Earth’s First Animals Are These Bizarre Leaf-Like Creatures That Are 500 Million Years Old

Half a billion years ago, the Earth and the life forms found in the planet were very, very different from what they are now.

During the Ediacaran Period 635 to 542 million years ago, bizarre Ediacaran organisms were king of the seas. These funny-looking life forms are crucial in piecing together the origins of life on Earth, because they came just before the event called the Cambrian explosion, which first introduced the precursors of many existing animal groups today.

Scientists had little idea of the nature of these Ediacaran organisms, but now researchers Jennifer Hoyal Cuthill of the Tokyo Institute of Technology and the University of Cambridge and Jian Han of Northwest University finally offer a definitive answer.

A New Set Of Prehistoric Animals Introduced

In research published in the journal Palaeontology, a team of researchers reveal that these strange, unrecognizable creatures can be classified as animals. This means that these Ediacaran organisms are the first animals on Earth.

Science Magazine reports that about 200 different types of Ediacaran organisms have been unearthed all over the world since the first one was discovered in South Australia's Ediacara Hills in 1946. Nearly all were found to have died out at the cusp of the Cambrian explosion around 541 million years ago.

Despite the volume, it still proved to be difficult to place the ancient creatures in part due to some species' anatomy that's alien to nature as humans know it.

An Animal That's Also An Ediacaran Organism

For the new study, researchers analyzed over 200 fossils of a 518-million-year-old marine species known as Stromatoveris psygmoglena.

It has been previously named an animal by paleontologists, and now Hoyal Cuthill and Han say that the Stromatoveris is an Ediacaran organism as well. They suggest that unlike other Ediacarans, they were able to survive into the Cambrian explosion.

It was while the pair was examining the Stromatoveris fossils that they noticed something, Hoyal Cuthill tells Science Magazine, adding that the species' features resemble some Edicaran organisms with distinct branched fronds and a fractal internal structure.

The duo also realized that the Stromatoveris and the other Ediacaran organisms don't belong to any living animal group or phylum.

"This branch, the Petalonamae, could well be its own phylum, and it apparently lacks any living descendants," Hoyal Cuthill explains.

What The Discovery Means For Evolution

The classification of these 500-million-year-old creatures as animals means they're the first animals to appear in the planet and the origin of the animal kingdom needs to be pushed back to the time of the oldest Ediacaran fossil, according to The Conversation.

It also means that those who are searching for the origins of animal life would need to focus on an earlier time period than the Cambrian explosion.

The classification of the Stromatoveris as an animal also means that not all Ediacaran organisms were wiped out in the Cambrian explosion. After all, many believe that their extinction was brought about by the introduction of animals.

Now that Ediacaran biota are named as part of the animal kingdom, the mystery shifts: why did they go extinct and why were they unable to spawn surviving descendants?