Bertorsonidra n. gen. (Bryozoa, Cheilostomata) for Tremopora prenanti Gautier, 1955, a rare species from the Mediterranean

The genus Bertorsonidra n. gen. is here proposed for Tremopora prenanti Gautier, 1955, a cheilostome bryozoan species from the Mediterranean area. The new description and first SEM illustration is mostly based on living material collected from infralittoral (17-19 m) bottoms off W Sicily and fossil specimens from lower Pleistocene, and possibly Pliocene, associations from three different localities in Sicily. The genus and species are characterized by a pseudoporous lepraliomorph frontal shield bordered by marginal areolae, with a prominent suboral umbo; a subcircular primary orifice with a shallow large sinus flanked by condyles, usually protected by oral spines; a prominent ovicell with an entirely exposed calcified entooecium sculptured by tubercles and pseudopores; a lateral suboral, hooked avicularium; and basal calcified pillar-like prominences for adhering to the substratum. The affinities of the genus with Robertsonidra Osburn, 1952, characterized by a frontal shield only perforated by peripheral areolae, are discussed. The erection of the new family Robertsonidridae n. fam. within the Lepraliomorpha is suggested for accommodating both Robertsonidra and Bertorsonidra n. gen. Information is given about ecological requirements of the species, persisting during time, and its morphological adaptation for colonising algal substrata, which Bertorsonidra prenanti n. comb. shares with some species of the genus Robertsonidra and other ones belonging to systematically unrelated genera.