New species of rare ancient worm discovered in fossil hotspot

A team of researchers including Leicester’s Professor David Siveter have discovered a new species of lobopodian, an ancient relative of modern-day velvet worms, in 430 million-years-old Silurian rocks in Herefordshire, UK.

Researchers from the universities of Oxford, Yale and Leicester and Imperial College London, have been carrying out fieldwork at the locality in Herefordshire since the mid-1990s. It is now recognised as a fossil site of global importance.

They have been able to three-dimensionally reconstruct the exceptionally well-preserved fossil using digital technology, and their research is reported in the Royal Society journal Open Science.

The sedimentary deposit in which it was discovered has since become known as the Herefordshire Lagerstätte, the term Lagerstätte indicating that it contains exceptionally preserved fossilised remains of the soft-parts animals and/or entirely soft-bodied animals.

The ‘worm’ from Herefordshire and its animal associates lived 430 million years ago within a marine basin that extended across what is now central England into Wales, and they are preserved in nodules in a soft, cream-colored volcanic ash mixed with marine sediment.

Professor David Siveter comented that “This fossil is exciting because it preserves an entirely soft-bodied animal in high fidelity and is of a group that in general is rare in the fossil record. It offers unique insight into their palaeobiology, geological history and evolution and enhances our understanding of the tree of life”.

First author Derek Siveter, Professor Emeritus of Earth Sciences at Oxford University and Honorary Research Associate at Oxford University Museum of Natural History, said: “Lobopodians are extremely rare in the fossil record, except in the earlier, Cambrian Period of geological time. Worm-like creatures with legs, many are an ancestral marine relative of modern-day velvet worms, or onychophorans - predators that live in vegetation, mainly in southern latitudes.

“This new lobopodian, which we have named Thanahita distos, was discovered during fieldwork in an area of Silurian rocks in Herefordshire. It is the first lobopodian to be formally described from rocks of Silurian age worldwide; exceptionally, it is fully three-dimensionally preserved, and it represents one of only eight known three-dimensionally preserved lobopodian or onychophoran fossil specimens.

“We have been able to digitally reconstruct the creature using a technique called physical-optical tomography. This involves taking images of the fossil at a fraction of a millimetre apart, then "stitching" together the images to form a "virtual fossil" that can be investigated on screen.”

The work was funded by the Natural Environment Research Council (NERC) and the Leverhulme Trust.