Trapeziidae Miers, 1886

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 : 618-620

publication ID	https://doi.org/ 10.26107/RBZ-2023-0047
publication LSID	lsid:zoobank.org:pub:821BC4EC-5AF9-4727-84A3-C44839DFBE28
persistent identifier	https://treatment.plazi.org/id/038EC92D-797E-7E50-FC0E-6AC527DEFC52
treatment provided by	Felipe
scientific name	Trapeziidae Miers, 1886
status

Treatment

Family Trapeziidae Miers, 1886 View in CoL

Trapeziinae Miers, 1886: 163 View in CoL (in part).

Diagnosis. Carapace trapezoidal (widest anteriorly) to hexagonal, transversely ovate; front entire to lobate and spinate; posterolateral margin gently concave to gently convex ( Figs. 11A, B View Fig , 12A, C View Fig ); carapace relatively low or high, dorsal surface gently or prominently convex in frontal view ( Figs. 11A, B View Fig , 12A, B View Fig ); posterior margin of epistome with distinct median lobe, lateral margin relatively short, gently concave, with 2 triangular lobes ( Figs. 5B, C View Fig , 11C View Fig ). Maxilliped 3 merus with anteroexternal corner not auriculiform; distal edge of exopod reaching to distal edge of merus ( Fig. 6B–D View Fig ). Chelipeds long to very long, heterochelous to homochelous, larger cheliped length about twice carapace width or greater; merus with sharp spines or teeth on flexor margin (except Hexagonaloides , unarmed), extensor margin smooth; carpus inner angle with or without tooth or spine ( Figs. 11A, B View Fig , 12A View Fig ). P2–5 merus unarmed; dactylus flexor margin with 3–5 transverse, comb-like rows of feeding setae ( Figs. 11A, B, D View Fig , 12A, E, F View Fig ); propodus smooth, outer surface without tubercles. Male thoracic sternum wide or elongated, sternopleonal cavity reaching anteriorly to midlength or anterior margin of P2 coxae or anterior margin of cheliped coxae ( Fig. 7C–E View Fig ); tubercle of male pleonal-locking mechanism small or distinct, on posterior edge or anterior one-third of thoracic sternite 5, may be near suture with sternite 6 ( Fig. 8H–J View Fig ). Male thoracic sternites 1–4 fused, with only lateral part of suture visible; suture between sternites 2, 3 usually visible, sometimes indistinct to absent or merely indicated by change in contour ( Fig. 7C–E View Fig ). Male pleon relatively wide or narrow or triangular; somites 3–5 fused, immovable, with sutures shallow to undiscernible ( Figs. 7C–E View Fig , 8B–D View Fig ). G1 almost straight to gently sinuous ( Fig. 9E–I View Fig ). G2 relatively slender, short, one-quarter to one-third length of G1; distal portion spatuliform, tip tapering ( Fig. 9F, H, J View Fig ). Vulva round to ovate; with flat lateral flexible sternal vulvar cover ( Fig. 10C View Fig ) or with hard lateral sternal cover arching over narrow membrane-covered opening ( Fig. 10D, E View Fig ).

Remarks. Ng et al. (2008) recognised three subfamilies in Trapeziidae : Calocarcininae, Quadrellinae , and Trapeziinae . Calocarcininae is elevated herein as a separate family, Calocarcinidae , new status (see below). We also recognise a separate subfamily, Sphenomeridinae Števčić, 2005 , new status, for Sphenomerides . Philippicarcinini Števčić, 2011, was subsequently recognised as another tribe in Trapeziidae by Števčić (2011), but is here regarded as a junior subjective synonym of Calocarcinidae Števčić, 2005 .

All trapeziids are obligate symbionts of zooxanthellate (hermatypic) and azooxanthellate (ahermatypic) scleractinian corals, colonial cnidarians and sponges ( Castro, 2013, 2015).