We all know about fossils that catch the eye - dinosaur skeletons that make the headlines, intricate shells entombed in polished slices of rock and even scatterings of petrified ancient teeth. Dr Paddy Orr and his team use modern technology to put flesh on the bones and build up a bigger picture of life on earth many millions of years ago. His lab’s discoveries include insights into ancient amphibian muscles and dinosaur feathers.
“We work on absolutely anything that is a little bit odd,” says Dr Orr, referring to the eclectic mix of animals and environments that have fallen under the gaze of his lab since he came to the UCD School of Geological Sciences in 2003.
“Most of the fossil record is made up of the hard parts of organisms, the bones, shells and teeth, the bimineralised tissues, and out of that you tend to simply get isolated bones, or if you have a multi-element skeleton you get disarticulate, separate elements,” he explains.
“But we look at exceptionally preserved fossils, like when you get articulated skeletons for vertebrates for example, or when you get soft tissue that would normally decay very rapidly.”
Artist's impression of two Sinosauropteryx - Feather-like structures in fossils of the dinosaur suggest it had reddish-brown and white tail stripes. Image: Chuang Zhao and Lida Xing
Much of the research hinges on relatively new, non-destructive techniques in microscopy that can identify and analyse tiny segments of fossil and highlight features that would previously have been overlooked.
“From a biological point of view they are little goldmines.”
Those new approaches include being able to get up close and very personal with the surface of a specimen by putting it directly into the scanning electron microscope (SEM) without the need to preserve the fossil first, explains Orr.
Then a method called “ion beam milling” allows the scientist take a tiny sliver of an interesting portion that they can go on and examine in minute detail under the transmission electron microscope (TEM).
The integrated processes mean the scientist can get the required information and still hand the precious specimen back to a curator without any visible damage to it, explains Dr Orr.
“The museums are fantastic archives of this information and the material we look at might be 100 or 120 years in the collection and now the technology means it can be analysed,” he says. “You can see the value of material that’s archived, often from sites that no longer exist.”
During his PhD work at Bristol University, Orr became interested in using microscopy to examine soft tissues and how they may be preserved. Fossils from specific environments where soft tissues are preserved to some degree can help flesh out the evolutionary record and also provide clues about the kind of ecosystems in which the animals and plants found themselves when they were alive, explains Orr.
His lab has turned up, and contributed to, landmark discoveries from such treasures, including images of preserved muscle fibres in frogs and salamander fossils from lake beds in Spain dating from between 10 and 17 million years ago.
“These are the first examples of fossilised bone marrow and musculature as organic remains,” says Orr, noting that at a molecular level there could await even more discoveries. “The importance of [biomolecules] in the geological record hasn’t been fully appreciated until the last few years, largely because of what we turned up.”
“There were these two competing models as to what these elongate fibrous stuctures were - they were either the proto-feathers, as many people believed, or they were collagen fibres from within the skin,” explains Orr. “We thought if they are feathers then the key thing they should have is little pigment bodies or melanosomes.”
On inspection, the international team from the University of Bristol, UCD, the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing, and the Open University found not one but two types of melanosomes in the specimens, coming down heavily on the ‘feather’ side of the argument, and they compared the rounded and sausage-shaped pigment bodies with those from a modern species of zebrafinch.
“Their approach also helped solve a mystery of fibres found on 125-million-year old fossil samples from China. ”
The proof-of-concept study suggested that dinosaurs may have had different coloured feathers, and Orr’s group now hopes to study further the distribution of the pigment body types to build up a better understanding of the animals’ appearance and the function the feathers may have had.
“We know that feathers evolved before flight, so their primary function must have been something else, and you can probably start to constrain what the functions would have been if you can understand the absolute colours but also the patterning, which I think is as critical; the patterning can break up the line of an animal or is can be something that screams ‘I’m here come get me’.”
As Orr’s lab continues to examine both the processes of soft-tissue preservation in fossils and the kinds of clues it can yield, he stresses that if you look in the right places there are rich pickings in the field that will benefit our understanding of how life on earth evolved.
“We think there’s a lot more organic preservation in certain settings than people have actually realised,” he says.
“It’s nice to have been the first to turn these things up, but I think the real excitement will come when other people build up enough data to get a better picture.”