Hypostomus perdido, Zawadzki & Tencatt & Froehlich, 2014

Zawadzki, Claudio H., Tencatt, Luiz F. C. & Froehlich, Otávio, 2014, A new unicuspid-toothed species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the rio Paraguai basin, Neotropical Ichthyology 12 (1), pp. 97-104 : 98

Hypostomus perdido , new species

Figs. 1-2a,c

Hypostomus sp. 2-Rio Perdido NUP 4249: Cereali et al., 2008: 587

(cytogenetic data, karyotype).

Holotype. MZUSP 111064, 159.1 mm SL, Brazil, Mato Grosso do Sul, Bodoquena, rio Paraguai basin, rio Perdido , 21°17’09”S 56°41’47”W, 8 Sep 2005, O. Froehlich.

Paratypes. All collected with the holotype (61 specimens) . ANSP 193370 , 2 , 163.6 - 171.3 mm SL . CPUFMT 1500 , 2 , 152.5 - 170.3 mm SL . INPA 37689 , 1, 144.4 mm SL . MCP 47141, 2 , 133.9 - 147.9 mm SL . MNRJ 40094 , 2 , 126.0- 153.1 mm SL . NUP 12143, 10 , 136.4 - 166.3 mm SL . NUP 12144, 18 , 109.1 - 152.4 mm SL . NUP 14406, 1 c&s, 124.0 mm SL . ZSM 41828, 1, 149.5 mm SL . ZUEC 7254 , 2 , 140.2 - 141.7 mm SL . ZUFMS-PIS 1468 , 20 , 126.6 -181.0 mm SL .

Diagnosis. Hypostomus perdido is distinguished from all congeners, except H. fonchii , by having unicuspid teeth (vs. bicuspid teeth). From H. fonchii it is distinguished by having fewer dermal plates in the median series of lateral plates (26- 27 vs. 28), fewer premaxillary teeth (7-10 vs. 18-21), fewer dentary teeth (8-13 vs. 18-25), a more depressed head (head depth 15.8-18.1% in SL vs. 19.1-22.0%), and by the presence of median buccal papilla (vs. its absence).

Description. Measurements and counts in Table 1 . Dorsal profile of head convex from tip of snout to supraoccipital posterior end; straight from that point to dorsal-fin origin. Head elevated and compressed. Snout narrow and compressed, covered by irregular series of several small plates. Mesethmoid forming conspicuous bulge from snout tip to nares. Upper orbital margin not elevated. Eye laterodorsally positioned. Interorbital region wide and flat in frontal view. Very slender keel on upper portion of pteroticsupracleithrum just posterior to orbit. Opercle considerably large and somewhat ellipsoidal; its horizontal length similar to orbital diameter; odontodes slightly larger on posterior margin. Predorsal region almost flat; usually with one single larger plate surrounding supraoccipital followed by two narrow plates in front of dorsal-fin spinelet. Dorsal profile of trunk tapering straight from dorsal-fin insertion to caudal peduncle posterior portion; ascending to caudal fin. Adipose fin long, almost same length of minimum caudal peduncle depth. Maximum body width at region of dorsal-fin origin; profile gradually tapering from this point to caudal fin. Caudal peduncle somewhat ellipsoid in cross-section; dorsal and ventral caudal peduncle region slightly flattened.

Dorsal fin II,7; distal margin slightly convex to straight; origin at vertical two plates before pelvic-fin insertion; adpressed rays not reaching adipose-fin spine. Pectoral fin I,6; distal margin straight and almost reaching from one-third to half pelvic-fin length, odontodes more developed on distal dorsal region. Pelvic fin I,5; distal margin straight to slightly convex; distal portion of unbranched pelvic-fin ray reaching or slightly surpassing anal-fin insertion when adpressed to body. Anal fin I,5; distal border rounded. Caudal fin I,14,I, posterior margin truncate to slight emarginated; lower lobe slightly longer than upper lobe. Vertebrae 27; ribs 9, first rib relatively larger than others.

Dorsal and lateral surface of head and body covered with dermal plates, except snout tip and area surrounding dorsal-fin base. Plates on lateral margin of head, from snout tip to pterotic-supracleithrum small and irregular. Five lateral series of plates on trunk. Dorsal, mid-dorsal, median, midventral and ventral series without keels. Lateral line complete on median lateral series. Mid-ventral series moderately bent on anterior portion. Ventral region of body with small platelets bearing odontodes, except area beneath lower lip, insertion of pectoral and pelvic fins, and anterior region of anus. Naked areas reduced on larger specimens. Lips round; covered with dense papillae, which decrease in size to distal border. Median buccal papilla sensu Armbruster (2003, fig. 3) present. Buccal skin internally bordering premaxilla and dentary with unorganized series of flat enlarged papillae ( Fig. 2a,c ). Maxillary barbel elongate and proximately joined to labial border by membrane; distal tip free. Premaxilla with 7 to 10 teeth, dentary 8 to 13 teeth; teeth robust, moderate in length, unicuspid, crown short and continuous to stalk (without notch between stalk and crown). Dentary rami straight and angled 82 to 94° from each other (n = 20 specimens; mean = 85.8°).

Figures

Fig. 1. Hypostomus perdido, holotype, MZUSP 111064, 159.1 mm SL, Brazil, Mato Grosso do Sul State, Bodoquena, rio Paraguai basin, rio Perdido. Dorsal (top), lateral (middle), and ventral (bottom) views.

Fig. 2. Mouth and right dentary close up of Hypostomus perdido, paratype, CPUFMT 1500, 170.3 mm SL (a and c) and of Hypostomus fonchii UMSS 00360, 154.0 mm SL (b and d), respectively.