Tetraliidae Castro, Ahyong & Ng 2004
Creators: name: Ng, Peter K. L.
name: Ahyong, Shane T.
name: Castro, Peter
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Tetraliidae

description: Family Tetraliidae Castro, Ahyong & Ng, 2004  Tetraliidae Castro, Ahyong & Ng, 2004: 22.  
 Diagnosis. Carapace longitudinally subtrapezoidal to obpyriform, widest anteriorly (Fig. 1C, D); antero- and posterolateral margins gradually merging, anterolateral margin, unarmed behind external orbital tooth (Fig. 1C, D); front denticulate; posterolateral margin gently convex to almost straight (Fig. 1C, D); 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). 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). 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, 6G, H); propodus smooth, outer surface without tubercles. P2–5 very short, merus very stout, appearing foliaceous (Fig. 1C, D). Sternopleonal cavity reaching anteriorly to level of midlength of P2 coxae (Fig. 7A, B); 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, 8A). G1 relatively stout to slender, almost straight but gently sinuous in form; distal margins lined with fine setae or spinules (Fig. 9A, C). G2 relatively slender, short, one-third to one-half length of G1; distal portion spatuliform, tip tapering (Fig. 9B, D). 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).   
 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).
description: Published as part of 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), pp. 606-631 in Raffles Bulletin of Zoology 71 on page 618, DOI: 10.26107/RBZ-2023-0047, http://zenodo.org/record/10271307