Morphology and phylogenetic relationships of a remarkable new genus and
two new species of Neotropical freshwater stingrays from the Amazon basin (Chondrichthyes: Potamotrygonidae)
Abstract
The morphology and phylogenetic relationships of a new genus and two new species of Neotropical freshwater stingrays, family Potamotrygonidae, are investigated and described in detail. The new genus, [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon[/FONT][/FONT], n. gen., and its two new species, [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon gomesi[/FONT][/FONT], n. sp. (type-species) and [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon rosai[/FONT][/FONT], n. sp., are compared to all genera and species of potamotrygonids, based on revisions in progress. Some of the derived features of [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon [/FONT][/FONT]include its unique disc pro-portions (disc highly circular, convex anteriorly at snout region, its width and length very similar), extreme subdivision of suborbital canal (forming a complex honeycomb-like pattern anterolaterally on disc), stout and triangular pelvic girdle, extremely reduced caudal sting, basibranchial copula with very slender and acute anterior extension, and precerebral and frontoparietal fontanellae of about equal width, tapering very little posteriorly. Both new species can be distinguished by their unique color patterns: [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon gomesi [/FONT][/FONT]is uniform gray to light tan or brownish dorsally, without distinct patterns, whereas [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon rosai [/FONT][/FONT]is characterized by numerous white to creamy-white vermiculate markings over a light brown, tan or gray background color. Additional proportional characters that may further distinguish both species are also dis-cussed. Morphological descriptions are provided for dermal denticles, ventral lateral-line canals, skeleton, and cranial, hyoid and mandibular muscles of [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon[/FONT][/FONT], which clearly corroborate it as the sister group of [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Paratrygon[/FONT][/FONT]. Both genera share numerous derived features of the ventral lateral-line canals, neurocranium, scapulocoracoid, pectoral basals, clasper morphology, and specific patterns of the adductor mandibulae and spiracularis medialis muscles. [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Potamotrygon [/FONT][/FONT]and [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Ple-siotrygon [/FONT][/FONT]are demonstrated to share derived characters of their ventral lateral-line canals, in addition to the presence of angular cartilages. Our morphological phylogeny is further corroborated by a molecular phylogenetic analysis of cyto-chrome [FONT=Times New Roman,Times][FONT=Times New Roman,Times]b [/FONT][/FONT]based on four sequences (637 base pairs in length), representing two distinct haplotypes for [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon gomesi[/FONT][/FONT]. Parsimony analysis produced a single most parsimonious tree revealing [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Heliotrygon [/FONT][/FONT]and [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Paratrygon [/FONT][/FONT]as sister taxa (boot-strap proportion of 70%), which together are the sister group to a clade including [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Plesiotrygon [/FONT][/FONT]and species of [FONT=Times New Roman,Times][FONT=Times New Roman,Times]Potamotry-gon[/FONT][/FONT]. These unusual stingrays highlight that potamotrygonid diversity, both in terms of species composition and undetected morphological and molecular patterns, is still poorly known.
http://www.mapress.com/zootaxa/2011/f/z02776p048f.pdf
If anyone has the whole pdf, please let me know, I'd like it
