Eocene stelleroids (Echinodermata) at Seymour Island, Antarctic Peninsula

Abstract

The new asteroid species Sclerasterias zinsmeisteri (Asteriidae), Paragonaster clarkae, Tesselaster clarki (both Goniasteridae), and the new ophiuroid species Ophiura hendleri (Ophiuridae) are described from the late Eocene La Meseta Formation at Seymour Island, Antarctic Peninsula. The arm tip of an apparently new genus of the Oreasteridae is too incomplete to assign at the generic level. Other La Meseta asteroid species have been described elsewhere. Six of seven recognized stelleroid genera and all represented families survive, and differences between new species and existing congeneric species are subtle. Thus, the La Meseta fauna was similar to living faunas in basic composition.Among La Meseta asteroids, Zoroaster aff. Z. fulgens and Ctenophoraster downeyae are known from numerous specimens; fossils of the other species are comparatively uncommon and given the uncertainties of sampling, further taxa might await discovery at Seymour Island. Although the Paxillosida is known from Jurassic rocks, fasciole-bearing, semi-infaunal genera are first known from Cretaceous deposits, and Astropecten and Astropecten-like Ctenophoraster are first recorded from Cenozoic rocks. Zoroaster and Tesselaster are only known from deep water settings today, although they are found in the La Meseta. Ophiura hendleri, the only ophiuroid recognized to date from the La Meseta, occurs singly, in small groups, and in Paleozoic-type ophiuroid-rich beds.