Quaestio simpsonorum is part of the Ediacara Biota, which preserves the oldest evidence for complex, macroscopic animals.
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Close up of Quaestio simpsonorum footprint. Image credit: Evans et al., doi: 10.1111/ede.12491.
Quaestio simpsonorum is one of more than 100 multicellular organisms from the Ediacaran period (635 to 538 million years ago), when the first complex, macroscopic animals emerged on Earth.
This creature was up to 8 cm (3.1 inches) wide and likely moved along what was once the seafloor.
Because no animals had yet evolved to burrow through the sediment, this seafloor was covered in a layer of microorganisms that created a slimy organic mat.
“Quaestio simpsonorum had some interesting features that made it stand out from other Ediacaran species,” said University of California’s Professor Mary Droser.
“What is really exciting about this fossil is that it’s basically bilaterally symmetrical, which means its right side mirrors its left side, but then it has an asymmetrical element that forms the shape of a backwards question mark.”
“This sort of symmetry indicates a certain level of genetic complexity.”
“Humans are bilaterally symmetrical but have a number of asymmetries, for example the location of the heart and appendix.”
“A number of other such asymmetries are found throughout the animal kingdom — this appears to be one of the first organisms to organize itself in that way.”
An artist’s reconstruction of Quaestio simpsonorum. Image credit: Walker C. Weyland.
More than a dozen specimens of Quaestio simpsonorum were unearthed at Nilpena Ediacara National Park in South Australia.
“Unique trace evidence uncovered by our team suggests that Quaestio simpsonorum ate the ancient organic mat as it moved along,” said Florida State University’s Professor Scott Evans.
“It really speaks to the unprecedented nature of the fossil record at Nilpena to have fossils preserved directly alongside evidence of their behavior — in this case showing us how an animal that went extinct half a billion years ago got its food.”
“Nilpena is a site of huge international significance and there really is nowhere else like it in the world,” said Stuart Paul, director of regional operations at National Parks and Wildlife Service.
“As well as learning about these amazing fossils out in the park, tourists can also visit the former blacksmith’s shop where one of the fossil beds is brought to life by an impressive, interpretive display with audio visual reconstructions of what these organisms looked like and how they behaved.”
The findings were published in the journal Evolution & Development.
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Scott D. Evans et al. A new motile animal with implications for the evolution of axial polarity from the Ediacaran of South Australia. Evolution & Development, published online September 3, 2024; doi: 10.1111/ede.12491
