Biconcavus, Figuerola & Gordon & Cristobo, 2018

Figuerola, Blanca, Gordon, Dennis P. & Cristobo, Javier, 2018, New deep Cheilostomata (Bryozoa) species from the Southwestern Atlantic: shedding light in the dark, Zootaxa 4375 (2), pp. 211-249 : 221

Biconcavus n. gen.

Type species. Biconcavus batmani n. sp. (SEE DESCRIPTION bELOW).

Etymology. LATIN ‘ cΟncaνus ’, CONCAVE, ALLUDINg TO THE bILATERALLY CONCAVE OPERCULAR MARgIN.

Diagnosis. COLONY ENCRUSTINg, MULTISERIAL. AUTOZOOIDS WITH ELEVATED, TUbERCULAR DISTAL MARgIN. UMbONULOID SHIELD DENSELY gRANULAR, FRONTALLY IMPERFORATE, WITH NUMEROUS, SMALL, DISTOLATERAL PERFORATIONS LIKELY TO bE PSEUDOPORES OUTSIDE THE bOUNDARY OF THE UMbONULOID FRONTAL SHIELD AND/OR MARgINAL AREOLAR OPENINgS. OPERCULUM WITH bICONCAVE LATERAL MARgINS. ORIFICE SUbqUADRATE, PROXIMAL AND DISTAL bORDERS STRAIgHT. NO ORAL SPINES OR LYRULA. AVICULARIA, OVICELLS AND ANCESTRULA NOT SEEN.

Remarks. OWINg TO THE PAUCITY OF MATERIAL AND THE AbSENCE OF AVICULARIA AND OVICELLS, IT IS HARD TO PLACE THIS TAXON WITHIN A FAMILY. THE LARgE SIZE OF THE AUTOZOOIDS, THE COARSELY gRANULAR FRONTALLY IMPERFORATE CALCIFICATION, AND THE DISTAL ORIFICIAL TUbERCLES ARE REMINISCENT OF AspidΟstΟma cΟrΟnatum (THORNELY, 1924). THE bILATERALLY bICONCAVE OPERCULAR MARgIN AND THE LARgE NUMbER OF DISTOLATERAL PORES, WOULD SEEM TO PRECLUDE ACCOMMODATION IN AspidΟstΟma OR ASPIDOSTOMATIDAE , HOWEVER. THERE ARE NO INTERNAL SUbORIFICIAL RIDgES, LIKE THOSE IN A. cΟrΟnatum, WHICH WOULD CORRESPOND TO OPESIULAR CHANNELS FOR ACCOMMODATION OF MUSCLES.

ON THE OTHER HAND, THIS NEW SPECIES MAY bE COMPARED TO Escharella mamillata HAYWARD & THORPE, 1989, WHICH HAS A SIMILAR FRONTAL SHIELD AND NO ARTICULATED ORAL SPINES IN ZOOIDS bEYOND THE gROWINg MARgIN. THE AbSENCE OF A LYRULA, HOWEVER, WOULD SEEM TO PRECLUDE ACCOMMODATION IN Escharella . FOR THESE REASONS, A NEW gENUS IS INTRODUCED HERE TO ACCOMMODATE THIS UNUSUAL NEW SPECIES.