Chirostylidae Ortmann, 1892

Baba, Keiji, Ahyong, Shane T. & Schnabel, Kareen E., 2018, Rediagnosis of the squat lobster genus Gastroptychus Caullery, 1896, with a new genus Sternostylus and a new family Sternostylidae (Crustacea: Decapoda: Anomura: Chirostyloidea), Zootaxa 4524 (1), pp. 77-86 : 78-79

Family Chirostylidae Ortmann, 1892

Chirostylidae Ortmann, 1892: 246 (part); 1898: 1149 (part).—van Dam, 1933: 2 (part).— Barnard, 1950: 495 (part).— Balss,

1957: 1594 (part).— Davie, 2002: 29 (part).— Poore, 2004: 220 (part).— Baba et al., 2009: 7 (part).—Schnabel & Ahyong,

2010: 58 (part).— Macpherson & Baba, 2011: 48 (part). Diptycinés Milne Edwards & Bouvier, 1894: 296, 312 (part); 1897: 116 (part). Diptychinae—Bouvier, 1896: 312 (part).— Milne Edwards & Bouvier, 1897: 116 (part). Uroptychidae Alcock, 1901: 236, 278 (part).

Type genus. Chirostylus Ortmann, 1892 .

Diagnosis. Carapace without transverse setiferous striae. Rostrum triangular, spiniform or strongly reduced, supraocular spines absent. Sternal plastron, at sternite 3, abruptly demarcated from preceding sternites (excavated sternum) by distinct step forming well-defined transverse or concave anterior margin at articulation with maxillipeds 3, and placing excavated sternum on lower plane (when viewed from ventral side). Abdominal somite 2 without anterolaterally produced spine on pleuron. Tailfan folded beneath preceding abdominal somite, telson divided into anterior and posterior lobes. Eyes well developed. Antennal scale present or absent. Maxilliped 1 without epipod; exopod flagellum smooth and non-annulated or absent. Maxillipeds 3 widely separated, with distal parts accommodated in excavated sternum between left and right maxillipeds 3 when folded. Pereopods 2–4 dactyli with terminal spine (unguis) clearly demarcated by suture, often slightly movable. Maxilliped 3 to pereopod 4 each with 2 arthrobranchs; pereopod 5 with 1 arthrobranch; pereopods 2–4 with 1 pleurobranch. Male pleopods 1 and 2 present.

Genera included. Chirostylus Ortmann, 1892 ; Gastroptychus Caullery, 1896 ; Hapaloptyx Stebbing, 1920 ; Heteroptychus Baba, 2018 ; Uroptychodes Baba, 2004 ; Uroptychus Henderson, 1888 .

Remarks. The sternal plastron and maxillipeds 3 are shown for species of Chirostylus , Gastroptychus , Heteroptychus , Uroptychodes and Uroptychus (Fig. 1A–E). The only known specimen of Hapaloptyx , H. difficilis Stebbing, 1920 , could not be examined; the illustrations presented by Stebbing (1920) are not detailed but appear to represent Chirostylidae sensu stricto. However, the systematic status of this genus remains to be determined by reexamination of type material (Baba et al. 2008; Schnabel & Ahyong 2010).

The genus Uroptychus remains highly speciose, currently containing 255 species worldwide, and displays such varied morphology that it may be best divided into several genera ( Baba 2018). For example, molecular analyses placed U. scambus apparently in a different clade within the Chirostylidae ( Schnabel et al. 2011; Roterman et al. 2013; Bracken-Grissom et al. 2013). This species, together with eight related species, including six new species, were transferred to Heteroptychus Baba, 2018 . A number of other groups of species require a review, for example, Uroptychus spinirostris ( Ahyong & Poore, 2004) , belongs to a group in the genus with a spinose body and pereopods very much like those of Gastroptychus , and is genetically remote from the other groups of Uroptychus and Heteroptychus (see Bracken-Grissom et al. 2013). This group includes U. chacei ( Baba, 1986a) , U. ciliatus (van Dam, 1933) , U. numerosus Baba, 2018 , U. quartanus Baba, 2018 , U. senarius Baba, 2018 , and U. spinimanus Tirmizi, 1964 . The following species or species groups require revision at a higher taxonomic level: two groups each centered around Uroptychus scandens Benedict, 1902 and U. naso van Dam, 1933 , respectively, as well as U. ctenodes Baba, 2018 , U. diaphorus Baba, 2018 , U. inaequalis Baba, 2018 and related species ( Baba 2018).