The relationship between bone shell microanatomy and palaeoecology in Testudinata from South America

Extant turtles exhibit a range of ecological adaptations to terrestrial and pelagic marine habitats. Bone shell microanatomy, and specifically, qualitative and quantitative approaches to shell bone porosity, have been used to infer palaeoecology and habitat. However, such inferences are hindered by the lack of a comprehensive sampling of testudine taxa and, in some instances, of long bones of vertebrates other than turtles. In this paper, we carry out an osteohistological analysis of Testudinata shell bones, including 31 different taxa, both extant and extinct, of known habitats. Costal and peripheral elements of published species and new data presented here are statistically analysed. Although, in some cases, values are congruent with those expected for a particular habitat (e.g. Hydromedusa casamayorensis), this is not true for all taxa examined. Moreover, microanatomical features of several taxa (e.g. Chelonia mydas) are inconsistent with habitat data. Results indicate that, although the microanatomical structure of the shell is related to habitat, this is not the only influence and indeed, in several cases, not the most important factor.