Astyanax petenensis ( Günther 1864 )

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 : 1403-1405

Astyanax petenensis ( Günther 1864)

( Figures 24 , 43 )

Tetragonopterus petenensis Günther 1864: 326 .

Astyanax mexicanus? Regan 1908 and subsequent authors.

Astyanax ‘Petén’, Schmitter-Soto 2016.

Diagnosis

Diagnosed from other Astyanax species in the region as follows: head profile, usually straight or very slightly concave (usually quite concave, in A. belizianus ; straight-convex, in A. brevimanus ); procurrent unsegmented dorsal rays on caudal fin, 9 or fewer (10 or more, in A. cubilhuitz sp. nov.); caudal vertebrae, 19 or fewer (20, in A. brevimanus ); body slenderer than A. bacalarensis sp. nov., A. belizianus and A. cubilhuitz sp. nov., mean depth 34% SL (vs 38%); interorbital, mean 9% SL (mean 8% SL in A. belizianus ); predorsal length, mean 49% (vs 50% or more); dorsal vertices of ceratohyal, angled (round in A. bacalarensis sp. nov., A. belizianus and A. cubilhuitz sp. nov.); urohyal, rostral end blunt (pointed in A. angustifrons ).

Redescription

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

Head profile, straight to very slightly concave; snout usually squarish, may be somewhat pointed. Lips even, or upper lip slightly protruding; mouth terminal. Pectoral fins usually reach pelvic-fin origin; anal and dorsal fins usually do not overlap. Lobes of caudal fin, subequal.

D. 10–11; A. 23–27, modally 24; pect. 11–13. Procurrent unsegmented dorsal rays on caudal fin, 9 or fewer. Gill rakers on first arch, 19–23, modally 21; on lower limb, 10–14, modally 13. Scales on lateral line, 33–38, modally 35; predorsal scales, 10–13, modally 11; scale rows from lateral line to base of first dorsal-fin ray, 6.5–8, modally 7; to base of pelvic fin, 6; to base of pectoral fin, modally 4, rarely 3 or 5; circumpeduncular scales, 14–17, modally 16. A single, short row of about 10 scales 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, 108.5 mm SL. Body depth, 31–36% SL. Head length, 22–28% SL; orbital diameter, 24–36% HL; interorbital distance, 7.8–10.4% SL, mean 8.9% SL (further morphometric data appear in Table 4).

Anterior fontanel, variable. Supraoccipital process in dorsal view, short, wide-based. 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. Metapterygoid, rostral arm longer than ventral, 2 dorsorostral projections. Infraorbital II, triangular with an angled base; infraorbital III, inferoposteriorly semicircular; infraorbital IV, square to rectangular, with a projection; contact between infraorbitals II and III, wide. Urohyal, rostral end turned up, blunt; its ventrorostral edge convex; ceratohyal foramen oval. Epibranchial III, distal segment of main body straight. Upper pharyngeal bones, crescent-shaped; lower pharyngeal plate single, its caudal side concave. Dorsal side of hyomandibular, convex. Sides of dorsal half of opercle, 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 canals at angle. Four or 5 predorsal bony elements, distally expanded; rostral edge of first pterygiophore angled. Coracoid with 2–3 interdigitations in suture to cleithrum, a concave caudal edge. Caudad process of postcleithrum, globose to digitiform. Proximal edge of pelvic bone, convex. Postanal element, long. Dorsal tip of scaphium, truncate; caudal tip, sharp; dorsoposterior edge, slightly concave to 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, P-shaped or indistinct. Pigment on anal fin, uniformly sparse. Caudal spot, both on peduncle and on fin rays.

Type material and depositor

Lectotype BMNH 1864.1 .26.374, ‘4 inches’ (101.5 mm) TL, Lake Petén Itzá, Guatemala (not ‘ Western Ecuador’ ), coll. O. Salvin, ca. 1861 ( Figure 43 ). Unique, no paralectotypes; the three Ecuadorian syntypes now in BMNH 2016.9 .13.5 are excluded from the series. See Remarks.

Distribution

Lake Petén and environs, Guatemala ( Figure 24 ).

Proposed common names

Petén tetra, sardinita del Petén.

Remarks

The syntypic series, with two type localities, is a composite. It seems clearest to reserve the name A. petenensis for the Guatemalan form, as also proposed by Ornelas-García et al. (2008). The Ecuadorian syntypes are thus excluded from the series.

Lima et al. (2003) considered A. petenensis to be a questionable synonym of A. mexicanus . Miller et al. (2009) considered the latter to be present in Petén, while acknowledging that Contreras-Balderas and Lozano-Vilano (1998) thought otherwise. Astyanax petenensis has the same general body shape as A. mexicanus , but the anal-ray count is one of several conspicuous differences; A. brevimanus is another species in north-eastern Guatemala with a ‘ mexicanus- Gestalt’.

The species is clade Ic of Ornelas-García et al. (2008) and probably clade E of Strecker et al. (2004).

Figures

Figure 24. Map of northern Central America, showing distribution localities of Astyanax baileyi, A. belizianus, A. brevimanus, A. cubilhuitz sp. nov., A. dorioni and A. petenensis. A larger symbol denotes the type locality.

Figure 43. Astyanax petenensis, lectotype, BMNH 1864.1.26.374. © The Natural History Museum, London. Reproduced by permission of The Natural History Museum, London. Permission to reuse must be obtained from the rightsholder.