The image shows Darwinius masillae X-ray image (left) and embedded on a resin slab (right) © Franzen et al.
Ida is so well-preserved that scientists can study the visible parts of her fossil quite easily.
They also used X-rays and CT scans to examine the fossil. These methods combined with high resolution images, meant they could study the developing teeth, some of which were not visible on the surface of the fossil. These techniques were particularly important as the skeleton is lightly crushed and the bones cannot be handled individually.
Scientists made detailed measurements of the dimensions of the fossil using calipers and a binocular microscope. These measurements, together with the CT scans and X-ray images, enabled them to compare the proportions of Ida's features with other primate specimens and also with animals alive today.
Comparing Ida with modern species meant that scientists could estimate the age of Ida at her death and what her expected life span would have been if she had lived to old age.
They were also able to compare Ida with other adapoid primate finds from Messel and from another German site, Geiseltal, such as Europolemur kelleri, E. koenigswaldi and Godinotia neglecta. However, none of these fossils is as complete as Ida.
Skeleton - This is complete apart from the lower part of the left hind leg and foot. It was lightly crushed by over-lying rock.
Skull - Because of compaction, the bones, especially the skull, have been slightly distorted. This meant that scientists had to treat their measurements with caution when comparing them with those of other finds.
Eyes - The size of the eye sockets are relatively large compared to the size of the skull showing that she was probably nocturnal.
Tail - Darwinius did not have a prehensile tail (capable of grasping) so she probably used her tail for balance or steering when leaping. The soft body contours of the tail are not preserved so we cannot tell if it was bushy or not.
Legs - Both fore and hind limbs are shorter than in contemporary relatives and, along with the soft body outline, suggest stronger muscles. The missing parts of the left leg were probably lost during excavation as there are no signs of damage to indicate that she was bitten or scavenged.
Stomach - Analysis shows that the contents of the gut include leaves and a fruit but no insects. This is consistent with the size of the animal and the structure of her teeth. Knowing what the creature ate and what her last meal was is valuable evidence that helps us build a picture of how she may have lived.
Lower jaw - The area where the two bones join is not fully fused. This is one of the clues, discovered by examining CT scans, which show that Ida was a juvenile. Crucially she does not have a toothcomb in the lower jaw, a feature that lemurs, lorises and bushbabies share.
Teeth - The presence of milk teeth and newly erupting permanent teeth revealed in the CT scans and X-ray images, indicate that Ida was a weaned juvenile about 9 months old. The shape of the teeth are distinct when compared with other extinct primate species.
Wrists and hands - The right wrist shows a fracture that has partially healed and may have been responsible for her demise. Examining the structure and shape of the bones shows that Ida had opposable thumbs and big toes and she had nails rather than claws on all fingers and toes.
Ankle and foot bones - The steepness of the outer side of Ida's ankle bone is a feature shared with tarsiers, monkeys, apes and humans, but not with lemurs, lorises and bushbabies. A small bone in the foot called the mesocuneiform is broad and triangular in shape, whereas it is narrow in lemurs, lorises and bushbabies. The structure of ankle and foot bones is important as it is associated with locomotion in the trees.