Paratrygon orinocensis, Loboda & Lasso & Rosa & Carvalho, 2021

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 : 6-25

Paratrygon orinocensis , new species urn:lsid:zoobank.org:act:86CC950D-66B1-44C2-B7D1-DC8BF88A089B

( Figs. 1‒17 , Tabs. 1‒2)

Disceus thayeri . —Fernández-Yépez, 1949:1‒2 (brief morphological description; occurrence in Orinoco basin).

Paratrygon aiereba . —Lasso et al., 1996:39‒47, 49, figs. 3‒5, 9, 11, 12, (morphometry, weight, sexual maturity, pregnancy, size of litter, feeding habits, occurrence in Caño Guaritico, Apure River subbasin, Venezuela). —Barbarino, Lasso, 2005:93‒107, figs. 1, 4‒10 (occurrence in Apure River, biological data, habitat, feeding habits, pregnancy, size of litter, morphometry, weight, sexual maturity, fishing data, commercialization). —Barbarino, Lasso, 2009:24‒31, figs. 1‒3 (commercialization, fishing data, habitat, morphometry, weight, reproduction data, sexual maturity). —Lasso et al., 2009:128 (occurrence in delta of Orinoco River). —Lasso et al., 2011:87‒88, 469, 493, fig. 61 (brief morphological descipition; feeding habits, biology, distribution, fishing data, species list of Orinoco River delta). —Lasso, Sánchez-Duarte, 2012: 23, 42, 132‒134, 308, 314, 318 (list of endangered species of fish in Colombia, brief morphological description, distribution, ecology, conservation). —Muñoz-Osorio, Mejía-Falla, 2013:189‒191 (occurrence in Bita River, brief morphological description, size of litter, conservation). —Lasso et al., 2013:137‒150, figs. 4‒6, 9, 12‒13 (brief morphological description, conservation, distribution, biological data, fishing data). —García-Villamil et al., 2013:290‒293, figs. 5‒6 (molecular systematics, phylogenetic discussion). —Sánchez-Duarte et al., 2016: 319, 321‒322 (specimen trade); —García et al., 2016:4481‒4482 (molecular systematics, phylogenetic discussion).

Paratrygon sp. —García et al., 2016:4484‒4489, fig. 2, p. 4484, fig. 3, p. 4485, fig. 4, p. 4485, fig. 5, p. 4486 (molecular systematics, phylogenetic discussion).

Paratrygon sp.1 . —Loboda, 2016: vol.1. vii-viii, 33, 60‒61, 75, 87, 97‒113, 117, 119‒123, 126‒127, 142, 156, 190‒192, 229‒236, vol.2. xv-xvi, 76‒90, figs. 105‒126, (morphometry, morphological description, taxonomic revision, diagnosis, previous misidentifications, distribution).

Holotype. IAvH-P 11939, female, 286 mm DW, Colombia, Vichada, Puerto Carreño, río Orinoco, locality of Piedra casa Bojonawi , 06°06’07.5’’N 67°29’11.9’’W, 1 Dec 2013, C. Lasso & M. A. Morales-Betancourt.

Paratypes. (10 specimens). IAvH-P 12449, male, 573 mm DW, Colombia, Vichada, Puerto Carreño, río Orinoco, locality of playa Reserva Natural Bojonawi , 06°06’07.2’’N 67’29’11.9’’W, 6 May 2014, C. Lasso & M. A. Morales-Betancourt. IAvH-P 12448, male, 421 mm DW, same data as anterior. IAvH-P 11940, male, 345 mm DW, Colombia, Vichada, Puerto Carreño, río Orinoco , locality of Piedra casa Bojonawi, 06°06’07.5’’N 67°29’11.9’’W, 28 Jun 2013, C. Lasso & M. A. Morales-Betancourt. IAvH-P 12439, female, 270 mm DW, Colombia, Vichada, Puerto Carreño, río Bita (tributary of río Orinoco ), 06°09’10.7’’N 67°35’45.1’’W, 1 Jan 2014, C. Lasso & M. A. Morales-Betancourt. MZUSP 117220 , male, 299 mm DW, Venezuela, Apure, Munoz, Rio Apure (tributary of río Orinoco ), Guaritico stream, 07°53’32.5’’N 68°52’49.8’’W, 23 Feb 2011, F. P. L. Marques & L. Sanchez. USNM 233944 , 5 , 3 females and 2 males, 245‒420 mm DW, Venezuela, Delta Amacuro, Guayana , río Orinoco , locality of Cabrian , between Puerto Ordaz and Los barrancos de Fajardo, 08°34’12’’N 62°15’48’’W, 11 Nov 1979, E. C. Marsh .

Non-types. (11 specimens). IAvH-P 11943, female, 372 mm DW, Colombia, Vichada , Puerto Carreño, río Orinoco, below Natural Park of Bojonawi , 06°05’51’’N 67°29’04.4’’W, 11 Oct 2013, C. Lasso. IAvH-P 11942, female, 297 mm DW, same data as anterior. IAvH-P 12440, female, 249 mm DW, Colombia, Vichada , Puerto Carreño, río Bita (tributary of Río Orinoco ), 06°09’10.7’’N 67°35’45.1’’W, 1 Jan 2014, C. Lasso. IAvH-P 11941, female, 248 mm DW, Colombia, Vichada , Puerto Carreño, río Orinoco, locality of Natural Reserve Bojonawi , 06°06’07.5’’N 67°29’11.9’’W, 12 Jun 2013, C. Lasso & M. A. Morales-Betancourt. IAvH-P 12443, female, 245 mm DW, Colombia, Vichada , Puerto Carreño, locality of Playa Caricari , 06°05’46.3’’N 67°29’04.7’’W, 28 Feb 2014, C. Lasso & M. A. Morales-Betancourt. IAvH-P 11938, male, 242 mm DW, same data as IAvH-P 11943. IAvH-P 12444, female, 241 mm DW, same data as IAvH-P 11943. IAvH-P 12445, female, 236 mm DW, Colombia, Vichada , Puerto Carreño, locality of Playa Caricari , 06°05’46.3’’N 67°29’04.7’’W, 5 Mar 2014, C. Lasso & M. A. Morales-Betancourt. IAvH-P 12442, 2, 1 female and 1 male, 174‒178 mm DW, Colombia, Vichada , Puerto Carreño, río Orinoco, below Natural Reserve Bojonawi , 06°05’51’’N 67°29’04.4’’W, 11 Oct 2013, C. Lasso & M. A. Morales-Betancourt. IAvH-P uncatalogued, 382 mm DW, Colombia . ICN uncatalogued, 4, 2 females and 2 males, 209‒355 mm DW, Colombia .

Diagnosis. Paratrygon orinocensis is distinguished from congeners by a combination of characters. Paratrygon orinocensis without lateral rows of thorns on tail (vs. P. aiereba and Paratrygon parvaspina with lateral rows of thorns on tail). Dermal denticles on the central region of the disc of P. orinocensis have wide and high crowns, presenting a central coronal plate very similar morphologically to its lateral coronal ridges, which in adults can be more than 12 (vs. P. aiereba and P. parvaspina that have small dermal denticles on the central disc, with high and narrow crowns presenting higher and pointed central coronal plates surrounded by minor, pointed or rounded lateral coronal ridges, which in turn vary between three and six). Paratrygon orinocensis has 22‒35/20‒29 teeth (vs. P. aiereba with 16‒26/14‒20, and P. parvaspina with 31/19‒22); central teeth of P. orinocensis with more developed and high cusps than P. aiereba and P. parvaspina . In P. orinocensis the spiracles are small and triangular, with mean length 5.6% DW [4.5‒7.9% DW] (vs. quadrangular and larger spiracles in P. aiereba , with mean length 6% DW [4.4‒11.6% DW], and very small and quadrangular spiracles in P. parvaspina with mean length 5.2% DW [4.9‒5.8% DW]. Paratrygon orinocensis has a short and straight spiracular process with developed and numerous dermal denticles (vs. larger and knob shaped spiracular process that almost covers the spiracle aperture and with some small dermal denticles in P. aiereba , and an extremely short and reduced spiracular process in P. parvaspina that is more perceptible in adult specimens, with few dermal denticles). Paratrygon orinocensis has a minute rostral projection (vs. P. aiereba that has a relatively large rostral projection, and P. parvaspina that has a large and circular rostral projection).

Description. For general aspect of Paratrygon orinocensis see Figs. 1‒3 , for morphological characters examined see Figs. 8‒17 . Measurements and counts are shown in Tabs. 1‒2, and S1 ‒ S2. Paratrygon orinocensis presents a more rounded than subcircular disc, with mean disc length 107.7% DW [104.4‒112.8%]. Anterior margin of disc with a prominent concavity at its medial portion, being clearly visible and pronounced ( Figs. 1‒3, S1 ). Disc also relatively short in comparison with total length, with mean of distance between anterior margin of disc and cloaca 85.6% DW [81.5‒91.7% DW].

Holotype Paratrygon orinocensis Mean SD Range N IAvH-P 11939

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

Total length 584 204.2 551.2 191.0 124.5 43.3 287 866 115.7 283.7 26

Disc length 305 106.6 322.9 107.7 94.3 2.2 190 634 104.4 112.8 26

Disc width 286 100.0 299.8 100.0 86.0 0.0 174 573 100.0 100.0 26

Interorbital distance 28 9.8 29.2 9.9 7.4 1.0 21 56 8.6 12.9 26

Interespiracular distance 43 15.0 46.6 15.8 11.3 1.6 36 86 13.8 20.7 26

Eye length 6 2.1 5.5 1.9 1.0 0.4 4 7 1.2 2.8 26

Spiracle length 16 5.6 16.6 5.6 4.4 0.7 12 30 4.5 7.9 26

Preorbital length 86 30.1 90.2 29.9 28.4 1.5 49 181 26.3 32.1 25

Prenasal length 77 26.9 82.6 27.5 23.4 1.2 44 150 24.7 30.3 26

Head small, with relatively short interorbital and interspiracular distances (means, respectively, 9.9% DW and 15.8% DW). Eyes small (mean diameter 1.9% DW) and slightly pedunculated. Spiracles positioned laterally in relation to eyes ( Figs. 4A‒C , 5 ), greater than eyes (mean length 5.6% DW), and oval-triangular in shape ( Fig. 5 ). Spiracular process short, straight and covering part of posterior portion of spiracular aperture, presenting developed dermal denticles ( Fig. 5 ). Preorbital, prenasal and preoral distances with means, respectively, 29.9% DW, 27.5% DW, and 30.9% DW. Internasal distance with mean of 8.3% DW, and mouth width with mean of 10% DW. Teeth triangular, large, cuspidate, arranged in quincunx in both jaws, presenting few differences in size between teeth from central and lateral rows, but central teeth slightly greater. Adult specimens possess pointed and high cusps, with teeth of central rows and in the lower jaw more developed ( Fig. 6 ). Tooth rows in adults 22‒35/20‒29, with exposed teeth in symphysis 2‒4/3‒4 ( Tab. 2).

Branchial basket rectangular, with mean distance between first pair of gill slits (anterior portion of branchial basket) 20.1% DW, and mean distance between fifth pair of gill slits (posterior portion) 17.3% DW. Branchial basket with mean distance between first and fifth gill slits 10.9% DW. Pelvic fins triangular and dorsally covered by the disc ( Figs. 1B , 2B, D , 3B, D; S 1B, D ), with mean length of anterior margin 16.9% DW. Distances between distal portions of pelvic fins, and between the axils of pectoral and pelvic fins, with means respectively of 38.7 and 3.8% DW.

Clasper short, robust and cylindrical with rounded tips in adult and subadult specimens. Claspers present significant increase in size from neonates to adults: ranges of external and internal lengths in neonates and juveniles, respectively, 2.1 to 3%, and 7.1 to 8.7% DW, in subadult specimen, respectively, 3.6 and 9.5% DW, and in adult specimen analyzed 8.7 and 17.3% DW. Pseudosiphon and ventral pseudosiphon also grow from juveniles to adults: ranges of lengths of pseudosiphon and ventral pseudosiphon, respectively, 0.6 to 1.2% and 2.9 to 3.3% DW in neonates and juveniles, and 1.4% and 7.3% DW in adult specimen (see S2 for more details).

Tail very long compared to the P. aiereba and P. parvaspina , with a short base, and a pre-caudal sting portion narrow; post- caudal sting portion extremely long and filiform ( Figs. 1‒3; S1 ). Mean of distance from cloaca to caudal sting insertion (pre-caudal sting portion of tail) 23.5% DW ( Tab. 1). Mean tail width 6.5% DW, presenting a proportional decrease in size from juveniles to adults: range in neonates from 7.2 to 9% DW, in juveniles from 5.1 to 7.3% DW, in subadult analyzed 6.4% DW, and in adults from 4.2 to 5.7% DW. Mean distance from cloaca to tail tip 100.7% DW, also with a proportional decrease from juveniles to adults: range in neonates 164.1 to 189.3% DW, in juveniles 26.2 to 150% DW, in subadult analyzed 66.3% DW, and in adults 27.1 to 59% DW ( Tabs. 1‒2; S2). Dorsal and ventral tail folds present but poorly developed, more easily recognizable in the portion immediately after caudal sting; some specimens with a medial ventral groove in the tail from its base to the origin of ventral fold.

Squamation. Dermal denticles present on entire dorsal region of disc and tail. Denticles greater in central region of disc, more concentrated and more visible than denticles on disc margins. Denticles on tail between tail base and caudal sting insertion are bigger than denticles located from caudal sting insertion to the tip of tail.

Dermal denticles on central disc region with diameters from 1‒2 mm ( Fig. 7 ). These denticles present a wide and high crown (cr), with a central coronal plate (ccp) morphologically similar to the lateral coronal ridges (lcr) that surround it ( Fig. 7 ). Dermal denticles on central region of disc generally with four to six lateral coronal ridges in juvenile specimens; subadults and adults present two rows of lcr surrounding the central coronal plate, with more than a dozen ridges in total. Dermal denticles on anterior margin of disc with similar morphology to central disc, however with fewer lcr: just one row of lcr surrounding ccp, and number of lateral ridges between three to six ( Fig. 8 ). Two morphological types of dermal denticles on tail base ( Fig. 9A ): one very similar to denticles on anterior margin of disc and central disc but with fewer lcr ( Figs. 9C‒D ), and an another type similar to the thorns on tail (but much smaller), with just a very high and developed ccp in its crown ( Fig. 9B ).

One to two dorsal rows of developed thorns with broad base present on tail of adult specimens; dorsal rows originate just after base of tail and extend almost to base of caudal sting ( Figs. 10A‒B ). Subadults and larger juvenile specimens generally with just one dorsal row of thorns, with few specimens presenting duplicate rows near the caudal sting base; thorns in these specimens also high and with broad base, slightly larger near caudal sting region ( Figs. 10C‒E ). Majority of juvenile specimens with just a part of the single dorsal row with small thorns, with a slightly larger thorns near the caudal sting ( Figs. 10F‒G ). Neonates with a single poorly developed row of minute thorns at tail base ( Fig. 10H ).

Caudal sting with mean length 12% DW [6.7 and 15.3% DW]; caudal sting mean width 1% DW [0.6 and 1.7% DW] ( Tab. 1). Subadult and larger juvenile specimens with one or two well developed caudal stings, with lateral serrations distributed along their entire length or just on their terminal half; lateral serrations more developed in the terminal portion of the sting ( Figs. 11A‒C ). Caudal stings without a dorsal medial groove. Younger juveniles and neonates with caudal stings similiar to subadults, however with reduced number of serrations and only on terminal half of sting ( Figs. 11D‒F ).

Lateral line. Four principal ventral lateral line canals (hyomandibular, HMD; infraorbital, IOC; supraorbital, SPO ; and nasal, NAS) connect at a unique point named junction of the four canals ( JFC), located laterally to mouth ( Fig. 12 ). Hyomandibular canal ( HMD) extends posteriorly through its angular component (ang). After the angular component, the canal continues to descend, contouring externally the branchial basket toward the central region of the disc to the scapulocoracoid bar, where it is curved posteriorly forming its jugular component (jug). Close to the pelvic girdle, the hyomandibular canal makes a broad loop, the subpleural loop (spl), with two to five small posterior subpleural tubules (pst) that continue posteriorly; posteriormost tubule slightly larger than others. From the subpleural loop, the canal continues anteriorly as a big curve to the scapulocoracoid bar, where it turns again externally in direction to anterior margin of the disc, forming the subpleural component (spc) of the hyomandibular canal. Subpleural component extends anteriorly toward anterolateral margin of disc, where between the levels of mouth and branchial basket the first subpleural tubule (spt) detaches from the hyomandibular canal, extending toward disc margin. Subpleural component reaches disc margin at the level just anterior to the nostrils, and continues anteriorly very close to disc margin to connect with the nasal canal ( NAS) in the mid region of anterior disc margin (not shown in Fig. 12 ). Dozens of small subpleural tubules connected to subpleural component of hyomandibular canal present on anterior disc margin, the posteriormost tubule longer than others ( Fig. 12 ).

From the JFC the infraorbital canal ( IOC) extends laterally, slightly curves anteriorly, and subdivides forming the ramifications of the suborbital component (sub). Suborbital component of infraorbital canal presents a honeycomb pattern; individual honeycombs greater posteriorly, smaller close to the subpleural component (spc) of hyomandibular canal and the anterior margin of the disc. Ramifications of the subrbital component connected in at least two points with the prenasal component (pnc) of nasal canal near the mid anterior margin of disc region. Supraorbital canal ( SPO ) extends medially and anteriorly from JFC, forming its orbitonasal component (orb) that curves posteriorly anterior to nostrils forming the prenasal loop (pnl). From the prenasal loop, the canal extends posteriorly in direction to the nostrils, forming the more broadly curved nasointernal loop (nil). From the nil, the supraorbital canal extends anteriorly to the level of the pnl, where it connects to the prenasal component (pnc) of nasal canal, forming in this part its subrostral component (sbr) with close to a dozen vesicles of Savi (vS) ( Fig. 12 ).

Nasal canal ( NAS) extends anteromedially at a 45° angle from the JFC to next to the nostril, where it penetrates the disc; the canal emerges between the nostrils, making a small anterior curve and ascending straight to the anterior margin of disc, forming the prenasal component (pnc). Prenasal component connects with sbr of SPO next to nostrils, and with sub of IOC and spc of HMD next to anterior margin of disc. Mandibular canal ( MNC) extends lateroexternally from median line of body very close to mouth, contouring posteriorly the adductor mandibulae muscle until close to the first gill slit, where ir penetrates the body ( Fig. 12 ).

Skeleton. Meristic counts of vertebrae and pectoral and pelvic radials are shown in Tab. 2. In dorsal view, neurocranium presents a “ T ” format, widest anteriorly at the nasal capsules ( NC). Rostral projection ( RPJ) minute and almost imperceptible in the anteriormost part of the neurocranium between the nasal capsules ( Fig. 13 ). Nasal capsules oval, separated by a large internasal septum (IS), anteriorly surrounded by the first segment of propterygium ( FSP) and laterally connected with propterygium ( PRO ) through a small and triangular antorbital cartilage ( ANT ). Preorbital process ( PRP) posterodorsal to the nasal capsules, small, triangular, and not exceeding laterally the limits of nasal capsules ( Fig. 13 ). Supraorbital crest ( SOC) posterior to the preorbital process and extending dorsolaterally above all orbital region. Posterior portion of SOC with a small supraorbital process (SP) and a short but more developed postorbital process ( POP). Roof of neurocranium with a large and spoon shaped fontanelle, from nasal capsules to posterior part of orbital region. Fontanelle divided into two components: an anterior, rounded and broad precerebral component ( PCF), and a posterior, long, narrow and “8”-shaped frontoparietal component ( FPF) ( Fig. 13 ).

Mandibular arch laterally extended, with long and proximally arched palatoquadrate ( PQ) and Meckel’s cartilage ( MC). Palatoquadrate not too slender, arched medially, with a dorsolateral process ( DLP) close to its articulation with Meckel’s cartilage. Meckel’s cartilage with a pronounced arch in its proximal portion where it articulates with palatoquadrate and hyomandibula; proximal portion more robust than distal portion. MC with long lateral process ( LP) that reaches the DLP of palatoquadrate ( Fig. 13 ). Hyomandibula ( HYO) long, slender and straight, with its distal portion anteriorly curved. This portion articulates with the posteroexternal corner of MC through the hyomandibular-Meckelian ligament (not shown in Fig. 13 ).

In dorsal view, synarcual cartilage with length similar to neurocranium and expanded laterally throughout its length, mainly posteriorly where it articulates with scapulocoracoid bar ( Fig. 14 ). Dorsomedial crest ( DMC) located over spinal nerve canal ( SNC); SNC tubular. Dozens of spinal nerve foramina ( SNF) present on lateral walls of SNC at its basal portion ( Fig. 14 ). Posterior region of synarcual cartilage expanded laterally with three areas of contact with the scapulocoracoid bar: dorsal socket (DS) broad and with a slightly deep recess, and two ventral condyles, anterior ventral condyle ( AVC) and posterior ventral condyle ( PVC), with anterior condyle slightly larger than posterior condyle. From this region to mid portion of SNC a lateral stay ( LS) projects laterally, almost reaching the widest point of synarcual cartilage (located at its articulation with scapulocoracoid bar) ( Fig. 14 ).

Scapulocoracoid (shoulder girdle) composed of coracoid bar ( CB) slightly arched in both anterior and posterior faces. Anterior surface with a more pronounced curvature than posterior aspect, and with a broad and triangular scapular process ( SCP) articulating with the synarcual cartilage ( Fig. 15 ). Scapular process with a dorsolateral crest ( DLC) which projects anterolaterally from the region next to its articulation with the synarcual cartilage, and projects laterally beyond the mesocondyle ( Fig. 15 ). In dorsal view, three condyles of SCP contact the basal elements of the pectoral fin. The procondyle (PC) in the anterolateral extremity of SCP, constituting the major condyle of SCP, articulates with the most anterior portion of the propterygium base and presents an inverted “L” shape ( Fig. 15 ). The mesocondyle ( MSC) in the posterolateral face of SCP next to the metacondyle articulates with the mesopterygium and is the most laterally projected condyle of SCP. The metacondyle ( MTC) also in the posterolateral extremity of SCP, very next to MSC, articulates with the metapterygium ( Fig. 15 ).

The propterygium ( PPT) articulates with PC at its anterior portion but posteriorly contacts the lateroexternal face of SCP between PC and MSC. The mesopterygium ( MSP) articulates solely with MSC, and the metapterygium ( MTP) articulates only with MTC ( Fig. 16 ). Propterygium robust and arched, is the most developed basal element of the pectoral fin, with its posterior extremity broader than the anterior and curved and more slender distally ( Fig. 16A ). Anterior extremity of PPT articulates at its internal face with the antorbital cartilage ( ANT ), and its anterior tip with the first segment of propterygium ( FSP). FSP one-fourth of PPT length, contouring externally the anterior portion of nasal capsules ( NC) and articulating anteriorly with the first two rays of the propterygium. Posterior portion of PPT, where it articulates with scapulocoracoid, presents an inverted “L” shape, with its anterior part contacting the procondyle and the rest contacting the lateral external face ( LEF) of SCP to next to the mesocondyle; this portion of PPT also contacts mesopterygium in two points: one on its external face near the tip, and other in the posterior extremity through a small articular surface ( SAS) ( Figs. 16A‒B ). Mesopterygium with length similar or slightly smaller than scapular process in anteroposterior aspect, being the smallest basal element of pectoral fin ( Figs. 15 , 16B ). Anterior portion of MSP anterioly detached and more slender than posterior part. Posterior portion more developed with its internal face articulating with MSC and presenting anteriorly a pronounced concavity which contacts propterygium. Both extremities, anterior and posterior, contact respectively propterygium and metapterygium, and median radials ( JMR) of pectoral fin ( Fig. 16B ). Metapterygium long, arched and slender, with its proximal portion about as wide or slightly less than half of width of proximal portion of PPT ( Fig. 16B ). Anterior portion of MTP slightly more robust than the rest, being articulated with MTC at its anterior tip, and contacting mesopterygium and JMR on its external anterior face. Posterior portion of MTP segmented in two or three posterior segments ( PSM) at the level of pelvic girdle, with its posterior segments sucessively smaller than anterior segments ( Fig. 16C ).

Pelvic girdle composed of arched puboischiadic bar (PB) which possesses a very long prepelvic process on its anteromedial portion (not shown in Fig. 17 ). Puboischiadic bar highly arched, with its anterior portion more inclined and its posterior portion highly curved. Lateral extremities of PB possess two ventral processes and one dorsal, and three pairs of dorsoventrally situated obturator foramina ( OF) ( Fig. 17 ). Iliac process ( IP) short, with same dimensions or slightly longer than ischial process, and located at posterolateral extremity of PB. Ischial process ( ISP) triangular and broad, located at internal portion of lateral extremities of PB. Lateral prepelvic process ( LPP) situated in lateral extremities of anterior margin of PB; LPP triangular, developed and projected dorsolaterally ( Fig. 17 ).

Color in alcohol. Dorsal disc color beige, brown, gray or dark gray, with large dark spots concentrated between disc margins and central disc area, and also small light spots distributed through entire disc ( Figs. 1A , 2A, C , 3A, C; S 1A, C ). Dark spots dark gray, dark brown or black, and in various shapes such as rounded, oval, polygonal,

vermiculated or even axon shaped. Large dark spots in some specimens possess small beige specks in its central area; when closer to disc margins, these spots become smaller. Large dark spots also occur in head and branchial basket regions. Small light gray or beige spots present polygonal shapes, and their sizes are generally similar to eye diameter but sometimes slightly greater. Dorsal caudal coloration from caudal base to caudal sting tip similar to dorsal disc coloration, with some dark spots on midline, and light spots laterally; post caudal sting region gray to dark gray with beige or light brown specks, but darker closer to tail tip.

Disc ventral coloration with two major patterns: one light, white color, predominant in practically all central disc area and anterior margin, and another darker pattern, gray color, present on lateral and posterior margins of disc ( Figs. 1B , 2B, D , 3B, D; S 1B, D ). Gray pattern in most specimens also possesses small and vermiculate dark gray spots closer to disc margins, with these spots more visible in juvenile specimens. Ventral coloration of pelvic fins also present both patterns present on ventral disc, with light pattern located on anterior margins and central region of pelvic fin, and dark pattern located only at posterior margin. Claspers also with both patterns, with light one at its base, and dark pattern at its medial and terminal regions. Ventral coloration of tail in few specimens with same light pattern of disc occurring from its base to caudal sting tip; however, in most specimens tail region presents a light gray coloration with some darker gray rounded spots. Post-caudal sting region of tail, in all specimens, with dark gray color, progressively darker toward tail tip, and with small dark gray specks thoughout. In live specimens, coloration similar but with dorsal and ventral patterns more clearly demarked.

Geographic distribution. Endemic to the Orinoco basin, specimens of Paratrygon orinocensis analyzed in this study occur in the Apure, Bita and Orinoco rivers ( Fig. 18 ).

Etymology. The epithet orinocensis reflects the endemic distribution of this new species in the main rivers of the Orinoco basin. An toponym.

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 8 | Dermal denticles in anterior margin of the disc of Paratrygon orinocensis, MZUSP 117220 (SEM images). A. dorsal view of four dermal denticles. B. morphology detail of one denticle in dorsal view. C. and D. lateral views of anterior margin dermal denticles. ccp = central coronal plate, 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 18 | Distribution of Paratrygon orinocensis throughout Orinoco basin. This species occurs in the mid and lower portion of Orinoco river, and mid portion of Apure river. See Discussion to a more complete discussion about its distribution. Star = holotype specimen (IAvH-P 11939) locality.