Scoliodota Clark 1908

Genus Scoliodota Clark, 1908

[New Japanese name: Ibokagi-namako-zoku]

Scoliodota Clark, 1908: 125, type species Chirodota japonica Marenzeller, 1882:123–124 [original designation/monotypy.], fixed by Heding, 1928: 319.

Scoliodota Heding, 1928: 319, type species Scoliodota theelii Heding, 1928: 319–322, rejected by Clark, 1946: 461.

Scoliorhapis Clark, 1946: 461, type species Scoliodota theelii Heding, 1928: 319–322, fixed by Rowe in Rowe and Gates, 1995: 267.

Modified diagnosis. Taeniogyriid genus with 10 stout tentacles with palmate or plumose digits. Calcareous ring stout, each element with short anterior projection and notable posterior depression, without any nerve hole, but the medio-ventral element with an anterior notch. Detectable retractor muscles or ligaments (namely: retractor organ) combined calcareous ring with longitudinal muscles. Anterior body wall with sigmoid hook ossicles which arranged by single circle under the skin, with facing open pointed end toward outside of circle and outside of skin, where the skin notably rising and conforming small verrucae however without passing through the skin. Sometimes wheel ossicles observed in body wall of mostly young animals, while adults usually lack wheel ossicles.

Remarks. The above diagnosis has been modified from the original definition by Clark (1908). The modifications include follows: the occasional presence of the chiridotid wheels (especially in young animals); only one circle of the sigmoid bodies under the skin (neither scattering nor penetrating the skin); stout calcareous ring with radial retractor organ.

Our modification of the generic diagnosis for Scoliodota Clark, 1908 pertains to the taxonomic boundaries of the two genera Taeniogyrus Semper, 1867 and Scoliorhapis Clark, 1946.

Previously, the genus Taeniogyrus Semper, 1867 was comprised of 26 species, including Taeniogyrus japonicus (Marenzeller, 1882) and Taeniogyrus australianus (Stimpson, 1855), which are represented by the nominal species Chirodota japonica Marenzeller, 1882 and Chirodota australiana Stimpson, 1855, and are the type species of Scoliodota Clark, 1908 and Taeniogyrus Semper, 1867, respectively. Therefore, prior to this study, Scoliodota Clark, 1908 was a junior synonym of Taeniogyrus Semper, 1867.

Likewise, Scoliorhapis Clark, 1946 harbored seven species including Scoliorhapis theelii (Heding, 1928) and Scoliorhapis lindbergi (D’yakonov in D’yakonov et al., 1958). Scoliorhapis theelii was originally described as Scoliodota theelii Heding, 1928, which was the type species of Scoliodota Heding, 1928. Because S. theelii was a junior homonym of Scoliodota Clark, 1908, its genus was replaced with Scoliorhapis Clark, 1946, making Scoliodota Heding, 1928 permanently invalid. Scoliorhapis lindbergi contains two nominal species: Scoliodota lindbergi D’yakonov (D’yakonov et al., 1958) and Scoliodotella uchidai Oguro, 1961. The latter is the type species of Scoliodotella Oguro, 1961, which had been regarded as a junior synonym of Scoliodota Heding, 1928 and Scoliorhapis Clark, 1946 before the present study.

Our findings indicated that the three nominal species Chirodota japonica Marenzeller (type species of Scoliodota Clark, 1908), Scoliodota theelii Heding (type species of Scoliodota Heding, 1928 [which is permanently invalid] and Scoliorhapis Clark, 1946), and Trichodota dendyi Mortensen would belong to the same genus. This genus should be referred to as Scoliodota Clark, 1908, as it is distinct from Chirodota australiana Stimpson, 1855 (type species of Taeniogyrus Semper, 1867) and Scoliodotella uchidai Oguro (type species of Scoliodotella Oguro, 1961).

With “ Taeniogyrus dendy ” and “ Taeniogyrus japonicus ” being removed, the genus Taeniogyrus Semper, 1867 is now comprised of 24 species (addition to this, three accepted species will be nearly nominated).

Of the seven species formerly belonged to Scoliorhapis, we transferred the type species “ Scoliorhapis theelii ” to the newly diagnosed Scoliodota Clark, 1908. The remaining six species are now referred to as Scoliodotella Oguro, 1961, yielding Scoliodotella biopearli (O’Loughlin & VandenSpiegel) comb. nov., Scoliodotella dianthus (Solis- Marin et al.) comb. nov. (to be a synonym of Scoliodota japonica in the present study), Scoliodotella lindbergi (D'yakonov, 1958 in D'yakonov et al.) comb. nov., Scoliodotella massini (O’Loughlin & VandenSpiegel) comb. nov., Scoliodotella sesokoensis (Yamana & Tanaka) comb. nov., and Scoliodotella stepanovi (Smirnov & Panina, in Smirnov et al.) comb. nov.

Amended diagnoses for Taeniogyrus Semper, 1867 and Scoliodotella Oguro, 1961 should be presented in future studies.