National Geographic should have a 3-D animation up soon
The pursuit of accurate dinosaur colours just turned into a race, and a heated one at that. Just last week, I wrote about a group of scientists who claimed to have accurately identified the colours of some feathered dinosaurs by microscopically analysing three fossils. According to that study, Sinosauropteryx had a tail covered in ginger stripes. Now, another group have revealed the palette of an entire dinosaur, Anchiornis. This tiny predator had a dark grey body and the limbs bore long, white feathers tipped with black spangles. Its head was mostly grey with reddish-orange and black specks, and an extravagant reddish-orange crown.
Both reconstructions are based on microscopic structures called melanosomes. They’re partly responsible for the brilliant colours of modern bird feathers, they’re packed with pigments, and they happen to fossilise well. There are two major types. Spherical ‘phaemelanosomes’ contain a reddish-brown or yellow pigment while the rod-like ‘eumelanosomes’ have black-grey tints.
The technique of inferring colours from fossil melanosomes was pioneered by Jakob Vinther at Yale University. He used it to show that a Cretaceous bird feather probably had black and white stripes and, later, that another fossil feather had an iridescent starling-like sheen. But these were analyses of single papers and even last week’s paper coloured Sinosauropteryx by looking at just one part of a single individual.
Vinther isn’t impressed with his rivals. “They are in the Stone Age when it comes to understanding melanosome fossilization and interpretation of original colors,” he says. To him, it’s simply not enough predict colours based on the presence of one type of melanosome. Even the hues of single feathers can depend on a mix of the two melanosome types with different concentrations of pigments. So you need to know the distribution of melanosomes across an animal and even then, you still need to work out how that translates to different colours.
And that’s exactly what he’s done. When I spoke to Vinther last week, he said, “We are still far from putting colours on dinosaurs [but] the future is promising. Eventually we will have dinosaurs in technicolour. We are working seriously on that currently.” He wasn’t kidding!
He had been working on a new specimen of Anchiornis with the catchy name of BMNHC PH828. The tail is missing but the rest of the skeleton is beautifully preserved, including the skull and both sets of limbs with their elegant plumes. Rather than looking at individual body parts, Vinther took 29 samples from the specimen, representing every type of feather types across different body parts. In each one, he thoroughly analysed the size, shape, density and distribution of melanosomes.
To interpret this goldmine of data, he worked with his colleague Matt Shawkey to catalogue the melanosomes from a wide variety of living birds, from ravens to finches to mallards. This modern data set was a cross between a paint catalogue and a Rosetta stone. It told Vinther how different combinations of melanosomes led to different colours and allowed him to correctly paint his Anchiornis.
What happens when you find a feathered dinosaur that really isn’t meant to have feathers? That’s the question set by a spectacular new fossil that adds a confusing dimension to the origin of feathers.
The concept of dinosaurs with feathers is no longer surprising. Birds certainly have them and they are now considered to be living dinosaurs. The infamous Velociraptor and its relatives were covered in plumes, which ranged from the simple quills of Sinosauropteryx to the flight-capable plumes on Microraptor‘s four wings. We know about these prehistoric feathers through the beautiful fossil impressions they have left behind, but a new set of impressions may be the most impressive yet.
They were discovered by Chinese scientists led by Xiao-Ting Zheng, who named their new discovery Tianyulong confuciusi, after the museum that Zheng works in and the famous Chinese philosopher. Its small, agile body, about the size of a cat, was covered in long, hollow filaments that closely resemble the primitive “proto-feathers” (or colloquially, “dinofuzz”) of other dinosaurs. What makes Tianyulong unique is that it is a very distant relative of all these other feathered species.
So far, all feathered dinosaurs are theropods, a group of two-legged and (mostly) carnivorous animals that included Tyrannosaurus and Velociraptor, and indeed, modern birds. The theropods belong one of the two major groups of dinosaurs, the Saurischia. Tianyulong, however, is a clear member of the other dinosaur lineage, the Ornithischia, which include the various armoured, horned, spiked and duck-billed species. This is the first time that anyone has discovered an ornithischian with feather-like structures all over its body.
More specifically, Tianyulong is a heterodontosaur, a group of small plant-eaters that are the most primitive of the ornithischians. Its position in the dinosaur family tree raises big questions about the origins of feathers. If its filaments are related to the proto-feathers of the theropods (which is possible but not certain), they either evolved independently or were derived from filaments that covered the very earliest of dinosaurs.
Beipaiosaurus was among the strangest of dinosaurs. It looked like a fusion of body parts taken from several other species and united in the unlikeliest of proportions. It had a stocky body, long arms adorned with massive claws, a long neck topped by an incongruously small head, and a beaked mouth. Bizarre as this cocktail of features is, it’s the animal skin that has currently warrants attention.
Fossils of Beipaiosaurus include impressions of its skin and these clearly show long, broad filaments clumped around its head, neck, rump and tail. They are feathers, but most unusual ones. Traces of feathers have been found on other dinosaurs (including the infamous Velociraptor) and they come in a variety of shapes and forms. But all are composite structures consisting of several slender filaments that either sprout from a single base or branch off a central stem.
Beipaiosaurus was also covered in some of these complex feathers, but it had other plumes that were far simpler. Each of these was a single, unbranched, hollow filament – exactly the sort of structure that palaeontologists had predicted as the first step in the evolution of feathers.
Until now, their existence was merely hypothetical – this is the first time that any have actually been found in a fossil. Other, more advanced stages in feather evolution have been described, so Beipaiosaurus provides the final piece in a series of structures that takes us from simple filaments to the more advanced feathers of other dinosaurs to the complex quills that keep modern birds aloft.