Calliax nishiki, Ando & Kawano & Muramiya & Niiyama & Kameyama & Shimoyama, 2020

Ando, Yusuke, Kawano, Shigenori, Muramiya, Yusuke, Niiyama, Sota, Kameyama, Sohiko & Shimoyama, Shoichi, 2020, Fossil decapods from the Upper Quaternary in Shinjima Island in Kagoshima Kyushu, Japan, and description of a new species of ghost shrimp (Axiidea Eucalliacidae), Zootaxa 4878 (3), pp. 523-541 : 527-530

Calliax nishiki sp. nov.

[New Japanese name: Nishiki-suna-moguri]

( Figs. 3, 4)

urn:lsid:zoobank.org:act:93ECF222-E117-43E9-8330-755E841C2983

Material examined. MFM142024 (holotype: P1 chela) , MFM142025 (paratype: P1 chela) , MFM142026 (paratype: P1 chela) , MFM142027 (paratype: P1 chela) , MFM142028 (paratype: P1 chela) , MFM142029 (paratype: P1 chela) , MFM142030 (paratype: P1 chela) , MFM142031 (paratype: P1 dactylus) , MFM142032 (paratype: P1 dactylus) , MFM142033 (paratype: P1 dactylus) , MFM142034 (paratype: P1 carpus) , MFM142035 (paratype: P1 carpus) , MFM142036 (paratype: P1 carpus) , MFM142037 (paratype: P1 carpus, merus, ischium) , MFM142038 (paratype: P1 merus) , MFM142039 (paratype: P1 merus) , MFM142040 (paratype: P1 merus) , MFM142041 (paratype: P1 ischium) , MFM142042 (paratype: P1 ischium) and 112 referred specimens .

Etymology. The name is derived from “Nishiki”, a Japanese word meaning beautiful, because of the fine preservations of the present specimens.

Type locality. Loc. 2-1, Moeshima Silt Bed in Shinjima Island , Kagoshima City, Kagoshima Prefecture, Japan. Holocene .

Measurements. See Table 2.

Diagnosis. Moderately sized axioid. Ischium of pereiopod 1 (P1) long, slender. Merus of P1 2.5 times longer than high; lower margin covered with small tubercles; posterior part of lower margin bearing 3–5 slender, sharp, slightly curved spines. Carpus of P1 1.3 times higher than long; proximo-upper margin concave; lower margin well curved without tubercles. Palm of Pl subrectangular, 2.2 times longer than tall; lateral outer surface of anterior margin (1/3 of palm height) armed with a slender keel-like ridge extending to half-length of dorsal border of fixed finger; base of ridge bearing 1–3 tubercles; outer surface of anterior part of proximo-lower margin with 10–15 small tubercles; lower margin keeled, slightly curved anteriorly. Fixed finger of P1 approximately 30 percent of length of palm, triangular, elongate, strongly curved dorsally and inner laterally with acutely pointed tip; occlusal margin armed with 2–3 molar-like triangular teeth. Dactylus of P1 as long as fixed finger, triangular, elongate, strongly curved dorsally and inner laterally with acutely pointed tip; occlusal margin bearing 8–10 small, rounded denticles.

Description. Moderately sized axioid. Ischium of pereiopod 1 (P1) long, slender; upper margin unarmed; lower margin bearing 10–15 small rounded spines. Merus of P1 2.5 times longer than tall; upper margin slightly sinuous; lateral outer surface with one ridge which is slightly sinuous; lower margin covered with 20–40 small tubercles along its length; posterior part of lower margin bearing 3–5 slender, sharp, slightly curved spines. Carpus of P1 as long as merus, 1.3 times higher than long; upper margin slightly curved, unarmed; proximo-upper margin concave; proximo-lower margin rounded, strongly curved and smooth its outline; lower margin well-curved without tubercles. Palm of Pl subrectangular, about 2.5 times longer than carpus, 2.2 times longer than high; upper margin slightly curved, converging distally, unarmed; outer surface of upper margin smooth; lateral outer surface of anterior margin (1/3 of palm height) armed with slender keel-like ridge extending to half-length of dorsal border of fixed finger; base of ridge bearing 1–3 tubercles; outer surface of anterior part of proximo-lower margin with 10–15 small tubercles; lower margin keeled, slightly curved anteriorly. Fixed finger of P1 approximately 30 percent of length of palm, triangular, elongate, strongly curved dorsally and inner laterally with acutely pointed tip; near base of fixed finger swollen; occlusal margin armed with 2–3 molar-like triangular teeth; lateral inner surface armed with one ridge along base to middle of fixed finger; base of inner ridge also bearing 1–3 tubercles; anterior part of inner surface with one low, short ridge; lower margin curved, unarmed. Dactylus of P1 as long as fixed finger, triangular, elongate, strongly curved dorsally and inner laterally with acutely pointed tip; upper margin well-curved; lateral outer surface smooth; lateral inner surface armed with ridge along its length; occlusal margin bearing 8–10 low rounded denticles.

Remarks. The present species is closest to extant Calliax lobata (de Gaillande & Langardère, 1966) , first described from southern France (Mediterranean). However, the latter species has seven blunt spines on the lower margin of the merus, single molar-like triangular teeth on the occlusal margin of the fixed finger and an absence of tubercles on the lateral surface of the palm. The new species is similar to extant Calliax doerjesti Sakai, 1999 , described from the USA, but differs in having 3–5 spines on the lower margin of the merus, a longer carpus with more rounded proximo-lower margin and 2–3 molar-like, triangular teeth on the occlusal margin of the fixed finger. The present species also resembles Calliax michelottii (A. Milne-Edwards, 1860) first described from the Miocene of Italy ( Hyžný & Gašparič 2014), but differs in having 3–5 spines on the lower margin of the merus, only one ridge on the lateral surface of base of fixed finger and a longer palm.

García Raso et al. (2019) reported extant Calliax lobata from the bathyal bottom of a reducing environment, and Taviani et al. (2013) collected many unnamed specimens of Calliax from the Holocene deposits, which were formed under the bathyal bottom within a similar setting. Moreover, Hyžný & Gašparič (2014) showed that many specimens identified with Calliax michelottii were collected from Oligocene to Miocene deposits formed at bathyal depths. Therefore, the present new Calliax might also be abundant in deep, marine, reducing environments. Indeed, this genus seems to mainly occur in reducing environments deeper than the sublittoral zone.