Taxonomic revision and phylogeny of the genus Cetiocyon and its discovery in the Neotropical region (Insecta: Coleoptera: Hydrophilidae)

The hydrophilid genus Cetiocyon Hansen (Sphaeridiinae: Megasternini) is diagnosed and revised, resulting in the fi rst record of the genus in the Neotropical Region and recognition of eight species in New Guinea. One new species, Cetiocyon incantatus new species, is described from Suriname, and four new species from the central mountain range of New Guinea: Cetiocyon cribripunctatus new species, Cetiocyon hebaueri new species, Cetiocyon riedeli new species, and Cetiocyon traipela new species. Four previously described species are redescribed: Cetiocyon goliathus (Huijbregts, 1984), Cetiocyon hanseni Hebauer, 2001, Cetiocyon loksai Hebauer, 2001, and Cetiocyon papuensis (d'Orchymont, 1924). An identifi cation key is included for all recognized species, along with photographs and illustrations of relevant morphological characters. A phylogenetic analysis based on 34 morphological characters supports the monophyly of the genus and its Australian – New Guinean origin, and suggests its close relationships to the New Guinean genus Platycyon Hansen and New Guinean species of Pelosoma Mulsant. Three distinctive lineages have been recognized within Cetiocyon, two represented by New Guinean species, the third by the Neotropical one. Possible reasons for the disjunct distribution of the genus are discussed, along with remarks about the composition of the Megasternini fauna in New Guinea.