Isistius labialis Meng, Zhu & Li, 1985b

White, William T. & Last, Peter R., 2013, Notes on shark and ray types at the South China Sea Fisheries Research Institute (SCSFRI) in Guangzhou, China, Zootaxa 3752 (1), pp. 228-248 : 236

Isistius labialis Meng, Zhu & Li, 1985b

[= Isistius brasiliensis ( Quoy & Gaimard, 1824) ]

( Figures 10a , 11 )

Isistius labialis Meng, Zhu & Li, 1985b: 442 , fig. 1 (South China Sea) – Compagno, 1999: 475; Compagno in Randall & Lim, 2000: 580; Compagno et al., 2005a: 128, fig., pl. 14.

Material examined. SCSFRI S 07257 (holotype), female 442 mm TL, South China Sea, 18°40'– 19°32' N, 112°31'– 113°57' E, depth 520 m, Oct 1980 .

Remarks. Described by Meng et al. (1985b) based on a single specimens collected from the South China Sea. Tentatively considered as valid by Compagno (1999) and Compagno in Randall & Lim (2000) and treated as a nominal species in Compagno et al. (2005a). This species is very similar in appearance to Isistius brasiliensis ( Quoy & Gaimard, 1824) , with its brown colouration with a distinct, dark brown collar marking, fins with pale posterior margins, and dorsal fins set far back on body and relatively well separated (which separate it from Isistius plutodus Garrick & Springer, 1964 ). The main characters distinguishing this species from I. brasiliensis according to Compagno et al. (2005a) are: upper teeth more numerous (43 vs. 31–37 rows), eyes slightly further forward and caudal fin with a shorter ventral lobe. Following examination of the holotype, the latter two character states do not hold up in distinguishing this species from I. brasiliensis (see Figure 10b ). In the original description, Meng et al. (1985b) distinguished I. labialis from I. brasiliensis in having: transverse, waved labial fold; snout shorter than eye diameter (vs. equal to); eye diameter two thirds (vs. half) of preoral length; height of pelvic fin equal to (vs. larger) the dorsal fins. However, when the holotype was compared with specimens of I. brasiliensis , the snout and eye proportions do not differ markedly and it is likely intraspecific variation was not considered. The statement about the pelvic fin being similar in size to the dorsal fins, which is also shown in the illustration in Compagno et al. (2005a, p. 128), is not reflected in the holotype of I. labialis which has pelvic fins clearly larger than the dorsal fins. Thus, the only characters remaining to separate the two species are the higher number of upper tooth rows and the presence of a large labial fold connecting lower labial furrows. However, the holotype was found to have a lower upper tooth row count of 35, or 17–1–17 (Flávia Petean, pers. comm.), compared to the 43 reported in Meng et al. (1985b); this falls within the upper tooth count range for I. brasiliensis of 31–37. Based on this information, I. labialis cannot be adequately distinguished from I. brasiliensis and we suggest that it should be considered a junior synonym of Isistius brasiliensis ( Quoy & Gaimard, 1824) .

Figures

FIGURE 10. Lateral view of: A. holotype of Isistius labialis SCSFRI S 07257 (female 442 mm TL); B. Isistius brasiliensis (CSIRO H 5150–01, female 480 mm TL) from off Australia.

FIGURE 11. Holotype of Isistius labialis SCSFRI S 07257 (female 442 mm TL): A. anterior ventral view; B. dentition.