Ordovician echinoderm fossil from Utah, USA

This video is called Life Science – Echinoderms.

30 January 2015

Name: Haimacystis rozhnovi
Location: Utah, USA, Wah Wah Limestone
Age: 466-488 million years ago, Ordovician Period

The early history of major groups of animals is often messy and mysterious. The suite of features that make those groups distinctive today show up piecemeal in different combinations in early species, like Haimacystis.

A long, thin column of discs and a flattened pod with a few wispy arms make up the body of this individual of Haimacystis. The animal is part of the same group that includes living sea stars, sea cucumbers, and intricately crowned sea lilies. The group also includes little-known, extinct animals like rhombiferans and corkscrew-armed gogiids.

Sea stars, sea lilies and other living animals in that group all have skeletons of calcified plates. All have five-part bodies that are usually symmetric.

Individuals of Haimacystis share some features with living members of their group, but their other features blur the neat distinctions that make five-part animals so different from other groups. They have calcified plates but they also have nineteen arms instead of five or ten. At best, they have two-part symmetry.

Haimacystis wasn’t a forerunner of its living relations or a species “on the way” to a more recognizable animals like starfish. Multiple species of sea lilies, one species of animals distantly related to sea stars, and at least six species of other early, irregular, extinct animals lived alongside Haimacystis. Haimacystis is its own subplot in the story of five-part animals.

Specimen Number: 1810TX5

References:

Sumrall, Colin D., James Sprinkle, and Thomas E. Guensburg. “Comparison of flattened blastozoan echinoderms: Insights from the early Ordovician eocrinoid Haimacystis rozhnovi.” Journal of Paleontology 75(2001):985-992.

Where are similar fossils found?

Bonus: The fossil’s name has an interesting backstory. “Haimacystis is a compound of the Greek haima, flowing blood, and cystis, sac, referring to the blood dripping from superficial leg wounds suffered by one of the co-authors when the biggest slab of specimens described herein toppled over and almost crushed him.” – Sumrall et al. 2001, p. 992