Medaeops serenei Ng & Mclay, 2007, new species

Medaeops serenei, new species

Figs. 4–7

Material examined: Holotype: male, 29.0 x 19.6 mm, station TAN0411-10, northwest Kermadec Ridge, New Zealand, 25º53.41–53.61’S, 177º11.10–11.07’E, 139–236 m, 4 October 2004. Paratype: 1 male, 23.8 x 16.4 mm, same data as holotype.

Description of holotype male. Carapace clearly broader than long (ratio = 1.5), most regions well marked by prominent grooves; grooves demarcating gastric regions relatively shallower, 1–4M all discernible, 1M highest part of carapace, separated from 2M by shallow broad grooves, 2M with groups of flattened granules with distinct longitudinal median groove which ends well before posterior margin, 2M separated from 3M by shallow grooves, 4M distinct. Front prominent, truncate, with deep notch which extends posteriorly from frontal margin, edge bearing strong blunt tubercles terminating laterally by larger tubercle with smaller tubercles behind; deep groove separates front, supraorbital margin that begins with tuberculated ridge directed anterolaterally, continuing concave margin armed with uniform small tubercles, interrupted by shallow groove, another groove marking off large external orbital tooth. Infraorbital margin concave, uniformly tuberculated beginning, ending with distinct tooth, visible dorsally, inner tooth longer. 1F, 2F not well marked, surface covered with small granules. 1L, 3L, 4L not well demarcated, area covered with granules; 2L, 5L well demarcated, anterior margin with row of more prominent granules, especially on 2L. 1P, 2P well demarcated, covered with small granules; posterior edge of 2P with low granuliform crest. 1R, 2R poorly demarcated. Orbits oblique, small; cornea well developed. Anterolateral carapace margin convex, marked by four distinct tuberculated, triangular teeth, excluding external orbital corner, first tooth on same level as infraorbital margin, second, third teeth largest, fourth tooth marking widest point of carapace. Posterolateral margin gently concave, margins granular. Antennules folding transversely, antennal flagellum short, passes through open orbital hiatus, urinal article inflated, smooth, slightly mobile, second, third articles granular, fixed, filling orbit, flagella short. Posterior margin of epistome deeply notched on either side of mid-line. Sub-orbital, subhepatic, pterygostomial, sub-branchial regions granular.

Outer surface of third maxilliped minutely granular, more so distally. Basis sub-triangular, ischium subrectangular medial margin minutely granular, setose, shallow sub-medial longitudinal sulcus. Merus subquadrate, granular except in two smooth sunken areas, antero-external margin produced laterally. Exopod not reaching distal margin of merus.

Chelipeds well developed compared to ambulatory legs, dorsal border cristate, carpus with blunt projection on inner distal margin, dorsal surface with an irregular lace-like pattern of granules, two short transverse granulated ridges near dorsal articulation with propodus; outer face of propodus minutely granular, with 2 faint longitudinal lines of larger granules, dorsal margin elevated marked with two interrupted ridges leading to articulation with dactylus; both dactylus, fixed finger black, outer surface of fixed finger with deep pits, distinct groove running almost to tip of finger; fingers gaping, right cheliped with three or four blunt teeth on each finger, left cheliped margins more closely approximated, three small blunt teeth on fixed finger, margin of dactylus scissor-like; tips of fingers on both chelipeds cross at tips when closed with dactylus inside fixed finger.

Ambulatory legs sparsely setose, shorter than chelipeds, decreasing in length posteriorly, articles laterally flattened, dorsal margins weakly granular, ventral margins rounded. Meri longest with dorsal ridge interrupted by distal notch just before meral-carpal joint. Dactylus relatively short, most of surface, except for tip, covered with very short setae.

Thoracic sternum broad, surface finely granular; sternites 1, 2 fused; suture between sternites 3, 4 complete; suture between sternites 3, 4 interrupted, only visible medially, laterally. Abdomen T-shaped; telson wider than long, margin semi-circular, evenly curved, surface with central circular sulcus. Segments 3-5 fused, surface granular, sutures scarcely evident; segment 6 oblong, lateral margins parallel, wider than long; pits for abdominal-locking mechanism well developed; segment 1 transversed by prominent granular ridge. G1 stout, strongly curved, narrowing distally, inner margin adorned with row of sparse sub-distal setae that are directed proximally. G2 short, curved, about one-third length of G1, flagellum with short projection.

Etymology. The new species of Medaeops is named in honour of Raoul Serène who made immense contributions to the study of Indo-West Pacific crabs, and whose 1984 monograph on the Xanthidae and Trapeziidae (Serène 1984) remains a classic on the Xanthoidea.

Remarks. The new species of Medaeops is closest to M. neglectus in that both species have four anterolateral teeth and heavily ornamented carapace, but they differ in that Medaeops serenei only has the regions on the anterior third well demarcated by deep grooves while in M. neglectus the regions on the anterior twothirds are well demarcated by deep grooves and ornamented with prominent granules. Medaeops neglectus also has a grooved pattern, which runs across from side to side, superimposed on the carapace features. Medaeops serenei differs from M. edwardsi in that its anterolateral margins are interrupted by teeth whereas in the latter species the margin is largely entire and the carapace is less granulated. M. granulosus has carinate anterior margins on the ambulatory legs while the new species is sparsely granulate.

The size, depth and distribution of the species in this genus are summarized in Table 2.

1. Anterolateral teeth only weakly developed on an evenly convex margin Medaeops edwardsi Guinot, 1967

– Anterolateral teeth prominent, broad .......................................................................................................... 2

2. Ambulatory legs distinctly carinate along anterior margins ............ Medaeops granulosus (Haswell, 1882)

– Ambulatory legs not distinctly carinate along anterior margins.................................................................. 3

3. Carapace region 4M distinct; ambulatory legs with row of spaced teeth along anterior margins of meri .... .............................................................................................................. Medaeops merodontos Davie, 1997

– Carapace region 4M not distinct; ambulatory legs with anterior margins of meri smooth or with at most large granules.............................................................................................................................................. 4

4. Carapace evenly granular. Frontal lobes separated by a broad notch; relatively long, narrow ambulatory legs. ............................................................................................................... Medaeops gemini Davie, 1997

– Carapace with granules arranged in clumps especially on anterior third; frontal lobes separated by a nar- row slit or notch; relatively short ambulatory legs ...................................................................................... 5

5. Carapace regions 4L, 5L and 6L well marked; abdominal segment 6 with concave margins ...................... ................................................................................................................ Medaeops neglectus (Balss, 1922)

– Only anterior margins of carapace regions 4L and 5L deeply incised; abdominal segment 6 with straight parallel margins .......................................................................................... Medaeops serenei, new species.

Discussion. Chilton (1911) published the first list of brachyurans from the Kermadec Islands. This was based on material collected by W. R. B. Oliver and others during their stay in 1908 and specimens collected by Captain Bollons during a visit to the islands by the government steamer Hinemoa. He provided a list of five species of xanthid crabs. Until recently little attention has been paid to the crustacean fauna of the islands but the detailed work of Takeda & Webber (2006) recently reported 15 species. The two new species reported here brings the number of xanthids to 17 species from nine of the 10 known subfamilies of Xanthidae (Table 3). Interestingly, none of these species are yet known from mainland New Zealand (McLay 1988).

Actaeinae

Gaillardiellus bathus Davie, 1997

Gaillardiellus rueppelli (Krauss, 1843)

Pseudoliomera helleri (A. Milne-Edwards, 1865) Serenius actaeoides (A. Milne-Edwards, 1873) [reported by Chilton (1911) as Lophactaea]

Antrocarcininae

Antrocarcinus petrosus Ng & Chia, 1994

Euxanthinae

Medaeops serenei, new species Miersiela haswelli (Miers, 1886)

Liomerinae

Liomera yaldwyni Takeda & Webber, 2006 Polydectinae

Lybia leptochelis (Zehntner, 1894) Zalasiinae

Banareia armata A. Milne-Edwards, 1873 [reported by Chilton (1911) as Banareia banareias (Rathbun, 1911)]

Zosiminae

Platypodia delli Takeda & Webber, 2006