Ptychotrema (Gastropoda: Streptaxidae) in north-east Africa: thirteen new species from Ethiopia reveal the presence of a diverse but little-known fauna

This paper reports on the Ptychotrema fauna of Ethiopia and other countries of north-east Africa (Somalia, Eritrea, Djibouti). It describes 13 new species that were collected during two short visits to Ethiopia in 2015 and reviews and figures the other species that have been attributed to Ptychotrema from the region. It provides an identification key based on adult shell characters. The new species are assigned to subgenus Parennea (five species) or subgenus Ennea (eight species) based on apertural dentition. These subgenera are adopted for pragmatic reasons, and it is recognised that they are almost certainly artificial categories. The introduced species are Ptychotrema (Parennea) bishanwakaense sp. nov., P. (Pa.) dolfi sp. nov., P. (Pa.) wondogenetense sp. nov., P. (Pa.) keffaense sp. nov., P. (Pa.) gaysayense sp. nov. and Ptychotrema (Ennea) aethiops sp. nov., P. (E.) unumiugum sp. nov., P. (E.) harennae sp. nov., P. (E.) canaliculatum sp. nov., P. (E.) balenense sp. nov., P. (E.) epicratis sp. nov., P. (E.) wiersbowskyi sp. nov., and P. (E.) propenanum sp. nov. The identification of so many undescribed species, following such a short period of fieldwork, highlights just how poorly the Ethiopian streptaxid fauna is known. They increase the number of streptaxid species known from Ethiopia and Eritrea by about 50%, and the number of Ptychotrema reported from the “Horn of Africa” from seven to 20. The ecological and biogeographical implications are discussed.