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[[ Genus Acanthopagrus Peters ZBK ]]
Acanthopagrus ZBK , now widely recognized as a valid Indo-West Pacific genus (Weber & de Beaufort, 1936; Akazaki, 1962; Smith & Smith, 1986; Carpenter, 2001), was first proposed as a subgenus of Chrysophrys ZBK by Peters (1855). The type-species of the genus is Chrysophrys vagus Peters ZBK (1852) which was later synonymized with A. berda by Smith & Smith (1986). There are eight currently recognized species of Acanthopagrus ZBK (Eschmeyer, 1998, 2005), of which A. berda is the most widespread (Fowler, 1933; Akazaki, 1962; Carpenter, 2001). Acanthopagrus berda ( Forsskal , 1775) , known as the “Picnic Seabream ”, is characterized by a generally silvery gray color on head, body and fins, 3 ½ scale rows between middle of spinous dorsal fin and lateral line, a fairly deep body, soft-rayed part of anal fin rounded posteriorly, and absence of single enlarged molar posteriorly in jaws as observed in the genus Rhabdosargus (Smith & Smith, 1986, see fig. 183.37 of p. 593; see fig. 8 of Carpenter, 2001). The holotype (ZMUC-P 50555, left dried skin, ca. 213 mm SL, type locality Red Sea) of Acanthopagrus berda has a strong concavity on the ventral edge of the first two infraorbitals above the posterior part of upper jaw (Fig. 1B, Fig. 2A and 2D). This character is a unique feature of this species of Acanthopagrus ZBK . After examination of numerous specimens of A. berda from many localities throughout the Indo-Pacific, we discovered three specimens labeled as A. berda from Taiwan that differed from this species by a number of characters. These specimens did not have a strong concavity on the ventral edge of the first two infraorbitals above the posterior part of upper jaw, even in the largest individual. In addition, they differed from A. berda in the following characters: cheek scale rows 3 or 4, thin upper and lower lips, prominent ridge on dorsal profile in front of eye in older individuals, head and body black with a strongly contrasting whitish belly and chin in older individuals, a dark spot at upper base of pectoral fins, and molar teeth more flattened.
The authors rechecked all known nominal species in the genus Acanthopagrus ZBK and determined that the six specimens from Taiwan represent an undescribed species. The authors herein describe A. taiwanensisn. sp. on the basis of these specimens. Nominal species synonymized with A. berda are discussed and observations are provided for other congeners.