Euryhaliotrema n. gen. (Dactylogyridae) is proposed for species having a bulbous base of the copulatory organ. The following are described from the gills of marine and freshwater teleosts of Brazil, Peru, Venezuela and/or Mexico: Euryhaliotrema chaoi n. gen, n. sp. (type species), E. lovejoyi n. gen, n. sp., E. potamocetes n. gen, n. sp., E. thatcheri n. gen, n. sp., E. monacanthus n. gen, n. sp., and E. succedaneus n. gen, n. sp. from Plagioscion squamosissimus and Plagioscion sp. (Sciaenidae); E. atlantica n. gen, n. sp. from Paralonchurus brasiliensis (Sciaenidae); and E. sagmatum n. gen., n. sp. from Umbrina xanti (Sciaenidae). Euryhaliotrema carbunculus n. comb. (syn. Pseudohaliotrema carbunculus Hargis, 1955) from Lagodon rhomboides (Sparidae); E. bychowskyi n. comb. (syn. Haliotrema bychowskyi Obodnikova, 1976) from Hapalogenys mucronatus (Haemulidae); E. paralonchuri n. comb. (syn. Pseudohaliotrema paralonchuri Luque & Iannacone, 1989) from Paralonchurus peruanus (Sciaenidae); and E. chrysotaeniae n. comb. (syn. Haliotrema chrysotaeniae Young, 1968), E. fastigatum n. comb. (syn. Haliotrema fastigatum Zhukov, 1976), E. johni n. comb. (syn. Haliotrema johnii [Tripathi, 1959] Young, 1968), E. longibaculum n. comb. (syn. Haliotrema longibaculum Zhukov, 1976), E. lutiani n. comb. (syn. Haliotrema lutiani Yamaguti, 1953), E. paracanthi n. comb. (syn. Haliotrema paracanthi Zhukov, 1976), E. torquecirrus n. comb. (syn. Haliotrema torquecirrus Zhukov, 1976), and E. tubocirrus n. comb. (syn. Haliotrema tubocirrus Zhukov, 1976) all from species of Lutjanidae are proposed. Phylogenetic analysis of 14 species of Euryhaliotrema spp. indicates that the genus had a marine origin and that the freshwater species of Euryhaliotrema n. gen form a monophyletic clade.
Platyhelminthes, Monogenoidea, Dactylogyridae, Euryhaliotrema n. gen., Sciaenidae, Lutjanidae, Haemulidae, Sparidae, phylogeny, new genus, new species.