The great mammalian evolutionary transitions - Insights from bone micro-anatomy

• Applicant: Dr. Eli Amson
• Subject Area: Palaeontology ; Systematics and Morphology (Zoology)
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388111938

• Final Report Year: 2021

Final Report Abstract

With this project I built a database comprising CT-scans (capturing the inner and outer structure) of skeletal elements (humerus and vertebra of the middle of the lumbar region) for almost 200 species of extant mammals. Several fossils were also successfully sampled. I devised a new methodology to assess the overall robusticity of bones. This methodology allowed to demonstrate that the body of the humerus (bone of the upper arm) of most mammals is not uniformly tubular as previously assumed, but becomes more compact proceeding distally (towards the hand). But specialised mammals have acquired modifications of their skeleton that depart from this condition, with for instance gliding and flying species who acquired a more regularly tubular and less compact structure. Taking into account all 1167 genera of extant mammals, I have estimated that transition events led to two aquatic convergences, 13 subterranean convergences, and seven aerial convergences represented by extant species. Combining both vertebral and humeral measurements in one single analysis allows to suggest that drastically different constraints can apply to bone structure in different skeletal elements.

Publications

• (2018) Bone cortical compactness in "tree sloths" reflects convergent evolution. Journal of Anatomy, 233: 580-591
  Montañez-Rivera, I., Nyakatura, J.A., Amson, E.
  
• (2018) Evolutionary adaptation to aquatic lifestyle in extinct sloths can lead to systemic alteration of bone structure. Proceedings of the Royal Society B, 285: 20180270
  Amson, E., Billet, G., Muizon, C. de
  
• (2018) Morpho-functional analysis using procrustes superimposition by static reference. Evolutionary biology, 45: 449–461
  Mielke, F., Amson, E., Nyakatura, J.A.
  
• (2018) Palaeobiological inferences based on long bone epiphyseal and diaphyseal structure - the forelimb of xenarthrans (Mammalia)
  Amson, E. & Nyakatura, J.A.
  
• (2019) Femoral morphology of sciuromorph rodents in light of scaling and locomotor ecology. Journal of Anatomy 234: 731- 747
  Wölfer, J., Amson, E., Arnold, P., Botton-Divet, L., Fabre, A.-C., H. van Heteren, A., Nyakatura, J.A.
  
• (2019) Overall bone structure as assessed by slice-by-slice profile. Evolutionary Biology 46(4): 343-348
  Amson, E.
  
• (2019) Trabecular bone architecture in the stylopod epiphyses of mustelids (Mammalia, Carnivora). Royal Society Open Science 6(10): 190938
  Amson, E., Killbourne, B.
  
• (2020). Evolution of bone cortical compactness in slow arboreal mammals. Evolution
  Alfieri, F., Nyakatura, J., and Amson, E.
  
• (2020). First evidence of convergent lifestyle signal in reptile skull roof microanatomy. BMC Biology 18:185
  Ebel, R., J. Müller, T. Ramm, C. Hipsley, and Amson, E.
  
• (2021). Humeral diaphysis structure across mammals. Evolution
  Amson, E.