More than 450 million years ago, long before dinosaurs appeared and before animals or plants had spread widely across dry land, crinoids were already thriving in some of Earth’s earliest coral reefs. These ancient relatives of starfish looked somewhat like flowers growing on stalks beneath the sea.
Crinoid fossils give paleontologists important clues about how early animals evolved and how complex life developed. But fossils usually preserve only durable structures such as shells or skeletal plates. Delicate tissues tend to disappear quickly after death, leaving major gaps in scientists’ understanding of how these animals actually lived.
A remarkably rare fossil studied by University of Oklahoma paleontologists is now helping fill in part of that missing picture.
“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. “Most fossils are only made up of hard parts like bones, teeth, or shells. Soft tissues are only preserved when the environment acts almost like a natural refrigerator or vacuum-sealer — conditions that are incredibly rare.”
The fossil belongs to Dendrocrinus simcoensis and preserves its tube feet, delicate structures that almost never survive fossilization. Cole and her colleagues describe the specimen in a new study.
Only two known crinoid fossils have ever been found with preserved soft tissue. This specimen is also the oldest example discovered so far.
“Preservation like this is truly one in a million,” Cole added. “Crinoid fossils number in the millions, and this is only the second time soft tissues have ever been found.”
Oldest Known Crinoid Soft Tissue
The preserved tissues date back more than 450 million years, making them far older than the earliest dinosaurs.
“It’s incredible these soft tissues have survived more than 450 million years,” said Dr. David Wright, another OU paleontologist and assistant curator of invertebrate paleontology at the Sam Noble Oklahoma Museum of Natural History, who co-authored the study with Cole. “For reference, these soft tissues are more than 200 million years older than the oldest dinosaur.”
For crinoids, tube feet play an important role in feeding, responding to water currents and occupying different ecological niches. Their size, spacing and overall form can vary depending on the animal’s surroundings and feeding method. In that sense, they can reveal information about lifestyle in much the same way that mammal teeth can reveal information about diet.
“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 explained. “Differences in their structure tell us about what kinds of environments a species lived in and how it fed.”
When the researchers compared the fossil with crinoids living today, they found notable differences in anatomy.
“Comparisons with living crinoids show that the anatomy of this ancient species was very different,” Cole added. “This gives us new insight into how crinoids evolved and how their feeding strategies changed over hundreds of millions of years.”
New Clues About Ancient Oceans
The fossil does more than expand scientists’ knowledge of crinoid anatomy. It can also help reconstruct the ecology of early Paleozoic oceans, when crinoids were among many early animal groups flourishing in reef ecosystems.
“Fossilized remains of long-extinct species can show features well outside the range of variation we see in living species,” Wright said.
“By comparing ecological ways of life for extinct and modern species, we can understand how patterns of adaptive evolution have changed through time and what factors shaped the modern biosphere.”
Soft tissue is exceptionally uncommon in fossils of early echinoderms, the larger animal group that includes crinoids and starfish. Because so little of it survives, every newly discovered specimen can greatly increase what researchers know about ancient ecosystems, feeding behavior and evolutionary change.
A Rare Fossil Hidden in a Museum Collection
Many people picture major paleontological discoveries happening during expeditions in remote landscapes. Fieldwork does produce new fossils, but important discoveries can also emerge from specimens that have already spent years stored, cataloged and protected in museums.
“New fossil discoveries ultimately come from fieldwork, but museum collections play a significant role in this kind of integrative research,” Wright said. “We don’t always know the full significance of the specimens we collect. New technologies, ideas or expertise often find surprising ways to utilize existing specimens to make new discoveries.”
The Dendrocrinus simcoensis fossil containing the preserved soft tissue had been housed for years at Montréal’s Musée de paléontologie et de l’évolution. The small museum operates entirely with support from community donations.
Its unusual scientific importance became apparent when crinoid specialists Drs. Cole and Wright examined the specimen closely during a research visit.
“This discovery highlights the importance of museum collections and the community support that keeps them alive,” Cole said. “Without the dedication of many people caring for these collections, this research would never have been possible.”
The invertebrate paleontology collections overseen by Drs. Cole and Wright at the Oklahoma Museum of Natural History contain more than a million specimens, and additional fossils are added every year. Collections on that scale can hold discoveries that may not be recognized until years or even decades after the specimens were first collected.
“This is why we work to make our collections accessible to researchers around the world,” Wright said. “There are simply too many fossils to study over one person’s career. There’s more than a lifetime’s worth of discoveries waiting to be found.”