Aphanotorulus unicolor ( Steindachner 1908 )

Ray, C. Keith & Armbruster, Jonathan W., 2016, The genera Isorineloricaria and Aphanotorulus (Siluriformes: Loricariidae) with description of a new species, Zootaxa 4072 (5), pp. 501-539 : 524-526

Aphanotorulus unicolor ( Steindachner 1908)

( Fig. 14 )

Plecostomus unicolor Steindachner, 1908: 164 . Type locality: Rio Purús. Lectotype: NMW 44271: 2, designated by Armbruster (1998b: 254).

Plecostomus madeirae Fowler, 1913: 571 , fig. 23. Type locality: Madeira River, about 200 miles east of W. long. 63º54'W, Brazil. Holotype: ANSP 39312.

Plecostomus popoi Pearson, 1924: 20 , pl. 3 (fig. 2). Type locality: Popoi River, Upper Río Beni, Bolivia. Holotype: CAS 77346.

Plecostomus micropunctatus La Monte, 1935: 1 , fig. 1. Type locality: Rio Purus: [...] in the vicinity of the mouth of Rio Macauhan, a tributary of Rio Iaco which, in turn, is a tributary of Rio Purus (70º15'W, 7º30'S). Holotype: AMNH 12598.

Plecostomus chaparae Fowler, 1940: 81 , figs. 38–40. Type locality: Boca Chapare, Río Chimore, Cochabamba, Bolivia. Holotype: ANSP 69067.

Aphanotorulus frankei Isbrücker & Nijssen, 1983: 108 , figs. 1–2. Type locality: [...] du Pérou, Dept. Ucayali, Prov. Coronel Portillo, système du Rio Aguaytia. Rio Neshua (environ 08º36'S, 74º50'W), 60 km S. O. de Pucallpa, le long de la route de Tingo Maria. Holotype: ZMA 116.640.

Material examined. See Armbruster and Page (1996) and Armbruster (1998).

Diagnosis. Aphanotorulus unicolor differs from all other members of Isorineloricaria , except A. ammophilus , by its numerous buccal papillae (vs. single, large papilla). Aphanotorulus unicolor is diagnosable from A. ammophilus by the absence of a ridge on the compound pterotic (vs. ridge present in A. ammophilus ). The urohyal is also uniquely modified in A. unicolor . The urohyal in A. unicolor has arms, which are thin and elongate, that overlap with the anterohyal (vs. short lateral arms of the urohyal that do not overlap the anterohyal in most other Loricariids) ( Armbruster 1998). In specimens larger than 75mm SL, A. unicolor has a larger orbit diameter to snout length ratio (28.0–42.2% vs. 18.5–27.9%), a larger caudal depth to pectoral spine length ratio (25.6–35.1% vs. 19.8–25.5%), and a smaller pectoral spine length to thorax length ratio (99.3–116.9% vs. 117.0–136.3%) than A. ammophilus ( Armbruster 1998) .

Description. Morphometric data given in Table 2 . Head slightly compressed with raised supraoccipital crest; crest ending abruptly with posterior edge perpendicular to head. Large flap covering posterior opening of nare. Interorbital surface flat. Nape increasing in height posteriorly.

Dorsal-fin spine slightly shorter than or equal in length to first dorsal-fin ray. Pectoral-fin spine even with point of insertion on pelvic fin. Pelvic fin spine comes even to insertion of the anal fin. Adipose-fin membrane extending to end of fourth adipose base plate.

Lateral line plates 28–32 (mode 29; n = 307); dorsal fin base plates six to nine (mode seven; n = 306); folded dorsal plates 10–13 (mode 12; n = 300); plates between dorsal and adipose fins six to 10 (mode eight; n = 305); adipose fin plates two to four (mode three; n =305); anal-fin base plates two to three (mode three; n =307); plates from anal fin insertion to last plate on caudal peduncle 13–16 (mode =14; n =307); plates in folded pectoral fin four to seven (mode five; n =302); number of teeth on dentary four to 18 (mode =12; n =302); number of teeth on premaxilla four to 17 (mode =12; n =304).

Sexual Dimorphism. Breeding males have elongate, unicuspid teeth. Hypertrophied odontodes also present on the posterior dorsal and lateral plates. Odontodes also present on the adipose- fin spine and upper caudal- fin spine.

Color in alcohol. Light tan to white background. Ventral surface white. Dorsal and lateral surfaces with dark, round spots. Spots small in size, less than half the width of the pupil. Spots form longitudinal rows in some specimens, more random in other specimens. Spots on caudal fin create vertical bars when fin is compressed. Spots on dorsal fin lie anterior to each dorsal fin ray.

Distribution. A wide-ranging species, with populations known from upper Amazon tributaries of Bolivia, Brazil, Colombia, Ecuador, and Peru ( Fig. 6 ).

Figures

FIGURE 6. Distribution of Aphanotorulus ammophilus and A. unicolor. Circles represent A. ammophilus, squares represent A. unicolor. Open shapes represent type localities. From Armbruster (1998).

FIGURE 14. Lateral, dorsal, and ventral view of Aphanotorulus unicolor, ZMA 116640 (Aphanotorulus frankei holotype), 105.4 mm SL Photographs by K. S. Cummings. Scale = 1 cm.