Archaeologists have unearthed thousands of bones in an underground cave in Saudi Arabia.
The gruesome graveyard contains bones from humans as well as at least 14 different kinds of animals, including cattle, horses and rodents.
The research team that found the bones has suggested they were carried to the Umm Jirsan cave by hyenas over the past 7,000 years.
The cave is a winding system of lava tubes and volcanic activity has created the hollowed cylinder of rock left behind.
The volcanic fields of Harrat Khaybar are just under one mile long - making it the longest lava tube in the area.
Scientists have been studying the underground system for more than a decade before they analysed the bones found there.
Study author Dr Mathew Stewart from the Max Planck Institute for Chemical Ecology in Germany wrote on Twitter : "This lava tube is chock-a-block with hundreds of thousands of beautifully preserved animal remains."
Dr Stewart and his colleagues analysed the location and frequency of cuts and scratches on the bones in order to find out how the bones got there.
The team concluded the bones were brought in by striped hyena, a species native to the Middle East.
They're said to be avid collectors of bones, which they bring to their dens to be eaten, fed to young, or stored for later use.
Striped hyena skeletal remains and their fossilised poo were also found in the caves, further strengthening their theory.
In 2013, researchers working the cave reported hearing growling sounds, suggesting it was still an active site.
Dr Stewart said cave bones are unusually well-preserved, offering insight into thousands of years of biodiversity.
He tweeted: "The material at Umm Jirsan has accumulated over the last 7,000 years, attesting to the excellent conditions for the preservation of bone within the lava tube.
"In a region where bone preservation is very very poor, sites like Umm Jirsan offer an exciting new resource."
The research was published in Archaeological and Anthropological Sciences.
