Re-examination of the Jurassic Mammaliaform Docodon victor by Computed Tomography and Occlusal Functional Analysis.

Docodon was the first described docodont, and has long featured prominently in the comparative and functional morphology of mammaliaform mandibles and teeth. We have now re-examined the dental and mandibular fossils of Docodon from Yale Quarry 9 at the Como Bluff site in the Late Jurassic Morrison Formation, using Computed Tomography (CT) scans and 3D image analyses. Our CT study revealed that some features used to distinguish the several Docodon "species" in historical studies many decades ago were based on incorrect manual restoration of mandibles, and on variable features of deciduous premolars, which are replaced in typical mammaliaform fashion. This supports a long-held notion that the multiple species of Docodon from the same quarry of the Morrison Formation are over-split and should be synonymized. We formally propose that the specimens examined in this study be synonymized under Docodon victor. Our new Occlusal Fingerprint Analysis (OFA) of Docodon molars supports the hypothesis that Docodon had a consistent dorso-posterior or palinal component in chewing in the disto-distolingual to distolingual direction. This helps to resolve the controversial historical alternative hypotheses postulated for tooth occlusion in the taxon. The Docodon occlusal pattern is likely a derived feature, evolved within Docodonta. A posterior component in the occlusal trajectory is a functional convergence of Docodon on unrelated traversodontid cynodonts. [ABSTRACT FROM AUTHOR]