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

Abstract

AbstractTreeshrews 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,Prodendrogale yunnanicaQiu, 1986 from the Miocene of China andPtilocercus kylinLi and Ni, 2016 from the Oligocene of China. Our results show thatPr. yunnanicahad a dental bauplan more like that of a tupaiid than that of a ptilocercid, but that the extant tupaiids, includingTupaiaandDendrogale, are more similar to one another in this regard than any are toProdendrogale.This is contrary to our expectations asProdendrogaleis hypothesized to be most closely related toDendrogale. Ptilocercus kylin,which has been proposed to be the sister taxon ofPt. lowiiGray, 1848, is characterized by dental morphology like that ofPt. lowiiin crest and cuspal position but is interpreted to have been more frugivorous. It has been claimed thatPtilocercushas undergone little morphological change through time. Our results suggest thatPt. kylinwas more ecologically distinct fromPt. lowiithan previously proposed, providing a glimpse into a more complex evolutionary history of the group than had been inferred.