Leiognathus Lacepède, 1802

Chakrabarty, Prosanta & Sparks, John S., 2008, Diagnoses for Leiognathus Lacepède 1802, Equula Cuvier 1815, Equulites Fowler 1904, Eubleekeria Fowler 1904, and a New Ponyfish Genus (Teleostei: Leiognathidae), American Museum Novitates 3623 (1), pp. 1-12 : 3-5

Leiognathus Lacepède, 1802

Figure 2

TYPE SPECIES: Leiognathus equulus ( Forsskål, 1775) .

OTHER INCLUDED SPECIES: Leiognathus robustus Sparks and Dunlap, 2004 , L. striatus, James and Badrudeen, 1990 .

DIAGNOSIS: Members of Leiognathus are distinguished from all other leiognathids by a combination of large adult body size (. 150 mm SL), the absence of large round blotches of pigment on the flank, and the presence of a strongly ventrally protracting mouth.

REMARKS: Members of Leiognathus can be further distinguished from all other ponyfishes, except Equula , by the presence of a nonsexually dimorphic light organ. The absence of flank pigmentation or the possession of faint yellowish or grayish-yellow vermiculate lines or vertical bars on the dorsal flank also distinguishes members of Leiognathus from all other ponyfishes, except Equula . Members of Leiognathus can be further distinguished from members of Equula by the presence of a strongly concave lower jaw profile (versus straight or nearly straight in Equula ). All explicit phylogenetic studies of Leiognathidae to date have recovered a paraphyletic Leiognathus ( Ikejima et al., 2004; Sparks and Dunlap, 2004; Sparks et al., 2005; Chakrabarty et al., MS). In accordance with the results of these studies, we restrict the name Leiognathus to the clade containing the type species, Leiognathus equulus ( Forsskål, 1775) (see Sparks and Dunlap, 2004), and two other described species, Leiognathus robustus Sparks and Dunlap, 2004 , and Leiognathus striatus James and Badrudeen, 1990 , a species rarely mentioned in the literature and even more rarely encountered in museum collections. This restricted concept of Leiognathus is recovered as the sister group to all other members of Leiognathidae , less Equula (fig. 1). Other ponyfish species in the literature currently referred to Leiognathus , but not included in our restricted concept of this genus, are provided novel or resurrected generic assignments below on the basis of apomorphic morphological features. The lineage labeled ‘‘‘ L. ’ sp. Sri Lanka’’ in figure 1 is recovered as a member of Leiognathus in Chakrabarty et al. (MS). The taxonomy of this group is further dealt with in that manuscript rather than here, because the species-level status of ‘‘ L. ’’ sp. Sri Lanka cannot be determined due to a lack of morphological vouchers (only a tissue sample was available to Sparks et al., 2005).

Leiognathus striatus can be distinguished from its congeners by the presence of an extremely deep body with a strongly convex dorsal profile (owing to the presence of a pronounced occipital hump) and a pigmentation pattern on the dorsal flank comprising broad yellow vertical bars. Leiognathus robustus can be distinguished from its congeners by the absence of a pronounced occipital hump and the presence of a mildly sloping predorsal profile (see Sparks and Dunlap, 2004). Leiognathus equulus is distinguished from congeners by the combination of a strongly sloping predorsal profile with a pronounced occipital hump and the absence of yellow vertical bars on the flank.