September 22, 2016:

by Elsa Panciroli

Forty researchers elbow their way to the front of the room. They whip out their cameras and mobile phones like palaeontological-paparazzi, and start snapping. Others hang back, hands on chins, to take in the animal standing on the table-top from different angles. They dispense approving nods, and converge to discuss their conclusions in hushed tones.

It’s not like anything seen alive on Earth today: it’s the size of large turkey, but with a face like a Jim Henson puppet. The head is a shoe-box with eyes, the Frankensteinian flatness on top accentuated by horns sticking out horizontally from each cheek. A parrot-like beak juts out at the front. One researcher reaches out and dares to touch the broom-like bristles that erupt from its tail. Another leans over and studiously peers up at the animal’s bottom.

This was the scene at the unveiling of paleoartist Bob Nicholls’ new reconstruction of Psittacosaurus. Hailed as the most accurate dinosaur reconstruction ever, it is based on studies of a spectacular fossil from China, carried out by a team led by Dr Jakob Vinther of the UK’s University of Bristol.

The Psittacosaurus specimen Vinther’s team studied is held at the Senkenberg Museum in Frankfurt. It is a complete skeleton from one of the world’s best preserved fossil deposits in China. Named the Jehol Biota, these deposits are a Lagerstätte, from the German for storage place: they are literally a rocky safehouse for the world’s most well-preserved fossils. There are a handful of Lagerstätte around the world, famed for yielding remains that retain their fossilised soft tissues, feathers, fur, skin and stomach contents. The Senckenburg Psittacosaurus is an exceptional example, even having its cloaca preserved – the multi-purpose opening for excretion, reproduction and urination.

While the exquisite patterns preserved in this specimen have been recognised before, Vinther’s team is the first to approach it quantitatively. To get a clear picture of the pigments in the dinosaurs’ skin, Vinther’s team fired a laser at the specimen – think less death-ray and more glow-stick – to highlight fluorescent materials (calcium phosphate) remaining preserved from the animal’s scales. Under an electron microscope, they confirmed the presence of melanosomes: the structures that store pigments in cells and tissues. From there it was a case of photographing the whole fossil and mapping the pigment patterns from the squished Cretaceous dinosaur on to a three-dimensional model. This is where paleoartist Robert Nicholls came in.

Based in Bristol, Nicholls is well known for his vivid paleontological artwork. He has worked with the BBC, National Geographic, various authors, and museums to breathe life into prehistory. His sketchbooks reveal a dark sense of humour, from sauropod necks acting as lightning rods, to dinosaurs suffering from dysentery.

“Some of my earliest memories are of drawing dinosaurs as a child, and that passion for illustrating extinct animals and environments has never left me,” he tells me enthusiastically. “Jakob called me one morning in 2014 and asked if I was interested in reconstructing a fossil dinosaur with accurate colour patterns. I said, yes!”

I asked Nicholls what makes this Psittacosaurus so special? “The most surprising features include an unusually large and wide head, highly pigmented clusters of scales on the shoulders, robust limbs, patagiums (skin flaps) behind the hind limbs, and a highly pigmented cloaca.” These features make him confident this is the most accurate reconstruction ever produced: “When the anatomy surprises me – it confirms that I’ve followed the fossil evidence rather than any preconceived ideas of my own.”

Recent palaeontological re-examinations of the Psittacosaurus are more than skin deep. The dinosaur takes its name from the Psittacines, the parrots, because of its superficially parrot-like beak and skull. This is a vivid simile, but it has led some palaeontologists (and palaeoartists) down an unhelpfully literal path. In 2010 the renowned palaeontologist Paul Sereno argued that “parrot-like” was more than just phraseology: he suggested psittacosaurs even had the same musculature as their modern bird analogues. This was controversial because parrots have evolved unique muscles not seen in other birds, or reptiles. Could such unusual muscles have appeared in this single group of dinosaurs?

So, despite the name, Psittacosaurus was not the dazzling parrot of the Mesozoic. Indeed, Vinther’s team reveals it was a creature more likely to stick to the shade.

Usually when reconstructing an animal, paleoartists research the creature’s anatomy, then the habitat it lived in, and use modern analogues to imagine likely colouration that matches the extinct animal’s lifestyle. Vinther’s study turns this process on its head: if you know the animal’s skin patterns in great detail, what does this tell you about how it lived?

“Colouration”, says Vinther, “tells us something about the dynamics between predators and their prey, among others. It is an important defence strategy in modern animals.”

To examine countershading in their Psittacosaurus, Nicholls created a second, plain grey model without pattern. This “blank” was placed outside, first in overhead strong sunlight, then in diffuse light, and photographed to examine how light and shadow fell on the body.

The images of the “blank” model in diffuse light matched perfectly with the skin pigments revealed in the Senckenberg fossil. The countershading told Vinther’s team that Psittacosaurus lived in a closed light environment, such as under a forest canopy.

“We had only looked at feathered dinosaurs and ones that are close to birds and lived in trees, which is a very different mode of life than this ground dwelling dinosaur,” explains Vinther. “This little guy was clearly exhibiting camouflage on most of its body – except for the strong pigmentation in the face, which might actually be for show rather than concealment.”

This is the first unequivocal evidence of countershading in a terrestrial fossil. It heralds a fresh perspective on extinct animals, one that sees these creatures not as hulking monuments standing alone in a landscape, but living beings adapting to their environment and surviving predation. Meanwhile, more sophisticated reconstruction of soft tissues provides further insights into feeding strategies, and dispels myths and misunderstandings over dinosaur anatomy and capability.

Now we can tap into how extinct animals influenced each other and how that is reflected in their colouration
Jakob Vinther

This Psittacosaurus also highlights how important research is for creating accurate paleoart. “The days when a paleoartist could simply fabricate any colour pattern they wanted for a dinosaur are gone,” Nicholls points out. “We have evidence of colour patterns in an increasing number of species, and where we don’t there are a great number of trends in nature that need to be considered, not to mention the variety of ways animals create colour.”

So what comes next, I ask Vinther? “I am personally looking at mammals from Messel for these reasons. We have lots primitive forms there - what will their colour pattern tell us about their environment and their interactions?”

I for one, can’t wait to find out.

References

Taylor, A, Lautenschlager, S, Zhao, Q, Rayfield, E 2016 Biomechanical evaluation of different musculoskeletal arrangements in Psittacosaurus and implications for cranial function. The Anatomical Record

Vinther, J, Nicholls, R, Lautenschlager, S, Pittman, M, Kaye, TG, Rayfield, E, Mayr, G and Cuthill, I C 2016 3D Camouflage in an Ornithischian Dinosaur. Current Biology, 26, 1-7.

Vinther, J 2015 Fossil melanosomes or bacteria? A wealth of findings favours melanosomes. BioEssays.