The Postcranial Axial Skeleton Ofmajungasaurus Crenatissimus(theropoda: Abelisauridae) From the Late Cretaceous of Madagascar

Recent fieldwork in Upper Cretaceous terrestrial deposits in northwestern Madagascar has yielded a remarkable diversity of vertebrates, including several specimens of the abelisaurid theropod Majungasaurus crenatissimus (Depéret, 1896) Lavocat, 1955. Featured among the discoveries is an exquisite specimen (UA 8678) that preserves a virtually complete precaudal vertebral column, numerous costal elements, and portions of the skull and appendicular skeleton. This contribution represents the first description highlighting the postcranial axial skeleton of Majungasaurus. Owing to the completeness and quality of preservation, this specimen allows an examination of the serial transformation of features along the length of the axial skeleton, including a detailed analysis of postcranial pneumaticity in a nontetanuran theropod. Notable features of Majungasaurus include pneumatic cervical ribs with caudally bifurcate shafts and extensive pneumaticity of all postatlantal, precaudal vertebrae. Several postcranial features exhibited by Majungasaurus—including a well-developed cervical epipophysis, laterally expanded dorsal parapophysis, and sub-divided infradiapophyseal fossa in middle dorsal series—support previous phylogenetic studies placing it within Abelisauroidea and Abelisauridae. Majungasaurus (and abelisaurids generally) exhibit a robust cervical skeleton that features tightly interlocking cervical ribs, hyperossification of cervical rib shafts, and hypertrophied muscle attachment sites relative to other basal theropods. These features together highlight an axial core constructed to withstand high stresses, likely reflecting feeding adaptations for predation on large-bodied prey.