Rhinotocinclus dinizae ( Ribeiro-Silva, Silva, Venere, Silva & Roxo, 2020 ), 2022

Reis, Roberto E. & Lehmann A., Pablo, 2022, A new genus of armored catfish (Siluriformes: Loricariidae) from the Greater Amazon, with a review of the species and description of five new species, Neotropical Ichthyology (e 220002) 20 (2), pp. 1-100 : 89-90

Rhinotocinclus dinizae ( Ribeiro-Silva, Silva, Venere, Silva & Roxo, 2020) , new combination

( Fig. 46 ; Tab. 9 )

Hisonotus dinizae Ribeiro-Silva, Silva, Venere, Silva & Roxo, 2020:554 (Type-locality: Brazil, Mato Grosso state, municipality of Barra do Garças, córrego Grande, drainage of rio Pindaíba, rio Araguaia basin, -15.7417 -52.0936 [15°44’30.12”S 52°05’36.96”W]. Holotype: MZUSP 125790).

Diagnosis. Rhinotocinclus dinizae is distinguished from congeners, except R. acuen , R. chromodontus , and R. jumaorum , by having the dominant color pattern formed by a dark stripe from the snout tip, through the eye and extending to end of caudal peduncle (Fig. 7E; vs. dominant color pattern formed by dark bars separated and distinct, or dark bars wide and partially coalesced or closed together), and by having a V-shaped light mark from the snout tip to each nostril (Figs. 6C,D; vs. light mark absent, Y-shaped or present as two separate lines from snout tip diverging to each nostril). It is also distinguished from congeners, except R. acuen , R. chromodontus , R. hera , and R. jumaorum , by lacking an adipose fin or platelets at the adipose-fin position (vs. adipose fin or platelets present). Rhinotocinclus dinizae is further distinguished from R. hera by the smaller orbit (12.9–14.8% vs. 15.1–17.3% HL, 38.1–43.0% vs. 44.0–50.4% interorbital distance, and 23.8–28.0% vs. 29.2–32.5% snout length), and from R. acuen , R. chromodontus , and R. jumaorum by the longer head (40.0–41.8% vs. 37.0–40.0%, 36.2–38.5%, and 36.4–39.8% SL, respectively). Rhinotocinclus dinizae is further distinguished from R. acuen by having longer fins (dorsal-fin spine 22.8–25.5% vs. 20.0–22.8% SL, anal-fin unbranched ray 18.5–19.5% vs. 15.0–17.4% SL, and pectoral-fin spine 28.1–30.0% vs. 23.1–26.9% SL). It is further distinguished from R. chromodontus and R. jumaorum by the fewer teeth (16–19 premaxillary, 12–15 dentary vs. 26–40, 21–34, and 20–33, 18–28, respectively).

Geographical distribution. Rhinotocinclus dinizae is known from two localities in the upper rio Araguaia near Barra do Garças, Mato Grosso State, Brazil ( Fig. 43 ).

Remarks. Another species originally described as Hisonotus , it was compared to congeners and diagosed as “ Hisonotus dinizae differs from all congeners, except H. acuen , H. bockmanni , H. chromodontus , H. jumaorum and H. vespuccii by having a V-shaped spinelet...”. Except for H. vespuccii , which is probably a member of Otothyropsis , all remaining species are now transferred to Rhinotocinclus and the functional V-shaped spinelet indeed diagnoses R. dinizae , as well as all Rhinotocinclus and Curculionichthys species, from Hisonotus . Extintion risk of Rhinotocinclus dinizae is currently not assessed.

The holotype and MZUSP paratypes of Hisonous dinizae have never been sent to MZUSP after the species original description and were unavailable for the present study, possibly having been lost. Five paratypes (LBP 4932), however, were examined and compared to other Rhinotocinclus species.

Material examined. LBP 4932 , 4 + 1 cs paraypes (4 measured), córrego Correntes , rio Araguaia basin, Barra do Garças, Mato Grosso, Brazil, 15°29’59”S 52°12’12”W, 22 Mar 2007, P. C. Vênere & V. Garutti .

Figures

FIGURE 43 | Geographic distribution of Rhinotocinclus species of the R. chromodontus group in southern Amazon. Rhinotocinclus acuen (red dots); R. chromodontus (blue dots); R. dinizae (cyan dots); R. jumaorum (yellow dots). T = Type-locality.

FIGURE 46 | Rhinotocinclus dinizae, LBP 4932, 19.5 mm SL, paratype, córrego Correntes, rio Araguaia basin, Barra do Garças, Mato Grosso, Brazil.