The post-cranial anatomy and functional morphology of Conoryctes comma (Mammalia: Taeniodonta) from the Paleocene of North America

PLoS One. 2024 Oct 25;19(10):e0311053. doi: 10.1371/journal.pone.0311053. eCollection 2024.

Abstract

Conoryctes comma is a member of the enigmatic group Taeniodonta, Paleogene mammals that have been found only in North America. Taeniodonts were part of the first wave of placental mammal diversification after the end-Cretaceous extinction. The lack of postcranial elements has limited the understanding of the anatomy and locomotion of Conoryctes, and how it compared to other taeniodonts. We here describe the postcranial anatomy and functional morphology of Conoryctes, based largely on nine new specimens found in the San Juan Basin, New Mexico, USA. The specimens include elements of the axial column, such as the axis, sacrum, and ribs; the humerus, ulna, radius, and part of the manus; the innominate, femur, tibia, and part of the pes, including the tarsals. Conoryctes was a medium-sized mammal, with a robust humerus, radius, and femur, and with anatomical similarities to other conoryctid taeniodonts and Onychodectes. The tarsal elements of Conoryctes show characteristics of the "leptictimorph astragalocalcaneal morphology" as seen in other Paleogene mammals, such as Escavadodon, Palaeanodon, and Procerberus. Anatomical features of the forelimb and hindlimb of Conoryctes indicate that it was a scratch-digging animal with powerful forearm muscles and well-stabilized digits, features that may have helped it adapt to the subtropical forests of the San Juan Basin, approximately 63 million years ago. This corroborates the previous hypothesis that digging adaptations are seen in all members of Taeniodonta for which the postcranial elements are known, and that digging ability was present in the common ancestor of the clade and potentially central to their radiation after the environmental destruction of the end-Cretaceous extinction.

MeSH terms

  • Animals
  • Biological Evolution
  • Bone and Bones / anatomy & histology
  • Fossils* / anatomy & histology
  • Mammals* / anatomy & histology
  • New Mexico
  • North America
  • Phylogeny
  • Skull / anatomy & histology

Grants and funding

ZK was funded by the European Research Council Starting Grant (PalM) (erc.europa.eu/funding/starting-grants), administered through the School of Geosciences, University of Edinburgh. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. SLS was funded by the European Research Council Starting Grant (PalM) (erc.europa.eu/funding/starting-grants) and the Philip Leverhulme Prize (https://www.leverhulme.ac.uk/philip-leverhulme-prizes). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. TEW was supported by National Science Foundation EAR 0207750 (www.nsf.gov/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Both TEW and SLB were supported by National Science Foundation EAR 1325544 and DEB 1654952 (www.nsf.gov/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. SLB is also supported by an European Research Council Starting Grant (PalM) (erc.europa.eu/funding/starting-grants). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.