ABSTRACT
A new subfamily (Styracurinae, subfam. nov.) and genus (Styracura, gen. nov.) are erected for Trygon schmardae Werner, 1904 (type species) and Dasyatis pacificus Beebe & Tee-Van, 1941, species placed in Himantura Müller & Henle, 1837 since 1953 but which differ significantly from it and all dasyatid genera in many morphological features. Recent molecular phylogenetic hypotheses based on the entire protein-coding mitochondrial genome have recovered Styracura as the sister group of the Neotropical freshwater stingrays (Potamotrygonidae), agreeing with previous morphological and molecular phylogenies. The Styracurinae, subfam. nov., is therefore placed in the Potamotrygonidae to reflect the current phylogenetic view. Morphological characters of phylogenetic relevance of the dermal denticles, ventral lateral-line canals, hyoid arch, cranial musculature, and pectoral and pelvic girdles are discussed and compared to other stingrays, in particular to dasyatids and potamotrygonins (now ranked as a subfamily). Inferred derived characters of Styracura and potamotrygonins require homoplasy (they are absent from Paratrygon and Heliotrygon), and ventral lateral-line canal patterns and morphology of the scapular process and pelvic girdle generally reveal an affinity to different dasyatid genera, but one most likely based on plesiomorphies or independent evolution; Styracura is considered more closely related to potamotrygonins.
Subject(s)
Skates, Fish/anatomy & histology , Skates, Fish/classification , Animals , Female , Male , Phylogeny , Species SpecificityABSTRACT
The Neotropical freshwater stingray Potamotrygom orbignyi (Castelnau, 1855), and other similar "reticulated" species occurring in northern South American basins, were submitted to a thorough taxonomic analysis based on an extensive external and internal morphological study. The identity of P. orbignyi and the taxonomic status of the related nominal species Potamotrygon dumerilii (Castelnau, 1855), Potamotrygon reticulata (Günther, 1880), and Potamotrygon humerosa Garman, 1913, are defined. Taxonomic and morphological analyses revealed that P. reticulata and P. dumerilii fall within the range of variation found in P. orbignyi and were consequently treated as junior synonyms, corroborating previous works. The extensive variation in coloration observed in P. orbignyi could not be divided into consistent morphotypes; P. orbignyi is therefore a widespread species in the upper, mid and lower Amazonas basin, the Orinoco drainage, and in rivers of Suriname and the Guianas. Additionally, P. humerosa and Potamotrygon marinae Deynat, 2007 were found to present characters that support their validity, and are redescribed based on newly collected material. Potamotrygon humerosa occurs predominantly in the mid and lower Amazonas River and in lower reaches of many of its affluents, whereas P. marinae is known only from French Guiana and Suriname. Characters that proved valuable as diagnostic indicators, either in combination or as derived features, are primarily from coloration, dermal denticles and spines (morphology, development and distribution), meristic features (e.g. numbers of tooth rows, vertebrae and mesopterygial radials), morphometric proportions (e.g. snout length, tail width at base and length), and size at sexual maturity.
Subject(s)
Elasmobranchii/anatomy & histology , Elasmobranchii/classification , Animals , Female , Male , Skeleton/anatomy & histology , Skin Pigmentation/physiology , South AmericaABSTRACT
Uma revisão taxonômica de duas espécies nominais de raias de água doce do gênero Potamotrygon previamente consideradas válidas, Potamotrygon falkneri Castex & Maciel, 1963 e Potamotrygon castexi Castello & Yagolkowski, 1969, foi realizada baseada numa análise detalhada abrangendo aspectos da morfologia externa e interna, incluindo um estudo morfométrico e merístico de espécimes provenientes da distribuição registrada dessas espécies. Além dessas espécies, o status taxonômico da espécie nominal Potamotrygon menchacai Achenbach, 1967, tratada por autores prévios como sinônimo júnior de Potamotrygon falkneri, foi avaliado. As espécies nominais que constituem o que foi chamado de complexo falkneri-castexi representam exemplos da variação cromática encontrados em uma única espécie, uma vez que ocorrem padrões intermediários de coloração e os caracteres restantes não são consistentes para separação em nível específico. Sendo assim, a espécie nominal P. falkneri é considerada válida e as espécies nominais P. castexi e P. menchacai sinônimos juniores desta. Adicionalmente, uma possível espécie nova é apresentada do río Madre de Dios no Peru, sendo esta portadora de alguns caracteres destoantes de P. falkneri. Essa espécie, conhecida de poucos indivíduos, é tratada aqui provisoriamente como Potamotrygon sp.
A taxonomic revision of two nominal species of freshwater stingrays of the genus Potamotrygon previously considered valid, Potamotrygon falkneri Castex & Maciel, 1963 and Potamotrygon castexi Castello & Yagolkowski, 1969, was conducted based on a detailed analysis of external and internal morphology, including a morphometric and meristic study of specimens from the recorded range of both species. The taxonomic status of the nominal species P. menchacai Achenbach, 1967, treated by previous authors as a junior synonym of P. falkneri, was also evaluated. These nominal species, which constitute what has been called the falkneri-castexi complex, were found to represent examples of chromatic variation present in a single species, given that intermediate patterns of coloration are common and the remaining characters analyzed are not consistent enough for separation at the specific level. Consequently, Potamotrygon falkneri is considered valid, whereas the nominal species Potamotrygon castexi and Potamotrygon menchacai are concluded to be junior synonyms of P. falkneri. Additionally, a putative new species is identified from the río Madre de Díos in Peru, which has some characters that do not correspond to P. falkneri. This species, known from few individuals, is here provisionally treated as Potamotrygon sp.
