Dawn Crinoid Fossils
Echinodermata, Subphylum Blastozoa, Class Eocrinoidea (also called
Dawn Crinoid, or Eocrinoid)
Time: Middle Cambrian
51mm and 38mm
Site: Upper Wheeler Formation, Millard County, Utah
is a Cambrian cystoid that is among the earliest and most primitive
groups of echinoderms. For this reason they are sometimes called
a "dawn crinoids". They had a vase-shaped body (calyx),
covered by plates that were symmetrical and have a bifurcated brachiole,
a slender arm-like structure for food-gathering that closely resembled
those in cystoids.
differed from true crinoids in that they had pores along the margins
separating the plates, and the type of feeding arms they displayed.
The species Gogia spiralis derives its name from its tightly spiraled
arms and is only one of three Gogia species to have spiraled arms.
Gogia had a vase-shaped body or calyx with irregularly positioned
plates. It also had a stalk made up of smaller plates that attached
to the sea floor, and food-gathering arm-like structures called
brachioles. Gogia was a sessile (stationary) suspension feeder gathering
food with its arms in calm waters of shallow Cambrian seas. Gogia
spiralis usually attached directly to the mud, but on rare occasions
attached to brachiopods and trilobite fragments on the sea floor.
Gogia were widely distributed in the lower and middle Cambrian of
western North America, but only a few partial specimens have been
found in the Burgess
Shale. Gogia occurred at the base of the cystoid radiation,
with three distinct cystoid lineages derived from different Gogia
species. Gogia lived only during the Cambrian time period, but the
cystoids that evolved from them survived until the end of the Devonian.
Also see: Utah
Cambrian Explosion Fossils
fossil pictures to enlarge