Astyanax bransfordii ( Gill 1877 ) Schmitter-Soto, 2017

Schmitter-Soto, Juan J., 2017, A revision of Astyanax (Characiformes: Characidae) in Central and North America, with the description of nine new species, Journal of Natural History (J. Nat. Hist.) 51 (21 - 24), pp. 1331-1424 : 1371-1373

Astyanax bransfordii ( Gill 1877) comb. nov.

( Figures 27 , 28 )

Bramocharax bransfordii Gill in Gill and Bransford 1877: 175.

Bramocharax elongatus Meek 1907: 110 .

Diagnosis

Diagnosed from other Astyanax species in Nicaragua and northern Costa Rica as follows: gill rakers on first arch lower arm, mean 15–16 (11 in A. nasutus , 14 in A. nicaraguensis ); caudal vertebrae, 19 (20 in A. nasutus ); supraoccipital in dorsal view, long, narrow-based (short, wide-based in A. cocibolca , A. nicaraguensis and A. orstedii ); 2 dorsoposteriad projections of metapterygoid (1 in A. nicaraguensis ); dentigerous arm of premaxilla, longer (arms subequal, in A. cocibolca ); maxillary teeth, more than 9 (vs 4 or fewer); lower pharyngeal plate, single (double in A. cocibolca ); infraorbital III, angled (semicircular in A. nicaraguensis ).

Redescription

A species of Astyanax , subgenus Astyanax (i.e. with a complete predorsal series of scales). Head profile straight; snout elongated ( Bramocharax - type); lips even, mouth terminal. Pectoral fins reach pelvic fin origin; anal and dorsal fins overlap. Lobes of caudal fin, subequal. D. 9–11; A. modally 25, up to 28; pect. 16. Procurrent unsegmented dorsal rays on caudal fin, 10 or more. Gill rakers on first arch, 26–27; on lower limb, 15–17. Scales on lateral line, 37–38; predorsal scales, 12; scale rows from lateral line to base of first dorsalfin ray, 8; to base of pelvic fin, 6; to base of pectoral fin, 5; circumpeduncular scales, 16–17. A long scale-row on anal fin base, with imbricated scales. Nuptial tubercles, not seen. Total vertebrae 32–33, 19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 92.0 mm SL. Body slender, 33–36% SL. Head length, 27–32% SL; orbital diameter, 24–30% HL; interorbital distance, ca. 8% SL (further morphometric data are given in Table 4).

Anterior fontanel, long, straight-sided, sharp-tipped. Supraoccipital process in dorsal view long, narrow-based. Vomer, rostrally undulate. Dentigerous arm of premaxilla, much longer and robust; 5 or more teeth. Highest tooth on dentary, fourth; posterior teeth, not abruptly smaller. Dorsal edge of longer articular arm, straight, arm pointed; dorsal articular arm, angled. Maxillary, with an angled anteroinferior edge; 9–13 teeth. Quadrate, dorsal process expanded. Metapterygoid, rostral arm longer than ventral, 2 dorsorostral projections. Infraorbital II, triangular with a double-angled base; infraorbital III, inferoposteriorly angled; infraorbital IV, rectangular, with a projection; contact between infraorbitals II and III, wide. Urohyal, rostral end turned up, blunt; its ventrorostral edge, convex; its ventral apex, closer to caudal end. Ceratohyal foramen, absent; rostral vertices, angled; ventral side, undulate. Epibranchial III not seen. Upper pharyngeal bones, crescent-shaped; lower pharyngeal plate, single; its caudal side, straight. Dorsal side of hyomandibular, convex. Opercle, dorsal edge convex; sides of dorsal half, parallel; posterior edge, dorsally undulate, ventrally straight; ventral tip, sharp. Interopercle, posterior edge, straight-convex, with a spine. Preopercular anterodorsal edge, with a median convexity; ventral rim, straight; posteroventral edge, curved; 2 canals at angle, parallel. Four predorsal bony elements, expanded. Coracoid with a concave caudal edge, a single posteroinferior spine. Caudad process of postcleithrum, squarish. Dorsal tip of scaphium, truncate; caudal tip, spiny; dorsoposterior edge, slightly concave. Postanal element, long. Largest hypuric plate, rostral edge concave; epuric plate on last neural spine, convex-sided.

Humeral spot, oval to indistinct. Pigment on anal fin, sparse. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Lectotype USNM 16885 , Lake Nicaragua, coll. J.F. Bransford, spring of 1876 ( Figure 27 ) . Paralectotypes: USNM 437594 (2 specimens), same collection data.

Distribution

Endemic to Lake Nicaragua and tributaries, Nicaragua and Costa Rica ( Figure 28 ).

Remarks

The species corresponds to clade IIa of Ornelas-García et al. (2008).

This is the type species of genus Bramocharax Gill , the synonymisation of which with Astyanax is supported by both molecular and osteological phylogenies ( Ornelas-García et al. 2008; Schmitter-Soto 2016).

Figures

Figure 27. Astyanax bransfordii, lectotype, USNM 16885. © M.E. Valdez-Moreno. Reproduced by permission of M.E. Valdez-Moreno. Permission to reuse must be obtained from the rightsholder.

Figure 28. Map of lower Central America, showing distribution localities of Astyanax bransfordii, A. cocibolca, A. nasutus, A. nicaraguensis, A. orstedii and A. panamensis. Astyanax bransfordii and A. cocibolca co-occur in Lake Nicaragua. A larger symbol denotes the type locality (uncertain for A. nicaraguensis and A. panamensis).