Savigny, 1816
Solitary zooids
Up to 100 mm long (Iasis zonaria, Iasis zonaria 1). Test very firm with a longer postero-median projection. Five body muscles. Intermediate muscle and body muscles broad. All the muscles interrupted dorsally and ventrally. The mature stolon describes one turn around the nucleus.
Aggregate zooids
Test very firm, asymmetric, with a posterior projection on its right side (Iasis zonaria 2). Five body muscles, all of them interrupted ventrally, MI interrupted dorsally as well; MV divided into two branches on the right side. Testis projecting as lobules around the nucleus. up to 7 embryos between MIV and MV (Esnal et al., 1987).
Species treated:
Iasis zonaria (Pallas, 1774)