A new patagonian penguin skull from the Early Miocene: taxonomic and paleobiological value.

ACOSTA HOSPITALECHE, C.

Buenos Aires

Jornada; XXVI JAPV.; 2012

No striking differences have been found between skulls of congeneric living penguin, the same pattern was assumed for fossils. MLG3400 is not a complete skull, but the preserved portion is very informative. The fossae glandulae nasales and the cristae nuchalis arerelated to the development of the nasal gland and the muscle adductor mandibulae externus respectively. The nuchal crests are attachmentpoints for the deeper neck muscles; their morphology allows inferences about habits related to diet and food catching. Theadductor mandibulae externus consists of several aponeuroses, and its three main subdivisions are involved in elevating the mandible.The pars rostralis has two origins, orbital and temporal, attached to the crista nuchalis transversa. The MLG 3400 resembles to Spheniscus urbinai Stucchi, 2002 because of the configuration of the nuchal crests, fossa glandulae nasalis, and fossa temporalis. Research based on more complete material may confirm its presence in the Patagonian Miocene. This specimen represents a starting point in the review of Miocene associations. All the currently known Patagonian fossil penguins are referred to extinct genera. MLG 3400 could represent the first specimen assigned to a modern genus in Patagonia and is interpreted as a medium-sized penguin with a primarily ichthyophagous diet. The development of the nuchal crests suggests a powerful skull mechanism for mandibular depression and upper jaw protraction. The extensive area for muscle attachment on the braincase could indicate great strength during jaw closure. This is consistent with the need for adequate force production during dives for pursuit-capture purposes