Astyanax petenensis ( Günther 1864 )

Astyanax petenensis ( Günther 1864) View in CoL

( Figures 24 View Figure 24 , 43 View Figure 43 )

Tetragonopterus petenensis Günther 1864: 326 View in CoL .

Astyanax mexicanus? Regan 1908 View in CoL and subsequent authors.

Astyanax View in CoL ‘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 View 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 View 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).