Thalamitoides A. Milne-Edwards, 1869

Huang, Yu-Hsuan & Shih, Hsi-Te, 2021, Chthonius rhodochelatus Hadzi 1933, Zoological Studies 60 (60), pp. 1-45 : 26

Genus Thalamitoides A. Milne-Edwards, 1869 Thalamitoides quadridens A. Milne-Edwards, 1869

( Figs. 4C , 15 )

Thalamitoides quadridens A. Milne-Edwards, 1869: 147 , pl. 6(8–15) (type locality: Madagascar); Stephenson and Rees 1967: 101, fig. 37 (Hawaii; Samoa; Philippines); Sakai 1976: 381, pl. 134(3) ( Japan: Ryukyus); Cariaso and Garcia 1986: 237, fig. 43 ( Philippines); Dai and Xu 1991: 35, fig. 26 (Nansha Is.); Ng et al. 2008: 155 (list); Yang et al. 2008: 791 (list) (Nansha Is.); Yang et al. 2012: 342, fig. 135, pl. 14(7) (Nansha Is.); Sasaki 2019: 9276 (list).

Material examined: Taiwan: 1 male (25.4 × 13.3 mm) ( NTOU), Sansiantai, Taitung, 1 Jul. 1987.

Diagnosis: Carapace with surface smooth, slightly convex, 1.9 times broader than long, broadest between anterolateral tooth 2. Frontal and mesogastric ridges unbroken; epibranchial regions with a pair of ridges; protogastric, metagastric, mesobranchial and cardiac ridges absent ( Fig. 15A ). Front with 4 lobes, median 2 lobes 2.5 times broader than lateral. Supraorbital margins with 2 notches, inner lobe slightly arched ( Fig. 15A ). Anterolateral margins with 4 teeth, decreasing in size posteriorly, tooth 1 with posterior margin serrated ( Fig. 15A ). Basal antennal segment with a row of granules. Chelipedal merus with 4 spines on inner margin, distal end of ventral surface with a spinule near articulation of carpus; carpus with 5–6 sharp spines; palm with 2 rows of spines on dorsal surface, inner row with 4 spines, outer with 5 spines; finger tips spoon-shaped ( Fig. 15C ). P5 with merus having strong spine on inner margin, distal end with small spine; propodus with 8 sharp spines on inner margin, dactylus with spinules on distal margins ( Fig. 15B ). Male pleon with pleomere 6 trapezoidal. G1 stout, distal part with bristles on lateral side ( Fig. 15D–G ).

Distribution: Hawaii; French Polynesia; Samoa; Fiji; New Caledonia; Australia (western); Indonesia (Banda); East Timor; Guam; Philippines; Nansha Is.; Taiwan (Sansiantai, Taitung; Fig. 1 : no. 13); Japan (Ryukyus); Thailand; Red Sea; Somalia; Tanzania; Mayotte I.; Madagascar ( Sasaki 2019; this study).

Ecological notes: The habitats include coral reefs and shallow waters ( Sakai 1976).

Remarks: The genus Thalamitoides A. Milne-Edwards, 1869 currently contains 3 species, viz. Tho. quadridens A. Milne-Edwards, 1869 , Tho. spinigera Nobili, 1905 and Tho. tridens A. Milne-Edwards, 1869 ( Ng et al. 2008). Geographically, Tho. quadridens and Tho. tridens are distributed in the Indo-West Pacific; and Tho. spinigera is in the northwestern Indian Ocean ( Sasaki 2019). The specimen from Taiwan is consistent with Tho. quadridens by the character of 4 anterolateral teeth ( Fig. 15A; A . Milne-Edwards 1869: pl. 6 (8, 15)) (vs. 3 teeth in Tho. spinigera and Tho. tridens ( Fig. 16A; A . Milne-Edwards 1869: pl. 6(1); Spiridonov and Neumann 2008: fig. 2A).

Figures

Fig. 4. Species of the family Portunidae. A, Thalamita gatavakensis Nobili, 1906, male (16.5 × 9.3 mm) (NTOU), Mao-ao, New Taipei City; B, Thalamita spinifera Borradaile, 1902, female (12.6 × 9.0 mm) (NCHUZOOL 16531), Erzihliao Fishing Port, Kaohsiung; C, Thalamitoides quadridens A. Milne-Edwards, 1869, male (25.4 × 13.3 mm) (NTOU), Sansiantai, Taitung; D, Thalamitoides tridens A. Milne-Edwards, 1869, female (16.1 × 8.2 mm) (NCHUZOOL 16520), Dongsha I.; E, Thranita cerasma (Wee & Ng, 1995), female (66.4 × 42.6 mm) (NCHUZOOL 16537), Dongsha I.; F, Thranita coeruleipes (Hombron & Jacquinot, 1846), male (59.7 × 40.5 mm) (NCHUZOOL 16507), Wanlitong, Kenting, Pingtung.

Fig. 15. Thalamitoides quadridens A. Milne-Edwards, 1869, male (25.4 × 13.3 mm) (NTOU). A, carapace; B, right P5 (dorsal view); C, right cheliped (dorsal view); D–G, right G1; D, E, dorsal view; F, G, ventral view.

Fig. 1. Taiwan main island and adjacent islets, with the collection localities shown in gray circles (see Table 1).

Fig. 16. Thalamitoides tridens A. Milne-Edwards, 1869, male (14.9 × 7.4 mm). A, carapace; B, basal antennal segment; C, palm of left cheliped (outer view); D–E, right G1; D, dorsal view; E, ventral view.