Steindachneridion scriptum (Miranda Ribeiro, 1918)

Garavello, Julio Cesar, 2005, Revision of genus Steindachneridion (Siluriformes: Pimelodidae), Neotropical Ichthyology 3 (4), pp. 607-623 : 615-616

Steindachneridion scriptum ( Miranda Ribeiro, 1918) Fig. 7

Steindachneria scripta Miranda Ribeiro, 1918: 640 (732), lectotype: MZUSP 2286, 395 mm; paralectotype MZUSP 1236, 700 mm (dry). Type locality: Itaqui , rio Uruguay, Rio Grande do Sul State, Brazil .

Steindachneria scripta: Britski, 1969: 205 (lectotype designation).

Steindachneridion scripta: Gosline : 1945: 51 (ref.); Fowler, 1951: 604 (ref.); Burgess, 1989: 282: 842; Lundberg & Littmann in Reis et al., 2003: 443; López et al., 2003: 61; Zaniboni Filho et al, 2004: 111 (ref.).

Steindachneridion inscripta (error): López, Menni & Miquelarena, 1987: 27 (ref.); Sverlij et al., 1998: 63

Pseudopimelodus parahybae: Devincenzi & Teague, 1942: 42 , fig (rio Uruguay), (misidentification of S. scriptum ?).

Diagnosis. Steindachneridion scriptum differs from its congeners by having the combination of the following characters: supraoccipital process distant from anterior nuchal plate by length of one orbital diameter; premaxillary tooth plates united and with groove medially, slightly curved and sharp in distal region; vomer with single and oval shaped tooth plate; and 15 to 17 gill rakers on first branchial arch. Head depth shorter than head width (64.2 to 86.2%); and head width 21.1 to 26.0% of SL. Orbit small 21.2 to 31.7% of interorbital distance and 7.3 to 10.1% of HL; mouth large, its width 38.7 to 47.2% of HL. Lips thin, maxillary barbel long, surpassing pectoral fin tip and reaching vertical through dorsal-fin insertion. Ground color displaying body light grayish, abdomen whitish, with elongated or striated black blotches and dark dots irregularly scattered on head, trunk, rays and membrane fins. Caudal peduncle depth 32.0 to 41.5% of head length; caudal fin deeply notched; upper lobe larger than lower; both tips slightly rounded.

Description. Morphometric data presented in Table 2; maximum body length 774 mm SL. Snout large; snout tip almost rounded in dorsal view; snout length 11.8 to 13.8% of SL; each pair of nostrils slightly protruding on dorsal snout profile; anterior pair inserted more widely spaced apart than posterior pair. Head wide, almost rounded in dorsal view; head depth 64.2 to 86.2% shorter than its width and 13.7 to 19.8% of SL; head length 26.8 to 31.5% of SL. Dorsal profile of head almost straight from tip of snout to the nuchal plate; slightly depressed at the region between supraoccipital process and anterior nuchal plate; a distance near one orbital diameter long separate the supraoccipital from the nuchal plate. Eyes dorsally placed more near to tip of snout than opercular opening; orbit small, 7.3 to 10.1% of HL and 21.2 to 31.7% of interorbital distance.

Opercular opening large and strongly curved forward; branchial membranes joining at narrow isthmus; eight branchiostegal rays reduced in size; 15 to 17 gill rakers on first branchial arch. Lower region of head with an arrow-like, shallow gular fold; deep grooves on each side of lower jaw. Mouth large and terminal; lower jaw slightly shorter than upper jaw; mouth width 38.7 to 47.2% of HL; posterior postcleithral process short, reaching vertical line passing through beginning supraoccipital process; lips thin; all barbels narrow and depressed; maxillary barbel long, when adpressed, reaching vertical line passing through dorsal-fin insertion. Tooth plates of premaxillary and dentary with villiform teeth; each premaxillary and dentary bone has its own tooth patch; premaxillary tooth plates large, unite and with a median groove; abruptly narrowing and curved inward distally; single vomer tooth plate continuous, almost elliptical and circumscribed by the premaxillary tooth plate; single dentary thin tooth plate distally sharp.

Body profile deep convex between nuchal plate and caudal peduncle; base of dorsal-fin and anterior region of adipose fin straight; anterior region and insertion of adipose fin slanted; dorsal profile of caudal peduncle slightly concave from adipose fin to base of caudal-fin. Predorsal length 39.4 to 44.1% of SL. Ventral profile of body slanted from tip of snout to abdominal region, almost straight on pelvic and analfin insertions; lower caudal peduncle profile slightly concave. Preanal distance 70 to 75.7% of SL. Caudal peduncle at vertical through posterior tip of anal fin nearly rounded in crosssection. Dorsal-fin rays i,7(6); first two rays not pungent; dorsal fin base inserted in the dorsal space between the vertical through pectoral-fin terminus and vertical line through anal-fin origin; dorsal-fin locking mechanism present. Pectoral-fin rays i,9(10), first pectoral-fin ray not pungent and devoid of serrae; distal margin of fin straight; pectoral-fin short, when adpressed reaching vertical through base of first dorsal-fin ray. Pelvic-fin rays i,5; tip of unbranched pelvic-fin ray smooth and not pungent; slightly rounded distally; tip of pelvic-fin when adpressed surpass the anus, but not reach the anal-fin origin. Anal-fin rays i,8(9,10), pelvic-fin distal margin truncate. Caudal-fin deep notched; dorsal lobe larger than the ventral lobe and both tips slightly rounded; principal caudal-fin rays, i,15(14-16),i; caudal peduncle low, its depth 9.9 to 11.7% of SL.

Body and head except orbital region covered with thick skin; ventral surfaces of pectoral and pelvic girdle entirely covered by skin. Supraoccipital process short covered by thin skin and reaching the vertical through opercular opening; posterior postcleithral process short and entirely covered by skin.

Color in alcohol. Dorsal and lateral regions of body and head light gray and ventral region whitish; dorsal regions of head and trunk with small elongated or striated dark brown marks larger than one orbital diameter, irregularly scattered; juveniles with lateral small dark brown elongated marks and dots on dorsal surface of body. Eyes dark. Dorsal, pectoral, pelvic, anal and adipose fins uniformly dark gray with small black or dark brown elongated marks or large dots scattered on rays and membranes; adipose fin with several dark marks; caudal fin with dark dots on base of each lobe; dark gray distally.

Distribution. Known from upper rio Paraná, and rio Uruguay basins, Brazil ( Fig. 1 ).

Material examined. Rio Grande do Sul State: MZUSP 2286 (lectotype), 395 mm and MZUSP 1236, 700 mm (paralectotype), Itaqui, rio Uruguay, 1914. MCP 12629, 1, 426 mm SL, rio Uruguay at confluence of rio Pelotas and rio Canoas , Barracão, 10-11 Dec 1988 . Santa Catarina State: MCP 12993, 1, 327 mm SL, Itá , rio Uruguay, 7-8 Dec 1988 . São Paulo State: MZUSP 42846 , 1 , rio Pardo, no date. MZUSP 88015 7, 471 to 774 mm SL, Jaguara, rio Grande , cachoeira Mata-Doutor, downstream of Jaguara hydroelectric power dam, 21-29 Jul 1988 . MZUSP 88016 , 4 , 420- 570 mm SL, Piraju, rio Paranapanema , downriver from Paranapanema hydroelectric power dam, 2 Nov 2002 . MZUSP 88017 , 4 , 390- 460 mm SL, Piraju, rio Paranapanema , downriver from Jurumirim hydroelectric power dam, 25-26 Jan 2001 . LISDEBE 1161, 2, 387- 490 mm SL, rio Grande at confluence with the ribeirão dos Dourados, 26 Aug to 3 Sep 1988 . LISDEBE 1162, 1, 385 mm SL, Salto Grande, rio Paranapanema , near Salto Grande, Jan 1991 . LISDEBE 1163, 2, 298 and 320 mm SL, Piraju, rio Paranapanema , downriver of the Paranapanema hydroelectric power dam, 6-10 Jul 2000 . LISDEBE 1164, 3, 416- 508 mm SL, Piraju, rio Paranapanema , downriver of the Paranapanema hydroelectric power dam, 15 Jul 2003 .

Figures

Fig. 7. Lateral and dorsal views of S. scriptum. MZUSP 88015, 690 mm SL, Jaguara, rio Grande, cachoeira Mata-Doutor, downstream of Jaguara hydroelectric power dam, São Paulo, Brazil.

Fig. 1. Southeastern South America with the geographical distribution of Steindachneridion species. Each symbol may represent more than one sample.