Oxypleurodon alisae, Lee & Forges & Ng, 2019

Lee, Bee Yan, Forges, Bertrand Richer De & Ng, Peter K. L., 2019, Deep-sea spider crabs of the family Epialtidae MacLeay, 1838, from Papua New Guinea, with a redefinition of Tunepugettia Ng, Komai & Sato, 2017, and descriptions of two new genera (Crustacea: Decapoda: Brachyura: Majoidea), Zootaxa 4619 (1), pp. 1-44 : 5-6

Oxypleurodon alisae n. sp.

( Figs. 1C , 2 A–C, 5A–D)

Material examined. Holotype: male (14.0 × 9.3 mm) (MNHN-IU-2015-227) [photographed], stn CP4336, Ainto Bay , southeast New Britain, Solomon sea, Papua New Guinea, 06°06’S 149°19’E, 314–341 m, coll. MADEEP Expedition, 7 May 2014 . Paratypes: 1 ovigerous female (14.5 × 9.7 mm) ( ZRC 2018.1476 , ex. MNHN-IU-2017- 11834) [photographed], same locality and collection data as holotype.— 1 female (with Sacculina : 10.0 × 7.4 mm) (MNHN-IU-2015-229) [photographed], stn CP4336, Ainto Bay, southeast New Britain, Solomon Sea , 06°06’S 149°19’E, 314–341 m, coll. MADEEP Expedition, 7 May 2014 .— 1 ovigerous female (14.0 × 9.0 mm) (MNHN-IU- 2014-12731) [photographed], stn CP4338, Solomon Sea, Ainto Bay , 06°08’S 149°17’E, 410-614 m, coll. MADEEP Expedition, 7 May 2014 .— 1 carapace only (18.2 × 11.9 mm) (MNHN-IU-2015-892), stn CP4498, Papua New Guinea, New Ireland, 02°21’S 149°56.4’E, 340–465 m, coll. KAVIENG 2014 Expedition, 6 September 2014 . – 1 male (13.1 × 8.5 mm) ( ZRC 2018.1477 , ex. MNHN-IU-2014-18412) , 1 male (10.5 × 7.5 mm), 1 ovigerous female (14.3 × 9.5 mm) (MNHN-IU-2014-18412), stn CP4337, Solomon Sea, Ainto Bay , 06°07’S 149°17’E, 287-447 m, coll. MADEEP Expedition, 7 May 2014 .— 1 male (11.7 × 7.6 mm) (MNHN-IU- 2011-2582), stn CP3631, 06°51’S 147°06’E, 613–652 m, coll. BIOPAPUA, 22 August 2010 .

Diagnosis. Small species (carapace length of 10.5–14.5 mm). Carapace pyriform, with 2 long pseudorostral spines, as long as length of carapace. Pseudorostral spines appressed, fused on proximal third, slightly diverging only on distal third ( Figs. 1C , 2A ); covered by thin tomentum with some longer setae between plates. Carapace with several raised plates as follows: 2 small supraorbital plates; 2 hepatic plates slightly separated, 2 small postorbital plates; 1 elongate mesogastric plate with each side 1 large epigastric granule; 2 sigmoid branchial plates directed outward, lower border of plate forming indentation; 1 cardiac plate forming 2 hook-like projections at interior distal border, forming elliptical-shaped plate; posterior border of carapace forming continuous ridge ( Figs. 1C , 2A ). Lateral side of carapace with 2 long, thin sub-branchial plates ( Fig. 2C ). Antennal flagellum shorter than pseudorostral spines. Basal antennal article longer than broad, enlarged basally, completely fused with carapace, distal angle blunt. Buccal frame covered by third maxilliped. Pterygostomial region with single raised plate on outer margin ( Fig. 2B ). Male cheliped shorter than P2, propodus inflated fingers slightly denticulate, carpus short, merus smooth with 2 distal tubercles. Ambulatory legs with cylindrical articles, dactylus curved. Male anterior thoracic sternites 3 and 4 deeply depressed. Male pleon with 6 articulated somites and telson. G1 straight, flattened at sharp distal tip ( Fig. 5 A–D).

Coloration. Live coloration pinkish-orange with some whitish areas on branchial plates, posterior carapace border and carpus of cheliped ( Fig. 1C ).

Etymology. The species is named after the French research vessel “ Alis ” that collected all the Papua New Guinea material.

Remarks. Oxypleurodon alisae n. sp., is characterized by its very long and fused pseudorostral spines. Five other species have similarly fused pseudorostral spines, viz. O. aurorae ( Alcock, 1899) from off Travancore coast in India, O. cuneus (Wood-Mason, in Wood-Mason & Alcock, 1891) from Andaman Sea, O. difficile ( Guinot & Richer de Forges, 1985) from Madagascar, O. parallelum Richer de Forges & Ng, 2009 , from the Solomon Islands, and O. pinocchio ( Guinot & Richer de Forges, 1985) from Makassar Strait.

In O. aurorae , O. cuneus , and O. difficile , the pseudorostral spines are fused along their entire length, becoming bifid only at their tips ( Guinot & Richer de Forges 1985: figs. 1A, B, 2A, B, 3A, B, pl. 1 figs. A, C, E, G, H; Richer de Forges 2010: fig. 1) while in O. alisae n. sp., it is only fused on the proximal one-third ( Figs. 1C , 2A ). Compared to O. alisae , the cardiac plate of O. aurorae is cordiform ( Guinot & Richer de Forges 1985: pl. 1 fig. C), more triangular on O. cuneus ( Guinot & Richer de Forges 1985: pl. 1 fig. A), and more rounded on O. difficile ( Guinot & Richer de Forges 1985: pl. 1 figs. E, G, H; Richer de Forges 2010: fig. 1); although all three species have the hepatic plate fused with the post-orbital plate ( Guinot & Richer de Forges 1985: pl. 1 figs. B, D, F). In O. alisae n. sp., the cardiac plate is more elongated horizontally and elliptical-shaped with irregular distal edges, and the hepatic and post-orbital plates are separate structures ( Figs. 1C , 2A, C ).

In O. parallelum , the pseudorostral spines are relatively shorter and thicker than in O. alisae n. sp. ( Richer de Forges & Ng 2009b: figs. 6A, 7C versus Figs. 1C , 2A ). In O. parallelum , the hepatic plate is completely fused with the post-ocular plate ( Richer de Forges & Ng 2009b: fig. 6A, 6C), whereas in O. alisae n. sp., they are separated ( Fig. 2B ). In O. alisae n. sp., the mesogastric plate is elongated and fusiform ( Figs. 1C , 2A ) while in O. parallelum , it is an ovoid elongate shape ( Richer de Forges & Ng 2009b: figs. 6A, 7C), and in O. pinnochio , it is wide, ovoid and elongate ( Guinot & Richer de Forges 1985: pl. 2 figs. A, C, E). The branchial plates have a similar sigmoid shape in these species but are distinctly thinner in O. alisae n. sp., with the lower indentation more pronounced ( Figs. 1C , 2A versus Richer de Forges & Ng 2009b: figs. 6A, 7C). In O. parallelum , the cardiac plate is ovate ( Richer de Forges & Ng 2009b: figs. 6A, 7C) rather than elliptical-shaped with irregular distal edges in O. alisae n. sp. ( Figs. 1C , 2A ). Lastly, the ambulatory legs are also proportionately shorter in O. parallelum than in O. alisae n. sp. ( Richer de Forges & Ng 2009b: fig. 7C versus Figs. 1C , 2A ).

In O. pinocchio , the pseudorostral spines are long, slender, and curved upwards, with a slightly bifid extremity ( Guinot & Richer de Forges 1985: figs. 4A–C, pl. 2), whereas in O. alisae n. sp., they are slender, straight, and fused only on the proximal third ( Figs. 1C , 2A ).

Oxypleurodon alisae n. sp. is currently only known from its type locality, Papua New Guinea.

Figures

FIGURE 1. Color in life. A, Griffinia takedai Richer de Forges & Ng, 2012, male (13.6 × 10.2 mm) (MNHN-IU-2013-3021), Papua New Guinea; B, Laubierinia carinata (Griffin & Tranter, 1986), male (24.7 × 16.0 mm) (MNHN-IU-2014-8128), Papua New Guinea; C, Oxypleurodon alisae n. sp., holotype, male (14.0 × 9.3 mm) (MNHN-IU-2015-227), Papua New Guinea; D, O. papuense n. sp., holotype, male (18.3 × 12.6 mm) (MNHN-IU-2015-228), Papua New Guinea; E, O. sp. 1, juvenile male (6.0 × 4.2 mm) (ZRC 2018.1478, ex. MNHN-IU-2017-11835), Papua New Guinea; F, Stegopleurodon planirostrum Richer de Forges & Ng, 2009, male (14.0 × 9.2 mm) (MNHN-IU-2015-64), Papua New Guinea.

FIGURE 2. Oxypleurodon alisae n. sp., holotype, male (14.0 × 9.3 mm) (MNHN-IU-2015-227), Papua New Guinea. A, overall dorsal view; B, overall ventral view; C, lateral view of carapace.

FIGURE 5. A–D, Oxypleurodon alisae n. sp., holotype, male (14.0 × 9.3 mm) (MNHN-IU-2015-227), Papua New Guinea, left G1. A, ventral view; B, ventral view of distal portion; C, dorsal view; D, dorsal view of distal portion. E–H, O. papuense n. sp., holotype, male (18.3 × 12.6 mm) (MNHN-IU-2015-228), Papua New Guinea, left G1. E, ventral view; F, ventral view of distal portion; G, dorsal view; H, dorsal view of distal portion.