Scientists in Central Australia say the discovery of a prehistoric claw at a fossil deposit is baffling.

The claw is about seven centimetres long and was found at the Alcoota Scientific Reserve, about 160 kilometres north east of Alice Springs.

The reserve is home to the largest and most concentrated fossil deposit of its kind in Australia and scientists say bones at the site could be millions of years old.

Dr Adam Yates from the Museum of Central Australia has told the ABC's Country Hour the claw may belong to a reptile.

"We don't know what animal this comes from," he said.

"Similar claws have been found in the past and they've been suggested to have come from a large goanna.

"That's a pretty big goanna.

"We're looking at something much bigger than a modern komodo dragon, so a really giant goanna.

"But we haven't found any other bones that we can attribute to a goanna of that size, so really we're scratching our heads."

The specimen will be brought to the Museum of Central Australia in Alice Springs for analysis.

Dr Yates says the team has dug up plenty of other fascinating specimens, including the shin bone of a giant flightless bird called dromornis stirtoni.

"It was three metres tall, weighing about half a tonne.

"It's quite probably the largest bird that ever lived."

Dr Yates believes the site is evidence of a mass extinction event.

"We think all these animals died at the same time, around a waterhole during a really nasty drought."