Using three-dimensional geometric morphometric and dental topographic analyses to infer the systematics and paleoecology of fossil treeshrews (Mammalia, Scandentia)

Abstract

<jats:title>Abstract</jats:title><jats:p>Treeshrews are small, Indomalayan mammals closely related to primates. Previously, three-dimensional geometric morphometric analyses were used to assess patterns of treeshrew lower second molar morphology, which showed that the positions of molar landmarks covary with intraordinal systematics. Another analysis used dental topographic metrics to test patterns of functional dental morphology and found that molar curvature, complexity, and relief were an effective means for examining patterns of variation in treeshrew dietary ecology. Here, we build on these analyses by adding two fossil taxa, <jats:italic>Prodendrogale yunnanica</jats:italic> Qiu, 1986 from the Miocene of China and <jats:italic>Ptilocercus kylin</jats:italic> Li and Ni, 2016 from the Oligocene of China. Our results show that <jats:italic>Pr. yunnanica</jats:italic> had a dental bauplan more like that of a tupaiid than that of a ptilocercid, but that the extant tupaiids, including <jats:italic>Tupaia</jats:italic> and <jats:italic>Dendrogale</jats:italic>, are more similar to one another in this regard than any are to <jats:italic>Prodendrogale.</jats:italic> This is contrary to our expectations as <jats:italic>Prodendrogale</jats:italic> is hypothesized to be most closely related to <jats:italic>Dendrogale. Ptilocercus kylin,</jats:italic> which has been proposed to be the sister taxon of <jats:italic>Pt. lowii</jats:italic> Gray, 1848, is characterized by dental morphology like that of <jats:italic>Pt. lowii</jats:italic> in crest and cuspal position but is interpreted to have been more frugivorous. It has been claimed that <jats:italic>Ptilocercus</jats:italic> has undergone little morphological change through time. Our results suggest that <jats:italic>Pt. kylin</jats:italic> was more ecologically distinct from <jats:italic>Pt. lowii</jats:italic> than previously proposed, providing a glimpse into a more complex evolutionary history of the group than had been inferred.</jats:p>