Seiitaoides kabuto Forges & Lee & Ng 2021, n. sp.
Creators: name: Forges, Bertrand Richer De
name: Lee, Bee Yan
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Majidae
Seiitaoides
Seiitaoides kabuto

description: Seiitaoides kabuto n. sp.
(Figures 10A–D; 11A–E)
Material examined. Holotype: ovigerous female (cl 10.0 mm, pcl 8.6 m, cw 5.3 mm, bcw 4.5 mm) (MNHN-IU-2016-7089), stn DW4836, Comoros Islands, 1225’S 4356’E, 82–88 m, coll. BIOMAGLO, 28 January 2017. Paratype: 1 female (cl 11.2 mm, pcl 9.3 mm, cw 5.7 mm, bcw 5.1 mm) (MNHN-IU-2016-7090), 1 ovigerous female (cl 10.1 mm, pcl 8.6 mm, cw 5.3 mm, bcw 4.6 mm) (ZRC 2020.377, ex MNHN-IU-2016-7088), same locality and collection data as holotype.
Diagnosis. Pseudorostral spines short, subcylindrical, gently diverging; outer margin with 2 accessory spines (Fig. 10B, D). Supraocular eave wide, margin entire, proximal part with low, blunt preocular tooth; partially overlaps long sharp flattened postocular spine; intercalated spine short, tightly appressed against eave and postocular spine; no obvious gaps between spines (Fig. 10B, C). Hepatic spine well developed, lobiform, sharp, directed outwards, with distinct boletiform tubercle dorsal to it, separated from postocular spine by wide gap (Fig. 10B, C). Gastric region well defined bearing several plates and granules; median part with 2 large circular plates arranged longitudinally, appressed against each other; protogastric region with 2 small round plates, laterally appressed; cardiac region raised, with 2 large lateral plates fused medially; branchial region with 3 closely arranged plates (Fig. 10B, D; Fig. 11A). Intestinal region, posterior carapace margin and posterolateral margin forming 1 broad brace-like granuliform plate, vaguely divided into 3 parts (Fig. 10B, D). Epistome quadrate (Fig. 11B). Third maxilliped with ischium distinctly tuberculated (Fig. 11C). Female cheliped short; merus, carpus and chela spiny (Fig. 11D). Ambulatory legs short, with merus and propodus spiny (Figs. 10A, C, 11E). Female pleonal somite 1 with large rounded tubercle covered with small granules (Fig. 10B, D).
Type locality. Comoros Islands.
Etymology. The name alludes to the general appearance of the carapace, superficially resembling a kabuto, the Japanese name for a samurai helmet. The name is used as a Latin noun in apposition.
Remarks. Seiitaioides kabuto n. sp. is morphologically most similar to S. stimpsoni (Miers, 1884, but differs in the pseudorostral spines being slender, with two accessory spinules on the outer margin (Fig. 10C, D) (versus prominently dorsoventrally flattened with margins unarmed in S. stimpsoni; Fig. 12A; Miers 1884: pl. 47 fig. A); having both median gastric plates subequal in size (Fig. 10B, D) (versus posterior plate distinctly smaller in S. stimpsoni; Fig. 12A; Miers 1884: pl. 47 fig. A); the supraorbital eave is long and slopes anteriorly towards the front (Fig. 10B, D) (versus short and subparallel in S. stimpsoni; Fig. 12A; Miers 1884: pl. 47 fig. A); the hepatic region has a small dorsal boletiform tubercle and a large lobiform spine ventral to it (Fig. 10B, D) (versus with only large dorsal boletiform tubercle in S. stimpsoni; Fig. 12A; Miers 1884: pl. 47 fig. A); and the lateral branchial plates are proportionately much larger (Fig. 10B, D) (versus small in S. stimpsoni; Fig. 12A; Miers 1884: pl. 47 fig. A).
The description and figure of S. stimpsoni by Miers (1884: 523, pl. 47 fig. A) does not show an intercalated spine but it is probably present. In S. kabuto n. sp., the intercalated spine is small and tightly appressed against the supraocular eave and postocular spine with no gaps between them (Fig. 10B, C), so much so that the structures appear almost completely fused. It could thus have been easily missed by Miers.
Seiitaioides kabuto n. sp. also resembles S. mirabilis n. sp., with both having large boletiform plates covered by granules. In S. kabuto n. sp., however, the hepatic tooth is long flattened and sharp (Fig. 10B, D) (versus short and thinner in S. mirabilis n. sp.; Fig. 8B); the preocular tooth is overlapping the wide postocular tooth, closing the gap and leaving only a very reduced intercalated spine (Fig. 10B, D) (versus a long blunt postocular tooth not touching the preocular tooth in S. mirabilis n. sp.; Fig. 8B); there is two partially fused plates (Fig. 10B, D) (versus only one large cardiac plate in S. mirabilis n. sp.; Fig. 7B); there are two large gastric plates (Fig. 10B, D) (versus only one cardiform plate in S. mirabilis n. sp.; Fig. 7B); the epistome is squarish (Fig. 11B) (versus longer than wide in S. mirabilis n. sp.; Fig. 9A, B); and the ambulatory legs are spiny (Fig. 10A, 11E) (versus smooth in S. mirabilis n. sp.; Fig. 8A, 9D).
description: Published as part of Forges, Bertrand Richer De, Lee, Bee Yan & Ng, Peter K. L., 2021, The taxonomy of spider crabs of the genera Eurynome, Choniognathus, Seiitaiodes and Kasagia (Crustacea: Brachyura: Majidae) from southwest Indian Ocean, pp. 301-333 in Zootaxa 5048 (3) on pages 317-319, DOI: 10.11646/zootaxa.5048.3.1, http://zenodo.org/record/5556341