2.8" Eocrinoid (Ascocystites) - Ordovician

Eocrinoids were one of the earliest groups of echinoderms and are believed to be closely related to many other groups including crinoids, cystoids and blastoids. They first appeared in the Early Cambrian and survived until the Late Silurian. Despite the name ("dawn crinoids"), they may not be directly ancestral to the true crinoids but crinoids instead evolved from the ancestors of Eocrinoids.

Eocrinoids had a vase-shaped body (calyx), covered by crystalline calcite plates. These plates were symmetrical and bore ridges which meet up with the ridges of other plates, giving a geometrical pattern. They had a stalk which attached them to the bottom of the ocean via a holdfast and were benthic suspension feeder which used their arms to move particles of food towards a mouth.