Osteopathology in Rhinocerotidae from 50 Million Years to the Present

PLoS One. 2016 Feb 3;11(2):e0146221. doi: 10.1371/journal.pone.0146221. eCollection 2016.

Abstract

Individual elements of many extinct and extant North American rhinocerotids display osteopathologies, particularly exostoses, abnormal textures, and joint margin porosity, that are commonly associated with localized bone trauma. When we evaluated six extinct rhinocerotid species spanning 50 million years (Ma), we found the incidence of osteopathology increases from 28% of all elements of Eocene Hyrachyus eximius to 65-80% of all elements in more derived species. The only extant species in this study, Diceros bicornis, displayed less osteopathologies (50%) than the more derived extinct taxa. To get a finer-grained picture, we scored each fossil for seven pathological indicators on a scale of 1-4. We estimated the average mass of each taxon using M1-3 length and compared mass to average pathological score for each category. We found that with increasing mass, osteopathology also significantly increases. We then ran a phylogenetically-controlled regression analysis using a time-calibrated phylogeny of our study taxa. Mass estimates were found to significantly covary with abnormal foramen shape and abnormal bone textures. This pattern in osteopathological expression may reflect a part of the complex system of adaptations in the Rhinocerotidae over millions of years, where increased mass, cursoriality, and/or increased life span are selected for, to the detriment of long-term bone health. This work has important implications for the future health of hoofed animals and humans alike.

Publication types

  • Historical Article
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Weight
  • Bone and Bones / pathology*
  • Extinction, Biological
  • Fossils / pathology*
  • History, Ancient
  • Perissodactyla* / classification

Grants and funding

This work was partially funded by the University of Oregon Museum of Natural and Cultural History and the University of Oregon Clark Honors College. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.