Tetraliidae Castro, Ahyong & Ng, 2004

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

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.10271579
persistent identifier	https://treatment.plazi.org/id/038EC92D-797E-7E52-FF1A-6B25209DFBD2
treatment provided by	Felipe
scientific name	Tetraliidae Castro, Ahyong & Ng, 2004
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Family Tetraliidae Castro, Ahyong & Ng, 2004 View in CoL

Tetraliidae Castro, Ahyong & Ng, 2004: 22 View in CoL .

Diagnosis. Carapace longitudinally subtrapezoidal to obpyriform, widest anteriorly ( Fig. 1C, D View Fig ); antero- and posterolateral margins gradually merging, anterolateral margin, unarmed behind external orbital tooth ( Fig. 1C, D View Fig ); front denticulate; posterolateral margin gently convex to almost straight ( Fig. 1C, D View Fig ); carapace relatively low, dorsal surface gently convex in frontal view; posterior margin of epistome with median lobe small, lateral margin wide, gently concave, almost entire, with small triangular lobe just before pterygostomial lobe ( Fig. 5A View Fig ). Maxilliped 3 merus almost round, anteroexternal part not auriculiform, as wide as elongate, subrectangular ischium; distal edge of exopod reaching to two-thirds length of merus ( Fig. 6A View Fig ). Basal antennal article mobile, rhomboid, expanded laterally to exclude peduncle excluded from orbit. Chelipeds long, distinctly heterochelous, major cheliped about twice carapace width or slightly shorter, merus quadrate in dorsal view, short, with sharp spines or teeth on flexor margin, extensor margin smooth; carpus inner angle rounded, unarmed ( Figs. 1C, D View Fig , 6G, H View Fig ); propodus smooth, outer surface without tubercles. P2–5 very short, merus very stout, appearing foliaceous ( Fig. 1C, D View Fig ). Sternopleonal cavity reaching anteriorly to level of midlength of P2 coxae ( Fig. 7A, B View Fig ); tubercle of male pleonal-locking mechanism small, on posterior edge of thoracic sternite 5, near suture with sternite 6. Male pleon transversely relatively wide, triangular, lateral margins of somites 3–6 gently converging, all somites and telson free ( Figs. 7A, B View Fig , 8A View Fig ). G1 relatively stout to slender, almost straight but gently sinuous in form; distal margins lined with fine setae or spinules ( Fig. 9A, C View Fig ). G2 relatively slender, short, one-third to one-half length of G1; distal portion spatuliform, tip tapering ( Fig. 9B, D View Fig ). Vulva simple, flat, lunate to subcircular, positioned on submedian part of sternite 6, positioned relatively far apart, with lateral, flexible sternal vulvar cover ( Fig. 10A, B View Fig ).

Genera included. Tetralia Dana, 1851a and Tetraloides Galil, 1986b .

Remarks. The two tetraliid genera are well defined, but the taxonomy of the species included in each genus is challenging because there are probably several species complexes contained therein. Colour pattern and genetics appear to be the most reliable differentiators for tetraliid species; other taxonomically reliable morphological characters are yet to be found. Both tetraliid genera are obligate symbionts of zooxanthellate (hermatypic) scleractinian corals of the genus Acropora Oken, 1815 ( Acroporidae ) ( Castro, 2015).