Astyanax macal, 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 : 1387-1389

Astyanax macal sp. nov.

( Figures 10 (a), 15, 35)

Astyanax sp. 4 . Ornelas-García et al. 2008.

Astyanax ‘Macal’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in Yucatan, Peten and Belize as follows: predorsal length, 50% SL or shorter (50% or longer in A. altior and A. angustifrons ); least depth, 12% SL or less (12% or more in A. altior ); anal fin origin usually without overlap to last dorsal-fin ray (usually overlapping in A. baileyi ); scaly sheath in anal-fin base, double (vs single); nuptial tubercles in male can be bifid (vs always simple); rostral fontanel, sides convex (vs usually straight).

Description

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

Head profile straight; snout rounded. Lower and upper lips even, or upper lip a bit protruding; mouth somewhat upturned. Pectoral fins, not reaching posteriorly to pelvic fin origin in females (longer in males); anal and dorsal fins do not overlap vertically in females (they do, in males). Lobes of caudal fin, not equal: lower one longer.

D. 10; A. 21–24, mean 22.5; pect. 12. Procurrent unsegmented dorsal rays on caudal fin, 10 or more. Gill rakers on first arch, 17–20, modally 19; on lower limb, 9–11. Scales on lateral line, 34–37, modally 36; predorsal scales, 11–12; scale rows from lateral line to base of first dorsal-fin ray, 7–8.5, modally 8; to base of pelvic fin, 6–7; to base of pectoral fin, modally 4, up to 5; circumpeduncular scales, 14–16, modally 15. A double scale row on anal fin base, about 8 scales long. Nuptial tubercles only on anal fin rays, simple or bifid. Total vertebrae 34, 20 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 67.2 mm SL. Body depth, 32–39% SL. Head length 24–28% SL; orbital diameter, 31–34% HL; interorbital distance, 8.5–10.9% SL, mean 9.3% SL (further morphometric data appear in Table 4).

Anterior fontanel short, convex-sided, blunt-tipped. Supraoccipital process in dorsal view, short, wide-based; caudally undulate 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, straight. Maxillary, with a convex anteroinferior edge; 1–3 teeth. Quadrate, dorsal process not expanded. Metapterygoid, rostral arm longer than ventral, 2 dorsorostral projections. Infraorbital II, a triangle with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, rectangular with a projection; a wide contact between infraorbitals II and III. Urohyal rostral end turned up, pointed, its ventrorostral edge convex, its ventral apex closer to caudal end; no ceratohyal foramen; rostral vertices of urohyal angled, the ventral side straight. Epibranchial III, insertion of uncinate process angled, the distal segment of the main body straight. Upper pharyngeal bones, oval; lower pharyngeal plate not seen. Dorsal side of hyomandibular, convex. Opercular dorsal edge, markedly angled; sides of dorsal half, parallel; posterior edge, dorsally concave, ventrally straight-convex; ventral tip, sharp. Interopercle, posterior edge, straight-convex, with a spine. Preopercle, anterodorsal edge, with a median convexity; ventral rim, straight; posteroventral edge, curved; 2 divergent canals at angle. Five predorsal bony elements, distally expanded; rostral edge of first pterygiophore angled. Coracoid with 2–3 interdigitations in suture to cleithrum, a concave caudal edge, a double posteroinferior spine. Caudad process of postcleithrum, digitiform. Proximal edge of pelvic bone, convex. Dorsal tip of scaphium, truncate; caudal tip, sharp; dorsoposterior edge, slightly concave. Neural spines under dorsal fin, straight. Seventh caudal vertebra from tail, with a haemal spine displaced caudad. Rostral edge of largest hypuric plate, convex. Epuric plate on last neural spine, straight.

Humeral spot vertically oblong, but rather inconspicuous. Pigment on anal fin, denser distally. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Holotype UMMZ 250291 , 67.2 mm SL, ‘ between San Luis and Millonarios, Cayo District’, Macal River , Maya Mountains, highlands of Belize, coll. Lichtfield, 1960 ( Figure 35 ) . Paratypes: UMMZ 178599, 13 specimens, same collection data as holotype.

Etymology

Named after the type locality. A noun in apposition. Probably from the Mayan ‘makal’, meaning ‘yam’.

Distribution

Endemic to the upper Macal River, Maya Mountains, Belize ( Figure 15 ). There is at least one other species endemic to this river: Poecilia teresae Greenfield 1990 . The river is a tributary of the eastern branch of the Belize River, Caribbean drainage.

Proposed common names

Macal tetra, sardinita del Macal.

Remarks

Astyanax macal sp. nov. corresponds to clade V or ‘species 4’ of Ornelas-García et al. (2008).

Figures

Figure 10. (a) An opercle with parallel sides (Astyanax macal sp. nov., UMMZ 178599); (b) sides divergent at mid-length (A. tehuacanensis sp. nov., UMMZ 198853). Scale bars:1 mm.

Figure 15. Map of northern Central America and southern Mexico, showing distribution localities of Astyanax aeneus, A. altior, A. angustifrons, A. bacalarensis sp. nov., A. caballeroi, A. finitimus, A. macal sp. nov. and A. ocotal sp. nov. A larger symbol denotes the type locality (uncertain for A. angustifrons).

Figure 35. Astyanax macal sp. nov., holotype, UMMZ 250291.