The osteology of the late cretaceous paravian rahonavis ostromi from Madagascar

Abstract

Rahonavis ostromi, a paravian from the Maastrichtian Maevarano Formation, Mahajanga Basin, northwestern Madagascar, preserves morphology germane to understanding the character transformations present among paravian theropods, and in particular, among those non-avialan theropods most closely related to birds. The holotype specimen consists of a partial axial column (including cervicodorsal, dorsal, sacral, and caudal vertebrae and chevrons), most of the hind limbs and pelvis, and a partial forelimb (scapula, ulna, radius). Additional isolated elements referred to Rahonavis include distal humeri, a partial dentary, and a second right ulna; the dupli-cate right ulna demonstrates that at least two individuals of Rahonavis are present in the collection. All specimens of Rahonavis were recovered from the same level in quarry MAD 93-18 in 1995. All elements are described in detail and illustrated in multi-ple views, including CT slices of select elements to demonstrate internal morphology. Recent phylogenetic analyses place Rahonavis either within the non-avialan Unenlagi-inae, an early-diverging clade within Dromaeosauridae, or at the base of Avialae. Rahonavis is one of the best represented and preserved Gondwanan paravians, and remains a pivotal taxon for understanding the evolution and biogeography of paravians.