Austrofundulus rupununi, Tomas Hrbek, Donald C. Taphorn & Jamie E. Thomerson, 2005

Tomas Hrbek, Donald C. Taphorn & Jamie E. Thomerson, 2005, Molecular phylogeny of Austrofundulus Myers (Cyprinodontiformes: Rivulidae), with revision of the genus and the description of four new species., Zootaxa 825, pp. 1-39 : 15-18

Austrofundulus rupununi new species

Figures 7 and 8

Austrofundulus limnaeus Schultz 1949. Taphorn and Thomerson 1978:415, 420-421 as “Guyanan Populations”, Table 13.

Holotype. FMNH 108226 (ex FMNH 92580). Adult male (38.2 mm) collected in an Arapari area on Louis Orella's Manari Ranch, 9th District, Guyana, approximately 4 miles due west of ranch house by L. Orella, D. and A. Melville, J. E. Thomerson, D. C. Taphorn and D. Hicks on 12 August, 1975.

Paratypes. FMNH 92580, twenty three additional specimens collected at the type locality together with the holotype. MCNG 52001, four specimens collected at the type locality together with the holotype. UMMZ uncatalogued (2 specimens), Rupununi, flooded roadside cut south of Grami Pond. 15 July 1971, F. Cichocki, B. Carlson. UMMA uncatalogued (1 specimen) Rupununi, ditch 1.5 miles south of Pirara Ranch, 22 July 1971, F. Cichocki, B. Carlson.

Diagnosis. Austrofundulus rupununi is distinguished from all other species of Austrofundulus by the presence of black to dark brown humeral spots above the pectoral fin, iridescent blue-green dorsal fin with black edges, showing approximately five curved rows of dark spots, and iridescent blue-green caudal fins, with scattered black pigment. Compared with other species of the “ limnaeus ” group, A. rupununi have larger scales reflected in the counts as significantly fewer lateral, transverse, caudal peduncle and breast scales; they also have fewer dorsal, and pectoral fin rays than other Austrofundulus species; as well as the greatest caudal peduncle depth of any Austrofundulus species.

Description. The males have an iridescent blue-green dorsal fin with black edges, showing approximately five curved rows of dark spots. Females have clear dorsal fins with light gray spots. Males have iridescent blue-green caudal fins, with scattered black pigment. The color is more intense proximally; distally the fin is dark gray. Both the dorsal and the ventral edge of the caudal fin extend to form a “lyre-tail”. Females have clear to light brown caudal fin. The anal fin of males is similar to the dorsal and caudal fins. A background of iridescent blue-green near the base is broken with about three bars of dark brown, with start at the base and curve out anteriorly, away from the body. The distal third of the anal fin is sometimes brown or sooty gray, but the proximal blue-green background may extend all the way to the distal edge. Females have clear light brown anal fins, with four to five brown spots. Both the pectoral and pelvic fins of males are reddish-brown, with easily visible rays. The pectoral and pelvic fins of females are clear or light gold. The sides of the body of males are complexly patterned. The reddish-brown background gets progressively darker from ventral to dorsal surface. Behind and above the pectoral fin are several (6-20) irregularly shaped spots of black, dark brown or maroon color. On the sides of the body, just anterior of the dorsal fin, there are vertical rows of iridescent blue-green scales. In some individuals these align to form vertical bars of blue-green alternating with reddish-brown. These colorful scales continue out onto the caudal peduncle. In females, the basic color is plain light brown, but a few individuals have an occasional blue-green scale. As in males, the abdomen of females is lighter than the rest of the body. Morphometric data are given in Table 4. Largest Austrofundulus rupununi male: 41.2 mm SL, mean: 36.6 mm SL. Females attain about equal size. Dorsal profile of head strongly convex, rapidly increasing posteriorly. Head smaller and less deep than in other species of the A. limnaeus group. Convex dorsal profile continued through dorsal fin base. Ventral profile of head convex, straightening posteriorly to anal fin. The double convexity makes the body robust with greatest body depth between pectoral fin base and dorsal fin origin. Caudal peduncle very deep, the deepest seen in the “ A. limnaeus ” species group. Lower jaw prominent, extended beyond upper jaw. Dorsal and anal fins slightly pointed in males, rounded in females. Caudal fin with extensions of upper and lowermost rays forming a slight “lyretail ”. Head scale pattern variable, but most individuals show the “E” pattern (Taphorn and Thomerson 1978, figure 2H, pg. 444). Neuromasts on top of the head arranged in opposing pairs in the form of a lyre. Lateral line is complete.

Etymology. Named after the Rupununi savannah, Guyana.

Distribution. Known only from the Rupununi savannah in Guyana, of the upper Tacutu River drainage which flows into the Branco and is part of the Amazon River Basin. This species is expected to occur to the south in the savannahs surrounding Boa Vista, Roraima, Brazil, but to date no Austrofundulus has been confirmed in this region. It is the only Austrofundulus known from an Amazon Drainage system.

Remarks. In general, individuals of Austrofundulus rupununi are phenotypically “intermediate” between the most gracile or delicate species of the genus, A. transilis , of the Venezuelan Llanos and the rest of the species previously known as A. limnaeus which attain a larger size and are robust predators. Similarly to A. transilis they have relatively small body size, and do not appear to be very aggressive. As in the A. limnaeus species group this species also has highly developed male coloration, as well as dorsal and ventral extensions on the caudal fin. In general, the over all tone of the body coloration is pastel, rather than the more gaudy color patterns seen in other Austrofundulus species.