SHENIINAE, P. K. L. Ng, P. F. Clark & Cuesta, 2010

Ng, Peter K. L., Clark, Paul F. & Cuesta, Jose A., 2010, Establishment of a new subfamily for Shenius anomalus (Shen, 1935) (Crustacea: Decapoda: Brachyura: Dotillidae), Journal of Natural History 44 (25 - 26), pp. 1531-1553 : 1532-1533

Subfamily SHENIINAE (new subfamily)

Type genus

Shenius Serène, 1971

Diagnosis

Carapace hexagonal, dorsal surface not convex with regions well defined, covered with short stiff setae. Buccal cavity broad, covering most of face; third maxillipeds with merus and ischium large, squarish, not forming any gape when closed. Ambulatory legs long, positioned laterally on thorax; meri of P2–P4 with dorsal margins armed with distinct spines; outer surface with submarginal carina. Male and female sternoabdominal cavity reaching to base of buccal cavity. Male abdomen with somite 5 shaped like hourglass. G1 sinuous, slender, with several short and long spines distally.

Remarks

From his choice of the species name ( anomalum ), Shen (1935) clearly had doubts as to placing the species in Camptandrium Stimpson, 1858 . In his Prodromus of the Indo-Pacific Brachyura, Serène (1968) retained the species in Camptandrium but later (Serène 1971) established a new genus Shenius within the Ocypodidae Rafinesque, 1815 , for the species, commenting that it differed markedly from the known species of Camptandrium . Serène and Umali (1972) elaborated on the problematic status of Shenius by illustrating more characters. In his review of Camptandrium, Serène (1974) reappraised the status of the Camptandriidae Stimpson, 1858 . He resurrected the Camptandriinae as a subfamily within the Ocypodidae , and also recognized the Scopimerinae Alcock, 1900 (= Dotillidae Stimpson, 1858 ). Nonetheless, Serène (1974) was unsure of the systematic status of Shenius . In defining the various ocypodid subfamilies, he placed Shenius with the group of genera that constitute the Dotillinae (as Scopimerinae), noting that they all had similar G1 structures ( Serène, 1974: 60). But in his provisional key to the Camptandriinae, Serène (1974: 66) treated Shenius as if it was a member of the subfamily.

In an unpublished thesis, Harminto (1988) had argued that while Shenius had many dotilline features, it was nevertheless so unusual that it merited its own subfamily within the Ocypodidae . Tan and Ng (1999: 195), in their revision of Camptandrium , noted “ Serène (1974) had in fact transferred Shenius (with some doubt) to the Dotillinae Stimpson, 1858. Shenius is certainly more closely affiliated to the Dotillinae as the male abdomen has all seven segments free (segments two and three always immovable in camptandriines). In addition to this, the G1 structure (slender and bent at tip), as well as the form of the mouthparts and orbital regions of Shenius differ significantly from that typically found in the Camptandriidae ” (see also Tan and Ng 1995).

Kitaura et al. (2002) proposed that the Dotillinae should be recognized as a family, and this was followed by Ng, Guinot and Davie (2008), who also placed Shenius in the Dotillidae . Ng, Guinot and Davie (2008), however, commented that, “The position of Shenius anomalus ( Shen, 1935) has not been settled. Shen (1935: 32, fig. 9A,B) originally placed it in Camptandrium because the carapace and legs are similar, but his figures of the suborbital margin, male abdomen and G1 ( Shen, 1935: figs 8B, 9C,D) do not indicate a close relationship. Realising this, Serène (1971) established a new genus, Shenius , for it. Serène (1974) then transferred Shenius to Dotillinae Stimpson, 1858 (present Dotillidae ), albeit with some doubt, probably because the carapace and pereiopod structures of Shenius , when compared to dotillids, are extremely different. Manning and Holthuis (1981) agreed that Shenius was not a camptandriid. In an unpublished thesis, Harminto (1988) re-examined Shenius and agreed with Serène (1974) about its relationships to the Dotillidae . As in dotillids the male abdomen has all segments freely articulating, the G1 is slender and bent at the tip, and the mouthparts and orbital regions are of the same form. The different carapace and pereiopod features, however, suggest that it should be placed in its own subfamily” ( Ng, Guinot and Davie 2008: 235).

With the exception of Shenius , the eight known genera of dotillids, Dotilla Stimpson, 1858 , Dotilloplax Tweedie, 1950 , Dotillopsis Kemp, 1919 , Ilyoplax Stimpson, 1858 , Potamocypoda Tweedie, 1938 , Pseudogelasimus Tweedie, 1937 , Scopimera De Haan, 1833 and Tmethypocoelis Koelbel, 1897 , have similar carapace and pereiopod structures. The atypical external morphology of Shenius (see below) strongly suggests that it should be placed in its own subfamily.