Iowa State Fossil

Crinoid is the Iowa state fossil. They make up the most ancient class of the phylum echinodermata, the Crinoidea.

**said to be the "proposed'' fossil of Iowa.

crinoid diagram


The crinoid have three different sections, the stem, the calyx, and the arms.

They are soft bodied animals had a skeleton structure of plates and spines covered with a leathery skin. The main body is made up of a flat cup, a ring of flexible arms, and a mushroom-shaped tube. The top of the tegmen is often ringed with spines that may have held an umbrella membrane. Some species cups are ringed in triangular spines, while others are rather long. The arms often divide, sometimes several times. The surfaces of the tegmen and inner arms grew celia (hairs) that directed water currents toward the animal's mouth. The bottom of the cup attaches to a long stem. The stem was made up of discs that can be round, oval, spiraled, or stars, they often have a hole in the center. Stem segments are sometimes called “pop rocks” because they explode in a fire, like popcorn. A root-like structure anchored the animal to the sea floor but did not absorb nutrients like a plant's root.

Fossil examples:

107892-004-90D9872D.jpg Scyphocrinites.jpg 6crinoid-moroccan206.jpg

Time Existed

The crinoid appeared and developed during Paleozoic era. Crinoids are considered to be the dominated at that time. Commonly, people call them "sea lilies" because they resemble a plant. Mississippian is considered to be the age of crinoids, however they appeared first in the fossil records about 530 million years ago. During the carboniferous period, the crinoids showed big morphological diversity. Large number of Paleozoic crinoids started to die off during Mesozoic era generally after Permo-Triassic extinction. However, during Mesozoic era, there was another great development of the animals with more flexible arms. Their population also was reduced during Cenozoic era, and they mostly existed in the deep ocean. Crinoids are considered to be among the most abundant and important fossils. Crinoids were major carbonate producing organisms during the Paleozoic and Mesozoic. In fact, entire carbonate shelves were made of parts of crinoidal skeletons. In general, crinoids lived in groups of several thousands, permanently attached to the ocean floor. Some crinoids, though, were ustalked. Their environments graded from very shallow to quite deep waters, 13,000 feet and more.


The remains of an organism that survive natural biological and physical processes must then become quickly buried by sediments. The probability for an organism to become fossilized increases if it already lives in the sediment , and those on the sea floor are more readily fossilized than those floating or swimming above it. Catastrophic burial with a rapid influx of sediment is necessary to preserve delicate complete animals such as crinoids. This explains why most crinoids, for example, are found only as stem pieces. Since crinoids were not usually buried quickly, their hard stem parts are far more frequently found as fossils. Observations of rare living crinoids have shown that they will rapidly disarticulate within a few days of death. Rapid burial, in contrast, prevents this disintegration, and thus explains a few localities where beds of delicate crinoids, starfish and brittle stars are preserved in their entirety.

Discovered by:

Articles do not say who discovered the fossil in Iowa.

Reason it became the state fossil:

It is very common in ares such as Marshalltown.


1. Rosenkranz, M. (2005). Student papers in geology. Retrieved from
2. Fossil Gallery - Crinoids, Blastoids, Cystoids. (n.d.). Catnapin. Retrieved January 22, 2012, from
3. Crinoid. (2012, January 12). In Wikipedia, The Free Encyclopedia. Retrieved 23:07, January 22, 2012, from
4. crinoid: fossils. [Photograph]. In Britannica Online for Kids. Retrieved from
5. Iowa Assosiation of Naturalists (1999, August). Iowa Geology and Fossils. Retrieved January 22, 2012, from