An outstanding fauna of marsupiate echinoids in the Pliocene of Vendée (western France)

Abstract

Abstract New investigations in the Pliocene deposits of Challans (Vendée) have allowed to collect more than 3000 marsupiate echinoids, remarkably preserved. So, apical systems, especially the marsupium of the breeding temnopleurids T. (V.) bigoti and C. bardini, have been described and figured for the first time with complete specimens. Two new marsupiate species have been described: Arbacina hugueti nov. sp., third marsupiate species of the genus Arbacina to be known in the Neogene of western France after A. emmae NÉRAUDEAU, 2003 from the Messinian of Brittany and A. pareyni ROMAN, 1983 from the Pliocene of Normandy; Tremaster romani, new species and genus of temnopleurid, characterised by an uncommon supra-ambital tuberculation, with excressences of the test surrounding scrobiculated tubercles. A third new marsupiate echinoid, Coptechinus sp. A, has been found too, but it is very difficult to know if it is a new species or a new morphotype of C. bardini. Contrarily to previous interpretations, this study points out the high diversity of western European Neogene marsupiate echinoids, a diversity comparable to the one of Australian Neogene marsupiate echinoids. However, breeding species from Australia and western Europe are clearly different and similarities exist between these two marsupiate echinofaunas at the family level only. Indeed, both in Australia and western Europe, the breeding species of echinoids mainly belong to the temnopleurid family, with the austral genus Paradoxechinus, on the one side, the north European genera Temnotrema and Coptechinus, on the other side. Moreover, the arbaciids consist of three marsupiate species of the genus Arbacina in Europe when no breeding species of this family exist in Australia. On the contrary, several breeding irregular echinoids have been found in the Australian Tertiary deposits (Spatangoids and Clypeasteroids) when not any marsupiate irregular echinoid has been discovered at present in the western Europe Neogene deposits.