Molecular phylogeny of the Hydroscaphidae (Coleoptera: Myxophaga) with description of a remarkable new lineage from the Guiana Shield

The phylogeny of the aquatic beetle family Hydroscaphidae is inferred from one mitochondrial (COI) and five nuclear (18S, 28S, wingless, arginine kinase and CAD) genes. Bayesian, maximum likelihood and maximum parsimony analyses were conducted on a combined dataset that included representatives from all three described hydroscaphid genera, three new species of the family of uncertain placement, and representatives from the myxophagan families Sphaeriusidae, Torridincolidae and Lepiceridae. All analyses strongly supported a set of nearly identical trees in which (i) the monophyly of Hydroscaphidae and all its constituent genera is affirmed, (ii) the nearly cosmopolitan genus Hydroscapha is sister to the remaining and exclusively Neotropical genera, and (iii) the new, morphologically aberrant taxa from the Guiana Shield form a monophylum separate from any described genus. Here, we review each genus of the family including the description of Confossa Short, Joly, Garcia & Maddison gen.n. to accommodate three new species: C. sculptura sp.n., C. falcata sp.n. and C. minima sp.n. The new genus possesses a remarkable perforated abdominal surface that we hypothesize serves as a respiratory plastron. We also present a key to the genera and a catalogue of species of the family.