Famille Holopodidae von Zittel, 1879

Remarks. This family of sessile crinoids displays a morphological and functional convergence with barnacles. The aboral cup restricted to the radial circlet is fixed to the substrate by an incrusting base with parallel growth lines more or less developed. The relatively short arms curl inwards and retract into the calcinal cavity with the proximal brachials forming a protective roof at rest. Study of extant species (Améziane et al. 1999) has clarified the major characters that distinguish Holopus and Cyathidium, the only two known extant genera attributed to this family (Table 17).

Stratigraphical distribution. Late Cretaceous (Cenomanian)–Recent, possibly since Late Jurassic (Sieverts-Doreck 1951).