[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

[dinosaur] Massospondylus inner ear labyrinth ontogeny




Ben Creisler
bcreisler@gmail.com


A new paper:


James M. Neenan, Kimberley E. J. Chapelle, Vincent Fernandez & Jonah N. Choiniere (2018)
Ontogeny of the Massospondylus labyrinth: implications for locomotory shifts in a basal sauropodomorph dinosaur.
Palaeontology (advance online publication)
doi: https://doi.org/10.1111/pala.12400
https://onlinelibrary.wiley.com/doi/10.1111/pala.12400



Data archiving statement: All surface models and supplementary figures from this study are available in the Dryad Digital Repository: https://doi.org/10.5061/dryad.pj5952j.Raw scan data is stored at the Evolutionary Studies Institute, University of the Witwatersrand.


Ontogeny is a vital aspect of life history sometimes overlooked in palaeontological studies. However, the changing geometry of anatomical structures during growth can be informative regarding ecological and functional reconstructions. The inner ear, or labyrinth, is an ideal ontogenetic study system because it has a strong functional signal in its morphology that is linked to locomotor mode. Yet almost nothing is known about labyrinth development in dinosaurs. We quantified labyrinth scale and geometry through ontogeny in the Early Jurassic dinosaur Massospondylus carinatus, which has an exceptional fossil record and is hypothesized to have undergone a gait change, from quadrupedal juvenile to bipedal adult. To test whether this putative locomotor shift is reflected in labyrinth morphology, computed microtomography (ÎCT) and propagation phaseâcontrast synchrotron radiation microtomography (PPCâSRÎCT) were used to obtain labyrinths from eight specimens, ranging from nearâhatchling to adult. Labyrinths grow substantially but scale with slight negative allometry compared to skull length throughout ontogeny, the first time this has been documented in dinosaurs. Geometric morphometric analysis of the labyrinth using a sliding semilandmark approach shows some morphological change through ontogeny, but little evidence supporting a locomotor shift. These results have implications for our understanding of sauropodomorph development and provide a better understanding of dinosaur locomotory evolution.