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FIGURE 1 in Potamotrygon rex, a new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the middle and upper rio Tocantins, Brazil, closely allied to Potamotrygon henlei (Castelnau, 1855)

FIGURE 1. Dorsal (A) and ventral (B) views of holotype of Potamotrygon rex, sp. nov. (adult female, MZUSP 120371, 1110 mm TL, 750 mm DL, 690 mm DW).

FIGURE 3 in Potamotrygon rex, a new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the middle and upper rio Tocantins, Brazil, closely allied to Potamotrygon henlei (Castelnau, 1855)

FIGURE 3. Dorsal (A) and ventral (B) views of Potamotrygon rex, sp. nov. (paratype, UNT 7146, 815 mm TL, 535 mm DL, 480 mm DW).

FIGURE 9 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 9. Remains of holotype of Potamotrygon schroederi (MHNLS 2504, Río Apure, Boca Apurito, Orinoco basin). A) Distal tail region with caudal stings. B) Nasoral region. C) Lateral portion of disc. Holotype was originally reported as a very large female (995 mm TL, 600 mm DL, 524 mm DW).

FIGURE 8 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 8. Río Nanay at Pampa Chica, large sandy beach along left bank of hairpin curve in river (flowing towards right), approximately 11 river km upstream from confluence with Río Amazonas and 4 km west of Iquitos center. Photo taken August 18, 2003. Large sandy beach where ANSP 182452 was collected in 2005 is largely submerged. Photograph by M. Sabaj Pérez.

FIGURE 7 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 7. Geographic distributions of Potamotrygon tigrina, n. sp. (star, type locality), and P. schroederi (circles, type locality solid) examined in this study. Base map by M. J. Weitzman.

FIGURE 3 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 3. Morphological details of holotype of Potamotrygon tigrina, n. sp. (MUSM 39978). A) Dorsal head and snout region. B) Nasoral region. C) Posterior disc and dorsal tail base region. D) Ventral view of pelvic fins. E) Posterior right side of disc, in dorsal view. F) Dorsal view of pelvic fins. Scale bars = 1 cm.

FIGURE 2 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 2. Freshly captured holotype of Potamotrygon tigrina, n. sp., in dorsal view, showing live coloration (MUSM 39978, juvenile male, Río Nanay, near Iquitos, Peru; 495 mm TL, 271 mm DL, and 258 mm DW).

FIGURE 5 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 5. Details of the skeleton and dermal covering in Potamotrygon tigrina, n. sp., from holotype (MUSM 39978, 495 mm TL, 271 mm DL, and 258 mm DW). A) Splanchnocranium and scapular region (most of gill arches removed). B) Close-up of angular cartilage. C) Base of tail region showing arrangement of dorsal spines and denticles.

FIGURE 6 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 6. Morphological details of distal tail region in Potamotrygon tigrina, n. sp., showing arrangement of dorsal tail spines, denticles, caudal stings, and vertebrae. A) MUSM 39978 (holotype; 495 mm TL, 271 mm DL, and 258 mm DW), lacking caudal stings. B) ANSP 191988 (paratype; 560 mm TL, 282 mm DL, 250 mm DW).

FIGURE 4 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 4. Paratype of Potamotrygon tigrina, n. sp. in dorsal (A) and ventral (B) views (ANSP 191988, preadult female, Peru, Departamento Loreto, Iquitos, Río Nanay; 560 mm TL, 282 mm DL, 250 mm DW; specimen dry, color faded).

FIGURE 1 in Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

FIGURE 1. Holotype of Potamotrygon tigrina, n. sp., in dorsal (A) and ventral (B) views (MUSM 39978, juvenile male, Río Nanay, near Iquitos, Peru; 495 mm TL, 271 mm DL, and 258 mm DW).

FIGURE 13 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 13. Alfred Russel Wallace's illustration of the new species, rendered between 1850 and 1852 (modified from Wallace, 2002). Original illustration about 12 cm long.

FIGURE 10 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 10. Further details of the skeleton of Potamotrygon wallacei n. sp. (UFPB 5217, female, 236 mm DW). A) Neurocranium in dorsal view. B) Lateral view of left scapula. C) Pelvic girdle showing extent of median pre-pelvic process (UFPB 6100, male 174 mm DW). D) Gill arches in dorsal view, splayed to left (dorsal elements removed from right side). Abbreviations: adf, anterodorsal fenestra; afp, anterior foramen for preorbital canal; avf, anteroventral fenestra; bb, basibranchial copula; bh, basihyal; cb: ceratobranchial (1, 5); epi, epibranchial (2); fpf, frontoparietal fontanelle; hb, hypobranchial (1); ip, iliac process; isp, ischial process; lf, lymphatic foramina; nc, nasal capsule; msc, mesocondyle; mtc, metacondyle; of, obturator foramen; paf, parietal fossa; pb, pharyngobranchial (2); pc, procondyle; pcf, precerebral fontanelle; ph, pseudohyal (ventral); pop, postorbital process; pp, prepelvic process; prp, preorbital process; pvf, posteroventral fenestra; sp, supraorbital process.

FIGURE 7 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 7. SEM photos of dorsal denticles near posterior mid-disc in Potamotrygon wallacei n. sp., showing conspicuous morphology of rounded protuberances forming a Y-shaped pattern (MZUSP 10290).

FIGURE 12 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 12. Maps showing distribution of Potamotrygon wallacei n. sp. in the Rio Negro basin (on left) and in the region near Barcelos (on right), upper Rio Negro basin, highlighting sampling efforts underway by one of us (MLG) since the mid-1990's (note that some collection localities occurred in small streams not indicated on map).

FIGURE 1 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 1. Dorsal (A) and ventral (B) views of holotype of Potamotrygon wallacei n. sp. (adult female, MZUSP 117809, 371 mm TL). Note that specimen lacks distal tip of tail and anteriormost caudal sting (smaller, posterior caudal sting shown), and that disc is slightly curled in B.

FIGURE 2 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 2. Dorsal (A) and ventral (B) views of paratype of Potamotrygon wallacei n. sp. (adult male, MZUSP 117806, 367 mm TL). Specimen was dissected to study ventral lateral-line canals (skin slightly displaced).

FIGURE 5 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 5. Dorsal view of live adult male specimen. Note large, lighter blotches on back that in many specimens coalesce to form amphora- or Ω-shaped figure, smaller spots closer to disc margins, particular coloration on eyes, and lateral darker bands on tail (photo courtesy of J.K. Langhammer).

FIGURE 11 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 11. Clasper skeleton of adult male (UFPB 5216, 345 mm TL). A) Dorsal view. B) Ventral view. Abbreviations: at, accessory terminal cartilage; ax, axial cartilage; be, beta cartilage; bp, basipterygium; bs, basal segment; dm, dorsal marginal cartilage; dt2, dorsal terminal 2 cartilage; vm, ventral marginal cartilage; vt, ventral terminal cartilage.

FIGURE 4 in A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon

FIGURE 4. Live and freshly caught specimens of Potamotrygon wallacei n. sp., showing variation in dorsal color pattern. A) From aquabr.com.br/artigos/peixes/arraia-de-agua-doce. B–E) From R. Hardwick (specimens in D are neonates; note great height of dorsal finfold in tail above specimen in E). F–G) Courtesy of N. Labbish Chao (note distinct amphora-shaped mark on disc center in G).