Revision of the genus Alonopsis Sars, 1862 and its position within Aloninae (Cladocera: Anomopoda: Chydoridae)

Taxonomic status of the genus Alonopsis was clarified by the morphological study and cladistic analysis. Morphology of both valid species, A. elongata (Sars, 1861) and A. aureolata Doolitle, 1912, was investigated. So far, generic status of the group was questioned, some authors treated Alonopsis as a part of the genus Acroperus. Our data confirm independent status of Alonopsis, and emended diagnosis of the genus is provided. According to our analysis, Acroperus and Alonopsis are the sister-groups of a monophyletic clade, each having their own autapomorphies. Both genera belong to a well-defined group of Aloninae (named here as Arthrocauda-group), which is characterized by the presence of well-developed abdominal joint and elongated narrow postabdomen. There are two parallel clades within the group, one formed by Acroperus and Alonopsis, other by Parakozhowia, Kozhowia and Camptocercus. According to our analysis, these branches have numerous homoplasies, the most significant of them is the independent appearance of the head keel in two most successful genera, Acroperus and Camptocercus.