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\begin{document}

\title{Why Animals Construct Helical Burrows: Construction vs.
Post-Construction Benefits}



\author[1]{Sean Doody}%
\author[2]{Stephen Hasiotis}%
\author[1]{Shivam Shukla}%
\affil[1]{University of South Florida}%
\affil[2]{University of Kansas College of Liberal Arts and Sciences}%


\vspace{-1em}



  
  \date{June 18, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
The extended phenotype of helical burrowing behavior in animals has
evolved independently many times since first appearing after the
Cambrian explosion (\textasciitilde{}540 million years ago). A number of
hypotheses have been proposed to explain the evolution of helical
burrowing in certain taxa, but no study has searched for a general
explanation encompassing all taxa. We reviewed helical burrowing in both
extant and extinct animals and from the trace fossil record and compiled
from the literature 10 possible hypotheses for why animals construct
helical burrows, including our own ideas. Of these, six were
post-construction hypotheses----benefits to the creator or offspring,
realized after burrow construction----and four were construction
hypotheses reflecting direct benefits to the creator during
construction. We examined the fit of these hypotheses to a total of 21
extant taxa and ichnotaxa representing 59--184 spp. Only two
hypotheses----antipredator, biomechanical advantage----could not be
rejected for any species (possible in 100\% of spp.), but six of the
hypotheses could not be rejected for most species (possible in 86--100
\% of spp.): microclimate buffer, reduced falling sediment (soil),
anticrowding, vertical patch, and the above two hypotheses. Four of
these six were construction hypotheses, raising the possibility that
helical burrowing might have evolved without providing post-construction
benefits. Our analysis showed that increased drainage, deposit feeding,
microbial farming, and offspring escape could not explain helical
burrowing behavior in the majority of taxa (5--48\%). Overall, the
evidence does not support a general explanation for the evolution of
helical burrowing in animals. The function and evolution of the helix as
an extended phenotype would seem, at least in some cases, to provide
different advantages for different taxa. Although direct tests of many
of the hypotheses would be difficult, we nevertheless offer ways to test
some of the hypotheses for selected taxa.%
\end{abstract}%



\sloppy


Why Animals Construct Helical Burrows:

Construction vs. Post-Construction Benefits

J. Sean Doody\textsuperscript{a*}, Shivam Shukla\textsuperscript{a} and
Stephen T. Hasiotis\textsuperscript{b}

\textsuperscript{a}Dept. of Integrative Biology, University of South
Florida, St. Petersburg Campus, 140 7\textsuperscript{th} Ave. South,
St. Petersburg, Florida 33701 USA

\textsuperscript{b}Dept. of Geology, University of Kansas, 1475 Jayhawk
Blvd, Lindley Hall, rm 215, Lawrence, Kansas 66045 USA

*Corresponding author: jsdoody@usf.edu

Abstract

The extended phenotype of helical burrowing behavior in animals has
evolved independently many times since first appearing after the
Cambrian explosion (\textasciitilde{}540 million years ago). A number of
hypotheses have been proposed to explain the evolution of helical
burrowing in certain taxa, but no study has searched for a general
explanation encompassing all taxa. We reviewed helical burrowing in both
extant and extinct animals and from the trace fossil record and compiled
from the literature 10 possible hypotheses for why animals construct
helical burrows, including our own ideas. Of these, six were
post-construction hypotheses----benefits to the creator or offspring,
realized after burrow construction----and four were construction
hypotheses reflecting direct benefits to the creator during
construction. We examined the fit of these hypotheses to a total of 21
extant taxa and ichnotaxa representing 59--184 \emph{spp} . Only two
hypotheses----antipredator, biomechanical advantage----could not be
rejected for any species (possible in 100\% of \emph{spp.} ), but six of
the hypotheses could not be rejected for most species (possible in
86--100 \% of \emph{spp.} ): microclimate buffer, reduced falling
sediment (soil), anticrowding, vertical patch, and the above two
hypotheses. Four of these six were construction hypotheses, raising the
possibility that helical burrowing might have evolved without providing
post-construction benefits. Our analysis showed that increased drainage,
deposit feeding, microbial farming, and offspring escape could not
explain helical burrowing behavior in the majority of taxa (5--48\%).
Overall, the evidence does not support a general explanation for the
evolution of helical burrowing in animals. The function and evolution of
the helix as an extended phenotype would seem, at least in some cases,
to provide different advantages for different taxa. Although direct
tests of many of the hypotheses would be difficult, we nevertheless
offer ways to test some of the hypotheses for selected taxa.

Key words: behavior; extended phenotype; costs-benefit; spiral burrow;
helix; ichnotaxa

\textbf{Introduction}

An extended phenotype, when referring to a single species, includes some
architecture or entity (e.g., beaver dam, termite mound) in which the
phenotype is the fitness of the construction for survival and
reproduction (Dawkins, 1982, 2004). Scientific interest in extended
phenotypes has been widespread and sustained, encompassing diverse areas
ranging from parasite manipulation of hosts (Hughes and Libersat, 2019)
to relationships between genomes and phenotypes (Hunter, 2018) to human
sexual selection theory (Luoto, 2019).

Burrow architectures are classic extended phenotypes that show great
diversity and complexity and can reflect important fitness-related
traits (Hansell, 2005). In a classic example, the old-field
mouse,\emph{Peromyscus polionotus} , constructs complex burrows with a
long entrance tunnel that leads into a nest cavity and a secondary
escape tunnel, while its sister species, the deer mouse (\emph{P.
maniculatus} ) builds shorter, single-tunnel burrows (Weber et al.,
2013). The complex burrowing behavior of \emph{P. polionotus} is
derived, has a strong genetic component, and its putative adaptive
function is to facilitate escape in an open, exposed habitat (Wolfe and
Esher, 1977; Weber and Hoekstra, 2009; Weber et al., 2013).

A diversity of terrestrial and aquatic animals excavates mysterious
helical burrows that comprise multiple, symmetrical spirals descending
into a medium (i.e., substrate, sediment). The first of these kinds of
burrows appeared with the Cambrian explosion \textasciitilde{}540
million years ago (e.g., Goldring and Jensen, 1996; Hasiotis, 2012;
Sappenfield et al., 2012; Zhang et al., 2015) and many others are known
only from fossils, including the remarkable 3-meter-deep burrows
assigned to the ichnotaxon \emph{Daimonelix} that were constructed by
the terrestrial beaver \emph{Palaeocaster} from the Miocene (Barbour,
1892; Martin and Bennett, 1977). Various forms of \emph{Daimonelix} are
now known to have been constructed by a variety of terrestrial
vertebrates since the Late Permian, approximately 260 million years ago
(Smith, 1987; Fischer and Hasiotis, 2018; Raisanen and Hasiotis, 2018).
Living examples of species that construct helical burrows include
terrestrial taxa, such as some pocket gophers, monitor lizards, and
scorpions, and marine forms such as some shrimp and some polychaetes
(e.g., Powell, 1977; Koch, 1978; L\selectlanguage{ngerman}öwemark and Schäfer, 2003; Hasiotis
and Bourke 2006; Netto et al., 2007; Wilkins and Roberts, 2007; Doody et
al., 2015).

The relentless, independent evolution of helical burrowing behavior
across disparate unrelated taxa dating back hundreds of millions of
years attests to its apparent utility. Yet, the reason(s) for the
evolution of the helix from more simple burrows remains largely
speculative and unresolved. One problem is that little is known of the
natural history of the tracemakers of the fossil burrows or trace
fossils (e.g., Bromley, 1996; Hasiotis 2007). Another problem is no
study has considered all taxa in the search for a general explanation,
although a diversity of functions is certainly possible and is sometimes
suggested. To illustrate, collectively, helical burrows have been
proposed to have evolved to buffer microclimate of the burrow from
harsher outside conditions (e.g., temperature, aridity, salinity),
promote drainage during flooding, thwart predators, reduce burrow
interference with conspecifics, increase surface area to expose more
sediment for deposit-feeding, or promote bacterial farming (e.g., Martin
and Bennett, 1977; Koch, 1978; Dworschak \& Rodriguez, 1997; Myer, 1999;
Netto et al., 2007; de Gibert et al., 2012; Doody et al., 2015; Raisanen
and Hasiotis, 2018; Muñiz and Belaústegui, 2019). Moreover, some have
hypothesized that helical burrows could serve multiple functions
(behavioral category polychresichnia; Hasiotis, 2003) (Koch, 1978; Netto
et al., 2007; Carvalho and Baucon, 2010; deGibert et al., 2012; Raisanen
and Hasiotis, 2018).

These hypotheses offered to explain helical burrowing behavior generally
invoke adaptation in the form of `post-construction' benefits to the
creator. Indeed, an adaptive function(s) of helical burrows seems
plausible, given its multiple origins and the increased effort required
to create a helix compared to a simpler (straight) burrow of the same
incline (volumetric calculations by Meyer, 1999). Much less attention
has been given to `construction' costs-benefits of helical burrows, or
those that provide no benefit to the occupant after burrow construction,
but rather are restricted to cost-benefits of burrowing behavior itself.
In an exception, White (2001) estimated the total cost of helical burrow
construction in scorpions by calculating the net cost of soil transport
and the costs of the animal moving itself and soil horizontally, and
vertically against gravity. Helical burrowing scorpions minimized both
(i) the energy used during burrow excavation by descending as steeply as
possible, and (ii) the energy required for burrow maintenance, by
constructing an entrance run that is shallower than the angle of repose
(rest) of dune sand (White, 2001).

Recently, two species of monitor lizards were found to excavate deep,
helical burrows for the sole purpose of nesting and the authors
discussed the fit of some post-construction (adaptive) hypotheses for
the function of the helix in these lizards (Doody et al., 2014, 2015,
2018a, b, 2021). The communal nests of the yellow-spotted monitor
(\emph{Varanus panoptes} ) and Gould's monitor (\emph{V. gouldii} ) are
by far the deepest extant vertebrate ground nests known (averaging 2--3
m deep and reaching 4 m deep). The burrows are soil-filled, and consist
of an incline to a depth \textgreater{} 1m, followed by 2--7 tight
descending spirals that terminate in a slightly enlarged nest chamber
(Fig.1a,b). Mothers excavate the burrows, lay their eggs, and then
abandon the burrows. Unlike scorpions, the lizards do not transport the
soil out from the burrows----they remain soil-filled and the lizards
`swim' through the excavated soil after laying eggs. Thus, White's
(2001) calculations and conclusions for scorpions and potentially other
animals do not apply to the lizards. Although a few of the
post-construction hypotheses might apply to the lizard burrows (e.g.,
the helix potentially reducing egg predation), `construction' benefits
may provide a more parsimonious explanation than `post-construction'
benefits; e.g., the helix preventing soil from falling back into the
burrow as it's removed; falling soil might make burrow creation
impossible or extremely difficult in a steep and straight inclined
burrow.

Herein we generate and review the major `construction' and
`post-construction' hypotheses for why animals evolve the extended
phenotype of helical burrows. We address 10 hypotheses including those
extracted from the literature and our own. We ask if any of the
hypotheses could be general for all taxa. If not, we ask the opposite
question: Why did helical burrowing evolve for different reasons in
different taxa? To address these two overarching questions, we examined
the fit of each hypothesis to each of 21 taxa representing 77--188 spp.,
based on natural history, behavior, and deductive reasoning, from
published sources. We outline potential future tests of hypotheses for
selected taxa.

\textbf{Materials and Methods}

We surveyed the scientific literature for evidence of helical burrows in
invertebrates and vertebrates using two-way searches on Google Scholar
and Google (general web search). We excluded species for which there was
only one (or less) spiral turn (e.g., Linsenmair, 1967; Basan and Frey,
1977; Hembree, 2009; Carvalho and Baucon, 2010; Kinlaw and Grasmueck,
2012; Hembree, 2014; Mikus and Uchman, 2013; Vazirianzadeh et al., 2017;
Paul et al., 2019). We also excluded studies describing burrows that
were weakly helical, weakly sinusoidal or `loosely spiraling' (e.g.,
Finlayson 1935 in Johnson, 1989; Koch, 1978; Coelho et al., 2000; Kinlaw
and Grasmueck, 2012). Although there is likely a continuum of sinuosity,
we found a somewhat dichotomous grouping of burrows that were slightly
curved vs. repeatedly or regularly spiral or helical. We thus only
included species with burrows described as `tortuous' or `possessing
regularly descending spiral coils,' or a `helix' (e.g., Powell, 1977;
Koch, 1978). Although the behavior of constructing weakly helical
burrows could be important in understanding the evolution of helical
burrowing behavior (indeed \emph{Urodacus} scorpions do both), the
number of taxa exhibiting weakly spiral burrowing are too numerous to
consider here. Moreover, the degree of burrow sinuosity has not been
quantified for most taxa, making interspecific comparisons difficult. We
included papers on both extant and extinct helical burrows produced by
animals, although the producers of helical burrows----trace fossils
reported as ichnotaxa or described in open nomenclature----in the fossil
record are often unknown. For trace fossils, several tracemakers from
different species as well as different phyla can produce a similar type
of trace fossil morphology (ichnotaxon), for example
\emph{Daimonelix}(Raisanen and Hasiotis, 2018). Thus, our data rows in
Table 1 often reflected more than one species. We also do not consider
burrows that occurred in one horizontal plane, including sinusoidal
traces (e.g.,\emph{Sinusichnus} ; Belaústegui et al., 2014; Soares et
al., 2020) and the spiral feeding traces that occur in soft sediment in
one surface plane (e.g., the polychaete \emph{Paraonis fulgens} ; Risk
and Tunnicliffe, 1978).

We compiled hypotheses offered for the function of the helix, against
which we could assign the likelihood that the hypothesis fit a
particular taxon or ichnotaxon. For this we used `possible', `not
likely' or `n/a' (not applicable); `n/a' indicated that there was
virtually no chance of a fit, based on deductive reasoning. For example,
the hatchling escape hypothesis developed for lizards, which proposes
that the helix loosens the soil to facilitate hatchlings escaping the
burrow through meters of resistant soil, would not be applicable to
aquatic species with open burrows. We subjectively assigned `not likely'
if a good fit was unlikely, and we explained our reasoning in the text.
Unlike with `n/a', `not likely' could change with the addition of new
information or if our reasoning or that of others, was less informed.
The assignment of `possible' indicated a good fit or potential fit,
based on the available evidence, context, and our reasoning or that of
other authors. In many cases, however, designation of `possible'
reflects that difficulty in testing hypotheses----for example, directly
testing the antipredator hypothesis for most extinct species is not
possible. Thus, we could not conclusively claim that a hypothesis was
general even if it scored `100\% possible' for all taxa. However, by
eliminating some taxa for each hypothesis (by assigning `n/a or `not
likely') we could potentially conclude that some or all of the
hypotheses \emph{could} be general for all taxa.

\textbf{Results}

Table 1 shows the results of the fit of hypotheses for the function of
helical burrows to 21 taxa representing 59--184 species. The wide range
in the potential number of species reflects both our lack of knowledge
of the burrow types in extant and extinct conspecifics and the
uncertainty of the species richness of ichnotaxa.

Of the 10 hypotheses, six are post-construction hypotheses and four are
construction hypotheses. Of the 21 taxa, 12 (57\%) are extant, eight
(38\%) are ichnotaxa and one includes both (5\%; Table 1).

Two of the hypotheses, antipredator and biomechanical advantage, were
designated as `possible' for all taxa (score of 100\%; Table 1). Other
high-scoring hypotheses were the anticrowding (95\%), vertical patch
(95\%), falling sediment (soil) (95\%), and microclimate buffer
hypotheses (86\%). Two hypotheses, deposit feeding and increase
drainage, received moderate scores (both 48\%), mainly due to the fit of
each to only terrestrial or only aquatic animals (Table 1). The
remaining two hypotheses, microbial farming and offspring escape,
received low scores (24\% and 5\%, respectively).

Although the hypothesis sample sizes precluded statistical comparison,
the mean score for construction hypotheses (91.5 ± 2.99\% SE; N=4) was
higher than the mean score for post-construction hypotheses (49.3 ±
14.06\% SE; N=6).

\textbf{Discussion}

Our review revealed that six of the 10 hypotheses for why animal
construct helical burrows could not be confidently rejected for most of
the taxa (86--100\% possible; Table 1). These hypotheses range from
`indirectly testable' (falling sediment, vertical patch, biomechanical)
to `extremely difficult or impossible to test' (antipredator,
anticrowding). Interestingly, four of those six hypotheses are
`construction' hypotheses, raising the possibility that helical
burrowing could save on energy costs associated with constructing a
helix without implicating post-construction adaptive benefits. Our
analysis also eliminated some hypotheses as general explanations for the
behavior; hypotheses involving increased drainage, deposit feeding,
microbial farming, and hatchling escape could not explain helical
burrowing behavior in the majority of the animals (5--48\%, Table 1).
The function and evolution of the helix as an extended phenotype remain
unknown but would seem, in some cases, to provide different advantages
for different taxa. In the following sections we discuss the fit of each
hypothesis to selected taxa.

\emph{4.1. Post-construction hypotheses}

\emph{4.1.1. Antipredator hypothesis}

Perhaps the most obvious reason to construct a more complex, helical
burrow is to reduce the threat of predation of the inhabitant(s)
(Martin, 1994; Doody et al., 2015). Accordingly, we could not rule out
this explanation for helical burrows of any species (Table 1). Any
burrow refuge could decrease predation, but a spiral could slow or
confuse a predator in pursuit of the inhabitant as it attempts to escape
down the burrow. The helical burrow could also, depending on size and
mobility of the predator, prohibit the predator from reaching the
inhabitant, its eggs, or offspring. For example, the helical burrows of
the pocket gopher \emph{Geomys pinetis} may slow down or confuse
predators such as weasels or snakes (Brown and Hickman, 1973). Myer
(1999), however, noted that while predators that could fit
into\emph{Palaeocastor} burrows may have been too long and/or not
flexible enough to follow the beavers down into the tight helix, snakes
and weasels could easily access helical burrows, and such predator
fossils as \emph{Zodiolestes daimonelixensis} (a prehistoric weasel)
have been found in \emph{Palaeocaster} burrows (Martin, 1989; 1994).
Elsewhere, helical burrows have been speculated to help thwart monitor
lizard and fish predators of scorpions (\emph{Urodacus} ) and shrimp
(\emph{Axianassa} ), repsectively (Koch, 1978; Felder, 2001). According
to Adams et al. (2016), the cost of predator excavation may increase
disproportionately the deeper and more tortuous the burrow, as sand
caves in and the tunnel becomes increasingly harder to follow.

In the case of monitor lizards (\emph{Varanus panoptes} and \emph{V.
gouldii} ) that construct helical burrows solely to lay eggs, the helix
could thwart egg predators. In support of predator exclusion geometry,
monitor helical burrows are very tight and regular. No egg predators
have been identified for these lizards, but the most likely predator
would be conspecific males (Doody et al., 2015). The monitor eggs at the
burrow terminus would be difficult to detect and reach by any predator
because the burrows are 2--4 m deep and soil-filled (Doody et al., 2015;
2018a, b; 2020), but perhaps the addition of a helix would further
frustrate a predatory monitor lizard. Alternatively, Doody et al. (2015)
speculated that perhaps the helix in monitor lizards evolved as a
deterrent to a now-extinct predator, such as \emph{Thylacinus}
or\emph{Megalania} (Clode, 2009).

There is no real evidence for an antipredator function of helical
burrows, but testing this hypothesis would be difficult for most
species, especially \emph{in situ} , and not possible for ichnotaxa with
no modern homologs. In the monitor lizards, field experiments comparing
nest predation rates between natural nests and artificial nests without
a helix could be a useful indirect test, as could creating baited,
artificial helical burrows to see if (marauding) male monitor lizards
could navigate the burrows.

\emph{4.1.2. Microclimate buffer hypothesis}

An often-cited potential function of helical burrows is to buffer the
burrow microclimate from the outside environment; microclimate factors
discussed include temperature, humidity, and salinity. Indeed, in our
review, the hypothesis could not be rejected for most taxa (86\%, Table
1). Koch (1978) showed that scorpion (\emph{Urodacus} ) species in more
open areas in more arid parts of Australia construct deeper burrows with
more spirals than those that construct burrows under cover objects in
more mesic areas, concluding ``It is clear that deep spiral burrow
construction has evolved as an adaptation for the avoidance of harsh
surface conditions, and has enabled species of the genus
\emph{Urodacus}to spread to otherwise inhospitable arid environments.''
While animals constructing deeper burrows in more arid environments to
buffer against extreme temperatures and low humidity is logical----Koch
successfully leverages the literature on arthropods in this
argument----this apparent relationship does not necessarily have a
direct bearing on the presence of, or number of spirals in, a helix,
which may simply be a correlate of depth, without implicating
microclimate buffering.

The ichnogenus \emph{Daimonelix} has been interpreted as multi-purpose
burrows (i.e., polychresichnia; Hasiotis, 2003) in which the helix
functions to buffer inhabitants from surface extremes. Noting the
seasonally hot and dry paleoclimate inhabited by \emph{Palaeocaster} ,
the Miocene terrestrial beaver tracemaker of some \emph{Daimonelix} ,
Martin and Bennett (1977) proposed that the helix would contribute to
keeping burrow humidity high. Myer (1999), after calculating the
comparative volumes and surface areas of helical vs. straight burrows,
concluded that the \emph{Daimonelix} helical design would have resulted
in a more consistent temperature and humidity when extreme variations
were experienced at the surface. In support, Smith (1987, 1993, see also
Smith et al., 2021) hypothesized that the helical burrows
of\emph{Diictodon} , a mammal-like therapsid from the Permian of South
Africa and another \emph{Daimonelix} tracemaker, offered climate control
(cool, moist conditions) during extremely hot and dry atmospheric
conditions; limited air flow of the helix would allow the humidity of
the terminal chamber to rise, especially if near the water
table.\emph{Daimonelix} burrows in Triassic (therapsids) and Jurassic
(mammals) continental deposits also occur in floodplain and alluvial
plain settings formed under megamonsoonal and tropical wet-dry climates,
respectively (Fischer and Hasiotis, 2018; Raisanen and Hasiotis, 2018).
Thus, the hypotheses of microclimate mediation and predator avoidance
would apply to these Mesozoic burrows as well.

According to Adams et al. (2016), Koch's (1978) assertion that scorpion
burrows are more helical and deeper in more arid areas is supported by
exposure to more wind and eddies in a turbulent boundary layer on plains
and sand dunes (Stull, 1988; Turner and Pinshaw, 2015) and higher rates
of water loss in burrowing scorpions than in non-burrowing species
(Gefen and Ar, 2004). Scorpions typically have very low rates of
evaporative water loss through their cuticle, however (Hadley 1970,
1990; Toolson and Hadley~1977). Thus, helical burrows as an adaptation
to sustain high relative humidity, thereby reducing the evaporative
water loss of scorpion inhabitants, is plausible.

Interestingly, deep and shallow helical scorpion burrows were found to
occur together in the same area in central Australia (Hasiotis and
Bourke, 2006; Hembree and Hasiotis, 2006). This association indicates
that there may be other factors at work, such as: (1) the occurrence of
different species with slightly different burrow morphologies; or (2)
ontogenetic variation in burrow size, with older and larger scorpions
having larger diameter, deeper, and more levels of helices in the
burrow. Also, perhaps, the orientation of the dune slope on which the
burrow is constructed may play a role in the burrow depth, with deeper
burrows on north-facing slopes because of the greater amount of solar
insolation.

Some monitor lizards (\emph{Varanus} ) construct helical burrows solely
for nesting; the 2--4 m deep burrows are unique among helical burrows in
that they are soil-filled (Doody et al., 2014, 2015, 2018a, b, 2021).
This places some doubt on microclimate buffering as an explanation for
helical burrowing in the lizards (Doody et al., 2015). If climate
control is the chief function of the helix, why add soil to the helix,
or why not construct a soil-filled straight burrow? The answer is not
clear. Since the soil-filled monitor burrows are not inhabited by the
lizards themselves, the removal of soil would not be considered when
calculating the relative costs of straight vs. helical burrows. Most
other nesting monitor lizards construct shallower (\textless{}0.5 m
deep) burrows in which they remove and then back-fill the soil (Pianka
and King, 2004); thus, the habit of leaving the soil in the burrow
exhibited by the deep-helical-nesting monitor lizards would likely be a
derived behavior. Although the deep-nesting, helical burrowing monitor
lizards do remove soil from the first \textasciitilde{}0.5 m of the
burrow length, the remaining soil is not removed. Although it is
possible that monitor lizards evolved helical burrow construction in
response to dry conditions, and then subsequently evolved leaving the
soil in the burrow to further insulate it or to thwart predators, this
sequence of evolutionary events is less parsimonious.

The aquatic helical burrows of the ichnogenus
\emph{Gyrolithes,}constructed from the Permian to the present-day, have
been interpreted as a refuge from extreme salinity fluctuations in
transitional environments between the continental and marine realms
(Beynon and Pemberton, 1992; Buatois et al., 2005; Netto et al., 2007;
Hasiotis et al., 2013). Theoretically, the effect of salinity
fluctuations would be diminished because fine sediment of infaunal
habitats slows down the exchange of pore water (Rhoads, 1975; Saunders
et al., 1965). This hypothesis was based on the idea that
\emph{Gyrolithes} was restricted to shallow marine environments
(Gernant, 1972). However, some (e.g., all Cambrian) \emph{Gyrolithes}
are found in open-marine environments, which is suggestive of normal
salinity conditions, shedding considerable doubt on salinity buffering
as the primary function of the helix (Netto et al., 2007; de Gibert et
al., 2012; Laing et al., 2018). Moosavizadeh and Knaust (2021) similarly
questioned the modulation of salinity as the principal function of
\emph{Gyrolithes} due to their apparent high-salinity paleoenvironments.
Similarly, \emph{Lapispira} has been found in fully marine deposits
(Lanes et al., 2008), shedding doubt on the salinity buffering
hypothesis for that ichnotaxon (de Gibert et al., 2012).

There are several important caveats to consider when interpreting
behavior and purpose of burrow construction. One of the basic principals
in ichnology is that any one particular burrow architecture---in this
case, helical burrow \emph{Gyrolithes} ---can be used under different
conditions for different purposes (e.g., Ekdale et al., 1984; Bromley,
1996). Some \emph{Gyrolithes} occur in the transitional zone where
salinities vary between marine, brackish, and fresh water, whereas
others occur in normal marine settings. There are also helical burrows
assigned to \emph{Gyrolithes} that reflect parts of larger burrow
systems, such as \emph{Ophiomorpha} and \emph{Thalassinoides} (Mayoral
and Muñiz, 1995, 1998; Dworschak and Rordrigues, 1997). The occurrence
of \emph{Gyrolithes} has been attributed to brackish water conditions
but not necessarily extreme in fluctuations, but more like mesohaline or
polyhaline salinities. For example, Jackson et al. (2016) and
Oligmueller and Hasiotis (2022) described \emph{Gyrolithes} from Lower
Permian river-dominated delta deposits in Antarctica and Upper
Cretaceous intertidal deposits in Colorado (USA), respectively. Both of
these occurrences are in the transitional zone where salinity
fluctuations were a daily phenomenon. Perhaps the helical burrow was a
way for the constructor to limit the amount of water in the burrow
exchanged with the flow and mixing of freshwater with marine water or
the changing tides. Also, the helical structure of
\emph{Gyrolithes}might have been an advantage to the constructor so as
not to be hydrodynamically removed from the burrow by changing water
currents, or as predator avoidance as the tracemaker withdraws itself
into the burrow.

Evidence for the microclimate buffering hypothesis is indirect at best
for most taxa. In particular, the unique soil-filled burrows of the
monitor lizards raises doubts. Addressing this hypothesis requires
understanding which extended phenotype evolved first----the helix or the
soil-filled aspect of the burrow. The two known helical-burrowing
monitor lizards are sister taxa, and most other species construct
simple, inclined soil-filled nesting burrows (Pianka and King, 2008).
The ancestral burrow morphology for the helical nesters is thus
soil-filled (back-filling or leaving the soil in place). The helical
burrows are also extremely deep (Doody et al., 2014, 2015, 2018a, b,
2021)----another derived trait. The most parsimonious evolutionary
sequence of burrow construction for the deep-nesting monitor lizards is
thus, soil-filled first, deep next, and then the helix. Why construct a
helix when the deep, plugged burrow would already provide buffering
between the burrow and the outside environment? The hypothesis appears
to be a poor fit to the monitor lizards.

\emph{Increased drainage hypothesis}

A third hypothesis for helical burrows in terrestrial taxa proposes that
the helix provides improved drainage in flood conditions via increased
surface area, thereby preventing or reducing burrow flooding that could,
for example, cause mortality or expulsion of scorpions or failure of
lizard eggs (Koch, 1978; Doody et al., 2015). This explanation was
rejected for a majority of taxa (possible in 48\% of taxa, Table 1).
Koch (1978) proposed that the extensive spiraling of
\emph{Urodacus}scorpion burrows would reduce the effect of sheet
flooding during the wet season. This idea may be supported by seasonal
flash flooding apparently experienced by \emph{Diictodon} (the
constructor of\emph{Daimonelix;} King, 1996), although this hypothesis
was not explicitly discussed (Smith, 1987; Smith et al., 2021). Indeed,
somewhat ironically, the taphonomy of helical burrows relies on flooding
in alluvial environments (e.g., Smith et al., 2021).

Although the helix itself may not beneficial for drainage after
flooding, the upturned terminal chambers on many of the Miocene and some
of the Jurassic \emph{Daimonelix} burrows (Martin and Bennett, 1977;
Raisanen and Hasiotis, 2018) have been thought to trap air in the burrow
chamber so that during flooding, the burrower would not drown in its
burrow (Hasiotis et al., 2004).

Nesting in both \emph{V. panoptes} and \emph{V. gouldii} in northern
Australia is during the late wet season and early dry season, and there
can be substantial rainfall including `sheet' flooding during the first
two months of incubation for the earlier nests (Australia Bureau of
Meteorology). Although the lizard burrows are soil-filled, the soil is
somewhat loose early in incubation. The loose soil combined with the
increased surface area of the helix could improve drainage above the
nest thereby preventing egg inundation, or reducing the amount of time
eggs are inundated. Lizard eggs can withstand inundation for up to six
hours based on previous experiments (Heger and Fox, 1992; Losos et al.,
2003).

\emph{Deposit-feeding hypothesis}

Some marine forms such as \emph{Gyrolithes} (e.g., Dworschak and
Rodriquez, 1997; Pervesler and Hohennegger, 2006; Carvalho and Baucon,
2010) may construct helical burrows for deposit feeding in shallow to
deep-water marine settings. Specifically, the increased surface area of
the helix compared to a straight burrow would enhance deposit feeding by
optimizing the utilization of nutrients in a given sediment volume in
animals, such as shrimp, polychaetes, and other vermiform animals. For
example, the helices found in the burrows of the thalassinidian
shrimp\emph{Axianassa australis} may allow the animals to burrow to
greater depths with gentle slopes in order to exploit deeper sediment
layers rich in organic matter (Dworschak and Rodriguez, 1997; see also
Atkinson and Nash, 1990; Nickell and Atkinson, 1995 for similar
conclusions for the shrimp \emph{Callianassa subterranea} ). Although
deposit feeding in\emph{A. australis} burrows needs confirmation, the
poor fit of the diameter of the shrimp to the burrow diameter suggests
deposit feeding, because suspension feeders tend to fit closely into
their burrows (Dworschak and Pervesler, 1997; see also Pervesler and
Dworschak, 1985); a close fit is necessary for effective ventilation of
the burrow for respiration and feeding in suspension feeders (Dworschak,
1981, 1987). Wetzel et al. (2010) considered deposit feeding as likely
in\emph{Gyrolithes} , partly based on the finding of an abundance of
plant material in the vicinity of the burrows (Dworschak and Rodriguez,
1997). Laing et al. (2018), however, considered deposit feeding unlikely
in\emph{Gyrolithes} , whether made by polychaetes or decapod
crustaceans, based on the lack of evidence of active infill or fecal
pellets. However, the presence or absence of backfill menisci and/or
fecal pellets are not necessary to determine if a burrow is used for
deposit-feeding. There are many callianassid and thalassinid shrimp that
produce fecal pellets while in their burrows and either used them to
construct burrow walls or expel them from the burrow by recirculating
the water (e.g., Kennedy et al., 1969; Curran and Seike, 2016; Netto et
al., 2017).

Helical burrows in terrestrial animals are likely not involved in
feeding, based on the lack of food resources deep in the ground (with
the exception of roots and tubers, which are shallow and close to the
surface), and based on the lack of frequent branching and fecal fillings
(Toots, 1963). The common mole rat does construct complex, shallow
burrows to feed on roots and tubers, but apparently does not construct
helical burrows (e.g., Spinks et al., 2000). Analogous burrow
morphologies to these modern burrowers have been found in Lower Jurassic
continental erg deposits of the Navajo Sandstone in Utah (Riese et al.,
2011).

\emph{4.1.5. Microbial farming hypothesis}

In a variation of the deposit feeding hypothesis, marine burrowers have
been hypothesized to create a helix to optimize feeding by increasing
the sediment-to-burrow ratio; this is referred to as microbial farming
or gardening (Felder, 2001; Moosavizadeh \& Knaust, 2001; Netto et al.,
2007). Netto et al (2007) argued that Permian \emph{Gyrolithes} were
created by crustaceans (rather than by polychaetes, as proposed by
Powell, 1977; see also Gingras et al., 2008), possibly implicating
microbial feeding since the Paleozoic. Moosavizadeh \& Knaust (2021)
considered microbial farming as the most likely function
of\emph{Gyrolithes} from Iran, which occurred in soft, low-energy
sediments. Microbial farming has also been hypothesized as a potential
function of helical burrows of trace fossil \emph{Helicodromites} in
oligotrophic conditions in a well-oxygenated environment (Poschmann,
2015). The possibility of microbial gardening in \emph{Gyrolithes} was
discussed by several authors (e.g., Seilacher, 2007; Wetzel et al.,
2010); however, the burrow morphology is not a good candidate for such a
behavior as it is also part of other burrow systems that are boxwork
structures (Mayoral and Muñiz, 1995, 1998; Dworschak and Rodriquez,
1997; Carvalho and Baucon, 2010). Furthermore, microbial farming is
indeed a trait of such marine trace fossils as \emph{Chondrites}
and\emph{Paleodictyon} , which have much more complex morphologies, like
downward and outward dendritic branching patterns and intricate
horizontal tubular patterns with vertical tubes (similar in pattern to a
chain-linked fence), respectively (Ekdale et al., 1984; Bromley, 1996).
Direct observations in extant marine helical-burrowing species \emph{in
situ} or in a laboratory setting are needed to provide indirect support
for this hypothesis.

\emph{4.1.6. Offspring escape hypothesis}

The sole (new) hypothesis involving postnatal parental care proposes
that the helix, by loosening the soil above the nest, facilitates
hatchling escape of neonate monitor lizards (this hypothesis is new and
may not apply to any other taxon). There is little doubt that the soil
is less resistant in the excavated helix compared to the surrounding
soil, which is often compact and firm. In fact, some helices were filled
with very loose soils and in some the core of the helix even collapsed,
leaving a cylinder-shaped section filled with loose soil (JSD, pers.
obs.). Hatchling emergence or escape burrows were found for both
deep-nesting species (Doody et al., 2018a, b). Hatchlings excavated
escape burrows nearly straight upwards from the nest 2--4 m to the
surface, rather than following their mother's soil-filled burrow. Such
deep nesting would challenge hatchlings to emerge considerable distances
through resistant soils. Although emergence burrows were not carefully
mapped, at least some of these burrows partly emanated through the helix
(JSD, pers. comm.); burrowing through the helix would involve traversing
\textasciitilde{}1--3 m of softer soil than the surrounding firm soils
(given that the helix begins at \textasciitilde{}1.2--1.5 m below the
surface). In short, the helix increases the probability of escaping by
reducing the effort required by hatchlings.

Perhaps in support of this hypothesis, the low clutch size (e.g., 3--8
eggs; Doody et al., 2020) of an animal nesting very deep might indeed
select for parental effort for careful nest excavation to facilitate
hatchling escape. While most ground-nesting reptiles deposit eggs
\textless{}30 cm below the surface, these lizards nest 2--4 m deep in
firm soils, seemingly requiring considerable energy for a small group of
hatchlings to excavate one emergence burrow. In only one of many nests
did we observe multiple emergence burrows emanating from the same
nest----there were two. The position of the helix directly above the
nest supports a useful function, but one could ask why the entire burrow
is not a helix (although perhaps loosening the soil for half the
emergence distance is enough to facilitate successful excavation and
escape). No other species can shed light on this hypothesis because none
are known to lay eggs or possess emergence burrows excavated by
hatchlings.

The recent finding of fossilized neonate \emph{Diictodon} skeletons with
adults in burrows assigned to \emph{Daimonelix} suggest that they could
have served as brood chambers; whether \emph{Diictodon} bore live young
or laid eggs is still under debate (Smith et al., 2021). Pocket Gopher
(\emph{Geomys} ) nests have also been found associated with helical
burrows (Brown and Hickman, 1973; Wilkins and Roberts, 2007). Although
the helix could be associated with brooding or eggs in some species
other than monitor lizards, the open \emph{Daimonelix} burrows
of\emph{Paleocaster} and \emph{Diictodon} do not support the idea of the
helix loosening the soil for neonates as posited by the hatchling escape
hypothesis.

Otherwise, there is little support for hatchling escape as a general
explanation for helical burrows. This hypothesis could be directly
tested by carefully excavating hatchling escape burrows to determine if
they typically emanate through the helical portion of the mother's
burrow. If they do, measuring the energetic costs of the hatchling
escape through resistant (no helix) soil vs. less-resistant soil (helix)
in the laboratory would be ideal. Measuring the energetic cost of the
mother's excavation of a helical nesting burrow would also provide
context for understanding any energetic benefit to hatchlings (see Rusli
et al., 2016 for a relevant example with sea turtle hatchlings).

\emph{4.2. Construction hypotheses}

\emph{4.2.1. Falling soil hypothesis}

Burrow structure can reflect the energetic cost of burrowing (Vleck,
1981; White, 2001). A new hypothesis, but partly based on previous
observations on helical burrowing in scorpions and evidence from
vertical burrows in pocket gophers, is that the spirals may allow the
animals to excavate a steep descent without much soil falling back into
the burrow during excavation; that is, the spirals would serve to hold
much of the newly excavated soil that would otherwise fall back into the
burrow terminus as its being removed, preventing or impeding further
excavation.

The first line of evidence supporting this hypothesis is found in the
relationship between climate-soil type-soil moisture and burrow
depth-number of spirals in scorpions. Scorpions occupying dry climates
with sandy dry soils construct deeper burrows with more spirals than
those in wetter climates. Polis (1990) hypothesized that by attenuating
the burrow angles the spirals would facilitate the vertical movements of
scorpions in burrows that are required to be deep enough to reach
optimal temperature and humidity. Adams et al. (2016) countered that
several species of scorpions construct simple vertical burrows without
spirals that descend 70--90° from the horizontal to 15--10 cm deep. This
comparison is confounded by soil type and moisture, however. Compared to
those in more mesic environments, scorpion burrows in more arid climates
are deeper and possess more spirals (references in Adams et al., 2010).
For example, burrows of the scorpion \emph{Urodacus yaschenkoi} in loose
sandy soil with little clay content were significantly shallower in
depth and angle, and with more spirals, compared to those in damp,
low-lying areas subject to flooding (Koch, 1977, 1978; Shorthouse and
Marple, 1980). Similarly, the deepest scorpion burrows with the most
spirals in South Africa were found in soils with high sand content and
low content of silt, clay, and organic matter, as well as low soil
moisture, compared to scorpion burrows in other areas (Abdel-Nabi et
al., 2004).

A second piece of related evidence comes from burrows of the pocket
gopher, \emph{Thonomys} \emph{bottae} , which excavates lateral tunnels
running parallel to the surface but must push excavated soil to the
surface to clear the burrows. According to Vleck (1981),
``\emph{Thonomys} in cohesive soils often dig nearly vertical laterals
and have little difficulty pushing lumps of excavated soil out or
plugging the lateral afterward (unpublished data). However, in
cohesionless sands like those in the study area, pocket gophers'
efficiency in pushing soil declines as slope increases. At steep angles
of ascent, much of a load of sand may fall back down the tunnel,
increasing the number of trips necessary to push a given amount out.
Laboratory observations indicate that \emph{T. bottae} may also have
difficulty in plugging the surface openings of vertical tunnels in
cohesionless soils. The slope of laterals is probably dictated by soil
characteristics and the differential efficiency of pushing soil with
changes in slope. Laterals that ascend at shallow angles may be the most
efficient solution in sandy soil.''

White (2001) demonstrated that the energetically cheapest method of
reaching an appropriate depth is to burrow the shortest possible
distance, which would be straight down (a vertical burrow). However,
they also noted that burrow structure may not be determined solely by
energetic concerns, and constructing a burrow from the surface at 90°
may not be possible. The burrow entrance constructed by the
scorpion\emph{U. yaschenkoi} is angled at about 25--30° (Koch 1978;
Shorthouse and Marples 1980), only marginally shallower than the angle
of repose of dune sand (32°: Robinson and Seely 1980). Thus, if burrows
were constructed at angles \textgreater{} 32°, sand would fall into, and
fill the burrow (White, 2001). Beyond the entrance run, the burrows
begin to spiral and descend steeply, as the soil becomes moister and
more cohesive with increasing depth. Burrows constructed by \emph{U.
yaschenkoi,} thus, minimize both the energy used during burrow
construction by descending as steeply as possible, and the energy
required for burrow maintenance by constructing an entrance run that is
shallower than the angle of repose of dune sand (White, 2001).

As with scorpions, helical burrows of deep-nesting monitor lizards also
exhibit a straight, gently sloping entrance run followed by a deeply
descending helix (Doody et al., 2015; 2018). The major difference is
that the lizard burrows are soil-filled----the soil is not removed
during construction. Thus, White's (2001) calculations of energy
expended moving soil out of the burrow would not apply to the lizard
burrows because the lizards do not remove the soil (except for the first
\textasciitilde{}0.5 m straight run). This focuses attention on the
digging action by asking: why not excavate straight down or straight at
a steep angle of incline? The answer may lie in the ability of the
spiral, combined with the lizard's body, in preventing loose, excavated
soil from falling back into the burrow terminus. Resisting the effects
of gravity by repeatedly removing falling soil would not only incur
extra costs, but could prohibit burrow construction.

Meyer (1999) used volumetric calculations to conclude that a helix would
cost 36--61\% more effort than a straight burrow. We do not challenge
the calculations or logic used by Meyer (1999); rather, we note that
those calculations did not consider the cost of repeatedly moving the
same soil that falls into the (shifting) burrow terminus during
construction. Thus, the need for constructing deep burrows----which
apparently evolved to provide moist conditions during the long dry
season incubation period in \emph{Varanus} lizards (see Doody et al.,
2015, 2018)----may have `prompted' helical construction to reduce the
energetic cost of repeatedly removing falling soil, or the falling soil
could have prohibited construction altogether. Another factor to
consider is the degree of firmness or cohesiveness of the soil in
which\emph{Daimonelix} was excavated. If the burrow walls contain
scratch marks (\emph{sensu} Zonneveld et al., 2022), then the sediment
was cohesive and much less likely to collapse in on itself. This would
limit the amount of effort in moving excavated material as long as the
matrix did not collapse in on it. Vertical burrows in stiff or firm,
cohesive sediment would also stay open; however, the biomechanics of the
organism would determine if a vertical burrow was a constructable and/or
livable situation (c.f., Hasiotis and Mitchell, 1993).

Could the falling soil hypothesis explain helical burrows in other
animals? The challenge of constructing a burrow vertically while
resisting the effects of gravity on both the body and loosened soil
could be general. Even in aquatic burrows the excavated soil must be
removed upwards against gravity, and a straight vertical shaft could
inhibit or prohibit this. Consider the amount of effort an organism
expends in maintaining its position in a vertical burrow excavated in
soil, 1--5 m deep, with appendages sprawled while excavating or
maintaining the burrow and removing the material to the surface. An
arthropod (e.g., arachnid, crustacean, or hexapod) with 6, 8, or 10
pairs of appendages could accomplish this feat (e.g., Hasiotis and
Mitchell, 1993; Hasiotis et al., 1993). Such burrow construction by a
tetrapod would be extremely difficulty for carrying material while
removing it from the bottom or maintaining its position in the burrow to
maintain the burrow walls (Hasiotis et al., 1999).

A gently inclined, long burrow might incur a lower energetic cost to
construct depending on the degree of inclination and distance between
the burrow entrance and terminus. Soil profiles have surface and
subsurface horizons from top to bottom with distinct composition and
firmness (e.g., Kraus, 1999; Brady and Weil, 2002). A gently inclined
burrow would increase the probability of spending more time within a
horizon with similar composition and firmness, whereas a vertical burrow
would have a higher probability of passing more quickly through multiple
horizons with different composition and firmness. If an inclined burrow
passes from a surface horizon that is relatively loose and contains
organics (i.e., A horizon) into a subsurface horizon (E, B, or C
horizon) that is more cohesive and firmer, than a higher energetic cost
might be incurred. The degree of energetic costs depends on the
development and thickness of each horizon, which reflects overall soil
formation.

The solution to conserve energy expenditure during construction would
seem to be a zigzag or switchback pattern which could eventually
`tighten' into a helix. However, some marine organisms construct(ed)
helical burrows in the horizontal direction (e.g., Dworschak and
Rodrigues, 1997; Minter et al., 2008); the falling soil hypothesis is
not a good fit as an explanation for helical burrows in these species.
Similarly, some helical sections in the burrows of the
shrimp\emph{Callianassa bouvier} may be excavated in the upwards
direction (Dworschak and Pervesler, 1988).

Some skinks construct a switchback style of burrow that mimics a spiral
(Hembree and Hasiotis, 2006). These switchbacks come from the main part
of the inclined burrow, which is flattened, elliptical in cross-section,
and resembles an upside-down U or reniform-shape (Hasiotis et al., 2004;
Hembree and Hasiotis, 2006). A possible function of this switchback
structure, which is not visible from the surface of the soil, is to
escape the burrow if a predator enters. Likewise, if the hidden
switchback burrow opening is discovered, a potential predator might not
be able to follow the tortuous path into the main part of the burrow.

Testing the falling soil hypothesis in monitor lizards could involve
observing nesting females in a captive situation to determine how well
mothers prevent soil from reaching the burrow terminus; alternatively,
recreating a helix in the laboratory with a model lizard could shed
insights into this ability, as would experiments with humans attempting
to construct a helical burrow.

\emph{4.2.2. Anticrowding hypothesis}

Many investigators have mentioned or addressed the possibility that
helical burrowing could reduce crowding and subsequent interference that
might otherwise occur if there were multiple burrows with straight runs
or ramps within a discreet area (Martin and Bennett, 1977; Koch, 1978;
Shorthouse and Marples, 1980; Myer, 1999; Gingras et al., 2008; Adams et
al., 2016; Doody et al., 2015). For example, Martin and Bennett (1977)
supposed that helical burrows in \emph{Paleocaster} could save
horizontal space and avoid neighboring burrows while maintaining a
shallow incline, great depth and close packing of burrows. For
scorpions, Koch (1978) mentions the avoidance of neighboring burrows
under crowded conditions as a possible function, and Shorthouse and
Marples (1980) hypothesized that helical burrows might decrease the risk
of antagonism or cannibalism by reducing the encounters probability
between scorpions from neighboring burrows. When discussing the function
of \emph{Gyrolithes} , Gingras et al. (2008) considered it likely that
the similar helical burrows of thalassinid shrimps were a response to
high population densities.

Myer (1999) used field data from \emph{Paleocaster}
-constructed\emph{Daimonelix} to calculate that burrow interference with
straight ramps or runs would lead to a low probability of a burrow
interfering with another (5--8\%). Adams et al. (2016) suggested that
this hypothesis leads to the prediction that burrows in dense
populations are more spiral than those in sparse populations; yet they
noted that hormurid scorpions that construct simple, vertical burrows,
occur in similar densities to~those constructing burrows with spirals
(Harington, 1978). Cambrian \emph{Gyrolithes} examined by Laing et al.
(2018) were relatively sparse, which may be due to them being part of
larger burrow systems of \emph{Thalassinoides} .

The anticrowing hypothesis is logical and supported by some evidence of
high densities of burrows, but is extremely difficult, if not
impossible, to directly test. An indirect test would be to characterize
burrow types at different densities, but this would assume that the
inclusion of spirals is a phenotypically plastic behavior, or that there
has been behavioral evolution among populations leading to disparate
burrow morphology.

\emph{4.2.3. Vertical patch hypothesis}

A third new hypothesis reflects potential heterogeneity in media
stiffness in the vertical vs. horizontal planes. Each soil horizon tends
to be more homogeneous in composition compared to overlying and
underlying in a particular area due to the abiotic and biotic processes
that form them (Kraus, 1999; Brady and Weil, 2002; Hasiotis, 2007).
Overall, there is greater heterogeneity vertically in a soil profile
than laterally, where the tendency is for the surface horizon (i.e., A
horizon) is looser with a greater amount of organic matter compared to
the subsurface horizon (e.g., B horizon), which is the zone of
accumulation of clays and other minerals that make it firmer and more
compact. Thus, deep burrowing in the form of a vertical burrow or
tightly helical burrow will incur a higher energetic cost to construct
the burrow. However, this cost is offset with the benefit of (1) greater
relative humidity and soil moisture (microclimate amelioration) combined
with (2) greater soil density (firmness and consistency) to ensure a
lower chance of soil collapse (i.e., escape of hatchlings) that also
doubles as better burrow construction in that sediment-filled burrows
result in predator avoidance.

In the case that shallower optimal or suitable sediment layers predict
similar layers directly below, it could benefit creators to construct
helical burrows once those shallower sediment conditions have been
discovered, rather than chance burrowing into suboptimal or unsuitable
conditions by excavating angular burrows. Relevant conditions could be
sediment or soil friability, hardness, or some biotic factor such
related to food or farming. In the case of deposit feeding or microbial
farming here could be post-construction benefits (see details for those
hypotheses). With the monitor lizards, most nesting areas are communal
and traditional, possibly due to the reduction in excavating costs
associated with constructing burrows in soil already loosed by
conspecifics (Doody et al., 2015; 2018).

\emph{4.2.4. Biomechanical advantage}

A fourth new hypothesis for helical burrows relates to biomechanical
advantage. As a burrower excavates, it may be better able,
leverage-wise, to remove or rework sediment (soil) with a lateral (side)
stroke that results in the burrow bending left or right. This could
result in a savings in energy or better efficiency in excavation that
could offset the increased effort required, mathematically, to excavate
a helical burrow rather than a straight burrow (as calculated by Meyer,
1999 for \emph{Palaeocaster} constructing \emph{Daimonelix} ; but see
previous section on falling soil hypothesis). This pattern would also
result in easier removal of excavated material from the burrow for many
tetrapods and arthropods. Also, helical burrowing in stiffer, more
cohesive media (sediment, soil) appears to be a tendency observed by one
of us (STH) in during burrow construction by spiders and crayfish (also
see Hasiotis and Bourke, 2006). Such a result might also be expected for
tetrapods that construct helical burrows in stiff or firm, cohesive
soils (also see Hembree and Hasiotis, 2006; Riese et al., 2011).

There is currently no evidence for this hypothesis in any taxon.
However, Monod et al. (2013) hypothesized that different burrow
architecture between taxonomic groups of scorpions was due to behaviors
related to morphology: fossorial hormurids are pedipalp burrowers that
use the large, often rounded pedipalpal chelae to loosen the soil and
carry it out of the burrow, whereas the closely related scorpionoid
families are cheliceral burrowers that use their enlarged chelicerae to
loosen the soil and then scrape it out of the burrow using the legs
and/or metasoma (see references in Monod et al., 2013). Barrass (1963)
found the direction of the spiral was related to the asymmetry of the
crab's claws such that the males with the major claw on the right exit
from the burrows spiralling counterclockwise, and vice-versa.

Testing the biomechanical hypothesis would minimally require observing
the digging strokes and understanding the biomechanics of burrow
excavation and preferably involve a comparison of energy required and
the efficiency of strokes that would create helical vs. straight
burrows. Toots (1963) provided an insightful treatment of the
fundamental biomechanical requirements of helical burrow construction by
considering the need for asymmetrical digging along the horizontal axis
and geotaxis and transverse gravity orientation (Toots, 1963). This
represents a good starting point for exploring the biomechanical
underpinnings of constructing a helical burrow, which may provide
insights into energetics and construction costs-benefits.

\emph{4.2.5. Additional hypotheses}

There were a few hypotheses mentioned in the literature that warranted
less attention based on their obvious lack of support or generality.
Koch (1978) proposed that extensive spiraling in scorpion burrows could
reduce the effects of wind-blown debris entering the burrow. This is
logical, but scorpions and other terrestrial animals often clear their
burrows of debris including blown sand, cave-in sand and vegetation
(Shorthouse and Marples, 1980). Spiral burrows produced by marine
organisms may help keep the burrow free of sediment debris. Another
hypothesis, raised for \emph{Gyrolithes} , suggests that the helical
burrow promotes anchoring of the tracemaker in the burrow in a
high-energy environment (Gingras et al., 2008; see also Laing et al.,
2018). However, the \emph{Gyrolithes} studied by Moosavizadeh and Knaust
(2021) reflected a low-energy environment. Finally, some male ghost
crabs (\emph{Ocypode} ) may construct spiral burrows for courtship
(Schober \& Christy, 1993; Clayton, 2005). However, only one species has
been shown to construct burrows with more than one spiral: at least some
of the burrows of \emph{Ocyopde ceratophthalmus} exhibit two spirals
(Parenzan, 1931, in: Eshky, 1985; Fellows, 1966, in: Vannini, 1980).
Some authors have included the hypothesis that helical burrows serve(d)
as domiciles (domichnia) that protect the burrows inhabitants (e.g.,
Laing et al., 2018). We did not consider this hypothesis because it
cannot in itself explain the evolution, benefits, or function of helical
structure above and beyond what the aforementioned hypotheses (e.g.,
antipredator) attempt to explain.

\emph{4.3. Potential evolutionary sequence of deep, helical burrowing
behavior in some monitor lizards}

We can reconstruct the putative evolution of nesting behavior in these
species using the discussions in previous sections. Large monitor
lizards that lay large eggs that require long incubation periods (6--9
months; Horn and Visser 1989; 1997) that must stretch over dry seasons
in species inhabiting arid areas, at least in Australia (Doody et al.,
2015; 2018). These species have evolved the behavior of nesting much
deeper than any other reptile (Doody et al., 2014; 2015; 2018). The
cheapest way, energetically, \emph{with regards to distance only} , for
a monitor lizard to nest 2, 3, or 4 m deep is to construct a vertical
tunnel straight below the site they have chosen (White, 2001, referring
to scorpions). However, a lizard cannot excavate a burrow straight down
because the soil continues to fall in on itself. For the lizard to
remove the soil from the burrow once they are deeper than 1 m is
effectively impossible because the soil would need to be thrown upwards
out of the burrow a considerable distance with efficiency. To our
knowledge, monitor lizards cannot carry or transport soil other than
kicking or dragging it on the surface with their limbs, head, and neck.
So, a deep, straight vertical burrow is physically impossible because
the creator could not get the loose soil out of the way to allow
continued burrow construction.

A physically manageable but more energetically expensive (distance-wise)
approach would be to excavate an inclined (straight) burrow run at an
angle that would prevent soil from falling back down once loosened. The
mean incline for \emph{V. panoptes} entrance burrows was 8° (Doody et
al., 2015). If the burrow is to be 3 m deep, with an angle of 8°,
solving for the opposite side of a right triangle yields a horizontal
distance of the nest from the burrow entrance of 19 m (13 m if 2 m deep,
26 m if 4 m deep). This is a considerable distance from where the mother
selected a suitable patch of soil, creating risk that she might
encounter more resistant soils that would be more costly to burrow
through. In support, both \emph{V. panoptes} and \emph{V. gouldii} nest
communally and traditionally, apparently taking advantage of soil
loosened by conspecifics by nesting in a discreet area of soil that is
softer than the surrounding area (Doody et al., 2015). Increasing the
angle of incline (steeper) would decrease the horizontal distance of the
nest from the burrow entrance, but at some point, the incline allows
soil to fall back into the burrow. As noted earlier, continually
removing soil that is falling back into the burrow is energetically
expensive and probably impossible at depths greater than one meter. This
cost could be large enough to offset or even outweigh the cost of
constructing a helix (calculated by Myer, 1999). Steeper inclines would
at some point be prohibitive (as with the vertical burrow above).

The possible solution was the construction of a helix, which is
physically manageable, and possibly energetically equivalent or superior
to a straight incline and would bring the creator straight down into the
intended nesting area with loosened soil. Perhaps there were
intermediates that resembled a zigzag or switchback pattern; these could
eventually `tighten' into a helix. Stopping the falling soil might be
especially needed useful for monitor lizards because they do not remove
the soil from the burrow, except for the first 0.5 m of the entrance
run.

\textbf{Conclusions}

Our near-exhaustive review was the first to consider all taxa when
addressing the evolution and function of, and costs and benefits to,
helical burrowing in animals. Our examination of the fit of 10
hypotheses to numerous living and extinct taxa failed to find compelling
evidence for one general hypothesis for why animals construct helical
burrows. Only two hypotheses----antipredator and biomechanical
advantage----could not be rejected for any species, although six of the
hypotheses could not be rejected for most species (possible in 86--100
\% of \emph{spp.} ). Thus, one or more of these could explain the
behavior of helical burrowing in most species. Four of these six were
construction hypotheses, raising the possibility that helical burrowing
might have evolved without providing post-construction benefits. Our
analysis did eliminate four hypotheses - increased drainage, deposit
feeding, microbial farming, and offspring escape -- as explanations for
helical burrowing behavior in the majority of taxa (possible in 5--48\%
of spp.). The extended phenotype of helical burrowing may have evolved
for a diversity of reasons. Further observations of helical burrowing in
different biotic and abiotic contexts, and in particular, experiments,
could in some cases eliminate or provide support for some of the
hypotheses, while other hypotheses are difficult to test, or not
directly testable.

\textbf{Tables}

See attached file.

\textbf{Figures}

See attached file.

\textbf{Data Accessibility}

All data are contained within this manuscript and its associated tables.

\textbf{Acknowledgments}

This research did not receive any specific grant from funding agencies
in the public, commercial, or not-for-profit sectors.

\textbf{References}

Abdel-Nabi, I. M., McVean, A., Abdel-Rahman, M. A., \& Omran, M. (2004).
Intraspecific diversity of morphological characters of the burrowing
scorpion \emph{Scorpio maurus palmatus} (Ehrenberg, 1828) in Egypt
(Arachnida: Scorpionida: Scorpionidae). \emph{Serket, 9} (2), 41-67.

Adams, A. M., Marais, E., Turner, J. S., Prendini, L., \& Pinshow, B.
(2016). Similar burrow architecture of three arid-zone scorpion species
implies similar ecological function. \emph{The Science of Nature, 103}
(7), 1-11.

Barbour, I. H. (1892). Notice of new gigantic fossils.\emph{Science}
(472), 99-100.

Barrass, R. (1963). The burrows of \emph{Ocypode
ceratophthalmus}(Pallas) (Crustacea, Ocypodidae) on a tidal wave beach
at Inhaca Island, Mocambique. \emph{The Journal of Animal Ecology} ,
73-85.

Basan, P. B., PB, B., \& RW, F. (1977). Actual-palaeontology and
neoichnology of salt marshes near sapelo island, georgia.

Belaústegui, Z., Gibert, J.M., López\selectlanguage{english}-Blanco, M., \& Bajo, I. (2014).
Recurrent Constructional Pattern of the Crustacean Burrow Sinusichnus
sinuosus from the Paleogene and Neogene of Spain.

Beynon, B. M., \& Pemberton, S. G. (1992). Ichnological signature of a
brackish water deposit: an example from the Lower Cretaceous Grand
Rapids Formation, Cold Lake oil sands area, Alberta.

Bradley, R.A. (1988). The influence of weather and biotic factors
behavior of the scorpion (\emph{Paruroctonus utahensis} ). \emph{Journal
Animal Ecology} 57:533-551.

Brady, N. C., \& Weil, R. R., (2002). The Nature and Properties of
Soils, 13th edition. Prentice Hall, Upper Saddle River, New Jersey.

Bromley, R. G. (1996), \emph{Trace Fossils. Biology, Taphonomy and
Applications} , 2nd ed., 361 pp. London: Chapman \& Hall.

Bromley, R. G., \& Frey, W. Robert. (1974). Redescription of the trace
fossil \emph{Gyrolithes} and taxonomic evaluation
of\emph{Thalassinoides} , \emph{Ophiomorpha} , and
\emph{Spongeliomorpha} . Geol. Soc. Denmark Bull. 23:311-335.

Brown, L. N., \& Hickman, G. C. (1973). Tunnel system structure of the
southeastern pocket gopher. \emph{Florida Scientist} , 97-103.

Buatois, L. A., Gingras, M. K., MacEachern, J., Mangano, M. G.,
Zonneveld, J.-P., Pemberton, S. G., . . . Martin, A. (2005).
Colonization of brackish-water systems through time: evidence from the
trace-fossil record. \emph{Palaios, 20} (4), 321-347.

Cameron, G. N., S. R. Spencer, B. D. Eshelman, L. R. Williams, And M. J.
Gregory. (1988). Activity and burrow structure of Attwater's pocket
gopher (\emph{Geomys attwateri} ). \emph{Journal of Mammalogy} , 69:
667-677.

Ceballos-G., Gerardo, Wilson, E. Don. (1985). Cynomys
mexicanus,~\emph{Mammalian Species} , Issue 248, 1--3,

Clayton, D. (2005). Substrate (acoustic/vibrational) communication and
ecology of the ghost crab \emph{Ocypode jousseaumei} (Brachyura:
Ocypodidae). \emph{Marine and Freshwater Behaviour and Physiology, 38}
(1), 53-70.

Clode, D. (2009). \emph{Prehistoric giants: the Megafauna of Australia}
: Museum Victoria Publishing.

Coelho, V. R., Cooper, R. A., \& de Almeida Rodrigues, S. (2000). Burrow
morphology and behavior of the mud shrimp \emph{Upogebia
omissa}(Decapoda: Thalassinidea: Upogebiidae). \emph{Marine Ecology
Progress Series, 200} , 229-240.

Curran, H.A., \& Seike, K. (2016). Modern and Fossil Callianassid
Burrows of the Bahamas: Comparisons and Implications for
Paleoenvironmental Analysis. Proceedings of the 16th Symposium on the
Geology of the Bahamas and Other Carbonate Regions, June 14-18, 2012.
In, B. Glumac and M. Savarese, eds. Gerace Research Centre, San
Salvador, Bahamas, p. 153-167.

Dafoe, L. T., Gingras, M. K., \& Pemberton, S. G. (2008). Analysis of
mineral segregation in Euzonus mucronata burrow structures: one possible
method used in the construction of ancient \emph{Macaronichnus
segregates} . \emph{Ichnos, 15} (2), 91-102.

Dawkins, R. (1982). The extended phenotype: The gene as the unit of
selection.

Dawkins, R. (2004). Extended phenotype--but not too extended. A reply to
Laland, Turner and Jablonka. \emph{Biology and Philosophy, 19} (3),
377-396.

De Carvalho, C. N., \& Baucon, A. (2010). \emph{Jurassic sex in the
beach? Macanopsis from the Kimmeridgian of Praia do Salgado
(Portugal).}Paper presented at the Workshop on Crustacean
Bioturbation---Fossil and Recent---Lepe 2010.

de Gibert, J. M., Mas, G., \& Ekdale, A. A. (2012). Architectural
complexity of marine crustacean burrows: unusual helical trace fossils
from the Miocene of Mallorca, Spain. \emph{Lethaia, 45} (4), 574-585.

de Gibert, J. M., Netto, R. G., Tognoli, F. M. W., \& Grangeiro, M. E.
(2006). Commensal worm traces and possible juvenile thalassinidean
burrows associated with \emph{Ophiomorpha nodosa} , Pleistocene,
southern Brazil. \emph{Palaeogeography, Palaeoclimatology,
Palaeoecology, 230} (1), 70-84.

Doody, J. S., James, H., Colyvas, K., Mchenry, C. R., \& Clulow, S.
(2015). Deep nesting in a lizard, deja vu devil's corkscrews: First
helical reptile burrow and deepest vertebrate nest. \emph{Biological
Journal of the Linnean Society, 116} (1), 13-26.

Doody, J. S., James, H., Ellis, R., Gibson, N., Raven, M., Mahony, S., .
. . McHenry, C. R. (2014). Cryptic and complex nesting in the
yellow-spotted monitor, \emph{Varanus panoptes} . \emph{Journal of
Herpetology, 48} (3), 363-370.

Doody, J. S., McGlashan, J., Fryer, H., Coleman, L., James, H.,
Soennichsen, K., . . . Clulow, S. (2020). Plasticity in nest site choice
behavior in response to hydric conditions in a reptile. \emph{Scientific
Reports, 10} (1), 1-10.

Doody, J. S., McHenry, C., Brown, M., Canning, G., Vas, G., \& Clulow,
S. (2018). Deep, helical, communal nesting and emergence in the sand
monitor: ecology informing paleoecology? \emph{Journal of Zoology, 305}
(2), 88-95.

Doody, J. S., McHenry, C. R., Durkin, L., Brown, M., Simms, A., Coleman,
L., . . . Clulow, S. (2018). Deep communal nesting by yellow-spotted
monitors in a desert ecosystem: indirect evidence for a response to
extreme dry conditions. \emph{Herpetologica, 74} (4), 306-310.

Doody, J. S., Soennichsen, K. F., James, H., McHenry, C., \& Clulow, S.
(2021). Ecosystem engineering by deep\selectlanguage{english}-nesting monitor
lizards.\emph{Ecology, 102} (4), e03271.

Dworschak, P.C. (1981). The pumping rates of the burrowing
shrimp\emph{Upogebia pusilla} (Petagna) (Decapoda:
Thalassinidea).\emph{Journal of Experimental Marine Biology and Ecology,
52} (1), 25-35.

Dworschak, P.C. (1987), The Biology of \emph{Upogebia pusilla} (PETAGNA)
(Decapoda, Thalassinidea). Marine Ecology, 8: 337-358.
https://doi.org/10.1111/j.1439-0485.1987.tb00193.x

Dworschak P.C. \& Ott, J.A. (1993). Decapod burrows in mangrove-channel
and back-reef environments at the Atlantic Barrier Reef,
Belize.\emph{Ichnos} 2:277--290

Dworschak, P.C. \& Pervesler, P. (1988) Burrows of \emph{Callianassa
bouvieri} Nobili 1904 from Safaga (Egypt, Red Sea) with some remarks on
the biology of the species. \emph{Senckenbergiana maritima} , 20, 1-17.

Dworschak, P.C., \& Rodrigues, S. D. A. (1997). A modern analogue for
the trace fossil \emph{Gyrolithes} : burrows of the thalassinidean
shrimp\emph{Axianassa australis} . \emph{Lethaia, 30} (1), 41-52.

Ekdale, A. A., Bromley, R. G., \& Pemberton, S. G.
(1984).\emph{Ichnology: The Use of Trace Fossils in Sedimentology and
Stratigraphy} , SEPM Short Course 15. Tulsa, Oklahoma, 319 p.

Eshky, A. A. (1985). \emph{Aspects of the ecology, behaviour and
physiology of the ghost crab Ocypode saratan (Forskal).} University of
Glasgow,

Felder, D. L. (2001). Diversity and ecological significance of
deep-burrowing macrocrustaceans in coastal tropical waters of the
Americas (Decapoda: Thalassinidea). \emph{Interciencia, 26} (10),
440-449.

Fellows, D. (1966). \emph{Zonation and burrowing behaviour of the ghost
crab Ocypode ceratophthalmus (Pallas) and Ocypode laevis (Dana) in
Hawaii, Honolulu.} MSc Thesis, Univ. Hawaii,

Fischer, S. A. and Hasiotis, S. T., 2018. Stratigraphic Changes in
Ichnopedofacies of the Upper Triassic Chinle Formation, Utah:
Implications to Paleohydrology and Paleoclimate. \emph{Annales
Societatis Geologorum Poloniae} , v. 88, p.127--162.

Gefen, E., \& Ar, A. (2004). Comparative water relations of four species
of scorpions in Israel: evidence for phylogenetic
differences.\emph{Journal of Experimental Biology, 207} (6), 1017-1025.

Gernant, R. E. (1972). The paleoenvironmental significance
of\emph{Gyrolithes} (Lebensspur). \emph{Journal of Paleontology} ,
735-741.

Gingras, M. K., Dashtgard, S. E., MacEachern, J. A., \& Pemberton, S. G.
(2008). Biology of shallow marine ichnology: a modern
perspective.\emph{Aquatic Biology, 2} (3), 255-268.

Gingras, M. K., Pemberton, S. G., Dashtgard, S., \& Dafoe, L. (2008).
How fast do marine invertebrates burrow? \emph{Palaeogeography,
Palaeoclimatology, Palaeoecology, 270} (3-4), 280-286.

Goldring, R. \& Jensen, S. (1994). Trace fossils and biofabrics at the
Precambrian-Cambrian boundary interval in western
Mongolia.\emph{Geological Magazine, 133} (4), 403-415.

Hadley, N. F. (1970). Water relations of the desert
scorpion,\emph{Hadrurus arizonensis} . \emph{Journal of Experimental
Biology, 53} (3), 547-558.

Hadley, N. F. (1990). Environmental physiology. In G. A. Polis
(Ed.),\emph{The Biology of Scorpions} (pp. 321--340). Stanford, CA:
Stanford University Press.

Hansell, M., \& Hansell, M. H. (2005). \emph{Animal architecture} :
Oxford University Press on Demand.

Harington, A. (1978). Burrowing biology of the scorpion\emph{Cheloctonus
jonesii Pocock} (Arachnida: Scorpionida: Scorpionidae). \emph{Journal of
Arachnology} , 243-249.

Hasiotis, S. T. (2003). Complex ichnofossils of solitary to social soil
organisms: understanding their evolution and roles in terrestrial
paleoecosystems. \emph{Palaeogeography, Palaeoclimatology,
Palaeoecology} , v. 192, p. 259-320.

Hasiotis, S. T., (2007). Continental ichnology: fundamental processes
and controls on trace-fossil distribution. In, W. Miller, III
(Ed.),\emph{Trace Fossils---Concepts, Problems, Prospects} , Elsevier
Press, p. 268-284.

Hasiotis, S. T., (2012). An Overview of the Diversity and Patterns in
Bioturbation preserved in Cambro-Ordovician Carbonate and Siliciclastic
Deposits of Laurentia. In, J. Derby, B. Fritz, S. A. Longacre, W. A.
Morgan, and C. A. Sternbach (Eds.), \emph{The Great American Carbonate
Bank} (p. 113-125). AAPG Memoir 89.

Hasiotis, S. T. and Bourke, M. C. (2006). Continental trace fossils and
museum exhibits: displaying burrows as organism behavior frozen in
time.\emph{The Geological Curator} , v. 8 (5), p. 211-226.

Hasiotis, S. T. and Mitchell, C. E. 1993. A comparison of crayfish
burrow morphologies: Triassic and Holocene fossil, paleo- and
neo-ichnological evidence, and the identification of their burrowing
signatures. \emph{Ichnos, 2} 291-314.

Hasiotis, S. T., Aslan, A. and Bown, T. M. 1993. Origin, architecture,
and paleoecology of the Early Eocene continental
ichnofossil\emph{Scaphichnium hamatum} . \emph{Ichnos, 3} 1-9.

Hasiotis, S. T., Miller, M. F., Isbell, J. L., Babcock, L. E., and
Collinson, J. W. (1999). Is Triassic Crayfish Fossil Evidence from
Antarctica Really Burrow Evidence of Mammal-like Reptiles? Resolving
Vertebrate from Invertebrate Burrows. \emph{Freshwater Crayfish12}
71-81.

Hasiotis, S. T., Wellner, R. W., Martin, A., and Demko, T. M. (2004),
Vertebrate burrows from Triassic and Jurassic continental deposits of
North America and Antarctica: their paleoenvironmental and
paleoecological significance. \emph{Ichnos} , v. 11, p. 103-124.

Hasiotis, S. T., McPherson, J., and Reilly, M. (2013). Using
Ichnofossils to Reconstruct the Depositional History of Sedimentary
Successions in Alluvial, Coastal Plain, and Deltaic Settings. \emph{2013
International Petroleum Technical Conference Proceedings} , Beijing,
China, 1-48.

Heger, N. A., \& Fox, S. F. (1992). Viability of lizard
(\emph{Sceloporus undulatus} ) eggs exposed to simulated flood
conditions. \emph{Journal of Herpetology, 26} (3), 338-341.

Hembree, D. I. (2009). Neoichnology of burrowing millipedes: linking
modern burrow morphology, organism behavior, and sediment properties to
interpret continental ichnofossils. \emph{Palaios, 24} (7), 425-439.

Hembree, D. I. (2014). Large complex burrows of terrestrial
invertebrates: neoichnology of \emph{Pandinus imperator} (Scorpiones:
Scorpionidae). In \emph{Experimental Approaches to Understanding Fossil
Organisms} (pp. 229-263): Springer.

Hembree, D. I., and Hasiotis, S. T. (2006). The identification and
interpretation of reptile ichnofossils in paleosols through modern
studies. \emph{Journal of Sedimentary Research} , v. 76, p. 575-588.

Horn, H. G., \& Visser, G. J. (1989). Review of reproduction of Monitor
lizards \emph{Varanm spp} in captivity. \emph{International Zoo
Yearbook, 28} (1), 140-150.

Horn, H. G., \& Visser, G. J. (1997). Review of reproduction of monitor
lizards \emph{Varanus spp} in captivity II. \emph{International Zoo
Yearbook, 35} (1), 227-246.

Hughes, D. P., \& Libersat, F. (2019). Parasite manipulation of host
behavior. \emph{Current Biology, 29} (2), R45-R47.

Hunter, P. (2018). The revival of the extended phenotype: after more
than 30 years, Dawkins' extended phenotype hypothesis is enriching
evolutionary biology and inspiring potential applications. \emph{EMBO
reports, 19} (7), e46477.

Jackson, A. M., Hasiotis, S. T., \& Flaig, P. P. (2016). Ichnology of a
Paleopolar, River-Dominated, Shallow Marine Deltaic Succession in the
Mackellar Sea: The Mackellar Formation (Lower Permian), Central
Transantarctic Mountains, Antarctica. \emph{Palaeogeography,
Palaeoclimatology, Palaeoecology, 441} , 266-291.
doi:https://doi.org/10.1016/j.palaeo.2015.07.010

James, R., Atkinson, A., \& Nash, R. D. (1990). Some preliminary
observations on the burrows of \emph{Callianassa subterranea} (Montagu)
(Decapoda: Thalassinidea) from the west coast of Scotland. \emph{Journal
of Natural History, 24} (2), 403-413.

Johnson, D. L. (1989). Subsurface stone lines, stone zones,
artifact-manuport layers, and biomantles produced by bioturbation via
pocket gophers (\emph{Thomomys bottae} ). \emph{American Antiquity, 54}
(2), 370-389.

Kennedy, W. J., Jakobson, M. E., \& Johnson, R. T. (1969). A
Favreina--Thalassinoides association from the Great Oolite of
Oxfordshire. \emph{Palaeontology, 12} (4), 549--554.

King, G. (1996). When the desert was green. \emph{Natural History, 105}
(3), 50-54.

Kinlaw, A., \& Grasmueck, M. (2012). Evidence for and geomorphologic
consequences of a reptilian ecosystem engineer: the burrowing cascade
initiated by the gopher tortoise. \emph{Geomorphology, 157} , 108-121.

Koch, L. (1978). A comparative study of the structure, function and
adaptation to different habitats of burrows in the scorpion
genus\emph{Urodacus} (Scorpionida, Scorpionidae). \emph{Records of the
Western Australian Museum, 6} (2), 119-146.

Koch, L. E. (1977). \emph{The taxonomy, geographic distribution and
evolutionary radiation of Australo-Papuan scorpions} (Vol. 5): Western
Australian Museum.

Kraus, M. J. (1999). Paleosols in clastic sedimentary rocks: their
geologic applications. \emph{Earth Science Reviews 47} 41-70.

Ksi\selectlanguage{polish}ąż\selectlanguage{english}kiewicz, M. 1977. Trace fossils in the Flysch of the Polish
Carpathians. \emph{Palaeontologia Polonica} 36: 1--208.

Laing, B. A., Buatois, L. A., M\selectlanguage{ngerman}ángano, M. G., Narbonne, G. M., \&
Gougeon, R. C. (2018). Gyrolithes from the Ediacaran-Cambrian boundary
section in Fortune Head, Newfoundland, Canada: Exploring the onset of
complex burrowing. \emph{Palaeogeography, Palaeoclimatology,
Palaeoecology, 495} , 171-185.

Lamoral, B.H. (1978). Soil hardness, an important and limiting factor in
burrowing scorpions of the genus \emph{Opisthophthalmus} C.L. Koch, 1837
(Scorpionidae, Scorpionida). \emph{Symposium of the Zoological Society
of London} 42: 171--181.

Lanés, Silvia \& Manceñido, Miguel \& Damborenea, Susana.
(2007).\emph{Lapispira} : A double helicoidal burrow from Jurassic
marine nearshore environments. \emph{Sediment-Organism Interactions: A
Multifaceted Ichnology.} 88. 59-78.

Linsenmair K. E. (1967). Konstruktion und Signalfunktion der
Sandpyramide der Reiterkrabbe \emph{Ocypode saratan} Forsk. (Decapoda
Brachyura Ocypodidae) {[}Construction and signal function of the sand
pyramid of the rider crab \emph{Ocypode saratan} . (Decapoda brachyura
ocypodidae){]}. \emph{Zeitschrift fur Tierpsychologie,} 24(4), 403--456.

Loope D. B. \& Dingus L. (1999). Mud-filled \emph{Ophiomorpha} from
Upper Cretaceous continental redbeds of southern Mongolia: An ichnologic
clue to the origin of detrital, grain-coating clays. \emph{Palaios} 14,
451--8

Losos, J. B., Schoener, T. W., \& Spiller, D. A. (2003). Effect of
immersion in seawater on egg survival in the lizard \emph{Anolis sagrei}
. \emph{Oecologia, 137} (3), 360-362.

Löwemark, L., \& Schäfer, P. (2003). Ethological implications from a
detailed X-ray radiograph and \textsuperscript{14}C study of the modern
deep-sea \emph{Zoophycos} . \emph{Palaeogeography, Palaeoclimatology,
Palaeoecology, 192} , 101-121.

Luoto, S. (2019). An updated theoretical framework for human sexual
selection: from ecology, genetics, and life history to extended
phenotypes. \emph{Adaptive Human Behavior and Physiology, 5} (1),
48-102.

Martin, L., \& Rice, J. (1994). The devil's corkscrew. \emph{Natural
History, 103} (4), 59-60.

Martin, L. D. (1989). Fossil history of the terrestrial Carnivora.
In\emph{Carnivore behavior, ecology, and evolution} (pp. 536-568):
Springer.

Martin, L. D., \& Bennett, D. K. (1977). The burrows of the Miocene
beaver \emph{Palaeocastor} , western Nebraska,
USA.\emph{Palaeogeography, Palaeoclimatology, Palaeoecology, 22} (3),
173-193.

Mayoral, E., \& Muñiz, F. (1995). Nueva ichnoespecie de Gyrolithes de
Mioceno Superior de la Cuenca del Guadalquivir (Lepe,
Huelva).\emph{Revista Española de Paleontología} , 10(2): 190--201.

Mayoral, E., \& Muñiz, F. (1998). Nueva datos icnotaxonomicos sobre
Gyrolithes del Plioceno Inferior de la Cuenca del Guadalquivir (Lepe,
Huelva, España). \emph{Revista Española de Paleontología} , 13(1):
61--69.

Meyer, R. C. (1999). Helical burrows as a palaeoclimate
response:\emph{Daimonelix} by \emph{Palaeocastor} .
\emph{Palaeogeography, Palaeoclimatology, Palaeoecology, 147} (3-4),
291-298.

Miku\selectlanguage{polish}ś, \selectlanguage{english}P., \& Uchman, A. (2013). Beetle burrows with a terminal chamber:
a contribution to the knowledge of the trace fossil \emph{Macanopsis} in
continental sediments. \emph{Palaios, 28} (6), 403-413.

Minter, N. J., Lucas, S. G., Lerner, A. J., \& Braddy, S. J.
(2008).\emph{Augerinoichnus} \emph{helicoidalis} , a new helical trace
fossil from the nonmarine Permian of New Mexico. \emph{Journal of
Paleontology, 82} (6), 1201-1206.

Monod, L., Harvey, M. S., \& Prendini, L. (2013). Stenotopic Hormurus
Thorell, 1876 scorpions from the monsoon ecosystems of northern
Australia, with a discussion on the evolution of burrowing behaviour in
Hormuridae Laurie, 1896. \emph{Revue suisse de Zoologie, 120} (2),
281-346.

Moosavizadeh, S. M. A., \& Knaust, D. (2021). The trace
fossil\emph{Gyrolithes} \emph{lorcaensis} from the Lower Cretaceous of
the Kopet-Dagh Basin, NE Iran. \emph{Ichnos} , 1-16.

Mu\selectlanguage{ngerman}ñiz, F., \& Belaústegui, Z. (2019). Helical crustacean
burrows:\emph{Gyrolithes} ichnofabrics from the Pliocene of Lepe
(Huelva, SW Spain). \emph{Palaios, 34} (1), 1-14.

Netto, R. G., Buatois, L. A., Mángano, M. G., \& Balistieri, P.
(2007).\emph{Gyrolithes} as a multipurpose burrow: An ethologic
approach.\emph{Revista Brasileira de Paleontologia, 10} (3), 157-168.

Netto, R. G., Curran, H. A., Belaústegui, Z., \& Tognoli, F. M. W.
(2017). Solving a cold case: New occurrences reinforce juvenile
callianassids as the \emph{Ophiomorpha} \emph{puerilis}
tracemakers.\emph{Palaeogeography, Palaeoclimatology, Palaeoecology,
475} , 93--105.

Nickell, L. A., \& Atkinson, R. J. A. (1995). Functional morphology of
burrows and trophic modes of three thalassinidean shrimp species, and a
new approach to the classification of thalassinidean burrow
morphology.\emph{Marine Ecology Progress Series, 128} , 181-197.

Oligmueller, A.R., and Hasiotis, S.T., (2022 in press). An
Ichnotaxonomic Assessment of the Cretaceous Dakota Group, Front Range,
Colorado, USA, and its Comparison to Other Western Interior Seaway
Deposits. \emph{University of Kansas Paleontological Contributions} .

Olivero, D. 2007. Zoophycos and the role of type species in
ichnotaxonomy. In W. Miller, ed., \emph{Trace Fossils: Concepts,
Problems, Prospects} . Elsevier, Amsterdam 219--231.

Parenzan, P. (1931). Osservazioni biologiche sull' \emph{Ocypode
ceratophthalma} F abr. Atti 1st. veneto Sci. 90, 1001-1008.

Paul, J., Mondal, S., Kayal, R., \& Sarkar, D. (2019). Burrow morphology
of the ocypodid crab \emph{Ocypode ceratophthalma} at Chandipur Coast,
Eastern India and its implications. \emph{Current Science (00113891),
117} (4).

Pervesler, P., \& Dworschak, P. C. (1985). Burrows of \emph{Jaxea
nocturna} Nardo in the Gulf of Trieste. \emph{Senckenbergiana maritima,
17} (1/3), 33-53.

Pervesler, P., \& Hohenegger, J. (2006). Orientation of crustacean
burrows in the Bay of Panzano (Gulf of Trieste, northern Adriatic
Sea).\emph{Lethaia, 39} (3), 173-186.

Pianka, E., \& King, D. (2004). \emph{Varanoid lizards of the world} :
Indiana University Press.

Polis, G. A. (1990). \emph{The Biology of Scorpions} . Stanford, CA:
Stanford University Press.

Poschmann, M. (2015). The corkscrew-shaped trace
fossil\emph{Helicodromites} Berger, 1957, from Rhenish Lower Devonian
shallow-marine facies (Upper Emsian; SW Germany). \emph{Paläontologische
Zeitschrift, 89} (3), 635-643.

Powell, E. N. (1977). The relationship of the trace
fossil\emph{Gyrolithes} (=\emph{Xenohelix} ) to the family Capitellidae
(Polychaeta). \emph{Journal of Paleontology} , 552-556.

Raisanen, D.C.W. and Hasiotis, S.T., 2018. New Ichnotaxa of Vertebrate
Burrows from the Salt Wash Member, Upper Jurassic Morrison Formation,
Southeastern Utah. \emph{Annales Societatis Geologorum Poloniae} , v.
88, p.181--202.

Riese, D.J., Hasiotis, S.T., and Odier, G., 2011. Burrows excavated by
mammals or therapsids in the Navajo Sandstone and their association with
other organisms represented by trace fossils in a wet desert
ecosystem.\emph{Journal of Sedimentary Research} , v. 81, p. 299-325.
DOI: 10.2110/jsr.2011.25

Rhoads, D. C. (1975). The paleoecological and environmental significance
of trace fossils. In \emph{The study of trace fossils} (pp. 147-160):
Springer.

Risk, M. J., \& Tunnicliffe, V. J. (1978). Intertidal spiral
burrows;\emph{Paraonis fulgens} and \emph{Spiophanes wigleyi} in the
Minas Basin, Bay of Fundy. \emph{Journal of Sedimentary Research, 48}
(4), 1287-1292.

Rismiller, P. D., McKelvey, M. W., \& Green, B. (2010). Breeding
phenology and behavior of Rosenberg's goanna (V\emph{aranus rosenbergi}
) on Kangaroo Island, South Australia. \emph{Journal of Herpetology, 44}
(3), 399-408.

Roberts, H. R., Wilkins, K. T., Flores, J., \& Thompson-Gorozpe, A.
(1997). Burrowing Ecology of Pocket Gophers (Rodentia: Geomyidae) in
Jalisco, Mexico.~\emph{The Southwestern Naturalist} ,~\emph{42} (3),
323--327. http://www.jstor.org/stable/30055283

Robinson, M. D., \& Seely, M. (1980). Physical and biotic environments
of the southern Namib dune ecosystem. \emph{Journal of Arid
Environments, 3} (3), 183-203.

Rusli, M. U., Booth, D. T., \& Joseph, J. (2016). Synchronous activity
lowers the energetic cost of nest escape for sea turtle
hatchlings.\emph{Journal of Experimental Biology, 219} (10), 1505-1513.

Sanders, H., Mangelsdorf Jr, P., \& Hampson, G. R. (1965). Salinity and
faunal distribution in the Pocasset River, Massachusetts
1.\emph{Limnology and Oceanography, 10} (suppl), R216-R229.

Sappenfield, A., Droser, M., Kennedy, M., \& McKenzie, R. (2012). The
oldest Zoophycos and implications for Early Cambrian deposit
feeding.\emph{Geological Magazine, 149(6)} , 1118-1123.

Schober, U., \& Christy, J. (1993). Sand disposal of the painted ghost
crab \emph{Ocypode gaudichaudii} (Decapoda: Ocypodidae): a possible role
in courtship. \emph{Marine Biology, 116} (1), 53-60.

Schultz, G. B. (1942). A review of the \emph{Daimonelix} problem.
University of Nebraska Studies in Science and Technology, 2, 1-30.

Seilacher, A. (2007). \emph{Trace fossil analysis} : Springer Science \&
Business Media.

Shorthouse, D., \& Marples, T. (1980). Observations on the Burrow and
Associated Behaviour of the Arid-Zone Scorpion \emph{Urodacus
Yaschenkoi} (Birula). \emph{Australian Journal of Zoology, 28} (4),
581-590.

Smith, R. M. (1987). Helical burrow casts of therapsid origin from the
Beaufort Group (Permian) of South Africa. \emph{Palaeogeography,
Palaeoclimatology, Palaeoecology, 60} , 155-169.

Smith, R. M. (1993). Vertebrate taphonomy of Late Permian floodplain
deposits in the southwestern Karoo Basin of South Africa.\emph{Palaios}
, 45-67.

Smith, R. M., Angielczyk, K. D., Benoit, J., \& Fernandez, V. (2021).
Neonate aggregation in the Permian dicynodont
\emph{Diictodon}(Therapsida, Anomodontia): Evidence for a reproductive
function for burrows? \emph{Palaeogeography, Palaeoclimatology,
Palaeoecology, 569} , 110311.

Spinks, A. C., Bennett, N. C., \& Jarvis, J. U. M., (2000). A comparison
of the ecology of two populations of the common mole-rat,\emph{Cryptomys
hottentotus hottentotus} : the effect of aridity on food, foraging and
body mass. \emph{Oecologia} , \emph{125} , 341--349.

Soares, J. L., Santos, H. P., Brito, A. d. S., Nogueira, A. A. E.,
Nogueira, A. C., \& Amorim, K. B. (2020). The crustaceans
burrow\emph{Sinusichnus sinuosus} from the Oligocene-Miocene carbonate
deposits of eastern Amazonia. \emph{Ichnos, 27} (2), 97-106.

Stull, R. B. (1988). \emph{An introduction to boundary layer
meteorology} (Vol. 13): Springer Science \& Business Media.

Toolson, E. C., \& Hadley, N. F. (1977). Cuticular permeability and
epicuticular lipid composition in two Arizona vejovid
scorpions.\emph{Physiological Zoology, 50} (4), 323-330.

Vannini, M. (1980). Researches on the coast of Somalia. The shore and
the dune of Sar Uanle: 27. Burrows and digging behaviour in ocypode and
other crabs (Crustacea Brachyura). \emph{Monitore Zoologico Italiano.
Supplemento, 13} (1), 11-44.

Vazirianzadeh, B., Jalali, A., Chrom, M., Mohammady, A., Vatandoost, H.,
\& Panahi, F. (2017). A comparative study of nesting sites and burrowing
habits of two Iranian burrowing scorpions. \emph{Journal of
Arthropod-Borne Diseases, 11} (1), 78.

Villa, B.C. (1989). Caracteristicas generales de la construccion de las
galerias de \emph{Pappogeomys merriami merriami} (Rodentia: Geomyidae)
en Chalco, Mexico. Anales Institut de Biologia Universidad Nacional
Autonoma. Mexico, Ser. Zool., 59:117 122.

Vleck, D. (1981). Burrow structure and foraging costs in the fossorial
rodent, \emph{Thomomys bottae} . \emph{Oecologia, 49} (3), 391-396.

Weber, J. N., \& Hoekstra, H. E. (2009). The evolution of burrowing
behaviour in deer mice (genus \emph{Peromyscus} ). \emph{Animal
Behaviour, 77} (3), 603-609.

Weber, J. N., Peterson, B. K., \& Hoekstra, H. E. (2013). Discrete
genetic modules are responsible for complex burrow evolution
in\emph{Peromyscus} mice. \emph{Nature, 493} (7432), 402-405.

Wetzel, A., Tjallingii, R., \& Stattegger, K. (2010).
\emph{Gyrolithes}in Holocene estuarine incised-valley fill deposits,
offshore southern Vietnam. \emph{Palaios, 25} (4), 239-246.

White, C. R. (2001). The energetics of burrow excavation by the inland
robust scorpion, \emph{Urodacus yaschenkoi} (Birula,
1903).\emph{Australian Journal of Zoology, 49} (6), 663-674.

Wilkins, K. T., \& Roberts, H. R. (2007). Comparative analysis of burrow
systems of seven species of pocket gophers (Rodentia:
Geomyidae).\emph{The Southwestern Naturalist, 52} (1), 83-88.

Williams, S. C. (1966). Burrowing activities of the
scorpion\emph{Anuroctonus phaeodactylus} (Wood) (Scorpionida:
Vejovidae).\emph{Proceedings of the California Academy of Sciences, 4th
series, 34} , 419-428.

Wolfe, J., \& RJ, E. (1977). Burrowing behaviour of old-field mice
(\emph{Peromyscus polionotus} ). A laboratory investigation. \emph{Biol.
Behav.}

Wood, H. E., \& Wood, A. E. (1933). \emph{Daemonhelix} in the
Pleistocene of Texas. \emph{Journal of Geology} , 41: 824-833.

Zhang, L. J., Fan, R.-Y., \& Gong, Y.-M. (2015). Zoophycos
macroevolution since 541 Ma. \emph{Scientific Reports, 5,} 14954 (2015).
https://doi.org/10.1038/srep14954.

Zonneveld, J.-P., Fiorillo, A.R., Gingras, M.K., and Hasiotis, S.T.,
(2022), Tooth-marks, gnaw marks, claw-marks, bite marks, scratch marks,
etc: terminology in Ichnology. \emph{Annales Societatis Geologorum
Poloniae} , p. 1--9; doi.org/10.1080/10420940.2022.2058937.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Fig. 1. Helical burrows in extant taxa. (A) Top-down view of
a\emph{Varanus panoptes} nesting burrow from Australia (J. S. Doody).
(B) Side view of a \emph{Varanus gouldii} nesting burrow from Australia
(J. S. Doody). (C) Diagram depicting \emph{Varanus gouldii} nesting
burrows (Doody et al., 2018). (D) Casts of scorpion burrows (top panels)
and entrances (bottom panels) from Australia (Hasiotis and Bourke,
2006).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Fig. 2. Helical burrows in extinct taxa. (A) \emph{Gyrolithes} probably
created by Crustaceans during the Miocene from the Cacela Formation,
Portugal (Cachao et al., 2009). (B) \emph{Helicodromites} probably
created by vermiform animals during the Devonian from the Hohenrein and
Laubach Formations, Germany (Poschmann 2015). (C)
\emph{Gyrolithes}created by shrimp during the Pliocene from the
Guadlquivir Basin, Spain (Muniz and Belaustegui, 2019). (D)
\emph{Daimonelix} burrows created by\emph{Paleocaster} during the late
Oligocene-early Miocene in the Harrison Formation, United States
(Martin, 1977; Permission granted to use, see Doody et al., 2015).

\textbf{6. Tables}

Table 1. Hypotheses for helical or spiral burrows across 21 extant and
extinct genera and ichnogenera representing 59--184 \emph{spp} .\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllll@{}}
\toprule
\begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Post-construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Construction benefits}\strut
\end{minipage} & \begin{minipage}[b]{0.07\columnwidth}\raggedright\strut
\textbf{Construction benefits}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Genus/\textbf{Ichnogenus} (\# spp.)\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Anti- predator\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Micro-climate Buffer\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Increased drainage\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Deposit feeding\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Microbial farming\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Offspring escape\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Reduced falling soil\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Anti-crowding\textsuperscript{y}\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Vertical patch\textsuperscript{y}\strut
\end{minipage} & \begin{minipage}[t]{0.09\columnwidth}\raggedright\strut
Biomechan. advantage\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Anuroctonus} (2)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Axianassa} (13)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Axiopsis} (1)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Callianassa} (2-47)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Cratogeomys} (1)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
unlikely\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Cylindrichnus} \textbf{(2)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Cynomys\textsuperscript{x}} (1)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
unlikely\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Daimonelix} \textbf{(2-4)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{unlikely}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Diictodon} \textbf{(1-7)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{unlikely}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Geomys} (3)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
unlikely\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Gyrolithes} \textbf{(15)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Helicodromites} \textbf{(2)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{unlikely}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{unlikely}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Lapispira} \textbf{(1)}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{unlikely}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{n/a}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\textbf{Poss.}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\emph{Notomastus} (1)\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
n/a\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Poss.\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllll@{}}
\toprule
\emph{Ocypode} (1) & Poss. & Poss. & n/a & Poss. & n/a & n/a & Poss. &
Poss. & Poss. & Poss.\tabularnewline
\midrule
\endhead
\emph{Ophiomorpha} \textbf{(1-3)} & \textbf{Poss.} & \textbf{Poss.} &
\textbf{n/a} & \textbf{Poss.} & \textbf{Poss.} & \textbf{n/a} &
\textbf{Poss.} & \textbf{Poss.} & \textbf{Poss.} &
\textbf{Poss.}\tabularnewline
\emph{Opisthophthalmus} (1-61) & Poss. & Poss. & Poss. & n/a & n/a & n/a
& Poss. & Poss. & Poss. & Poss.\tabularnewline
\emph{Paleocaster} \textbf{(1-4)} & \textbf{Poss.} & \textbf{Poss.} &
\textbf{Poss.} & \textbf{unlikely} & \textbf{n/a} & \textbf{n/a} &
\textbf{Poss.} & \textbf{Poss.} & \textbf{Poss.} &
\textbf{Poss.}\tabularnewline
\emph{Paruroctonus} (1-8) & Poss. & Poss. & Poss. & n/a & n/a & n/a &
Poss. & Poss. & Poss. & Poss.\tabularnewline
\emph{Urodacus} (5) & Poss. & Poss. & Poss. & n/a & n/a & n/a & Poss. &
Poss. & Poss. & Poss.\tabularnewline
\emph{Varanus} (2) & Poss. & unlikely & unlikely & n/a & n/a & Poss. &
Poss. & Poss. & Poss. & Poss.\tabularnewline
SCORE: & 100\% & 86\% & 48\% & 48\% & 24\% & 5\% & 95\% & 95\% & 95\% &
100\%\tabularnewline
\bottomrule
\end{longtable}

Table 1. Hypotheses for helical or spiral burrows across 21 extant and
extinct genera and ichnogenera representing 59--184 \emph{spp} . (see
text for explanation of why there is a range in the number of species).
Designations include `poss.' (possible), `unlikely', or `n/a' (not
applicable, not possible, or highly unlikely). Scores = the proportion
(\%) possible for each taxon. \textsuperscript{X} = ichnotaxa \& modern
taxa; y = could also result in post-construction benefits. Data based on
deductive reasoning and the following sources:
\emph{Anuroctonus}(Williams, 1966); \emph{Axianassa} (Dworschak and
Rodriguez, 1997; Felder, 2001; Netto et al., 2007); \emph{Axiopsis}
(Dworschak and Ott, 1993); \emph{Callianassa} (Dworschak and Pervesler,
1988; Atkinson and Nash, 1990; James et al., 1990; Nickell and Atkinson,
1995);\emph{Cratogeomys} (Villa, 1989; Roberts et al., 1997; Wilkins and
Roberts, 2007); \emph{Cylindrichnus} (de Gibert et al.,
2006);\emph{Cynomys} (Wood \& Wood, 1933; Schultz, 1942; Ceballos-G and
Wilson, 1985); \emph{Daimonelix} (Fischer and Hasiotis, 2018; Raisanen
and Hasiotis, 2018); \emph{Diictodon} (Smith, 1987; Smith, 1993; King,
1996; Smith et al., 2021); \emph{Geomys} (Brown and Hickman, 1973;
Cameron et al., 1988; Wilkins and Roberts, 2007);
\emph{Gyrolithes}(Gernant, 1972; Bromley and Frey, 1974; Powell, 1977;
Ekdale et al., 1984; Beynon and Pemberton, 1992; Mayoral and Mu\selectlanguage{ngerman}ñiz,
1995; Bromley, 1996; Dworschak and Rordrigues, 1997; Mayoral and Muñiz,
1998; Buatois et al., 2005; Netto et al., 2007; Wetzel et al., 2010; de
Gibert et al., 2012; Hasiotis et al., 2013; Jackson et al., 2016; Laing
et al., 2018; Muniz and Belastegui, 2019; Moosavizadeh and Knaust, 2021;
Oligmueller and Hasiotis, 2022); \emph{Helicodromites} (Poschmann,
2015);\emph{Lapispira} (Lanes et al., 2007; de Gibert et al.,
2012);\emph{Notomastus} (Powell, 1977); \emph{Ocypode} (Parenzan, 1931,
in: Eshky, 1985; Fellows, 1966, in: Vannini, 1980; Schober and Christy,
1993; Clayton, 2005); \emph{Ophiomorpha} (Loope and Dingus, 1999; de
Gibert et al., 2012); \emph{Opisthophthalmus} (Lamoral,
1978);\emph{Paleocaster} (Martin and Bennett, 1977; Meyer,
1999);\emph{Paruroctonus} (Bradley, 1988); \emph{Urodacus} (Koch, 1977;
1978; Shorthouse and Marples, 1980; White, 2001; Adams et al.,
2016);\emph{Varanus} (Doody et al., 2014; Doody et al., 2015; Doody et
al., 2018a,b; Doody et al., 2020).

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\selectlanguage{english}
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\end{document}

