Trichomycterus igobi, a new catfish species from the rio Iguaçu drainage: the largest head in Trichomycteridae (Siluriformes: Trichomycteridae)

Abstract

A new species of Trichomycterus is described for the rio Iguaçu drainage in Southern Brazil. Trichomycterus igobi, new species, is readily distinguishable from all other species currently in the genus by its extremely large head (23.8-26.8 % SL), which is proportionally the largest head in any Trichomycteridae. That characteristic plus the relatively deep body result in a very short-bodied overall aspect, the most extremely such case in the genus Trichomycterus. Other diagnostic features that distinguish the new species from most or all of its congeners include a short caudal peduncle (15.4-19.7 % SL); an almost entirely cartilaginous second hypobranchial (with only vestigial ossification); a mesial expanded palatine ossification; a narrow cleithrum, falciform in shape; and the lack of a proximal posterior concavity on the third ceratobranchial. The new species seems to form a monophyletic group with T. stawiarski and other undescribed species (T. sp. C), also endemic to the rio Iguaçu. As putative synapomorphies, the three species share a rigid spine-like morphology of individual procurrent caudalfin rays, an extended area of dorsal caudal-fin procurrent rays, and numerous branchiostegal rays (ten or eleven).Uma nova espécie de Trichomycterus é descrita para a bacia do rio Iguaçu, sul do Brasil. Trichomycterus igobi, nova espécie, é facilmente distinguida das outras espécies atualmente no gênero por sua cabeça extremamente grande (23.8-26.8% SL), que é proporcionalmente a maior em Trichomycterinae e talvez em Trichomycteridae. Esta característica, em combinação com o corpo relativamente alto, resulta em um aspecto geral atacarracado que é o mais extremo no gênero Trichomycterus. Outras características que distinguem a nova espécie da maioria ou todas as outras espécies do gênero incluem o curto pedúnculo caudal (15.4-19.7 % SL); segundo hipo-branquial quase inteiramente cartilaginoso (somente com ossificação vestigial); palatino expandido medialmente; cleitro estreito, de formato falciforme; e ausência de uma concavidade posterior no terceiro ceratobranquial. A nova espécie parece formar um grupo monofilético com T. stawiarski e outra espécie não descrita (T. sp. C), também endêmicas do rio Iguaçu. Como potenciais sinapomorfias, as três espécies compartilham uma morfologia rígida dos raios procurrentes caudais, que são semelhantes a espinhos; área estendida de distribuição de raios procurrentes caudais dorsais; e raios branquiostégios numerosos (10 ou 11).

Taxonomic review of the genus Trichomycterus Valenciennes (Siluriformes: Trichomycteridae) from the laguna dos Patos system, Southern Brazil

“…In the few studies that attempted to elucidate the relationships among the species of Trichomycterus of south and southern of Brazil, Wosiacki & de Pinna (2008) recognized a monophyletic group formed by the species endemic to the rio Iguaçu basin [T. crassicaudatus Wosiacki & de Pinna, 2008; T. igobi Wosiacki &de Pinna, 2008, andT. stawiarski (Miranda Ribeiro, 1968)] based in three putative synapomorphies: the procurrent caudal-fin rays thickly ossified and rigid, the dorsal procurrent rays extend for a long portion of the caudal peduncle, stretching over the tips of at least ten neural spines, and 10-11 branchiostegal rays.…”

“…The measurements follow Tchernavin (1944) for the length of barbels, Wosiacki & de Pinna (2008) for the length and depth of the caudal peduncle and for the supraorbital pore distance, Ferrer & Malabarba (2011) for the scapular girdle and Costa (1992) for the remaining measurements.…”

A new catfish species of the genus Trichomycterus (Siluriformes: Trichomycteridae) from the río Orinoco versant of Páramo de Cruz Verde, Eastern Cordillera of Colombia

“…A few proposals of smaller putative monophyletic units within the genus (e.g., Trichomycterus brasiliensis species-group), have been recently advanced (Barbosa & Costa, 2003a;Fernández & Osinaga, 2006;Wosiacki & de Pinna, 2008), and all of these species groups are circumscribed to specific restricted geographic regions. This situation is understandable given the challenging taxonomic history of Trichomycterus, involving many species defined by brief and poorly informative descriptions, and old preserved associated type material, limiting not only the availability of complete morphological information but even the applicability of those names to any other specimen than the types.…”

Trichomycterus payaya, new catfish (Siluriformes: Trichomycteridae) from headwaters of rio Itapicuru, Bahia, Brazil

“…Most species have a limited distribution and display a high level of endemism (Eigenmann, 1918;Costa, 1992;Bockmann & Sazima, 2004). The diverse group is currently undiagnosable by synapomorphies (Wosiacki & de Pinna, 2008a).…”