A new miocene penguin from Patagonia and its phylogenetic relationships.

ACOSTA HOSPITALECHE, C. I. A.; TAMBUSSI, C.; DONATO, M.; COZZUOL, M

Acta Paleontológica Polónica

APP

Año: 2007 vol. 52 p. 299 - 314

We describe a new medium-size penguin (Spheniscifomes), Madrynornismirandus nov. gen. nov. sp. from the early late Miocene Puerto Madryn Formation of Chubut Province, Argentina. Although it is evident that extant and fossil penguins constitute a remarkably homogeneous family of birds, their within-group phylogenetic relationships are less obvious. In order to identify the phylogenetic position of the new taxon, we conducted a phylogenetic analysis of 20 taxa (17 representative species of all living genera and three fossil species belonging) using 44 osteological characters. The family Spheniscidae is clearly monophyletic and Madrynornis mirandus is closely related to the living taxa. Our phylogenetic interpretation is congruent also with biostratigraphic data, with Paraptenodytes from the early Miocene (about 20 Ma) located at the base of the Spheniscidae. Classically, two basic tarsometatarsal types were recognized (one for pre-Miocene and the other for the post-Miocene penguins), based on the pattern of the proximal foramina and the  hypotarsus. Madrynornis mirandus exhibits an arrangement of the proximal foramina and a degree of metatarsals fusion similar to the living forms, although its elongation index (total length/proximal width)is reminiscent of the extinct Paraptenodytes (a penguin historically recognized as a pre-Miocene form, coming from the early Miocene of Argentina). Madrynornis reveals that the two basic tarsometatarsal types co-existed among Miocene penguins.