Astyanax rioverde Lozano-Vilano and 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 : 1405-1407

Astyanax rioverde Lozano-Vilano and Schmitter-Soto sp. nov.

( Figures 5 (a), 6(b), 8(b), 12, 44)

Astyanax mexicanus [part. et non] de Filippi 1853. Meek 1904: 84.

Astyanax ‘Rioverde’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in central-northern Mexico as follows: circumpeduncular scales, modally 16.5 (vs fewer); body deeper, mean 37% SL (mean 34% SL in A. argentatus ); interorbital, mean 9–10% SL (mean 8% SL in A. tehuacanensis sp. nov.); maxillary 10.2% SL or shorter, mean 9.5% (10.1% SL or longer, mean 11.1% in A. argentatus ); anal-fin base, 24% SL or shorter (23% SL or longer in A. argentatus ); anterior fontanel, short (longer in A. mexicanus and A. tehuacanensis sp. nov.), convexsided (straight-sided in A. acatlanensis sp. nov., A. mexicanus and A. tehuacanensis sp. nov.), sharp-tipped (blunt in A acatlanensis sp. nov. and A. mexicanus ); infraorbital II, triangular with an angled base (base convex in A. acatlanensis sp. nov., A. argentatus and A. mexicanus ); first dorsal pterygiophore, rostral edge, angled (curved in A. argentatus and A. mexicanus ); humeral spot, oval (vs triangular-rectangular).

Description

A species of Astyanax , subgenus Astyanax (i.e. with a complete predorsal series of scales).

Head profile straight to convex at nape; snout rounded. Lower and upper lips, even; mouth terminal, not upturned. Pectoral fins, usually not reaching posteriorly to pelvic fin origin, often falling very short; anal and dorsal fins do not overlap vertically. Lobes of caudal fin, subequal.

D. 9; A. modally 18, up to 20; pect. 11. Procurrent unsegmented dorsal rays on caudal fin, 9 or fewer. Gill rakers on first arch, 16–19, modally 18; on lower limb, 10–11. Scales in lateral line, 31–35, modally 33; predorsal scales, 9–13, mean 11.5; scale rows from lateral line to base of first dorsal-fin ray, 7; to base of pelvic fin, 6; to base of pectoral fin, 3.5–4; circumpeduncular scales, 16–17. A short, single scale row on anal fin base. Nuptial tubercles only on pelvic-fin rays, simple. Total vertebrae, 32–33; 18–19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 74.8 mm SL. Body deep, 34–40 % SL, mean 36.6%. Head rather short, 22–26% SL; orbital diameter 30–35% HL; interorbital distance, 8.6–9.9% SL, mean 9.1% SL (further morphometric data appear in Table 4).

Anterior fontanel short, convex-sided, sharp-tipped. Supraoccipital process in dorsal view, short, wide-based, caudally slightly concave in lateral view. Vomer rostrally slightly concave. Dentigerous arm of premaxilla, longer; 4–5 teeth. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Dorsal edge of longer articular arm, straight. Maxillary, with a convex anteroinferior edge; 1–3 teeth. Quadrate, dorsal process expanded. Metapterygoid, rostral arm longer than ventral; only 1 dorsorostral projection. Infraorbital II, a triangle with an angled base; infraorbital III, inferoposteriorly angled; infraorbital IV, rectangular with a projection; a wide contact between infraorbitals II and III. Urohyal rostral end turned up, blunt, its ventrorostral edge convex, its ventral apex closer to caudal end; ceratohyal foramen, oval; its rostral vertices angled, its ventral side undulate. Epibranchial III, insertion of uncinate process round, the distal segment of the main body curved. Upper pharyngeal bones, S-shaped; lower pharyngeal teeth plate, single, its caudal side concave. Dorsal side of hyomandibular, convex. Opercular dorsal edge, obtuse; sides of dorsal half, parallel; posterior edge, dorsally concave, ventrally straight-convex. Interopercle, posterior edge, straight-convex, with a spine. Preopercular anterodorsal edge, straight-concave; ventral rim, convex; posteroventral edge, curved; 2 canals at angle. Five predorsal bony elements, distally expanded; rostral edge of first pterygiophore angled. Coracoid with 6 interdigitations in suture to cleithrum, a concave caudal edge, a double posteroinferior spine. Caudad process of postcleithrum, digitiform. Proximal edge of pelvic bone, convex. Caudal tip of scaphium, sharp, its dorsoposterior edge slightly concave. Neural spines under dorsal fin, straight. Postanal element, short. Sixth or seventh caudal vertebra from tail, with a haemal spine displaced caudad. Rostral edge of largest hypuric plate, straight. Epuric plate, variable.

Humeral spot oval, short. Pigment on anal fin sparse, distal. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Holotype UMMZ 250293 , 74.8 mm SL, ditch 4.8 mi [7.7 km] south of Rioverde , San Luis Potosí, Mexico, coll. Barbour and Douglass, 1959 ( Figure 44 ) . Paratypes: UANL 1030 , 300 specimens, stream 7.7 km SSE of Rioverde , coll . S . Contreras-Balderas, July 1968, UANL 1326 , 7 specimens, stream 1 km E of Rioverde , same collector and date . UMMZ 192510 , 305 specimens, same collection data as holotype . UMMZ 172194 , 29 specimens, 40 mi (64.4 km) west of Rioverde , same collectors and date . UMMZ 193447 , 34 specimens, río Santa María , 10 mi (16.1 km) south-east of Rioverde, same collectors and date .

Etymology

Named after the type locality. A noun in apposition.

Distribution

Ditches and other tributaries (including Río Santa María) to Río Verde, Río Pánuco drainage (Atlantic), near the city of Rioverde, San Luis Potosí State, Mexico ( Figure 12 ).

Proposed common names

Rioverde tetra, sardinita de Rioverde.

Remarks

The species corresponds to clade Ia of Ornelas-García et al. (2008), in part, and to clade A2 of Strecker et al. (2004).

The authorship of this species is joint with M.L. Lozano-Vilano, who independently collected and recognised it as distinct.

Figures

Figure 5. (a) An infraorbital II with an angled base (Astyanax rioverde sp. nov., UMMZ 192510); (b) base convex (A. aeneus, UMMZ 178568). Scale bars: 0.5 mm.

Figure 12. Map of Mexico, showing distribution localities of Astyanax acatlanensis sp. nov., A. argentatus, A. mexicanus, A. rioverde sp. nov., A. salvatoris sp. nov., A. tamiahua sp. nov. and A. tehuacanensis sp. nov. A larger symbol denotes the type locality (ambiguous for A. mexicanus; see text).

Figure 44. Astyanax rioverde sp. nov., holotype, UMMZ 250293.