Meeting Abstract
The turtle family Kinosternidae consists of 26 species in 4 genera. Members of this group are restricted to the new world, ranging from southern Canada to central South America. These turtles occupy a range of habitats, but all are aquatic or semiaquatic, and typically walk along the bottom of water bodies rather than swimming. They are mostly small turtles, with to carpace lengths of 105-380mm. These turtles have unique shell shapes and constructions (many species possess hinged plastrons). The goal of this study was to determine whether these unique shells also showed unique patterns of morphological or functional evolution among turtles. Data consisted of 3D landmark data captured from scute triple junctions of 214 specimens of 23 kinosternid species. The lineage density of kinosternids was not significantly higher or lower than those of other turtle species. We found strong evidence of phylogenetic signal in kinosternid shell shape, as with other turtles. There is a significant pattern of allometry among kinosternids, but, size explained very little variation in shell shape. The direction of allometry differed from that of other turtle families. We assessed shell mechanics using finite element modeling, and shell hydrodynamics, heat transfer, and stability by calculating a series of morphological indices known to be associated with those functions. Kinosternid shell performance does not fall outside the range of other hard-shelled turtles for any of those functions, but kinosternids do show a unique combination of strong carapaces, weak plastrons, and moderate streamlining, stability, and heat transfer ability. Despite their unique shell shapes, kinosternids do not show any unusual patterns of morphological evolution, although they do show a unique combination of shell performance measures.
