Imprisoned in rock for millions of years, some dinosaurs do not give up their secrets easily.
Now one of the earliest and most primitive plant-eating dinosaurs has been imaged in the world's largest x-ray machine. Experts described the Heterodontosaurus tucki dinosaur, which has been extinct for 200 million years, as 'amazing'.
The plant eater had 'spare' teeth in its jaw, to replace those worn down by grinding, and delicate features of its skull.
The fossil was found by South African palaeontologist Billy de Klerk, lying in a stream bed near a small town in the Grahamstown's region in 2005.
Together with John Hepple, a technician in Rhodes Geology Department, he excavated the fossil from the stream bed and painstakingly removed enough rock from the bones to identify the specimen.
'A few more years on the streambed and the specimen might have been washed away,' he said, adding 'we just happened to be at the right place at the right time.'
It is the most complete fossil ever discovered of a species known as Heterodontosaurus tucki.
The dinosaur was relatively small, with the species reaching between 3.9 feet (1.1 m) and possibly 5.7 feet (1.75m) in length, weighing between four and 22lbs (two and 10kg).
Despite being in excellent condition, the skeleton is too small and delicate, and the rocks around it too hard, to let palaeontologists get a proper look at its anatomy.
To shed light on the specimen, scientists from the university spent five days at the European Synchrotron Radiation Source (ESRF) in Grenoble, France scanning the complete skeleton of the small dinosaur.
The beamlines, as they are called, offer the unique combination of high-energy, high brilliance and wide X-ray beams necessary to scan large fossils. It's the high coherence of the beam that enables it to contrast the fossilised bones with the surrounding rock, which have similar densities.
Professor Choiniere dubbed the resulting x-ray images 'amazing'.
'Right away when we open these images we can tell quite a few things about the skull,' he explained. 'One of the things is that it's likely a juvenile: the skull bones aren't strongly sutured together.
'We can also tell that we're really able to reconstruct the skull very, very well. On the first scans we can see the openings in the skull, which are for the balance organs.
'We can digitally reconstruct the balance organs of the animal and tell how it held its head and how it interacted with its environment. That's the sort of data you just can't get by looking at a skull in 2D, so it's very exciting.'
It's hoped the study could help the researchers discover how H. tucki move and breathed. Looking at the back of the skull the experts could see the opening where the brain would have sat.
By digitally processing the opening, they can compare the digital brain model with that of modern birds and other dinosaurs.
It could tell them whether the small animals was capable of complex behaviours, for example. The team also studied the dinosaur's teeth and believe its back teeth were used for grinding.
They saw H. tucki had 'spare' teeth inside the jaw to replace grinding teeth that could be worn down. While experts have speculated about tooth replacement in heterodontosaurus, this is the first evidence to confirm their suspicions.
The team was also impressed with the ancient animal's fine palate bones, which measure less than one millimetres across. The fact they are intact suggests the dinosaur has not suffered any head trauma or further damage when it was buried in the rock.