Systematic revision of the recent species of Peasiella Nevill, 1885 (Gastropoda: Littorinidae), with notes on the fossil species

Abstract

Peasiella is a genus of the Littorinidae, whose members have minute, trochoidal shells, and are found on rocky shores in the Indo-Pacific region. Six Recent species [P. tantilla (Gould, 1849), P. conoidalis (Pease, 1868), P. roepstorffiana (Nevill, 1885), P. lutulenta sp. nov., P. isseli (Semper in Issel, 1869) and P. infracostata (Issel, 1869)] are recognized herein, one of which is described as new. Shell characters are highly variable, but usually adequate for identification, and provide characters for a key. The reproductive anatomy, paraspermatic nurse cell, egg capsule, head-foot, and radula are described. Distribution maps are provided, and the species can be classified as oceanic, continental, or intermediate, according to their distribution and habitat. Within the subfamily Littorininae the phylogenetic relationships of Peasiella are uncertain. Fossils are known from France and New Zealand, and the earliest from the Middle Eocene. Four fossil species [P. minuta (Deshayes, 1824), P. reyti (Cossmann et Peyrot, 1917), P. pontileviensis (Morgan, 1915) and P. aff. roepstorffiana (Nevill, 1895)] are briefly described, but the account is probably not complete, because fossils may have been misclassified in other families