Latatheres affinis (H. Milne Edwards, 1853 ) Ahyong, 2018

Ahyong, Shane T., 2018, Revision of Ostracotheres H. Milne Edwards, 1853 (Crustacea: Brachyura: Pinnotheridae), Raffles Bulletin of Zoology 66, pp. 538-571 : 566-567

Latatheres affinis (H. Milne Edwards, 1853) new combination

( Figs. 13 , 15 )

Ostracotheres affinis H. Milne Edwards, 1853: 220 , pl. 11 fig. 11. — Paulson, 1875: 70. — Tesch, 1918: 262, 263, 287. — Guinot, 1967: 279. — Silas & Alagarswarmi, 1967: 1195. — Schmitt et al., 1973: 6, 7, 28. — Takeda & Konishi, 1989: 1222. — Ng et al., 2008: 250.

Ostracoteres affinis . — Nobili, 1906b: 299, 300–301. — Michel, 1964: 10.

Type material. Neotype: MNHN IU-2016-10944 (B10570), ovigerous female (cl 4.5 mm, cw 5.8 mm), Djibouti, coll. Jouseaume, 1891.

Other material examined. MNHN IU- 2016-10945 (B10571), 1 ovigerous female (cl 6.5 mm, cw 8.2 mm), Djibouti, coll. Jouseaume, 1891.

Description. Female: Carapace ovate ( Fig. 15A ), wider than long, surface finely and sparsely setose; strongly vaulted longitudinally, rounded in lateral view; front transverse, straight, not produced, frontal width about 1/4 carapace width; anterolateral margins undefined, rounded; dorsal surface smooth, regions not indicated.

Epistome ( Fig. 15B ) with narrowly triangular interantennular septum; median buccal margin with obtuse median point. Antennular sinus larger than orbit; antennules folded obliquely. Antenna short, free antennal articles extending to about ¾ height of eye; antennal articles 1 and 2 fused to epistome. Eye filling orbit, cornea pigmented.

Maxilliped 3 ( Fig. 15C ) ischiomerus length about 2.5 × width; surface sparsely, finely setose; inner margin weakly concave, distomesial margin rounded, produced slightly beyond palp articulation; outer margin strongly convex. Carpus about half propodus length. Propodus spatulate, gently tapering, apex narrowly rounded. Exopod margins straight to weakly convex.

Cheliped (pereopod 1) very sparsely setose ( Fig. 15A, D ). Dactylus and pollex curved, apices crossing distally, without gape. Dactylus shorter than dorsal margin of propodus palm, occlusal margin with triangular tooth proximally. Pollex occlusal margin weakly crenulate, with small, traiangular tooth near midlength; inner ventral margin with row of setae. Propodus palm dorsal margin length 1.4 × height; ventral margin distinctly evenly convex. Carpus and merus unarmed; merus slender, as long as propodus.

Walking legs (pereopods 2–5) similar, slender ( Fig. 15A, E–H ); relative lengths: pereopod 3>pereopod 2>pereopod 4>pereopod 5; surfaces very sparsely setose; P5 articulating with body at same level as pereopod 4. Meri unarmed, length 4.9–5.6 × height (pereopods 2–4), 4.6 × height (pereopod 5). Propodi unarmed, 4.6–4.7 × height. Dactyli simple, sparsely setose, that of pereopod 3 longest; pereopod 2 dactylus strongly falcate, apex spiniform, perpendicular to main dactylar axis; pereopod 3–5 dactyli similar, stout, weakly curved; pereopod 2–3 dactyli 0.5 × propodus length; pereopod 4 dactylus 0.4 × propodus length; pereopod 5 dactylus 0.6 × propodus length.

Hosts. Not known.

Remarks. Latatheres affinis new combination, originally described from Mauritius, was neither well illustrated nor well described by H. Milne Edwards (1853), who provided only a figure of maxilliped 3 and minimal indications of appendage differences relative to O. savignyi (= O. tridacnae ). As a result, it is not possible to determine the identity of H. Milne Edwards’ species with any degree of confidence based on the type description. The current concept of L. affinis is based on Nobili’s (1906b) account of specimens from Djibouti, examined here, which presumably were identified based on the similar maxilliped 3 to that figured by H. Milne Edwards (1853: pl. 11 fig. 11). Although Nobili (1906b: 300) referred to the carapace and walking legs of the present specimens as “légèrement duveteuses” [slightly furry], they are largely glabrous. Only very few, short, sparsely scattered setae are now present on the carapace, pereopods and margins of the abdomen of the extant specimens. Much of the original setation was doubtless lost over time, possibly during past specimen preparation, although the original degree of setation was in any case probably sparse and much less extensive than possibly implied by Nobili (1906b). Nobili’s description of the setation in L. affinis may have been made with other pinnotherids from the region in mind, such as O. tridacnae , which is tomentose overall, and D. spondyli , with its glabrous carapace and near glabrous walking legs.

The original type material of L. affinis is now lost ( Schmitt et al., 1973; Guinot pers. com.), and no material from Mauritius is available for study. Given the ambiguous identity of the species and lack of extant type material, one of Nobili’s Djibouti specimens (ovigerous female, cl 4.5 mm, MNHN IU-2016-10944) is herein designated as the neotype to fix the identity of L. affinis .

Differences between L. affinis and L. tomentipes are outlined under the account of the latter.

Distribution. Western Indian Ocean, from Djibouti and Mauritius; bathymetric range not known.

Figures

Fig. 13. Distribution of species of Latatheres new genus. (●) L. affinis (H. Milne Edwards, 1853) new combination; (■) L. tomentipes (Takeda & Konishi, 1994) new combination.

Fig. 15. Latatheres affinis (H. Milne Edwards, 1853) new combination, ovigerous female neotype, cl 4.5 mm, cw 5.8 mm, Djibouti, MNHN IU-2016-10944. A, dorsal habitus; B, cephalothorax, anterior view; C, right maxilliped 3; D, right chela, anterior view; E–H, right pereopods 2–5. Scale: A, D = 1.0 mm; B, C, E–H = 0.5 mm.