The oldest known animal predator has been uncovered in Leicestershire

The earliest known animal with a skeleton has been discovered in Leicestershire, UK.

The new species, Auroralumina attenboroughii, was discovered in Charnwood Forest, a site which has long been recognised for its scientifically important fossils. A. attenboroughii is thought to be one of the first cnidarians, a group including coral and jellyfish, and dates back over 560 million years.

The lead author of a paper describing its fossil, Dr Frankie Dunn, says, 'This is very different to the other fossils in Charnwood Forest and around the world.'

'Most other fossils from this time have extinct body plans and it's not clear how they are related to living animals. A. attenboroughii, however, clearly has a skeleton with densely packed tentacles that would have waved around in the water capturing passing food, much like corals and sea anemones do today.'

'It's nothing like anything else we’ve found in the fossil record at the time.'

Scientists hope that the discovery will be the first of many revealing what the earliest animal life would have looked like.

The description of the fossil was published in Nature Ecology and Evolution. 

What is the Ediacaran Period?

The Ediacaran is a period of history which lasted from around 635 to 540 million years ago. During this time, life evolved from simple multicellular structures such as microbial mats and into more complex forms.

For instance, Ikaria wariootia is one of the earliest known bilaterians, which are animals possessing a head, tail and gut. It is also one of the first species thought to have burrowed, based on the shape and size of preserved tunnels found nearby.

While the Ediacaran is recognised as an important point in the evolution of life on Earth, it tends to be overshadowed by the following geological period, the Cambrian. In particular, the Cambrian Explosion is when most modern animal groups begin to appear in the fossil record and organs such as eyes first evolve.

This is primarily due to the evolution of hard skeletons, which became widespread during this time. Mineralised structures like skeletons are much easier to fossilise than soft-bodied organisms like those found in the Ediacaran.

Instead, scientists often have to turn to other ways of researching these soft-bodied organisms. For instance, the presence of ancient sea sponges over 600 million years ago has been inferred by the presence of fossilised molecules preserved in rocks. 

In some rare circumstances, however, the structure of soft-bodied organisms can be preserved. Some species can become mineralised in low-oxygen water by a process known as secondary phosphatisation, allowing them to fossilise.

A soft-bodied organism might also leave an impression after its body is pressed into a malleable substance.

The latter is what happened to Auroralumina attenboroughii, which is believed to have been swept up in an ancient volcanic eruption which led to its preservation. It is thought to have lived in shallower waters than the fossils it is now surrounded by.

'The ancient rocks in Charnwood closely resemble ones deposited in the deep ocean on the flanks of volcanic islands, much like at the base of Montserrat in the Caribbean today,' Frankie explains. 

'All of the fossils on the cleaned rock surface were anchored to the sea floor and were knocked over in the same direction by a deluge of volcanic ash sweeping down the submerged foot of the volcano, except for A. attenboroughii.'

'It lies at an odd angle and has lost its base, so appears to have been swept down the slope in the deluge.' 

How was the earliest animal predator discovered?

The fossil of A. attenboroughii was discovered in rocks once presumed to be so old that they predated the existence of life itself. However, this changed in the 1950s, when a fossil called Charnia masoni was discovered by Tina Negus.

However, her discovery was not widely appreciated, and the fossil was rediscovered by Roger Mason in 1957. This led to the description of the species, and a greater appreciation of life in the Ediacaran.

Researchers continue to investigate the area's fossils, and in 2007, scientists from the British Geological Society cleaned the rock surrounding the discovery site of C. masoni and took a mould of the rock's surface. 

Their investigation revealed the presence of A. attenboroughii, whose scientific name translates as Attenborough's dawn light. It was named after Sir David Attenborough as the naturalist and presenter has raised awareness of Charnwood Forest's fossils.

It pushes the history of predation as a way of life back by around 20 million years, with the scientists believing it may have fed on algae, zooplankton and small protists. The fossil is thought to represent a stem medusozoan, making it a relative of the ancestors of modern jellyfish. 

Modern jellyfish metamorphose from an immature sessile stage anchored to the floor into a sexually mature medusa with tentacles trailing behind a bell-shaped body. A. attenboroughii appears similar to jellyfish in their sessile stage, but it is currently unclear whether it had the ability to transform. 

As A. attenboroughii is significantly bigger than modern jellyfish, it may have been unable to do so, and the medusa stage of the cnidarian lifecycle may have evolved later. It may have proved a stepping stone between the Ediacaran and the Cambrian, as its shape is similar to fossils from the latter period.

Scientists hope that rocks of similar ages in the UK and around the world will contain more fossils that could help reveal the origins of the different animal groups we know today.

'Our discovery shows that the body plan of the cnidarians was fixed at least 20 million years before the Cambrian Explosion,' Frankie says. 'It’s hugely exciting and raises many more questions for the future.'