The Postcranial Morphology of Ptilocercus lowii (Scandentia, Tupaiidae): An Analysis of Primatomorphan and Volitantian Characters
- Cite this article as:
- Sargis, E.J. Journal of Mammalian Evolution (2002) 9: 137. doi:10.1023/A:1021387928854
The eutherian orders Scandentia, Primates, Dermoptera, and Chiroptera have been grouped together by many morphologists, using various methods and data sets, into the cohort Archonta. Molecular evidence, however, has supported a clade (called Euarchonta) that includes Scandentia, Primates, and Dermoptera, but not Chiroptera. Within Archonta, some systematists have grouped Dermoptera and Chiroptera in Volitantia, while others have grouped Dermoptera and Primates in Primatomorpha. The order Scandentia includes the single family Tupaiidae, with two subfamilies, Ptilocercinae and Tupaiinae. Ptilocercinae is represented only by Ptilocercus lowii, which has been said to be the taxon most closely approximating the ancestral tupaiid. However, most researchers working on archontan phylogeny typically do not treat the order Scandentia as being polymorphic. They usually use Tupaia to represent Scandentia, despite the fact that Ptilocercus is quite distinct from Tupaia and has been argued to be the more plesiomorphic of the two taxa. In this study, a character analysis was performed on postcranial features that have been used to support the competing Primatomorpha and Volitantia hypotheses. In recognition of the polymorphic nature of Scandentia, taxonomic sampling within Scandentia was increased to include Ptilocercus. The postcranium of Ptilocercus was compared to that of tupaiines, euprimates, plesiadapiforms, dermopterans, and chiropterans. Several character states used to support either Primatomorpha or Volitantia, while not found in Tupaia, were found in Ptilocercus. While these features may have evolved independently in Ptilocercus, it is perhaps more likely that they represent features that first evolved in the ancestral archontan and were then lost in one of the extant orders. This character analysis greatly reduces the supportive evidence for the Primatomorpha hypothesis.