Sea stars from Middle Jurassic lagerstätte of La Voulte-sur-Rhône (Ardèche, France)

Abstract

The Callovian Lagerstätte of La Voulte-sur-Rhône represents deep (bathyal) environments at the bottom of a submarine rocky slope. Three sea star body fossils partially replaced with pyrite were collected from clay beds. A small, stellate specimen is assigned to Terminaster cancriformis, a species already known from Jurassic clay deposits of Germany, Switzerland and England. the morphology of Terminaster illustrates mostly plesiomorphic features for post-Paleozoic sea stars, and the genus may be considered either as a paedomorphic Zoroasteridae or a stem group Forcipulatacea. Two specimens of a large multiarmed sea star are assigned to Decacuminaster n. gen. solaris n. sp., characterized by a lack of abactinal plates and an axial skeleton typical of the Velatida. the two genera Xandarodaster and Plesiastropecten are close to Decacuminaster and must be transferred to the Velatida. in modern oceans, the association of a multiarmed Velatida and a zoroasterid-like species would be typical of bathyal/abyssal environments, which suggests that these groups explored deep sea environments early in their history.