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Vertebrae: 117-130. This species can be diagnosed from other congeners by having the following combination of features: dorsal disc with a dark brownish background, covered with beige to whitish, closely packed small spots roughly arranged in small concentric patterns, these wider toward disc margins, without ocelli; whitish spots may be closely set forming vermicular patterns; lower back portion of disc with a characteristic roughly polygonal pattern, interspersed with small light spots; rostral dermal denticles fairly simple, composed of a single central crown and star-shaped base, with central and posterior disc denticles presenting star-shaped crown ridges, mostly with anterior and lateral dichotomies; two to three irregular rows of hook-shaped spines on dorsal tail midline. This differs from other amazonian Potamotrygon species (P. motoro (Müller & Henle, 1841), P. boesemani Rosa, Carvalho & Wanderley, 2008, P. signata Garman, 1913, P. leopoldi Castex & Castello, 1970, P. henlei (Castelnau, 1855), and the doubtful Potamotrygon ocellata (Engelhardt, 1912) by lacking any form of discrete dorsal ocelli or circular or irregular spots larger than eye-diameter. This is distinguished from P. schroederi Fernandez-Yépez, 1958 and P. tigrina Carvalho, Sabaj Pérez & Lovejoy, 2011 by presenting small dorsal beige to white spots arranged in concentric patterns, slightly greater than eye-diameter, and without banded pattern of alternating yellow and dark brown bands on tail (vs. much larger spots in vivid yellow with black pigmentation pattern and evidently banded tail); from P. orbignyi (Castelnau, 1855) and P. humerosa Garman, 1913 by its characteristic dorsal color pattern composed of small spots forming whitish polygonal patterns, especially on lower back region (vs. a broad, dark reticulate pattern spread over most of disc, usually without accessory spots) and a relatively smaller head region, longer tail, and also by the lack of disc tubercles (sometimes present in latter species); from P. falkneri Castex & Maciel, 1963 and P. tatianae Silva & Carvalho, 2011 by a darker brown dorsal backgroung color, its characteristic polygonal vermicular pattern on posterior disc, and shorter tail (means of 86.3% DW vs. 93.5% DW in P. falkneri and 109% DW in P. tatianae). It differs further from P. scobina Garman, 1913 by the absence of dorsal ocelli, by a much shorter tail (means of 86.3% DW vs. 121.5% DW), by a broader tail base (means of 14.8% DW vs. 13.4% DW), and by presenting 2?3 rows of midtail spines (vs. 1?2 rows in P. scobina). In addition, apart from P. scobina, P. limai is the only species of Potamotrygon which possesses three angular cartilages (vs. one or two in all other species) (Ref. 94972). |