Isorineloricaria spinosissima ( Steindachner 1880 )

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 : 530-532

Isorineloricaria spinosissima ( Steindachner 1880)

( Fig. 16 )

Plecostomus spinosissimus Steindachner, 1880: 98 , pl. 5 (figs. 1, 1a). Type locality: Guayaquil [ Ecuador]. Holotype: NMW 55027.

Plecostomus festae Boulenger, 1898: 11 . Type locality: Rio Vinces and Rio Peripa, Equateur. Syntypes: BMNH 1898.11.4.32 (1), ZMUT 1518 (1).

Material examined. Ecuador: AUM 4251 (1); Los Rios, Rio Vinces, at Vinces, col. by T. Roberts, R. Gilbert, and F. Silva M., 5 November 1971. FMNH 58546 (3); Rio Duales, Colimes, A.W. Henn, 1913. FMHN 59369 (1); Guayaquil, A.W. Henn, 1913. MCZ 48773 (2); Fish market at Quevedo, 0˚59’S 79˚27’W, T.R. Roberts and party, 11 April 1971. MCZ 51699 (2); Rio Vinces at Vinces, Roberts, Gilbert, and Silva, 11 May 1971. MSUM 5205.4.A (2), Napo-Pastanza Provence, Ecuador, col. By C.M. Fugler, 1 September 1964.

Diagnosis. Isorineloricaria spinosissima can be diagnosed from Aphanotorulus and all other Isorineloricaria by having a smaller caudal fin depth to head length ratio (16.5–19.1% vs. 20.6–30.1%). Isorineloricaria spinossissima can be further diagnosed from A. ammophilus and A. unicolor by the presence of a single, large buccal papillae (vs. multiple buccal papillae present in A. ammophilus and A. unicolor ; and from A. emarginatus and A. horriddus by having rounded ridges on the compound pterotics (vs flat compound).

Description. Morphometric data given in Table 5 . Head moderately deep; elevated supraoccipital crest with posterior edge level with nape. Interorbital surface flat. Nape with increasing height from posterior edge of the supraoccipital to the insertion of the dorsal-fin spine. Extremely elongate caudal peduncle in adults; caudal peduncle circular in cross-section.

Pectoral-fin spine does not reach insertion of pelvic fin. Pelvic-fin spine does not reach point of anal fin insertion.

Lateral line plates 31–33 (mode 32; n= 11); dorsal fin base plates seven to eight (mode seven; n= 11); folded dorsal plates 10–14 (mode 13; n= 11); plates between dorsal and adipose fin nine to 11 (mode 10; n= 11); adipose fin plates three to four (mode four; n= 11); anal fin base plates two to three (mode two; n= 11); plates from anal fin insertion to last plate on caudal peduncle 19–21 (mode =20; n =11); plates in folded pectoral fin four to seven (mode four; n =11); number of teeth on dentary 19–31 (mode =19; n =11); number of teeth on premaxilla 17–34 (mode =29; n =11).

Sexual dimorphism. Breeding males with hypertrophied odontodes on all surfaces of body except ventral surface of head and abdomen. Odontodes present on pectoral, dorsal, adipose, and caudal- fin spines; odontodes increase in density and length distally on each fin spine.

Color in alcohol. Body background white to light tan. Spots numerous on dorsal and lateral surfaces. Spots dark brown; not uniform in shape and moderate to very dense, especially on head. Random spotting on paired fins. Dorsal fin with two rows of spots between each ray. Spots difficult to view in breeding males due to distortion caused by presence of breeding odontodes. Ventral surfaces without spots.

Juveniles with much lighter base color and very large dark spots. Spots randomly distributed on dorsal and lateral surfaces and all fins.

Distribution. Endemic to the Guayas River basin, Ecuador (Fig. 10).

Comments. Large ontogenetic shape change between juveniles and adults. Isbrücker (1980) suggested Plecostomus festae be recognized as a separate species from I. spinosissima due to their wide variation in shape and size; however, Weber (2003) recognized P. f e s t a e as a junior synonym of I. spinosissima . The ontogenetic shifts in shape most likely explain the wide variation in counts and measurements.

Figures

FIGURE 16. Dorsal, lateral, and ventral views of Isorineloricaria spinosissima, BMNH 1898.11. 4.32 (syntype of Plecostomus festae), 357.6 mm SL Photographs by C. Zawadzki.