Paracanthopoma irritans, Pinna & Dagosta, 2022

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 : 37-42

Paracanthopoma irritans , new species ( Fig. 21 )

Paracanthopoma sp. 4 – Wosiacki & de Pinna, 2007: 73 [catalog].

Holotype: MZUSP 126815 (split from MZUSP 100136 ) 16.5 mm SL, Brazil, Pará, rio Trombetas , approx. 70 km upstream from Oriximiná (approx. 01°32′S, 56°14′W), col A.C. Lima 21 Jan 2001.

Paratypes: BRAZIL: INPA 12430 , 2 ex, 10.4 mm SL (smaller specimen; larger one damaged), Brazil, Amazonas, rio Capucapu (trib. to rio Jatapu , rio Uatumã drainage), col., J. Porto, 27 Nov 1988 ; INPA 20529 , 23 ex (2 c&s), 15.4-20.1 mm SL, Amapá,rio Amapá Grande at Cachoeira Grande, col., M. Jégu, 25 Aug 1992 ; LIRP 12689 , 21 ex, 12.5-18.6 mm SL, Pará, Jacareacanga, rio Cururu ( rio Teles-Pires drainage), (08°49′36″S, 57°14′03″W), col., M. Carvalho & A. Datovo, 06 Dec 2005 ; LIRP 12690 , 21 ex, 11.8-16.8 mm SL, Pará, Jacareacanga, rio Teles-Pires , (08°53′04″S, 57°23′02″W), col., M. Carvalho & A. Datovo, 05 Dec 2005 ; LIRP 12691 , 6 ex, 12.7-17.3 mm SL, Pará, Jacareacanga, sand bank on right margin of rio Cururu ( rio Teles-Pires drainage) (08°53′42″S, 57°14′27″W), col., M. Carvalho & A. Datovo, 06 Dec 2005 ; LIRP 12692 , 2 ex, 15.8-16.2 mm SL, Pará, Jacareacanga, rio Cururu ( rio Teles-Pires drainage), (08°52′27″S, 57°15′09″W), col., M. Carvalho & A. Datovo, 06 Dec 2005 ; LIRP 12695 , 11 ex, 9.3-15.5 mm SL, Mato Grosso, Apiacás, rio Tapajós drainage (08°50′52.72″S, 57°25′14.21″W), col., M. Carvalho, 02 Dec 2005 ; LIRP 12698 , 2 ex, 11.6-13.8 mm SL, Pará, Jacareacanga, rio Teles Pires (08°51′28″S, 57°25′10″W), col., M.Carvalho & A.Datovo, 04 Dec2005 (mixed with 1ex of Pc. alleynei ) ; LIRP 12699 , 2 ex, 11.9-12.6 mm SL, Mato Grosso, Apiacás, rio Tapajós drainage (08°51′58.89″S, 57°24′41.85″W),col., M.Carvalho, 03Dec2005 (mixed with 1 ex of Pc. alleynei ) ; MZUSP 87049 , 4 ex, 8.4-11.8 mm SL, Mato Grosso, Gaúcha do Norte, rio Curisevo (trib. to rio Xingu ), Porto do Vitório , near Ribeirão Kevuaieli (13°02′05″S, 53°25′19″W), col., C. Moreira, I. Landim & A. Datovo, 19 Oct 2004 (collected together with Pc. parva MZUSP 87048) ; MZUSP 87099 , 1 ex, 15.3 mm SL, Mato Grosso, Paranatinga, rio Jatobá (trib. to rio Ronuro , rio Xingu drainage), at bridge on road from Salto da Alegria to Nova Ubiratã (12°49′19″S, 54°09′24″W), col., J.L. Birindelli et al. team, 22 Oct 2004 ; MZUSP 94977 , 2 ex, 9.8 and 14.3 mm SL, Brazil, Amazonas, rio Jaú , Lago do Miratucu ( rio Negro drainage), col., A.L. Kirovsky, 10 Jun 1996 ; MZUSP 94981 , 4 ex, 10.7-14.8 mm SL, Brazil , rio Xingu,col.,unknown, 17 Sep 2001 ; MZUSP95675 , 1 ex, 13.4 mm SL, Mato Grosso, Gaúcha do Norte, Ribeirão da Anta and flood lake, at mouth on rio Culuene ( rio Xingu drainage) (13°30′53″S, 53°05′34″W), col., F.C. T. Lima et al., 12 Oct2007 ; MZUSP96052 , 27 ex(3 c&s), 10.2-16.3mm SL, Pará, Jacareacanga, rio Teles Pires immediately below Sete Quedas rapids, rio Tapajós drainage (09°19′01″S, 56°46′47″W), col., L.M. Sousa & A.L. Netto-Ferreira, 26 Sep 2007 ; MZUSP 99803 , 5 ex, 15.0- 17.6 mm SL, Pará, Jacareacanga, rio Teles Pires ( rio Tapajós drainage), downstream from Sete Quedas (09°19′56″S, 56°46′33″W), col., L.M. Sousa & A.L. Netto-Ferreira, 09 Jun 2008 ; MZUSP 99942 , 1 ex, 13.6 mm SL, Pará, Jacareacanga, rio Teles Pires ( rio Tapajós drainage), downstream from Sete Quedas (09°20′38″S, 56°46′42″W), col., L.M. Sousa & A.L. Netto-Ferreira, 10 Jun 2008 ; MZUSP 100136 , 16 ex (3 c&s), 12.5-17.0 mm SL, collected with holotype ; MZUSP 100233 , 10 ex (2 c&s), 12.8-16.8 mm SL, Amapá /Pará, rio Jari, above Cachoeira de Santo Antônio, between Porto Sabão and 5 km above mouth of rio Uiratapuru (00°37′02″S, 52°31′35″W), col., C. R. Moreira and F.A. Bockmann, 20-24 Feb 2008 ; MZUSP 100235 , 201 ex (15 c&s), 10.6-15.5 mm SL, Amapá, rio Jari , near left margin, downstream from Laranjal do Jari, col., C. R. Moreira & F.A. Bockmann, 08 Oct 2007 ; MZUSP 103511 , 14 ex, 9.1-13.4 mm SL, Amapá, Laranjal do Jari, Igapó on left margin of rio Jari , upstream from Iratapuru , upstream from Cachoeira de Santo Antônio (00°35′05″S, 52°36′59″W), col., J. Birindelli et al., 22 Feb 2009 (collected with Pc. parva, MZUSP 126876) ; MZUSP 111690 , 1 ex, 14.4 mm SL, Pará, Altamira, rio Xingu at Praia do Pajé , at mouth of Igarapé Panela (03°14′12″S, 52°13′21″W), col., O. Oyakawa et al., 08 Nov 2011 ; MZUSP 118136 , 1 ex, 15.4 mm SL, Mato Grosso, Apiacás, rio Teles Pires ( rio Tapajós drainage) (07°53′55.86″S, 57°50′36.32″W), col., W. Ohara, 31 Aug 2015 ; MZUSP 119685 , 2 ex [mixed with 6 ex of Pv. oxyptera ], 15.4-17.2 mm SL, Pará, Altamira, rio Curuá, at Curuá Beach t Castelo dos Sonhos district (08°20′53.94″S, 55°04′58.55″W), col., O. Oyakawa et al., 07 Aug 2015 ; MZUSP 120574 , 6 ex, 11.8-13.7 mm SL, Pará, Tracuateua, Igarapé AÇaiteua ( rio Quatipuru drainage) (01°08′39.09″S, 46°59′14.56″W), col., R. Reis et al., 21 Aug 2014 ; MZUSP 120575 , 6 ex, 10.9-13.6 mm SL, Pará, Tracuateua, Igarapé AÇaiteua ( rio Quatipuru drainage), col., R. Reis et al., 05 Jun 2015 ; MZUSP 120576 , 1 ex, 12.2 mm SL, Pará, Tailândia, Agropalma, rio Acará drainage (02°30′10.8″S, 48°53.0′W), col., Renan Reis, 2016 . PERU: INHS 42756 , 3 ex, 13.6-15.5 mm SL, Loreto, río Nanay (río Amazonas drainage) at Pampa Chica , N edge of Iquitos, col., M.H. Sabaj et al., 27 Jul 1997 . VENEZUELA: MBUCV-V 14057 , 1 ex, 18.1 mm SL, Cataniapo, Las Pavas, Caño Las Pavas , tributary of río Cataniapo ( río Orinoco drainage) (05°34′00″N, 67°30′36″W), col., R. Royero, 25 Jul 1982 ; MBUCV-V 17853 , 11 ex, 13.2-14.8 mm SL (mixed with additional specimens of Paravandellia sp. ), Amazonas, Mavaca, río Mavaca ( río Orinoco drainage), beaches upstream from Campamento Base , Expedición Tapirapecó, col., R. Royero et al., 22 Mar 1988 ; MBUCV-V 19816 , 20 ex, 12.2-14.9 mm SL, Apure, Capanaparo, La Pica , Caño La Pica , tributary of río Capanaparo ( río Orinoco drainage) at road San Fernando de Apure-Puerto Páez, col., O. Castillo, 20 May 1989 ; MBUCV-V 29078 , 1 ex, 17.7 mm SL, Amazonas, Cataniapo, Las Pavas, río Cataniapo ( río Orinoco drainage), port at Comunidad Las Pavas (05°36′00″N, 67°30′37″W), col., R. Royero, 16 Aug 1984 ; MZUSP 87065 , 1 ex, 17.3 mm SL, Bolívar, río Aro (río Orinoco drainage), Hato Las Mayitas , south of Moitaco (07°58′25″N, 64°11′17″W), col., F. Provenzano & A. Rojas, 16 Apr 2004 ; MZUSP 106060 , 2 ex, 15.9-16.5 mm SL, Amazonas, río Mavaca ,beach upstream from base-camp of Tapirapecó Expedition, col., R. Royero et al., 22 Mar 1988 ; USNM 272286 , 1 ex, 14.7 mm SL, Amazonas, Ature, río Orinoco, raudales de Ature , eastern shore, (approx. 05°36′N, 67°37′W), col., R. P. Vari et al., 02 Dec 1984 .

Diagnosis: Distinguished form all congeners except Pc. ahriman , Pc.cangussu , and Pc.capeta , by the presence of five median premaxillary teeth (two or three often in replacement) (vs. either three or 9 to19 in total).The species is further distinguished from all congeners, except Pc. ahriman and Pc.cangussu , by the broad and long ventral portion of the opercular periodontodal fold, forming a lateral ridge of integument extending anteriorly to the dorsal margin of the interopercular odontodophore (vs. ventral part of fold not anteriorly extended,independent from interopercular odontodophore). Distinguished from Pc. ahriman by the sparse dark pigmentation on the head (vs. heavy dark pigmentation on head, faded in long-preserved specimens); by the narrower head (head width 73.3-76.9% HL; vs. 80.7-87.6); by the narrower interorbital (11.0-12.8% HL; vs. 14.8-17.9); by the narrower anterior internarial width (13.4-16.5% HL; vs. 17.6-20.2); by the narrower posterior internarial width (3.3-5.5% HL; vs. 10.1-11.4). Distinguished from Pc. cangussu by having 6 + 6 principal caudal-fin rays (vs. 5 + 5); by the less deep caudal peduncle (8.3-10.6% SL; vs. 10.8-13.0); by the narrower posterior internarial width (3.3-5.5% HL; vs. 8.1-10.0); by the fewer procurrent caudal-fin rays (19-25 dorsally and 21-25 ventrally, vs. 28-30 dorsally and 27-29 ventrally); by the caudal peduncle progressively deeper to base of caudal fin (vs. deepest portion of caudal peduncle approximately at its half-length); by the dorsal and ventral profiles of caudal peduncle gently continuous with caudal fin, with only slight depression in some specimens (vs. profiles of caudal peduncle posteriorly strongly converging towards base of caudal fin, forming pronounced concave regions clearly delimiting beginning of caudal fin); by the interorbital smaller than eye diameter (vs. larger). Further distinguished from Pc. capeta by the broader head (73.3-76.9% HL; vs. 68.0-72.0); by the mouth cleft directed more strongly posteriorly than laterally (vs. opposite); and by the roundish median premaxilla (vs. trapezoidal with nearly straight anterior margin).

Description: Morphometric data for the holotype and paratypes are provided in Table 7 . Body moderately elongate (HL 16.7-18.6% 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, nearly straight, from head to origin of dorsal fin ( Fig. 21 ). Dorsal and ventral profiles of caudal peduncle strongly convex posterior to ends of dorsal and anal fins, spatulate, expanded by procurrent caudal-fin rays. Dorsal and ventral profiles of caudal peduncle gently continuous with caudal fin, with only slight depression in some specimens.Ventral profile of body straight to pectoral-fin base and then gently convex until pelvic-fin origin, with some specimens with distented abdomen due to gut content. Myotomes and longitudinal skeletogenous septum clearly visible through thin integument along whole body. In few specimens, axillary gland full with secretion, very large and protruding markedly on surface of body. In majority of specimens,gland empty, much smaller and less conspicuous. When full, anterior end of gland surrounding dorsoposterior, ventral and posterior margins of muscular pectoral-fin base, as thick corselet, extending posteriorly beyond margin of adpressed pectoral fin for distance equivalent to fin length. Gland narrowing to blunt posterior end, extending along limit between hypaxial musculature and abdominal cavity, its large round or oval pore located slightly posterior to middle of pectoral-fin length, in dorsal view. Condition of gland posterior to pore evidently related to amount of secretion stored at time of preservation.

Dorsal profile of head continuous with that of dorsum, its origin indicated by slight constriction of anterior end of epaxial musculature. Head longer than broad (head width 73.3-76.9% HL), snout broad, parabolic with a continuous round anterior margin ( Fig. 21 ). Head muscles not entering skull roof. Head moderately depressed (head depth 34.9-45.1% HL) with dorsal profile gently convex, nearly straight, with curvature accentuated close to tip of snout. Ventral profile of head straight, flat. Eye large (14.0-18.7% HL), without free orbital rim, located dorsolaterally on head and directed dorsolaterally, with pronounced lateral component. Integument over eye thin and transparent. Middle of eye slightly anterior to middle of HL, interorbital smaller than eye diameter. Eyelens large and unconstricted by iris in specimens examined. Anterior nostril small, surrounded by short tubule of integument only slightly produced posteriorly into very small nasal barbel ( Fig. 22 ). Anterior internarial width approximately equal to interorbital. Posterior naris large and widely open twice as large as anterior ones, adjacent to anteromesial margin of eye and partly occluded by anterior flap of integument ( Fig. 22 ). Anterior margins of posterior nares leveled or slightly anterior to transverse line through anterior margins of eyes. Posterior internarial width narrower than interorbital and narrower than diameter of one nostril.

Opercular odontodophore medium-sized and nearly round, dorsolaterally located on head, on dorsal half of head depth in lateral view, anterodorsally to pectoral-fin base. Opercular odontodes 6 to 9, closely positioned in more or less irregular roundish disposition, with two largest ones posteriorly. Main axis of opercular odontodes oriented horizontally in lateral view, with distal portions of larger posterior ones curved dorsoposteriorly. Opercular periodontodal fold well-differentiated but short, extending shortly beyond tips of odontodes, its ventral side extending anteriorly as broad straight or slightly convex edge to dorsal margin of interopercular periodontodal fold. Interopercular odontodophore slightly larger than opercular one, located ventrolaterally on head,immediately ventral to horizontal through origin of pectoral fin, with 8 or 9 odontodes closely positioned in two irregular, partly imbricating, rows. Interopercular odontodes larger posteriorly, dorsal ones curved dorsomedioposteriorly and ventral ones curved ventroposteriorly. Interopercular odontodophore slightly closer to opercular one than to eye. Interopercular periodontodal fold of integument well-developed, roundish, extending well beyond tips of odontodes. Epiodontodal velum thin and transparent, covering most of odontodes.

Mouth inferior (ventral). Each premaxilla with 1 or 2 scalpelloid teeth attached (in parallel when 2) to its distal tip. Two tooth sockets always present, but one of them usually in process of replacement. Scalpelloid teeth deeply hidden in labial tissue and impossible to expose in preserved specimens without damaging soft tissue. No conical teeth on premaxilla ( Figs. 4F , 23 ). Upper lip very broad, with ventral surface of snout. Median premaxilla small, restricted to middle of upper jaw, with 5 teeth disposed in single row, with one central largest tooth and two smaller ones on each side. In most specimens, one or two teeth in process of replacement, but total count of five obvious by tooth sockets and relative position of attached teeth. Tooth bases disposed at approximately same transverse line, with central one slightly anterior to others ( Figs. 4F , 23 ). 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. Basal portion of all median premaxillary teeth strongly compressed laterally. Median premaxillary velum well-defined, semicircular, covering whole dentition when intact. Hypodontal pad of median premaxilla small, forming round mound following tooth distribution. Lower jaw narrow, composed mostly of short pointed dentary lobes, mostly confluent at midline, continuous with mental region posteriorly. Jaw cleft short, oblique relative to longitudinal axis. Dentary diastema small and angulate. Dentary teeth 4 (when 3, replacement one in formation), closely packed at mesial end of dentary and disposed as two ventral and two dorsal ones, not exactly aligned ( Figs. 4F , 23 ). Dentary teeth long and strongly curved, with ventral ones longer and with curvature positioned distally and dorsal ones shorter and with curvature approximately at midlength. All dentary teeth with their axis anteromesially-directed at base, but strongly curved dorsally at distally.

Branchiostegal velum forming large free fold, in continuous posteriorly concave arc across whole of mental region ( Fig. 22 ). Dorsal portion of fold reaching, but not covering, anterior margin of pectoral-fin base. Branchial openings small, spanning part of area between ventral margin of opercular odontodophore and mid-depth of interopercular odontodophore, anteroventrally to pectoral-fin base. Maxillary barbel very thin, especially distally, in most populations not reaching, or barely reaching, interopercular odontodophore ( Fig. 22 ; but some with longer berbels reaching to middle of interopercuar odontodophore, e.g., MZUSP 120575). Posterior point of maxillary barbel base at, or slightly 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 to vestigial, attached mesially to base of maxillary barbel. Nasal barbel very small, represented by posterior elongated portion of integument fold around anterior naris, with double internal elastin core visible in cleared and stained specimens.

Lateral line very short, slightly curved dorsally distally, extending alongside dorsal margin of anterior portion of axillary gland. Terminal lateral-line pore dorsal to axillary gland opening. Very short secondary branch splitting off ventrally from proximal portion of main canal, with corresponding pore opening at approximately basal third of main canal.Single lateral-line tubule very poorly calcified, extending for most of main canal posterior to bifurcation.

Pectoral fin short (60.4-68.6% HL), with convex-truncate margin, its base on ventral side of body. Pectoral-fin rays i + 5 (i + 6 on one side of one specimen). Pelvic fin very small, close to each other at base, modally with i + 4 rays, (a few specimens with i + 3 or i + 5), with variable branching pattern ranging from all rays unbranched to maximum of four branched. Pelvic splint usually present, absent in few specimens. Origin of pelvics close to origin of anal fin, slightly anterior to vertical through origin of dorsal-fin, entirely covering anus and urogenital papilla and extending posteriorly to origin of anal fin. Posterior margin of pelvic fin round. Dorsal fin small, roughly rectangular-roundish, with gently convex distal margin. Dorsal-fin rays i + 6 or ii + 6, a single specimen with ii + 5, plus 4-6 procurrent ones. Anal fin small, similar in size and shape to dorsal fin but more roundish, modally with ii + 5 rays (one specimen i + 5), plus 4-6 procurrent ones. Origin of anal fin at vertical through origin of dorsal fin. Caudal fin truncate with round corners, less deep than maximum depth of caudal peduncle. Principal caudal-fin rays 6 + 6 (n = 16) with an anomalous specimen in MZUSP 100136 with 5 + 5. Procurrent caudal-fin rays 19 (n = 4), 20 (n = 1), 21 (n = 3), 22 (n = 2), 23 (n = 4), 24 (n = 2) or 25 (n = 1) dorsally and 21 (n = 1), 22 (n = 1), 23 (n = 4), 24 (n = 6) or 25 (n = 5) ventrally.

Vertebrae 39 (n = 3), 41 (n = 4), 42 (n = 4), 43 (n = 5) or 44 (n = 1). First dorsal-fin pterygiophore subsequent to neural spine of vertebra 21 (n = 6), 22 (n = 9), 23 (n = 2). First anal-fin pterygiophore subsequent to haemal spine of vertebra 20 (n = 1), 21 (n = 3), 22 (n = 8), 23 (n = 4) or 24 (n = 1). Dorsal-fin pterygiophores 6 (n = 17). Anal-fin pterygiophores 6 (n = 17). Branchiostegal rays 3.

Pigmentation in preservative: Body almost entirely white. Dorsum lacking dark pigment. Posterior part of caudal peduncle with irregular longitudinal stripe formed by internal chromatophores along vertebral column, with some dark spots also over hypural plate in some specimens. Dorsal half of abdomen with few sparse dark chromatophores. Posterior half of neurocranium with irregular dark brain pigment seen by transparency, forming irregular bilateral patterns, often delimiting dark protrusion at midline. Brain pigment faintly extending anteriorly along edges of neurocranium. Some specimens with dark fields over epirostralis muscle, anterolaterally to eyes, and a spot on opercular odontodophore.

Etymology: From the Latin irritans , irritating, taken from the name of the human flea, Pulex irritans .

Geographical distribution: Paracanthopoma irritans has a widespread but patchy distribution in the tributaries of the Amazon basin in Brazil and Peru, and río Orinoco in Venezuela ( Fig. 27 ). Except for a record in the río Nanay (rio Amazonas drainage in Peru), all other lots are from Amazonian tributaries east of the mouth of the rio Negro. It is absent in the Araguaia system, where it is apparently replaced by Pc. cangussu . It has not yet been recorded in the southwestern Amazon. This is the only species of Paracanthopoma that occurs in any of the isolated drainages north of the mouth of the Amazon (rio Amapá Grande).

Biology: An 8.4 mm SL specimen of Pc. irritans in MZUSP 87049 is the smallest vandelliine yet found with evidence of ingested blood. The species also seems to mature at relatively small sizes.The lot MZUSP 96052 includes six female specimens with large mature eggs visible externally, the smallest of which is 13.0 mm SL and the largest 15.0 mm SL.

Remarks: This species is one of the most variable in Paracanthopoma , with much geographically-correlated morphological variation. A few of those variations stand out as possibly relevant taxonomicaly. Specimens in MZUSP 100235 (rio Jari) differ from usual Pc. irritans in having a visually much narrower caudal peduncle, which results in a distinct body shape.Since this difference is not reflected in additional characters, it is here considered as a populational variant. Specimens in MZUSP 94981 (rio Xingu) differ from the type series in a number of details. Their head is proportionally shorter and narrower, their caudal peduncle is more strongly spatulate, and their anterior nostril is more anteriorly located (in lateral aspect approximately at middistance between posterior nostrils and tip of snout rather than closer to former). They possibly represent a distinct species, though certainly close to Pc. irritans and Pc. cangussu . Given the few specimens available and the relatively imprecise locality information, their description at this time seems unwarranted. Finally, specimens in MZUSP 120575 are different from a majority of other samples of Pc. irritans in having obviously longer maxillary and rictal barbels. In view of the wide geographical distribution and phenotypic variation, it is possible that Pc. irritans actually comprises additional species not yet recognized.

Figures

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 21. Paracanthopomairritans,holotype,MZUSP 126815,16.5 mm SL,Brazil,Pará,RioTrombetas,(A) Lateral viewof body;(B)Dorsal viewof head;(C) ventral view of head.

Figure 22. Paracanthopoma irritans, paratype,MZUSP 96052,SEM images of head.(A) Dorsal;(B)Ventral.Scale bar = 500 μm.

Figure 23. Paracanthopoma irritans, holotype,MZUSP 126815,CT scan images of head skeleton,(A) Lateral;(B) Dorsal;(C) Ventral.Specimen poorly calcified,some structures not properly shown.

Figure 27. Map of northern South America showing geographical distribution of Paracanthopoma irritans (dot) and Pc. malevola (triangle). Open symbols represent type localities. Some symbols may represent more than a single locality or lot of specimens.