OSTEOSCLEROSIS IN THE EXTINCT CAYAOA BRUNETI (AVES, ANSERIFORMES): INSIGHTS ON BEHAVIOR AND FLIGHTLESSNESS

DE MENDOZA, R.; TAMBUSSI C.P.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2015 p. 1 - 20

0002-7014

Abstract. Many studies on avian microanatomy have established a relationship between high bone compactness (i.e., higher degree of osteosclerosis) and diving behavior. Greatest degrees of compactness have been observed in the femora and humeri of penguins, femur of Hesperornis Marsh, 1872, and of Polarornis gregorii Chatterjee, 2002, and to a somewhat lesser degree, in the humeri of flightless Pan-Alcidae. Within Anatidae, humeral and femoral compactness among diving species is greater than among non-diving species, whereas flightless diving species have a greater degree of compactness than their flying close relatives. In Cayaoa bruneti Tonni, 1979, an extinct flightless foot-propelled, diving anatid with extreme forelimb reduction, osteosclerosis is as great as that of penguins. Although osteosclerosis in the humerus of wing-propelled divers could be part of adaptations to flightlessness, osteosclerosis in the femur of both foot- and wing-propelled divers could be part of the consequences of flightlessness and which is a result of selection to counter buoyancy.