Potamotrygon boesemani, Rosa & de Carvalho & Wanderley, 2008

Rosa, Ricardo S., de Carvalho, Marcelo R. & Wanderley, Cristiane de Almeida, 2008, Potamotrygon boesemani (Chondrichthyes: Myliobatiformes: Potamotrygonidae), a new species of Neotropical freshwater stingray from Surinam, Neotropical Ichthyology 6 (1), pp. 1-1 : 1-

Potamotrygon boesemani , new species Figs. 1–6 , 8

Holotype. USNM 225574 (male, 377 mm DW), Matapi Creek , ca. 1 km from Corantijn River, Nickerie District, Surinam, 5º00’N 57º16’W, R. Vari et al., 9 Sep 1980. ( Figs. 1 , 2 ).

Paratypes. USNM 225216 (female, 153 mm DW), stream about 0.5 km inland of Camp Mataway , Nickerie District, Surinam, 4º48’N 57º43’W, Vari et al., 12 Sep 1980 ; USNM 225575 (male, 250 mm DW), Corantijn River at km 180, Nickerie District, Surinam, 5º08’N 57º18’W , R. Vari et al., 8 Sep 1980 ( Fig. 3 ) ; USNM 388849 (male [ Fig. 4 ], 413 mm DW; female [ Fig. 5 ], 427 mm DW), same data as holotype .

Non-type specimens. RMNH 26188 (two females, 275 and 364 mm DW), tributary of Kabalebo river , ca. 8 mi. below Avanavero Falls, Corantijn river drainage, Surinam ( Fig. 6 ) ; USNM 226191 (male, 128 mm DW), same data as USNM 225575 ; USNM 226192 (one male and two female embryos aborted by adult female), same data as USNM 225574 ; USNM 226193 (two females, 134 and 150 mm DW), stream on south bank of Lucie River , ca. 6 km upstream of ferry crossing on Amotopo-Camp Geol. Rd., Corantijn drainage, Nickerie District, Surinam, 3º36’N 57º37’W , R. Vari et al., 18 Sep 1980 ; USNM 226194 (male, 163 mm DW), small creek entering Corantijn river on east side approximately 300 m North of Amotopo Boat Landing, Nickerie District, Surinam, 3º33’N 57º40’W , R. Vari et al., 19 Sep 1980 .

Diagnosis. Dorsal region of disc of dark brown background coloration, with deep orange to red ocellated spots of irregular form, encircled by relatively broad black rings, in irregular concentric series, and frequently in pairs around disc center; buccal cavity dark-pigmented with orange spots in adult specimens. This species is distinguished from the ocellated congeners P. motoro (Natterer in Müller & Henle), P. henlei (Castelnau) , and P. leopoldi Castex & Castello by the more intensely colored ocelli, which are usually yellow in the latter species. From P.motoro , it is also distinguished by the darker

R. S. Rosa, M. R. de Carvalho & C. de A. Wanderley 3

dorsal background coloration, by the broader black contour of the dorsal ocelli, and by the irregular form of the ocelli as compared to the rounded shape in the latter species. From P. henlei and P. leopoldi , it is distinguished by the lack of ocelli on tail. From the tentatively identified specimen of P. ocellata (Engelhardt) , which also has dark orange ocelli, the irregular contour of the ocelli in the new species is also distinctive. The teeth are relatively smaller and in greater number (up to 45 rows in the upper jaw) than in P.motoro (23 to 32) and P. ocellata (24 in specimen 190 mm DW). The number of pectoral-fin radials (98 to 104) is also slightly higher than in P. ocellata (94).

Description. Measurements are given in Table 1 and counts in Table 2 . Disc subelliptic, disc length 1.02-1.17 times its width. Tail flattened dorsoventrally, tail length 0.9-1.3 times DW in intact specimens. Dorsal surface of disc rough in adults, with denticles more developed and concentrated on midline and anterior portion. Tail with 12-27 median dorsal spines in young specimens and 28-42 in adults, in irregular rows; tail spines relatively high, acute and less curved when compared with congeners. Tail with well-developed lateral spines in adults, shorter than dorsal spines. One or two serrated caudal stings, inserted relatively close to tail base; sting length 1.6 to 2.5 times tail width. Eyes relatively large, eye length 1.6- 2.9 in interorbital distance, 3.5-6.4 in interocular distance. Spiracle length 1.4-2.1 times eye length, 2.0- 3.4 in interspiracular distance. Mouth with five buccal papillae in all specimens; mouth width 9.2-13.6 in DW, 0.8-1.1 times internarial width. Teeth relatively small, set in quincunx, in 24 to 45 longitudinal rows in upper jaw, 24 to 43 in lower jaw, 5 to 10 exposed teeth in median row of lower jaw. Tooth rows increase in number with body size ( Fig. 7 ). Teeth sexually dimorphic, females and immature males with rhombic posterior margin, mature males with cuspidate posterior margin. Nostrils oblique to midline, nostril length 1.2-1.6 (x=1.4) in internarial distance, 2.3-2.9 (x=2.6) in prenarial distance. Branchial basket relatively broad, its greatest width at level of first pair of gill openings 3.6-4.2 in DW.

Neurocranium ( Fig. 8 ) relatively long, cranium length 26.7- 27.7% DW (x=27.3, n=5, SD=0.4). Nasal capsules anteriorly convex with a median concavity between them; cranium width at nasal capsules 17.0-18.0% DW (x=17.5, n=5, SD=0.4). Preorbital processes laterally prominent and subtriangular; cra- 4 A new species of Neotropical freshwater stingray from Surinam

R. S. Rosa, M. R. de Carvalho & C. de A. Wanderley 5

nium width at preorbital processes 18.9-21.6% DW (x=20.3, n=5, SD=1.0). Supraorbital processes short; cranium width at supraorbital processes 9.8-10.4% DW (x=10.1, n=4, SD=0.3). Postorbital processes laterally expanded and flattened; cranium width at postorbital processes 20.2-22.0% DW (x=21.2, n=3). Cranial fontanelle elongate and anteriorly broad, with slight constriction between precerebral and frontoparietal portions; fontanelle length 16.6-17.9% DW (x=17.1, n=5, SD=0.5), fontanelle width 6.6-9.2% DW (x=7.7, n=5, SD=1.1). Antorbital cartilage triangular and elongated, tapering towards posterior end ( Fig. 8b ). Upper jaws (palatoquadrates) slender and separated at symphysis. Lower jaws (Meckel’s cartilages) broad, stout and separated at symphysis; distance between lateral margins of lower jaws nearly equal to preorbital width of cranium. Hyomandibular cartilage slender and slightly arched at its anterior end. Two parallel angular cartilages at the articulation of hyomandibular cartilage and lower jaw. Claspers relatively long, clasper length in immature specimens 8.6 to 13.3 in DW, clasper length in adults 3.6-3.7 in DW.

Color in alcohol. Dorsal surface of disc with dark brown background coloration and deep orange to red ocellated spots of irregular format, surrounded by thick black rings. Black ring width usually equal to or larger than diameter of corresponding ocellus. Some ocelli with light yellow center, gradually darkening to orange towards margin. Some ocelli joined in pairs, mainly in disc center, where they are more irregularly shaped. Ocelli diminish in size towards disc margins. Dorsal surface of pelvic fins with same color as disc, bearing smaller 6 A new species of Neotropical freshwater stingray from Surinam

orange ocelli and irregular lighter spots. Ventral surface of disc medially white and laterally with broad areas pigmented in dark brown, with scattered ocellated or vermiculated spots, ranging from light yellow to orange. Ventral disc surface of adult specimens usually with one central dark spot over pectoral girdle. Embryos and young specimens with completely creamy white ventral surface. Tail dark brown dorsally, with irregular orange spots but no large ocelli beyond its base. Lateral surface of tail with alternate black bars with white spots in the interspaces. Spiracular cavity, floor and ceiling of mouth cavity pigmented with dark and orange spots in adult specimens. Holotype with dark pigment also in nasal cavity ( Fig. 2b ). The coloration of preserved specimens does not differ significantly from freshly collected material, as confirmed by color slides taken in the field shortly after capture.

Geographic Distribution. This species is known from the Corantijn river drainage, in Sipaliwini and Nickerie districts, Surinam ( Fig. 9 ) .

Etymology. The specific name honors the late Dutch biologist Marinus Boeseman (1916-2006), who contributed substantially to our knowledge of both South American ichthyology (including chondrichthyans) and zoological history.

Figures

Fig. 1. Potamotrygon boesemani. Dorsal (A) and ventral (B) views of holotype (USNM 225574, 377 mm DW), Corantijn river.

Fig. 2. Potamotrygon boesemani. Detailed view of interorbital region (A) and of mouth and nasal cavity (B) of holotype (USNM 225574, 377 mm DW).

Fig. 3. Potamotrygon boesemani. Dorsal view of paratype (USNM 225575, 250 mm DW), from Corantijn river.

Fig. 4. Potamotrygon boesemani. Dorsal (A) and ventral (B) views of paratype (USNM 388849, male, 413 mm DW), from Corantijn river.

Fig. 5. Potamotrygon boesemani. Dorsal (A) and ventral (B) views of paratype (USNM 388849, female, 427 mm DW), from Corantijn river.

Fig. 6. Potamotrygon boesemani. Dorsal views of non-type specimens (RMNH 26188), from Corantijn river: (A) 275 mm DW; (B) 364mm DW.

Fig. 8. Potamotrygon boesemani. (A) Dorsal view of neurocranium. (B) Ventral view of neurocranium and jaws, traced from radiograph (Meckel’s cartilage and palatoquadrate somewhat distorted by opened mouth) (USNM 225574, 377 mm DW). Note that antorbital cartilage has been removed from left side in B. Abbreviations: aac=anterior angular cartilage, aoc=antorbital cartilage, fpf=frontoparietal fontanelle, hyo=hyomandibula, Mc=Meckel’s cartilage, pac=posterior angular cartilage, pcf=precerebral fontanelle, pop=postorbital process, pq=palatoquadrate, prp=preorbital process, sp=supraorbital process.

Fig. 7. Number of longitudinal tooth rows in upper (a) and lower (b) jaws of Potamotrygon boesemani, relative to disc width. Adjusted straight lines of both regression functions nearly coincident.

Fig. 9. Map depicting localities of specimens of Potamotrygon boesemani. Open square is the locality of holotype (Corantijn river).