Scallasis caledonica (Ngoc-Ho, 1991)

Komai, Tomoyuki, Poore, Gary C. B. & Fujita, Yoshihisa, 2020, Redescription of the poorly known ghost shrimp species, Scallasis amboinae Bate, 1888, review of the genus, and description of a new species from the Ryukyu Islands, Japan (Decapoda: Axiidea: Callianassidae), Zootaxa 4766 (3), pp. 401-420 : 408

Scallasis caledonica ( Ngoc-Ho, 1991)

Callianassa caledonica Ngoc-Ho, 1991: 285–287, fig. 2.— Dworschak 2007: 307.

Trypaea caledonica .— Sakai 2011a: 395.

Scallasis caledonica .— Poore et al. 2019: 143.

Type material. Holotype: New Caledonia, Lagon Est , 21 m, 13 January 1987, female (cl 5.0 mm), MNHN-Th 1072 .

Paratype: Same data as holotype, 1 female lacking pleon (cl 5.0 mm), MNHN-Th 1073; 1 male lacking pleon (cl 4.0 mm), 2 males (cl 4.5, 5.0 mm), MNHN-Th 1074.

Diagnosis. Pleomere 6 as long as wide. Telson 0.8 times as long as wide; greatest width 1.2 times posterior width. Maxilliped 3 ischium-merus 3 times as long as wide; merus free distal margin transverse, rounded. Female major cheliped ischium lower margin with 6–8 small spines; merus lower margin with simple proximal spine; palm 0.9 times as long as carpus. Male major cheliped merus lower margin as in female; dactylus as in female. Minor cheliped ischium lower margin with 10 small serrations; merus lower margin with 1 oblique spine at midpoint. Male pleopod 1 of 1 minute article. Male pleopod 2 absent. Uropodal endopod anterior margin with small spine about two-thirds along; dorsal surface with 1 long proximal spiniform seta, usually plus 1 shorter submarginal seta; exopod anterior margin with small spiniform seta about three-quarters along.

Distribution. Known only from the type locality in New Caledonia.

Remarks. Scallasis caledonica was originally described on the basis of five specimens from Lagon Est, New Caledonia ( Ngoc-Ho 1991; as Callianassa ). We have re-examined the type material and can confirm the accuracy of Ngoc-Ho’s figures, the only exception being the presence of two long facial spiniform setae and another distally on the anterior margin of the uropodal endopod. The male possesses a minute, pear-shaped pleopod 1 but lacks pleopod 2. Ngoc-Ho (1991) noted that the chelipeds were only slightly sexually dimorphic. Differences from S. amboinae are subtle: the distal margin of the merus of maxilliped 3 is less oblique, and the major cheliped is more compact, its meral tooth being proximal and triangular, rather than spine-like.

Sakai (1999) considered Callianassa caledonica a junior synonym of “ Callianassa ” pygmaea while Dworschak (2007) considered it a valid species. Sakai’s (2010) treatment of Callianassa caledonica was not consistent: under the account of Trypaea andamaniensis , he stated “ T. caledonica is considered to be a separate species”, whereas under the account of Trypaea tonkinae he viewed it as a questionable synonym.