Bijdragen tot de Dierkunde, 55 (2): 242-248 — 1985 Lasiancistrus scolymus, a new species of mailed catfish from Rio Aripuanã, Est. Mato Grosso do Sul, Brazil (Pisces, Siluriformes, Loricariidae) by H. Nijssen & I.J.H. Isbrücker Institute of Taxonomic Zoology, University of Amsterdam, P.O. Box 20125, 1000 HC Amsterdam, The Netherlands Abstract holotypes and feel confident that they represent two distinct Lasiancistrus is described and species. scolymus n. sp. illustrated, the from Rio Rio based upon holotype Aripuanã, We Dr. H. A. Britski and Madeira Est. Mato do Brazil. It is are grateful to (MZUSP), to system, Grosso Sul, Mr. G. J. Howes (British Museum (Natural History), compared with Lasiancistrus heteracanthus (Günther, 1869), London, for access the material in their care. of the Lasiancistrus 1904. BMNH) to type-species genus Regan, Taxonomische Mr. L. A. van der Laan (Instituut voor Zoologie (Zoologisch Museum), Amsterdam, ZMA) Résumé made the photographs. Lasiancistrus scolymus n. est décrit et illustré, cette des- Financial for the visit Brazil the sp. support to was given to basée Rio cription étant sur l’holotype du Aripuanã, second author by the Treub Society for Tropical Research bassin du Rio Madeira, État Mato Grosso do Brésil. Sul, (Utrecht), the Artis Fund (Amsterdam), and by the Royal La nouvelle est Lasiancistrus espèce comparée avec Academy of Sciences of the Netherlands (Amsterdam). heteracanthus du Lasian- (Günther, 1869), espèce-type genre cistrus Regan, 1904. Lasiancistrus scolymus n. sp. (Figs. 1-3; table I-A) INTRODUCTION Material. — Holotype, MZUSP 26809, probably a nup- 143.6 Est. Mato tial male, standard length mm, Brazil, The holotype and single known specimen of the Grosso do Sul, Rio Aripuana, Humboldt (10°10'S describe here 59°27'W), Rio Madeira system, coll. J. G. Da Silva, species we as Lasiancistrus scolymus 16-X-1976. n. sp. was found in the ichthyological collection of the Museu de da Universidade de Zoologia — Latin kind Etymology. From the scolymus, a Sao Paulo visit of the (MZUSP) during a of the of different thistle; alluding to presence second author in 1983. January and head. sharp odontodes on the sides of snout According to Howes (1983), Lasiancistrus Regan, 1904, is a genus of the subfamily Description. — Morphometric data (taken Chaetostomatinae (incorrectly spelled Chaeto- according to the methods described by Heit- stominae inclusion 1983: in by Howes, 1983). With the mans et al., 34-35, fig. 1) are given of table I. 1-3 illustrate the of the new species, Lasiancistrus consists 24 Figs. holotype. with of about species (cf. Isbriicker, 1980; Heitmans et al., Interoperculum a clump 25 several of well known. 1983), which are not prominent evertible odontodes, anteriorly After in a comparison with various species (either about 3 mm long, increasing gradually size from specimens or from data in literature), La- posteriorly, the longest being about 15 mm. siancistrus The odontodes embedded in scolymus appears to us to be most are proximally a closely related with the type-species of the fleshy shaft, of which the thickness (on the L. heteracanthus which odontode the distal end of the genus, (Giinther, 1869), longest at shaft) the We have is 0.9 odontodes is known from holotype only. mm. These evertible are made a direct comparison between both whitish, except for their tips, which are bright 55 - 1985 243 BIJDRAGEN TOT DE DIERKUNDE, (2) in dorsal view. Fig. 1. Lasiancistrus scolymus n. sp., holotype in ventral view. Fig. 2. Lasiancistrus scolymus n. sp., holotype - SCOLYMUS N. SP. 244 H. NIJSSEN & I. J. H. ISBRUCKER LASIANCISTRUS The Two the anal fin yellow. tips are sharply curved toward the scutes are present along eleven between the anal fin and the anterior axis of the head, and acute distally. base, and fin The clump of evertible odontodes is bordered procurrent caudal spinule. These ventral (and partly mixed with) dorsally, anteriorly and scutes are also flattened. Posteriorly they are series of broader than the dorsal sides of the caudal ventrally by a extremely thin, often more feeble ventrolateral keel very long (stiff, hair-like) odontodes, up to peduncle, forming a on measured from the the last five behind the head are five about 12.5 mm long as scutes. Just distal end of the fleshy shaft. These "hairs" scutes at either side in transverse series. Dorsal fin anal fin fin have various distal positions. Some curve faint- I, 6, i; I, 4, i; pectoral fin caudal fin I. Five ly sideward, others backward, and still others I, 6; pelvic I, 5; I, 14, pro- caudal fin in front bend forward; some are straight. Like the ever- current spinules of the upper tible odontodes, the "hairs" are whitish and lobe, one in front of the lower lobe. Caudal fin the lower have minute, acute, yellow-coloured tips which slightly emarginate, be curved not. lobe than the may or being longer upper. shorter hair- Head and in front of the Similar, although considerably snout eyes rough, like odontodes the sides of where are present on the especially along the snout margin, anterior the leav- ossifications extend towards the snout to interopercular area, ventrally nar- ing a broad frontal area devoid of them. The row dorsal side of the upper lip. longest of these fragile odontodes are about 5.5 Cleithrum likewise rough, the remainder of mm. The opercular margin is provided with the head being smooth because of the minute twelve (at the right side, because of damage odontodes. Sutures of most ossifications of the most are lost at the left side) thin but promi- head are faintly visible, except for those on and with nent, erect or oblique odontodes, largest of along the snout. Body scutes longitudinal which 2.8 series measures mm. of prominent odontodes, those along their Lateral body scutes 25, including a margins larger than the others. Dorsum of first triangular scutelet on the caudal fin base. three pectoral fin rays and of first four pelvic fin scutelets the with odontodes. Small, triangular on caudal fin rays prominent base 7 (left side), 8 (right side) in vertical series. No continuous longitudinal series of promi- Predorsal scutelets between the odontodes the 5, supraoc- nent on body scutes. and the fin rim raised. cipital process procurrent dorsal Supraorbital hardly Supraoc- one at either side of the with a spinule: (a) supraoc- cipital posteriorly transversely straight median broad cipital process, (b) two large, scutes and process. median Abdomen line (with a faint suture, anteriorly reaching entirely naked. Lateral hardly the median supraoccipital process), (c) a pair of visible. more or less scutes faint Dorsum of its triangular (with a me- upper lip very narrow, naked, dian and smooth. side of this suture), (d) a narrow, curved predor- margin Ventral lip narrow, sal scutelet in front of leav- the procurrent predorsal with a transverse series of small papillae, smooth in teeth. The spinule. This scutelet reaches to the first of six ing a margin front of the scutes the dorsal fin followed of the continues without along base, by papillate part upper lip seven scutes between the dorsal fin and the interruption onto the lower lip. The lower lip is fin adipose spine (which is preceded by one papillate (except for its posterior margin, which is and for the base azygous scutelet, having a sharp posteromedial smooth, except a strip near the fin the elevation), one scute along adipose of the teeth); the larger papillae are those on middle of the the At spine, three scutes along the adipose fin mem- lip, beyond teeth. either and brane, two scutes between this membrane side there is a small, smooth, triangular max- and the caudal barbel. first procurrent fin spinule. illary These —between dorsal fin and the The is about 11 with scutes spine premaxilla mm, caudal fin base— are dorsally flattened. numerous small and slender teeth. The teeth BIJDRAGEN TOT DE DIERKUNDE, 55 (2) - 1985 245 3. Lasiancistrus head of in lateral and ventral view. Fig. scolymus n. sp., holotype dorsal, 246 H. NIJSSEN & I. J. H. ISBRUCKER - LASIANCISTRUS SCOLYMUS N. SP. sometimes dou- are arranged into an irregular, ble which is difficult to count row, accurately. The of the teeth is crown premaxillary sharply with bent inwards. The teeth are bifid, a larger, and truncate inner lobe a smaller, triangular outer lobe. and has The mandible is about 10 mm in numerous teeth, like those the premaxilla. The mandibular teeth have a large, elongate lobe and (rectangular to acute) inner a smaller, triangular outer lobe. Colour in alcohol. — Ground colour of of of naked ventral parts reddish tan, lips and ventral body scutes yellowish and greyish tan, minute respectively. Abdomenwith numerous, whitish, ill-defined markings. Sides and dorsum of head and body, and the brownish without fins are grey, markings. Comparison. — See Lasiancistrus heteracanthus, below. Lasiancistrus heteracanthus (Günther, 1869) (Fig. 4; table I-B) Chaetostomus heteracanthus Gunther, 1869: 425-426, figs. 3-4 (original description; type-locality: "Upper Amazons" and "Peruvian Amazons"; holotype). Material. — Holotype examined, BMNH 1869.5.21:3, standard 153 probably a nuptial male, length mm, Peru, Upper Amazon, coll. E. Bartlett. Fig. 4. Lasiancistrus heteracanthus (Günther, 1869), Comparison with Lasiancistrus scolymus.- reproduction of Günther’s original illustrations of the data in table I. 4 Morphometric are given Fig. holotype. is a reproduction of Gunther's (1869, figs. 3-4) original illustrations. Gunther (1869: 426) stated in italics: "In- Lateral body scutes 26 (left side), 27 (right scutelets the teroperculum with two kinds of spines, there side). Small, triangular on caudal of twelve slender but stiff in being a group about fin base 8 (both sides) vertical series. Predor- and slightly hooked spines surroundedby a ring sal scutes 4.