Sphenomerides Rathbun, 1897

Ng, Peter K. L., Ahyong, Shane T. & Castro, Peter, 2023, Re-appraisal of the families and subfamilies of Trapezioidea Miers, 1886, with establishment of a new family, Ectaesthesiidae (Crustacea: Decapoda: Brachyura), Raffles Bulletin of Zoology 71, pp. 606-631 : 622

publication ID	https://doi.org/ 10.26107/RBZ-2023-0047
publication LSID	lsid:zoobank.org:pub:821BC4EC-5AF9-4727-84A3-C44839DFBE28
DOI	https://doi.org/10.5281/zenodo.10271581
persistent identifier	https://treatment.plazi.org/id/038EC92D-7962-7E4E-FEB9-6BC52687FAB2
treatment provided by	Felipe
scientific name	Sphenomerides Rathbun, 1897
status

Treatment

Sphenomerides Rathbun, 1897 View in CoL

Sphenomerus Wood-Mason View in CoL in Wood-Mason & Alcock, 1891: 263 (name pre-occupied by Sphenomerus Candèze, 1859 View in CoL [Coleoptera]); Alcock, 1898: 227.

Sphenomerides Rathbun, 1897: 164 View in CoL (replacement name for Sphenomerus Wood-Mason View in CoL in Wood-Mason & Alcock, 1891); Alcock, 1899: 65; Serène, 1973: 207, 1984: 289; Castro et al., 2004: 59 View Cited Treatment ; Ng et al., 2008: 185; Poore & Ahyong, 2023: 730, fig. 14.139g.

Type species. Sphenomerus trapezioides Wood-Mason View in CoL in Wood-Mason & Alcock, 1891, by monotypy; gender masculine).

Diagnosis. As for subfamily.

Remarks. As discussed earlier for Ectaesthesiidae , Sphenomerides is not included in Calocarcinidae mainly because its P2–5 dactylus possesses transverse comb-like rows of feeding setae, albeit restricted to the flexor margin only ( Fig. 12E, F View Fig ), features absent in Calocarcinus and Philippicarcinus . In addition, the posterior margin of the epistome is proportionally wider in Calocarcinus and Philippicarcinus than in Sphenomerides ( Figs. 5D View Fig vs Fig. 5C View Fig ), the maxilliped 3 merus is quadrate and wider than long, with the ischium rectangular ( Fig. 6E View Fig ) (merus longer than wide with the ischium trapezoidal in Sphenomerides ; Fig. 6D View Fig ), the flexor margin of the cheliped merus is smooth and unarmed (spinate in Sphenomerides ; Fig. 12A View Fig ), there is always a distinct suture separating thoracic sternites 2 and 3 ( Fig. 7F, G View Fig ) (no suture visible in Sphenomerides ; Fig. 7E View Fig ), male pleonal somite 2 is proportionally much broader than in Sphenomerides ; Fig. D, E); the sutures across male pleonal somites 3–5 are visible although they are immobile ( Fig. 8E View Fig ) (sutures conspicuously shallow to hardly visible in Sphenomerides ; Figs. 8D View Fig , 12D View Fig ), and the G2 is three-quarters to subequal to the length of the G1 with the basal portion elongated ( Fig. 9L, N View Fig ) (short, being only about one-quarter the length of the G 1 in Sphenomerides ; Fig. 9J View Fig ). Only one of the above features of Sphenomerides is different from typical trapeziids: the absence of suture between thoracic sternites 2 and 3 ( Fig. 7E View Fig ). This character, however, can also be observed in some species of Trapezia and Quadrella so it is not unique in the family. Sphenomerides is also unusual among trapeziids in its comparatively high carapace, with the dorsal surface prominently convex ( Fig. 12B View Fig ). All other confamilials are distinctly flatter. In most other aspects, including the relatively slender G1 and comparatively narrow maxilliped 3 merus, Sphenomerides is close to the quadrellines. However, the inflated carapace and unusual distribution of the P2–5 feeding setae, being present on the flexor margin but absent from the facial surfaces (present in other trapeziids) are considered sufficient to justify placing Sphenomerides in its own subfamily within Trapeziidae .