Friday, May 6, 2016

[Ichthyology • 2016] Potamotrygon wallacei • A New Species of Neotropical Freshwater Stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the Smallest Species of Potamotrygon


Potamotrygon wallacei 
Carvalho, Rosa & Araújo, 2016 

DOI:  
10.11646/zootaxa.4107.4.5


Abstract

A new species of Potamotrygon is described from the Rio Negro drainage, Amazonas, Brazil. In spite of being cited or pictured several times in the scientific and aquarium fish literature since the 19th Century, it had been misidentified and still lacked a scientific name. Potamotrygon wallacei, n. sp., is diagnosed by the following characters: dorsal surface of disc light brown, with black irregularly-shaped vermiculate markings forming an amphora- or Ω-shaped figure on mid-disc, delimiting light brown reniform areas at disc center, and with subcircular light brown ocellate markings on disc margins; small body size (smallest known Potamotrygon species; largest examined specimen measured 310 mm DW); dorsal spines on tail usually rather low, without broad bases, in one to rarely three irregular rows, but extending posteriorly only to tail mid-length and not to caudal stings, with altogether relatively few spines; denticles on posterior mid-disc and tail base Y-shaped, with a central, anterior, bulbous cusp and usually two posterior pairs of smaller, rounded cusps; and single (anterior) angular cartilage. The new species is similar to P. orbignyi and other "reticulated" species in having a single (anterior) angular cartilage and in the color pattern of the tail, but is easily distinguished based on its size, dorsal tail spine arrangement, and specific details of color pattern.

Keywords: Potamotrygon wallacei n. sp., Myliobatiformes, morphology, systematics, taxonomy, Pisces


Potamotrygon wallacei, n. sp. live specimen resting in a tank in the Rio Itu, showing its great transparency 

Alfred Russel Wallace's illustration of the new species, Potamotrygon wallacein. sp. (modified from Wallace, 2002).
Original illustration about 12 cm long. 

Geographic distribution. Potamotrygon wallacei is endemic to the Rio Negro drainage in Amazonas, Brazil, occurring from Santa Isabel down to Rio Cuieiras in the vicinity of Manaus (Fig. 12).

Common name. The species is known as “raia cururu” in Brazil; “cururu” is a common name for the cane toad, Rhinella marina, to which the dorsum of P. wallacei bears some resemblance.

Etymology. The specific name honors Alfred Russel Wallace (1823–1913), the first naturalist to collect, observe and illustrate this species while on his travels in the Rio Negro in the early 1850's (Wallace, 2002).


FIGURE 14. Typical habitats where Potamotrygon wallacei n. sp. is common.
Upper left: Igarapé Daraquá, near the mouth of Rio Itu, left bank of the Rio Negro just above Barcelos (AM, Brazil). Upper right: typical flooded forest ("igapó") habitat (Rio Itu).
Lower left: live specimen resting in a tank in the Rio Itu, showing its great transparency. Lower right: Igarapé Cazurucu, affluent of Rio Itu. 

Marcelo R. de Carvalho, Ricardo S. Rosa and Maria Lúcia G. de Araújo. 2016. A New Species of Neotropical Freshwater Stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the Smallest Species of PotamotrygonZootaxa. 4107(4);  DOI:  10.11646/zootaxa.4107.4.5

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