Is the Ida fossil the missing link?

If Ida isn't the missing link, why is it important?

Although Ida doesn't quite fit the bill for the way most people use the term "the missing link," it's still an important find. First, it appears to document a previously unknown species, Darwinius masillae. It's the only D. masillae specimen discovered so far, and it's one of a very few primate fossils found in the Messel pit fossil beds.

The fossil is also almost entirely complete. Most animal fossils are highly fragmented -- they're bones, pieces of bones or small portions of skeletons. The D. masillae fossil, on the other hand, is about 95 percent complete [source: Franzen et al]. Even its tiny, delicate bones, like the tips of its toes and tail, are still intact. Only the lower part of one leg and possibly a few tail vertebrae are missing. This means researchers can get a complete look at an animal's entire skeleton instead of having to use knowledge of similar animals to try to fill in gaps.

On top of that, the D. masillae fossil shows the animal's hair and soft tissues, which doesn't happen often. The fossilization process works best on hard tissues, like bone. Hair, skin and other soft tissues usually rot away or are eaten by scavengers before they can harden into stone. But in the case of the D. masillae fossil, the animal most likely fell into a lake created by a volcano crater and was quickly buried in sediment at the bottom, where it was protected from destructive bacteria and predators.

As the material surrounding D. masillae's body hardened, bacteria left a dark stain. This dark stain essentially paints a picture of the animal's soft tissue and hair in the oil shale that surrounds the fossilized bones today. This gives researchers a much clearer idea of what the animal actually looked like, how its muscles were situated and how it moved. The level of detail even extends to the animal's stomach, which contains remnants of its last meal -- fruit and leaves.

Much like the dinosaur fossil known as Leonardo, the D. masillae fossil gives scientists a lot of information to work with -- and some research challenges. Both fossils are embedded in stone, and removing them from the rock would destroy them. That's why researchers used numerous imaging techniques to get clear pictures of D. masillae to study. Some of the technologies include digital X-rays, CAT scans and mammography.

Together with analysis of both halves of the fossil and comparisons to other fossil specimens, these images have allowed scientists to draw several conclusions about the fossil. And those conclusions -- while they don't quite make D. masillae the missing link -- have an importance all their own.