A peculiar armored worm with bundles of spiky bristles on its sides crawled the Earth more than half a billion years ago, fossils unearthed in China reveal.
The bizarre creepy crawly was also covered in dense plates on its back that overlapped in a regular pattern.
The stocky creature, named Wufengella, was only an inch long and segmented like an earthworm.
It had a fleshy body with a series of flattened lobes projecting from the sides and belonged to an extinct group of shell-like organisms called tommotiids, experts say.
They added that the discovery sheds light on the evolution of three major groups of living animals.
A peculiar armored worm with bundles of spiky bristles on its sides crawled the Earth more than half a billion years ago, fossils unearthed in China reveal. It is depicted in an artist’s impression
Co-author Dr Jakob Vinther, from the University of Bristol, said: ‘It resembles the unlikely progeny between a bristle worm and a chiton mollusk. Interestingly, it doesn’t belong to either group.’
The animal kingdom is made up of more than 30 major body plans called phyla – each with a set of specific characteristics.
Only a few are shared by more than one group, which is evidence of their very rapid evolution.
They originated during a period known as the Cambrian Explosion, about 550 million years ago.
Co-author Dr. Luke Parry of the University of Oxford added: ‘Wufengella belongs to a group of Cambrian fossils crucial to understanding how lophophorates evolved.
“They are called tommotiids, and these fossils have allowed us to understand how brachiopods evolved into two ancestral shells with many shell-like plates arranged in a cone or tube.”
Brachiopods are a tribe that superficially resembles bivalves – such as mussels – in having a few shells. They live attached to the seabed, rocks or reefs.
The stocky creature, named Wufengella, was only an inch long and segmented like an earthworm. It had a fleshy body with a series of flattened lobes projecting from the sides and belonged to an extinct group of shell-like organisms called tommotiids, experts say.
But their interior is very different in many ways. In fact, brachiopods filter water using a pair of tentacles folded into a horseshoe-shaped organ.
It is called a lophophore and is shared with horseshoe worms or ‘phoronids’ and moss animals known as ‘bryozoans’.
Pedigrees using amino acid sequences match anatomical evidence that all three are each other’s closest living relatives — collectively named as Lophophorata after their filter-feeding organ.
Scans show that Wufengella, which is 518 million years old, a complete camenellan tommotiid and reveal what the long-sought ancestor looked like.
dr. Parry said: ‘When it first became clear to me what this fossil was that I was looking at under the microscope, I couldn’t believe my eyes. This is a fossil we’ve often speculated about and hoped we’d see one day.”
The fossil fulfills the paleontological prediction that the ancestral lineage of the lophophorates was an agile, armored worm.
The soft anatomy also brings into focus ideas on how lophophorates may be related to segmented worms.
Experts say the discovery sheds light on the evolution of three major groups of living animals
dr. Vinther said: ‘Biologists have long noted how brachiopods have multiple, paired body cavities, unique kidney structures and bundles of bristles like larvae on their backs.
‘Through these similarities, they noticed how closely brachiopods resemble annelids.
“We can now see that those similarities are a reflection of shared ancestry. The common ancestor of lophophorates and annelids had an anatomy most similar to annelids.
‘At some point, the lophophorates’ tommotiid ancestor became sessile and evolved suspension feeding (catching particles suspended in the water).
“Then a long, worm-like body with countless repeating body units became less useful and became smaller.”
Co-author Greg Edgecombe, of the Natural History Museum, added: “This discovery shows how important fossils can be for reconstructing evolution.
‘We get an incomplete picture by looking only at living animals, with the relatively few anatomical features shared between different phyla.
“With fossils like Wufengella, we can trace each lineage back to its roots, realizing how they once looked very different and had very different ways of life, sometimes unique and sometimes shared with more distant relatives.”
The new research is published in the journal Current Biology.
WHAT WAS THE ‘CAMBRIAN EXPLOSION’?
Scientists have long speculated that a large oxygen spike during the ‘Cambrian explosion’ was key to the development of many animal species.
The Cambrian explosion, about 541 million years ago, was a period when a wide variety of animals appeared on the evolutionary scene.
Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized into colonies.
Over the next 70 or 80 million years, evolution accelerated and the diversity of life began to resemble that of today.
It ended with the Cambrian-Ordovician extinction, about 488 million years ago.