Astyanax altior Hubbs 1936

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 : 1356-1358

Astyanax altior Hubbs 1936

( Figures 15–17 )

Astyanax fasciatus altior Hubbs 1936: 176 .

Astyanax altior Hubbs ; species rank, Schmitter-Soto 1998.

Diagnosis

Diagnosed from other Astyanax species in the Yucatan as follows: body depth, up to 48% SL (vs never greater than 42%); anal origin overlaps last dorsal-fin ray (usually no overlap in A. angustifrons ); scales between lateral line and dorsal-fin origin, modally 8 (vs modally 7.5 or fewer); anterior fontanel, shorter (longer in A. angustifrons ); rostral vertices of ceratohyal, angled (round in A. bacalarensis sp. nov.); preopercle anterodorsal edge, straight-concave (with a median convexity in A. bacalarensis sp. nov.); coracoid caudal edge, concave, with a double spine (vs spine single).

Redescription

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

Head profile concave or straight-concave; snout round. Lips even; mouth terminal. Pectoral fins usually reach pelvic fin origin; anal and dorsal fins may or may not overlap. Lobes of caudal fin, subequal.

D. 9–10; A. 22–25, mean 24; pect. 10–15. Procurrent unsegmented dorsal rays on caudal fin, 9–10. Gill rakers on first arch, 21–24, mean 22.5; on lower limb, 12–14. Scales on lateral line, 32–36, modally 34; predorsal scales, 10–13, mean 11.5; scale rows from lateral line to base of first dorsal-fin ray, 8, occasionally 8.5; to base of pelvic fin, 5–6; to base of pectoral fin, 4; circumpeduncular scales, 16–18. An imbricated scale row on anal fin base, long. Nuptial tubercles, always simple. Total vertebrae 31–33, 18–19 caudal. Detailed frequencies are given in Table 3.

Largest examined specimen, 57.5 mm SL. Body very deep, 37–48% SL. Head length 27–34% SL; orbital diameter 30–33% HL; interorbital distance, 8.6–10.8% SL (further morphometric data appear in Table 4; see also Schmitter-Soto 1998).

Anterior fontanel short, convex-sided, blunt-tipped. Supraoccipital process in dorsal view, long, narrow-based, angled or slightly concave in lateral view. Vomer rostrally slightly concave. Arms of premaxilla, variable; teeth, 0–4. Highest tooth on dentary, first or third; the 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 dorsocaudad projections. Infraorbital II, triangular with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, rectangular with a projection; contact between infraorbitals II and III, wide. Urohyal rostral end turned up, its ventrorostral edge convex, its ventral apex closer to caudal end; ceratohyal foramen oval (sometimes absent); rostral vertices of ceratohyal angled, the ventral side variable. Epibranchial III, insertion of uncinate process angled, the distal segment of the main body variable. Upper pharyngeal bones, oval; lower pharyngeal plate, single; its caudal side, concave. Dorsal side of hyomandibular, convex. Opercular dorsal-half sides, parallel; opercle caudoventrally straight-convex, caudodorsally concave; ventral tip, sharp. Interopercle, posterior edge, straight-convex. Preopercle, ventral rim, straight; posteroventral edge, curved; 2 canals at angle. Five predorsal bony elements, expanded; rostral edge of first pterygiophore, variable. Coracoid with 4–5 interdigitations in suture to cleithrum, a concave caudal edge, a double posteroinferior spine. Caudad process of postcleithrum, trapezoidal to globose. Proximal edge of pelvic bone, convex. Postanal element, short. Dorsal tip of scaphium, truncate; caudal tip, spiny; 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, straight. Epuric plate on last neural spine, edge straight.

Humeral spot, an elongated lozenge. Pigment on anal fin sparse, rather distally concentrated. Caudal spot both on peduncle and on fin rays ( Figure 16 ).

Type material and depositor

Holotype UMMZ 102144 , 53.0 mm SL, ‘roadside pool 3 km south of Progreso’ , northwestern Yucatan, Mexico, coll. C.L. Hubbs, 1932 . Paratypes: UMMZ 102145 ( Figure 17 ), 3 specimens (2 of them juveniles), same collection data as holotype.

Distribution

North-western Yucatan Peninsula ( Figure 15 ). No records in its eastern coast, contra Schmitter-Soto (1998), nor in central Campeche, contra Torres-Castro et al. (2009); see below.

Remarks

Based solely on meristics and morphometrics, Schmitter-Soto (1998) diagnosed A. altior from ‘ A. aeneus ’ (= a mixture of A. angustifrons and A. bacalarensis sp. nov.), wrongly including in A. altior populations from central Quintana Roo. The present osteological diagnosis brings the taxon back to Hubbs’ (1936) concept; the Quintana Roo populations belong to a different deep-bodied species, A. bacalarensis sp. nov. As for the records in Campeche, they correspond to A. angustifrons .

The species is part of clade Ib of Ornelas-García et al. (2008) and corresponds to clade B of Strecker et al. (2004). Hausdorf et al. (2011) found a nuclear-gene group exclusive to A. altior . The species has been listed as Vulnerable ( Jelks et al. 2008).

Figures

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 16. Astyanax altior live at Cenote Xlaká in Dzibilchaltún, Yucatan. © M. Salazar González. Reproduced by permission of M. Salazar González. Permission to reuse must be obtained from the rightsholder.

Figure 17. Astyanax altior, paratype, UMMZ 102145.