Abstract
A systematic revision of the Potamotrygon motoro (Müller & Henle, 1841) species complex in the Paraná-Paraguay basin based on morphological characters was undertaken. Morphological systems analyzed include external morphology, coloration, dermal denticles, and spines, canals of the ventral lateral-line system, and skeletal components. Potamotrygon motoro is widely distributed in the Paraná-Paraguay basin and some of its diagnostic characters are: ocelli present on dorsal disc tricolored, well-defined and evenly distributed, with diameter similar or greater than eye-length; ventral coloration with relatively large whitish central region, with gray or brown area predominant on outer ventral disc margins; dermal denticles well-developed and star-shaped over central disc; labial grooves absent; monognathic heterodonty present in upper and lower jaws of adults. Potamotrygon pauckei Castex, 1963 and Potamotrygon labradori Castex, Maciel & Achenbach, 1963, are synonymized with P. motoro; Potamotrygon alba Castex, 1963, is a nomen dubium in accordance with previous authors. Additionally, two new ocellated species of Potamotrygon from the Paraná-Paraguay basin are described: Potamotrygon pantanensis, sp. nov. and Potamotrygon amandae, sp. nov. These are described and compared with P. motoro and other congeners. Potamotrygon pantanensis, sp. nov. is described from the northern Pantanal region; Potamotrygon amandae, sp. nov. is widespread in the Paraná-Paraguay basin.
Highlights
Potamotrygon motoro (Müller & Henle, 1841) is the most wide-ranging species of the family Potamotrygonidae, occurring in most freshwater systems in South America where potamotrygonids are known to inhabit, such as the Amazon, Orinoco, Paraná-Paraguay, and Uruguay basins (Garman, 1913; Rosa, 1985; Compagno & Cook, 1995; Carvalho et al., Two new species of ocellated freshwater stingrays2003; Rosa & Carvalho, 2007), as well as the Mearim system of northern Brazil (Soares, 2005)
Together with significant variation in some morphological characters between populations of different basins, and even in closely adjacent areas, has led some authors to indicate that a taxonomic subdivision of P. motoro may be necessary (Castex, 1964; Carvalho et al, 2003)
Three additional specimens from the type-series of P motoro have been reported from the ichthyological collection of the Naturhistoriches Museum Wien, Austria (Ludwig, 2009), and due to their better state of preservation provide a significant opportunity to confirm the morphological characteristics reported by Müller & Henle (1841) for P. motoro in its original description
Summary
2003; Rosa & Carvalho, 2007), as well as the Mearim system of northern Brazil (Soares, 2005). Together with significant variation in some morphological characters (e.g., dorsal disc coloration) between populations of different basins, and even in closely adjacent areas, has led some authors to indicate that a taxonomic subdivision of P. motoro may be necessary (Castex, 1964; Carvalho et al, 2003) To complicate this scenario, the original type-series of P. motoro, collected and sent to Europe by Johann Natterer in the 19th century, was originally composed of six syntypes, of which just a single juvenile specimen has been recognized as the last remaining type-specimen by most recent authors (a female specimen preserved in the Zoologisches Museum der HumboldtUniversität, Berlin; Rosa, 1985; Paepke & Schmidt, 1988; Carvalho et al, 2003). The present study anticipates the publication of a larger morphological and taxonomic revision of P. motoro in the Amazon basin (based on Loboda, 2010)
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