Taxonomy and morphology of three species of Psammobatis distributed in the Southwestern Atlantic Ocean (Rajiformes: Arhynchobatidae) with notes on intraspecific variation

Abstract

The genus Psammobatis is currently composed of seven valid species and four of these are known to occur along the southeastern and southern coasts of Brazil (P. bergi, P. extenta, P. lentiginosa, and P. rutrum). The differentiation among the last three species is still problematic since identification keys and species description are ambiguous and do not consider the influence of secondary sexual dimorphism and ontogenetic variation on morphological characters. This study aimed to investigate the external and internal morphology of P. extenta, P. lentiginosa, and P. rutrum, redescribing these species and illustrating characters useful to their distinction. Coloration pattern, dermal denticles, neurocranium and clasper morphology, disc shape, morphometric and meristic data were analyzed. The morphometric data showed 10 significant measurements to distinguish P. lentiginosa from P. extenta and 12 measurements to distinguish it from P. rutrum. For P. extenta and P. rutrum, six measurements with significant differences were observed, concentrated in disc and snout regions, and eye diameter. Psammobatis rutrum and P. lentiginosa are distinguished by their tail region, snout shape and mouth. Evidence of sexual dimorphism was observed in the three species regarding measurements related to head and disc shape. Lastly, an identification key is provided to the Brazilian species of Psammobatis.