Isorineloricaria tenuicauda ( Steindachner 1878 )

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 : 532-533

Isorineloricaria tenuicauda ( Steindachner 1878)

( Fig. 17 )

Plecostomus tenuicauda Steindachner, 1878a: 90 . Type locality: Magdalenen-Stromes [ Colombia]. Syntypes: MSNG 8856 (1), NMW 42596 (1), NMW 44263 (1), NMW 44264 (1), NMW 44265 (1), NMW 44266 (3), NMW 44268 (1), NMW 44294 (1), ZMUC P 30172 (1). One syntype illustrated in Steindachner (1879: pl. 6).

Plecostomus winzi Fowler, 1945b: 9 , figs. 4–7. Type locality: Honda, Colombia. Holotype: ANSP 71623. Distribution: Magdalena River basin, Colombia, known only from holotype ( Weber, 2003).

Material examined. Syntypes: NMW 44265 (1), Magdalena stream; NMW 44266 (3), Magdalena stream. Nontype material: Colombia: ANSP 71263 ( Plecostomus winzi holotype) (1); Honda, Rio Magdalena Basin, C. Miles, November 1940. CU 47928 (1), Lake San Sylvestre by city of Barranca-Bermeja, Santander, col. by F. Archer, J.D. Archer, 20 August 1964; FMNH 55169 (3); Soplaviento, Eigenmann. FMNH 76408 (1); Honda, Eigenmann. FMNH 76424 (1); Calamar Cienega, Eigenmann. FMNH 96234 (1); Puerto del Rio, Magdalena River, Cienega on Central Magdalena, M. Gonzales, 1913.

Diagnosis. Isorineloricaria tenuicauda can be diagnosed from from I. acuarius by having a smaller caudal peduncle width to pectoral spine length ratio (31.5–56.2% vs. 59.6–65.2%), which separates 95% of individuals; from I. spinosissima by having a larger caudal fin depth to head length ratio (see diagnosis of I. spinosissima ); and from I. villarsi , by a rounded ridge present on the compound pterotics (vs. sharp ridge). Isorineloricaria tenuicauda can be further diagnosed from A. ammophilus and A. unicolor by a single, large buccal papillae (vs. multiple buccal papillae); and from A. emarginatus and A. horriddus by having rounded ridges on the compound pterotics (vs flat compound pterotics).

Description. Morphometric data given in Table 6 . Head moderately deep with elevated supraoccipital crest; crest often ending sharply. Ridges formed on compound pterotics rounded in most specimens (lack a sharp ridge). Nape slightly increasing in height posteriorly.

Pectoral-fin spine reaches posterior to insertion of pelvic fin. Pelvic-fin spine reaches insertion of anal-fin spine. Adipose-fin spine triangular, adipose-fin membrane extending to third adipose fin plate (two plates separate adipose-fin membrane and first dorsal procurrent caudal fin spine).

Lateral line plates 28–29 (mode 28; n = 12); dorsal fin base plates seven to nine (mode eight; n = 12); folded dorsal plates 13–15 (mode 13; n = 12); plates between dorsal and adipose fins six to nine (mode eight; n = 12); adipose fin plates three to four (mode three; n =12); anal-fin base plates two to three (mode two; n =12); plates from anal fin insertion to last plate on caudal peduncle 15–17 (mode =17; n =12); plates in folded pectoral fin five to nine (mode seven; n =12); number of teeth on dentary 20–35 (mode =29; n =10); number of teeth on premaxilla 20–35 (mode =30; n =12).

Sexual Dimorphism. Breeding males with hypertrophied odontodes on pectoral-, adipose-, and caudal-fin spines, which increase in length and density distally. Small hypertrophied odontodes on the dorsal-fin spine. Hypertrophied odontodes also on the pectoral- and caudal-fin rays. Paired-fin spines swollen. Hypertrophied odontodes covering posteromedial edge of most plates along body, cheek plates, opercle, along snout, and cleithrum.

Color in alcohol. Background light brown or tan. Covered in small brown spots over entire body. Some specimens lack spots on abdomen. Spots small and uniform in size all over body, except abdomen and paired-fin rays. Spots on abdomen vary from small single spots to large fused spots with open centers (circles and semicircles). Some elongate (fused) spots on paired-fin rays. Two rows of spots between fin rays on paired fins. One row of spots between rays on caudal fin. Dorsal-fin membranes with randomly placed spots.

Juveniles without abdominal spots. Smallest spots on head, with increasing size posteriorly. Spots form bands in paired fins, dorsal fin and caudal fin.

Distribution. Isorineloricaria tenuicauda is restricted to the Río Magdalena basin, Colombia (Fig. 10).

Figures

FIGURE 17. Lateral, dorsal, and ventral views of Isorineloricaria tenuicauda, MSNG 8856 (syntype). Photographs by M. Allen. Scale = 3 cm.

Tables

TABLE 6. Selected morphometrics of Isorineloricaria tenuicauda and I. villarsi.

Isorineloricaria tenuicauda		Isorineloricaria villarsi
Measurement N Average SD	Range	N Average SD	Range
Standard Length (SL, mm) 12	41.5–516.9	16	85.5–516.9
% SL
Predorsal Length 12 37.8 1.9	34.5–40.8	16 35.7 3.2	29.2–41.8
Head Length (HL) 12 32.4 2.4	28.6–37.8	16 29.4 3.2	24.0–36.1
Cleithral Width 12 25.4 1.3	22.6–28.0	16 22.9 2.4	19.1–26.7
Dorsal spine Length 10 32.1 2.2	28.3–35.0	15 27.8 5.6	13.8–34.1
Folded dorsal-fin Length 12 40.3 1.5	37.2–42.3	16 37.1 2.4	31.2–40.1
Dorsal-fin base Length 12 25.9 1.8	21.0–28.7	16 23.8 1.7	19.7–26.4
Dorsal- adipose Length 12 20.5 1.5	17.6–22.7	16 22.0 1.5	18.3–24.2
Thorax Length 12 24.3 1.3	22.1–26.1	16 22.9 1.6	19.1–25.8
Pectoral spine Length 12 30.8 2.6	24.4–34.0	16 26.2 2.0	23.4–30.7
Abdominal Length 12 20.4 0.8	19.4–21.8	16 20.2 1.3	18.0–22.7
Pelvic spine Length 12 22.0 1.9	17.7–25.2	16 20.2 1.7	16.4–23.4
Postanal Length 12 37.0 2.0	31.2–38.7	16 40.1 3.3	34.1–45.8
Caudal peduncle Depth 12 8.2 0.7	6.8–9.2	16 7.4 1.0	6.3–9.1
Caudal peduncle Width 12 14.2 1.6	9.4–15.7	16 14.8 1.8	12.5–18.3
Adipose-fin spine Length 12 8.2 0.7	7.7–9.8	16 7.5 0.6	6.6–9.0
Anal-fin Length 12 16.0 1.2	14.0–18.0	16 14.6 1.8	10.6–16.9
Anal-fin base Length 11 4.4 0.6	3.2–5.5	16 4.5 0.5	3.6–5.3
Adipose- upper caudal Length 12 23.1 1.1	21.3–25.1	16 21.1 1.8	16.9–23.3
Adipose- lower caudal Length 12 26.6 1.2	24.7–28.5	16 25.0 1.5	21.1–26.6
%HL
Head Depth 12 58.4 2.3	54.4–62.8	16 55.7 2.8	50.6–62.0
Snout Length 12 56.6 1.7	52.7–59.0	16 57.1 2.5	53.1–62.6
Orbit Diameter 12 15.8 2.3	12.7–19.1	16 13.7 3.3	10.2–22.7
Interorbital Width 12 43.1 1.7	40.2–45.8	16 42.6 1.8	38.9–45.8
Snout opercle Distance 12 71.4 2.2	68.1–75.8	16 72.4 2.5	66.6–74.7
Head Width 12 81.4 4.1	71.5–86.9	16 79.4 2.5	74.6–85.6
Head eye Length 12 42.4 1.6	39.6–44.5	16 43.1 1.8	38.0–45.1
Eye nare Length 12 13.1 1.4	9.9–14.5	16 12.8 1.4	10.7–16.1
Internares Width 12 15.2 1.3	12.8–16.7	16 17.0 1.4	14.8–19.3
Snout nares Length 12 35.9 2.1	30.9–39.0	15 37.2 2.2	33.0–42.8
Snout pectoral Length 12 72.9 1.9	70.9–77.4	16 75.0 2.7	67.1–78.5
Pectoral orbit Distance 12 27.0 2.2	21.4–29.1	16 28.6 2.0	24.5–31.0
Mouth Width 12 38.3 2.6	34.9–42.4	16 38.5 2.6	32.6–42.8
Mouth Length 12 43.1 2.7	39.0–47.2	16 42.3 2.5	38.6–46.8
Dentary Length 12 12.2 1.3	10.1–14.1	16 11.9 1.1	10.4–14.5