Tosarhombus Amaoka, 1969

Amaoka, Kunio & Ho, Hsuan-Ching, 2019, The lefteye flounder family Bothidae (Order Pleuronectiformes) of Taiwan, Zootaxa 4702 (1), pp. 155-215 : 210

Genus Tosarhombus Amaoka, 1969

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Tosarhombus Amaoka, 1969:64 . Type species: Tosarhombus octoculatus Amaoka, 1969 .

Diagnostic features. Body ovoid. Tip of isthmus below posterior margin of lower eye. Dorsal profile of head steeper in males than in females and juveniles. Both eyes separated by extremely wide concavity; interorbital width larger in males than in females or juveniles. Rostral, orbital and mandibular spines well developed in males.

Mouth large; maxilla extending to or slightly beyond anterior margin of lower eye. Teeth on upper jaw uniserial (rarely biserial); teeth on lower jaw uniserial, nearly same size on both sides. Gill rakers moderately long, usually not serrated, absent in upper limb.

Scales generally not deciduous, ctenoid on ocular side with one row of long ctenii along posterior margin; scales cycloid on blind side. Lateral line on ocular side curved above pectoral fin; lateral line absent on blind side. Pectoral fin rays on ocular side filamentous in males. Pelvic fin on ocular side starting at tip of isthmus, and on a vertical through posterior margin of lower eye; first ray on blind side opposite to third fin ray on ocular side. Vent on blind side, just before origin of anal fin, and urogenital pore on ocular side, opposite side of vent. Caudal skeleton with four plates including parhypural and three hypurals, without deep clefts on distal margins.

Remarks. Tosarhombus closely resembles Parabothus in having ctenoid scales with long spines on the ocular side, caudal plates lacking cleft, and sexual dimorphism in interorbital width. It differs from Parabothus in having a much wider interorbital space in males, a rostral spine present in males, a deeper body and a row of yellowish white blotches on the anterior margin of the head. It also resembles Crossorhombus in the deep body, the broad interorbital space in males, and ctenoid scales with long spines on the ocular side. It differs from Crossorhombus in the tip of the isthmus below the posterior margin of the lower eye, no blotch on the blind side of the body in both sexes and the first pelvic fin ray on the blind side opposite to the third ray on the ocular side.