Re-appraisal of the families and subfamilies of Trapezioidea Miers, 1886, with establishment of a new family, Ectaesthesiidae (Crustacea: Decapoda: Brachyura) Author Ng, Peter K. L. Author Ahyong, Shane T. Author Castro, Peter text Raffles Bulletin of Zoology 2023 2023-10-30 71 606 631 journal article 10.26107/RBZ-2023-0047 2345-7600 10271307 821BC4EC-5AF9-4727-84A3-C44839DFBE28 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 Fig. 12. Sphenomerides trapezioides , male (7.8 × 5.9 mm) (ZRC 2000.2103), Madagascar. A, Dorsal habitus; B, frontal view of cephalothorax; C, dorsal view of carapace; D, male pleonal somites 3–6 (ventral view) showing fusion between somites 3–5; E, left P4 dactylus and propodus; F, comb-like setal rows on left P4 dactylus. 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