78 Australian Geographicthe pigments wrapped up inside them, and also through their
stacking and organisation, which interferes with and manipulates
the light that hits them.
Sinosauropteryx was just the start, and now a series of compel-
ling papers has detailed the colours of Archaeopteryx, Anchiornis
and Microraptor. National Geographic described Anchiornis as hav-
ing “looked something like a woodpecker the size of a chicken,
with black-and-white spangled wings and a rusty red crown”.
The team behind that discovery, including Yale University
feather expert Professor Richard Prum, analysed the colour on
29 diff erent regions of the animal’s body, giving them a largely
complete picture of the overall plumage pattern. Archaeopteryx
would have been black, while a 2012 study of 130-million-year-old
Microraptor revealed it would likely have had dark blue to black
plumage with white dappling and an iridescent sheen – perhaps
similar to a magpie or raven.
“Modern birds use their feathers for many diff erent things,
ranging from fl ight to thermoregulation to mate-attracting
displays,” Richard’s co-author, Dr Matt Shawkey, from the
University of Akron in Ohio, told reporters. “Iridescence is
widespread in modern birds and is frequently used in displays.
Our evidence that Microraptor was largely iridescent thus suggests
that feathers were important for display even relatively early in
their evolution.”A
USTRALIA’S FAIRY WRENS are delightful little songbirds,
some of which have brilliant blue and iridescent plumage.
Recent studies have also shown that male fairy wrens of
some species have patches of feathers that refl ect ultraviolet (UV)
light. This is invisible to us, but appears as another layer of colour
to female wrens. Although humans have three types of colour-
detecting rod cells in their eyes – red, blue and green – birds
have a fourth, which detects UV light. This means they see the
world in a much more complex palette of colours than we do.
It illustrates just how important colour is to these animals, and
that the ability to see a wide range of bright colours may have
been spurred on by colourful plumage that evolved for display
purposes in their dinosaur ancestors.
It would be no surprise to fi nd that dinosaurs were as varied
and colourful as birds, given they most likely shared the full
colour vision of birds. Although some mammals are colourful,
most tend to be fairly drab, in greys and browns and shades of
black and white. This is because, aside from a handful of species
(including chimps, orangutans, baboons and humans), they don’t
see in colour, instead visualising the world in black and white.
Mammals also have more of a need to be camoufl aged than
birds, because they often live on the ground and fi nd it morediffi cult to fl ee from predators. “Birds are brilliantly coloured
because they do see in colour, and it’s likely that, because birds
are a kind of dinosaur, the extinct dinosaurs also saw in bright,
vivid colour,” says Dr Mark Norell at the American Museum
of Natural History in New York City.
These colours might have helped them recognise other mem-
bers of their own species, camoufl aged them, or been used for
defence to dissuade other animals from attacking them (in the
same way that some poisonous frogs are thought to use bright
colours as a signal that says, “Don’t eat me, I’ll make you sick”).
Of course, in living birds, some of the most brightly coloured
are the males of those species that use colour to woo and court
females, such as peacocks and birds of paradise.
In dinosaurs there evolved a great array of ornamentation- including crests, frills, horns and spikes – to attract mates,
warn off rivals and otherwise communicate. This surely means
they used feathers for the same purpose, just as many brightly
coloured birds do today. “Once dinosaurs had acquired feathers
for insulation, what could be more natural than to adapt them
into display structures?” asks Professor Phil Currie, a palae-
ontologist at the University of Alberta in Canada. “They are
lightweight, strong, colourful, and can be shed and replaced.”
Could it even be that the success, diversity and longevity
of the dinosaur family is attributable to the bright colours the
evolution of feathers aff orded them?
In combination, the variations in colour and structure can
be a powerful tool for creating the diff erences among isolated
populations that allow new species to form. The formation of
new species is dependent on there being some sort of barrier
to individuals of diff erent populations mating. Feathers are a
“perfect structure to provide such a platform”, says Professor
Xing Xu at the Institute of Vertebrate Paleontology and Paleo-
anthropology in Beijing, China.
Although at this stage he says it’s just a crazy idea, he believes
there may even be a way to test the link between feathers and
evolutionary success in a group of animals. The fi rst step is
to confi rm whether the diff erent kinds of feather-, quill- and
fl uff -like structures seen in fossils of pterosaurs and dinosaurs
(such as Sinosauropteryx, Caudipteryx, Beipiaosaurus, Tianyulong and
Psittacosaurus) all share a single evolutionary root, or if they
evolved in separate instances. The next step would be to try
to reconstruct feather colours and then compare the diversity
of brightly coloured groups of dinosaurs and birds with that of
groups without such a range of brightly coloured feathers.
Only more research will tell, but colourful feathers may have
played a more important role in the evolution and diversifi cation
of birds and dinosaurs than anyone could have predicted. AG
Dinosaurs evolved a great
array of ornamentation:
crests, frills, horns and spikes.
JOHN PICKRELL is the editor of
AUSTRALIAN GEOGRAPHIC and a dinosaur
enthusiast. This is an edited extract from his
book Flying Dinosaurs: How fearsome reptiles
became birds (NewSouth, 2014, $29.95).
Learn more about the book and feathered
dinosaurs at: http://www.fl yingdinosaurs.net IVPP / UNIVERSITY OF TEXAS / UNIVERSITY OF BRISTOLag0914_JohnsdinosP78 - 73 2014-08-11T16:16:25+10:00