Echinoid spines and bryozoans in yellow weathering subunit of Worland Limestone

Echinoid spines (lower left and left-center) and fenestrate bryozoans
(upper right) concentrated on bedding surface in yellow-weathering
zone of Worland. Apparently the echinoid spines simply fell away from
the animal's body after it died. They were neither scattered nor
fragmented, attesting to low current strength. Echinoid spines are easily
confused with brachiopod spines. These echinoid spines are barbed,
however, and brachiopod spines are not. Also, brachiopod spines have
lamellar microstructure and large central cavities, whereas those of
echinoids have a very narrow central cavity and break along calcite
cleavage planes. Also, brachiopod spines are often slightly to strongly
curved, whereas echinoid spines are straight.

Return to Technical Discussion

Main Menu