When did animals leave their first footprint on Earth?

Rodiano Bonacci
Giugno 8, 2018

Animals use their appendages or outgrowths to move around, make their homes, feed, and find mates.

They were discovered by researchers from the Nanjing Institute of Geology and Palaeontology from the Chinese Academy of Sciences and Virginia Tech in the United States.

This places them perhaps even 10 million years before the "Cambrian Explosion" (roughly 541 million years ago), the moment in time which sparked the incredible evolution of life that led to the unbelievable diversity of species that we see today. This is considered the earliest animal fossil footprint record. The latest prints date to the Ediacaran period, whose sparse fossil record is populated with soft-tissued creatures including worms and organisms that resembled tiny immobile bags.

Scientists have found fossilised footprints dating from 551 million years ago in China, left in mud by an unknown bug.

Xiao's team found the footprints while tilting rock slabs at different angles.

"We do not know exactly what animals made these footprints, other than that the animals must have been bilaterally symmetric because they had paired appendages", study co-author Shuhai Xiao, a geobiologist from Virginia Tech, told the Independent.

"Previously identified footprints are between 540 and 530 million years old", Dr Zhe Chen from the Nanjing Institute of Geology and Palaeontology told MailOnline.

The trackways are irregular, the scientists found, with two rows of imprints that suggest they were created by a bilaterian animal whose appendages raised it above the ground.

The fossils date to the Ediacaran Period, which was between 635 to 541 million years ago.

The scientists are unsure whether the creature had many legs or just two, and whether it was a member of the arthropod group, which includes bumblebees and spiders, or annelids, which contains modern-day bristle worms.

Also, the trackways appear to be connected to burrows, suggesting that the animals may have periodically dug into sediments and microbial mats, perhaps to mine oxygen and food.

'Arthropods and annelids, or their ancestors, are possibilities.

"But unless the animal died (and preserved) next to its footprints, it is hard to say who made the footprints", he said.

The tracks could be from 10 million years before the Cambrian Explosion, a sudden explosion in biodiversity almost half a billion years ago. This critter was roaming the planet millions of years before the first mammals, the first dinosaurs, and even the first fish.

It ended with the Cambrian-Ordovician extinction event, approximately 488 million years ago.

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