Cephalocassis Bleeker, 1852

(Figs 1–3, 24B, 28)

Type species: Arius melanochir Bleeker, 1852 .

Diagnosis

Posterior branches of mesethmoid narrow (6, 0> 1); posterior branches of mesethmoid parallel throughout their entire extension (7, 0> 1); anterior portion of anterior cranial fontanel not delimitedbydorsalexpansionoforbitosphenoid (24, 1> 0); fenestra delimited by parieto-supraoccipital, pterotic and sphenotic present (34, 0> 1); parieto-supraoccipital process base almost as narrow as posterior portion (46, 1> 0); vomer anterior margin very pronounced and acute (50, 0> 1); tooth plates associated with vomer absent (55, 1> 0); lateral expansions of orbitosphenoid and pterosphenoid absent (64, 1> 0); optic foramen very reduced (67, 1> 2); basioccipital lateral process absent (82, 1> 0); space between transcapular process and otic capsule very small (89, 1> 2); teeth on dentary restricted to mesial two-thirds (116, 1> 0); premaxilla narrow and very long, its length two to three times in width (120, 1> 2); interopercle anterior portion conspicuously narrow (133, 0> 1); metapterygoid one and one-half times longer than deep in perpendicular section (135, 1> 2); ventral crest of hyomandibula absent (142, 0> 1); second external branchiostegal ray almost as wide as first ray (148, 0> 1); second basibranchial spindle shaped (166, 1> 0); first hypobranchial very elongate transversely, with well-developed and acute mesial face (172, 0> 1); anterior process of first hypobranchial very conspicuous (173, 0> 1); second hypobranchial very elongate transversely, its mesial face acute (176, 0> 1); posterior margin of fourth epibranchial slightly convex, one-fourth as wide as long (187, 0> 1); accessory crest connecting transverse and median crests associated with neural spine of fourth vertebra present (204, 0> 1).

Ambiguous optimization: Posterior cranial fontanel very wide and long (27, 2> 3).

Included species

Cephalocassis melanochir Bleeker, 1852 .

Habitat and distribution: Freshwater, Southeast Asia (Fig. 24).

Remarks

Hemipimelodus had been treated as a junior synonym of Cephalocassis in recent morphological studies (Marceniuk and Menezes 2007, Marceniuk et al. 2012), a condition supported by an extensive list of shared synapomorphies (2, 15, 50, 85, 116, 120, 135, 142, 166, 204, 148, 200, and 222) including an autapomorphy (presence of a fenestra delimited by the supraoccipital, pterotic, and sphenotic). The total-evidence analysis, however, corroborates results of a previous molecular analysis (Betancur-R. 2009), which supports the recognition of Cephalocassis and Hemipimelodus as valid genera, indicating a strong morphological convergence of lineages restricted to freshwater. The inclusion of Cephalocassis in the subtribe Ariina is supported by the MP and ML analyses.