Using Geometric Morphometrics to Examine Cranial Disparity in Extinct and Extant Marsupial and Placental Carnivores

Abstract

Carnivory evolved independently in multiple mammalian lineages including Carnivora, Dasyuramorphia, and extinct Borhyaenidae, Oxyaenida and Hyaenodontida. Each lineage combines expanded attachment sites for mandibular adductors with specialized shearing dentition. Three‐dimensional geometric morphometrics were used to characterize cranial disparity in each carnivorous lineage to test for a correlation between developmental constraint in the marsupial carnivore skull and the limited morphological diversity of the group. When only extant Carnivora is included in the analysis, marsupial carnivores do occupy a separate, limited region of morphospace. When a large sample of extinct placental carnivores are included, placental morphospace and marsupial morphospace overlap. Placental Hyaenodontida, which shares with marsupial carnivores the presence of multiple carnassialized molars, unreduced dentition, long rostra, and distal temporomandibular joints, overlap extensively with marsupial carnivores. Hyaenodontidans dominated carnivore niches during early Paleogene, but were replaced by carnivorans. This analysis demonstrates the anatomical similarities between hyaenodontidans and marsupial mammals may be more significant factors in the extinction of both carnivorous lineages rather than developmental constraints affecting the cranial and functional diversity of marsupials.