By Paul Rincon
Science reporter, BBC News, Murcia
Giant hyenas, sabretoothed cats, giraffes and zebras lived side by side in Europe 1.8 million years ago.
The creatures' remains were among a vast fossil hoard unearthed at an ancient hyena den in the Granada region of south-east Spain.
The area appears to have been a crossroads where European animals mixed with species from Africa and Asia.
About 4,000 fossils have been found at the unique site. They also include gazelles, wolves, wild boar and lynx.
The dig's co-director, Dr Alfonso Arribas, said the specimens were the remains of carcasses scavenged by giant hyenas (Pachycrocuta brevirostris).
After stripping them of flesh, the hyenas discarded the bones. The scavenged remains were then rapidly buried, explaining their remarkable preservation.
The fossils are currently being exhibited at the Archaeological Museum of Cartagena in Spain.
The Fonelas P-1 site is regarded as extremely important, because it dates to a time - the boundary between the Pliocene and Pleistocene Epochs - when early humans are thought to have first left Africa to colonise Europe and Asia.
So far, Dr Arribas and Guiomar Garrido, from Spain's Geological and Mining Institute, have identified 24 species of large mammal, eight species of small mammal, two reptile species and one species of bird.
Some were previously unknown to science. The brown hyena (Hyaena brunnea) is found today only in the deserts of southern Africa. The discovery of its remains at Fonelas marks the first time the species has been found outside that region.
Sabretooth: The area appears to have been a great wildlife crossroads
At Fonelas, African species like H. brunnea mixed with Asian animals such as Canis etruscus - the ancestor of today's wolf - and a giraffe resembling a modern okapi.
Native European mammals such as the mammoth (Mammuthus meridionalis) and the sabretoothed cat (Megantereon cultridens) are also represented at the site.
The assemblage includes the oldest goat ever found and the earliest badger discovered in Europe.
"These mammals would have inhabited different ecotomes, but they existed in the same time and place," Guiomar Garrido told BBC News.
Gazelle: The dig site records a key period in history
Alfonso Arribas added: "They would have got close enough for their eyes to meet."
The discoveries were presented at the Climate and Humans conference in Murcia, Spain.
African species may have made it to Europe via a number of routes: across the straits of Gibraltar, via Sicily and up through the Levant.
At a different archaeological site in the same region, Arribas and colleagues have excavated stone tools made by primitive humans.
They are currently awaiting the results of magnetostratigraphy dating to determine the age of the site.
The researchers point to similarities between the fauna at Fonelas and those found at the site of the earliest tool makers in East Africa.
Early humans might have been drawn to Europe by the rich diversity of mammals at sites like Fonelas.