Rhinotocinclus pentakelis ( Roxo, Messias & Silva, 2019 ), 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 : 70-73

Rhinotocinclus pentakelis ( Roxo, Messias & Silva, 2019) , new combination

( Fig. 39 ; Tab. 8 )

Parotocinclus pentakelis Roxo, Messias & Silva, 2019:347 (Type-locality: Brazil, Tocantins State, municipality Lavandeira, Rio Palmas, Rio Tocantins basin; 12°48’05”S 46°28’38”W. Holotype: MZUSP 124900).

Diagnosis. Rhinotocinclus pentakelis is distinguished from all congeners, except for R. bockmanni , R. dani , R. hera , R. marginalis n. sp., and R. loxochelis n. sp. by having the dominant color pattern formed by dark bars on body well separated and distinct (Fig. 7D; vs. dominant color pattern formed by wide dark bars partially coalesced or closed together, or formed by a dark stripe from the snout tip, through the eye and extending to end of caudal peduncle); having two separate light lines from snout tip diverging to each nostril (Figs. 6E,F; vs. light lines on snout absent, Y- or V-shaped); and by having teeth with yellow cusps (Fig. 5C; vs. cusps light ochre or brown). Rhinotocinclus pentakelis is further distinguished from R. britskii , R. discolor , R. eppleyi , R. isabelae , R. kwarup , R. longirostris , R. pilosus , R. polyochrus , R. variola , and R. yaka by lacking an adipose fin (vs. adipose fin present). Rhinotocinclus pentakelis is further distinguished from congeners, except R. bockmanni , R. dani , R. loxochelis n. sp., and R. marginalis n. sp., by having small platelets at adipose-fin position (vs. small platelets absent). Rhinotocinclus pentakelis is distinguished from R. bockmanni by lacking a triangular dark spot at the dorsal-fin membrane (vs. dorsal-fin dark spot present), and by having a conspicuous dark bar 2 on body (vs. bar 2 absent or inconspicuous). It is distinguished from R. hera by having small platelets at adipose-fin position (vs. small platelets absent) and yellow teeth cusps (vs. light ochre cusps); and from R. dani by the deeper body (body depth 18.4–20.8% vs. 16.3–18.3% SL; caudal peduncle depth 10.1–11.7% vs. 8.8–9.9% SL; head depth 43.6– 49.5% vs. 38.0–43.5% HL), and longer dorsal-fin spine (27.0–30.8% vs. 24.0–27.0% SL). Rhinotocinclus pentakelis is further distinguished from R. loxochelis n. sp. by the regularly arranged dark bars on body (vs. dark bars on body somewhat fragmented and inclined, such that they connect to form a zig-zag pattern), and the comparatively shorter head (head length 37.5–39.7% vs. 39.3–41.3% HL); and from R. marginalis n. sp. by the comparatively deeper caudal peduncle (10.1–11.7% vs. 9.1–10.1% SL and 26.3–29.7%; vs. 23.3–26.3% HL).

Geographical distribution. Rhinotocinclus pentakelis is only known from two localities in tributaries to the rio Tocantins in the state of Tocantins, Brazil ( Fig. 36 ).

Remarks. In the original description, Parotocinclus pentakelis was named and diagnosed from remaining Parotocinclus species, except P. dani , by possessing five conspicuous dark bars on body, compared to three or four dark bars of other Parotocinclus species. In fact, however, remaining Amazon basin Parotocinclus , now all transferred to Rhinotocinclus , possess five dark bars (Fig. 7). Extintion risk of Rhinotocinclus pentakelis is currently not assessed.

Material examined. MCP 54394, 36 (16 measured) + 2 cs, rio Palma at Lavandeira, rio Tocantins basin, Tocantins, Brazil, 12°47’41.03”S 46°30’46.20”W.

Figures

FIGURE 36 | Geographic distribution of Rhinotocinclus species of the R. bockmanni group in southeastern Amazon basin. Rhinotocinclus bockmanni (black dots); R. dani (red dots); R. hera (pink dots); R. loxochelis n. sp. (blue dots); R. marginalis n. sp. (white dots); R. pentakelis (yellow dots). T = Type-locality.

FIGURE 39 | Rhinotocinclus pentakelis, MCP 54394, 23.4 mm SL, female, rio Palma at Lavandeira, rio Tocantins basin, Tocantins, Brazil.

Tables

TABLE 8 | Descriptive morphometrics of Rhinotocinclus species. Values given as percent of standard length or head length. Range includes the holotype (Hol), SD = standard deviation.

	R. pentakelis n = 16					R. marginalis n = 13					R. loxochelis n = 9
Character
	Low	High	Mean	SD	Hol	Low	High	Mean	SD	Hol	Low	High	Mean	SD
Standard length (mm)	18.1	23.6	21.2		19.6	18.2	20.8	19.4		22.6	20.3	23.1	21.6
Percent of SL
Body depth	18.4	20.8	19.5	0.80	17.7	16.5	18.7	17.9	0.62	18.7	18.3	20.4	19.4	0.70
Predosal distance	47.1	49.5	48.1	0.79	47.8	43.6	49.8	47.7	1.45	50.0	48.7	52.8	50.5	1.55
Prepelvic distance	42.0	45.2	43.6	0.83	45.2	43.1	46.7	44.7	1.11	44.1	42.8	46.4	44.3	1.19
Preanal distance	62.4	66.6	64.3	1.20	62.9	56.4	65.1	62.9	2.22	65.0	61.7	66.2	63.9	1.27
Preadipose distance	-	-	-	-	-	-	-	-	-	-	-	-	-	-
Dorsal-fin spine length	27.0	30.8	28.8	1.24	23.1	21.9	25.7	24.1	1.18	25.7	23.2	27.6	25.4	1.29
Anal-fin unbranched ray length	18.4	21.8	19.7	0.90	18.0	17.0	19.9	18.6	0.77	17.3	17.1	19.0	18.0	0.73
Adipose-fin spine length	-	-	-	-	-	-	-	-	-	-	-	-	-	-
Pectoral-fin spine length	28.8	33.5	30.6	1.23	28.7	28.3	30.3	29.2	0.58	32.1	30.4	32.1	31.2	0.63
Caudal peduncle depth	10.1	11.7	10.7	0.42	9.2	9.3	10.0	9.6	0.23	10.5	10.3	11.2	10.8	0.31
Dorsal-adipose fin distance	-	-	-	-	-	-	-	-	-	-	-	-	-	-
Dorsal-fin base length	11.1	13.1	12.5	0.46	12.1	11.4	12.4	12.0	0.27	11.9	11.8	13.5	12.6	0.66
Lower caudal-fin principal ray	26.9	34.6	29.9	1.88	27.4	27.4	31.5	29.0	1.37	27.4	24.5	29.2	27.0	1.51
Cleithral width	25.4	27.5	26.2	0.53	25.6	24.6	27.2	25.8	0.67	26.2	26.1	27.4	26.8	0.50
Head length	37.5	39.7	38.3	0.61	39.2	38.0	40.8	39.3	0.97	39.3	39.3	42.1	40.4	0.79
Percent of HL
Head depth	43.6	49.5	47.1	1.70	45.2	40.2	46.1	44.0	1.83	49.4	44.3	49.4	46.8	1.75
Interorbital distance	36.9	40.9	39.1	0.94	34.8	34.8	37.6	36.1	0.86	42.3	38.8	43.9	42.1	1.46
Orbital horizontal diameter	15.9	18.2	16.7	0.62	16.7	14.9	17.5	16.2	0.72	17.5	15.9	18.1	17.3	0.63
Snout length	49.2	53.3	51.0	1.05	51.4	47.9	53.1	50.7	1.27	50.0	49.4	52.3	51.0	0.98
Internarial distance	7.6	12.3	9.7	1.55	12.4	8.2	13.2	11.1	1.30	14.4	11.8	14.4	13.0	0.80
Tooth count
Premaxilla	15	22	18.3	1.69	14	12	18	15.5	1.71	20	16	22	19.9	1.83
Dentary	14	21	16.8	1.81	13	11	16	13.3	1.25	17	15	19	16.9	1.27