Peeking back in time: Novel insights into the evolutionary relationships of diplommatinids (Caenogastropoda, Cyclophoroidea) from around Australia

Abstract

Based both on published GenBank DNA sequences and newly produced sequences, I have assembled the largest multi‐loci sequence dataset of the Diplommatinidae to date to investigate their evolutionary history. The focus of this study is on the diverse genus Palaina, which is represented by new sequences of its type species as well as additional samples from Timor and the Solomon Islands. In addition, the type species of Palmatina from Norfolk Island is also included. A relaxed molecular clock hypothesis is presented that incorporates several calibration points based on fossils or on previously published age estimates for major clades. Accordingly, the Sundaland diplommatinids Plectostoma, Opisthostoma, Arinia and Diplommatina are of considerable evolutionary antiquity, each likely having originated during the Cretaceous or early Paleogene at the latest. The Palaina sensu lato main clade was found to be the sister of all other diplommatinids included in the tree and has also diverged during the late Cretaceous. Palaina as currently delineated is rendered non‐monophyletic by the radiations of Hungerfordia and Eupalaina, which are endemic to the archipelago of Palau, as well as Palmatina from Norfolk Island.