PALEOPATHOLOGY IN ARCHOSAURS FROM THE UPPER CRETACEOUS MAEVARANO FORMATION OF MADAGASCAR

The Upper Cretaceous Maevarano Formation of Madagascar has yielded a diverse archosaurian assemblage containing crocodyliforms, non-avian theropods, birds, and sauropods. Large, well-documented collections allow a faunal-level survey of skeletal paleopathology and other abnormalities. A preliminary examination of over 420 elements from 44 localities identified 36 elements with pathologies or other abnormalities. Pathologies were largely restricted to phalanges and caudal vertebrae (31 out of 36 elements). For instance, 15 out of 71 distal caudal vertebrae from two species of titanosaurian sauropod (Rapetosaurus and an unnamed taxon) exhibit abnormalities. These include bone spurs, osteophytes, and asymmetry of the vertebral centrum. In the medium-sized abelisaurid theropod Majungatholus, observed pathologies include osteophytes on pedal phalanges, a fractured and healed pedal phalanx, and caudal vertebrae with bone spurs, intervertebral fusions, and vertebral spine malformation. Observed pathologies in the small abelisauroid theropod Masiakasaurus include a caudal vertebra with a pathologic neural spine and pedal phalanges with osteophytes. In the crocodyliform Mahajangasuchus, osteophytes were identified on multiple phalanges from a single individual. The surangular from a second, unnamed crocodyliform taxon exhibited remodeling of unknown etiology, and a crocodyliform humerus of unknown affinity displayed a healed fracture. No pathologies were identified in the sample of bird specimens. The higher incidence of pathologies in distal elements such as caudal vertebrae and phalanges may reflect a greater propensity towards injury in these areas due to their vulnerable location or a collection or preservation bias towards smaller elements. The survey undertaken here provides a baseline for comparison with other paleofaunas, which may offer further information about behavior, disease, physiology, and paleoecology.