Trichomycterus zonatus ( Eigenmann, 1918 )

Reis, Vinícius J. C. & Pinna, Mário De, 2019, The type specimens of Trichomycterus alternatus (Eigenmann, 1917) and Trichomycterus zonatus (Eigenmann, 1918), with elements for future revisionary work (Teleostei: Siluriformes: Trichomycteridae), Zootaxa 4585 (1), pp. 100-120 : 109-115

Trichomycterus zonatus ( Eigenmann, 1918)

( Fig. 5 , 6 )

Pygidium zonatum Eigenmann, 1918:330 , Agua Quente, Cubatao, 7 miles west of Santos, São Paulo, Brazil. [Holotype: FMNH 58573 (ex CM 7596), paratypes: FMNH 58572 (1, not conspecific with holotype and remaining paratypes; see Discussion below), 58574 (2)].

Description of type specimens. Paratype FMNH 58572 not conspecific with remainder of type series, see Discussion, and its discrepant characters indicated in relevant parts of description that follows. Morphometric data for holotype and paratypes in Table 2 . See figures 5 and 6 for general external aspect. Body cross-section oval, increasingly compressed posteriorly mainly along caudal peduncle. Body elongate with dorsal and ventral profiles slightly convex on trunk and then nearly straight to caudal peduncle. Body depth approximately even along length of body, slightly decreasing posterior to dorsal-fin origin.

Head depressed, as long as wide, trapezoidal in dorsal view. Width of head increasing slightly from snout to end of opercle. Levator mandibulae well-developed, more markedly so in holotype than in paratypes. Mouth subterminal. Upper lip convex, covered with numerous small and short papillae internally and externally. Premaxillary teeth arranged in three well-defined but irregular rows. Dentary teeth arranged in three irregular rows with inner one extending posteriorly to coronoid process. Lower lip well developed, convex and covered with small and short papillae internal and externally, with lateral fleshy folds adjacent to rictal-barbel base. Anterior nostril closer to upper lip than to anterior margin of eye, surrounded by membrane forming short tube continuous with nasal barbel base. Posterior nostril anteriorly surrounded by thin, crescent flap of integument. Maxillary barbel extending to gill opening but not reaching pectoral-fin origin. Rictal barbel shorter than maxillary barbel, extending to vertical through posterior margin of eyes but not reaching posterior margin of interopercular patch of odontodes. Nasal barbel extending to perpendicular through posterior margin of opercular patch of odontodes.

Eye large, without free orbital rim, located at anterior half of head length and on dorsolateral region of head. Elliptical ocular capsule formed by thin and translucent skin not adhered to surface of eyeball. Interorbital space slightly convex transversally, equivalent to approximately twice, or slightly less, orbital diameter.

Opercular patch of odontodes dorsolaterally located on head, posteriorly surrounded by fold of integument, with posterior margin almost reaching vertical through anterior margin of base of first pectoral-fin ray, and 10 [1], 14* [2], 15 [1, FMNH 58572] conical odontodes. Interopercular patch of odontodes ventrolaterally located on head, large, about twice as deep as opercular patch, with 15 [1], 17 [1], 27 [1, FMNH 58572] conical odontodes (holotype not counted due to condition of specimen). Branchiostegal membranes thick, narrowly joined to isthmus medially and forming large free fold. Branchiostegal rays eight in holotype FMNH 58573, paratypes FMNH 58574 and seven in paratype FMNH 58572, largest rays visible through skin.

Pectoral-fin rays I + 6* [3] in holotype FMNH 58573 and paratypes FMNH 58574 specimens; I+7 [1, FMNH 58572 ]. Distal margin of pectoral fin straight or slightly convex; first ray not prolonged as filament (prolonged as filament in FMNH 58572 ). Anterior portion of pectoral-fin base not covered by branchial membrane. Axillary gland pore dorsal to base of first pectoral-fin ray, anteroventral to first lateral-line pore, larger than lateral-line pores. Pelvic-fin rays I+4 [4], plus pelvic splint. Distal margin of pelvic fin covering, but not surpassing, anus. Base of pelvic fin positioned close together in FMNH 58573 , FMNH 58574 , and separated by one eye diameter in FMNH 58572 . Dorsal-fin rays iii+II+7 [3, including FMNH 58572 ]*, ii+II+7 [1]. Dorsal fin convex distally, on posterior half of the body, with origin slightly anterior to vertical through origin of anal fin. Dorsal-fin pterygiophores 8[4]. First pterygiophore anterior to neural spine of 17 th post-Weberian vertebrae, except for specimen FMNH 58572 , anterior to 16th. Anal-fin rays iii+II+5 [1]*, ii+II+5 [2], i+II+5 [1, FMNH 58572 ]. Distal margin of anal fin convex. Anal-fin pterygiophores 6[4]. First pterygiophore anterior to hemal spine of 21 th post- Weberian vertebrae, except for specimen FMNH 58572 , anterior to 20 th. Caudal-fin rays 6+7 [4]. Caudal fin with posterior margin ranging from straight to slightly convex with round dorsal and ventral corners. Post-Weberian vertebrae 38 [3]*, 36 [1, FMNH 58572 ]. First post-Weberian vertebrae nearly half length of subsequent ones. Second post-Weberian vertebrae with wide, short parapophyses. Ribs 11 [2, FMNH 58572 ], 13 [2] *.

Cephalic lateral line canals with simple, non-dendritic tubes ending in single pores. Supraorbital canal mostly within frontal bone. Supraorbital pores invariably present: s1 medial to nasal-barbel base and autopalatine, s3 medial to posterior nostril and anterior to frontal, and s6 paired posteromedial to eye and at midlength of frontal. Paratype FMNH 58572 with single median s6 pore. Infraorbital canal consisting of posterior segment only. Infraorbital pores i10 and i11 located posterior to eye and anterolateral to postorbital process of sphenotic-prooticpterosphenoid. Paratype FMNH 58572 with i1 and i3. Otic canal without pores. Postotic pores: po1, anteromedial to opercular patch of odontodes and lateral to joint between sphenotic-prootic-pterosphenoid and pterotic, and po2, medial to opercular patch of odontodes and lateral to joint between pterotic and posttemporo-supracleithrum. Lateral line of trunk anteriorly continuous with postotic canal and reduced to short tube, apparently non-ossified as seen in stereo radiographs ( Fig. 7 ). Lateral line pores invariably present: ll1 and ll2 dorsally to pectoral-fin base.

Coloration in ethanol ( Figs. 5 and 6 ). One of the paratypes (FMNH 58572) from Rio Cubatão belongs to a species different from the holotype and two other paratypes, from Rio Ribeira de Iguape (see Discussion). They are therefore described separately below.

Holotype and paratypes FMNH 58574 . General dark pigmentation of body forming variable nebulous, broadly confluent pattern of dark markings. Broad irregular midlateral band along flanks, extending continuously to base of caudal fin (holotype and one paratype FMNH 58574 ; Fig. 5A, B ) or to vertical through end of dorsal-fin base (second paratype 58574; Fig. 5C ). Caudal peduncle predominantly dark across entire depth in holotype and one paratype FMNH 58574 ( Fig. 5A, B ), almost entirely obliterating light background color, which remains encroached as few light patches and thick vermiculations. Caudal peduncle in second paratype FMNH 58574 with three large isolated dark blotches irregularly disposed along midline, last one over hypural plate, and smaller dark markings near dorsal and ventral margins of peduncle. Dorsum with broad continuous band or sequence of large round blotches, interposed with smaller ones. Head with dark covering mostly continuous with that of trunk dorsally ( Fig. 6 ). Region corresponding to neurocranium especially dark due to superimposition of brain pigment plus integument dark pigment. White areas dorsally or anterodorsally to opercular patch of odontodes and lateral portion of cheeks. Nasal and maxillary barbels with irregular covering of dark chromatophores, forming occasional faint spots. Rictal barbel mostly without dark pigment. Opercular patch of odontodes markedly dark. Interopercular patch of odontodes white or with faint dark field along dorsal margin. Caudal fin with dark spots roughly aligned vertically. Dorsal and pectoral fins with randomly distributed irregular spots, especially near bases. Anal and pelvic fins with few faint dark fields near bases. Abdomen without dark pigment .

Paratype FMNH 58572. Dark pigment mostly faded and further obscured by overlying layer of old coagulated and darkened mucus, detached or removed in some areas (cf. right and left sides of head in Fig. 6D ). Sides of body with series of eight large roundish isolated blotches, roughly along midlateral line, last one over hypural plate. Dorsum with series of large spots roughly aligned with dorsal midline. Head with dark covering similar in density to that of dorsum, with denser concentrations posterior to eyes. Pigmentation of opercular and interopercular patches of odontodes not differentiated from rest of head. Few remaining dark chromatophores on fins indicate that dark pigment was present, but no pattern is apparent due to advanced fading.

Figures

FIGURE 5. Trichomycterus zonatus, lateral views. A—holotype, FMNH 58573, 52.3 mm SL, Água Quente; B and C, paratypes, FMNH 58574, 42.8–46.9 mm SL, same locality as holotype (specimen C illustrated in Eigenmann (1918, pl 51, fig 1)); D—paratype, FMNH 58572, 50.7 mm SL, Cubatão, 7 miles west of Santos, São Paulo, Brazil.

FIGURE 6. Trichomycterus zonatus, heads in dorsal views. A—holotype, FMNH58573, 52.3 mm SL, Água Quente; B and C, paratypes, FMNH 58574, 42.8–46.9 mm SL, same locality as holotype; D—paratype, FMNH 58572, 50.7 mm SL, Cubatão, 7 miles west of Santos, São Paulo, Brazil.

FIGURE 7. Stereo triplet of Trichomycterus zonatus holotype FMNH58573. 3D effects: A+B, dorsal view; B+C, ventral view. See text (Material and Methods) for further explanation.