In the remote outback of South Australia, paleontologists have unearthed fossils of a peculiar creature that may rewrite our understanding of early animal life. Named Quaestio simpsonorum, this ancient marine organism lived approximately 555 million years ago and is one of the earliest known animals capable of movement.
A Question-Marked Pioneer
“The animal is a little smaller than the size of your palm and has a question-mark shape in the middle of its body that distinguishes between the left and right side,” Scott Evans, assistant professor of geology at Florida State University and lead author of the study, said in a press statement. “There aren’t other fossils from this time that have shown this type of organization so definitively. This is especially interesting as this is also one of the first animals that was capable of moving on its own.”
Discovered at Nilpena Ediacara National Park, a site renowned for its rich fossil beds, Quaestio simpsonorum lived during the Ediacaran Period — a fundamental era when single-celled organisms began evolving into complex multicellular life.
Researchers believe that Quaestio simpsonorum behaved like an ancient underwater vacuum, roaming the seafloor and consuming nutrients such as microscopic algae and bacteria. As it moved, it left behind trails in the organic mat that coated the seafloor — a kind of nutrient-rich prehistoric slime.
“One of the most exciting moments when excavating the bed where we found many Quaestio was when we flipped over a rock, brushed it off, and spotted what was obviously a trace fossil behind a Quaestio specimen — a clear sign that the organism was motile; it could move,” said Ian Hughes, a graduate student in organismic and evolutionary biology at Harvard University.
The creature’s distinct left-right asymmetry is particularly notable. It marks an important evolutionary development that allowed animals to do different things with each side of their bodies, hinting at the genetic mechanisms that would later give rise to more complex animals.
“Determining the gene expressions needed to build these forms provides a new method for evaluating the mechanisms responsible for the beginnings of complex life on this planet,” Evans explained. “Because animals today use the same basic genetic programming to form distinct left and right sides, we can be reasonably confident those same genes were operating to produce these features in Quaestio, an animal that has been extinct for more than half-a-billion years.”
A Window into Early Evolution
The discovery not only sheds light on the evolution of movement and body organization but also adds context to how complex life can form — whether on Earth or elsewhere in the universe. It underscores the diversity of life that was already present during the Ediacaran Period, long before the Cambrian Explosion, which is often cited as a time of rapid diversification of life forms.
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“We’re still finding new things every time we dig,” Hughes said. “Even though these were some of the first animal ecosystems in the world, they were already very diverse. We see an explosion of life really early on in the history of animal evolution.”
As paleontologists continue to excavate the vast fossil beds of Nilpena Ediacara National Park, they remain hopeful about uncovering more secrets from Earth’s distant past. Each new discovery adds a piece to the puzzle of how life evolved from simple single-celled organisms to the complex array of animals we see today.
“It’s incredibly insightful in terms of telling us about the unfolding of animal life on Earth,” said Mary Droser, distinguished professor of geology at UC Riverside and Nilpena’s lead scientist. “Studying the history of life through fossils tells us how animals evolve and what processes cause their extinction, be it climate change or low oxygen.”
The findings appeared in the journal Evolution & Development.
