Three-Dimensional Geometric Morphometric Analysis of Treeshrew (Scandentia) Lower Molars: Insight into Dental Variation and Systematics.

Scandentia (treeshrews) is an order of small-bodied Indomalayan mammals generally agreed to be a member of Euarchonta with Primates and Dermoptera (colugos). However, intraordinal relationships among treeshrews are less well understood. Although recent studies have begun to clarify treeshrew taxonomy using morphological and molecular datasets, previous analysis of treeshrew dentition has yielded little clarity in terms of species-level relationships within the order. However, these studies made use of character-based methods, scoring traits across the dental arcade, which depend on there being clear differences among taxa that can be encapsulated in coding schemes. Geometric morphometrics has the potential to capture subtler shape variation, so it may be better for examining similarities among closely related taxa whose teeth have a similar bauplan. We used three-dimensional geometric morphometrics on a sample of treeshrew lower second molars and compared the patterns of variation to the results of previous studies. We captured 19 landmarks on a sample of 43 specimens representing 15 species. Using specimen-based principal components analysis and between-group principal component analysis, the two treeshrew families (Tupaiidae and Ptilocercidae) were well separated in morphospace. Moreover, several treeshrew species plot in morphospace according to the clades established in previous molecular work, with closely related species plotting closer to one another than to more distantly related species, suggesting that dental morphology can be useful when studying relationships among treeshrews. As most extinct treeshrews are known only from teeth, understanding morphological patterns in treeshrew molars is important for future work on the evolutionary history of Scandentia. Anat Rec, 302:1154-1168, 2019. © 2019 Wiley Periodicals, Inc.