An unusual new ophiuroid (Echinodermata) from the Late Ordovician (early Katian) of Morocco

International audience ; A distinctive new genus and species of the subphylum Asterozoa, Componaster spurius n. gen., n. sp., is described from the Late Ordovician (early Katian) of Morocco. Construction of the ambulacral column is considered key to delineation of classes of the subphylum Asterozoa: morphology and configuration of the mouth frame, axial (ambulacral series), and adaxial (lateral series) enable class-level assignment of C. spurius n. gen., n. sp. to the Ophiuroidea Gray, 1840. However, overall form and aspects of extraxial skeletal expression from beyond the ambulacral column are strongly reminiscent of expressions of the Asteroidea de Blainville, 1830. The character complex of C. spurius n. gen., n. sp. precludes its alignment with any available ophiuran ordinal concept, and available data do not justify proposal of new ordinal terminology: the species is left incertae sedis at the ordinal level but a new familial taxon, Componasteridae n. fam., is recognized. Although Late Ordovician, the complex morphology of Componaster spurius n. gen., n. sp. suggests either plesiomorphic expressions from asterozoan diversification surviving until the Katian or significant homoplasy during early ­asterozoan history.