DOI: 10.5061/dryad.pj5952j
title: Data from: Ontogeny of the Massospondylus labyrinth: implications for locomotory shifts in a basal sauropodomorph dinosaur

description: 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.
description: 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.jpg