Jorn Hurum, of the University of Oslo Natural History Museum, led the investigation of the fossil's significance.
"[Ida] is the first link to all humans ... truly a fossil that links world heritage ... the closest thing we can get to a direct ancestor"
Jorn Hurum, paleontologist
He said the fossil shows characteristics from the very primitive non-human evolutionary line, but is more related to the human evolutionary line (anthropoids, such as monkeys, apes and humans).
However, she is not really an anthropoid either, he said.
The fossil, called Darwinius masillae and said to be a female, provides the most complete understanding of the paleobiology of any primate so far discovered from the Eocene Epoch, Hurum said.
The female animal lived during an epoch in Earth history known as the Eocene, which was crucial for the development of early primates - and at first glance, Ida resembles a lemur.
He described the discovery as "a dream come true" and said it was "the closest thing we can get to a direct ancestor".
"This is the first link to all humans ... truly a fossil that links world heritage," he said.
Some independent experts, awaiting an opportunity to examine the new fossil, are sceptical of the claim.
Ida was discovered in the 1980s in a fossil-rich area called Messel Pit, near Darmstadt in Germany and has been held in a private collection.
|Experts are somewhat sceptical of 'missing link' claims [AFP]
The scientific team concluded that she was not simply another lemur, but a new species.
They have called her Darwinius masillae, to celebrate her place of origin and the bicentenary of the birth of Charles Darwin.
Jens Franzen, an expert on the Messel Pit, described Ida as "like the Eighth Wonder of the World", because of the extraordinary completeness of the skeleton.
It was information "palaeontologists can normally only dream of", he said.
In addition, Ida bears "a close resemblance to ourselves" he said, with nails instead of claws, a grasping hand and an opposable thumb - like humans and some other primates.
But Franzen said some aspects of the teeth indicate she is not a direct ancestor - more of an "aunt" than a "grandmother".
"She belongs to the group from which higher primates and human beings developed but my impression is she is not on the direct line."
Chris Beard, curator of the Carnegie Museum of Natural History, said he was "awestruck" by the publicity surrounding the new fossil.
"I would be absolutely dumbfounded if it turns out to be a potential ancestor to humans."
But he said that Ida would be "a welcome new addition" to the world of early primates.