Nouvelles espèces d’Ancyrocrinus et d’Ammonicrinus , crinoïdes à pédoncule spécialisé du Dévonien armoricain (Brest, France)

New species of Ancyrocrinus and Ammonicrinus, crinoids, crinoids with specialized stem from the Armorican Devonian (Brest, France). The discovery of the oldest tetrameral grapnels of Ancyrocrinus, A. crozonensis n. sp., in the Lower Eifelian modifies considerably the previous evolutionary scheme and sets the problem of the transition from tetrameral to pentameral symmetry in the ancyrocrinid holdfasts. The presence of a new species of Ammonicrinus, A. kerdreoletensis n. sp., in the Upper Emsian suggests a North-Gondwanan origin of the genus. Its highly specialized structure of the stem, characteristic of the genus, was developed earlier than previously recognized.