A new nigerian hunter snail species related to ennea serrata d’Ailly, 1896 (Gastropoda, Pulmonata, Streptaxidae) with notes on the west African species attributed to Parennea pilsbry, 1919

Abstract

Ennea nigeriensis sp. n. is described from southeastern Nigeria on the basis of external and internal shell morphology. Following Pilsbry’s formal criteria of a single palatal fold and corresponding external furrow, the new species may be assigned to Parennea. Ennea nigeriensis sp. n. exhibits substantial similarity with E. serrata, a species from Cameroon, in the cylindrical shell shape, crenulate suture, and internal shell morphology, indicating that the two species are closely related. CT scanning confirmed the presence of only a single palatal fold in E. nigeriensis sp. n. and two in E. serrata. In spite of this, the Nigerian species is provisionally assigned to Ennea rather than Parennea, suggesting that the characters used to define Ennea and Parennea are insufficient to delimit natural groups of species. The holotype of E. serrata is examined for the first time since its description in 1896 and a redescription of the species is provided based on the two shells hitherto known. Study of the original specimens recorded as Ptychotrema (Parennea) sulciferum by Degner from Liberia reveals these to belong to Ennea cf. thompsonae. The Nigerian shell recorded by van Bruggen as Ptychotrema (Parennea) aequatoriale proved to be a specimen of Ennea cf. perforata. As a result, no species attributable to Parennea now appear to be known in West Africa; in contrast, numerous species are known from central and eastern Africa.