Eventually tested: Phylogenetic position of “Testechiniscus” meridionalis (Murray, 1906) (Heterotardigrada) revealed

Abstract

Tardigrade fauna of Antarctic and sub-Antarctic islands has been extensively studied from the beginning of the 20th century, which led to many species descriptions from that part of the globe. Echiniscus meridionalis, described by Murray in 1906 based on a small population found in the South Orkney Islands, is one of such species. Currently, E. meridionalis is classified as a member of the genus Testechiniscus, due to the presence of well-developed ventral plate armature. I intended to verify the affinity of this species to Testechiniscus, which has already been questioned, with the application of integrative approach to populations recently collected in the King George Island (South Shetland Islands). Consequently, I revealed that E. meridionalisstat. rev. belongs in Echiniscus, likely being an isolated phylogenetic lineage of a Southern Hemisphere/Gondwanan origin. I provided a redescription of the species and discussed its morphological oddities in comparison with other echiniscids, pinpointing to similarities between E. meridionalis and several other Echiniscus species endemic to some Southern Hemisphere localities. The study has broad implications to the classification of Diploechiniscus, Echiniscus and Testechiniscus, which were redefined accordingly. Phylogenetic positions of Testechiniscus macronyx, Echiniscus becki, E. laterosetosus, and E. polygonalis were also considered, and I concluded that the present generic assignments are wobbly. The following combinations are proposed: Diploechiniscus laterosetosuscomb. nov. and D. polygonaliscomb. nov.