Body mass estimation and locomotion of the Miocene pelecaniform bird Macranhinga

The fossil darter Macranhinga paranensis (Aves: Pelecaniformes) from the la te Miocene of Argentina is the largest of all known extinct or living Anhin gidae. Its body mass is estimated at a mean value of 5.4 kg by using a scal ing model derived from the logarithmic relationship between measurements of the least shaft circumference of the femur/ tibiotarsus and body masses. P redictions of body mass, as well as the analysis of anatomical evidence, ar e used to infer that Macranhinga paranensis would have probably had a power ed flapping flight and an aquatic locomotion similar to that of cormorants. The morphology of the pelvis and the hind-limb would have allowed Macranhi nga paranensis to catch fishes by means of pursuit-diving rather than stalk ing them in an anhinga-like manner. As determined by adaptations mainly of tarsometatarsal morphology, the species had well developed perching and cli mbing abilities.