Astyanax tehuacanensis, 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 : 1411-1413

Astyanax tehuacanensis sp. nov.

( Figures 2 (b), 10(b), 12, 47)

Tetragonopterus mexicanus non de Filippi, Meek 1904.

Astyanax ‘Tehuacán’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in central Mexico as follows: anal-fin rays, mean fewer than 24 (mean 24 or more in A. aeneus ); total gill rakers, mean fewer than 20 (mean 22 or more in A. fi nitimus); head shorter, mean 21.9% SL (vs mean 23.8% or more); snout shorter, mean 3.3% SL (vs mean 4.2% or more); interorbital, mean 8% SL (mean 9–10% SL in A. acatlanensis sp. nov. and A. mexicanus ); pectoral fin shorter, mean 19.3% SL (mean ca. 21% in A. acatlanensis sp. nov. and A. mexicanus ); anterior fontanel, longer (vs shorter); infraorbital II, triangular with an angled base (base convex in A. acatlanensis sp. nov., A. aeneus and A. mexicanus ); epibranchial III, distal segment straight (curved in A. fi nitimus and A. mexicanus ); first dorsal pterygiophore, dorsal edge angled (curved in A. mexicanus ).

Description

A species of Astyanax , subgenus Astyanax (i.e. with a complete predorsal series of scales). Head profile, straight-convex at nape; snout round. Lips even (sometimes upper lip a bit salient); mouth terminal. Pectoral fins, usually far from reaching posteriorly to pelvic fin origin; anal and dorsal fins do not overlap vertically. Lobes of caudal fin, subequal.

D. 9; A. 18–23, mean 20.5; pect. 13–14. Procurrent unsegmented dorsal rays on caudal fin, variable. Gill rakers on first arch, 18–19; on lower limb, modally 11, occasionally 12. Scales in lateral line, 32–36, modally 35; predorsal scales, 11–13, modally 12; scale rows from lateral line to base of first dorsal-fin ray, 7–8.5; to base of pelvic fin, 6; to base of pectoral fin, 4, rarely 3.5; circumpeduncular scales, 15–17, mean 16. A short, single scale row on anal fin base. Nuptial tubercles, not seen. Total vertebrae 32–33, 18–19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 74.5 mm SL. Body depth, 34–38% SL. Head short, 20–24% SL; orbital diameter 31–36% HL; interorbital distance, 7.4–9.1% SL, mean 8.2 (further morphometric data appear in Table 4).

Anterior fontanel long, straight-sided, sharp-tipped. Supraoccipital process in dorsal view, long, narrow-based; slightly concave in lateral view. Vomer rostrally slightly concave. Dentigerous arm of premaxilla, longer; 0–4 teeth. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Dorsal edge of longer articular arm, undulate. 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, square with a projection. Urohyal rostral end turned up, blunt, its ventrorostral edge spiny, its ventral apex closer to caudal end; ceratohyal foramen oval, its rostral vertices angled, its ventral side undulate. Epibranchial III, insertion of uncinate process angled, the distal segment of the main body straight. Upper pharyngeal bones, S-shaped; lower pharyngeal plates not seen. Dorsal side of hyomandibular, convex. Opercular dorsal edge, convex; sides of dorsal half, divergent; caudoventrally straight-convex, caudodorsally concave; ventral tip, sharp. Interopercular posterior edge straight-convex, with a spine. Preopercle, anterodorsally straight-concave; ventral rim, straight; posteroventral edge, curved; 2 canals at angle, parallel. Five predorsal bony elements, irregularly expanded; rostral edge of first pterygiophore angled. Coracoid with 2 interdigitations in suture to cleithrum, a concave caudal edge, a single posteroinferior spine. Proximal edge of pelvic bone, convex. Postanal element, short. Caudal tip of scaphium, truncate, its dorsoposterior edge sharp. Neural spines under dorsal fin, straight. Sixth caudal vertebra from tail, with a haemal spine displaced caudad. Rostral edge of largest hypuric plate, straight. Epuric plate on last neural spine, straight-edged.

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

Type material and depositor

Holotype UMMZ 250295 , 74.5 mm SL, Río Salado (or Zapotitlán), 22 mi (35.4 km) south of Tehuacán , Papaloapan basin, Puebla, central Mexico, coll. R. R. Miller and party, March 1976 ( Figure 47 ) . Paratypes: UMMZ 198853 (57 specimens), same collection data as holotype.

Etymology

Named after the type locality. An adjective.

Distribution

Endemic to the Río Salado (Gulf of Mexico versant), south of Tehuacán, Puebla, central Mexico ( Figure 12 ).

Proposed common names

Tehuacán tetra, sardinita de Tehuacán.

Figures

Figure 2. (a) A urohyal with ventral apex about equidistant between rostral and caudal tips (Astyanax mexicanus, UMMZ 169835); (b) closer to caudal end (A. tehuacanensis sp. nov., UMMZ 198853).

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 47. Astyanax tehuacanensis sp. nov., holotype, UMMZ 250295.