RECONSTRUCTING THE ONTOGENY OF THE SAUROPODOMORPH MUSSAURUS AND IMPLICATIONS FOR LOCOMOTION

ANDREW CUFF; ALEJANDRO OTERO; LAUREN SUMNER; DIEGO POL; JOHN HUTCHINSON

Congreso; 78 Annual Meeting of the Society of Vertebrate Paleontology; 2018

Mussaurus patagonicus is a sauropodomorph from the Early Jurassic of Argentina,originally described from hatchling remains. Further discoveries of juvenile and maturespecimens provide a sufficiently complete series to reconstruct general patterns ofontogeny. Here, one each of a hatchling, juvenile (~1 year old), and adult (8+ years old)individual was studied. Digital models of the bones were created for each specimen, fromsegmented μ-CT scans for the smaller bones and photogrammetry and laser scans for thelarger bones. Modeled bones were then articulated to produce complete skeletons, withmissing bones being replaced by scaled versions of adults or closely related taxa. Eachskeleton was wrapped in convex hulls or more anatomically realistic shapes, which wereused to estimate body mass and center of mass, and to conduct sensitivity analyses of thesecalculations. Both methods show consistent results that Mussaurus rapidly grew from about60 g at hatching, to ~7 kg at one year old, and reaching ~1430 kg at adulthood. During thistime, the body?s center of mass moved from a position in the mid-thorax to a more caudalposition nearer the pelvis, consistent with a shift from quadrupedalism to bipedalism thatmight have occurred early in ontogeny in Mussaurus and other early sauropodomorphs.Our findings offer important new insights into the evolution of locomotion acrossSauropodomorpha, consistent with a heterochronic shift to quadrupedalism nearSauropoda.