Tetriasidae, Tsang & Naruse, 2023

Tsang, Ling Ming & Naruse, Tohru, 2023, Recognition of Parapinnixidae Števčić, 2005, and Tetriasidae fam. nov. in Pinnotheroidea De Haan, 1833 (Crustacea: Brachyura: Thoracotremata), Zootaxa 5249 (5), pp. 540-558 : 545-548

publication ID	https://doi.org/ 10.11646/zootaxa.5249.5.2
publication LSID	lsid:zoobank.org:pub:949F2D17-F10C-4ED1-9580-2CB12BD65896
DOI	https://doi.org/10.5281/zenodo.7704175
persistent identifier	https://treatment.plazi.org/id/03CD233F-473E-745A-FF22-C5F9FB44E657
treatment provided by	Plazi
scientific name	Tetriasidae
status	fam. nov.

Treatment

Family Tetriasidae View in CoL fam. nov.

Diagnosis. Carapace ( Fig. 2 View FIGURE 2 ) rectangular to subtriangular, wider than long in both sexes, female carapace wider than that of male, dorsally convex longitudinally and transversely; regions clearly defined by grooves; front and buccal cavern proportionally wide, especially species with wider carapace ( Figs. 2 View FIGURE 2 , 3A View FIGURE 3 , 4A View FIGURE 4 ). Epistome wide transversely, buccal cavern semicircular, large ( Figs. 3A, B View FIGURE 3 , 4 View FIGURE 4 ). Antennal article 1 oval, placed anterior to lateral part of epistome, posteromesial part of article 1 minutely protruding onto epistome posterior margin ( Fig 4 View FIGURE 4 ). Mxp3 ( Fig. 3 View FIGURE 3 ) longitudinally placed in buccal cavern ( Fig. 3A, B View FIGURE 3 ). Maxilliped 3 ischium and merus fused but demarcated by superficial suture, merus produced mesio-subdistally; palp 3-segmented, each article about two-thirds length of merus; carpus length as long as distal width of merus, semi-triangular, attached to distolateral corner of merus; propodus widened distally; dactylus inserted at distolateral corner (in situ) of propodus, subrectangular. Exopod wide, subrectangular, distolateral corner concave, flagellum distinct. Ambulatory legs ( Fig. 2 View FIGURE 2 ) bilaterally symmetrical, stout to slender, length P3>P2>P4>>P5. Male pleonal somite and telson free, pleonal somites narrow horizontally, especially somites 4–6, telson ( Fig. 3B View FIGURE 3 ) much wider, distally reaching suture between mxp3 ischium and merus when closed. G1 simple, slender, slightly curved distally. G2 small. Female pleon and telson free, covering most of thoracic sternum and distally entering buccal cavern in large female.

Type genus. Tetrias Rathbun, 1898 View in CoL , by present designation and monotypy.

Etymology. Rathbun (1898) did not provide an etymology of the type genus Tetrias . It is probably derived from the Latin word “Tetris”, an adjective derived from the word “teter”, which means ugly and not beautiful. It may also be from the Greek word “ Tetrix ”, which refers to a grouse (a compact dull-brown well camouflaged bird), and the name is used for a genus of family Tetrigidae (grasshopper). Considering ICZN Articles 29.3.3, 29.6 and Recommendation 29A, the entire genus name “ Tetrias ” is used as the stem of the family name Tetriasidae .

Remarks. Members of Tetriasidae fam. nov. are characterized by their setose appearance, rectangular to subtriangular and high carapace, and dorsal surface regions of the carapace being clearly demarcated by grooves in both sexes ( Fig. 2 View FIGURE 2 ; A. Milne-Edwards 1873: pl. 18, fig. 3; Rathbun 1898: pl. 43, fig. 12). Tetriasidae fam. nov. is distinct from other pinnotheroid families in its large mxp3 palp articles: the dactylus is enlarged, the carpus, propodus and dactylus are each about two-thirds length of the merus, and the dactylus is inserted at the distolateral corner of the propodus (in situ) ( Fig. 3 View FIGURE 3 ; Rathbun 1898: pl. 43, fig. 13). Most members of Pinnotheridae sensu stricto with 3-segmented mxp3 palps have the dactylus slender to narrowly spatulate and inserted subdistally on the lower margin of the propodus, for example, the pinnotherine Pinnotheres pisum ( Linnaeus, 1767) (Becker & Türkay 2010: fig. 5C), the pinnixine Pinnixa cylindrica (Say, 1818) ( Rathbun 1918: 160 fig. 99a), and the pinnixulaline Pinnixuala valerii ( Rathbun, 1931) ( Palacios Theil et al. 2016: fig. 9d) (also see Manning 1993; Ahyong & Ng 2007; Ahyong 2018; Ng & Ahyong 2022). The mxp3 dactylus of some pinnotherid species is either inserted at the distal end of the propodus or relatively enlarged ( Table 1 View TABLE 1 ), but none of them simultaneously possess both character states. The pinnotherine Pinnaxoides chilensis (H. Milne Edwards, 1837) has a superficially similar mxp3 condition to tetriasids but is still markedly different because the distomesial corner of the propodus is produced ( Rathbun 1898: pl. 43, fig. 10, as P. hirtipes ; Garth 1957: fig. 9D; Takeda & Prince Masahito 2000: fig. 2C; Ng & Manning 2003: fig. 7A, B; Campos 2017: fig. 3d–f).

Tetriasidae fam. nov. also differs from the two pinnotheroid families in its unique combination of characters: the presence of a superficial suture between mxp3 ischium and merus ( Fig. 3D View FIGURE 3 ; Rathbun 1898: pl. 43, fig. 13) (versus absent in pinnotherine pinnotherids, except for some species of Pinnaxodes , such as P. chilensis (H. Milne Edwards, 1837) ( Campos 2017) , P. floridensis Wells & Wells, 1961 ( Wells & Wells 1961: fig. 2F, G), and P. gigas Green, 1992 ( Green 1992: fig. 3F)); and the proportionally wider front, hence horizontally wider buccal cavern and widely separated eyes ( Fig. 3A; A View FIGURE 3 . Milne-Edwards 1873: pl. 18, fig. 3; Rathbun 1898: pl. 43, fig. 12; 1918: pl. 39, fig. 4, 5) (versus narrow in Parapinnixidae ( Fig. 5A View FIGURE 5 , also see remarks of Parapinnixidae ) and pinnotherine pinnixines, such as Pinnixa cylindrica (Say, 1818) ( Rathbun 1918: pl. 35, figs. 5–8)).

Tetriasidae fam. nov. is currently known by one genus and two species: Tetrias fischerii (A. Milne-Edwards, 1867) and T. scabripes Rathbun, 1898 ( Ng et al. 2008). An ongoing revision of the genus will recognise more species of Tetrias from the Indo-West Pacific (T. Naruse, T. Komai and P. K. L. Ng, in preparation).