Pimelodus halisodous, Ribeiro & Lucena & Lucinda, 2008

Ribeiro, Frank R. V., Lucena, Carlos A. S. & Lucinda, Paulo H. F., 2008, Three new Pimelodus species (Siluriformes: Pimelodidae) from the rio Tocantins drainage, Brazil, Neotropical Ichthyology 6 (3), pp. 455-464 : 458-460

Pimelodus halisodous , new species

Fig. 3

Pimelodus sp. D - Lucinda et al., 2007: 79

Holotype. MCP 41738, 108.8 mm SL, rio Paranã, 12º30’S 48º12’W, fazenda Traçadal , Paranã, Tocantins, Brazil, 9 May 2000, Neamb- UFT.

Paratypes. Brazil. Tocantins State. All collected by Neamb-UFT staff. MCP 41921, 2 , 99.5-101.2 mm SL, UNT 3438 , 2 (1 c&s), 98.9-103.9 mm SL, Porto Nacional, rio Tocantins, 10º43’15"S 48º25’14"W, 14 Jan 1997 . UNT 3443 , 1 , 107.0 mm SL , Paranã, fazenda Traçadal, rio Paranã, 12º30’S 48º12’W, 25 Mar 1998 . UNT 3449 , 1 , 98.7 mm SL, Brejinho de Nazaré , rio Tocantins, 10º59’46"S 48º32’06"W, 4 Nov 2002 . UNT 3450 , 1, 110.7 mm SL, collected with the holotype. UNT 3452 , 1 , 96.5 mm SL, Porto Nacional, rio Tocantins, 10º43’15"S 48º25’14"W, 10 Jun 2002 . UNT 3455 , 1 , 99.2 mm SL, Porto Nacional, rio Tocantins, 10º43’15"S 48º25’14"W, 18 Dec 1997 . UNT 3899 , 1, 106.2 mm SL, Pedro Afonso, rio Sono , approximately 8º59’S 48º10’W, 20 Feb 2001 . UNT 3900 , 2 , 88.6 and 84.8 mm SL, Porto Nacional, rio Tocantins, 10º43’15"S 48º25’14"W, 4 Dec 2002 . UNT 5837 , 1 , 103.0 mm SL , Paranã, fazenda Traçadal, rio Tocantins, approximately 12º29’S 48º12’W, 29 Sep 1999 .

Diagnosis. Pimelodus halisodous is distinguished from its congeners, except P. jivaro , P. joannis , P. ornatus , P. pictus , and P. stewarti , by the presence of a dorsal median crest along supraoccipital process (vs. crest absent); and shorter distance between the posterior nostril and the anterior orbital border (posterior nostril closer to anterior orbital border vs. posterior nostril closer to anterior nostril than to anterior orbital border). Pimelodus halisodous differs from P. jivaro by the shorter maxillary barbel, extending only slightly beyond caudal-fin base (vs. maxillary barbel surpassing total length). The new species differs from P. ornatus and P. pictus by the uniform grayish to yellowish coloration (vs. presence of two bands or dark dots along flanks, respectively). Pimelodus halisodous differs from P. stewarti and P. joannis by having a longer pectoral-fin spine (20.0-23.5 vs. 15.4-19.6% SL); a longer snout (43.1-47.9 vs. 35.8-41.8% HL); and a larger number of premaxillary tooth rows (13-16 vs. 5-9).

mus; preventral profile of body slightly convex; anal-fin base straight. Head covered by thin skin. Skull roof ornamented with numerous small granulations, more visible in larger specimens. Snout not very long, projecting beyond mandibular symphysis by distance less than internarial length. Mouth subterminal; margins curved in ventral view when mouth closed and exposing less than anterior half of premaxillary tooth rows; upper lip thick, fleshy, striated. Fleshy rictal fold in pocket behind corner of mouth. Posterior nostrils closer to anterior orbital border than to anterior nostrils; anterior nostril with fleshy rim slightly raised posteriorly; posterior nostril thin, fleshy, with elevated rim. Eye large, elliptical, margin completely free and dorsolaterally positioned on head; horizontal orbital diameter greater than interorbital width; orbit oblong, horizontal orbital diameter greater than vertical orbital diameter. Premaxillary tooth patch short, broad, rectangular and transversely elongated; premaxilla with approximately 13-16 (n = 8) irregular rows of slender conical teeth; internal border of pre-maxilla concave. Four or five irregular tooth rows on dentary. Vomerine and pterygoid teeth plates absent. Anterior cranial fontanel triangular in dorsal view, open from mesethmoid to frontals, and terminating anterior to vertical through posterior margin of eye. Posterior cranial fontanel reduced to ovoid or circular foramen in center of supraoccipital in specimens smaller than 100 mm SL, and completely closed in larger specimens. Supraoccipital process wide; dorsal surface with longitudinal median crest, ornamented with numerous small granulations; lateral margins of supraoccipital process converging posteriorly, process covered by narrow sheath of opaque hyaline skin. Anterior and middle nuchal plates ornamented sparsely with tuberculated ridges.Anterior nuchal plate with short anterior process fitting into bifid supraoccipital tip. Posterior nuchal plate with short posterior process not trespassing line through origin of first branched dorsal-fin ray. Three pairs of barbels, each flattened at base. Maxillary barbel inserted at vertical through posterior edge of anterior nostril; slightly surpassing caudal-fin base. Mental barbels inserted anterior to gular fold apex, in curved line parallel to mandibular margin. Inner mental barbel reaching base of pectoral fin. Tip of outer mental barbels reaching middle pectoral-fin rays, almost to tip of pectoral spine. Gill membranes free, diverging just behind gular fold apex and supported by 7 branchiostegal rays. Gill rakers well-ossified, sharp and slen- der; 15-17 (mode = 15) on first branchial arch; 3-4 on epibranchial (mode = 3), 11-13 on ceratobranchial (mode = 12; n = 13). Dorsal fin rays II,6 (mode = 6; n = 13); fin inserted near anterior onethird of SL, its origin slightly posterior to vertical through tip of innermost pectoral-fin ray. Spinelet narrow, sharply angular or having low anterior crest. Dorsal spine straight, strong, pungent, shorter than first branched ray, continued in filamentous ray reaching nearly to edge of first soft dorsal-fin ray; its length approximately equal to pectoral-spine length. Dorsal spine sometimes with 1 or 2 anterior distal serrae (n = 9). Posterior margin of dorsal spine with moderately sharp retrorse spines distally, becoming gradually erect near spine base. First branched dorsal-fin ray longest, last dorsal-fin ray less than one-half-length of first ray; distal margin of dorsal fin nearly straight.Adipose fin large, slightly posterior to middle of body.Adipose-fin margin rounded and moderately deep, its apex near to vertical through anal-fin origin, ending posteriorly as short free lobe to vertical through tip of last anal-fin ray. Caudal fin i,7,8,i (n = 13) deeply forked, with pointed lobes; dorsal lobe slightly longer than ventral lobe, outer principal rays non-filamentous. Eighteen dorsal and 19 ventral procurrent caudal-fin rays. Anal fin inserted at posterior one-third of SL; fin margin slightly concave, not forming distinct lobe anteriorly; tips of longest anterior and posterior branched rays meet when depressed. Anal fin iv-v,7-8 (mode = 7; n = 13), last rays simple, first and second branched rays longest. Pectoral fin i,9-10 (mode = 9; n = 13); its posterior margin obliquely truncate; first soft ray longer than spine. Pectoral spine strong, continued in filamentous ray reaching nearly edge of first soft pectoral-fin ray. Pectoral spine distally pointed, dorsal and ventral surfaces smooth; numerous, regularly spaced, uniformly retrorse unicuspid dentations along most of posterior margin; anterior distal serrae weak or absent (larger in juveniles), antrorse and straight dentations along proximal half of anterior margin, becoming progressively less prominent and more crowded proximally; anterior dentations much larger in juveniles. Pelvic fin i,5 (n = 6); first branched ray longest, inserted near vertical through fifth and sixth branched dorsal-fin ray. Lateral-line canal complete, extending onto caudal-fin base; canal nearly straight, with superficial tubular ossicles directed posteroventrally and more developed anteriorly; no accessory laterosensory canals posterior to nuchal area. Posterior cleithral process broad, triangular, ventral margin nearly straight, dorsal margin somewhat concave; granular and osseous tubercles on lateral surface. Urogenital papilla short, located in shallow depression immediately posterior of anus. No apparent sexual dimorphism. Superficial ossifications of Weberian complex centrum not covering seventh centrum. Total vertebrae 41 (15 precaudal and 26 caudal). First pleural rib on sixth vertebra. Nine pairs of pleural ribs.

Color in alcohol. Body color grayish to yellowish. Ventral region brownish to light. Light narrow band along lateral line.

Head surface grayish to brownish. Eyes dark. Some specimens with several dark chromatophores on surface of posterior cleithral process, opercle and below orbit region; sometimes reaching body flanks; such chromatophores more concentrated on lower half of flanks below lateral line. Dorsal fin with black chromatophores on distal portion of rays 2-4. Pectoral, pelvic and anal fins hyaline, base sometimes yellowish. Adipose fin hyaline with minute uniformly scattered melanophores on distal portion. Black chromatophores along interradial membranes of caudal fin, concentrated on median portion of each caudal-fin lobe. Maxillary barbel dusky on dorsal surface; lighter on ventral surface. Mental barbels pale.

Distribution. Pimelodus halisodous is known from the upper and middle portions of the rio Tocantins drainage ( Fig. 2 ).

Etymology. The specific name, halisodous from the Greek adjective halis, meaning in crowds, in plenty, sufficient, enough, plus the Greek noun odous, meaning tooth. The name alludes to the several (ca. 15) irregular rows of conical and slender teeth on each premaxilla. A noun in apposition.

Figures

Fig. 3. Pimelodus halisodous, holotype, MCP 41738, 108.8 mm SL, rio Paranã, rio Tocantins drainage, Brazil.

Fig. 2. Rio Tocantins drainage showing the collection localities of Pimelodus stewarti (triangles, 1), P. halisodous (squares, 2), and P. joannis (circles, 3). Numbers represent type-localities. Some symbols represent more than one lot or locality.