Statommatia Ng & Castro, 2016, n. gen.
Creators: name: Ng, Peter K. L.
name: Castro, Peter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chasmocarcinidae
Statommatia

description: Genus Statommatia n. gen.
Hephthopelta — Serène 1964a: 239; 1968: 92 (part).
Type species. Hephthopelta apta Rathbun, 1914 (gender feminine) Other species included:
Statommatia granulosa n. sp.
Statommatia knudseni (Serène, 1964) Statommatia malagasy n. sp.
Statommatia pubescens (Chen, 1998)
Diagnosis. Carapace subtrapezoidal to subovate, distinctly wider than long, gently convex dorsally (granular in S. granulosa; granular, tomentose in S. pubescens); front bilobed, with shallow median cleft; anterolateral margins arcuate, minutely granular, without distinct lobes or teeth (conspicuously granular in S. knudseni). Epistome slightly depressed; posterior margin with broadly semicircular or narrowly rectangular median lobe with deep median fissure, semicircular lateral margins. Eye peduncle filling orbit, short, gently tapering to cornea, immobile; cornea reduced, pigmented. Third maxillipeds not filling buccal cavern when closed; merus subcircular or subquadrate, outer margin nearly curved, even, anteroexternal angle rounded; ischium rectangular to quadrate, about same length as merus or slightly longer than merus. Chelipeds subequal in length, slightly dissimilar in female, heteromorphic in males; fingers of minor chela subcircular in cross-section, not distinctly laterally flattened, gently tapering to tip, scissor-like, cutting margins with distinct sharp teeth; cutting margins of major chela with broad, blunt teeth, largest most proximal on upper, lower cutting margin (dactylus of major chela arched in males of S. apta, S. malagasy); lower, proximal portion of propodi of small male chelipeds bordered by thick tubercles, granules on inner, outer margins forming elevated ridges in S. apta. Ventral surface of cheliped merus with row of small tubercles along outer margin (small teeth in large S. malagasy), inner margin unarmed. Inner margin of cheliped carpus with short distal tooth, proximal part rounded. Inner margin of basis-ischium of adult major cheliped gently granuliform. Ambulatory legs unarmed (P2 merus with few pointed tubercles in S. knudseni). P5 dactylus gently upcurved. Fused thoracic sternites 1, 2 broad, short or long; fused thoracic sternites 3, 4 broad. Male pleon lateral margins of somite 6, fused somites 3‒5 slightly convex; postero-lateral regions as in rest of somite, not particularly swollen; telson proportionally long. Sterno-pleonal cavity of male deep, pressbutton for pleonal holding as small, short tubercle posterior to thoracic sternal suture 4/5 near edge of sternopleonal cavity. Male thoracic sternite 8 long, rectangular; “supplementary plate” long, subrectangular; structures tightly appressed with penis concealed (e.g., Fig. 61 D). G1 with stout basal part; distal part slender, tapering, with short spinules. G2 short, about half or less than length of G1; distal segment short. Somites of female pleon with markedly convex lateral margins; telson proportionally long (unknown in S. knudseni). Sterno-pleonal cavity of female deep, vulvae relatively close together, located between sutures 5/6, 6/7.
Etymology. The name is derived from the arbitrary combination of statos, Greek for “fixed,” and ommatos, Greek for “eye,” in reference to the fixed, non-mobile eyestalks that are diagnostic for the genus. Gender feminine
Remarks. Statommatia n. gen. is characterised by immobile eyes, short eye peduncles, short G2 (about half G1 length), proportionally short male telson, wide, short male thoracic sternites 2, 3, a vertical depression on the male and female thoracic sternites 4, 5, and a vulva on the margin of a shallow sterno-pleonal cavity.
The characteristics and differences between Statommatia n. gen. and the other genera once treated as part of Hephthopelta s. lato are summarised in Table 2.
Distribution. Indo-West Pacific region: western Indian and western Pacific oceans.
description: Published as part of Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), pp. 1-182 in Zootaxa 4209 (1) on pages 72-73, DOI: 10.11646/zootaxa.4209.1.1, http://zenodo.org/record/272646