Sigmodota Studer, 1876

O’Loughlin, P. Mark & VandenSpiegel, Didier, 2010, A revision of Antarctic and some Indo-Pacific apodid sea cucumbers (Echinodermata: Holothuroidea: Apodida), Memoirs of Museum Victoria 67, pp. 61-95 : 78-80

Sigmodota Studer, 1876

Table 3

Sigmodota Studer, 1876: 454 .— Théel, 1886a: 16, 33.— Ludwig, 1898: 73, 81–82.—Östergren, 1898: 117–118.—H. L. Clark, 1908: 121.— Dendy and Hindle, 1907: 113.— Heding, 1928: 277.— Pawson, 1964: 466.— Smirnov, 1998: 519.

Diagnosis. Taeniogyrinid genus with 12 plates in calcareous ring, 12 tentacles, peltato-digitate, 4–7 pairs of digits per tentacle, terminal pair longest; rods in tentacles; chiridotid wheels and sigmoid hooks in body wall; teeth on the inner rim of wheels in continuous series; wheels grouped into papillae, hooks scattered in body wall; no miliary granules in longitudinal muscles; 3–10 polian vesicles; ciliated funnels present.

Type species. Type species fixed here (under Article 70.3.2 of the 1999 edition of the ICZN Code) as Chiridota contorta Ludwig, 1875 , misidentified as Holothuria (Fistularia) purpurea Lesson, 1830 in the original monotypy designation by Studer (1876).

Other species. Taeniogyrus dubius H. L. Clark, 1921 (as S. dubia ); Taeniogyrus magnibaculus Massin and Hétérier, 2004 (as S. magnibacula ).

Remarks. We follow Ludwig (1898) and H. L. Clark (1908) and agree that Studer’s Sigmodota purpurea ( Lesson, 1830) is a junior synonym of Taeniogyrus contortus ( Ludwig, 1875) . Studer (1876) erected his new genus Sigmodota for the species Holothuria (Fistularia) purpurea Lesson, 1830 because of the presence of sigmoid hooks in apodid specimens from the Kerguelen Is and Magellanic region. He reported 12 tentacles, and ignored the 10 tentacles in the species Holothuria (Fistularia) purpurea Lesson. As understood by Ludwig 1898 and H. L. Clark 1908 and as argued above by us in “Relevant history of species misidentification” the material that Studer examined had 12 tentacles, hooks and wheels.

H. L. Clark (1908) judged Sigmodota Studer to be a junior synonym of Taeniogyrus Semper, 1867 , which he diagnosed as having: 10 or 12 peltato-digitate tentacles; 1 or several polian vesicles; ciliated funnels not in stalked clusters; wheels in papillae; large sigmoid hooks scattered in body wall; lacking miliary granules. He included two species: Taeniogyrus australianus ( Stimpson, 1855) , with 10 tentacles, hooks in papillae, single polian vesicle; and Taeniogyrus contortus ( Ludwig, 1875) , with 12 tentacles, hooks scattered, 6 or 7 polian vesicles.

As discussed above in “Ossicle clusters in generic diagnosis” we reject ossicle aggregation in the body wall as a generic diagnostic character, and judge that tentacle number is a good generic character. Thus we raise Sigmodota Studer out of synonymy with Taeniogyrus Semper, 1867 on the basis of the type species Chiridota contorta Ludwig having 12 tentacles and the type species of Taeniogyrus , Chiridota australiana Stimpson , having 10.

We examined specimens of Sigmodota contorta (Ludwig) and Sigmodota magnibacula (Massin and Hétérier) and found that there were consistently 12 subequal plates in the calcareous ring. Plates were fused, and joined beneath the tentacle bases attached to the outside face of the ring. Each plate had a low anterior projection and a shallow concave posterior indentation.