Chatar & al Ontogeny Smilodon
Project
ID: 000599525
Public
Chatar N, Boman R, Fischer V, Segura V, Julémont C & Tseng ZJ. Growing sabers: Mandibular shape and biomechanical performance trajectories during the ontogeny of Smilodon fatalis. The Anatomical Record (Under review) Evolution of organisms can be studied through the lens of developmental systems as the timing of development of morphological features is an important aspect to consider when studying a phenotype. This enterprise is notoriously difficult in fossil amniotes due to the scarcity of the fossil record. However, the numerous remains of Rancho La Brea allow a detailed study of the post-natal changes in an extinct sabertoothed felid: Smilodon fatalis. While different aspects of the ontogeny of Smilodon have already been studied, an important question remained open: how did the cubs of Smilodon acquired and process food? We used 3D geometric morphometric and finite element analysis to quantify both mandibular shape and performance during growth of Smilodon fatalis and the extent lion, Panthera leo. Using a total of 49 mandibles (22 belonging to Smilodon fatalis and 23 belonging to Panthera leo at different stages of developments), we observed a clear shift in mandibular shape in both lion and sabertooths growth sequences coinciding approximately with the eruption of the lower carnassial. The eruption of this tooth signifies the end of the weaning period in extant lionsand implies a longer weaning in S. fatalis given its delayed eruption sequence. We also highlight distinct ontogenetic trajectories, with S. fatalis undergoing more post-natal mandibular shape changes than P. leo. Finally, although S. fatalis appears to be more efficient than P. leo to perform an anchor bite, this efficiency is acquired through ontogeny and at a quite late age .