A Tremadocian asterozoan from Tasmania and a late Llandovery edrioasteroid from Victoria

Abstract

Jell, P.A., 2014. A Tremadocian asterozoan from Tasmania and a late Llandovery edrioasteroid from Victoria. Alcheringa 38, 528–540. ISSN 0311-5518.An asterozoan, Maydena roadsidensis gen. et sp. nov., is described from the mid-Tremadocian (La1b Zone) Florentine Valley Formation in southwestern Tasmania and is the oldest known asterozoan in the world. Although only a single, largely dissociated, specimen is available, enough is preserved to recognize distinctive ambulacral plates similar to those of Archegonaster Jaekel from the Llanvirn of the Czech Republic. Reciprocodiscus transambus n. gen., n. sp. is an isorophid edrioasteroid from the uppermost late Llandovery Springfield Formation exposed in the bed of Deep Creek, near Springfield, 65 km north northwest of Melbourne. It occurs with a low-diversity trilobite fauna indicating a deepwater, subphotic environment. This edrioasteroid has in each ambulacrum a single series of floor plates that are not visible on the oral surface, indicating its isorophid affinity and retains certain apparently primitive features that are not seen in post-Cambrian edrioasteroids, such as the very large plates of the marginal circlet, plated aboral surface and ambulacral tips extending onto the marginal circlet plates.Peter A. Jell [p.jell@uq.edu.au] School of Earth Sciences, The University of Queensland, St Lucia Queensland 4072, Australia.