Paleontologists Find Strange Ball-Like Structures in 80-Million-Year-Old Fossils

Friday, May 15, 2020

Uintacrinus socialis from the Niobrara Formation, Kansas, United States. Image credit: James St. John / CC BY 2.0.

A team of paleontologists from Australia and the UK has found fullerene-like structures in Cretaceous-period crinoids, marine animals related to starfish, sea urchins, and brittle stars. The researchers believe these strange structures might have acted as a buoyancy chamber to allow the animals to float in seawater but also protect them.

Crinoids, also known as sea lilies or feather-stars, are part of a large group of marine invertebrate animals called echinoderms. Other echinoderms are starfish, brittle stars, sand dollars, sea urchins, and sea cucumbers.

The skeleton of echinoderms is made of the mineral calcite, and consists of hundreds of individual plates of different shapes and sizes.

All living echinoderms have what is called pentameral symmetry, which means their bodies are organized in patterns of five; for example, the five arms of the common starfish. Crinoids may have as few as five arms, but usually they have arms in multiples of five.

Crinoids are unusual looking animals because they look more like plants than animals. Superficially, the stem or column of a crinoid resembles the stalk of a flower, the calyx or head resembles the sepals of a flower, and the arms resemble the petals of a flower.

These marine animals first appeared in the seas of the Cambrian period, about 300 million years before dinosaurs. They flourished during Paleozoic and Mesozoic eras, and some survive to the present day. Around 600 living species are known; most are free-living feather stars or comatulids living in the shallow seas.

“Crinoids were in a very dangerous place millions of years ago when the oceans were shallower and they shared them with predators such as crabs and fish,” said co-author Dr. Aaron Hunter, a researcher in the School of Earth Sciences at the University of Western Australia and the Department of Earth Sciences at the University of Cambridge.

“Survival was critical and the ball-like structures, able to withstand very heavy loads, formed around them to protect them from the harms of the ocean and aid buoyancy.”

“These animals could then spread around the world and have been found in chalk rocks from Texas, US to Kalbarri in Western Australia. They could form a snow shoe to sit on the bottom of the shallow oceans or float and relocate to safer places.”

Marsupites testudinarius. Image credit: Ghedoghedo / CC BY-SA 3.0.

Dr. Hunter and his colleague, Dr. Jennifer Hoyal Cuthill from the Institute of Analytics & Data Science & School of Life Sciences at the University of Essex, the Department of Earth Sciences at the University of Cambridge, and the Earth-Life Science Institute at Tokyo Institute of Technology, analyzed the fossilized remains of Marsupites testudinarius and Uintacrinus socialis, two crinoid species that lived 80 million years ago (Cretaceous period).

Both species possessed long feeding arms and an enlarged, close-to-spherical head, composed of 16 large plates in Marsupites testudinarius but many more, small plates in Uintacrinus socialis.

According to the team, the heads of these animals show structural similarities to carbon fullerene and fulleroid molecules, respectively.

Marsupites testudinarius had fewer but relatively large plates, creating a stable structure,” Dr. Hunter said.

Uintacrinus socialis on the other hand has far more complex plates that form a dome.”

“The structures are also found in the carbon molecule buckminsterfullerene but this is the first time we have found such a structure in fossils and it still remains a mystery why these successful structures did not evolve again.”

The findings were published in the journal Palaeontology.


Jennifer F. Hoyal Cuthill & Aaron W. Hunter. Fullerene-like structures of Cretaceous crinoids reveal topologically limited skeletal possibilities. Palaeontology, published online February 18, 2020; doi: 10.1111/pala.12474