Astyanax tamiahua, 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 : 1409-1411

Astyanax tamiahua sp. nov.

( Figures 12 , 46 )

Astyanax ‘Tamiahua’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in Veracruz and northern Mexico as follows: body deeper, mean 35.9% SL (mean 33.9% SL in A. argentatus ); head longer, more than 26% SL (26% or less in A. acatlanensis sp. nov., A. argentatus and A. rioverde sp. nov.); supraoccipital in lateral view, slightly concave (angled in A. fi nitimus); infraorbital II, triangular with an angled base (with a long convex base in A. argentatus and A. mexicanus ); first dorsal pterygiophore, rostral edge angled (curved in A. argentatus and A. mexicanus ).

Description

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

Head profile approximately straight at nape; snout rounded; lower and upper lips even, mouth terminal. Pectoral fins usually reach posteriorly to pelvic fin origin; anal and dorsal fins may overlap vertically. Lobes of caudal fin, subequal.

D. 10–11; A. 20–25, modally 22; pect. 10–11. Procurrent rays on dorsal caudal fin, 9 or fewer. Gill rakers on first arch, 17–20, modally 19; on lower limb, 11–12. Scales in lateral line, 30–34, modally 32; predorsal scales, 9–12, modally 10; scale rows from lateral line to base of first dorsal-fin ray, 7; to base of pelvic fin, 5; to base of pectoral fin, modally 4, as few as 3; circumpeduncular scales, 15–18, modally 16. A short, single scale row on anal fin base. Nuptial tubercles may be bifid. Total vertebrae 31–33, 18–19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 62.7 mm SL. Body depth, 33–38% SL. Head length, 26–28% SL; orbital diameter, 30–37% HL; interorbital distance, 8.2–11.1% SL, mean 9.3 (further morphometric data appear in Table 4).

Anterior fontanel short, convex-sided. Supraoccipital process in dorsal view, long, narrow-based, slightly concave in lateral view. Vomer rostrally slightly concave. Arms of premaxilla, subequal; 0–4 teeth. Highest tooth on dentary, first or third; posterior teeth, abruptly smaller. Articular, dorsal arm, angled. Maxillary teeth, 1–3. Quadrate, dorsal process not expanded. Metapterygoid, rostral arm longer than ventral. Infraorbital II, a triangle with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, square. Urohyal rostral end turned up, its ventrorostral edge convex, its ventral apex about equidistant between rostral and caudal end; ceratohyal rostral vertices angled. Epibranchial III, distal segment of the main body, straight. Lower pharyngeal teeth plate, single; its caudal side concave. Dorsal side of hyomandibular, convex. Opercle, sides of dorsal half, parallel; caudoventrally straight-convex, caudodorsally concave; ventral tip, sharp. Interopercular posterior edge, straight-convex, with a spine. Preopercular ventral rim, straight; posteroventral edge, curved; 2 canals at angle. Five predorsal bony elements; rostral edge of first pterygiophore angled. Coracoid with 2 interdigitations in suture to cleithrum, a concave caudal edge. Caudad process of postcleithrum, with parallel sides and convex end. Proximal edge of pelvic bone, convex. Postanal element, short. Caudal tip of scaphium, spiny; its dorsoposterior edge, slightly concave. Neural spines under dorsal fin, straight. Sixth caudal vertebra from tail, with a haemal spine displaced caudad. Rostral edge of largest hypuric plate, concave. Epuric plate on last neural spine, convex-edged.

Humeral spot, squarish. Pigment on anal fin, concentrated distally. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Holotype UMMZ 250294 , 54.2 mm SL, Río Cucharas near Tamiahua, northern Veracruz, Mexico, coll. April 1930 ( Figure 46 ) . Paratypes: UMMZ 97362 (103 specimens), same collection data as holotype . UMMZ 167489 (100 specimens), Río Nautla at Ixtacocoa, Veracruz, Mexico, coll . September 1951.

Etymology

Named after the type locality. A noun in apposition.

Distribution

Tamiahua to Nautla, northern Veracruz, Mexico ( Figure 12 ).

Proposed common names

Tamiahua tetra, sardinita de Tamiahua.

Remarks

The southern population at Nautla may reach 25 anal-fin rays and 34 scales on lateral line, whereas the type population near Tamiahua does not exceed 23 and 33, respectively; pectoral fins are also longer in the northern range.

The species, represented by both populations, is a part of clade Ia of Ornelas-García et al. (2008), in a subgroup different from from that of the inland northern forms.

Figures

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 46. Astyanax tamiahua sp. nov., holotype, UMMZ 250294.