Paracanthopoma alleynei ( Henschel, Bernt, Baskin, Schmidt, Lujan, 2021 ) ( Fig. 8 )

Pinna, Mário de & Dagosta, Fernando Cesar Paiva, 2022, A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus, Papéis Avulsos de Zoologia 62, pp. 1-90 : 16-21

Paracanthopoma alleynei ( Henschel, Bernt, Baskin, Schmidt, Lujan, 2021) ( Fig. 8)

Paracanthopoma sp. 2 – Wosiacki & de Pinna, 2007: 73 [catalog].

Paracanthopoma parva [non Giltay 1935] – Schmidt, 1993 [in part, only specimen AMNH 72898, later designated as holotype of Paravandellia alleynei ; occurrence in Essequibo drainage, Guyana; photograph of live specimen ( Fig. 2 )].

Paravandellia alleynei Henschel, Bernt, Baskin, Schmidt, Lujan, 2021b: 7 , figs.

[holotype: AMNH 72898 , 26.0 mm SL; Guyana: Region 7 (Cuyuni-Mazaruni): Confluence of Mazaruni and Cuyuni rivers at Kartabo Point , Essequibo River basin, 06°22′56″N, 58°41′36″W, col., K. Schmidt, R. Schmidt and A. Pappantoniou, 10 Jul 1983; paratype: AMNH 72899 SW, 1 ex (c&s), 22.0 mm SL; collected with holotype; actually represents Pc.parva ].

Material examined

Type material: AMNH 72898, 1 ex, holotype of Paravandellia alleynei , 26.0 mm SL, Guyana, Region 7 (Cuyuni-Mazaruni), Confluence of Mazaruni and Cuyuni rivers at Kartabo Point, Essequibo River basin (06°22′56″N, 58°41′36″W), col., K. Schmidt, R. Schmidt and A. Pappantoniou, 10 Jul 1983.

Non-type material (all from Brazil): INPA 16555 (mixed with 2 ex of Pc. parva ), 6 ex, 18.9-23.1 mm SL, Brazil, Roraima, Boa Vista, Maracá, rio Branco, col., O. Bitar , May 1988 ; MZUSP 103052 , 5 ex (3 c&s), 18.6-22.6 mm SL, collected with INPA 16555 ; LIRP 7399 , 13 ex, 10.1-17.8 mm SL, Roraima, Boa Vista, rio Uraricoera at Localidade de AlagadiÇo ( rio Branco drainage) (03°22′30″N, 60°35′43″W), col., A. Datovo, 16 Feb 2007 ; LIRP 7412 , 1 ex, 10.1 mm SL, Roraima, Boa Vista, rio Uraricoera at Localidade de AlagadiÇo ( rio Branco drainage) (03°22′30″N, 60°35′43″W), col., M. Carvalho & A. Datovo, 16 Feb 2007 ; LIRP 12697 , 14 ex, 11.4-19.1 mm SL, Roraima, Boa Vista, rio Uraricoera at Localidade de AlagadiÇo (rioBrancodrainage)(03°22′30″N, 60°35′43″W), col., A. Datovo & M. Carvalho 16 Feb 2007 ; LIRP 12698 , 1 ex, 16.7 mm SL, Pará, Jacareacanga, rio Teles Pires [= rio São Manuel] (08°51′28″S, 57°25′10″W), col., M. Carvalho & A. Datovo, 04 Dec 2005 (mixed with 2 ex of Pc. irritans ) ; LIRP 12699 , 1 ex, 17.6 mm SL, Mato Grosso, Apiacás, rio Teles Pires [= rio São Manuel] close to Santa Rosa lodge (08°51′49″S, 57°24′38″W), rio Tapajós drainage, col., M. Carvalho, 03 Dec 2005 (mixed with 2 ex of Pc. irritans ) ; NUP 7525 , 1 ex, 23.6 mm SL, Mato Grosso, Aripuanã, Serra do Expedito,unnamed creek tributary to rio Praia Grande ( rio Madeira basin) (10°02′51″S, 59°23′21″W).

Diagnosis: Distinguished form all congeners except Pc. vampyra by the presence of eleven median premaxillary teeth (vs. either three to nine or 13 and more); by four to six scalpelloid teeth (decreasing in size laterally) stacked in parallel at the distal end of the premaxilla (vs. scalpeloid teeth one or two, equal in size when two); by the presence of one or two conical teeth on the premaxilla (inserted basally relative to distal scalpelloid teeth) (vs. no conical teeth on premaxilla); by the long and ventrally-flat, almost spatulate, snout (vs. snout not pronouncedly spatulate). Distinguished from Pc. vampyra by the bilobed or concave caudal fin (vs. truncate or convex); the fewer procurrent caudal-fin rays (14 to 19 dorsally and ventrally) not forming prominent expansions on caudal peduncle (vs. 22 to 27 dorsal and 21 to 25 ventral, forming large expansions along most of caudal peduncle, which as a consequence is spatulate in shape); the pectoral fin broadly triangular in shape, with rays not markedly differing in length (vs. fin pointedly triangular in specimens 15 mm SL or larger, with rays steeply decreasing in size posteriorly); the presence of scattered dark spots on lateral surface of abdominal wall (vs. absence of dark pigmentation on abdomen); the mostly round mesethmoid cornua (vs. strongly angulate); the long and slender premaxilla (vs. short and thick); the longer snout (39.3-43.1; vs. 35.3-37.6% HL); the short broad parasphenoid, its length less than twice its maximum width (vs. parasphenoid elongate, its length 2.5-3.5 times its maximum width), and the concave anterior margin of the supraoccipital, not extending anteriorly beyond transverse line through articulation with sphenotic (vs. anterior margin of supraoccipital irregularly straight, extending well anteriorly to transverse line through articulation with sphenotic).

Description: Morphometric data for the holotype and paratypes are provided in Table 2 . Body moderately elongate (HL 16.9-18.8% SL). Cross-section of body slightly broader than deep at pectoral-fin insertion and increasingly compressed posterior to that point, tapering to caudal fin. Dorsal profile of body gently convex from head to origin of dorsal fin. ( Fig. 8 ) Dorsal and ventral profiles of caudal peduncle straight and converging towards midline along anterior half and straight or slightly convex and diverging along posterior half, corresponding to area of procurrent caudal-fin rays, with overal effect of gently concave dorsal and ventral margins ( Fig. 8 ). Caudal peduncle narrow, not markedly expanded by procurrent rays. Ventral profile of body straight at pectoral-fin origin and then gently convex until pelvic-fin origin. Myotomes and longitudinal skeletogenous septum clearly visible through thin integument along whole body. Axillary gland small and narrow,elongate in shape, its anterior end adpressed to dorsoposterior margin of muscular pectoral-fin base, extending posteriorly to beyond margin of adpressed pectoral fin (but no specimens with full gland, making its profile difficult to determine precisely). Large, round or oval, axillary-gland pore located approximately at vertical through anterior third of pectoral fin, sometimes immediately posterior to vertical through end of pectoral-fin base.

Dorsal profile of head continuous with that of dorsum ( Fig. 8 ), its origin sometimes indicated by slight constriction of anterior end of epaxial musculature. Head much longer than broad (head width 60.5-63.9% HL), snout broad and very long, parabolic with continuous round anterior margin. Head muscles not entering skull roof. Head strongly depressed ( Figs. 8 , 9 ) (head depth 32.7-35.7% HL) with dorsal profile gently convex, nearly straight, to tip of snout. Ventral profile of head straight, flattened. Eye large (12.4-14.9% HL), without free orbital rim, located dorsolaterally on head and directed dorsolaterally, with pronounced dorsal component ( Fig. 8 ). Integument over eye thin and transparent. Middle of eye almost exactly at middle of HL, interorbital width approximately 75% of longitudinal diameter of eye. Eyelens occupying most of lateral surface of eye and either entirely unconstricted by iris or constricted only marginally, with large round pupil, in specimens examined. Anterior nostril small, surrounded by short tubule of integument produced posteriorly into small pointed process ( Fig. 9 ), with double elastin cores. Anterior internarial width slightly larger than interorbital. Posterior naris slightly larger than anterior one, round or triangular in shape, adjacent ot mesial margin of eye and partly occluded by anterior flap of integument. Posterior naris positioned anteromesially to eye, their middle posterior to transverse line through anterior margin of eyes. Posterior internarial width narrower than interorbital nd approximately equal to diameter of one nostril.

Opercular odontodophore large and elongate, dorsolaterally located on head, on dorsal half of head depth in lateral view,anterodorsally to pectoral-fin base ( Figs.8 , 9 ). Opercular odontodes 12 or 13, arranged in four irregular vertical rows of three or four.Main axis of opercular odontodes oriented horizontally in lateral view, with distal portion of larger ones curved dorsoposteriorly. Few caps of replacement odontodes interspersed with mature ones. Opercular periodontodal fold well-differentiated but small, extending only shortly beyond tips of odontodes. Interopercular odontodophore slightly larger than opercular one, located ventrolaterally on head, immediately ventral to horizontal through origin of pectoral fin, with 12 to 14 odontodes closely positioned in single row or two partly imbricated rows. Interopercular odontodophore approximately equidistant between opercular one and eye. Interopercular periodontodal fold well-differentiated, roundish and extending only shortly beyond tips of odontodes. Epiodontodeal velum thin, covering entire length of odontodes.

Mouth inferior (ventral), strongly flattened ventrally ( Figs. 8 , 9 ). Each premaxilla with 4 to 6 small scalpelloid teethattachedtoitsdistaltipanddisposedinpeculiarparallel and aligned arrangement ( Figs. 4B , 10 ). Scalpelloid teeth progressively larger mesially, deeply hidden in labial tissue and difficult to expose in preserved specimens without damage to soft tissue. Single large conical tooth at anteriormost point of premaxilla ( Figs. 4B , 10 ), corresponding to angle at midlength of bone, its axis mostly straight, directed ventrally, with tip gently curved posteriorly. Upper lip broad, continuous with ventral surface of snout. Median premaxilla large, with 11 teeth disposed in two irregular curved rows ( Figs. 4B , 10 ), anterior one with three teeth on each side (separated by median gap) and posterior one with two teeth on each side and one in middle. All teeth posteriorly oblique to ventral surface of median premaxilla at base and curved further posteriorly at distal pungent portion, those on lateral regions of median premaxilla also with lateral component. All median premaxillary teeth strongly laterally compressed basally. Three to five replacement tooth caps posterodorsally to mature dentition. Median premaxillary velum absent or very reduced. Hypodontal pad of median premaxilla broad, occupying entire upper jaw. Lower jaw narrow, composed mostly of narrow and elongated dentary lobes, anteriorly round and continuous with mental region posteriorly ( Fig. 8 ). Jaw cleft short and strongly directed posteriorly, its lateral portion almost parallel to longitudinal axis. Dentary diastema narrow and well-defined, angulate. Dentary teeth 4, closely packed at mesial end of dentary and disposed as two ventral and two dorsal ones, not exactly aligned ( Figs. 4B , 10 ). Dentary teeth long, their axis anteriorly-directed at base, but strongly curved dorsally at distal third.

Branchiostegal velum forming large, continuous, hyperbolic and posteriorly concave, free fold across whole of mental region ( Figs. 8 , 9 ). Dorsal portion of velum reaching, but not covering, anterior margin of pectoral-fin base. Branchial openings small, spanning approximately area between ventral margin of opercular odontodophore and mid-depth of interopercular oontodophore. Maxillary barbel long and thin, reaching slightly beyond base of anteriormost interopercular odontodes. Posterior point of its base anterior to vertical through anterior margin of eye in lateral view.Mesial (or ventral) part of maxillary-barbel base inserting directly onto corner of mouth without intervening membranous outgrowth. Rictal barbel small but well-differentiated, located mesially to base of maxillary one and approximately onefifth of its length. Nasal barbel vestigially represented by posterior elongated portion of fold around anterior naris described above, with double internal elastin core.

Lateral line short and straight, extending alongside dorsal margin of anterior portion of axillary gland. Terminal lateral-line pore immediately dorsal to axillary gland opening. Very short secondary branch splitting off ventrally from proximal portion of canal, with corresponding pore opening anterior to midlength of main canal. Single long lateral-line tubule, straight in shape, extending for approximately 70% of main canal posterior to bifurcation.

Pectoral fin short (61.4-67.2% HL), triangular in shape and with truncate or gently convex margin, its base on ventral side of body. Pectoral-fin rays i + 5, not differing markedly in length. Pelvic fins small, rectangular with convex margin, closely positioned at base, with i + 4 rays. Pelvic splint present. Origin of pelvics well anterior to vertical through origin of dorsal-fin, entirely covering anus and urogenital openings and ending just short of anal-fin origin. Dorsal fin triangular with round apex,with gently convex or straight distal margin and ii + 7 rays, plus 5 procurrent ones. Anal fin smaller than dorsal one, roughly rectangular in shape, with distal margin gently convex anteriorly and concave posteriorly and ii + 5 fin rays, plus 4 or 5 procurrent ones. Origin of anal fin posterior to vertical through origin of dorsal-fin. Caudal fin bilobed or concave, deeper than maximum depth of caudal peduncle when spread. Principal caudal-fin rays 6 + 7. Procurrent caudal-fin rays 14 to 19 both dorsally and ventrally.

Vertebrae 38 (n = 3) or 39 (n = 8; holotype). First dorsal-fin pterygiophore subsequent to neural spine of vertebra 21 (n = 3). First anal-fin pterygiophore subsequent to haemal spine of vertebra 22 (n = 1) or 23 (n = 2). Dorsalfin pterygiophores 8 (n = 3). Anal-fin pterygiophores 6 (n = 3). Branchiostegal rays 3.

Pigmentation in preservative: Body almost entirely white. Scattered dark spots over lateral surface of abdominal wall, not extending dorsally onto myotomal region. Posterior half of neurocranium with irregular dark brain pigment seen by transparency. Sparse fields of chromatophores between eyes and nostrils, anterolateraly to eyes and dorsal to maxillary barbel base. Isolated spots near base of dorsal fin and on basal portion of caudal fin and hypural plate.

Geographical distribution: Paracanthopoma alleynei has been recorded from uplands in both Brazilian and Guiana shields, in the rio Essequibo, upper rio Branco, rio Teles Pires and rio Aripuanã basins ( Fig. 20 ).

Remarks: The paratype of Pc. alleynei (AMNH 72899SW) belongs to a species different from the holotype. Examination of that specimen reveals that it has an epiphyseal comissure of the latero-sensory canal opening as a single median s6 pore; an anteriorly-produced supraoccipital extending approximately to the epiphyseal comissure; nine median premaxillary teeth (three of which currently fallen off but indicated by sockets); one or two scalpelloid teeth on the premaxilla (inferred by sockets), no conical premaxillary teeth; the interopercle closer to the opercle than to the lower jaw articulation; a very small ascending process of the opercle; a thickwalled palatine, with a relatively narrow central fenestra; the palatine cartilage for the articulation of the maxilla at the midlength of the lateral margin of the bone; and the mesial margin of the palatine produced mesially at its midlength. All those characteristics contrast with conditions in the holotype and remaining specimens of Pc. alleynei (no epiphyseal commissure and double s6 pores; anteriorly concave supraoccipital; 11 median premaxillary teeth; four to six scalpelloid teeth; one or two conical premaxillary teeth; interopercle closer to lower-jaw articulation than to opercle; large ascending process of the opercle; thin-walled palatine with a central fenestra occupying nearly the entire area of the bone; the palatine cartilage for the articulation of the maxilla at the anterior half of the lateral margin of the bone; and the mesial margin of the palatine continuous, not produced mesially). Those characters show that the paratype is a very different species from the holotype, and also that it belongs to a disjunct subgroup of the genus, the parva -clade (see Discussion below). The paratype specimen was first reported in Schmidt (1993, then bearing the number AMNH 72898SW) and was cleared and stained on the occasion of that publication. As then, the specimen is today well-stained for cartilage but not for bone. It has lost the external portions of all fins, caudal- and pelvic-fin supports,part of the mesethmoid cornua,most odontodes, all scalpelloid teeth and some median premaxillary teeth. Nonetheless, the skeletal features mentioned above can still be clearly confirmed. Although the condition of the specimen does not allow examination of all relevant details, it most likely belongs to Pc. parva , or a very similar form. Illustrations of the specimen and accompanying text in Schmidt (1993, figs. 1, 2) are sufficient to show that it is a taxon different from the holotype, such as the epiphyseal comissure opening as a single median pore.The description of Pc.alleynei (Henschel et al., 2021: 10) mentions the latter condition as typical for the species, an observation presumably based on the paratype only because it does not correspond to the holotype (with double pores). Both the holotype and paratype of Pc. alleynei have been collected in the same locality and date, but from different hosts (the former from Brachyplatystoma vaillantii and the latter probably from Doras micropoeus ). Co-occurrence of Pc. alleynei and Pc. parva is previously recorded in at least one other sample (INPA 16555, from the rio Branco).

Figures

Figure 2. Map of South America showing geographical distribution of Paracanthopoma.

Figure 4. Comparative chart of jaws and anterior portion of head of Paracanthopoma species, cleared and stained specimens, ventral views: (A) Pc. ahriman FMNH 105525;(B)Pc.alleynei MZUSP 103052;(C) Pc.cangussu MZUSP 86250;(D)Pc.capeta MZUSP 29154;(E) Pc.daemon MZUSP 95597;(F)Pc.irritans INPA 20529; (G) Pc.malevola MCP 36217;(H) Pc.parva MZUSP 30400;(I) Pc.saci MZUSP 125626; (J) Pc.satanica MZUSP 100149;(K) Pc.truculenta MZUSP 30404;(L) Pc.vampyra MZUSP 100138. Scale bars = 500 μm. Pc.carrapata not shown.

Figure 8. Paracanthopoma alleynei, MZUSP 103052,21.6 mm SL,Brazil,Roraima,Boa Vista, Maracá,Rio Branco.(A) Lateral view of body; (B) Dorsal view of head; (C) ventral view of head.

Figure 9. Paracanthopomaalleynei, INPA 16555,SEM images of head.(A) Dorsal;(B)Ventral.Scale bar = 500 μm.

Figure 10. Paracanthopoma alleynei, MZUSP 103052,CT scan images of head skeleton,(A) Lateral;(B) Dorsal;(C)Ventral.

Figure 20. Map of northern South America showing geographical distribution of Paracanthopoma ahriman, (losenge); Pc. alleynei (pentagon), Pc. cangussu (cross), Pc. capeta (6-tip star); Pc. carrapata (inverted triangle), Pc. daemon (square). Open symbols represent type localities. Some symbols may represent more than a single locality or lot of specimens.