Cochlostoma bicostulatum Gofas, 1989

Gofas, Serge, 2001, The systematics of Pyrenean and Cantabrian Cochlostoma (Gastropoda, Cyclophoroidea) revisited, Journal of Natural History 35 (9), pp. 1277-1369 : 1317-1319

Cochlostoma bicostulatum Gofas, 1989

(®gures 31±34)

Cochlostoma bicostulatum Gofas, 1989: 45 ±46, ®gure 6±9. Type locality: Seldesuto, near Matienzo (Santander)ÐHOLOTYPE MNHN. PARATYPES MNHN, MNCN, MZB, UPV .

Manuscript names in Museum collections:

Pomatias bicostulatum Aguiar-Amat `des®ladero de Beyos, Asturias, D. Quatrecasas leg. et det.’ MZB 80.0047.

Cochlostoma azpeitianum Ortiz de Zarate in coll. Altimira (®de Raven, 1990).

Cochlostoma cantabricum Raven in coll. UPV.

Description

Shell up to 12.5 Ö 5 mm with 7.5 to 8.5 quite rounded whorls. Early whorls with a peripheral angle which is slightly apparent next to it; body whorl de®nitely constricted, well rounded.

Sculpture of weak wrinkles on the ®rst embryonic half whorl, then grading to crowded (25±30/mm) ribs on the second whorl. Spire whorls with alternating very strong ribs (9±11 ribs/mm) with 1± 4 ®ner ones; ribs de®nitely thickened at their termination along the suture, so as to give it a crenulated aspect.

Aperture strongly thickened and expanded into a collar, with a very distinct rim forming a sharp angle inside the outer lip. Peristome distinctly auriculated, gradually narrowing at the columellar insertion; collar usually contained in a plane, not distorted.

Shell colour of a uniform pale brown to tan. Peristome white.

Female and male genital systems as in general description.

Remarks

This species is easily recognized by its pattern of alternating strong and thin ribs. Cochlostoma asturicum , which is found sympatrically in the Picos de Europa area, is similar in general shape and size, but has equal ribs and a darker shell colour.

Several characters are shared with the eastern Pyrenean species C. nouleti : the alternating sculpture, the wrinkled pattern on the very early part of the spire, the de®nite inner rim of the aperture, and among the allozymic characters the SOD and MPI patterns.

Habitat

Among limestone, mostly among mounds of loose large stones in shaded places. The partitioning of the habitat is clearcut where the species is sympatric with C. hidalgoi ; the latter living higher on exposed surfaces (®gure 34). Cochlostoma bicostulatum is more ubiquitous and sometimes very abundant in the coastal area, where it is often found alone.

Distribution

The coastal areas of the Basque country, Cantabrian range and Asturias. This species is predominant at lower altitudes, and can be found only a few metres away from the maritime splash zone if limestone is present.