The great mammalian evolutionary transitions - Insights from bone micro-anatomy
Systematics and Morphology (Zoology)
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.
(See online at https://doi.org/10.1111/joa.12873) - (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
(See online at https://doi.org/10.1098/rspb.2018.0270) - (2018) Morpho-functional analysis using procrustes superimposition by static reference. Evolutionary biology, 45: 449–461
Mielke, F., Amson, E., Nyakatura, J.A.
(See online at https://doi.org/10.1007/s11692-018-9456-9) - (2018) Palaeobiological inferences based on long bone epiphyseal and diaphyseal structure - the forelimb of xenarthrans (Mammalia)
Amson, E. & Nyakatura, J.A.
(See online at https://dx.doi.org/10.1101/318121) - (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.
(See online at https://doi.org/10.1111/joa.12980) - (2019) Overall bone structure as assessed by slice-by-slice profile. Evolutionary Biology 46(4): 343-348
Amson, E.
(See online at https://doi.org/10.1007/s11692-019-09486-6) - (2019) Trabecular bone architecture in the stylopod epiphyses of mustelids (Mammalia, Carnivora). Royal Society Open Science 6(10): 190938
Amson, E., Killbourne, B.
(See online at https://doi.org/10.1098/rsos.190938) - (2020). Evolution of bone cortical compactness in slow arboreal mammals. Evolution
Alfieri, F., Nyakatura, J., and Amson, E.
(See online at https://doi.org/10.1111/evo.14137) - (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.
(See online at https://doi.org/10.1186/s12915-020-00908-y) - (2021). Humeral diaphysis structure across mammals. Evolution
Amson, E.
(See online at https://doi.org/10.1111/evo.14170)
