550-million-year-old thingamajig determined to actually be an animal

A mysterious 550-million-year-old fossil that "looks strangely like a ribbed oval" was likely an animal, researchers at the universities of Oxford, Cambridge, Bristol, and the British Geological Survey have found, Science Alert reports. The discovery means that the critter, called a Dickinsonia, predates the Cambrian Explosion of life on Earth, offering compelling evidence for the theory that animals evolved millions of years before the 541-million-year-old benchmark for most known life, The University of Oxford writes.

It took nearly 70 years of research to figure out what exactly Dickinsonia was (some guesses included: a fungus, a lichen, a worm, a jellyfish, a placozoan, and a mushroom). But by studying the growth of Dickinsonia, researchers were recently able to classify it "from a developmental perspective," researcher Alex Liu said.

"When we combined ... growth data with previously obtained information on how Dickinsonia moved, as well as some of its morphological features, we were able to reject all non-animal possibilities for its original biological affinity and show that it was an early animal, belonging to either the Placozoa or the Eumetazoa," added lead researcher Renee Hoekzema.

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Dickinsonia is what researchers call an "Ediacaran biota," one of a group of early organisms that drifted around primordial oceans between 580 and 540 million years ago. The new research "allows Dickinsonia to be considered in debates surrounding the evolution and development of key animal traits," Liu said, and it "will ultimately improve our knowledge of how the earliest animals made the transition from simple forms to the diverse range of body plans we see today." Read more about Dickinsonia at Science Alert.