A Revision of the Macraster species (Echinodermata, Echinoidea) occurring in the Albian deposits of the Zagros basin, Southwest Iran

The paper describes the spatangoid echinoids belonging to Macraster, which could be found in the Albian deposits (Kazhdumi Formation) at the Anneh anticline situated in Zagros Mountains, Southwest of Iran. The aim is to re-examine, and redefine three species: M. douvillei, M. longesulcatus and M. obtritus. Douvillaster and Macraster genera are synonymized and then the assignment of nominal Tethyan species belonging to the same genera is reviewed. The substantial reduction of species does not strongly impact the biodiversity patterns. Neither the bio-geographical provinciality nor the temporal trends of taxonomic richness are affected. Among the Cretaceous spatangoids, Macraster is a highly specialized taxon that displays outstanding adaptations of the ambulacra to improve in the gaseous exchanges. This, in return, triggers the higher frequency of the taxon in the warm shallow waters of the Tethyan margins, and in oxygen-depleted environments. (C) 2013 Elsevier Masson SAS. All rights reserved.