Trapezioidea, 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 : 626-628

Key to families and subfamilies of Trapezioidea

1. Male pleonites 3–5 fused, immovable, even if some or all sutures visible ..........................................................................2

- Male pleonites and telson freely articulating .........................5

2. Cheliped merus usually with sharp spines or teeth on flexor margin. G2 shorter than half the length of G1 ........................ .......................................................................... 3 ( Trapeziidae )

– Cheliped merus unarmed. G2 three-quarters to as long as G1 ........................................................................... Calocarcinidae

3. Carapace subtrapezoid. Maxilliped 3 merus as wide as ischium (at midlength) ......................................................... Trapeziinae

– Carapace hexagonal or ovate. Maxilliped 3 merus narrower than ischium (at midlength) ....................................................4

4. Carapace hexagonal; dorsum flattened, gently convex in anterior view. P2–5 dactyli with transverse comb-like rows of setae on facial surfaces....................................................... Quadrellinae

– Carapace transversely ovate; dorsum distinctly convex. P2–5 dactyli with transverse comb-like rows of feeding setae on flexor margin only, absent from facial surfaces....................... ....................................................................... Sphenomeridinae

5. Carapace dorsal surface covered with small granules and spines; anterolateral margin with 2 or 3 teeth and additional acute granules or spinules. Cheliped propodus outer surface with prominent rounded or pointed tubercles ...... Domeciidae

– Carapace dorsal surface smooth; anterolateral margin behind outer orbital tooth unarmed or with sharp spine. Cheliped propodus smooth, outer surface without tubercles.................6

6. Carapace transversely ovate, widest near midlength; anterolateral margin with two teeth posterior to outer orbital tooth; front smooth, unarmed. Antennal peduncle entering orbital hiatus. Maxilliped 3 exopod reaching distally to distal edge of merus ................................................................ Ectaesthesiidae

– Carapace subtrapezoidal, widest anteriorly; anterolateral margin unarmed posterior to outer orbital tooth; front denticulate. Antennal peduncle excluded from orbit. Maxilliped 3 exopod reaching to two-thirds length of merus.................. Tetraliidae