Paratrygon aiereba (Müller & Henle, 1841)

Loboda, Thiago Silva, Lasso, Carlos A., Rosa, Ricardo de Souza & Carvalho, Marcelo Rodrigues de, 2021, Two new species of freshwater stingrays of the genus Paratrygon (Chondrichthyes: Potamotrygonidae) from the Orinoco basin, with comments on the taxonomy of Paratrygon aiereba, Neotropical Ichthyology (e 200083) 19 (2), pp. 1-80 : 40-67

Paratrygon aiereba (Müller & Henle, 1841)

( Figs. 33‒58 ; Tabs. 5‒6)

Trygon aiereba Müller & Henle, 1841:160 , 196 [original description, not figured, type locality: ‘ Brasilien’ [= Brazil]; one type specimen originally deposited in the Zoologische Staatssammlung München (“ Ein Exemplar im zoologischen Museum zu München ”, p. 196), presently considered lost].

Trygon (Paratrygon) aiereba . — Duméril, 1865:594‒595 [synonymy, description, distribution].

Disceus strongylopterus [sic]. —Garman, 1877:208‒209 [synonymy, description, distribution in Belém, Manaus and Óbidos (Brazilian locations)].

Paratrygon strongylopterus [sic]. — Jordan, 1887:557 [citation]. —Eigenmann, Eigenmann, 1891:24 [citation, distribution]. —Eigenmann, 1910:378 [synonymy, distribution].

Paratrygon orbicularis . —Eigenmann, 1912:118 [synonymy, brief description; note that Raja orbicularis Bloch, Schneider, 1801 is based on the “ Aiereba ” of Marcgrav, 1648, intended for a marine stingray and considered a nomen dubium by Rosa, 1991].

Elipesurus strogylopterus . — Garman, 1913:425‒426 [synonymy, description]. —Fowler, 1951:4‒5 [synonymy, distribution].

Disceus thayeri Garman, 1913:426‒427 , plates 34, 54 (fig. 2), 57 (fig. 2), 70 (fig. 3) [synonymy, original description, distribution in Belém, Manaus, Óbidos and rio Juruá ; type locality: Amazon (in the following localions: Manaus , Óbidos and Belém [“ Para ”]) and Juruá rivers; type specimens (syntypes): MCZ 563 -S (female, from Belém), MCZ 297 -S (female, from Manaus) and MCZ 606 -S (male, from Óbidos)]. —Fowler, 1951:10, fig. 4 [synonymy, distribution]. —Castex, 1964:33‒34 [brief description, distribution].

Potamotrygon strongylopterus . —Castex, 1964:22 [synonymy, brief description, distribution].

Disceus strogylopterus . —Castex & Castello, 1969:21, 22, 24, 26‒29 [taxonomic discussion, description, distribution].

Paratrygon aiereba . —Rosa, 1985a:363‒372, 365‒394, 405‒407, 413‒431, 433‒434, 437‒438, 454, 460‒462, figs. 87‒96, fig. 97b, fig. 99, [synonymy, diagnosis, taxonomic discussion, description, distribution, phylogenetic analysis]. —Taniuchi, Ishihara, 1990:10‒12, 14‒15, fig. 1 [morphological description of clasper]. —Rosa, 1991:425‒430, 433‒435, figs. 1‒2, fig. 5 [synonymy, description, taxonomic discussion, distribution]. —Compagno, Cook, 1995:72‒73, 80‒81 [distribution]. — Lovejoy, 1996:214‒217, 219‒221, 224‒225, 227‒230, 234, 236‒237, 240‒246, 249, fig. 4c, figs. 6e, 6f, fig. 8d, fig. 9d, fig. 10c, fig. 11f, figs. 15‒16 [morphological description, analysis, phylogenetic discussion]. —Carvalho et al., 2003:22‒23 [synonymy, taxonomic discussion, brief biological aspects, distribution]. —Carvalho et al., 2004:10, 17, 49, 76, 78, 81, 84‒86, 90, 93‒99, 101, 103, 105, 107‒109, 118, 134‒135 figs. 43‒47, fig. 51 [morphological description, analysis, phylogenetic discussion]. —Santos et al., 2004:138, 184, 188, 214 [list of species of the Tocantins River, Tucuruí region, brief description of external morphology]. —Rosa et al., 2010:246‒247, 253‒256, 259‒260, 262, 276‒277, fig. 5.2, fig. 5.A.1 [identification key, taxonomy, phylogenetic discussion, feeding habits]. —Carvalho, Lovejoy, 2011:16‒17 [list of analyzed specimens; characters discussed in relation to Heliotrygon ; phylogenetic discussion]. —Frederico et al., 2012:73‒79, figs. 1‒3 [phylogeography, molecular analysis, conservation]. —Mojica et al., 2012:42 [list of endangered species of fishes of Colombia]. —García-Villamil et al., 2013:288‒294, figs. 4‒6 [molecular systematics, phylogenetic discussion]. —Sánchez-Duarte et al., 2013:319, 322, 330, 332 [comercialization]. —Silva, 2014: vol 1., 24, 277‒280, 370, 383, 412, 418, 483, vol2., ix, 148, 188, fig. 148, fig. 188 [morphological description of scapulocoracoid, pelvic girdle, skeletal elements of paired fins, phylogenetic discussion]. —Fontenelle, Carvalho, 2016:1‒3, 8‒11, figs. 1‒2, fig. 9b, fig. 10b, fig. 11 [brain morphology, phylogenetic discussion]. —Garcia et al., 2016:4483‒4489, figs. 2‒5 [molecular systematics, phylogenetic discussion]. —Loboda, 2016: vol.1., vi, viii, 2‒5, 7, 14‒18, 21‒58, 60‒61, 65‒66, 68‒71, 73, 75, 79‒87, 91, 94‒96, 100, 105, 108‒113, 117, 119‒123, 126‒127, 130‒131, 133‒136, 142, 147‒148, 151‒154, 156, 164‒168, 189‒192, 195, 198, 204‒211, vol.2., viii-x, 2‒31, 75, figs. 2‒38 [morphometry, morphological description, taxonomic revision, diagnosis, synonymy, distribution, morphological characters discussion]. —Carvalho, 2016b:3, 55, 57‒59 fig. 49c, p. 57 [occurrence in lower portion of the Tapajós River, identification key]. —Carvalho, 2016c:624 [species account, identification, illustration, distribution]. —Sánchez-Duarte et al., 2016:151‒156, figs. 15‒17 [biological data, habitat].

Holotype. Formerly in the ZSM, considered lost (Rosa, 1985a; Loboda, 2016), probably during a bombing raid in April 1944 (Rosa, 1991) (see Discussion below).

Neotype. MZUSP 117155 , male, 603 mm DW, Brazil, State of Pará , municipality of Colares, Marajó Bay, 00º55’34’’S 48º17’25’’W, 16 Aug 2007, F. P. L. Marques, M. Cardoso & V. M. Bueno . Neotype herein designated (see Discussion below).

Diagnosis. Paratrygon aiereba is distinguished from congeners by a combination of characters. An evident pair of big and dark spots on the preorbital region of the disc that resembles the shape of “eyebrows” or a “mustache” (vs. P. orinocensis and P. parvaspina lacking this pair of preorbital spots). Spiracular process great and knob-shaped in neonates, juveniles, subadults and adults, being more developed (almost covering the entire spiracle aperture) and with some small dermal denticles in adults (vs. P. orinocensis has short and straight spiracular process with developed dermal denticles, P. parvaspina has an extremely short and reduced spiracular process, being just more visible in adult specimens, which possesses few dermal denticles). Spiracles large and quadrangular, mean spiracle length 6% DW [4.4 to 11.6% DW] (vs. P. orinocensis has triangular and slightly smaller spiracles, mean spircale length in 5.6% DW [4.5‒7.9% DW], and P. parvaspina has very small and quadrangular spiracles, with mean spiracle length 5.2% DW [4.9 to 5.8% DW]. Few tooth rows in the upper and lower jaws 16‒26/14‒20 (vs. P. orinocensis with 22‒35/20‒29, and P. parvaspina with 31/19‒22). Frontoparietal component of fontanelle very large, with its posterior extremity very broad and rounded (vs. P. orinocensis with a very narrow frontoparietal component with a number eight shape, and P. parvaspina that has a broad frontoparietal component but narrower than in P. aiereba ). Propterygium not very curved, straighter at its posterior portion (vs. P. orinocensis and P. parvaspina with a more curved propterygium, including at their posterior portions).

Description. For general appearance of P. aiereba , see Figs. 33‒34 , 38‒40 , for morphological characters examined see Figs. 4G‒I , 35‒37 , 41‒58 . Measurements and counts presented in Tabs. 5‒6, respectively, and S4‒S5. In the description below, P. aiereba is directly compared to the Orinoco Paratrygon species.

Among the three species of Paratrygon , P. aiereba is the species that reaches the largest dimensions ( Tabs. 1, 3 and 5), with means of total length, disc length, and disc width, respectively, 594.7, 398.2, and 362.2 mm, and the maximum size of these measurements reaching, respectively, 1270, 867 and 786 mm. Paratrygon orinocensis is the largest species of the genus in the Orinoco basin reaching a total length of 866 mm, and disc dimensions of 634 DL and 573 mm DW ( Tab. 1). Paratrygon parvaspina is the smallest species of the genus, with means of 409.4 TL, 320.6 DL, and 299.6 mm DW ( Tab. 3), with its disc width not exceeding 500 mm in the greatest specimen measured (holotype, IAvH-P 12447).

As in the other two new species of the genus, P. aiereba also has a subcircular to oval disc, with mean of disc length in 110.3% DW [103.7 to 117.7% DW]. However, both new species from the Orinoco basin present a more rounded disc, with P. parvaspina presenting the roundest disc among all three species, with mean of its disc length

106.5% DW ( Tabs. 1, 3, 5). The median concavity of the anterior disc margin of P.

aiereba is more pronounced and visible in adult and subadult specimens ( Figs. 33‒34 ,

38‒40 ; S 4 ); all specimens of P. orinocensis (from juveniles to adults) possess this concavity very pronounced ( Figs. 1‒3; S1 ); on the other hand, in P. parvaspina this concavity is extremely reduced ( Figs. 19‒20 ). Paratrygon orinocensis possesses a shorter disc than P.

aiereba and P. parvaspina , with the mean distance between anterior margin of disc and cloaca 85.6% DW ( P. aiereba 89.5% DW and P. parvaspina 90.3%; Tabs. 1, 3, 5).

Neotype Paratrygon aiereba Mean SD Range N MZUSP 117155

mm %DW mm %DW mm %DW mm %DW

Total length 937 155.4 594.7 178.8 207.6 44.4 271 1270 111.0 283.7 43

Disc length 645 107.0 398.2 110.3 181.3 3.1 171 857 103.7 117.7 45

Disc width 603 100.0 362.2 100.0 166.7 0.0 147 786 100.0 100.0 45

Interorbital distance 62 10.3 38.6 10.8 17.4 0.7 19 84 9.3 12.9 45

Interespiracular distance 88 14.6 56.5 16.0 23.7 1.6 31 114 13.6 22.4 45

Eye length 7 1.2 5.7 1.7 1.7 0.5 3 11 0.9 2.7 45

Spiracle length 29 4.8 20.9 6.0 8.8 1.4 10 47 4.4 11.6 45

Preorbital length 179 29.7 113.0 31.2 51.7 1.9 47 243 25.3 35.0 45

Prenasal length 167 27.7 105.8 29.5 46.1 1.3 43 212 27.0 32.4 45

Preoral length 185 30.7 118.5 33.0 51.9 1.4 49 237 30.2 36.3 45

Internasal length 50 8.3 29.5 8.3 13.8 0.5 11 63 7.3 9.5 44

Mouth width 59 9.8 37.0 10.2 17.7 0.7 14 80 8.7 12.3 43

Distance between first gill slits 113 18.7 77.8 21.4 38.1 1.2 31 180 18.7 24.3 43

Distance between fifth gill slits ‒ ‒ 66.9 18.6 34.0 1.0 25 167 16.8 21.2 42

Branchial basket length 64 10.6 40.6 11.3 18.5 0.7 17 87 10.0 13.6 45

Length of anterior margin of pelvic 99 16.4 64.0 17.6 30.5 2.1 22 130 14.1 22.9 45 fin

Pelvic fins width 238 39.5 143.5 40.2 67.4 4.5 49 327 30.8 48.9 44

External length of clasper 49 8.1 21.7 4.7 19.9 2.8 4 60 2.3 10.4 25

Internal length of clasper 97 16.1 46.6 10.9 36.4 4.5 11 113 6.7 21.5 24

Distance between cloaca and tail tip 402 66.7 265.2 87.8 97.2 43.0 82 545 19.5 183.0 42

Tail width 36 6.0 23.7 6.6 11.6 0.8 11 55 5.0 8.8 45

Distance between snout tip and 504 83.6 318.4 89.5 146.6 3.2 139 720 83.6 97.1 44 cloaca

Distance between pectoral axil and 30 5.0 17.0 4.6 9.7 1.1 5 40 2.3 7.5 45 posterior margin of pelvic fin

Distance between cloaca and caudal 127 21.1 79.8 23.5 35.9 3.0 42 191 17.5 31.3 41 sting

Caudal sting length 45 7.5 36.8 11.3 15.0 2.8 17 80 3.0 17.9 38

Caudal sting width 4 0.7 3.3 1.0 1.5 0.3 1 7 0.4 1.5 40

Dorsal pseudosiphon length 12 2.0 8.4 1.5 3.7 0.5 1 12 0.4 2.0 11

Ventral pseudosiphon length 37 6.1 30.4 5.4 12.8 1.7 7 52 2.1 7.6 9

In relation to head proportions, P. parvaspina possesses the largest mean interorbital distance of 11.6% DW, P. aiereba has 10.8% DW, and P. orinocensis has the smallest mean at 9.9% DW. In relation to interspiracular distance, P. aiereba possess the largest mean with 16% DW, whereas P. orinocensis has 15.8% DW and P. parvaspina has 15.5% DW. All three species possess pedunculate, small eyes ( Figs. 4 , 5 , 21 , 35 ), however, P. parvaspina has the greatest mean eye length at 2.2% DW, whereas P. orinocensis has 1.9% DW and P. aiereba has 1.7% DW ( Tabs. 1, 3, 5). Spiracles possess diferent shapes among the three species: P. aiereba possesses large, quadrangular spiracles ( Figs. 4G‒I , 35 ) with mean length 6% DW [4.4 ‒ 11.6% DW]; P. orinocensis has triangular and slightly smaller spiracles ( Figs. 4A‒C , 5 ) with mean length 5.6% DW [4.5‒7.9% DW]; and P. parvaspina possesses very small and quadrangular spiracles ( Figs. 4D‒F , 21 ), with mean length 5.2% DW [4.9‒5.8% DW]. Spiracular process in P. aiereba great, knob-shaped in neonates, juveniles and adult specimens, being more developed and almost covering the entire spiracle aperture in adults; dermal denticles on this process very small in P. aiereba , even in adults ( Fig. 35 ). Paratrygon orinocensis has short and straight spiracular processes with developed dermal denticles ( Fig. 5 ). Paratrygon parvaspina has extremely short and reduced spiracular processes, being just more visible in adult specimens, and with few dermal denticles present ( Fig. 21 ).

Paratrygon aiereba has intermediate values of preorbital, prenasal and preoral distances proportions compared with the new species, with its preorbital, prenasal and preoral means, respectively, 31.2%, 29.5% and 33% DW ( Tab. 5). Head closer to the anterior margin of the disc in P. orinocensis , with means of preorbital, prenasal and preoral distances respectively 29.9%, 27.5% and 30.9% DW. Paratrygon parvaspina has the greatest preorbital, prenasal and preoral distances among the three species with means, respectively, 32.2%, 31.5% and 35% DW; even the ranges of these measurements between the two sympatric species of the Orinoco basin are very contrasting, mainly in prenasal and preoral distances ( Tabs. 1, 3). Mouth and nostrils proportionally similiar in all three species: P. aiereba has means of internasal distance and mouth width, respectively, 8.3% and 10.2% DW, P. orinocensis 8.3% and 10% DW, and P. parvaspina 8.1% and 9.8% DW ( Tabs. 1, 3, 5).

Teeth triangular, large, cuspidate, and arranged in quincunx in both jaws in all three species ( Figs. 6 , 36 , 37 ), with teeth in central rows presenting more developed cusps. Adult specimens of P. orinocensis possesses more developed and higher cusps than P. aiereba and P. parvaspina ( Fig. 6 ). Paratrygon aiereba has fewer tooth rows in upper and lower jaws than both new species with 16‒26/14‒20, whereas P. orinocensis has 22‒35/20‒29 and P. parvaspina has 31/19‒22; however, P. aiereba has more exposed teeth at symphysis, 3‒6/3‒5, vs. 2‒4/ 3‒4 in P. orinocensis ( Tabs. 2, 4, 6).

Paratrygon aiereba has a large and laterally expanded branchial basket with means of distance between first pair of gill slits, distance between fifth pair, and branchial basket length, respectively, 21.4%, 18.6%, and 11.3% DW. Both new species of the Orinoco basin have proportionally smaller branchial baskets than P. aiereba , with means in P. orinocensis , respectively, 20.1%, 17.3%, and 10.9% DW, and in P. parvaspina 20.5%, 17.6%, and 10.4% DW ( Tabs. 1, 3, 5).

Pelvic fins triangular and dorsally covered by the disc in all three species of Paratrygon ( Figs. 1B , 2B, D , 3B, D , 19B, D , 20B, D , 33B , 38B , 39B, D , 40B, D; S 1B, D, S 4B, D ). Proportions of pelvic fin measurements very similar among the three species: means of length of anterior margin, pelvic fin length, and distance between the axils of pelvic and pectoral fins in P. aiereba , respectively, 17.6%, 40.2%, and 4.8% DW; in P. orinocensis , 16.9%, 38.7%, and 3.8% DW; and in P. parvaspina , 16.6%, 42.5%, and 4.1% DW ( Tabs. 1, 3, 5). Male adult specimens of P. aiereba and P. orinocensis with short, robust and cylindrical claspers presenting rounded tips ( Fig. 33B , and also see fig. 3 of Moreira et al., 2018 for more external details). Means of external and internal lengths of clasper in all male specimens (including neonates, juveniles and subadults) of both species, respectively, 4.7% and 10.9% DW in P. aiereba , and, 3.4% and 8.9% DW in P. orinocensis ( Tabs. 1, 5); only a single juvenile male specimen of P. parvaspina was measured (see Tab. 3). Claspers show a significant size increment from neonates to adults; however its growth is greater between subadult and adult specimens (S2 and S5, respectively, for P. orinocensis and P. aiereba ); range of external and internal lengths of clasper in neonates of P. aiereba , respectively, 2.4 to 2.7% and 6.7 to 7.5%; in juveniles 2.3 to 4.4% and 6.8 to 11.7%; and in adults 6.6 to 10.4% and 15.1 to 21.5% DW (S5). Pseudosiphon and ventral pseudosiphon also show this size increment from neonates to adults in these both species (S2, S5). Pseudosiphon small, located in the medial region of internal lateral portion of clasper; ventral pseudosiphon larger, occurring in the external lateral portion of clasper from the same level of anterior margin of pseudosiphon to clasper tip. Spermatic groove dorsally located from the same level of posterior margin of pelvic fins to the distal extremity of clasper; at the level between the two pseudosiphons, this groove curves toward the external lateral portion (see fig. 3 of Moreira et al., 2018 for clasper of P. aiereba ).

Paratrygon aiereba and P. orinocensis possess long tails with mean distances between cloaca and caudal sting insertion (pre-caudal sting portion) in both species 23.5% DW, and mean distances between cloaca and tail tip (post-caudal sting portion), respectively, 87.8% and 100.7% DW ( Tabs. 1, 5). Paratrygon parvaspina has a shorter tail, with means of precaudal sting and distance between cloaca and tail tip, respectively, 21.1% and 50.4% DW ( Tab. 3). However, tail width in all three species very similar, with means around 6.5 DW ( Tabs. 1, 3, 5). All three species present a decrease of tail length (pre- and postcaudal sting portions) from neonates to adult specimens (see values of tail measurements in S2, S3 and S5). Tail folds in the three species lack morphological differences, with lateral tail folds slightly developed and occurring from base of tail to caudal sting insertion, and dorsal and ventral tail folds present just on postcaudal sting portion and poorly developed.

Color in alcohol. Paratrygon aiereba presents dorsal disc coloration in gray or brown tones, with dark and light spots spread over disc; dark spots larger and more conspicuous than light spots ( Figs. 33A , 34 , 38A , 39A, C , 40A, C; S 4A, C ). Paratrygon orinocensis and P. parvaspina present a similar pattern, in gray and brown tones with large dark and small light spots on disc; however specimens of both Orinoco basin species also have beige on dorsal disc, mainly P. parvaspina ( Figs. 1A , 2A, C , 3A, C , 19A, C , 20A, C; S 1A, C ). Dark spots of P. aiereba dark brown, dark gray or black, generally large, vermiculate or rounded, and sometimes axon shaped, being more evident and larger near disc margin; some adults present small gray rings within the largest dark spots on central disc, and the great majority of specimens of P. aiereba also have an evident and diagnostic preorbital pair of dark spots extremely developed on preorbital region that resembles a pair of eyebrows or a mustache shape. Paratrygon orinocensis has a similar pattern of dark spots, with various shapes and dark tones (see pags. 18‒19), however smaller than in P. aiereba , and generally rounded with small beige specks inside largest dark spots in adults; dark spots in this species larger near the central disc region. Paratrygon parvaspina presents dark spots with vermicular or slender dendritic shapes, spread and more or less evenly spaced (mainly in adult specimens) over disc, and small and more concentrated near disc margins. No specimen of both new Orinoco basin species present the preorbital pair of developed dark blotches observed in P. aiereba . Light spots of P. aiereba light gray, beige or light brown, rounded and not as evident as the dark spots, intermingled in some specimens. Paratrygon orinocensis has these spots polygonal and generally about same size as eye diameter; P. parvaspina with rounded, oval or polygonal light spots. Dorsal coloration of tail in P. aiereba similar to color pattern present from dorsal disc to caudal sting insertion, with dark spots occurring laterally on tail, and light spots on central dorsal area; postcaudal sting portion with very dark tone. The opposite occurs in the precaudal sting portion of P. orinocensis with dark spots present on central dorsal area and light spots occurring laterally; postcaudal sting portion also dark, but with some beige specks. Paratrygon parvaspina also has dorsal tail coloration similar to dorsal disc, with dark spots spread on the precaudal sting portion, and postcaudal sting tail light beige or light gray presenting many and small dark specks.

Paratrygon aiereba possess a similar pattern of ventral coloration of the two new species, with two tones present on the disc: one light (white or light beige), predominant on central area of disc and anterior margin, and another one dark (brown, gray or beige) occurring on the lateral and posterior margins of disc; also in all three species, some specimens possess small and rounded, oval or vermiculate darker spots close to disc margins ( Figs. 1B , 2B, D , 3B, D , 19B, D , 20B, D , 33B , 38B , 39B, D , 40B, D; S 1B, D, S 4B, D ). Pelvic fins and claspers with similar pattern among the three species: the same tones of ventral disc occur on pelvic fins and claspers, with light tone present on anterior margin of pelvic fins and clasper base, and dark tone present posteriorly. Ventral coloration of tail also similar among the three species on precaudal sting portion, presenting the same light tone on central disc with some gray spots. Coloration on postcaudal sting portion darker and similar in P. aiereba and P. orinocensis ; P. parvaspina presents on this portion lighter, either beige or gray tone, slightly darker near tail tip; ventrally numerous small dark gray specks present in P. parvaspina .

Squamation. Paratrygon aiereba possess dermal denticles scattered throughout dorsal disc and tail as P. orinocensis and P. parvaspina , with denticles on disc center greater and more visible than at margins; on tail, denticles greater on precaudal sting portion, and on postcaudal sting portion denticles minute and scarce ( P. parvaspina without denticles on postcaudal sting portion of tail).

Paratrygon aiereba has small dermal denticles, even on disc where they reach their greatest size, their diameters not reaching one mm ( Figs. 41‒42 ). Paratrygon orinocensis possesses larger denticles on disc center than P. aiereba , with diameters reaching two

mm ( Fig. 7 ), whereas P. parvaspina has small denticles with diameters 0.5 mm on central disc ( Fig. 23 ). On central disc region in P. aiereba , dermal denticles have a high and narrow crown, with a higher and pointed central coronal plate (ccp) surrounded by smaller, pointed or rounded lateral coronal ridges (lcr) vary in number between three and six depending on their size; adult specimens present crowns with more lateral ridges ( Fig. 42 ). Paratrygon orinocensis has dermal denticles on central disc with wide and high crowns, presenting a central coronal plate morphologically very similar to its lateral coronal ridges; lcr in adult specimens more than 12 ( Fig. 7 ). Dermal denticles on central disc of P. parvaspina morphologically similar to P. aiereba ( Fig. 23 ). Dermal denticles on disc margins in P. aiereba more scattered, mainly on lateral margins ( Fig.

43). Morphology of dermal denticles on anterior and lateral margins similar to central disc ( Figs. 43A‒B ), however with fewer lateral crown ridges; dermal denticles on anterior margin have a more pointed ccp than central denticles ( Figs. 43A , 44A ). Dermal denticles on posterior margins with a very developed and pointed ccp ( Fig. 44D ). Some specimens of P. aiereba present on their posterior disc margins well-developed thorns,

much greater than dermal denticles; these thorns have a large basal plate (bp), generally with some denticles, and a very high and developed pointed crown (cr) ( Figs. 44E‒F ).

Paratrygon aiereba has dermal denticles on tail base with morphology similar to thorns,

larger than dermal denticles from other parts of disc (their basal plates reach one mm),

with a very developed ccp (reaching one mm high), and presenting small and pointed lateral crown ridges ( Fig. 45 ). Paratrygon orinocensis has two morphological types of dermal denticles on tail base ( Fig. 9 ): one similar to dermal denticles on central disc area

( Figs. 9A, C‒D ), and another similar to typical dermal denticles of tail base of P. aiereba

( Figs. 9A‒B ).

Paratrygon aiereba has dorsal and lateral rows on tail ( Fig. 46 ). Adult specimens have two or three dorsal rows with developed, high and broad-based thorns; some specimens also have tubercular ones. Dorsal rows extend from tail base and reach caudal sting insertion. Adults also with developed lateral rows, generally a single row, extending from the medial portion of tail to the region just posterior to caudal sting tip; lateral rows also with developed thorns, more developed than dorsal thorns in some specimens ( Fig. 46A ). Large juvenile specimens present dorsal and lateral rows very similar to adults, however with thorns not as developed ( Figs. 46B‒C ). Most juvenile specimens have only dorsal rows, with few small thorns; lateral rows less developed and occurring in few specimens ( Figs. 46D‒E ). Neonates only with incipient dorsal rows on the tail base; however some specimens lack thorns ( Fig. 46F ). Paratrygon orinocensis presents only dorsal rows on tail, lacking lateral rows ( Fig. 10 ). Adult specimens with one or two dorsal rows of developed and high thorns with broad base ( Figs. 10A‒B ). Subadults and larger juveniles generally with only one row, with thorns high and with broad base ( Figs. 10C‒E ). Most juvenile specimens with only part of this single dorsal row with small thorns ( Figs. 10F‒G ). Neonates with only a poorly developed row of minute thorns on tail base ( Fig. 10H ). Paratrygon parvaspina has dorsal and lateral rows of thorns on tail ( Fig. 24 ). Adult specimens with just one dorsal and one lateral row. Dorsal row in adult and large juvenile specimens extends from tail base to caudal sting insertion; dorsal thorns developed, high and with broad tubercular bases ( Figs. 24A‒C ). Lateral rows in these specimens extend from just anterior to medial portion of tail and reach caudal sting insertion; lateral thorns very similar to dorsal ones. Juveniles only present a dorsal row with thorns slightly less developed than adult specimens, and with broad tubercular bases ( Figs. 24D‒F ).

Paratrygon aiereba with long and slightly broad caudal sting ( Fig. 47 ); P. orinocensis with similar caudal sting as P. aiereba , whereas P. parvaspina has a diagnostic small and slender caudal sting ( Figs. 11 , 25 ). Mean caudal sting length in P. aiereba 11.3% DW and range between 3 and 17.9% DW; caudal sting mean width 1% DW and range between 0.4 and 1.5% DW ( Tab. 5). Adults possess one or two very developed caudal stings, with lateral serrations along their length, with larger serrations closer to tip; a dorsal medial groove present in caudal sting, from sting base to its distal third ( Figs. 47A‒B ). Subadult specimens have a caudal sting similar to adults, however its serrations occur on the distal two-thirds of sting and lack a dorsal medial groove. Larger juvenile specimens also have one or two stings, with serrations only present on the distal two-thirds ( Fig. 47C ). Most juveniles have only one caudal sting with few lateral serrations present on distal two-thirds ( Figs. 51D‒F ). Paratrygon orinocensis has a mean caudal sting length 12% DW [6.7‒15.3% DW], and caudal sting width with mean 1% DW [0.6‒1.7% DW] ( Tab. 1). Paratrygon parvaspina has a very reduced caudal sting, with mean length 6.2% DW [5.6‒7.1% DW], and mean width 0.9% DW ( Tab. 3).

Lateral line. Paratrygon aiereba has the junction of four canals (JFC) very small, its posterior portion the junction point of hyomandibular (HMD) and infraorbital canals (IOC), and its anterior portion the junction of supraorbital ( SPO ) and nasal (NAS) canals ( Fig. 48B ). JFC in P. orinocensis very small ( Fig. 12 ), and P. parvaspina has the largest JFC among the three species ( Fig. 26 ).

From JFC, hyomandibular canal (HMD) extends posteriorly through its angular component (ang), which contourns externally the adductor mandibulae; P. aiereba has a straight angular component ( Fig. 48A ), whereas P. orinocensis and P. parvapsina have a more curved component ( Figs. 12B , 26B ). Hyomandibular canal continues to descend and externally surrounds the branchial basket at about central region of disc, forming the jugular component (jug); P. aiereba and P. parvaspina have this component straighter and posteriorly directed ( Figs. 26A , 48A ) whereas in P. orinocensis the jug component more directed to central disc region ( Fig. 12A ). Jugular component descends farther and posterior to the level of scapulocoracoid; this canal posteriorly extends slightly away from central disc until it reaches a region slightly anterior to level of pelvic girdle; in this part, the jugular component forms the subpleural loop (spl). Paratrygon orinocensis has a wide spl with two short posterior subpleural tubules (pst) ( Fig. 12A ); P. aiereba and P. parvaspina have a short spl with three short pst, with some of them branched ( Figs. 26A , 48A ). After the spl, hyomandibular canal ascends anteriorly and parallel to jugular component until level of fourth pair of branchial slits, where the canal directs anterolaterally to disc margin, forming its subpleural component (spc). Paratrygon aiereba has part of this component extending to level of fourth pair of gill slits slightly straighter than the other two species ( Fig. 48A ); P. orinocensis has the same portion of its spc directed to cental disc region ( Fig. 12A ), and P. parvaspina has its entire spc as a big curvature directed toward anterolateral disc margin ( Fig. 26A ). At mouth level, subpleural component continues approaching anterolateral margin of disc, and from there proceeds anteriorly, parallel and very close to margin, until it reaches the junction with prenasal component of nasal canal (pnc); this entire portion of spc presents subpleural tubules (spt) which are longer at lateral margins, reducing in size close to the anterior margin. Paratrygon aiereba and P. orinocensis have the beginning of the spt at level of mouth ( Figs. 12 , 48 ), whereas P. parvaspina has the beginning of its spt s at level of second pair of gill slits ( Fig. 26 ).

From the JFC, infraorbital canal (IOC) extends laterally and distally to just anterior to level of mouth, and subsequently ramifies into its suborbital component (sub). Suborbital component of IOC with honeycomb-shaped ramifications, which are greater posteriorly and smaller close to subpleural component of HMD and to the anterior disc margin; sub ramifications connect in various points with subpleural component of HMD, and in only two points with prenasal component of NAS. Paratrygon aiereba and P. orinocensis have more honeycomb-shaped ramifications ( Figs. 12 , 48 ) than P. parvaspina ( Fig. 26 ).

Supraorbital canal ( SPO ) emerges from the JFC directed anteriorly and inclined (in a 45° angle) to anteromedial region of disc, forming orbitonasal component (orb). At level between the nostril and anterior margin of disc, SPO continues anteriorly to form the prenasal loop (pnl), before turning posteriorly again. Orbitonasal component in P. aiereba extends straight to the pnl ( Fig. 48 ); P. orinocensis has a small curvature anteriorly directed in its orb ( Fig. 12 ), whereas P. parvaspina has a smooth and small curvature posteriorly directed in its orb ( Fig. 26 ). Also P. parvaspina has a slightly wide pnl compared to the other two species ( Fig. 26B ). From pnl, SPO extends posteriorly close to the nostrils where it forms a new central loop, the nasointernal loop (nil) directed anteriorly. After nil, SPO extends anteriorly until up to half prenasal distance where it connects with the prenasal component of NAS; in this region, named subrostral component of SPO (sbr), the vesicles of Savi (vS) occur. Paratrygon aiereba has a longer sbr than the other two new species, and the number of vS of P. parvaspina is smaller (around six vS; Fig. 26B ) than in P. aiereba and P. orinocensis (around 12 vS; Figs. 12B , 48B ).

Nasal canal (NAS) extends anteromedially from the JFC next to external margin of nostril in a 45° angle, where it penetrates the disc. The canal emerges in region between nostrils, next to longitudinal midline of body, and makes a small curvature in direction of anterior disc, where it ascends straight to anterior margin of disc, forming in this portion its prenasal component (pnc). At the pnc, the NAS connects with the other three canals. Connection of SPO with NAS in P. aiereba is located more anteriorly than in the two new species ( Figs. 12B , 26B , 48B ).

Mandibular canal (MNC) extends posteriorly from midline of disc next to mouth and contours posteriorly the adductor mandibulae muscle until just anterior to level of first gill slit, where it enters the body; MNC makes a central posterior curve in P. aiereba ( Fig. 48 ), descends in a straight fashion at a 45° angle in P. orinocensis ( Fig. 12 ), and descends straight in almost a 90° angle in P. parvaspina , where at the level of first pair of gill slits it makes an external curve surrounding the adductor mandibulae muscle ( Fig. 26 ).

Skeleton. Mersitic counts of vertebrae and pectoral and pelvic radials of P. aiereba shown in Tab. 6.

Neurocranium of P. aiereba with length similar to synarcual cartilage ( Figs. 49 , 50 ). Nasal capsules (NC) and anterior region of neurocranium well inclined ventrally in a 45° angle in lateral view ( Fig. 49 ). Neurocranium widest at postorbital process (POP) and nasal capsules, whereas orbital region, anterior to supraorbital process (SP), is the narrowest portion. In dorsal view, neurocranium of P. aiereba more similar to P. parvaspina than to P. orinocensis , which has an evident “T” shape and a more slender orbital region than P. aiereba and P. parvaspina ( Figs. 13 , 27 , 50 ).

Nasal capsules broad, oval and inclined, with a relatively large internasal septum (IS); IS larger in P. orinocensis and narrower in P. aiereba ; NC in P. aiereba laterally surrounded by first segment of propterygium (FSP), as in P. orinocensis , and different from P. parvaspina in which the FSP does not directly contact the lateral surface of NC ( Figs. 13 , 27 , 50 ). Between nasal capsules, at the anteroventral tip of neurocranium, a small rostral projection (RPJ) is present ( Figs. 49 , 50 ); RPJ minute and not developed in P. orinocensis , whereas P. parvaspina has a large and circular RPJ ( Figs. 13 , 27 ). Posterolaterally NC articulates with the antorbital cartilage condyle (AOC). Nasal cartilages (NSC) present ventral to the NC apertures ( Fig. 49 ).

Preorbital processes (PRP) just posterior to NC and dorsally positioned, triangular and not very projected laterally beyond level of NC ( Figs. 49 , 50 ) in P. aiereba , as in P. orinocensis ; however, P. parvaspina has PRP very projected and extending externally beyond level of NC ( Figs. 13 , 27 ). Base of PRP with two foramina of preorbital canal (FPC) visible dorsally and ventrally, the anterior more developed than posterior ( Fig. 49 ). Posterior to PRP, on dorsolateral portion of neurocranium, the supraorbital crest (SOC) covers entire dorsal part of lateral walls of orbital region from the PRP to supraorbital process ( Figs. 49 , 50 ); P. aiereba has a slightly more developed SOC than the two species from Orinoco basin ( Figs. 13 , 27 , 50 ).

The anterior cerebral vein foramen (ACVF) is found on lateral wall of orbital region of neurocranium; optic nerve foramen (II) large and posterior to PRP, close to it; both foramina are positioned slightly dorsally on lateral wall of orbital region ( Fig. 49 ). Optic pedicel (OP) closely adjacent to II; oculomotor nerve foramen (III) dorsal to OP; efferent spiracular artery foramen (ESAF) ventral to OP. Supraorbital process (SP) level with OP. Orbital fissure (OFS) posterior to III, and ventral to it is the interobital vein foramen (IVF); IVF easy to visualize in ventral view of neurocranium ( Fig. 49 ). Orbital fissure located at junction of orbit with otic capsule; just dorsal to OFS is the wing shaped postorbital process (POP); in dorsal view POP projects laterally from lateral wall of neurocranium at a 45° angle just posterior to SP ( Figs. 13 , 49 ). Posterior and ventral to OFS is the arch shaped lateral commissure (LC); immediately anterior to LC is the hyomandibular ramus of facial nerve foramen (VII). The glossopharyngeal nerve foramen (IX) and the hyomandibular facet (HF) ( Fig. 49 ) are located on lateral wall of otic capsule, posterior and near ventral face of neurocranium.

Roof of neurocranium from NC to POP with a large, spoon-shaped fontanelle composed of anterior, rounded precerebral component (PCF) and posterior, narrow and straight frontoparietal component (FCF) in between the PRP and POP ( Figs. 13 , 27 , 49 , 50 ). Paratrygon aiereba has the largest FCF, with its posterior extremity very broad and rounded ( Fig. 50 ); P. parvaspina also has a broad FCF, however slightly less wide than in P. aiereba ( Fig. 27 ). Paratrygon orinocensis has narrowest FCF, with a “8” shape ( Fig. 13 ). Posteriorly to fontanelle and above otic capsule, two pairs of lymphatic foramina occur: anterior and larger endolymphatic foramina (ELF), and the posterior perilymphatic foramina (PLF) ( Fig. 49 ).

Basal plate of neurocranium with a pair of internal carotid artery foramina (ICAF) located next and below OFS ( Fig. 49 ). A large and circular foramen magnun (FM) stands out in posterior view of neurocranium in the occipital region; vagus nerve foramen (X) lateral to FM, and dorsolaterally to these foramina is the lateralis branch of vagus nerve foramen (LbX). Ventral to FM is the articular surface ( AS), and lateral to it is a pair of occipital condyles (OC) for the articulation with the synarcual cartilage ( Fig. 49 ).

Mandibular arch laterally extended in P. aiereba , with long and proximally arched palatoquadrate (PQ) and Meckel’s cartilage (MC) ( Figs. 50 , 51 ); these cartilages are slightly thinner in P. aiereba than in the two Orinoco basin species ( Figs. 13 , 27 , 50 ). Palatoquadrate straight, slightly arched near its proximal portion, and with a small dorsolateral process (DLP) near its articulation with Meckel’s cartilage ( Figs. 13 , 27 , 50 , 51 ). Meckel’s cartilage with proximal portion slightly more robust and curved, where it articulates with PQ and also with hyomandibular-Meckelian ligament (L); MC presents a long lateral process (LP) which almost reaches dorsal level of PQ ( Figs. 13 , 27 , 50 , 51 ), and also a ventrolateral process (VLP) on its distal extremity ( Fig. 51 ).

Hyomandibula (HYO) rectangular, with its dorsal extremity tapered ( Fig. 51 ). In dorsal view, HYO is long, slender and straight in all three species, slightly more robust and curved at its medial part in P. parvaspina ( Figs. 13 , 27 , 50 ). Hyomandibular-Meckelian ligament (L) slighlty robust despite being reduced, without any type of embedded calcified elements; the ligament possesses a wide connection to HYO, with this part of the ligament broad, contacting almost the entire proximal end of the cartilage ( Fig. 51 ).

As in the Orinoco basin species, P. aiereba has a synarcual cartilage similar in length to neurocranium and laterally expanded mainly at its posterior portion where it articulates with scapulocoracoid ( Fig. 52 ). Dorsomedial crest (DMC) low and occuring over the anterior and medial portions of the spinal nerve canal (SNC); SNC also contains along its total lenght and next to its basal portion several spinal nerve foramina (SNF). Medial portion of synarcual with a small lateral projection (SLP) of its lateral basal surface. On posterior region of synarcual, dorsal socket (DS) broad, with a deep and concave surface positioned above the two ventral condyles which articulate with scapulocoracoid: a large and convex anterior ventral condyle (AVC), and a smaller posterior ventral condyle (PVC) are present; as P. parvaspina, AVC in P. aiereba has a convex surface, whereas P. orinocensis has a straight AVC ( Figs. 14 , 28 , 52 ). Lateral stay (LS) of synarcual cartilage projects anteriorly from its articulation with scapulocoracoid; among the three species, P. parvaspina has the longest and most laterally projected LS ( Figs. 14 , 28 , 52 ).

Paratrygon aiereba presents scapulocoracoid with coracoid bar (CB) slighlty arched at anterior face, and straight posteriorly. Broad scapular process (SCP) quadrangular in lateral view and triangular in dorsal view, its articular region with synarcual cartilage extending laterally ( Figs. 53 , 54 ). Coracoid bar in P. orinocensis more slender than in P. aiereba , with curved anterior and posterior faces, whereas P. parvaspina has a more broad CB with a more straight anterior face than in the other two species ( Figs. 15 , 29 , 53 , 54 ).

Scapular process dorsally with a small dorsolateral crest (DLC), more pronounced anterolaterally ( Figs. 53 , 54 ); in some specimens of P. aiereba, DLC exceeds laterally to level of mesocondyle (MSC) ( Fig. 54 ). Paratrygon orinocensis also has a very pronounced DLC exceeding the MSC laterally, however, P. parvaspina has a short and not so pronounced DLC which does not exceed MSC ( Figs. 15 , 29 ). Laterally in central region of SCP, P. aiereba has two broad and deep fenestrae separated from one another by the lateral external face (LEF) of SCP: anterodorsal fenestra (ADF) smaller and deeper, and anteroventral fenestra (AVF) very wide, encompassing almost the entire ventral area of the LEF. Posteriorly and separated by MSC are the postdorsal fenestra (PDF) and the postventral fenestra (PVF), both small, but with the PVF slightly larger ( Fig. 53 ).

The condyles that articulate with basal elements of pectoral girdle are positioned on horizontal axis of lateral face of SCP ( Figs. 53 , 54 ). On the anterior extremity of SCP is the dorsoventrally elongated procondyle (PC). Procondyle articulates with the anteriormost part of the base of propterygium (PPT), which presents an inverted “L” format ( Fig. 54 ). Between procondyle and mesocondyle is the long LEF of the SCP, which separates the two major fenestrae (ADF and AVF) and where it contacts the posterior and greater part of the PPT base ( Fig. 53 , 54 ). Mesocondyle (MSC) anteriorly and next to metacondyle (MTC), both condyles positioned and laterally projected on posterior extremity of horizontal axis of the lateral face of SCP; MSC small and rounded, separates the two small fenestrae (PDF and PVF) and articulating with mesopterygium (MSP); MTC slightly dorsoventrally elongated, situated in the posterior corner of horizontal axis of SCP and articulates with metapterygium (MTP) ( Figs. 53 , 54 ). Paratrygon aiereba presents the three condyles slightly larger and more pronounced than in the two Orinoco species, whereas P. parvaspina has the smallest condyles ( Figs. 15 , 29 , 53 , 54 ).

Paratrygon aiereba possesses three basal elements of pectoral fin, propterygium (PPT), mesopterygium (MSP), and metapterygium (MTP) articulated with their respective condyles of SCP: PPT with the anterior part of its base articulated with PC and its posterior and greater part contacting the LEF surface; MSP articulates only with MSC; and MTP only contacts the MTC ( Figs. 54 , 55 ).

Propterygium in P. aiereba robust, slightly arched in its anterior portion where it articulates with the antorbital cartilage ( ANT ), and, as in the other two species, with its posterior extremity broader than anterior ( Fig. 55A ). Articulation base of PPT with the scapulocoracoid with an inverted “L” format, with its anterior portion articulated with PC and its posterior and greater portion contacting the LEF surface of SCP. In addition, PPT also articulates with mesopterygium through a small articular surface (SAS) on its posterior extremity. First segment of propterygium (FSP) one-fourth length of PPT, extending anteriorly to level of slightly less than half of the anterior portior of nasal capsules, and articules anteriorly with the first two robust rays of pectoral fin ( Fig. 55A ).

Propterygium more curved in both Orinoco species than in P. aiereba ; P. parvaspina has the most robust PPT among the three species, whereas P. aiereba has the anterior portion of PPT less tapered and unequal in relation to its posterior portion ( Figs. 16 , 30 , 55 ). Paratrygon orinocensis and P. aiereba has its FSP contacting externally the nasal capsules (contact surface is larger in P. orinocensis ), whereas in P. parvaspina this contact does not occur. Small articulation surface (SAS) of the PPT in P. orinocensis larger than P. aiereba and P. parvaspina ( Figs. 16 , 30 , 55 ).

Mesopterygium in P. aiereba slightly shorter or equal to SCP at its anteroposterior axis ( Fig. 55B ). Posterior portion of MSP more developed, and with the articulation point with MSC at its proximal extremity. Anteriorly and next to this articulation point, MSP has a pronounced concavity where it contacts the SAS of PPT. Anterior portion of MSP thinner than posterior portion and slightly wider than half of posterior portion. Anterior and posterior extremities of MSP contact respectively PPT and MTP and junctions of median radials (JMR) of pectoral fin. JMR located at the anterior extremity of MSP larger and more numerous ( Fig. 55B ).

Concavity of MSP more pronounced in P. aiereba and P. orinocensis than in P. parvaspina ; JMR more numerous in P. aiereba than in the two species, and the JMR in P. parvaspina occurs in the anterior extremity of MSP ( Figs. 16 , 30 , 55 ).

Metapterygium in P. aiereba long, arched and slender, with its medial portion between half or little more than half the width of the PPT. Anterior part of MTP more robust than posterior, being articulated with MSC of SCP at its anterior extremity, and contacting MSP ( Fig. 55C ). Posterior portion of MTP segmented in three or four posterior segments (PSM), being the posterior PSM sucessively smaller than the anterior segments ( Fig. 55C ).

Paratrygon parvaspina has the most robust MTP among the three species, with its anterior part much larger and robust than the other two; MTP in P. parvaspina also has more unequal extremities than P. aiereba and P. orinocensis , with its MTP more tapered from anterior to posterior portions than the other species ( Figs. 16 , 30 , 55 ).

Paratrygon aiereba has an arched puboischiadic bar (PB), with its anterior portion straighter, and posterior margin half-circle shaped; some specimens possess a PB with an inverted “V” format, with the anterior portion more inclined than other specimens ( Figs. 56 , 57 ). Lateral extremities of PB possess two ventral processes, each with a dorsal projection, besides three pairs of dorsoventral obturator foramina (OF). Iliac process (IP) well developed, in rectangular shape, located on external posterior portion of lateral extremity of PB, forming the posteriormost extremity of pelvic girdle. The dissected specimen of P. aiereba (MZUSP 103896) has a small foramen (SF) in the external face of IP next to its insertion on PB ( Fig. 56 ). Ischial process (ISP) small, triangular, located on the internal portion of lateral extremities of PB, delineating the half-circle shape of the posterior margin. Lateral prepelvic process (LPP) dorsal to lateral extremities of PB, small and triangular ( Figs. 56 , 57 ). Anterior portion of PB stands out the long and very developed prepelvic process (PPP) with an equivalent length to the width of PB ( Fig. 56 ).

Paratrygon parvaspina possesses less developed IP, ISP and LPP than the other two species, and their tips are more rounded; IP much more developed and long in P. aiereba than in the other two species ( Figs. 17 , 31 , 56 , 57 ). Clasper skeleton of P. aiereba composed of the following elements divided into basal, axial and terminal groups: basal elements - two basal segments or intermediate cartilages, basal 1 (B1) and basal 2 (B2), and beta cartilage (β); axial elements - axial cartilage (AX), dorsal marginal cartilage (DM), and ventral marginal cartilage (VM); and terminal elements - dorsal terminal 1 (DT1), dorsal terminal 2 (DT2), and acessory terminal 1 (AT1) ( Fig. 58 ).

In dorsal view, β cartilage is the anteriormost skeletal element, its anterior extremity articulated with B1 and B2, its posterior extremity connected with DM; β cartilage long and cylindrical, slender and slightly curved. Dorsal marginal posterior to the β cartilage, connecting posteriorly with the DT2, with a flat shape, and projecting laterally and externally to central axis of clasper. Dorsal terminal 2 and AT1 form the distal portion of clasper skeleton; DT2 with cylindrical shape in dorsal view, its ventral portion more wide and flat; in ventral view DT2 covers AT1 ( Fig. 58 ).

In ventral view, the small and cylindrical B1 and B2 cartilages contact β cartilage at proximal tip of clasper; B2 slightly larger than B1. AX cartilage posterior to B2, also cylindrical, but slender and long, and constituting the principal cartilage of axial group; posteriorly AX connects with DT2 and AT1. Ventral marginal cartilage articules almost along its entire length with AX and is positioned more externally in relation to central axis of clasper; VM wraps around AX, its lateral aspect visible in dorsal view. Ventrally, posterior tip of clasper with large DT1 cartilage, rectangular in shape and covering DT2 and AT1, its lateral extension also visible in dorsal view ( Fig. 58 ).

Geographic distribution. Paratrygon aiereba is herein restricted to the Amazon basin, occurring along the central channel of Solimões-Amazonas river, and also through its main affluents in the upper portion of Amazon basin: headwaters of Caqueta, Madeira, Purus, Putumayo and Ucayali rivers; the distribution of this species covers the territories of Bolivia, Brazil, Colombia, Equador, and Peru ( Fig. 59 ).

Etymology. Aiereba comes from the old Tupi language (a classical indigenous language from Brazil) word aîereba that designates a specific type of marine stingray (possibly Styracura schmardae ; see Ferrão, Soares, 1993, p. 37), which occurs on the coast of northeastern Brazil. This name was first made known during the period of Dutch occupation (1630‒1654) when Marcgrav (1648) used it (possibly from the Tapuya nation) to designate this marine stingray species. As an adjective in the same language aiereba also means smooth, unmarked, shallow (Navarro, Suassuna, 2013).

Material examined. Paratrygon aiereba : Bolivia: AMNH 59865 , male, 281 mm DW, AMNH 59878 , male, 383 mm DW, ZSM 34500 , female, 204 mm DW. Brazil: IAvH-P 11894, female, 472 mm DW, INPA 1331 , female, 255 mm DW, MCZ 297 - S, female, 281 mm DW (syntype of Disceus thayeri Garman, 1913 ) , MCZ 563 - S, female, 303 mm DW (syntype of Disceus thayeri Garman, 1913 ) . MCZ 606 - S, male, (syntype of Disceus thayeri ), MNHN A.1019, female, 324 mm DW, MNHN A.1020, male, 299 mm DW, MNHN A.2269, male, 285 mm DW, MNHN A.2270, male, 147 mm DW, MNHN 1997-0495 , female, 285 mm DW, MPEG uncatalogued, 6, 3 females and 3 males, 255‒786 mm DW, MUSM uncatalogued, male, 220 mm DW, MZUSP 14774 , female, 256 mm DW, MZUSP 51680 , male, 610 mm DW, MZUSP 101015 , female, 150 mm DW, MZUSP 103896 , male, 508 mm DW, MZUSP 103907 , male, 606 mm DW, MZUSP 104029 , male, 436 mm DW, MZUSP 104985 , female, 590 mm DW, MZUSP 104986 , female, 560 mm DW, MZUSP 104987 , male, 568 mm DW, NMW 79194 , female, 314 mm DW, UFPB 3478 , UFPB 3479 . Colombia: IAVH-P 11929 , male, 366 mm DW, IAvH-P 11937, male, 280 mm DW. Peru: IAvH-P 11927, male, 408 mm DW, IIAP uncatalogued, 3, 1 female and 2 males, 194‒208 mm DW, MUSM 0002 , male, 328 mm DW, MUSM 1389 , 2 , 1 female and 1 male, 204 ‒ 207 mm DW, MUSM 7352 , female, MUSM 9423 , male, 428 mm DW, MUSM 47105 , male, 214 mm DW, MZUSP 14772 , female, 221 mm DW, MZUSP 14773 , female, 236 mm DW, MZUSP 117831 , female, 200 mm DW, USNM 264005 , male, 184 mm DW.

Figures

FIGURE 1 | Holotype of Paratrygon orinocensis, IAvH-P 11939, adult female, 286 mm DW, from Orinoco river. A. dorsal and B. ventral views.

FIGURE 2 | Paratypes of Paratrygon orinocensis. IAvH-P 12448, subadult male, 421 mm DW, from Orinoco river. A. dorsal and B. ventral views. USNM 233944a, adult female, 420 mm DW, from Orinoco river. C. dorsal and D. ventral views.

FIGURE 3 | Paratypes of Paratrygon orinocensis. IAvH-P 11940, juvenile male, 345 mm DW, from Orinoco river. A. dorsal and B. ventral views. USNM 233944b, juvenile male, 335 mm DW, from Orinoco river. C. dorsal and D. ventral views.

FIGURE 4 | Frontal view of eyes and spiracles of the three species of genus Paratrygon. Paratrygon orinocensis: A. IAvH-P 12449 (paratype), adult male, 573 mm DW, from Orinoco river. B. USNM 233944a (paratype). C. IAvH-P 11939 (holotype). Paratrygon parvaspina: D. IAvH-P 12447 (holotype), adult female, 450 mm DW, from Bita river. E. IAvH-P 12441 (paratype), juvenile female, 225 mm DW, from Tomo river. F. IAvH-P 12446 (paratype), juvenile male, 212 mm DW, from Tomo river. Paratrygon aiereba: G. MPEG uncatalogued, adult male, 578 mm DW, from Marajó island. H. MZUSP 14774, juvenile female, 256 mm DW, from Jutaí river. I. MUSM uncatalogued, juvenile male, 220 mm DW.

FIGURE 5 | Lateral view of spiracles and spiracles process of Paratrygon orinocensis. A. IAvH-P 12449 (paratype). B. IAvH-P 12448 (paratype). C. IAvH-P 11939 (holotype). D. IAvH-P 11942, juvenile female, 297 mm DW, from Orinoco river. E. IAvH-P 11938, juvenile male, 242 mm DW, from Orinoco river. F. IAvH-P 11941, juvenile female, 248 mm DW, from Orinoco river.

FIGURE 6 | Upper (above) and lower (below) teeth of Paratrygon orinocensis, IAvH-P 12449 (paratype). Scale bars = 5 mm.

FIGURE 7 | Dermal denticles in the central disc of Paratrygon orinocensis. A. dorsal view of dermal denticles of IAvH-P 12448. B. dorsal view of three dermal denticles of MZUSP 117220 (paratype), juvenile male, 299 mm DW, from Apure river, made by Scanning Electron Microscopy (SEM image). C. dorsal view of one central dermal denticle of MZUSP 117220 (SEM image). D. morphology detail of a central dermal denticle of MZUSP 117220 (SEM image) in dorsal view. E. lateral-dorsal view of one central dermal denticle of MZUSP 117220 (SEM image). F. lateral-dorsal view of one central dermal denticle showing the crown (MZUSP 117220, SEM image). ccp = central coronal plate, cr = crown, lcr = lateral coronal ridge.

FIGURE 9 | Posterior margin and tail’s basis dermal denticles of Paratrygon orinocensis, MZUSP 117220 (SEM images). A. dorsal-lateral views of three dermal denticles showing the two morphological types: one more similar with the central disc dermal denticles (left down corner), and other more smiliar with thorns of tail’s dorsal row (right down corner); left above a bud of a denticle. B. morphology detail of one pointed dermal denticle in lateral view. C. and D. lateral views of two dermal denticles. ccp = central coronal plate, lcp = lateral coronal ridge.

FIGURE 10 | Dorsal row of thorns on the tail of Paratrygon orinocensis. A. dorsal view of USNM 233944a (paratype). B. lateral view of USNM 233944a. C. dorsal view of IAvH-P 11939 (holotype). D. lateral-dorsal view of IAvH-P 11940 (paratype). E. dorsal view of IAvH-P 11943, juvenile female, 372 mm DW, from Orinoco river. F. dorsal view of IAvH-P 11938. G. dorsal view of IAvH-P 12444, juvenile female, 241 mm DW, from Orinoco river. H. dorsal view of ICN uncatalogued specimen, juvenile male, 240 mm DW.

FIGURE 11 | Dorsal view of caudal sting of Paratrygon orinocensis in six specimens. A. IAvH-P 11939 (holotype). B. IAvH-P 11940 (paratype). C. IAvH-P 11943. D. IAvH-P 12440, juvenile female, 249 mm DW, from Bita river. E. IAvH-P 12443. F. IAvH-P 12444.

FIGURE 12 | Ventral canals of lateral line system in Paratrygon orinocensis, MZUSP 117220 (paratype). A. distribution of all ventral canals. B. detail of the anterior central disc ventral canals. ang = angular component of hyomandibular canal, HMD = hyomandibular canal, IOC = infraorbital canal, JFC = junction of the four canals, jug = jugular component of hyomandibular canal, MNC = mandibular canal, NAS = nasal canal, nil = nasointernal loop, orb = orbitonasal component of supraorbital canal, pnc = prenasal component of nasal canal, pnl = prenasal loop, pst = posterior subpleural tubules, sbr = subrostral component of supraorbital canal, spc = subpleural component of hyomandibular canal, spl = subpleural loop, SPO = supraorbital canal, spt = subpleural tubule, sub = suborbital component of supraorbital canal, vS = vesicles of Savi.

FIGURE 13 | Radiographs of neurocranium and mandibular arch of Paratrygon orinocensis, upper views. A. USNM 233944b (paratype). B. MZUSP 117220 (paratype). ANT = antorbital cartilage, DLP = dorsolateral process, FPF = frontoparietal component of fontanelle, FSP = first segment of propterygium, HYO = hyomandibula, IS = internasal septum, LP = lateral process, MC = Meckel’s cartilage, NC = nasal capsule, PCF = precebral component of fontanelle, POP = postorbital process, PQ = palatoquadrate, PRO = propterygium, PRP = preorbital process, RPJ = rostral projection, SOC = supraorbital crest, SP = supraorbital process. Arrow indicates to the anterior portion of specimens.

FIGURE 14 | Radiographs of synarcual cartilage of Paratrygon orinocensis, upper views. A. USNM 233944b (paratype). B. MZUSP 117220 (paratype). AVC = anterior ventral condyle, DMC = dorsomedial crest, DS = dorsal socket, LS = lateral stay, PVC = posterior ventral condyle, SNC = spinal nerve canal, SNF = spinal nerve foramen. Arrow indicates to the anterior portion of specimens.

FIGURE 15 | Radiographs of scapulocoracoid of Paratrygon orinocensis, upper views. A. USNM 233944b (paratype). B. MZUSP 117220 (paratype). CB = coracoid bar, DLC = dorsolateral crest, MSC = mesocondyle, MTC = metacondyle, PC = procondyle, SCP = scapular process. Arrow indicates to the anterior portion of specimens.

FIGURE 16 | Radiographs of basal elements of pectoral fin of Paratrygon orinocensis, USNM 233944b (paratype), upper views. A. propterygium region. B. mesopterygium region. C. metapterygium region. ANT = antorbital cartilage, FSP = first segment of propterygium, JMR = junction of medial radials, MSP = mesopterygium, MTP = metapterygium, PPT = propterygium, PSM = posterior segments of metapterygium, SAS = small articulation surface. Arrow indicates to the anterior portion of specimens.

FIGURE 17 | Radiographs of pelvic girdle of Paratrygon orinocensis, upper views. A. USNM 233944b (paratype). B. MZUSP 117220 (paratype). IP = iliac process, ISP = ischial process, LPP = lateral prepelvic process, OF = obturator foramen, PB = puboischiadic bar. Arrow indicates to the anterior portion of specimens.

FIGURE 19 | Holotype and paratype of Paratrygon parvaspina. Holotype, IAvH-P 12447, adult female, 450 mm DW, from Bita river. A. dorsal and B. ventral views. Paratype, IAvH-P 12441, juvenile female, 255 mm DW, from Tomo river. C. dorsal and D. ventral views.

FIGURE 20 | Paratypes of Paratrygon parvaspina. IAvH-P 12446, juvenile male, 212 mm DW, from Tomo river. A. dorsal and B. ventral views. MZUSP 117836, juvenile female, 266 mm DW, from Orinoco river. C. dorsal and D. ventral views.

FIGURE 21 | Lateral view of spiracles and spiracles process of Paratrygon parvaspina. A. IAvH-P 4684, adult female, 345 mm DW, from Tomo river. B. IAvH-P 12441 (paratype). C. IAvH-P 12446 (paratype). D. MZUSP 117836 (paratype).

FIGURE 23 | Dorsal view and details of central disc dermal denticles of Paratrygon parvaspina, MZUSP 117836 (paratype) (SEM images). A. and B. dorsal view of some denticles. C. dorsal and D. lateral details of central dermal denticles. ccp = central coronal plate, lcr = lateral coronal ridge.

FIGURE 24 | Dorsal and lateral rows of thorns in Paratrygon parvaspina. A. and B. IAvH-P 12447 (holotype). C. IAvH-P 4684. D. detail of dorsal pointed spines on the tail of IAvH-P 12441 (paratype). E. IAvH-P 12446 (paratype). F. MZUSP 117836 (paratype).

FIGURE 25 | Dorsal view of caudal stings of Paratrygon parvaspina. A. IAvH-P 4684. B. IAvH-P 12441 (paratype). C. IAvH-P 12446 (paratype). D. MZUSP 117836 (paratype).

FIGURE 26 | Ventral canals of lateral line system in Paratrygon parvaspina, IAvH-P 12446 (paratype). A. distribution of all ventral canals. B. detail of the anterior central disc ventral canals. Abbreviations see Fig. 12.

FIGURE 27 | Radiograph of neurocranium and mandibular arch of Paratrygon parvaspina, MZUSP 117836 (paratype), upper view. Abbreviations see Fig. 13. Arrow indicates to the anterior portion of specimen.

FIGURE 28 | Radiograph of synarcual cartilage of Paratrygon parvaspina, MZUSP 117836 (paratype), upper view. Abbreviations see Fig. 14. Arrow indicates to the anterior portion of specimen.

FIGURE 29 | Radiograph of scapulocoracoid of Paratrygon parvaspina, MZUSP 117836 (paratype), upper view. Abbreviations see Fig. 15. Arrow indicates to the anterior portion of specimen.

FIGURE 30 | Radiographs of basal elements of pectoral fin of Paratrygon parvaspina, MZUSP 117836 (paratype), upper view. Abbreviations see Fig. 16. Arrow indicates to the anterior portion of specimen. A. Propterygium region. B. Mesopterygium region. C. Metapterygium region.

FIGURE 31 | Radiograph of pelvic girdle of Paratrygon parvaspina, MZUSP 117836 (paratype), upper view. Abbreviations see Fig. 17. Arrow indicates to the anterior portion of specimen.

FIGURE 33 | Neotype of Paratrygon aiereba, MZUSP 117155, adult male, 603 mm DW, from Marajó bay. A. dorsal and B. ventral views.

FIGURE 34 | Paratrygon aiereba, dorsal view of the specimen MZUSP 104896, adult female, 560 mm DW, from Javari river. Note the concavity in the anterior margin of the disc.

FIGURE 35 | Lateral view of spiracles and spiracles process of Paratrygon aiereba. A. MPEG uncatalogued, adult female, 786 mm DW, from Marajó island. B. AMNH 59878, subadult male, 383 mm DW, from Itenez river. C. IAvH-P 11929, juvenile male, 366 mm DW, from Putumayo river. D. MNHN A.2269, juvenile male, 285 mm DW, from Solimões river. E. MUSM 1389, neonate female, 204 mm DW. F. MZUSP 101015, neonate female, 150 mm DW, from Breu river.

FIGURE 36 | Upper teeth of Paratrygon aiereba. A. MZUSP 104895, adult female, 590 mm DW, from Javari river. B. MNHN A.1019, juvenile female, 324 mm DW, from Solimões river. C. MNHN A.2269. Scale bars, A. = 5 mm, B. and C. = 2 mm.

FIGURE 37 | Upper (above) and lower (below) teeth of Paratrygon aiereba, MNHN A.2269. Scale bars = 2 mm.

FIGURE 38 | Non-type specimen of Paratrygon aiereba, MPEG uncatalogued, adult female, 786 mm DW, from Marajó island. A. dorsal and B. ventral views.

FIGURE 39 | Non-types of Paratrygon aiereba. MPEG uncatalogued, adult male, 681 mm DW, from Marajó island. A. dorsal and B. ventral views. MZUSP 104029, juvenile male, 436 mm DW, from Juruá river. C. dorsal and D. ventral views.

FIGURE 40 | Non-types of Paratrygon aiereba. IAvH-P 11927, juvenile male, 408 mm DW, from Putumayo river. A. dorsal and B. ventral views. IIAP uncatalogued, juvenile female, 208 mm DW, from Napo river. C. dorsal and D. ventral views.

FIGURE 41 | Dorsal view of dermal denticles in central disc of Paratrygon aiereba (SEM images). A. INPA 1331, juvenile female, 255 mm DW, from Solimões river. B. MUSM 47105, juvenile male, 214 mm DW, from Uribamba river. C. MZUSP 117831, neonate female, 200 mm DW, from Nanay river.

FIGURE 42 | Details of dermal denticles in central disc of Paratrygon aiereba (SEM images) in dorsal view. A. MZUSP 103896, adult male, 508 mm DW, from Tapajós river. B. and C. INPA 1331.D. and E. MUSM 47105. F. MZUSP 117831. ccp = central coronal plate, lcr = lateral coronal ridge.

FIGURE 43 | Dermal denticles in the disc margins of Paratrygon aiereba, MZUSP 103896 (SEM images). A. dorsal view of anterior margin denticles. B. dorsal view of lateral margin denticles. C. lateral view of posterior margins denticles.

FIGURE 44 | Details of dermal denticles in the disc margins of Paratrygon aiereba, MZUSP 103896 (SEM images). A. dorsal view of anterior margin denticles. B. dorsal and C. lateral detail of lateral margin denticle. D. lateral view of a posterior margin denticle. E. dorsal and F. lateral detail of a thorn in the posterior margin of disc. bp = basal plate, ccp = central coronal plate, cr = crown, lcr = lateral coronal ridge.

FIGURE 45 | Details of dermal denticles and thorns in the tail basis of Paratrygon aiereba, MZUSP 103896 (SEM images). A. dermal denticles and one thorn (right superior corner) in the tail basis of MZUSP 103896. B. detail of pointed dermal denticles of left superior corner in the Fig. 45a. image. ccp = central coronal plate, lcr = lateral coronal ridge.

FIGURE 46 | Dorsal view of dorsal and lateral rows of thorns in Paratrygon aiereba. A. MZUSP 117155 (neotype). B. MUSM 9423, juvenile male, 428 mm DW, from Las Piedras river. C. IAvH-P 11927. D. MUSM 1389, juvenile male, 207 mm DW. E. MZUSP 14772, juvenile female, 221 mm DW, from Ucayali river. F. MZUSP 101015.

FIGURE 47 | Dorsal view of caudal stings of Paratrygon aiereba. A. MPEG uncatalogued, adult male, 681 mm DW. B. MZUSP 103907, adult male, 606 mm DW, from Tapajós river. C. IAvH-P 11894, juvenile female, 472 mm DW. D. IAvH-P 11937, juvenile male, 280 mm DW, from Putumayo river. E. MNHN A.2289. F. USNM 264005, juvenile male, 184 mm DW, from Tambopata river.

FIGURE 48 | Ventral canals of lateral line system in Paratrygon aiereba, MZUSP 117831. A. distribution of all ventral canals. B. detail of the anterior central disc ventral canals. Abbreviations see Fig. 12.

FIGURE 49 | Neurocranium of Paratrygon aiereba, MZUSP 103896, in dorsal, ventral, lateral, caudal and frontal views (from top to bottom, and from left to right). ACVF = anterior cerebral vein foramen, AOC = antorbital cartilage condyle, AS = articular surface, ELF = endolymphatic foramina, ESAF = efferent spiracular artery foramen, FCF = frontoparietal component of fontanelle, FM = foramen magnum, FPC = foramen of preorbital canal, ICAF = internal carotid artery foramina, HF = hyomandibular facet, IVF = interorbital vein foramen, IS = internasal septum, LC = lateral comissure, NC = nasal capsule, NSC = nasal cartilage, OC = occipital condyle, OFS = orbital fissure, OP = optic pedicel, PCF = precerebral component of fontanelle, PLF = perilymphatic foramina, POP = postorbital process, PRP = preorbital process, RPJ = rostral projection, SOC = supraorbital crest, SP = supraorbital process, II = optic nerve foramen, III = oculomotor nerve foramen, VII = hyomandibular ramus of facial nerve foramen, IX = glossopharyngeal nerve foramen, X = vagus nerve foramen, LbX = lateralis branch of vagus nerve foramen.

FIGURE 50 | Radiographs of neurocranium and mandibular arch of Paratrygon aiereba, upper views. A. ZSM 34500, neonate female, 204 mm DW, from San Martin river. B. USNM 264005. Abbreviations see Fig. 13. Arrow indicates to the anterior portion of specimens.

FIGURE 51 | Mandibular and hyoid archs of Paratrygon aiereba, MZUSP 103896, in frontal and ventral views (from top to bottom). L = Hyomandibular-Meckelian ligament, VLP = ventrolateral process. Other abbreviations see Fig. 13.

FIGURE 52 | Synarcual cartilage of Paratrygon aiereba, MZUSP 103896, in dorsal, ventral, lateral, caudal and frontal views (from top to bottom, and from left to right). SLP = small lateral projection. Other abbreviations see Fig. 14.

FIGURE 53 | Scapulocoracoid of Paratrygon aiereba, MZUSP 103896, in dorsal and ventral views (from top to bottom). ADF = anterodorsal fenestra, AVF = anteroventral fenestra, PDF = postdorsal fenestra, PVF = postventral fenestra, LEF = lateral external face. Other abbreviations see Fig. 15.

FIGURE 54 | Radiograph of scapulocoracoid of Paratrygon aiereba, ZSM 34500, upper view. Abbreviations see Fig. 15. Arrow indicates to the anterior portion of specimen.

FIGURE 55 | Radiographs of basal elements of pectoral fin of Paratrygon aiereba, ZSM 34500, upper views. Abbreviations see Fig. 16. Arrow indicates to the anterior portion of specimen. A. Propterygium region. B. Mesopterygium region. C. Metapterygium region.

FIGURE 56 | Pelvic girdle and fins of Paratrygon aiereba, MZUSP 103896, in dorsal and ventral views (from top to bottom). PPP = prepelvic process, SF = small foramen. Other abbreviations see Fig. 17.

FIGURE 57 | Radiograph of pelvic girdle of Paratrygon aiereba, ZSM 34500, upper view. Abbreviations see Fig. 17. Arrow indicates to the anterior portion of specimen.

FIGURE 58 | Skeletal elements of right clasper of Paratrygon aiereba, MZUSP 103896, in dorsal, ventral, ventral without dorsal terminal 1 (top, left to right), and (below, left to right) dorsal and ventral views of dorsal terminal 1. AT1 = acessory terminal 1, AX = axial cartilage, B1 = basal 1, B2 = basal 2, β = beta cartilage, DM = dorsal marginal cartilage, DT1 = dorsal terminal 1, DT2 = dorsal terminal 2, VM = ventral marginal cartilage.

FIGURE 59 | Distribution of the three species of genus Paratrygon throughout the Amazon and Orinoco basins. Paratrygon aiereba (green) is restricted to Amazon basin, and Paratrygon orinocensis (red) and Paratrygon parvaspina (blue) are restricted and sympatric in the Orinoco basin. Star = neotype specimen (MZUSP 117155) locality.