Taxonomic revision of modern Doras Lacepède, 1803 (Siluriformes: Doradidae), with descriptions of three new species



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Suriname (Maroni Dr.): ANSP 187138 (1 alc, 100.5 mm), Litanie River at mouth and confluence with Marowini River, just upstream from settlement of Konya Kondre, 03°17'24”N, 054°04'38”W (SUR 07-05), M.H. Sabaj et al., 21 Apr 2007; ANSP 187139 (5 alc, 77.5–143.2 mm), Lawa River, large cataract complex in side channel west of base camp, ca. 8km SSW Anapaike, 03°19'52”N, 054°04'20”W (SUR 07-06), M.H. Sabaj et al., 21 Apr 2007; ANSP 187399 (1 alc, 147.5 mm; 1 sk 170 mm), same data as neotype; Suriname (Corantijn Dr.): MHNG 2671.071 (2 alc, 143.7–198 mm), Corantijn River, downstream of Wonotobo Falls camp, J.I. Montoya-Burgos et al., 8 Nov 2005; MHNG 2672.075 (3 alc, 173–203 mm) Corantijn River, Wonotobo Falls near camp, J.I. Montoya-Burgos et al., 5 Nov 2005; MHNG 2699.048 (3 alc, 168–237 mm), Sipaliwini River, J. Mol et al., 2007; MZUSP 97654 (1 alc, 178 mm) same data as MHNG 2672.075; USNM 226185, 226187 (2 alc, 109.6–113.6 mm) Matappi Creek 05°01'N, 57°17'30"W, H.M. Madarie, 17 May 1980. Venezuela (Essequibo Dr.): INHS 31676 (1 alc, 194 mm), Río Yuruari (Rio Cuyuni Dr.), near La Pastora, W of Guasipati, Bolivar State (DCT 94-25), D.C. Taphorn et al., 10 Jan 1994; Venezuela (Caroní–Orinoco Dr.), Bolivar State: AMNH 91129 (1 alc, 139.7 mm), Río Lima, trib Río Carapo, south face of Cerro Guaiquinima, 05°30'40"N, 63°30'40''W (CJF-90-02), C.J. Ferraris et al., 16 Feb 1990; AMNH 96798 (1 of 4 alc, 302 mm), Rio Carapo, trib. Rio Paragua, base camp, 05°30'40"N, 063°30'40"W (CJF-90-17), C.J. Ferraris & A. Machado-Allison, 24 Feb 1990; AMNH 91330SD (1 sk, ca. 550 mm), same data as AMNH 96798; ANSP 187157 (1 sk), Rio Carapo, trib. Rio Paragua (Caroní-Orinoco Dr.), below closest set of rapids to mouth, a large caño on left bank (CJF-90-13), C.J. Ferraris & A. Machado-Allison, 24 Feb 1990.
Diagnosis.—Doras carinatus is diagnosed among modern congeners by the following combination of characteristics. Midlateral scutes 33–36; gas bladder with single terminal diverticulum (Figs. 6A–B); teeth present on premaxillae; infraorbital one (lacrimal) with elongate anterior wing extending well beyond mesial concavity for anterior nare (Figs. 4B–C); ventral surface without conspicuous pores or with few small pores restricted to skin around vent; symphyseal limbs of cleithrum with concave lateral and anteriormost margins; distal anterior margin of pectoral spines smooth; postinfranuchal midlateral scutes overlapping and of more or less uniform depth anterior to anal fin; infranuchal scute with medial thorn flanked by subtriangular wings (Figs. 5A–B); postcleithral process deep to shallow (depth 2.28–3.93 times into oblique length) with straight to weakly concave free dorsal margin and dorsal field ornamentation moderately expanded, excluded from or forming less than one-third of posterior (distal) margin of process (Figs. 2B–D); skin covering dorsal-locking spine and base of dorsal spine moderately darkened by weak concentration of melanophores with dorsal spine dusky or becoming gradually lighter distally (Figs. 8, 9); caudal fin uniformly dusky with scattered melanophores (Figs. 8, 9).

Doras carinatus is diagnosed from fossil species †D. dioneae by the following combination of characteristics of the pectoral girdle (see Figs. 2, 3B in Sabaj Pérez et al., 2007). Triangular ventral posterior process of cleithrum well developed with broad base and distal tip extending beyond articulation of anterior process of pectoral spine; thin anterior keel on ventral surface of coracoid strongly oblique, forming about 45° angle with transverse line through body; transition between medial margin of posterior coracoid keel (process) and transverse vertical wall of coracoid gradual and remote (displaced anteriorly and medially) from articulation with anterior process of pectoral spine; trench between anterior and posterior coracoid keels broad, width about equal to that of notch for pectoral-spine insertion.

Comparisons.—Doras phlyzakion and D. zuanoni have 30–32 midlateral scutes, gas bladder with two posterior diverticula (Figs. 6G–H), premaxillae edentate, infraorbital one relatively short, anterior tip extended short distance beyond mesial concavity for anterior nare (Fig. 4A); ventral surface with many small pores in skin particularly on abdomen and near ventral insertion of gill flap (Figs. 3B–C); symphyseal limbs of cleithrum with straight lateral margins and rounded (convex) anteriormost margin; and distal anterior margin of pectoral spines serrated. Doras micropoeus has postinfranuchal midlateral scutes distinctly increasing in separation and decreasing in depth anteriorly from above anal-fin origin; infranuchal scute lacking posteriorly direct wings and with medial thorn absent or rudimentary (Fig. 5C). Doras higuchii has a deep postcleithral process (depth 1.8–2.49 times into oblique length) with free dorsal margin straight to weakly convex, and dorsal field ornamentation broadly expanded, forming one-third to half of posterior margin (Fig. 2E); skin covering dorsal-locking spine and sometimes base of dorsal spine blackened with strong concentration of melanophores with dorsal spine markedly depigmented, pale (Fig. 11); caudal fin with greater concentration of melanophores on lower rays and membranes of upper lobe and upper rays and membranes of lower lobe forming two dusky stripes, particularly in juveniles (Fig. 11A).

The fossil †D. dioneae has triangular ventral posterior process of cleithrum small, tip falling short of articulation of anterior process of pectoral spine; thin anterior keel on ventral surface of coracoid more transversely aligned, forming less than 45° angle with transverse line through body; medial margin of posterior coracoid keel distinctly arched and more proximal to articulation of anterior process of pectoral spine; and trench between anterior and posterior coracoid keels narrow, width less than 3/4 maximum width of notch.



Description.—Morphometrics and meristics summarized in Table 2; aspects of postcleithral process summarized in Table 1. Largest specimen examined ca. 550 mm SL (AMNH 91330SD, sk). Body elongate, slightly compressed, deepest at dorsal-fin origin, gently tapering to short, slender caudal peduncle. Ventral surface flattened from snout to anal-fin origin. Head large, deep, weakly compressed with prominent conical snout; dorsal profile straight to weakly concave from snout tip to between anterior and posterior nares, then curving gently (convex) to interorbital region and finishing straight, weakly oblique to dorsal-fin origin except in the two largest specimens examined (AMNH 91330SD, SL ca. 550 mm and ANSP 187157, SL ca. 500 mm), both as skeletons. In these large specimens the skull begins to rise more steeply at the middle pitline of the supraoccipital, elevating the nuchal region and imparting a shallow concavity to the dorsal profile from the interorbital region to the dorsal-fin origin. Eyes large (22.19–31.06% of head length), covered by thin skin (adipose eyelid not distinct), positioned high on head; dorsal margin of orbit strongly concave; interorbital width relatively narrow (12.46–18.28% of head length).

Mouth small, subterminal; gape with rounded (concave) anterior (premaxillary) margin, straight to weakly concave posterior (dentary) margin. Teeth present on dentaries and usually premaxillae (only one in 19 specimens examined with premaxillae edentate). Each premaxillae with 1–8 strong acicular teeth set close in one or two irregular rows (n = 18, SL 143.2–302 mm). Each dentary with about 10–50 strong acicular teeth a few rows or small patch.

Anterior and posterior nares separate, surrounded by short tubular skin; posterior nare larger than anterior, located more or less at midpoint between anterior nare and anterior margin of eye; anterior nare closer to posterior nare than snout tip. Cephalic shield weakly ornamented, usually with distinct middorsal furrow extending from middle pitline of supraoccipital to about suture between anterior and middle nuchal plates, sometimes extending onto middle nuchal plate. Cranial fontanel with single opening anterior to epiphyseal bar (portion posterior to epiphyseal bar occluded). Fontanel elongate, narrow, widest posteriorly with rounded margin, attenuate anteriorly; enclosed posteriorly and laterally by frontals, anteriorly by mesethmoid. Nuchal foramina absent. Nuchal shield roof-shaped, forming transverse angle. Anterior nuchal plate well-developed, subpentagonal to subhexagonal, wider than long and usually sharing broad lateral suture with epioccipital. Mesethmoid elongate, shaped like a fountain pen nib, attenuate anteriorly with sharply pointed tip. Infraorbital one (lacrimal) elongate with long tapered anterior wing extending well beyond central mesial concavity for anterior nare (Figs. 4B–C). Epioccipital posterior process long, ribbon-like, twisted from horizontal plane (anteriorly) to vertical plane (posteriorly), becoming laterally expanded, often weakly bifid posteriorly (Figs. 5A–B).

Three pairs of barbels: maxillary, inner and outer mental (Fig. 1A). Maxillary barbel long, tip often finishing beyond medialmost point of gill opening; fimbriate with about 15-18 fimbriae along lateral margin; proximal fimbriae rugose with papillae and secondary fimbriae along trailing margin. Mental barbels nearly equal in size, finishing about halfway between anterior margin of lower jaw and medialmost extent of gill opening; bases thick, profusely ornamented with fleshy papillae. Lips fleshy, surfaces with low rounded papillae near insertion of maxillary barbels.

Pectoral girdle in ventral view subtriangular, elongated anteriorly with convergent lateral margins of paired symphyseal (horizontal) limbs of cleithrum long, concave. Anteriormost margin of pectoral girdle truncated with concave margin. Transverse limb of coracoid process with distinct posterior process (keel) relatively short, extending slightly beyond posterior insertion of pectoral fin and falling well short of posterior tip of postcleithral process. Ventral surfaces of pectoral girdle (including posterior processes of coracoid) covered with skin (not exposed).

Postcleithral process variable in shape (Figs. 2B–D), moderately to deeply subrectangular (depth 2.28–3 times into oblique length) in adult specimens from Essequibo, Corantijn and Maroni basins vs. moderately to shallowly subrectangular (depth 2.85–3.93 times into oblique length) in adults from Orinoco and Oyapock basins (Table 1); all margins entire, without conspicuous dentations; free dorsal margin (posterior to supracleithrum) straight (all specimens) to weakly concave (except in Oyapock specimens); ventral margin nearly straight from shoulder to ventral posterior corner of process; posterior margin straight, weakly oblique, tilted anteriorly. Entire postcleithral process laterally compressed, thickness nearly uniform (i.e., blade-like), without distinct longitudinal swelling or thickening along medial face.

Lateral surface of postcleithral process ornamented with low, narrow ridges and shallow grooves; pattern of ornamentation separable into three longitudinal fields (dorsal, middle, and ventral) with the dorsal and middle fields occupying more or less equal areas (Figs. 2B–D). Dorsal field widest anteriorly, tapering posteriorly to dorsal posterior corner, excluded from or forming less than one third of posterior margin of process; surface with network of fine ridges best developed on dorsal anterior portion. Middle field narrowly triangular (expanded posteriorly); surface with elongate longitudinal ridges and grooves, all of which diverge gradually from point posterior to shoulder bulge to posterior margin of process; dorsalmost ridge finishes at or slightly below dorsal posterior corner of process and ventralmost ridge finishes at ventral posterior corner. Ventral field very narrow, tapering posteriorly to ventral posterior corner; surface with network of fine ridges. Dorsal and middle fields planar; ventral field sloping medially.

Skin relatively smooth except for extremely minute punctate tubercles scattered on head, body and fins, particularly on gill covers and dorsal surfaces of head. Elongate slit-like pore in axillary of pectoral fin. Skin beneath entire length of postcleithral process perforated with numerous small round pores imparting sponge-like appearance (Figs. 2B–C). Small pores also present in skin surrounding anteriormost scutes, usually just posterior to medial thorn. Conspicuous pores absent from skin on ventral surfaces or restricted to skin immediately surrounding vent.

Dorsal fin I,6 (n = 27), rarely I,7 (3); pectoral fin modally I,9, range I,8–11 (30); pelvic fin i,6 (30), anal fin modally v,10, range iv–vi,8–11 (30); caudal fin i,7/8,i (30) with dorsal procurrent rays modally 15, range 13–16 (29) and ventral procurrent rays modally 14, range 12–16 (29). Dorsal-fin origin located about one-third SL from snout tip. Dorsal-fin spine long, compressed, gently curved basally, becoming straight distally; ossified tip sharply pointed with soft cartilaginous (break-away) tip when intact. Dorsal spine with distinct antrorse teeth along basal four-fifths of anterior margin, distal fifth smooth; teeth small and crowded basally, becoming slightly larger and more separated towards middle of spine; posterior margin with teeth along distal half nearly to tip, teeth smaller and more separated than those along anterior margin, proximal teeth weakly antrorse, distal teeth straight to weakly retrorse. Adipose-fin tear-drop shaped with distal free margin rounded; base not continued anteriorly as fleshy keel; origin more or less at vertical through anal-fin origin. Pectoral spines strong, dorsoventrally flattened, gently curved and tapering to sharp point with distal cartilaginous tip when intact; length about equal to that of dorsal spine. Anterior margin of pectoral spines with moderate antrorse teeth; teeth small and crowded basally, becoming larger and more separated towards middle, typically absent from distalmost tip; posterior margin with moderate retrorse teeth along entire margin; teeth slightly larger and more separated than those along anterior margin and becoming gradually more separated and larger towards middle. Pelvic fins subtriangular, distal margin weakly rounded and relatively straight when extended; origin near vertical through adpressed tip of pectoral spine and posterior to midpoint of standard length. Anal fin large, triangular with extended distal margin straight to weakly emarginate. Caudal fin distinctly forked with weakly rounded lobes; lower lobe slightly larger and more broadly rounded than upper. Upper and lower procurrent caudal-fin rays like those of caudal fin, not modified into plates.

Lateral line ossified with complete series of 33–36 midlateral scutes ((modally 34; n = 33) per side beginning with infranuchal. Lateral line in tympanal region (anterior to infranuchal scute, between nuchal shield and postcleithral process) without emergent scutes but partially enclosed by three separate canal-like ossifications decreasing in length posteriorly and covered with thin skin. Infranuchal scute contacting posterior nuchal plate dorsally and first complete rib (borne on sixth vertebra) internally; scute tall with ventral anterior expansion strongly contacting internal surface of distal postcleithral process and retrorse medial thorn flanked by subtriangular, posteriorly pointed wings (Figs. 5A–B). Postinfranuchal scutes oblique and weakly overlapping, depth uniform to anal-fin origin; depth of scutes above pelvic-fin origin more or less one-fifth of corresponding body depth. Each postinfranuchal scute with distinct medial thorn, and subtriangular dorsal and ventral wings with posterior margin entire or with a few serrations; dorsal wing slightly smaller and drawn out into anterodorsal and posterior points, ventral wing drawn out into ventral and posterior points. First postinfranuchal midlateral scute with dorsal wing contacting (underlying) that of infranuchal scute.

Gas bladder large, occupying most of dorsal portion of visceral cavity; shape cordiform with paired posterior chambers longer than single anterior chamber; walls smooth except for small (sometimes rudimentary), singular, posterior (terminal) diverticulum. Terminal diverticulum asymmetric, formed by expansion of only one of the two posterior chambers and without internal septa (Figs. 6A–B).

Coloration.—In alcohol and life dorsal and dorsolateral surfaces of head and body uniform gray to tan ground color; sides of body becoming gradually lighter ventrally from midlateral plates; lowermost sides and ventral surfaces pale, white (Figs. 8, 9). Maxillary barbel gray to tan; mental barbels pale, white. Fins without distinct marks. Skin around dorsal locking spine and base of dorsal spine moderately darkened by weak concentration of melanophores; remaining dorsal spine dusky or becoming gradually lighter distally; bases of rays and membranes dusky, becoming gradually clear distally. Paired, anal and caudal fins more or less uniformly dusky with melanophores scattered throughout spines, rays and membranes. Live specimen figured in Le Bail et al. (2000:43).

Distribution and habitat.—Doras carinatus occurs in rivers draining the northern side of Guiana Shield in Brazil (Amapá State), French Guiana, Suriname, Guyana and Venezuela (Fig. 7). From east to west it is known from the Oyapock, Approuague, Sinnamary, Mana, Maroni, Corantijn, Essequibo (including the Cuyuní), and Paragua (Caroní-Orinoco Dr.) basins (includes records reported by Le Bail et al., 2000:43). In the Essequibo basin, Guyana, D. carinatus was collected in the main channel of large rivers over substrates of sand or gravel and often in moderately clear water and swift currents associated with cataracts. Doras carinatus is syntopic with D. micropoeus in the lower Essequibo and upper Maroni basins and likely elsewhere.



Reproduction.—Two females, ANSP 187399 (170 mm) and ANSP 187139 (143.5 mm), swollen with mature eggs were collected in mid-April (highwater season) in the upper Lawa River, a large tributary of Maroni, Suriname. The larger female was collected in a gill net set in the main channel and smaller one was collected closer to shore (depth <1.5 m) at night over sand in moderately swift water below a large cataract. Doras carinatus is likely a non-guarding open substrate spawner in the lithophilous guild of Kryzhanovsky (1949) and Balon (1949).

Etymology.—Species named for spines on midlateral scutes based on Linnaeus’ (1766:504) reference to “Linea lateralis subserrata & carinata spinis, ut in Scombris”. Evidently, the scutes in D. carinatus reminded Linnaeus of the longitudinal keels in “Scombris”, presumably Scomber scombrus Linnaeus 1758, the Atlantic mackerel.

Remarks.—There are no known types for Silurus carinatus. Linnaeus (1766:504, p. 1357 in Gmelin edition) specified its habitat as “Surinami” (Suriname) and his brief description noted “…linea laterali spinosa, cirris 6 pinnatis”, indicating a doradid with fimbriate barbels. Doras carinatus and D. micropoeus are the only fimbriate-barbel doradids known from Suriname where both occur sympatrically in the Corantijn and Maroni basins (Le Bail et al., 2000; pers. obs.). Both species are consistent with Linnaeus’ description of Silurus carinatus. Early references to the Linnaean species, often as “Silure”, “Doras”, or “carené”, by Bonnaterre (1788:153), Bloch and Schneider (1801:108), and Lacepède (1803:117) provide no clues to its identity. Valenciennes’ (in Cuvier and Valenciennes, 1840) redescription and illustration (Plate 442) of D. carinatus somewhat confused the issue as it was based in part on the holotype of Doras oxyrhynchus, a valid species currently placed in Anduzedoras (Sabaj and Ferraris, 2003). Eigenmann (1912) effectively established the identity of the Linnaean species in his “Freshwater fishes of British Guiana…”. He provided an illustration and brief redescription of S. carinatus in the genus Hemidoras, and proposed a new species H. micropoeus distinguished by having midlateral plates “from ventrals forward rudimentary” vs. “nearly equally well-developed along entire length” in H. carinatus. The basis for Eigenmann’s assignment of the Linnaean name S. carinatus is unknown and perhaps nonexistent, but retained here for taxonomic stability. The neotype (ANSP 187114) designated here is consistent with Eigenmann’s redescription and illustration of S. carinatus and was collected syntopically with D. micropoeus in Suriname.
Doras micropoeus (Eigenmann, 1910)

Figs. 1B, 2F, 4D, 5C, 6E–F, 7 & 10; Tables 1 & 3


Hemidoras micropoeus Eigenmann, 1912:195 [type locality: Wismar, British Guiana (= Guyana)].
Holotype.—CM 1636 (365 mm TL, missing, not found at FMNH): Guyana: Demerara River at Wismar, C.H. Eigenmann, et al., Sep 24–29, Oct. 3, 1908.

Paratypes (3).—Guyana: CAS 46959 (1 alc), FMNH 53193 (1 alc, 197 mm) [ex CM 1637, ex IU 12029], Lama Stop-Off; CAS 60712 (1 alc, 217 mm TL), same data as holotype.

Non-type material.—“Guianas”: ANSP 78070 [ex. Hyrtl Coll.] (1 sk, 160 mm), pre-1870. French Guiana: St. Laurent du Maroni (Mana Dr.): MNHN 1998-1691 (1 alc), Mana River, Cayenne Market, P. Planquette, 13 Mar 1983; MNHN 1998-1773 (2 alc), Mana River, P.-Y. Le Bail & P. Keith, 1998; MNHN 1998-1774 (1 alc); (Maroni Dr.): Tampoc River, P.-Y. Le Bail & P. Keith, Nov 1998; MNHN 2000-5863 (1 of 2), Tampoc River, Saut Pièrkuru (station niv1mar4), 02°49’N, 053°32’W, M. Jégu et al., 2000. Guyana (Berbice Dr.): MHNG 2651.065 (1 alc, 140 mm), Berbice River, Dubulay Ranch, Station MCF04-29, J.I. Montoya-Burgos, et al., 5 Nov 2004; Guyana (Demerara Dr.): AMNH 12946 (3 alc, 42.7–149.6 mm) Demerara River, Wismar, A.S. Pinkus, 1934?; AMNH 214844 (9 alc, 37.6–94.4 mm) Demerara River, Malali, A.S. Pinkus 1934; AMNH 214896 (14 alc, 45–86.4 mm), Demerara river, Wismar, A.S. Pinkus, 20 Nov–9 Dec 1934; AMNH 214907 (1 alc, 73.2 mm), Demerara River, Malali, A.S. Pinkus, 26 Nov–1 Dec 1934; AMNH 214957 (3 alc, 43-57.6 mm), Demerara River, Malali, A.S. Pinkus, 1935; AMNH 215083 (1 alc, 64.6 mm), Demerara River, Malali, A.S. Pinkus, Aug 1935; AUM 27983 (11 alc, 27.5–156 mm), Demerara River, north bank near Linden, 06°01’14”N, 058°18’03”W (Guy 98-9), L.M. Page, et al., 18 Oct 1998; INHS 49098 (49 alc), Demerara River, 5.05 mi SSW Linden, bearing 195°, 05°56’00”N, 058°18’22”W (Guy 98-6), L.M. Page et al., 17-18 Oct 1998; INHS 49162 (12 alc), same data as AUM 27983; Guyana (Essequibo Dr.): AMNH 72897 (4 alc, 122.1–170 mm), Mazaruni and Cuyuni Rivers at confluence, about 100 m off Kartabo Point (RES-83-3), R.E. Schmidt & A. Pappantoniou, 10 Aug 1983; ANSP 175867 (1 alc, 175.4 mm), Essequibo River, approx. 3 hours upstream from Kurupukari field station, 04°34’17”N, 058°35’17”W (WGS97-26), W.G. Saul et al., 30 Jan 1997; ANSP 175868 (1 alc, 170 mm), Essequibo River, 180 yd. upstream from Essequibo campsite (Maipuri), 04°45’43”N, 058°45’52”W (WGS97-23), D. Allicock, 27 Jan 1997; ANSP 177426 (1 alc, 302.0 mm), Essequibo River, small blackwater creek opposite Paddle Rock campsite, 04°45’00”N, 058°42’00”W (GGW97-16), C. Watson et al., 23 Nov 1997; ANSP 177880 (4 alc, 181–274 mm), Essequibo River at Essequibo campsite, 04°45’41”N, 058°45’53”W (WGS97-19), D. Torres et al., 26 Jan 1997; ANSP 178703 (1 alc, 222 mm), Essequibo River, extensive sandbar 500 m downstream from Paddle Rock campsite, 04°44’00”N, 058°43’00”W (GGW97-17), C. Watson et al., 23 Nov 1997; INPA _____ (1 alc, 194 mm), same data as ANSP 177880; MZUSP 88606 (1 alc, 164 mm), same data as ANSP 175868. Suriname (Maroni Dr.): Sipalawini: ANSP 187110 (2 alc, 174–225 mm; 2 sk, 205–210 mm), Lawa River, base camp ca. 8 km south-southwest of Anapaike/Kawemhakan (airstrip), 03°19’31”N, 054°03’48”W (SUR 07-01), J.G. Lundberg et al., 18 Apr 2007; Suriname (Corantijn Dr.): Nickerie: USNM 226188 (1 alc, 136.2 mm), Corantijn River, between Baviian Island and Guyana border, 05°31’N, 57°12’W (RPV 80-10), R.P. Vari et al., 6 Sep 1980.
Diagnosis.—Doras micropoeus is diagnosed among modern congeners by two unique characteristics: 1) postinfranuchal midlateral scutes distinctly decreasing in depth anteriorly from above anal-fin origin, becoming either reduced and non-overlapping or lost entirely, and 2) infranuchal scute with medial thorn absent or rudimentary and lacking posteriorly pointed wing-like expansions (Fig. 5C). Doras micropoeus is diagnosed from fossil species †D. dioneae by having a deeper postcleithral process, depth 2.12–2.65 (vs. 2.75) times into oblique length, and by sharing the same combination of characteristics of the pectoral girdle described for D. carinatus (see Diagnosis of D. carinatus).

Comparisons.—Doras micropoeus is further distinguished from D. phlyzakion and D. zuanoni by having a deeper postcleithral process, depth 2.12–2.65 times into oblique length (vs. 3.05–3.84; see Fig. 2); gas bladder with one terminal diverticulum (vs. two posterior diverticula; see Fig. 6); premaxillae with teeth (vs. edentate); infraorbital one elongate, anterior wing well-developed with tip extending well beyond mesial concavity for anterior nare (vs. infraorbital one relatively short, anterior tip extending short distance beyond concavity; see Fig. 4); ventral surface without conspicuous pores or with few small pores restricted to skin surrounding vent (vs. ventral surface with small pores in skin particularly on abdomen and near ventral insertion of gill flap; see Fig. 3); symphyseal limbs of cleithrum with concave lateral and anteriormost margins (vs. straight lateral margins and rounded, convex anteriormost margin); and distal anterior margin of pectoral spines smooth (vs. serrated).

Description.— Morphometrics and meristics summarized in Table 3; aspects of postcleithral process summarized in Table 1. Largest specimen examined 302 mm SL (ANSP 177426), possibly larger holotype (missing), 365 mm TL, reported by Eigenmann (1912). Body elongate, slightly compressed, deepest at dorsal-fin origin, gently tapering to short, slender caudal peduncle. Ventral surface flattened from snout to anal-fin origin. Head large, deep, weakly compressed with elongate, conical snout (particularly in adults); dorsal profile distinctly concave from snout tip to between anterior and posterior nares, then curving gently (convex) to above eye and finishing straight, weakly oblique to dorsal-fin origin. Eyes large (19.81–26.42% head length), covered by thin skin (adipose eyelid not distinct), positioned high on head; dorsal margin of orbit strongly concave; interorbital width relatively narrow (13.73–17.77% head length).

Mouth small, subterminal; gape with rounded (concave) anterior (premaxillary) margin, straight to weakly concave posterior (dentary) margin. Teeth present on dentaries and premaxillae. Each premaxillae with 4–9 strong acicular teeth set close in one or two irregular rows (n = 8, SL 170–274 mm). Each dentary with many (ca. 20–60) strong acicular teeth in a subrectangular patch.

Anterior and posterior nares separate, surrounded by short tubular skin; posterior nare larger than anterior, located more or less at midpoint between anterior nare and anterior margin of eye; anterior nare much closer to posterior nare than snout tip. Cephalic shield weakly ornamented, middorsal furrow lacking or weak, extending from middle pitline of supraoccipital to suture between anterior and middle nuchal plates. Cranial fontanel with single opening anterior to epiphyseal bar (portion posterior to epiphyseal bar occluded). Fontanel elongate, narrow, widest posteriorly with rounded margin, attenuate anteriorly; enclosed posteriorly and laterally by frontals, anteriorly by mesethmoid (Fig. 1B). Nuchal foramina absent. Nuchal shield roof-shaped, forming transverse angle. Anterior nuchal plate well-developed, subpentagonal to subhexagonal, wider than long and usually sharing broad lateral suture with epioccipital (Fig. 1B). Mesethmoid elongate, attenuate anteriorly with sharply pointed tip (Fig. 1B). Infraorbital one (lacrimal) very elongate with long, narrow, tapered anterior wing extending well beyond mesial concavity for anterior nare (Figs. 1B, 4D). Epioccipital posterior process long, ribbon-like, twisted from horizontal plane (anteriorly) to vertical plane (posteriorly), and becoming laterally expanded with irregular dorsal posterior margin (Fig. 5C).

Three pairs of barbels: maxillary, inner and outer mental. Maxillary barbel long, tip more or less reaching medialmost point of gill opening; fimbriate with about 15-18 fimbriae along lateral margin, proximal fimbriae rugose with papillae and secondary fimbriae along trailing margin. Mental barbels nearly equal in size, finishing about halfway between anterior margin of lower jaw and medialmost point of gill opening, bases thick, profusely ornamented with fleshy papillae. Lips fleshy, surfaces with low rounded papillae near insertion of maxillary barbels.

Pectoral girdle in ventral view subtriangular, elongated anteriorly with convergent lateral margins of paired symphyseal (horizontal) limbs of cleithrum long, concave. Anteriormost margin of pectoral girdle truncated with deeply concave margin. Transverse limb of coracoid process with distinct posterior process (keel) relatively short, extending slightly beyond posterior insertion of pectoral fin and falling well short of posterior tip of postcleithral process. Ventral surfaces of pectoral girdle (including posterior processes of coracoid) covered with skin (not exposed).

Postcleithral process blade-like, deeply to moderately subrectangular, depth 2.12–2.65 times into oblique length in adults (n = 11, SL 170–274 mm). Margins entire; free dorsal margin straight to weakly concave; ventral margin straight; posterior margin oblique, tilted anteriorly (Fig. 2F). Surface ornamentation of postcleithral process similar to D. carinatus except divisions between three longitudinal fields often less distinct and dorsal and middle fields more broadly expanded.

Skin relatively smooth except for extremely minute punctate tubercles scattered on head, body and fins, particularly on gill covers and dorsal surfaces of head. Elongate slit-like pore in axillary of pectoral fin. Skin beneath entire length of postcleithral process perforated with numerous small round pores imparting a sponge-like appearance (Fig. 2F). Small pores sometimes evident in skin surrounding anteriormost scutes, usually just posterior to medial thorn. Conspicuous pores absent from skin on ventral surfaces or restricted to skin immediately surrounding vent.

Dorsal fin I,6 (n = 15); pectoral fin modally I,10, range I,9–10 (15); pelvic fin i,6 (15), anal fin modally v,8 in Maroni specimens (4), v,9 in remaining specimens (11), overall range iv–vi,8–10 (15); caudal fin i,7/8,i (15) with dorsal procurrent rays modally 14, range 14–16 (15) and ventral procurrent rays modally 15, range 13–16 (15). Dorsal-fin origin located more or less two-fifths SL from snout tip. Morphology of fins as described for D. carinatus.

Lateral line ossified with a complete or incomplete series of midlateral scutes; total count of scutes and scuteless pores (placeholders) 32–36 per side (modally 34; n = 13). Specimens from Maroni drainage with first 6–10 postinfranuchal scutes lacking; other specimens occasionally with one or two anteriormost postinfranuchal scutes lacking medial thorns or missing entirely. Infranuchal scute tall, narrow with anteroventral expansion strongly contacting internal surface of distal postcleithral process; usually without medial thorn (small emergent thorn or carina sometimes present) and without subtriangular, posteriorly pointed dorsal and ventral expansions (Fig. 5C). Postinfranuchal scutes oblique, shallow and (when present) non-overlapping anterior to vertical between pelvic- and anal-fin origins, becoming deeper and weakly overlapping posteriorly; depth of scute above pelvic-fin origin more or less one-tenth of corresponding body depth. When present, each postinfranuchal scute usually with distinct medial thorn (thorns smallest anteriorly, gradually increasing in size posteriorly to caudal peduncle) and subtriangular dorsal and ventral wings lacking distinct serrations along posterior margin (wings best developed posteriorly); dorsal wing slightly smaller and drawn out into anterodorsal and posterior points, ventral wing drawn out into ventral and posterior points.

Gas bladder large, cordiform with paired posterior chambers longer than single anterior chamber; walls smooth except for single elongate terminal diverticulum (Figs. 6E–F).



Coloration.—Largely as described for D. carinatus except in some specimens of D. micropoeus the melanophores appear more concentrated in the distal portion of dorsal fin, particularly in the membranes (Fig. 10). Live specimen figured in Le Bail et al. (2000:45).

Distribution and habitat.—Doras micropoeus occurs in Atlantic coast rivers draining the northern side of the Guiana Shield in French Guiana, Suriname and Guyana. From east to west it is known from the Mana, Maroni, Corantijn, Berbice, Demerara and Essequibo basins. In the Lawa River, Suriname, adults (ANSP 187110) were collected using gill nets set the main channel below a large cataract. Doras micropoeus is syntopic with D. carinatus in the lower Essequibo and upper Maroni basins and probably elsewhere.

Etymology.—Species name from the Greek words mikros (small) and poieo (to make) in reference to the reduced or “rudimentary” anterior midlateral scutes.
Doras higuchii, new species

Figs. 2E, 3A, 6C–D, 7 & 11; Tables 1 & 4


Holotype.—MZUSP 96333 (alc, 177.7 mm): Brazil: Pará: Altamira Municipality: Rio Curuá, (Iriri-Xingu Dr.), near town of Castelo dos Sonhos, 08°19’07”S, 055°05’23”W (PIPE2007102203), J.L. Birindelli, M.H. Sabaj Pérez, L.M. Sousa, A.N. Ferreira, N.K. Lujan, 23 Oct 2007.

Paratypes.—Brazil (Xingu Dr.):


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