It may have been "a complete fluke", but some United Kingdom scientists believe the discovery of a giant fossil at an English beach has unearthed the world's biggest-ever bug.
The fossilised partial remains of an extinct millipede — also known as Arthropleura — was detected when a block of sandstone was cleaved in two at Howick in Northumberland.
When the sandstone opened up, the exposed fossil revealed a millipede believed to have been around 2.5 metres long — more than 25 times longer than the average centipede.
It dates back to the Carboniferous Period, 326 million years ago, around 100 million years before dinosaurs inhabited the Earth.
The fossil, measuring 75cm, will go on display at Cambridge's Sedgwick Museum next year.
The Journal of the Geological Society has just published a paper analysing "the largest arthropod in Earth's history".
"It was a complete fluke of a discovery," Neil Davies, from the department of earth sciences at the University of Cambridge, told the ABC.
"We were visiting the beach to look at the general geology, and we saw a boulder had recently fallen from the cliff and split in two.
"We found the fossil inside this crack, but the location is not known for fossils … our timing was lucky."
With a width of 55cm, and an estimated weight of more than 50 kilograms, the millipede would have been the largest invertebrate — an animal without a backbone — ever recorded.
"The closest competitor is a Devonian sea scorpion from Germany, but this one is at least 10cm longer."
Only the third Arthropleura fossil to have been unearthed, it is considered more significant than the two previous discoveries, both in Germany.
Unlike most bugs, Arthropleura are believed to have supplemented a traditional diet of seeds and nuts by eating other animals to maintain their significant girth.
Researchers estimate the chunky millipedes had between 32 and 64 legs.
Dr Davies said the discovery gave researchers more of an idea of how the first animals and plants occupied the land and interacted with each other.
"It also goes to show that there are loads of things out there to discover," Dr Davies said.
However, Dr Davies admits that some questions will remain unanswered about the coastal-loving creatures who lived at a time when the UK is believed to have enjoyed much warmer weather.
"We have not yet found a fossilised head, so it's difficult to know everything about them," he said.
