Gephyrotes Norman 1903

Genus Gephyrotes Norman, 1903

Revised diagnosis. Colony encrusting, unilaminar, or erect and bifurcating. Autozooids with moderately developed gymnocyst, usually visible laterally and proximally. Frontal shield formed by variable number of opposing costae, these very close to each other or separated by variable number of intercostal pores and fusing at or near zooidal midline. Peristomial and inner orifices variably shaped. Secondary orifice with elevated suboral costal complex formed by conjunction of the two most distal pairs of costae; the first (distalmost) pair raised, originating from proximolateral corners of orifice; the second pair each bifurcating, with only the more distal branch elevated and fusing in the midline with first pair of costae, the more proximal branch of the bifurcation not raised but horizontal; fusion of elevated complex variable, but often a small central lacuna as well as two larger lateral ones. Ooecium hyperstomial, subglobular, becoming immersed in distal zooid (Type A ovicell of Bishop & Househam 1987) and partially covered by extension of its gymnocyst, leaving only irregular patches exposed. Avicularia adventitious, paired, single or lacking, lateral to orifice, probably of kenozooidal origin; frequent tubular kenozooids of smooth gymnocyst around zooidal margins; occasional elongate kenozooids with reduced frontal shield. Oral spines seemingly restricted to periancestrular zooids. Basal pore chambers absent; uniporous mural septula visible in vertical walls.

Type species. Escharipora figularis forma nitido-punctata Smitt, 1868.

Remarks. The peristomial bridge-like structure composed of the fused distalmost pair of costal spines is the most typical and constant feature of the genus. A similar elevated spine complex resulting from the fusion of bifid costae has been described in some Cretaceous cribrimorph genera, i.e. Morphasmopora Lang, 1916 and Kelestoma Marsson, 1887, included by Lang (1922) in the subfamily Kelestominae together with Gephyrotes. Peristomial constructions have also been described in Tricephalopora Lang, 1916 and Phractoporella Lang, 1917 but they derive from secondary or even tertiary calcification (Taylor & McKinney 2006), not primary costal spines. Morphasmopora is also characterized by a complex serpentine pattern of kenozooids concentrated in maze-like areas as large as autozooids. In contrast, the kenozooidal network in Gephyrotes is relatively simple. Kenozooids in Kelestoma continuously surround zooidal margins and show numerous elongate openings. In Gephyrotes, kenozooid are continuous only in some species, and openings are usually less numerous and smaller. The presence of multiporous septula described by Hayward & Ryland (1998) cannot be confirmed. Communication pores are barely visible, and when present they appear of the uniporous type.

Distribution. Eocene–Recent of Europe and North America (Fig. 1).