Scientists discover how marine creatures survived in the Jurassic era

Scientists from The University of Western Australian and University of Cambridge have discovered that crinoids, marine creatures from the class of animals that includes starfish and sea urchins, survived the Jurassic era by clinging to floating logs and large rafts that allowed them to travel vast distances across the ocean.

Understanding how crinoids survived on these rafts in Jurassic times has remained a mystery up until now. It is understood they survived much longer in the Jurassic period, compared to modern day, but just how they achieved this has baffled scientists.

The research team examined crinoid fossils from German museums and collections and used a spatial analysis to examine fossil positioning to understand their abundancy, size, distribution and growth patterns.

Adjunct Research Fellow Aaron Hunter from UWA’s School of Earth Sciences said crinoids were in a precarious position in ancient times when oceans were shallower and they faced more predators such as crabs and fish.

“We found that floating logs that could stay afloat for months or years became essential for their survival in the otherwise uninhabitable shallow seas of what is now England and Germany,” Dr Hunter said.

“We also developed a diffusion model to look at how long a wood log survived as a means of transport and shelter for the creatures, before it would sink. We found some colonies could last longer than 20 years.”

Dr Hunter said adapting to this way of life allowed the crinoids to avoid predators and they could also access food found on the surface of the ocean.

“Raft colonies still exist today where plants and animals use objects in the ocean as a means of transportation. It explains how remote islands such as Hawaii were colonised by flora and fauna,” he said.

Dr Hunter said the findings offered insight into the use of floating logs and rafts today by plants and animals that were normally hard to observe due to the vastness of the ocean. 

“This is a common means of transport and has been observed in situations such as after the Japanese 2011 Tōhoku earthquake and tsunami, when plants and animals rafted from Japan to the coast of North America,” he said.