Thyonidium

Düben & Koren, 1844

13 species

Tentacles 20, exceptionally fewer or more, five pairs of larger alternating with five pairs of smaller. Ambulacral appendages in the shape of pedicels sometimes densely crowded, sometimes more thinly scattered; often an arrangement of them in rows distinguished along the ambulacra. (Fisher, 1907)

Dendrochirote holothurians with 15 tentacles in two circles (10+5). The podia scattered evenly over the whole body. (Only in very young animals are the podia confined to double rows on the radii). The calcareous ring is simple and without forked tails. The calcareous bpdies are well developed towers with four columns and a jagged ring forming a crown. They lie in the epidermis and are spread evenly and thickly over the whole body. There is no calcareous body loss in the very young or in very old animals. (Heding & Panning, 1954)

Thyonidiinae with 20 tentacles, 5 pairs of large tentacles in an outer ring alternating with 5 pairs of small tentacles in an inner ring (10+10). (McKenzie, 1991)