The oldest complex animal life in the world can be found in the ancient fossil-bearing rocks of the Mistaken Point Ecological Reserve and UNESCO World Heritage Site and the Bonavista Peninsula’s Discovery UNESCO Global Geopark.
One of the most iconic and beautiful fractal-like forms is a spindle-shaped fossil known as Fractofusus misrai.
Dr. Duncan McIlroy, professor of paleontology in the Department of Earth Sciences, Faculty of Science, suggests that the fossil lived flat on the deep, dark ocean floors of the Ediacaran period, almost 570 million years ago, growing bacterial symbionts on their lower surfaces and using their upper surfaces to capture food and oxygen from the ocean.
Previous studies of simulated flow around Ediacaran fossils, based on the Mistaken Point assemblages, have used simple morphologies and do not capture the essence of these beautiful fossil organisms.
To try to remedy this, Dr. McIlroy’s research group, which includes PhD candidate Daniel Pérez-Pinedo, master of science student Jenna Neville and Dr. Rod Taylor, worked with world-renowned paleo-artist Bob Nicholls to create a 3D reconstruction that included the upper surface of the organism.
This digital model was very different from previous models and was based on the wealth of Fractofusus fossils at Mistaken Point.
Oblique positions
Dr. McIlroy’s work fascinates biologist Daniel Pérez-Pinedo; it’s the reason he came to Memorial University to pursue his doctoral degree.
Mr. Pérez-Pinedo has been studying a new fossil site at Capelin Gulch, near the community of Melrose on the Bonavista Peninsula, where Fractofusus misrai was recently discovered.
He discovered that the Fractofusus fossils there were not randomly oriented as recent wisdom said they should be.
Instead, they had orientations that showed clusters with the long axis positioned obliquely to the current.
Uncovering the ecology of the Ediacaran seafloor of Newfoundland made Mr. Pérez-Pinedo feel as if he was peering through a window into the dawn of animal life, he says.
“I felt like we had really brought one of these enigmatic fossil organisms to life.”
He first proposed that the oblique orientation of Fractofusus might be due to the organisms trying to find a compromise between not being washed away by the current and accessing the maximum amount of current for feeding and exchanging oxygen and waste products.
“Like lots of great research, it raised as many questions as it answered,” said Dr. McIlroy. “Fortunately, Daniel was willing to learn the skills needed to answer some of those questions, too.”
For the next phase in his research, Mr. Pérez-Pinedo used Mr. Nicholls’ 3D models to understand exactly how Fractofusus might have interacted with weak seafloor currents.
“I decided to learn how to employ computed fluid dynamic modelling to simulate how Bob Nicholls’ models might work in a current,” he said.
“I remember when Daniel sent me the first successful attempts at modelling the flow around Fractofusus,” said Dr. McIlroy. “I was blown away by how the flow was captured and funnelled by the rangeomorph branches. For the first time in my career, I felt like we had really brought one of these enigmatic fossil organisms to life.”
The researchers were then able to experiment with organism orientations and make calculations of drag. They found support for their original hypothesis.
Oblique orientations were optimal for the fossil organisms and provided an ideal compromise between minimizing drag and maximizing access to the current.
“What sets the fossils in Newfoundland apart is their extraordinary preservation,” said Mr. Pérez-Pinedo. “Entire communities of soft-bodied fossil organisms were preserved in situ beneath volcanic ash horizons, offering an unprecedented level of detail. Considering these records date back approximately 570 million years, the sub-millimetre preservation is simply breathtaking.”
The long wake of the slowed current behind Fractofusus in Mr. Pérez-Pinedo’s simulations shows that they likely changed seafloor conditions in a manner that might have benefitted organisms down current from them, including the potential for increased sedimentation of food particles onto the seafloor.
“Daniel’s refined modelling suggests that we should be working hard to try to use our current understanding of the shapes of these ancient fossils, and turning them into 3D models that are as realistic as possible and then experiment to find out how they interacted with simulated currents,” said Dr. McIlroy.
Read the published paper in Science Direct.
