Viaderiana typica Ward, 1942

Manikandan, K, Megalaa, N, Valliappan, Subramanian, Nandini, K, Rani, Lourdu V, Dakshinamurthi, Senthil & Nagappan, Nagappan, 2022, Crabs (Crustacea, Decapoda) from the Seas of East and Southeast Asia Collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 3. Sahul Shelf, Bulletin of the National Museum of Nature and Science. Series A, Zoology 48 (2), pp. 35-83 : 75-76

Viaderiana typica Ward, 1942

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 29, 1 juv. ( CB 4.1 including lateral spines×CL 4.0 mm) , NSMT-Cr 30764.

Remarks. In the genus Viaderiana , the carapace dorsal surface is typically covered with long, rather sparse, silky setae, and shallowly divided into regions; the carapace anterolateral margin is armed with two spiniform tubercles and a third vestigial tooth or granule behind the external orbital angle. The specimen at hand is unfortunately lacking all the chelipeds and ambulatory legs, while the generic affiliation is without doubt in Viaderiana .

The carapace is narrow and distinctly quadrate with the almost longitudinal posterolateral margins, and the posterior of the two anterolateral spines is slightly larger than the first. The latter character is of specific value in Viaderiana , but it is also affected by maturity, and the present specimen is a juvenile. As for the narrowly quadrate carapace, this specimen is close to V. typica Ward, 1942 and V. quadrispinosa ( Zehntner, 1894) . The latter species is well known by its characteristic chocolate brown color pattern, although in the specimen examined, the color is completely faded, without trace of color pattern. In adult V. typica , the carapace has the coarsely areolated dorsal surface and stronger anterolateral teeth. Recently, Maenosono (2020) reported on four species of Viaderiana from the Ryukyu Islands, namely, V. incerta (Takeda and Miyake, 1969) , V. typica Ward, 1942 , V. quadrispinosa ( Zehntner, 1894) and V. longipes (A. Milne-Edwards, 1873) , and discussed the identification challenges in detail, with fine photographs. Following the details elucidated by Maenosono (2020), the young specimen at hand, having no chelipeds and ambulatory legs, is reasonably, but tentatively identified as V. typica among the congeners from the Ryukyu Islands as well as the other, about 14, Indo-West Pacific congeners.

Distribution. West Pacific (Ryukyu Islands, Palau Islands, Indonesia, Viet Nam and Thailand), Indian Ocean ( Mauritius), and now northern Australia, as referred to Ward (1942), Serène (1971, 1980), Takeda (1972), and Maenosono (2020). Maenosono (2020) recorded two males collected from crevices of a dead coral block at Urasoe, Okinawa-jima in the central Ryukyu Islands.