South America/West Antarctica: Pacific Affinities of the Weddellian Marine/Coastal Vertebrates

Abstract

Late Cretaceous/Paleogene strata of the James Ross Basin, West Antarctica (63°S), yield the only association of marine and terrestrial vertebrates and plants known from anywhere in the continent. Fossil marine vertebrates from the extensive Cretaceous (Coniacian, Campanian and Maastrichtian) marine deposits of the James Ross Basin include marine reptiles (plesiosaurs and mosasaurs), turtles, and neoselachian and teleostean fishes. The ichthyofauna recovered from levels of the early-middle Eocene (Ypresian/Lutetian) Cucullaea I Allomember include 35 species referable to 26 families, thus making it one of the most abundant and diverse fossil marine vertebrate faunas yet recorded in southern latitudes. The diversity of the Seymour Island penguin fauna of the late Eocene (Priabonian) Submeseta Allomember indicates that this group was significantly more abundant and diverse in the Paleogene than it is today. The first significant radiation of the Weddellian penguins took place by early Eocene (Ypresian) times (basal Cucullaea I Allomember), with eight sympatric species.