Camptostroma

In life, Camptostroma would have resembled a cupcake, with the mouth in the center of the upper surface, with ambulacra radiating from it in the 2-1-2 pattern common in early echinoderms. The ambulacra are straight in juveniles, but in larger adult specimens, ambulacra A, B, C, and E curve clockwise while ambulacrum D curves counter-clockwise. The anus is near the periphery between ambulacra C and D. The ambulacra may have extended beyond the upper surface on stubby arms. While this diagnosis is tentative, ongoing work appears to support it. ==Classification and relationships==

While initially considered to be a scyphozoan due to the fossil's medusoid shape, later investigation detected the presence of stereom plates with the calcitic cleavage pattern diagnostic of echinoderms. However, a later classification based on that of the Treatise omitted this class. Camptostroma has since been placed in a class of basal echinoderms, the Edrioasteroids, although some recent authors only describe it as "edrioasteroid-like". However, other phylogenies are ambiguous regarding whether it is closer to the crinoids, eocrinoids, or eleutherozoans. ==References==