A new species of Psephenops Grouvelle, 1898, with new distribution data and habitat notes of the psephenine water-penny beetles from Mexico (Coleoptera: Psephenidae: Psepheninae)

A new species of Psephenops is described based on specimens from Chiapas, Mexico. The new species may be separated from known Psephenops species by a combination of traits, mainly by uniformly widened parameres in dorsal view, elongated, with apex rounded, with internal margins fused at the base. First records of Belicinus rhomboideus Arce-Pérez & Shepard, 2012 and Psephenops shepardi Arce-Pérez, 2013 in Mexico are presented, while new state records of Psephenus palpalis Champion, 1913 and Psephenopalpus browni Arce-Pérez, 2004 within the country are also presented, with notes on habitat for each species; males of the latter three species are reported as collected entirely submerged utilizing a Surber sampler.

An identification key for species of Psephenops of the New World is included. The number of valid species of Psephenops now totals 16, with three species occurring in Mexico. The number of species of psephenins (Psephenidae: Psepheninae) known from Mexico increases from 10 to 13.