Scientists have revealed the first near-complete skeleton of a 66 million-year-old mammal which lived among dinosaurs.
A study into the fossils was released to Nature on Wednesday which shows the mammal resembled a badger with its long torso and stubby tail.
The fossil was found in Madagascar in 1999 by scientist Dr David Krause but was only officially named on Wednesday.
Scientists have called the mammal Adalatherium hui which means 'crazy beast' in Malagasy and Greek.
Dr Alistair Evans, who was part of the team who studied the fossil's teeth, said the fossil was unprecedented.
"We could never have believed we would find such an extraordinary fossil of this mysterious mammal," he said.
"This is the first real look at a novel experiment in mammal evolution.
"It has taken 20 years to study in detail every aspect of the fossil, to show what type of mammal it was and how it likely lived in its ecosystem."
The mammal would have lived during the Cretaceous Period and was part of a group of mammals called gondwanatherians, which were named after the supercontinent Gondwana.
Previous fossils from the group have only contained teeth so the new fossil has helped the scientists understand how they looked.
Originally mammals in the period were only thought to be the size of mice to help them survive amongst the dinosaurs, but the fossil has been compared to the size of a cat.
Scientists estimated it weighed around 3kg, but had not yet reached its full adult size.
They believe it's large claws and robust legs would have allowed it to burrow into the earth to avoid predatory creatures and Evans compared it to Australian marsupials.
The study's lead author David Krause said the mammal was "outlandish".
The mammal has a strange snout, the teeth were different to anything they had ever seen before, it's backbone had more vertebrae than any other Mesozoic, and one of its leg bones was oddly curved.
"Its many uniquely bizarre features defied explanation in terms of relationships to other mammals. In this sense, it was a 'crazy beast,'" he told Reuters.
Gondwanatherians were first thought to be related to sloths, anteaters, and armadillos but "now are known to have been part of a grand evolutionary experiment, doing their own thing, an experiment that failed and was snuffed out in the Eocene, about 45 million years ago," Krause said in a press release.
"Knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal-like Adalatherium could have evolved; it bends and even breaks a lot of rules."
But he says there is still a lot to learn about the animals and they hope more fossils will be discovered.
"Adalatherium is just one piece, but an important piece, in a very large puzzle on early mammalian evolution in the southern hemisphere," Krause says. "Unfortunately, most of the pieces are still missing."
