Chinommatia littoralis Tesch 1918
Creators: name: Ng, Peter K. L.
name: Rahayu, Dwi Listyo
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chasmocarcinidae
Chinommatia
Chinommatia littoralis

description: Chinommatia littoralis (Tesch, 1918)
(Figs. 1–4)
Hephthopelta littoralis Tesch, 1918: 233, pl. 9, fig. 3 [type localilty: Indonesia]. — Serène 1968: 92 [in list]. — Ng et al. 2008: 76 [in list].
Chinommatia littoralis —Ng & Castro 2016: 70, figs. 15A; 25E; 32C; 43H.
Not Hephthopelta littoralis— Chen 1998: 298, fig. 22 [Nansha Islands, South China Sea] [= Chinommatia cavimanus (Rathbun, 1914)]
Not Hephthopelta littoralis — Zarenkov, 1972: 238, figs. 1–4 [Vietnam] [= Chinommatia cavimanus (Rathbun, 1914)]
Material examined. Holotype: female (4.9 × 3.5 mm) (NNM-ZMA), Indonesia, north coast of Ceram, Waru Bay, Siboga Expedition, stn 174, 18 m, July 1899. Others: 1 male (6.1 × 4.6 mm), 1 female (6.4 × 4.5 mm) (ZRC 2017.0119), Tanimbar Island, Maluku, Indonesia, trawl, 20 m, coll. D.L. Rahayu, October 1994.
Comparative material. See Ng & Castro (2016) for material of other Chinommatia species and Notopelta mortenseni (Serène, 1964).
Diagnosis. Carapace subtrapezoidal, lateral margins gently convex, converging posteriorly; maximum width to length ratio 1.3 in male, 1.4 in females (Figs. 1 B, 2); dorsal surface with fine irregular punctae, with short tomentum in life, otherwise without long setae (Figs. 1 A, B, 2); frontal margin with shallow but visible median cleft (Figs. 1 B, 2C, D); anterolateral margins arcuate, subcristate, granular, with some granules sharp, without distinct lobes or teeth (Figs. 1 B, 2C, D); sub-branchial region not visible in dorsal view for females (Figs. 1 B, 2D) but distinct in male (Fig. 2 C). Eye peduncle relatively long, mobile, dorsal margin almost straight, with small rounded granules (Figs. 2 C, D, 3A, B). Epistome with semicircular median lobe, lateral margins semicircular (Fig. 3 A). Third maxilliped merus subovate, anteroexternal angle not expanded; ischium rectangular, longer than merus (Fig. 3 F). Ambulatory legs with meri relatively short, margins lined with long setae, outer surfaces with low tomentum (Figs. 1 A, B, 2A, B). Fingers of major, minor chela subcircular in cross-section, laterally flattened, blade-like (Fig. 3 G, H); inner proximal part of cutting margin of dactylus of major male chela with gently curved cutting tooth (Fig. 3 G); inner distal margin of cheliped carpus with short, slightly curved tooth (Fig. 2 A, B); inner margin of merus with small tubercles, not spinate (Fig. 2 A, B). Male, female thoracic sternum relatively transversely narrow (Fig. 3 D, I). Male pleon with telson linguiform (Fig. 3 D). Vulva large, without operculum (Fig. 3 J). G1 relatively stout, distal half relatively more slender, distal part with numerous short, stout spines, distal opening relatively large (Fig. 4 A, B). G2 long, more than three-quarters length of G1, basal segment elongated, distal segment short (Fig. 4 C).
Remarks. The holotype female (4.9 × 3.5 mm, NNM-ZMA) from Ceram is in poor condition, with almost all its pereopods detached, some of which are missing (Fig. 1). The specimen is very delicate and no attempt was made to scrape off the setae or tomentum on the carapace. Nevertheless, it shows enough characters to identify the present material from Tanimbar Island with confidence.
Ng & Castro (2016: 70) treated Zarenkov’s (1972: 238, fig. 4) record of “ Hephthopelta littoralis ” as valid, although they commented that “his specimen is depicted with teeth on the cheliped meri rather than tubercles” (Ng & Castro (2016: 70). Comparisons with our fresh material and reappraising his figures leads us to the conclusion that his material from Vietnam almost certainly belongs to Chinommatia cavimanus s. str. instead. His figures of the third maxilliped (Zarenkov, 1972: fig. 4IIImxp; cf. Ng & Castro, 2016: fig. 32A); inner margin of the merus of the cheliped lined with sharp spines (Zarenkov, 1972: fig. 4Iple, 4Ipde; cf. Ng & Castro, 2016: fig. 42J); lateral view of the chela with the inner surface characteristically inflated (Zarenkov, 1972: fig. 4Ipde; cf. Ng & Castro, 2016: fig. 44A, B); male pleon shape (Zarenkov, 1972: fig. 4Abd; cf. Ng & Castro, 2016: fig. 53A, B); and G1 (Zarenkov, 1972: fig. 4Ipl; cf. Ng & Castro, 2016: fig. 75A–C) agree with what has been described and figured for Chinommatia cavimanus s. str. by Ng & Castro (2016). The G2 figured by Zarenkov (1972: fig. 4IIpl) is superficially similar to that by Ng & Castro (2016: fig. 75) for Chinommatia cavimanus s. str. but the distal segment appears to be relatively longer. The depth where Zarenkov’s specimens were collected (10–72 m) is shallower than what has been reported for the species by Ng & Castro (2016: 65). Most of the characters discussed above may also apply to C. bicuspida Ng & Castro, 2016, but this species is known so far only from further south in Papua New Guinea and Fiji. Chen (1998: 298, fig. 22) identified specimens from the South China Sea as “ Hephthopelta littoralis ”, probably following Zarenkov (1972), but Ng & Castro (2016: 64) referred them to Chinommatia cavimanus s. str. after examining photographs of the material. As such, what has been recorded as “ Hephthopelta littoralis ” in the list of Chinese taxa by Jiang (2008: 770) should also be referred to Chinommatia cavimanus s. str.
Ng & Castro (2016: 72) separated Notopelta Ng & Castro, 2016, from Chinommatia by the former possessing a submarginal granular crest along the anterolateral margin, a relatively wide carapace and proportionately wider male thoracic sternum, stout and dorsoventrally flattened (reniform) eyestalks, and the adult male major cheliped with a prominent ischial projection. Chinommatia littoralis is superficially close to Notopelta mortenseni, and the present specimens of Chinommatia littoralis challenge several of the diagnostic characters used to define Notopelta. The carapace of Chinommatia littoralis is relatively wider than most Chinommatia species; the width to length ratio of the male is 1.3 while those of the two females are 1.4. These proportions approach that of Notopelta mortenseni (width to length ratio 1.4). The granular anterolateral margin of female Chinommatia littoralis is marginal, with the sub-branchial region not visible in dorsal view (Fig. 2 D). In the male, however, the carapace is proportionately broader and part of the sub-branchial region is visible in dorsal view, and the anterolateral margin this appears to submarginal in position (Fig. 2 C), similar to that observed in Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 15G–I). The eye peduncle of Chinommatia littoralis is relatively stout and partly dorsoventrally compressed (Fig. 15H) like that of Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 15H), but it does not have the median part distinctly constricted and not reniform. The G1 and G2 of Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 76F–H) are very similar to those of Chinommatia littoralis. The distal half of the G1 of Chinommatia littoralis, however, is relatively stouter (Fig. 4 A, B) than that of Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 76F–H). Most Chinommatia species have relatively long G2s (cf. Ng & Castro, 2016: fig. 75D, H, M), but proportionately, they are all shorter than those of Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 76I). Unlike other Chinommatia species, the G2 of Chinommatia littoralis is proportionately longer (Fig. 4 C), similar to the condition in Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 76I). Like Chinommatia littoralis, the fingers of both major and minor chelae of Notopelta mortenseni are laterally flattened and blade-like (Fig. 3 G, H; Ng & Castro, 2016: fig. 45A, B).
Significantly at the generic level, the male of Chinommatia littoralis (6.1 × 4.6 mm), although similar in size or larger than those of Notopelta mortenseni examined by Ng & Castro (2016), does not possess a long ischial projection on the ischium of the adult male major cheliped (Fig. 2 A), a diagnostic character for Notopelta mortenseni (cf. Ng & Castro, 2016: fig. 42L). In addition, the male and female thoracic sternum is relatively narrower transversely in Chinommatia littoralis (Fig. 3 D, I) compared to the condition in Notopelta mortenseni (cf. Ng & Castro, 2016: figs. 53F, 87F, G).
Specimens of Chinommatia littoralis can also be separated from Notopelta mortenseni in having a distinct shallow median cleft on the frontal margin (Fig. 1 B, 2C, D) (almost entire in Notopelta mortenseni; cf. Ng & Castro, 2016: fig. 15G–I); dorsal margin of the ocular peduncle lined with small granules (Fig. 2 C, D) (smooth in Notopelta mortenseni; cf. Ng & Castro, 2016: fig. 15H); the anteroexternal angle of the merus of the third maxilliped is not expanded at all (Fig. 3 F) (slightly expanded in Notopelta mortenseni; cf. Ng & Castro, 2016: fig. 32F); the ambulatory meri are relatively shorter (Figs. 1 A, B, 2A, B) (conspicuously longer in Notopelta mortenseni; cf. Ng & Castro, 2016: fig. 15G, I); the female telson is slightly narrower (Fig. 3 I) (slightly wider in Notopelta mortenseni; cf. Ng & Castro, 2016: fig. 87F).
With regards to the structures of the ocular peduncle and ischium of the major male cheliped, and to a lesser degree the proportions of the anterior male and female thoracic sternums, Chinommatia littoralis differs markedly from Notopelta mortenseni. In contrast, the structures of the anterolateral margin, G1 and G2 are closer to those seen in Notopelta mortenseni. As such, Chinommatia littoralis seems to be possess some character states which are intermediate between what Chinomattia and Notopelta. The two genera are kept distinct for the time being.
Distribution. Now known for certain only from the Indonesian Moluccas, from Ceram and now Tanimbar Island. Depth: 18– 20 m.
description: Published as part of Ng, Peter K. L. & Rahayu, Dwi Listyo, 2017, Rediscovery of Chinommatia littoralis (Tesch, 1918) (Crustacea: Decapoda: Brachyura: Chasmocarcinidae) from Tanimbar Island, Indonesia, pp. 494-500 in Zootaxa 4294 (4) on pages 495-500, DOI: 10.11646/zootaxa.4294.4.9, http://zenodo.org/record/832867