New Study Sheds Light on Earth’s First Animals

Credit: UCR

To study Dickinsonia, the researchers travelled to South Australia’s desert outback, which was once underwater and is now home to an abundance of Ediacaran fossils. They measured the size, shape and structure of almost 1,000 specimens of Dickinsonia costata, paying attention to the number and size of the modules. The work was done in collaboration with James Gehling of the South Australian Museum in Adelaide, Australia, who is a coauthor on the paper.

The study showed that Dickinsonia’s development, and particularly that of the modules, was complex and systematic to maintain the oval shape of the animal. The accumulation of new modules, by a process called terminal addition, suggests that Dickinsonia developed in a related way to bilaterians, a complex group that display bilateral symmetry, including animals ranging from flies and worms to humans. However, the researchers do not believe Dickinsonia was ancestrally related to bilaterians, since it lacked other features that most bilaterians share, most notably a mouth, gut and anus.

“Although we saw some of the hallmark characteristics of bilateral growth and development, we don’t believe Dickinsonia was a precursor to today’s bilaterians, rather that these are two distinct groups that shared a common set of ancestral genes that are present throughout the animal lineage,” Evans said. “Dickinsonia most likely represents a separate group of animals that is now extinct, but can tell us a lot about the evolutionary history of animals.”

The title of the paper is “Highly Regulated Growth and Development of the Ediacara Macrofossil Dickinsonia Costata.” The study was supported by the National Science Foundation and the National Aeronautics and Space Administration Exobiology.

Contacts and sources:
Sarah Nightingale