Fossil crinoid stem

Today, you get a photo of a fossilized crinoid stem, from the Mississippian-aged Lodgepole Limestone of the Bridger Range, north of Bozeman, Montana. A pencil is provided for scale:

crinoid_stem

Zoomed-in a bit, and cropped. The segments (“columnals”) show up nicely:

crinoid_stem_2

Crinoids are echinoderms, the invertebrate phylum which includes sea urchins and sea stars. However, at first glance you might think they were plants, as they are sessile (mainly sessile, anyhow) and have an overall form much like a kindergartner’s sketch of a flower. This morphology is where their common name, sea lilies, comes from.

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