Two new species of freshwater stingrays of the genus Paratrygon (Chondrichthyes: Potamotrygonidae) from the Orinoco basin, with comments on the taxonomy of Paratrygon aiereba

Thiago Silva Loboda,Ricardo De Souza Rosa,Marcelo Rodrigues De Carvalho,Carlos A Lasso

doi:10.1590/1982-0224-2020-0083

Abstract

Abstract The genus Paratrygon, currently recognized as the sole monotypic genus of the family Potamotrygonidae, has a considerably greater diversity than previously indicated, including molecular studies, which supported P. aiereba (hitherto the only recognized species in the genus) as a possible species complex. Here we describe two new species of the genus that are both endemic to and sympatric in the Orinoco basin. Paratrygon aiereba, type species of the genus, is now restricted to the Amazon basin. Both new species are identified and defined through morphological characters such as coloration, dermal denticle morphology, arrangement of thorns, distribution and morphology of ventral lateral line canals, morphology of skeletal elements, and morphometrics. An extensive comparison of these characters between the new species herein described and P. aiereba is presented. Finally, a taxonomic reappraisal of P. aiereba is provided through a revision of preserved material and its original description, plus new evidence about its type-locatity, collectors, and a reconsideration of the destination of its type-specimen.

Highlights

The family Potamotrygonidae Garman, 1877 is composed of two subfamilies, five genera and 38 valid species (Carvalho et al, 2016; Silva, Loboda, 2019), with the neotropical freshwater stingrays being represented by four genera and 36 species: Paratrygon Duméril, 1865, currently monotypic, Potamotrygon Garman, 1877, the most diverse genus with 31 species, and Plesiotrygon Rosa, Castello & Thorson, 1987 and Heliotrygon Carvalho & Lovejoy, 2011 with two species each
The distribution of potamotrygonins is restricted to South American rivers that flow into the Caribbean Sea and Atlantic Ocean, with the exception of rivers located between the Parnaíba and La Plata basins and the rivers of Patagonia (Compagno, Cook, 1995; Rosa et al, 2010)
The available literature did not provide any morphological evidence that P. aiereba occurs in rivers of the Orinoco basin

Summary

Introduction

The family Potamotrygonidae Garman, 1877 is composed of two subfamilies, five genera and 38 valid species (Carvalho et al, 2016; Silva, Loboda, 2019), with the neotropical freshwater stingrays (subfamily Potamotrygoninae) being represented by four genera and 36 species: Paratrygon Duméril, 1865, currently monotypic, Potamotrygon Garman, 1877, the most diverse genus with 31 species, and Plesiotrygon Rosa, Castello & Thorson, 1987 and Heliotrygon Carvalho & Lovejoy, 2011 with two species each. In the last ten years, a series of taxonomic revisions and species descriptions based on morphological characters considerably increased our understanding of the diversity of the subfamily These works resulted in the description of 13 new species of Potamotrygon, one new species of Plesiotrygon, and one new genus, Heliotrygon with two new species (Carvalho, Lovejoy, 2011; Carvalho, Ragno, 2011; Silva, Carvalho, 2011; Carvalho et al, 2011; Loboda, Carvalho, 2013; Fontenelle et al, 2014; Carvalho, 2016a,b; Fontenelle, Carvalho, 2017; Silva, Loboda, 2019). A new subfamily was included alongside potamotrygonins in the family Potamotrygonidae: the subfamily Styracuninae ni.bio.br | scielo.br/ni

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