MORPHOLOGY, SYSTEMATICS, AND BIOLOGY OF THE SPANISH MACKERELS (SCOMBEROMORUS , SCOMBRIDAE) Bruce B. Collette 1 and Joseph L. Russo 2 ABSTRACT The Spanish mackerels and seerfishes of the genus Scorn beromorus constitute the most speciose group of the 44 genera in six families that comprise the suborder Scombroidei. As in higher scom-brids, Scomberomorus , Acanthocybium , and Grammatorcynus have a well-developed median keel on the caudal peduncle, but there is no bony support as is present in the Sardini and Thunnini. Acanthocybium and Scomberomorus share 17 osteological characters and are considered sister-groups. The relationships of Grammatorcynus are not clear but it is clearly more primitive than Scomberomorus; therefore, we have used it as the outgroup for a cladistic analysis of Scomberomorus. Scomberomorus differ from all other scombrids in having a spatulate anterior extension of the vomer. There are 18 species in the genus, nearly 40% of the 49 species of scombrids: Eastern At-lantic — tritor (Cuvier); western Atlantic — brasiliensis Collette, Russo and Zavala-Camin, cavalla (Cuvier), maculatus (Mitchill), and regalis (Bloch); eastern Pacific — concolor Lockington and sierra Jordan and Starks; and Indo-West Pacific — commerson (Lacepede), guttatus (Bloch and Schneider), koreanus (Kishinouye), lineolatus (Cuvier), munroi Collette and Russo, multiradiatus Munro, niphonius (Cuvier), plurilineatus Fourmanoir, queenslandicus (Macleay), semifasciatus (Macleay), and sinensis (Lacepede). A cladistic analysis of 58 characters shows six monophyletic species-groups in Scomberomorus. The sinensis group is monotypic and is defined by the presence of an abrupt downward curve in the lateral line under the first dorsal fin and by its retention of a swim bladder. The commerson species-group contains commerson, niphonius, queenslandicus, and cavalla and is defined by the presence of an intercalar spine of at least moderate length. Scomberomorus cavalla and S. commerson share two additional specializations, the pterosphenoid bones are close together and the lateral line curves abruptly downward under the second dorsal finlets. The munroi species-group is monotypic and is defined by the loss of the anterior process on the outer surface of the head of the maxilla. The semifasciatus species-group contains semifasciatus, plurilineatus, and lineolatus, and is defined by the presence of a greatly expanded posterior end of the maxilla. Scom-beromorus lineolatus and S. semifasciatus share an additional specialization, a wide parasphenoid, but this character state appears independently in several other lines. The guttatus species-group contains guttatus, multiradiatus, and koreanus and is defined by a high supraoccipital crest. Auxil-iary branches extend off the anterior part of the lateral line in S. guttatus and S. koreanus. The regalis species-group contains regalis, tritor, maculatus, concolor, sierra, and brasiliensis and is defined by the presence of nasal denticles. All but the most primitive species in this group (S. tritor) have an artery arising from the fourth left epibranchial artery. The four most advanced species (all except tritor and maculatus ) have developed a long posterior process on the pelvic girdle. The three most advanced species (sierra, brasiliensis, and regalis) have a coeliaco-mesenteric shunt connect-ing the fourth right epibranchial artery with the coeliaco-mesenteric artery. The purposes of this paper are to define the 18 species of Scomberomorus, to clarify their rela-tionships, and to assess the systematic position of Scomberomorus within the Scombridae. The methods used are similar to those of Collette and Chao (1975) in a revision of the bonitos and of Gibbs and Collette (1967) in a revision of Thun-1 National Marine Fisheries Service, Systematics Laboratory, National Museum of Natural History, Washington, DC 20560. National Marine Fisheries Service, Systematics Laboratory, National Museum of Natural History, Washington, DC 20560, and Department of Biological Sciences, The George Washington University, Washington, DC 20006; present address: Office of Information Research Resource Management, Smithsonian Institution, Washington, DC 20560. nus, and rely on previous work by Kishinouye (1923), Munro (1943), Mago Leccia (1958), and Devaraj (1977). The Spanish mackerels have been placed by Collette and Chao (1975) and Collette and Russo (1979) in a tribe (the Scomberomorini) along with Acanthocybium and Grammatorcynus, interme-diate between the more primitive mackerels (Scombrini) and the more advanced bonitos (Sar-dini). Acanthocybium is clearly the specialized sister group of Scomberomorus, but the phylo-genetic position of Grammatorcynus has been unclear. Until recently, the number of valid species of Manuscript accepted November 1983. FISHERY BULLETIN: VOL. 82, NO. 4, 1984. 545
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