World's Oldest Footprints Discovered on Ancient Seafloor
Neil Armstrong left the first footprint on the moon, on July 20, 1969.
But what about Earth — when did animals first leave footprints here?
While we don't know exactly when animals first left tracks on our
planet, the oldest footprints ever found were left between 551 million
and 541 million years ago during the Ediacaran period,
a new study finds. That's hundreds of millions of years before
dinosaurs started roaming Earth, about 245 million years ago. The new
findings suggest animals evolved primitive "arms" and "legs" earlier
than previously thought.
The odd-looking prehistoric trackways show two rows of imprints that
resemble a series of repeated footprints, the researchers said. The
scientists found the trackways in the Dengying Formation, a site in the
Yangtze Gorges area of southern China. [Image Gallery: 25 Amazing Ancient Beasts]
The trackways' characteristics indicate that a bilaterian animal — that
is, a creature with bilateral symmetry that has a head at one end, a
back end at the other, and a symmetrical right and left side — made the
tracks. This sea-dwelling animal had paired appendages that raised its
body above the ocean floor, the footprints left behind by its multiple
feet suggest.
These footprints are located next to fossilized burrows. This means
that the mystery animal might have periodically dug into the ocean
floor's sediments and microbial matts, possibly to mine for oxygen and
food, the researchers said.
Both the footprints and the borrows
are known as "trace fossils," a term that refers to fossilized remnants
that animals leave behind, such as fossilized poop, rather than fossils
of the animals themselves. The newfound trace fossils are some of the
earliest known evidence for animal appendages on record. Until now, it
was thought that bilaterian animals, such as arthropods and annelid
worms, first appeared during the Cambrian explosion, between 541 million and 510 million years ago, although some scientists suspected that these animals evolved earlier.
The study was published online today (June 6) in the journal Science Advances.
Original article on Live Science.
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