Micro-anatomy of the volar skin and interordinal relationships of primates

Paleontological and molecular evidence have been employed to suggest that f lying lemurs (Dermoptera) and primates form a monophyletic group, in sharp contrast with cranial and postcranial evidence indicating sister group rela tionships between flying lemurs and bats (Chiroptera). New evidence from th e epidermis of the volar pads of primates, tree shrews, flying lemurs, bats , and other mammals was examined and mapped on to various hypotheses of arc hontan relationships. The micro-anatomy of the skin on the palm and sole of flying lemurs and bats differs fundamentally from that of tree shrews (Sca ndentia) and primates. The volar skin of flying lemurs and bats lacks the s erial arrangement of papillary ridges and grooves ("fingerprints") found in primates, tree shrews, and many other mammals. Moreover, the junction betw een the epidermis and dermis in flying lemurs and bats is relatively flat a nd shows little or no development of the internal ridges that occur in prim ates and tree shrews. When mapped on to a set of cladograms of mammals curr ently allocated to the superorder Archonta, this new evidence does not supp ort sister group relationships between flying lemurs and primates, regardle ss of the volar skin morphology that characterized the last common ancestor of Archonta. Micro-anatomical differences that distinguish the volar skin of flying lemurs and bats from that of primates and tree shrews reflect a p rofound dichotomy in the functional roles fulfilled by the extremities, whi ch could be significant in a phylogenetic context. (C) 2000 Academic Press.