Data from: Ontogeny of the Massospondylus labyrinth: implications for locomotory shifts in a basal sauropodomorph dinosaur

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 (μCT) and propagation
phase‐contrast synchrotron radiation microtomography (PPC‐SRμCT) were used
to obtain labyrinths from eight specimens, ranging from near‐hatchling 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.