Science Interviews

Interview

Sun, 13th Feb 2011

Planet Earth Online - Dinosaurs Show their True Colours

Professor Mike Benton, University of Bristol

Listen Now    Download as mp3 from the show What Makes Mucus Green?

Diana -   Now heres a question...  What colour are dinosaurs?  Its an issue that puzzled palaeontologists since fossils of the creatures were first discovered.  But now, thanks to modern science, dinosaurs are beginning to show their true colours.

Professor of palaeontology at the University of Bristol, Mike Benton showed Planet Earth podcast presenter Richard Hollingham a fossil of a 12-million-year-old bird.

Mike -   So we have some specimens here...

Richard -   So were opening a locked cabinet, pulling out a drawer here.

Mike -   So this is an astonishing little specimen....

Digital illustration of the coelurosaurian dinosaur ''Sinosauropteryx prima'', based on the holotype specimen.Richard -   The sample fits in about the palm of your hand.

Mike -   Yes, the palm of my hand, and this is a complete little bird.  You can see that the bones are a kind of cream colour and almost chalky in appearance.  These are the wing bones here, here's the back bone and the ribs there.  I think heres the head, kind of bent back, almost over the top of the thing.  And around it is a halo of fluffy, bluey grey material which are traces of the feathers, and you can see at the edges they become wispy.  And so, we were then focusing on this dark gray material which is obviously remnants of soft tissue.

Richard -   It is coloured.  There are different shades of brown and gray.  Can you say that they were the colours of the feather then?

Mike -   No.  I think that's been the question so far.  There are many fossil birds and there are many fossil dinosaurs with rather obvious feathers around the edge and nobody can deny that they're feathers because in many cases, they have the detail of a wing feather with a quill up the middle and the branching barbs at the side.  Others like these ones here are the sort of wispy down feathers, as we would call them, that cover the whole body area in the base of the wings and they're there mainly for insulation.  But as you look at them, the differences in tone, the different shades of gray, you would be foolish to try and interpret those as original colour.

Richard -   So, you got some of the samples that you put under the electron microscope.  We can hear this electron microscope buzzing away behind us.  If we look at the screen here, you've got one of the images when you're zooming in to the micron level here...

Mike -   Yes, so this scale is 2 microns.

Richard -   Its almost like a series of little rugby balls all jammed together.

Mike -   Yes, they're sort of arranged higgledy piggledy, you can't see particular rows.  These little structures, judging by their shape and size, were pretty certain that these are what are called melanosomes.  Melanosomes in feathers of modern birds are introduced at the very early embryonic stage of the feather as it sprouts from the skin and they come from the skin itself.  So melanin is a well-known chemical that occurs throughout almost all organisms.  Mostly, it gives a black colour and in the case of birds, it is produced within the skin and then it is packaged in a particular way before it goes into the feather because the keratin that makes the feather is rather like a plastic or its quite a hard solid material.  And in order to get the chemical in, it has to be packaged into these organelles.

Richard -   So, a particular shape gives you a particular colour.  Is that what you're looking for?

Sinosauropteryx type specimen with filament impressions, Inner Mongolia MuseumMike -   This is what were looking for and this is a remarkable fact that are across all modern birds and across indeed all modern mammals there are two main kinds of melanosomes.  There are numerous others in between, but the two main end members are a sausage-shaped melanosome, that's about 1 micron in length, and at the other end, there's a spherical melanosome that's about half a micron across, or just slightly less.  These two end members always correspond to black and ginger.  So the long sausage-shaped one is black to dark brown and is called a umelanosome and the spherical one at the other end is a ginger colour, always in mammals and birds and the rest and its called a phaeomelanosome.

Richard -   So lets zoom back out from these samples you've got at micron level under the electron microscope to this dinosaur bird.  What does it look like?

Mike -   We looked at a number of different dinosaur specimens from China, but the one we were particularly keen to study in detail is called Sinosauropteryx, and it was a small turkey-sized animal with a long thin tail.  But the reason we chose it was because it has the most primitive feather-like structures and we thought if we can not only determine the colour, but also determine whether these are feathers or not then were doing something important in terms of the evolution of the group.  So we had two things to do and we looked at some of the dark coloured ones and found that they were full of phaeomelanosomes, the ginger giving melanosomes.  So we believe that shows two things:  first of all, that these simple bristle-like filaments actually are some kind of a feather and that's important, and secondly, they have to be ginger.  So we can reconstruct this dinosaur at least with a ginger in white-striped tail, like a barb or spoke.

Chris -   Dianasaur or dinosaur?

Diana -   Ginger power!  Yes!  Revealing the coloration of dinosaurs, millions of years after they died.  That was Mike Benton from the University of Bristol and he was talking to Planet Earth podcast presenter, Richard Hollingham

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