Figure 2. Photos showing shell morphology of the two species
land snails. The sampling strategy along with the growth band was also
shown.
2.3 Ecological habits of the two species
The two species of land snails used in this study have different living
habits. C. pulveratrix usually lives in relatively cold and dry
climates whereas M. yantaiensis lives in warm and sub-humid
climates (Wu et al. , 1996; Chen and Wu, 2008). The pictures for
two species of land snails are shown in Figure 2. Both species are also
living in the modern time. According to Chen (2016), C.
pulveratrix distributes over a vast area including Shanxi, Henan,
Hunan, Shaanxi, Gansu, Xinjiang provinces, and even in central Asia. The
habitat for C. pulveratrix is usually in thick grasses or under
the litter beneath trees in mountain area, on flat slope of hills as
well as in ranches, orchards and crop land. M. yantaiensisdistributes usually in northern China, i.e., Beijing, Tianjin, Hebei,
Shanxi, Inner Mongolia, Shandong and Shaanxi, and also shows in area
around the Yangtze River. It often lives in slightly damp bushes,
grasses, under rocks and leaves in in mountainous and hilly areas.
Shell size comparion shows that C. pulveratrix is usually larger
than M. yantainesis (Table 1). This morphology difference
complies with their living environment conditions.According to previous
studies, the large shell can reduce the ratio of surface area to volume,
thereby limiting water evaporation and making it easier for the snails
to survive in drier environments(Nevo et al., 1983; Yanes and
Fernández-Lopez-de-Pablo, 2016).
Table 1 Snail shell sizes of the two species at various MIS
stages.