A 450-Million-Year-Old Crinoid Fossil Preserves Soft Tissue Never Seen This Old

A remarkably rare fossil studied by University of Oklahoma (OU) paleontologists is helping fill a major gap in scientists' understanding of how early animals lived. Crinoids, ancient relatives of starfish that resembled flowers on stalks, were already thriving in some of Earth's earliest coral reefs more than 450 million years ago, but fossils usually preserve only durable structures such as shells or skeletal plates.

"After an animal dies, soft tissues like skin, eyes, or internal organs are the first things to decay," said Dr. Lena Cole, OU paleontologist and assistant curator of invertebrate paleontology at the Sam Noble Oklahoma Museum of Natural History. The newly studied fossil, belonging to the species Dendrocrinus simcoensis, preserves its tube feet — delicate structures that almost never survive fossilisation. "Preservation like this is truly one in a million," Cole said. "Crinoid fossils number in the millions, and this is only the second time soft tissues have ever been found." The preserved tissue is also the oldest known example, more than 200 million years older than the earliest dinosaur.

Tube feet play an important role in feeding, responding to water currents and occupying different ecological niches, said Dr. David Wright, another OU paleontologist and study co-author. "Since crinoid tube feet are used for feeding, you can think of them in a similar way to how we think about teeth in mammals," Wright said. "Differences in their structure tell us about what kinds of environments a species lived in and how it fed." Comparisons with living crinoids showed the ancient species' anatomy was notably different.

The fossil had been housed for years at Montréal's Musée de paléontologie et de l'évolution, a small museum that operates entirely on community donations, before its significance became apparent when Cole and Wright examined it during a research visit. The invertebrate paleontology collections the two oversee at the Oklahoma Museum of Natural History contain more than a million specimens.