Austrolebias prognathus, Wilson J. E. M. Costa, 2006

Wilson J. E. M. Costa, 2006, The South American annual killifish genus Austrolebias (Teleostei: Cyprinodontiformes: Rivulidae): phylogenetic relationships, descriptive morphology and taxonomic revision., Zootaxa 1213, pp. 1-162: 52-54

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Austrolebias prognathus

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Austrolebias prognathus  (Amato), new combination

(Fig. 21)

Cynolebias prognathus  ZBK  Amato, 1986: 7 ( type locality: Maravillas floodplains, 13 km from the Ruta 9, La Coronilla , Rocha, Uruguay; holotype: MUNHINA 2609  ).

Material examined

Uruguay: Rocha: CIMC 3501, 1; Maravillas floodplains at Ruta 14, 13 km from the Ruta 9, La Coronilla ; M. Cheffe, 7 Aug. 2000.  UFRJ 6187, 2; UFRJ 6188, 3 (c&s); CTL 1813, 3; San Luis, Ruta 19, km 29.5 ; H.-J. Ephan, T. Litz, J. J. Reichert & H. Salvia, 24 Aug. 1994.  CTL 1811, 4; San Miguel ; H. Salvia, 1993.  CTL 1817, 4; Los Naranjales, rio Cebollati ; H. Salvia, 1994.  CTL 1391, 1; temporary swamp near canal Andreoni, Ruta 14, km 504 , 33°55.21’S 53°32.61’W; P. Laurino, T. Litz, E. Perujo, H. Salvia & J. Salvia, 27 Aug. 2004.GoogleMaps  Maldonado: UFRJ 6189, 1 (c&s); CTL 1812, 3; CTL 1392, 6; Salamanca , 34°6.32’S 54°36.05’W; P. Laurino, T. Litz, E. Perujo, H. Salvia & J. Salvia, 28 Aug. 2004.GoogleMaps  Brazil: Rio Grande do Sul: CIMC 8562, 3; arrroio Chui floodplains ; M. Volcan et al., 30 Aug. 2004.  CIMC 8593, 1; idem ; same collectors, 25 Sep. 2004. 


Similar to A. elongatus  and A. monstrosus  , and distinguished from all other species of the A. elongatus  group and most other cynolebiatines in possessing some transverse series of small scales on anal-fin base in males, contact organs on outer surface of each pectoral fin and on caudal fin in males, long jaws (lower jaw 29.3-36.4 % head length in males), and numerous gill-rakers on the first branchial arch (5-6 + 14-16). Distinguished from A. elongatus  and A. monstrosus  by the absence of minute scales on the pectoral-fin and caudal-fin bases in older males, and absence of ventral process on posttemporal.


Morphometric data appear in Table 3. Females larger than males, the largest female examined 102.4 mm SL, largest male 89.2 mm SL. Dorsal profile of head straight to slightly concave, gently convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle; no distinctive adipose ridge on frontal region. Ventral profile slightly convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Greatest body depth at level of pelvic-fin base. Body moderately slender and slightly compressed. Snout pointed and jaws elongated.

Tip of both dorsal and anal fins rounded. Anteromedian rays of anal fin of females not extended; distal portion of anal fin thickened in females. Caudal fin rounded. Pectoral fins elliptical, posterior margin on vertical between base of 2nd and 3rd anal-fin rays in males, between pelvic-fin base and anus in females. Tip of each pelvic fin reaching between base of 2nd and 4th anal-fin rays in males, reaching urogenital papilla in females. Pelvic-fin bases medially united, sometimes medial membrane coalesced in about 50 % of its length. Urogenital papilla not attached to anal fin. Dorsal-fin origin on vertical between base of 6th and 9th anal-fin rays in males, between base of 3rd and 7th anal-fin rays in females; dorsal-fin origin between neural spines of 15th and 17th vertebrae; anal-fin origin between pleural ribs of 14th and 15th vertebrae. Dorsal-fin rays 17-20 in males, 17-19 in females; anal-fin rays 23-25 in both sexes; caudal-fin rays 31-33; pectoral-fin rays 13-14; pelvicfin rays 6.

Scales very small, cycloid, and irregularly arranged. Entire trunk scaled, except just above anal-fin base in females. Head scaled, except anterior half of frontal region and ventral surface. Eight transverse rows of scales on caudal-fin base; eight rows of minute scales on basal third of anal-fin in male; no scales on dorsal fin. Frontal scales small and restricted to posterior frontal portion, without clear arrangement pattern; E-scales not overlapping medially. Longitudinal series of scales about 50-55; transverse series of scales about 20; scale rows around caudal peduncle about 45. One prominent contact organ on each scale of flank and opercle in males. Row of contact organs on inner surface of each pectoral-fin ray, and on outer surface of upper pectoral-fin rays, lateral surface of all anal-fin rays, distal lateral surface of dorsal-fin rays, and distal lateral surface of caudal-fin rays in males.

Cephalic neuromasts: supraorbital 29-31, parietal 4-5, anterior rostral 4-5, posterior rostral 3-4, infraorbital 3 + 33-38, preorbital 2-4, otic plus post-otic 16-19, supratemporal 2-3, median opercular 1, ventral opercular 1-2, preopercular 31-37, mandibular 25-33, lateral mandibular 10-13.

Basihyal subtriangular, width about 90 % of length; basihyal cartilage short, about 35 % of total basihyal length, without lateral projections. Six branchiostegal rays. Three or four teeth on second pharyngobranchial. Gill-rakers on first branchial arch 5-6 + 14-15. Dermosphenotic ossification absent. Ventral process of posttemporal absent. Total vertebrae 35-37.


Males: sides of body dark yellowish gray to dark brown, with small pale golden spots. Urogenital papilla gray. Opercular and infraorbital regions pale green; approximately rectangular, elongate black infraorbital bar; faint gray supraorbital spot. Iris red, with dark brown bar through center of eye. Unpaired fins dark gray, with gray dots. Pelvic fins dark gray. Pectoral fins hyaline.

Female: sides of body gray, with vermiculate pale golden marks; no dark spot on anterocentral portion of flank and caudal peduncle. Opercular region pale golden. Iris red, with dark brown bar through center of eye. Dark gray infraorbital bar and faint gray supraorbital spot. Unpaired fins hyaline with dark gray vermiculate marks; paired fins hyaline.


Southern tributary drainages to lagoa Mirim and adjacent coastal basins, southern Brazil and eastern Uruguay (Fig. 18).


According to Amato (1986), the original description of M. prognathus  was based only on males. However, as already noted by Reichert (1994), the illustrated holotype (Amato, 1986: fig. 8) is a female. The description also indicates that contact organs were absent in all specimens of the type series, suggesting that it comprises only females. This may be confirmed through examination of the type series, which was not available during the present study.