Comprehensive Description

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Hypostomus taphorni (Lilyestrom 1984)

Fig. 22

Cochliodon taphorni Lilyestrom 1984 ZBK :43, figs. 8-9.

Material examined: VENEZUELA . Bolivar : Río Botanmo, Río Cuyuni dr. on the road to Bochinche, 07°25’N , 61°11’W , MCNG 8048, 1, (184.8, holotype ) , MCNG 8049, 1, (76.2, paratype ) . Caño Negro, Río Cuyuni dr. caño a little above Isla de Anacoco, 06°47’N , 61°12’W , MCNG 1452, 1, (181.7, paratype ) . Caño , Río Cuyuni dr. Highway 1, 20 river km above km 88 of El Dorado - Santa Elena road, MBUCV V-16491, 1, (151.6) . Caño Negro, Río Cuyuni dr. primary tributary of the Río Cuyuni above Isla Anacoco, 06°44’N , 61°09’W , MCNG 928 . Caño Quebrada Clara, Río Cuyuni dr. at the moth of Quebrada Clara at Anacoco, cerca the confluence with the Río Cuyuni, approx. 1 km up, 06°47’N , 61°10’W , MCNG 16901, 1, (149.1) . Caño Quebrada Clara, Río Cuyuni dr. below bridge cerca isla Anacoco, 06°42’N , 61°09’W , MCNG 16450, 1, (83.5) . Río Corumo, Río Botanmo - Río Cuyuni dr. 10 km E Tumeremo on road from Tumeremo to Bochinche (just after Fort Terembay), 07°25’00”N , 61°28’00”W , ANSP 168195, 7, 2 cs, (120.4-158.7) , MBUCV V-26824, 9, 2 cs, (115.9-197.1) , INHS 31768 , MCNG 29566, 1, (72.3) , and MCNG 16038, 1, (80.8) . Río Cuyuni, Río Essequibo dr. 10 km W km 88 of El Dorado - Santa Elena road, MBUCV V-16601, 1, (130.4) . Río Cuyuni, Río Essequibo dr. cerca de la Chalana de Anacoco, 06°43’N , 61°09’W , MCNG 11066, 1, (228.0) . Río Cuyuni, Río Essequibo dr. near Isla Anacoco, MCNG 7535, 1, (219.2) . Río Yuruari, Río Cuyuni dr. just E El Manteco, INHS 31600, 1, (87.2) .

Diagnosis: Hypostomus taphorni can be distinguished from all other members of the H. cochliodon ZBK group by the combination of having a bicolored caudal fin (light above, dark below) and small spots on the abdomen. Some specimens tentatively identified as H. plecostomoides from northern Bolivar State, Venezuela, have a bicolored caudal fin, but have medium to large spots on the abdomen (See Comments in H. plecostomoides ).

Description: See Hypostomus cochliodon ZBK group description for more details. Morphometric data given in Table 6. Body typically almost entirely dark brown with medium to large spots present. Spots on head fairly small when compared to H. plecostomoides , fading posteriorly and absent on caudal peduncle. Spots on abdomen very small (Fig. 22). Caudal fin bicolored, upper lobe tan and without spots, lower lobe black. Color in juveniles as in adults, but spots comparatively larger with spots on abdomen very light or absent.

Dorsal fin short, rarely reaching preadipose plate when depressed. Depressed pectoralfin spine ventral to pelvic fin reaches 2-3 plates beyond pelvic-fin rays. Tip of pectoral-fin spine of nuptial males with stout, recurved, hypertrophied odontodes.

Keels weak to moderately developed. Orbits forming ridge moderately raised above medial surface of head; ridges of dorsal and lateral aspect of head fairly well-developed. Longitudinal ridge on pterotic-supracleithrum beginning at posterodorsal corner of eye formed from raised bone and slightly larger odontodes absent. Opercle supporting up to 10 odontodes in juveniles; number of odontodes on the opercle decreases with age and many adults have no odontodes on the opercle. Nuptial body odontodes present (Fig. 2B). Plates in skin anterior to dorsal-fin spine absent or few (Fig. 6A; Table 7).

Each jaw with 6-12 teeth (mode = 10), teeth large and spoon-shaped. Average angle between dentaries 56° (SD = 7°; range: 44°-66°; N=13). Lateral line plates 27-29; dorsal plates 8-9; interdorsal plates 6-8; adipose caudal plates 8-10.

Range: From the Río Cuyuni drainage of Venezuela (Fig. 11). Recent collecting in Guyana suggests that H. taphorni is limited to the Cuyuni drainage and replaced by two undescribed species in the rest of the Essequibo river drainage. Hypostomus taphorni is allopatric to all other members of the H. cochliodon ZBK group (see Comments on page 43).

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