Squatina Dumeril

Jonathan H. Walsh & David A. Ebert, 2007, A review of the systematics of western North Pacific angel sharks, genus Squatina, with redescriptions of Squatina formosa, S. japonica, and S. nebulosa (Chondrichthyes: Squatiniformes, Squatinidae)., Zootaxa 1551, pp. 31-47 : 46

[[ Genus Squatina Dumeril ]]

The main confusion among WNP squatinids lies in differentiating S. formosa and S. nebulosa from one another. The main character used in the past to differentiate these two species was the number of dermal lobes at the corners of the mouth (Chen 1963, Nakabo 2002, Compagno 2005a). Based upon our examination, this character does not appear to be robust in separating these species. Although all S. formosa individuals studied had one dermal lobe, S. nebulosa specimens had one or two lobes, invalidating this character as a method of separating the two species. Additionally, the number of dermal lobes was often difficult to determine since differentiation between lobes is often vague and these lobes are susceptible to damage during capture and or preservation of specimens. A combination of characters should be used to identify individuals of these two species, since the differences are subtle and a great deal of overlap exists among many characters. The best characters available, based on our findings, appear to be the shape of the caudal pelvic and dorsal fins, the ratio of standardized pelvic girdle distance with the standardized head length, and the shape and height of the upper lip arch. The upper lip arch appears to be of particular value as a field character. It is a feature that is not prone to damage and is easy to assess quickly in the field. More specimens are needed to assess the utility of this character but it appears to be useful for all WNP squatinids.

Based on the key characters presented herein, we provide the following key to the WNP squatinids:

Key to Western North Pacific Squatina Species

1. Pelvic fin tips do not extend to origin of first dorsal fin..............................................................................2.

- Pelvic fin tips extend to or surpass origin of first dorsal fin........................................................................3.

2. A prominent row of thorn-like denticles extending from mid-back to caudal peduncle; no distinct ocelli on posterior lobes of the pectoral fins................................................................................................ S. japonica

- No row of thorn-like denticles extending from the mid-back to the caudal peduncle, distinct paired ocelli on the posterior lobes of the pectoral fins......................................................................... S. tergocellatoides

3. Upper lip arch semi-circular in shape (>1.5% TL in height); dorsals are lobed with a curvilinear anterior margin; pelvic girdle distance 1.4 times or less head length; caudal fin is lobed, especially dorsally, with a curvilinear postventral caudal margin........................................................................................... S. formosa

- Upper lip arch is not semi-circular in shape (<1.5% TL in height); dorsals are not lobed (angular) without a curvilinear anterior margin (straight); pelvic girdle distance greater than 1.4 times head length; caudal fin is not lobed (angular), especially dorsally, without a curvilinear postventral caudal margin (straight) ... ..................................................................................................................................................... S. nebulosa