‘Extremely Rare’ 430-Million-Year-Old Worm-Like Fossil Found In Herefordshire

This newfound ancient critter is a distant relative of the velvet worm.

Velvet worm (Onychophora).
Pedro Bernardo / Shutterstock

This newfound ancient critter is a distant relative of the velvet worm.

British researchers have stumbled upon a previously unknown species of lobopodian, an ancient worm-like creature dating back 430 million years ago, to the Silurian Period.

The new species is a distant relative of the modern-day velvet worm (Onychophora, imaged above) and has been identified from an “exceptionally well-preserved fossil” — one of a handful of lobopodian fossils to be conserved in a fully three-dimensional state, reports the University of Oxford.

Dubbed Thanahita distos, the new lobopodian species was unearthed from a famous paleontological site in Herefordshire, U.K., and is described in a study just published in the journal Royal Society Open Science.

What’s remarkable about Thanahita distos is that it’s the very first lobopodian fossil to ever be retrieved from Silurian rocks, and the eighth to be discovered after it was three-dimensionally preserved.

Another interesting about this fossil is that, although it was found encased in 430-million-year-old rocks, it actually belongs to a much older group of lobopodians that emerged 100 million years before the Silurian, during the Cambrian Period — some 520 to 510 million years ago.

“Lobopodians are extremely rare in the fossil record, except in the Cambrian Period,” said study lead author Derek Siveter, Professor Emeritus of Earth Sciences at Oxford University and a researcher at the Oxford University Museum of Natural History.

According to Siveter, these worm-like creatures were ancient marine critters, some of which went on to spawn the velvet worms we see today, while others gave rise to modern-day arthropods, such spiders and crustaceans.

With the help of a technique called physical-optical tomography, Siveter’s team was able to make a computer reconstruction of Thanahita distos so that we can see what this ancient sea-dweller looked like.

As Siveter explains, the technology “involves taking images of the fossil at a fraction of a millimeter apart, then ‘stitching’ together the images to form a ‘virtual fossil’ that can be investigated on screen.”

Thanks to their efforts, we now know that the newfound lobopodian had nine pairs of legs, or appendages, which ended with claws — either two claws or single one.

This predatorial creature likely lived in the dark depths of the sea, “below the depth to which much light penetrates,” judging by the lack of photosynthetic algae traces in the rocks where the fossil was found.

Recovered from a sedimentary deposit known as the Herefordshire Lagerstätte, which yielded a treasure trove of fossils in the past and is renowned for harboring impeccably conserved remains of soft-bodied animals, the Thanahita distos fossil was preserved in “special circumstances.”

The fossil was discovered in what Siveter calls a Silurian “time capsule” — a nodule-like mold formed around the animal by clay mineral deposited almost immediately after death. Once those original minerals decomposed, the mold was filled with calcite, which helped cement the fossil inside the capsule and safely preserve it after it got buried under volcanic ash.

“Since its discovery, the Herefordshire Lagerstätte has yielded a diversity of arthropods that have contributed much to our understanding of the paleobiology and early history of this very important invertebrate group,” said Siveter.