Scyramathia A. Milne-Edwards, 1880

Lee, Bee Yan, Richer De Forges, Bertrand & Ng, Peter K. L., 2020, Revision of the deep-water spider crab genus, Scyramathia A. Milne-Edwards, 1880, with the description of a new species from the Mediterranean and notes on Rochinia A. Milne-Edwards, 1875, and Anamathia Smith, 1885 (Crustacea, Decapoda, Brachyura, Epialtidae), Zoosystematics and Evolution 96 (2), pp. 537-569 : 537

Genus Scyramathia A. Milne-Edwards, 1880

Scyramathia A. Milne-Edwards 1880a: 356; A. Milne-Edwards 1880b: 277; Sars 1885: 5, 6; Smith 1886: 625[21]; A. Milne-Edwards and Bouvier 1894: 12, 13; Alcock 1895: 201; A. Milne-Edwards and Bouvier 1900: 131; Rathbun 1901: 61; Stebbing 1902: 5; Doflein 1904: 80, 81; Stebbing 1905: 25; Stebbing 1910: 289; A. Milne-Edwards and Bouvier 1923: 379; Barnard 1950: 48 (key), 49; Tavares 1991: 161, 162; Tavares and Santana 2018: 204, 208.

? Scyramathia : Alcock 1895: 165 (list).

Type species.

Amathia carpenteri Norman, in Thomson 1873, subsequent designation by Rathbun 1925; gender feminine.

Diagnosis.

Carapace pyriform, with strong raised plate-like structures in large adult specimens (Figs 3 , 4A , 5A , 7A, C , 9A-I , 10A , 11A , 12 , 13A ); weak plates on smaller specimens (see Tavares et al. 2015: Fig. 1A-C ). Pseudorostral spines long, slender, diverging at approximately 45° angle or less. Supraorbital eave truncated with sharp preorbital angle; strong postorbital lobe fused with hepatic spine, round anterior margin (Figs 3 , 4A , 5A , 7A, C , 9A-I , 10A , 11A , 12 , 13A ). Mesogastric and cardiac regions with plates; long lateral branchial spine pointing outwards, more plate-like in large specimens (usually exceeding 20 mm carapace width) (Figs 3 , 4A , 5A , 7A , 9A-I , 10A , 11A , 12 , 13A ). Antennal flagellum short, about half pseudorostral spine length. Basal antennal article longer than broad, with straight to gently convex outer margin. Distal angle of buccal frame blunt, slightly raised. Pterygostomial region with large, flattened granules on outer margin (Figs 4B , 5B , 6C , 7B, D , 10B , 11B, E , 13B ). Chelipeds slender with slight carinate margins; propodus slender, longer than fingers; carpus with carinate margins; merus triangular in cross-section with carinate margins. Ambulatory legs long with cylindrical articles, rounded margins; merus with blunt distal angle; P2 longest (Figs 3 , 4A , 5A , 10A , 11A , 12 , 13A ). Male thoracic sternum transversely broad, deeply groove; sternites 3, 4 relatively wide with slightly constricted lateral margin. Male pleon rectangular, telson triangular; surface of somites smooth (Figs 4B , 5B , 6D, F , 10B , 11B, E , 13B ). G1 straight, distal part elongated, with sharp angle at tip (Figs 8C-F , 15A-H ); G2 with wide distal tip forming C-shape lateral margin (Fig. 8G, H ).

Remarks.

When establishing Scyramathia A. Milne-Edwards, 1880, A. Milne-Edwards (1880a: 356) transferred Scyra umbonata Stimpson, 1871, and Amathia carpenteri Norman, in Thomson 1873, to it, commenting that both species do not belong to the genus they were described in: "Je ferai remarquer que l’ Amathia Carpenteri n’appartient pas au genre Amathia et que la prétendue Scyra umbonata n’est certainement pas une Scyra " [I will point out that Amathia carpenteri does not belong to the Amathia genus and that alleged Scyra umbonata is certainly not Scyra ]. He did not elaborate on the reasons why the two genera were different, nor did he compare it to Rochinia A. Milne-Edwards, 1875, which he described only seven years earlier. There were no distinguishing or diagnostic morphological characters provided for Scyramathia A. Milne-Edwards, 1880. No type species for the genus was proposed, Rathbun (1925) subsequently selected Amathia carpenteri Norman, in Thomson 1873, as the type species for Scyramathia .

Scyramathia carpenteri (Norman, in Thomson 1873) was described in Amathia Roux, 1828, but this genus name is preoccupied by Amathia Lamouroux, 1812 ( Bryozoa), and as such, a new name Anamathia , was proposed by Smith (1885). Alcock (1895: 201) re-described Scyramathia as he understood it and remarked that it is distinct from Anamathia , with more affinities to Hyastenus White, 1847, and Pugettia Dana, 1851. Alcock (1895), however, had based his understanding of Scyramathia on the Indo-West Pacific species. In selecting S. carpenteri (Norman, in Thomson 1873) as the type species of Scyramathia , Rathbun (1925) also synonymised it under Rochinia , but without any explanation. Although Garth (1958: 283) listed Scyramathia A. Milne-Edwards, 1880, and Anamathia Smith, 1885, in the synonymy of Rochinia , he commented that the genus is not monophyletic due to the varying forms of the G1. Scyramathia has nevertheless remained under the synonymy of Rochinia since. Serène and Lohavanijaya (1973: 55) discussed the history of Rochinia , and noted that some authors (e.g. Barnard 1950) still considered Scyramathia a valid genus.

The species in Scyramathia s. str. have characteristic carapace plates that become more pronounced and lamelliform with age (see Tavares et al. 2016; Tavares and Santana 2018). Our studies confirm the findings of Tavares and Santana (2018). Tavares and Santana (2018) noted that Scyramathia includes the following species: S. carpenteri Norman, in Thompson, 1873, S. umbonata Stimpson, 1871, and a fossil species, S. boschii ( Casadío, Feldmann, Parras & Schweitzer, 2005) (see Casadío et al. 2005). Tavares and Santana (2018), however, retained one species, Scyramathia hertwigi Doflein, in Chun 1900, from Africa in Rochinia sensu lato. It is clearly a Scyramathia species (present study).

Scyramathia s. str. is herein re-defined. With the transfer of S. hertwigi , as well as the description of a new species, S. tenuipes sp. nov., from the Mediterranean Sea, there are now four extant species and one fossil species in this genus.

Figures

Figure 1. Rochinia gracilipes A. Milne-Edwards, 1875, paralectotype male [dry] (20.0 x 15.0 mm) (MNHN-IU- 2000 - 4460 [= MNHN-B 4460]), Cap. Corrientes. A. overall dorsal view; B. overall ventral view; C. lateral view of carapace.

Figure 3. Illustration of Scyramathia carpenteri (Norman, in Thomson 1873), " sandy chalk of Holtenia ground ", overall dorsal view. (After Norman, in Thomson 1873: fig. 35).

Figure 4. Scyramathia carpenteri (Norman, in Thomson 1873), lectotype male (21.6 x 15.9 mm) (NHM 1907.8.28.3), " Holtenia ground " (= between north Scotland and the Faeroe Islands). A. overall dorsal view; B. overall ventral view; C. lateral view of carapace.

Figure 5. Scyramathia carpenteri (Norman, in Thomson 1873), male (41.3 x 34.0 mm) (NHM 1983.449), North Sea. A. overall dorsal view; B. overall ventral view; C. lateral view of carapace.

Figure 6. A. Scyramathia carpenteri (Norman, in Thomson 1873), male (35.0 x 27.1 mm) (NHM 1981.108), North Sea; B-F. S. carpenteri (Norman, in Thomson 1873), male (41.3 x 34.0 mm) (NHM 1983.449), North Sea. A, B. lateral view of carapace; C. ventral frontal surface of carapace; D. male thoracic sternum view; E. dorsal surface of male left chela; F. posterior ventral view of male pleon.

Figure 7. Illustration of Scyramathia carpenteri (Norman, in Thomson 1873). A, B. lectotype male (21.6 x 15.9 mm) (NHM 1907.8.28.3), " Holtenia ground " (= between north Scotland and the Faeroe Islands); C, D. paralectotype female (13.0 x 8.4 mm) (NHM 1911.11.8.377), same locality as lectotype. A, C. dorsal view of carapace; B, D. ventral frontal surface of carapace.

Figure 8. Illustration of Scyramathia carpenteri (Norman, in Thomson 1873). A, C-H. lectotype male (21.6 x 15.9 mm) (NHM 1907.8.28.3), " Holtenia ground " (= between north Scotland and the Faeroe Islands); B. paralectotype female (13.0 x 8.4 mm) (NHM 1911.11.8.377), same locality as lectotype. A, B. lateral view of carapace; C. ventral view of G 1; D. ventral view of distal portion of G 1; E. dorsal view of G 1; F. dorsal view of distal portion of G 1; G. ventral view of G 1; H. dorsal view of G 2. Scale bars: 1 mm.

Figure 9. Variation of plate-like structures on carapace on Scyramathia carpenteri (Norman, in Thomson 1873). A. lectotype male (21.6 x 15.9 mm) (NHM 1907.8.28.3), " Holtenia ground "; B, G. female (22.4 x 17.2 mm, 35.8 x 29.0 mm, respectively) (NHM 1978.99), North Sea; C. male (41.3 x 34.0 mm) (NHM 1983.449), North Sea; D, E, H, I. male (28.2 x 22.7 mm, 37.1 x 30.5 mm, 24.6 x 17.2 mm, 33.0 x 25.7 mm, respectively) (NHM 1978.99), North Sea; F. male (35.0 x 27.1 mm) (NHM 1981.108), North Sea.

Figure 10. Scyramathia hertwigi Doflein, in Chun 1900, lectotype male (33.7 x 27.0 mm) (ZMB 13699), South Atlantic Ocean. A. overall dorsal view; B. overall ventral view; C. lateral view of carapace.

Figure 11. A-C. Scyramathia umbonata (Stimpson, 1871), female (36.7 x 27.9 mm) (NSMT-Cr 7178), off Suriname; D-F. Rochinia confusa Tavares, 1991, paratype male (8.0 x 5.2 mm) (MNHN-IU- 2014 - 19836 [= MNHN-B 24570]), Brazil. A, C. overall dorsal view; B, E. overall ventral view; C, F. lateral view of carapace.

Figure 12. Colour in life of Scyramathia tenuipes sp. nov., holotype male (33.9 x 26.3 mm) (ICMD 288), Mediterranean Sea (Credits: MacPherson E & Abello P).

Figure 13. Scyramathia tenuipes sp. nov., holotype male (33.9 x 26.3 mm) (ICMD 288), Mediterranean Sea. A. overall dorsal view; B. overall ventral view; C. lateral view of carapace.

Figure 15. A-D. Scyramathia hertwigi Doflein, in Chun 1900, paralectotype male (24.7 x 19.0 mm) (ZMB 13700), Agulhasstrom [= Agulhas current], left G 1; E-H. Scyramathia tenuipes sp. nov., holotype male (33.9 x 26.3 mm) (ICMD 288), Mediterranean Sea, left G 1. A, E. ventral view; B, F. ventral view of distal portion; C, G. dorsal view; D, H. dorsal view of distal portion. Scale bars: 1 mm.