Potamotrygon amandae, Loboda & Carvalho, 2013

Loboda, Thiago Silva & Carvalho, Marcelo Rodrigues de, 2013, Systematic revision of the Potamotrygon motoro (Müller & Henle, 1841) species complex in the Paraná-Paraguay basin, with description of two new ocellated species (Chondrichthyes: Myliobatiformes: Potamotrygonidae), Neotropical Ichthyology 11 (4), pp. 693-737 : 723-735

Potamotrygon amandae , new species

Figs. 38-52

Potamotrygon pauckei : - Castex, 1963a: 54, 56, fig. 13, p. 56 [citation of one male specimen as legend to photograph]; - Castex, 1963c: 292 [citation of male specimen from Castex 1963a]; - Castex, 1963d: 27-28, 31, 44-46, 56 [morphological characters, toxicity, distribution]; - Castex, 1964: 30 [external morphology, coloration]; - Castex & Maciel, 1965: 7-9, 14 [distribution and occurrence in rivers around Santa Fé, Argentina]; - Castex & Yagolkowski, 1970: 3, 13-26, fig. 6, p. 24, fig. p. 25, fig. p. 26 [external morphology, dentition, denticles and spine morphology, coloration, measurements, distribution]; - Castello, 1975: 30-31 [citation of a female specimen].

Potamotrygon cf. motoro : -Graça & Pavanelli, 2007: xi, 6, 9, 13, 22, 24, 240, fig. 2, p. 24 [distribution, identification key, morphological measurements, coloration, tooth counts]. -Domingues & Marques, 2007: 157, 167-168, 173 [new species of parasite described]; -Silva & Goulart, 2007: 413-418, figs. 2-4, p. 415, fig. 5, p. 416, figs. 11-12, p. 417, fig. 14, p. 418 [morphometric data].

Potamotrygon motoro : -Lonardoni et al., 2006: 195-200, fig. 2, p. 198 [feeding habits]; -Garrone-Neto et al., 2007: 206-208, fig. 3, p. 207 [occurrence in upper Paraná River]; -Silva & Uieda, 2007: 221-225, fig. 1a, p. 222 [feeding habits]; -Lacerda et al., 2008: 115, 117, 121 [parasites]; -Garrone-Neto & Sazima, 2009a: 113-115, fig. 2, p. 115 [foraging habits]; -Garrone-Neto & Sazima, 2009b: 499- 500, fig. 1, p. 500 [foraging behavior]; -Maniglia, 2010: 6-7, 10-12, 14, 16, 19-38, fig. 1, p. 16, fig. 2, p. 20, fig. 3, p. 22, fig. 4, p. 23, fig. 5, p. 25, fig. 6, p. 26, fig. 7, p. 28, fig. 8, p. 28, fig. 9, p. 30, fig. 10, p. 31, fig. 11, p. 32, fig. 12, p. 33, fig. 13, p. 34 [molecular data].

Potamotrygon aff. motoro : -Cruz et al. 2011: 201-205, 207, fig. 2, p. 203, fig. 3, p. 204, fig. 6, p. 207 [karyotype].

Holotype. MZUSP 110910 , adult female, 341 mm DW, Paraguai River , subdistrict of Albuquerque , district of Corumbá, State of Mato Grosso do Sul, Brazil, 19º41’S 57º38’W, 11 Dec 2003, F. P. L. Marques, F. Reyda & W. Santana.

Paratypes. (12 specimens). MZUSP 110904 , adult male, 312 mm DW, Paraná River , district of Porto Primavera, State of São Paulo, Brazil, 22º47’S 52º96’ W, B. A. de Oliveira & G.C. Evagenlista, 06 Apr 2004 . MZUSP 111921 , adult female, 298 mm DW, Paraná River , subdistrict of Jupiá , district of Três Lagoas, State of Mato Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 17 Dec 2003 . MZUSP 110906 , adult female, 294 mm DW, Paraguai River , subdistrict of Albuquerque, district of Corumbá, 19º41’S 57º38’W, F. P. L. Marques, F. Reyda & W. Santana, 08 Dec 2003 . MZUSP 110909 , adult female, 290 mm DW, Paraguai River , subdistrict of Albuquerque, district of Corumbá, 19º41’S 57º38’W, F. P. L. Marques, F. Reyda & W. Santana, 10 Dec 2003 . MZUSP 110907 , adult female, 270 mm DW, Paraguai River , subdistrict of Albuquerque, district of Corumbá, 19º41’S 57º38’W, F. P. L. Marques, F. Reyda & W. Santana, 08 Dec 2003 . MZUSP 111916 , adult male, 259 mm DW, Paraná River , subdistrict of Jupiá , district of Três Lagoas, State of Mato Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 15 Dec 2003 . MZUSP 111920 , adult male, 255 mm DW, Paraná River , subdistrict of Jupiá , district of Três Lagoas, State of Mato Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 17 Dec 2003 . MZUSP 110913 , adult female, 254 mm DW, Paraguai River , subdistrict of Albuquerque, district of Corumbá, 19º41’S 57º38’W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 12 Dec 2003 . MZUSP 111919 , adult female, 236 mm DW, Paraná River , subdistrict of Jupiá , district of Três Lagoas, State of Mato Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 16 Dec 2003 . MZUSP 111917 , young male, 218 mm DW, Paraná River , subdistrict of Jupiá , district of Três Lagoas, State of Mato Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 15 Dec 2003 . MZUSP 111925 , juvenile male, 195 mm DW, Paraná River , subdistrict of Jupiá, district of Três Lagoas, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 17 Dec 2003 . MZUSP 111923 , juvenile female, 194 mm DW, same data as previous specimen .

Non-type specimens examined: Brazil. State of Mato Grosso: (22 specimens) . MZUSP 111911 , adult female, 274 mm DW, Mutum River, tributary of Cuiabá River, district of Barão de Melgaço , F. P. L. Marques & M. Cardoso, 08 Jul 2006 . MZUSP 111914 , adult male, 268 mm DW, same data as previous . MZUSP 111913 , adult male, 245 mm DW, same data as previous . MZUSP 111912 , adult male, 232 mm DW, same data as previous . MZUSP 110916 , adult female, 275 mm DW, baia Sinhá Mariana, tributary of Cuiabá River, district of Barão de Melgaço , W. J. da Graça, 22 Set 2003 . State of Mato Grosso do Sul : MZUSP 110915 , adult female, 322 mm DW, Paraguai River, subdistrict of Albuquerque, district of Corumbá , 19º41’S 57º38’W, F. P.L. Marques, F. Reyda, J. Caira & W. Santana, 13 Dec 2003 . MZUSP 110905 , adult female, 319 mm DW, Paraguai River, subdistrict of Albuquerque, district of Corumbá , 19º41’S 57º38’W, F. P. L. Marques, F. Reyda & W. Santana, 05 Dec 2003 . MZUSP 110914 , adult female, 253 mm DW, Paraguai River, subdistrict of Albuquerque, district of Corumbá , 19º41’S 57º38’W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 12 Dec 2003 . MZUSP 110912 , adult female, 227 mm DW, same data as previous . MZUSP 111918 , adult female, 254 mm DW, Paraná River, subdistrict of Jupiá, district of Três Lagoas , 20º79’S 51º 65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 16 Dec 2003 . MZUSP 111140 , adult female, 254 mm DW, Paraná River, subdistrict of Jupiá, district of Três Lagoas , 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 17 Dec 2003 . MZUSP 111926 , juvenile female, 228 mm DW, Paraná River, subdistrict of Jupiá, district of Três Lagoas , 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 18 Dec 2003 . MZUSP 111922 , juvenile female, 226 mm DW, same data as previous . MZUSP 111136 young female, 226 mm DW, Paraná River, subdistrict of Jupiá, district of Três Lagoas , 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 17 Dec 2003 . MZUSP 111924 , young female, 210 mm DW, Paraná River, subdistrict of Jupiá, district of Três Lagoas, State of Mato

Grosso do Sul, Brazil, 20º79’S 51º65’ W, F. P. L. Marques, F. Reyda, J. Caira & W. Santana, 15 Dec 2003. State of Paraná: NUP 4379 , adult female, 264 mm DW, São Francisco Verdadeiro River, tributary of Paraná River, district of Pato Bragado . NUP 4396 , adult female, 243 mm DW, same data as previous . NUP 4420 , juvenile female, 230 mm DW, São Francisco Falso River, tributary of Paraná River ,

district of Santa Helena. State of São Paulo : MZUSP 110903 , adult male, 311 mm DW, Paraná River , district of Porto Primavera, 22º47’S 52º96’ W, B.A. de Olibeira & C.G. Evangelista, 05 Apr 2004. Paraná River basin, without specific locality: MZUSP 111148 , adult male, 280 mm DW. MZUSP 111149 , adult female, 256 mm DW. MZUSP 111150 , juvenile male, 215 mm DW .

A n Range Mode

Precaudal vertebrae 36 5 36 - 49 36 Caudal vertebrae 82 4 76 - 85 - Total vertebrae 118 4 118 - - 125 Diplospondylic vertebrae 90 4 89 - 100 90 Propterygial radials 43 5 41 - 44 43 Mesopterygial radials 16 5 14 - 16 16 Metapterygial radials 33 5 31 - 36 33 Total pectoral radials 92 5 87 - 95 - Pelvic radials 21 5 17 - 24 - Tooth rows of upper jaw - 3 30 - 35 - Tooth rows of lower jaw - 3 30 - 31 31 Symphysis of upper jaw - 3 4 - 5 4 Symphysis of lower jaw - 3 4 - 5 5 Enlarged dorsal pointed-spines 33 14 32 - 77 60

Diagnosis. Potamotrygon amandae , sp. nov. differs from congeners in the Paraná-Paraguay basin, except P. motoro and P. pantanensis , due to its predominantly grayish or dark brown dorsal background color usually with bicolored ocelli on dorsal disc ( P. falkneri , P.histrix , P.schuhmacheri , and P.brachyura lack ocelli; some specimens of P. amandae , sp. nov. lack ocelli and have a uniform dark brown or gray dorsal color). A combination of characters differentiates P. amandae , sp. nov. from P. motoro and P. pantanensis : dorsal background predominantly grayish or dark brown ( P. motoro with dorsal disc background color gray, dark gray, olive, olivaceous brown, or dark brown, and P. pantanensis with dorsal disc background brown); ocelli, when present, with two colors, with a whitish, light gray or light yellow central area surrounded by a black peripheral ring ( P. motoro presents tricolored ocelli with a peripheral dark ring, yellowish or orange center and with an intermediate band, and P. pantanensis presents bicolored ocelli with a beige, orange or dark yellow central area surrounded by a peripheral black ring); ventral disc coloration grayish, covering almost all of ventral disc (ventral color predominantly whitish over central disc in P. motoro and P. pantanensis ); dermal denticles differ from P. motoro due to their smaller size and without developed coronal plates in P. amandae , sp. nov., and from P. pantanensis due to their distribution over almost entire dorsal side of disc (in P. motoro and P. pantanensis , dermal denticles do not cover almost entire dorsal disc); greater spiracular length compared to P. motoro and P. pantanensis , with mean 10.1% DW (ranging from 8.2 to 12.8% DW), whereas in P. motoro spiracular mean length is 8.0% DW (ranging from 6.7 to 9.8% DW), and in P. pantanensis mean spiraclular length is 8.7% DW (ranging from 7.6 to 9.6% DW); relatively longer tail, with tail length averaging 82.1% DW, whereas mean tail length is 78.5% DW in P. motoro and 73.4% DW in P. pantanensis ; tail relatively more slender in P. amandae , sp. nov., with mean tail width 11.0% DW (ranging from 7.2 to 13.6% DW), whereas in P. motoro and P. pantanensis mean tail width is, respectively, 13.4% DW and 13.2% DW (ranging from 10.5 to 14.8% and 11.2 to 15.5% DW, respectively); frontoparietal fontanelle of neurocranium constricted at midlength (unconstricted in P. motoro and P. pantanensis ), and postorbital process clearly more developed than in P. motoro and P. pantanensis ; anterior angular cartilage with its medial portion at articulation with Meckel’s cartilages highly curved (“J”-shaped), and much greater than posterior angular cartilage (both angular cartilages subequal in P. motoro , and P. pantanensis with anterior angular cartilage rather straight, not “J”-shaped).

Description. Proportional morphometrics and counts are presented, respectively, in Tables 5 and 6.

External morphology. Disc subcircular, longer than broad, with disc length ranging from 105.5 to 121.4% DW, similar to P. motoro . Head narrow with interorbital distance 11.5 to 16.9% DW, interspiracular distance 17.4 to 21.4% DW, and internasal distance 6.6 to 9.6% DW. Mouth narrow, its width ranging from 7.0 to 11.7% DW, and with five papillae on ventral oral epithelium (three central and two peripheral). Small, distinct rostral protuberance lacking. Eyes bulging dorsally, relatively large. Spiracles muscular, trapezoidal and large, with mean spiracular length 10.1% DW, ranging from 8.2 to 12.8% DW. Branchial basket narrow, with mean distances between first gills slits and fifth gill slits, respectively, 25.4% DW and 17.9 DW; branchial basket mean length 17.3% DW, similar to P. pantanensis . Potamotrygon amandae presents well-developed labial grooves on posterolateral corners of mouth.

Teeth in quincunx, individual teeth smaller than in P. motoro , without monognathic heterodonty ( Fig. 45 ). Contrary to P. motoro , more tooth rows present on upper jaw compared to lower jaw; tooth row count 26-37/23-33; teeth in median rows of upper and lower jaws 6-8/4-13 ( Table 6).

Pelvic fins dorsally covered by disc, with only posterior margins extending beyond disc. Pelvic fins triangular, with distal portion slightly rounded; anterior margins range between 18.6 to 27.2% DW. Clasper long and slightly curved; dorsal pseudosiphon drop-shaped ( Fig. 46 ). Clasper relatively small, with mean and range of internal length in mature adult males, respectively, 25.6% DW and 23.2 to 26.7% DW, and mean and range of external length, respectively, 12.3% DW and 10.0 to 13.9% DW ( Table 5).

110910. Mean (x) and Standard Deviation (SD) are expressed in proportions of disc width (% DW), and range is expressed in millimeters (mm) and proportions of disc width (% DW). Clasper measurements were taken only from adult specimens.

Tail long and relatively more slender in comparison with P. motoro and P. pantanensis , with range and mean of distance between cloaca and caudal extremity, respectively, 54.5 to 102.3% DW and 82.3% DW; tail width ranging from 7.2 to 13.6% DW. Dorsal and ventral tail folds relatively well-developed.

Coloration. Dorsal disc coloration somewhat variable, generally with a dark background color, and with bicolor ocelli distributed throughout entire disc ( Figs. 38a , 39a , 40a , 41a , 42a , 43a , 44a). Bicolor ocelli present a whitish rounded central region surrounded by a black peripheral ring ( Fig. 47 ). Background color on dorsal disc light gray, dark gray, light brown, or dark brown. Three patterns of dorsal disc coloration predominant in P. amandae : specimens with only ocelli, specimens with ocelli and small spots, and specimens without ocelli or spots ( Figs. 38a , 39a , 40a , 41a , 42a , 43a , 44a, 47 ). In specimens only with ocelli, most ocelli concentrated on central region of disc, their diameter greater than ocelli on disc margins, with some central ocelli reaching eye-diameter in size. Ocelli either poorly or well-defined. Ocelli with bicolor pattern generally with central region light gray, light beige or light yellow surrounded by black ring; some specimens with tricolored ocelli (with an additional intermediate brownish band). Specimens with ocelli and spots present spots more numerous on central disc, and ocelli concentrated on disc margins. Spots with vermiculate or “U” format ( Fig. 46a ). Spots and ocelli poorly or well-defined, and both composed of two bands of colors with central region whitish, light gray, light beige, beige, or dark beige or brown surrounded by a black peripheral ring. In specimens without ocelli or spots, only few indistinct, brownish spots, hidden by amandae , including the holotype (A) MZUSP 110910. Mode of enlarged dorsal pointed-spines presents two predominant values.

general backgound color, present around eyes and spiracles ( Figs. 38a , 46b ). Dorsal coloration of pelvic fins similar to dorsal disc, but less intense; number of bicolor ocelli and spots from few, near pelvic insertion, to numerous on entire surface of pelvic fin. Dorsal color of tail in specimens without ocelli and spots with uniform coloration on entire tail, from base to tip. Specimens with dorsal disc ocelli with many spots on tail. Specimens with dorsal disc ocelli and spots with many small spots on dorsal tail, alternating with darker backgound to resemble a striped pattern posterior to caudal sting. Freshly collected specimens with more intensely colored ocelli.

Ventral disc coloration with three distinct regions ( Figs. 38b , 39b , 40b , 41b , 42b , 43b , 44b). Anterocentral ventral disc and snout area predominantly whitish on most specimens (surrounding mouth and nostrils and between, and anterior to, branchial slits). Most of ventral disc, except anterocentral and marginal regions, predominantly light gray, gray, or light brown, with whitish, small rounded spots. Disc margins, usually posterior to level of mouth, predominantly dark gray, brown or dark brown, also with scattered whitish spots. Ventral color of pelvic fins with light gray, gray, or light brown background, with whitish, small rounded spots; margins of pelvic fins similar to ventral disc margins. Ventral coloration of tail with round or vermiculate whitish or light gray spots from base to tip, on a grayish or brownish background.

Squamation. Dermal denticles distributed over entire dorsal disc and tail. Central region of disc with two predominant types of dermal denticles, one larger with a star-shaped crown, and another very small with a pointed crown. Star-shaped denticles in P. amandae differ from P. motoro in presenting few developed coronal ridges and a taller and more pointed crown; pointed denticles present a pointed coronal plate surrounded by tiny pointed coronal ridges ( Fig. 48 ). Marginal region of disc with only pointed denticles with a relatively smaller diameter and only a pointed coronal plate; denticles greater in size on posterior and anterior disc. Between central and marginal disc regions, denticles with intermediate morphology between star-shaped and pointed. Denticles with pointed, trichotomous crown surrounding spiracles. Distribution, concentration and size of dermal denticles varies slightly among specimens, with some presenting more developed and concentrated denticles on dorsal disc but most with more denticles on head and anterior disc margin. Denticles with pointed crowns posterior to tail base, and relatively large near caudal sting. Dorsal row of pointed-spines on tail unique, with some specimens presenting double and even triple rows ( Fig. 49 ). Rows generally originate anterior to tail origin on disc, but in some specimens even more anteriorly. Morphology of dorsal tail spines varies slightly between specimens, with majority presenting higher, more slender and straight spines, and more curved and lower spines in others ( Fig. 49 ). Number of spines in dorsal rows varies from 11 to 70 in specimens analyzed ( Table 6). One or two lateral rows of pointed-spines on tail with spines morphologically similar to those on dorsal tail.

Ventral lateral-line canals. Description based on three adult specimens, two females (MZUSP 110916, 275 mm DW; MZUSP 111140, 254 mm DW), and one male (MZUSP 110903, 311 mm DW) ( Fig. 50 ).

Hyomandibular canal (hyc) connects with orbitonasal component of supraorbital canal (onc) anterior to nostrils, as in P. pantanensis ; orbitonasal component not as straight as in P. pantanensis , with undulations that resemble P. motoro . Number of subpleural tubules (spt) in the subpleural component of hyomandibular canal (spc) in P. amandae greater than in P. pantanensis and less than in P. motoro ; anteriormost tubules relatively more curved. Subpleural loop (spl) presents an elongate and unique posterior subpleural tubule (pst) without ramifications. Jugular component of hyomandibular canal (jch) without pronounced curve at level of branchial basket as in P. motoro , and with slight undulations close to gill basket (absent in P. motoro and P. pantanensis ). Jugular component connects anteriorly with angular component of hyomandibular canal (ach), itself connecting anteriorly with nasal canal (nas) as in P. motoro . Angular component short and straight, but little more developed than in P. pantanensis . Infraorbital canal (ioc) extends from junction with supraorbital canal (suc), as in P. motoro , and extends laterally as a broad curve, sometimes with undulations. Infraorbital canal with a straight external segment extending to anterior portion of disc, forming the infraorbital loop (iol). Suborbital component of infraorbital canal (sub) greater than in P. pantanensis and smaller than in P. motoro , and slightly undulated (straight in P. pantanensis and P. motoro ). Suborbital loop (sol) rather straight as in P. pantanensis , but more developed, and greater than infraorbital loop, not deflecting anteromedially as in P. motoro . Ascending portion of suborbital component of infraorbital canal slightly undulated, such as in P. motoro , and extends to ascending portion of subrostral component of supraorbital canal (sbr). Supraorbital canal (suc), as in P. motoro , extends from junction with infraorbital canal. Orbitonasal component of supraorbital canal (onc) with several small undulations. Prenasal loop (pnl) smaller and more narrow than in P. motoro and P. pantanensis , but nasointernal loop (nil) more broad than in P. pantanensis and P. motoro . Subrostral component of supraorbital canal (sbr) extends anteroposteriorly in parallel and closely adjacent to prenasal component of nasal canal (pnc), reaching anterior disc margin. Infraorbital canal intersects subrostral component just anterior to its midlength. As in P. motoro , nasal canal (nas) extends anteromedially from connection with final portion of hyomandibular canal; however, different from P. pantanensis and P. motoro , prenasal component of nasal canal (pnc) appears just anterior to anterior margin of nostrils on nasal curtain. Contrary to P. pantanensis and more similar to P. motoro , P. amandae presents a considerable distance between intersection of final portion of hyomandibular canal and anterior portion of nasal canal with infraorbital and supraorbital canals. Mandibular canal (mnc) as in P. pantanensis , relatively shorter and more straight than in P. motoro .

Skeletal features. Skeleton generally similar to P. pantanensis , differing principally in dorsal fontanelle size and shape from P. motoro ( Figs. 51 , 52 ). Fontanelle similar to P. pantanensis , however frontoparietal fontanelle (FPF) in P. amandae more slender, constricted at its midlength, and more oval posteriorly. Supraorbital process (SP) less developed than in P. motoro and P. pantanensis , and postorbital process (POP) greater proportionally than in P. pantanensis . Jaws similar to P. pantanensis , with the principal difference that in P. amandae the anterior angular cartilage (AAC) curved medially where it articulates to Meckel’s cartilages (MC), presenting a “J”- shape ( Fig. 51 ).

Geographic distribution. Specimens of P. amandae were collected from many localities throughout the Paraná-Paraguay basin: northern Pantanal, southern Pantanal, Paraná River at the border between São Paulo and Mato Grosso do Sul States, and along the border between Brazil (Paraná State) and Paraguay. Specimens of P. amandae examined in the Florentino Ameghino museum are from the region of Santa Fé, Argentina. The species has recently been collected in the lower Tietê River (an afluent of the Paraná River in São Paulo State; Garrone-Neto et al., 2007), a result of a recent increase in its range; its presence in the Tietê River is a consequence of the formation of the Itaipu reservoir, which previously contained the Sete Quedas waterfall system, a natural barrier impeding the presence of stingrays farther up the Paraná River ( Fig. 53 ).

Etymology. The specific name posthumously honors biologist Amanda Lucas Gimeno, who was an undergraduate colleague of the first author.

Remarks. Despite being a new species, P. amandae has been known for some time, however its similarities with P. motoro and P. histrix probably confounded authors who recognized it as a hybrid because of some of its intermediate characteristics (mainly dorsal coloration; Castex & Yagolkowski, 1970). The first author that probably studied a specimen of P. amandae was Castex (1963a, 1963c, 1963d, 1964, Castex & Maciel, 1965, Castex & Yagolkowski, 1970), albeit misidentified as P. pauckei . Some specimens (MFA 300, MFA 315 and MFA 316), identified as P. pauckei in the Florentino Ameghino museum and examined by us, are actually specimens of P. amandae . Nevertheless, the nominal species P. pauckei cannot be applied to specimens we have described as P. amandae because, as explained above (see remarks for P. motoro ), even though the type-series of P. pauckei probably originally included one specimen of P. amandae , P. pauckei is a junior synonym of P. motoro [when Castex (1964) subsequently designated one of the specimens of original type-series of P. pauckei as “ holotype ”, which counts as a lectotype designation, he fixed this nominal species to MFA 232, which is a specimen of P. motoro (Articles 74.5 e 74.6 of the ICZN; see remarks for P. motoro above)].

Some specimens of P. amandae have a dorsal disc color similar to many specimens of P. histrix . Despite ocelli being present in the former species and absent in the latter, both species share a predominantly gray background as the principal coloration on dorsal and ventral surfaces of disc, pelvic fins and tail. Other morphological features that are similar between these two species are the high concentration of dermal denticles on the center of disc, dorsal rows of enlarged and pointed spines on tail, and the morphology of these spines. However, besides the dorsal coloration usually presenting whitish ocelli (diagnostic for P. amandae ) and gray, drak gray to purple, small vermiculate spots (diagnostic for P. histrix ), morphometrics of some specimens of P. histrix helps separate these two species: mean interorbital distance (19.3% DW) and range (18.7% to 20.3% DW), mean spiracular length (4.9% DW) and range (3.5 to 5.8% DW), and mean prenasal distance (12.1% DW) and range (10.6 to 11.8% DW) are the principal distinctions; more measurements are presented in Tables 5 and 7. Futhermore, characters of P. histrix , such morphology of dermal denticles, ventral lateral-line canals, and skeletal componets show significant differences between these two species (Silveira & Carvalho, pers. obs.).

Similar to other potamotrygonid species (e.g., Potamotrygon falkneri ; Silva & Carvalho, 2011a, 2011b), P. amandae presents a variable pattern of dorsal disc coloration. Within the brown and gray patterns, the variation can be composed of ocelli, small, vermiculated marks or the total absence of specific dorsal patterns. Some of these variations are present in specimens that have been collected together in the same locations in the Paraná-Paraguay basin, and therefore cannot be applied in a consistent manner to separate putative sub-groups within P. amandae . Adult males of P. amandae also mature at relatively smaller sizes, between 20 and 35 cm DW.

Figures

Fig. 38. Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of holotype, MZUSP 110910, adult female, 341 mm DW, Paraguay River.

Fig. 39. Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of paratype, MZUSP 110904, adult male, 312 mm DW, from Paraná River.

Fig. 40. Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of paratype, MZUSP 110906, adult female, 294 mm DW, from Paraguay River.

Fig. 41. Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of paratype, MZUSP 110907, adult female, 270 mm DW, from Paraguay River.

Fig. 42. Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of paratype, MZUSP 111916, adult male, 259 mm DW, from Paraná River.

Fig. 43.Potamotrygon amandae, n. sp. Dorsal (a) and ventral (b) views of paratype, MZUSP 111919, adult female, 236 mm DW, from Paraná River.

Fig. 45. Potamotrygon amandae, n. sp. Upper and lower jaws of a non-type adult female specimen, MZUSP 110916, 275 mm DW.

Fig. 46. Potamotrygon amandae, n. sp. Dorsal view of right clasper of an adult male, MZUSP 111148, adult male, 280 mm DW.Abbreviations:ap, apopyle; cg, clasper groove; dp, dorsal pseudosiphon; hp, hypopyle; vp, ventral pseudosiphon.

Fig. 47. Patterns of ocelli and spots in specimens of P. amandae, n. sp.: (a) holotype MZUSP 110910, (b) MZUSP 110904 and (c) MZUSP 110906.

Fig. 48. Potamotrygon amandae, n. sp. Detail of dermal denticles present in a non-type juvenile male specimen, MZUSP 111150, 215 mm DW, showing the two morphological types of denticles, with star-shaped and pointed crowns.

Fig. 49. Potamotrygon amandae, n. sp. MZUSP 111148: (a) Dorsal view of tail showing the entire dorsal rows of enlarged pointed spines, (b) showing the rows and format of pointed spines, and (c) detail of some pointed spines of dorsal rows.

Fig. 50. Potamotrygon amandae, n. sp. Ventral canals of lateral line system in a non-type adult female specimen, MZUSP 111140, 254 mm DW. Abbreviations: hyc, hyomandibular canal; ioc, infraorbital canal; mnc, mandibular canal; nas, nasal canal; suc, supraorbital canal; ach, angular component of hyomandibular canal; iol, infraorbital loop; jch, jugular component of hyomandibular canal; nil, nasointernal loop; onc, orbitonasal component of supraorbital canal; pnc, prenasal component of nasal canal; pnl, prenasal loop; pst, posterior subpleural tubule; sbr, subrostral component of supraorbital canal; sol, suborbital loop; spc, subpleural component of hyomandibular canal; spl, subpleural loop; spt, subpleural tubules; sub, suborbital component of infraorbital canal.

Fig. 51. Potamotrygon amandae, n. sp. Dorsal and ventral views of neurocranium and mandibular arch (in ventral view) of a non-type adult male specimen, MZUSP 111148, 280 mm DW. Abbreviations: AAC, anterior angular cartilage; CL, calcified ligament; DLP, dorsolateral process; EPB, epiphysial bar; 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. 52. Potamotrygon amandae, n. sp. Anatomical details from radiograph of holotype, MZUSP 110910. Abbreviations: AAC, anterior angular cartilage; PAC, posterior angular cartilage.

Fig. 53. Distribution of Potamotrygon amandae, n. sp. in the Paraná-Paraguay system. Red circles show localities where specimens of P. amandae were obtained for this study. Red star indicates Paraguay River, type locality of P. amandae.