Comparative Osteology of Serranid Fishes of the Genus Roccus (Mitchill)

Abstract

HE serranid genus Roccus occurs between the parallels 50'N and 25?N and is represented by six species; saxatilis, chrysops, americanus and interruptus in North America, labrax and punctatus in Europe. The six species formerly were assigned to as many as five genera by authors. Jordan and Gilbert (1883:528-531), first to revise the genus, relegated the four American species to the genus Roccus (with Morone as a subgenus) and tentatively included the two European species. External characteristics were used as criteria. Later Berg (1949: 1012-1013) assigned them to a single genus, Morone, with three subgenera, and gave as diagnostic generic characters: (1) separate dorsal fins, (2) teeth present on the base of the tongue, and (3) absence of a supramaxillary bone. His classification of subgenera was also based primarily on external characters. The present osteological study was undertaken to check the validity of a monogeneric classification. Five species, saxatilis, chrysops, americanus, interruptus and labrax, were compared. The findings indicate that biologically the species are of a single genus. Subgenera may be defined using combinations of skeletal characters. Starks (1901: fig. 45, pls. 63-65) used the skeleton of saxatilis in illustrating the synonymy of the fish skeleton and with the exception of the trunk skeleton the same illustrations appeared in Jordan (1905: figs. 22-26 and 28). Excellent figures of the head skeleton are given by Gregory (1918: figs. 1, 2, 6, 7). He (1933: figs. 1 and 119) also discusses and illustrates the head skeleton in his monograph on fish skulls. Merriman's (1940: 55-64) fine paper describes the trunk skeleton of saxatilis and includes detailed drawings of the parts. Giinther (1859: 66) described the skeleton of americanus, and a dorsal view of the skull of labrax appeared in Boulenger (1895: 125). Terminology for the skull components follows Gregory (1933); that of the trunk skeleton is after Merriman (1940). In the present study the skeletons of five species of Roccus are compared. Lack of readily available study material of punctatus precluded its use here. Mitchill (1815: 415) refers to an aberrant form of saxatilis which has broken or inter-