Taxonomic revision of Eocene Antarctic penguins based on tarsometatarsal morphology

TLDR: Gradual cooling of climate, changes of environment and trophic relationships, that lasted several millions years, were most probably responsible for the intense speciation and taxonomic diversification of the Middle-Late Eocene La Meseta penguins.

Abstract: Eocene penguin remains from Seymour Island (Antarctica) are so far the old− est−known record of extinct Sphenisciformes. Rich Argentine and Polish collections of pen− guin bones from the La Meseta Formation are taxonomically revised on tarsometatarsal morphology. Two genera and four species are erected: Mesetaornis polaris gen. et sp. n., Marambiornis exilis gen. et sp. n., Delphinornis arctowskii sp. n. and D. gracilis sp. n. Moreover, the diagnoses of already described species: Anthropornis nordenskjoeldi, A. grandis, Palaeeudyptes klekowskii, P. gunnari, Archaeospheniscus wimani and Delphi− nornis larseni are revised as well. Gradual cooling of climate, changes of environment and trophic relationships, that lasted several millions years, were most probably responsible for the intense speciation and taxonomic diversification of the Middle-Late Eocene La Meseta penguins.