Takedactylus Naruse and Maenosono, 2012

Genus Takedactylus Naruse and Maenosono, 2012 View in CoL

Takedactylus masatsunei Naruse and Maenosono, 2012 View in CoL [Jn: Takeda-koyubi-pinno]

( Fig. 2 View Fig )

Takedactylus masatsunei Naruse & Maenosono, 2012, p. 227 View in CoL , figs. 1–2.

Material examined. ɹ Chichi-jima Is. —Ototo-jima I., 1 juv. (cb 3.3×cl 2.2 mm), NSMT-Cr 32392, 10-VII-1969, coll. by M. Imajima.

Remarks. ɹ This small species has hitherto been known only by the holotype female (cb 2.9 by cl 1.8 mm) from Sesoko Island adjacent to Okinawa Island, Ryukyu Islands. The present juvenile ( Fig. 2 View Fig ) from Ototo-jima Island is almost same size with the holotype, agreeing very well with the description, photographs and line drawings of the holotype.

The carapace ( Fig. 2A View Fig ) is laterally rectangular in outline, fairly strongly convex longitudinally and flattened laterally, with the smooth and illdefined dorsal surface; the posterior part of the dorsal surface is strongly deflexed towards the posterior carapace margin; the frontal region ( Fig. 2B View Fig ) is about one third as wide as the carapace, gently sloping anteriorly, with the obtusely angulated median part. Eyestalk is short and stout, with prominently large cornea, being partly protruded from the orbit. The carapace lateral margins of both sides ( Fig. 2A View Fig ) are longitudinal and parallel to each other. Each epibranchial angle is obtusely angulated, directed towards the subhepatic region, and reaching the level of the supraorbital margin. In the specimen examined, the right cheliped is lost; the left cheliped is smooth and strong, with the inflated palm; the merus is widened distally, with three obtuse edges; the carpus is small, and its inner angle is obtuse; the palm is quite smooth, and the outer surface and upper margin is regularly convex; both fingers are curved, and the movable finger is shorter than the immovable finger. The first three pairs of the ambulatory legs are long, robust and similar in general shape; the second pair is the longest, and the first and third pairs are similar in length and shape; three edges of each merus are sharp, with the surface between the lower edges is flattened; the anterior margins of the carpi and propodi are heavily furnished with soft hairs; the posterior margin of each carpus of the second pair is lobate distally, with a longitudinal narrow ridge on the upper surface; each dactylus is short and rapidly narrowed at the junction with the claw-like dactylus. The last leg is markedly small and shorter than the merus of the third pair. The pleon ( Fig. 2C View Fig ) is narrow and seven-segmented. The Japanese name, Takeda-koyubi-pinno, was proposed by Naruse (2017).

Another species of Takedactylus , T. compressus Naruse and Yoshida, 2018 , obtained from tube of annelid worm, Loimia sp. , at Nakoudojima Island and Muko-jima Island, Ogasawara Islands, is, without doubt, close to T. masatsunei , but has the much wider carapace.

Distribution. ɹ This species has hitherto been known only by the female holotype from Sesoko Island, west of Okinawa Main Island, Ryukyu Islands.