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Taeniodonta is a group of North America Palaeogene mammals that lived after the end-Cretaceous mass extinction. Taeniodonts show an extreme degree of dental wear, indicative of an abrasive diet, leading to hypsodonty in the most derived species. The rarity of fossils and their highly worn teeth makes their dental morphology difficult to study. We examined five new partial mandibles from the San Juan Basin, New Mexico, USA, most of which preserve unworn molars. One of the specimens preserves a deciduous ultimate premolar and using 3D micro-CT we were able to segment and study the unworn permanent tooth embedded in the jaw. We then conducted multivariate analyses on dental measurements to compare the new specimens to known teeth of early taeniodonts. We assigned the new specimens to at least three genera of Conoryctidae, a taeniodont subclade. Our results suggest that there is a broader dental diversity of the studied genera than previously thought. Morphological observations also suggest that progressive loss of cingulids and the addition of cuspids started early in the evolution of taeniodonts. These distinctive dental specializations strengthen the hypothesis that early Palaeocene mammals were able to rapidly adapt to fill the vacant ecological niches after the end-Cretaceous extinction
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THE PHYLOGENY OF THE EARLY PALAEOCENE ORDER TAENIODONTA USING NEW SPECIMENS FROM NEW MEXICO, USA
After the Cretaceous-Palaeogene (K-Pg) mass extinction mammals thrived in the Cenozoic. However, the phylogenetic affinities of early Palaeogene ‘archaic’ mammals that lived immediately after the extinction remain unresolved. Taeniodonta is a group of puzzling ‘archaic’ mammals that appeared in the early Palaeocene of North America. They are arranged into two subgroups; the Conoryctidae and Stylinodontidae and are characterised by their extreme degree of dental wear, indicating an abrasive diet, which led to hypsodonty in the most derived species. Due, in part, to their worn teeth and their rarity in the fossil record, the position of taeniondonts in the mammalian phylogenetic tree remains unresolved. New fossils from San Juan basin, New Mexico, USA, including unworn teeth of four genera and postcranial elements of an early taeniodont, Conoryctes, shed light on their dental and postcranial anatomy. Both in the forelimb and hind limp of Conoryctes, there are anatomical adaptations towards fossoriality. Using these specimens, we scored taeniodonts and other Palaeogene mammals into a phylogenetic data matrix (620 characters, 135 taxa). We then conducted a phylogenetic analysis using parsimony. Our results show that Taeniodonta is a monophyletic group within Eutheria. We also found that Onychodectes is basal to the two subgroups previously proposed. Based on the new postcranial fossils and revised phylogeny, we concluded that digging behaviours were likely ancestral for taeniodonts. Therefore, a more fossorial mode of life may have been beneficial for their surviving and thriving in the wake of the K-Pg extinction.
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- Award ID(s):
- 1654952
- PAR ID:
- 10482353
- Publisher / Repository:
- European Association of Vertebrate Paleontology
- Date Published:
- Journal Name:
- European Association of Vertebrate Paleontology Abstract Volume
- Subject(s) / Keyword(s):
- Palaeogene mammals extinction anatomy phylogeny
- Format(s):
- Medium: X
- Location:
- Benevento Italy
- Sponsoring Org:
- National Science Foundation
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