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Multituberculates remain one of the more poorly understood mammalian
clades. The North American multituberculate record is comprised mostly of
isolated teeth and incomplete jaws leading to interpretations of
relationships based on limited anatomy. Despite the fragmentary record,
the p4 of cimolodontan multituberculates is both common and a source of
diagnostic characters in systematic studies. The results of a recent
morphometric study on the neoplagiaulacid Mesodma suggest that p4 size may
be more useful than shape in diagnosing the various species referred to
this genus. We tested this hypothesis by applying two different
morphometric methods (2D geometric morphometrics and linear measurements)
to two samples – (1) one including the p4s of four known species (M.
ambigua, M. thompsoni, M. formosa, and M. pygmaea), and (2) a sample of
unidentified p4s of Mesodma from the Bug Creek Anthills locality of
Northeastern Montana. Our results indicate that while form explains most
of the morphological variation in p4s of the various species of Mesodma,
linear measurement data support differences in p4 morphology that are not
recovered by form data alone. Depending on the methods used, we found
evidence for the presence of one or more species of Mesodmain the Bug
Creek Anthills fauna. Although shape and size both contribute to
morphological variation in the p4 of Mesodma, our results suggest that the
diagnostic power of each in isolation, or in combination, varies
significantly with the type of methodology employed.
13 views reported since publication in 2023.