TRIAKIDAE

FAMILY TRIAKIDAE View in CoL

The caudal fin has a distinct ventral lobe (however, almost absent in Triakis ) and a large terminal dorsal lobe, especially in Galeorhinus (almost one-half of the entire caudal fin length) ( Figs 3 View Figure 3 , 4 View Figure 4 ). Preceding the caudal fin skeleton is a thin cartilaginous plate situated distally to the haemal arch (arrow in Figs 3 View Figure 3 , 4A View Figure 4 ). The caudal fin skeleton of examined triakids has ~53–62 VC ( Table 1), the basidorsal and interdorsal cartilages are truncated, and the supraneural spines are elongated, curved and terminally tapering. The caudal fin skeletons of Mustelus , Triakis and Galeorhinus are divided into anterior and posterior diplospondylic caudal regions (Table 2). The anterior diplospondylic caudal region has six to seven VC ( Table 1). The basiventral cartilages in this region are pentagonal in Mustelus and Triakis ( Fig. 3 View Figure 3 ) and have clear anterior apophyses (anterior prominences) in Galeorhinus (arrow in Fig. 4B View Figure 4 ). The first haemal spines are somewhat anteriorly concave. The haemal spines are slightly more slender in Galeorhinus than in Mustelus and Triakis . In the posterior diplospondylic caudal region, most of the haemal spines are anteriorly convex. At the posterior extremity of the caudal fin, in all examined genera of Triakidae , haemal spines are reduced and basiventral cartilages absent.

Table 2. Anatomic regions of carcharhiniforms caudal fin

ACD, anterior caudal diplospondylic region; DC, diplospondylic caudal region; PCD, posterior caudal diplospondylic region.