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.SAM/PK/1314 right endosseous labyrinthSurface file of the right labyrinth from SAM/PK/13141314 right .plyBP/1/4779 left endosseous labyrinthSurface file of the left labyrinth from BP/1/47794779 left.plyBP/1/4930 left endosseous labyrinthSurface file of the left labyrinth from BP/1/49304930 left.plyBP/1/4934 left endosseous labyrinthSurface file of the left labyrinth from BP/1/49344934 left.plyBP/1/4998 left endosseous labyrinthSurface file of the left labyrinth from BP/1/49984998 left.plyBP/1/5231 left endosseous labyrinthSurface file of the left labyrinth from BP/1/52315231 left.plyBP/1/5241 right endosseous labyrinthSurface file of the right labyrinth from BP/1/52415241 right.plySAM/PK/7904 left endosseous labyrinthSurface file of the left labyrinth from SAM/PK/79047904 left.plySupplementary Figure S1The landmarking method employed in this study. A, semilandmarks are placed along the exterior and interior margins of each semicircular canal, additionally capturing the geometries of the crus communis as well as the anterior and lateral ampullae. B, semilandmark sequences are resampled in R to 14 equally-spaced points along each margin.Figure S1.jpgSupplementary Figure S2FIG. S2. Extreme shapes from PC axes overlain to demonstrate geometry change in lateral (left), dorsal (middle) and posterior (right) views. A, PC1. Negative values are in green and positive values in red. B, PC2, the axis that shows ontogenetic shape change. Colour scheme follows figure 3, with negative values in dark blue and positive values in light blue. C, PC3. Colour scheme follows A.Figure S2.jp