Pigment in Scaly Dinosaurs

[DinoLord]

It's frequently said that when illustrating dinosaurs, the colors used are pretty much always up to one's imagination (within reason of course). However, I've been wondering lately as to the sorts of limitations scaly dinosaurs (like sauropods) had when it came to color palette. Does anyone here happen to know about the origins of different colors in scales, and if any particular colors can be ruled out as unlikely to have occurred (for example there are not many purple animals around today)?

[tyrantqueen]

There are some very colourful lizards:



Some people say that you would not see bright colours on a sauropod because it would need to be camouflaged. The counterpoint to that argument is that they were such a large size anyway, so camouflage would have been moot. Personally, I like my dinosaurs colourful.

[fabricious]

I like a good mix of both, sine every big group of animals has those relying on camouflage, those displaying bright colors and those who don't need to do either of them and are just dull colored.
For a colorful depiction of scaly dinosaurs I would mainly rely on extant reptiles and the color palette we have there, for feathered ones I'd look at birds, naturally.

[DinoLord]

Good point on the lizards (though the really colorful ones seem to be either herbivorous, omnivorous, or insectivorous). I'm mainly curious as to where different colored pigments come from (especially blue pigment), and if they would have been possible in dinosaurs of different diets.

I agree with you on the sauropod point - there really would have been no use with trying to camouflage themselves as adults. I wonder if this applied to adults of sauropod-hunting theropods as well...

[stoneage]

The largest animals today are not brightly colored.  Whales, Elephants, Rhinos, Hippos, and scaley animals like Crocodiles and Alligators.
Today there are no birds over 350 pounds and the Ostrich isn't brightly colored.

[fabricious]

The largest animals today consist only of mammals, though, which don't show a big variety of bright colors in all kinds of sizes. Alligators and crocodiles aren't brightly colored as well and might never have been, so that is not really a good clue to follow.

[DinoLord]

Modern crocodilians are all ambush predators so it makes sense for them to have more subdued colors.

However the main point of my original post was not what color schemes are likely, but what colors are biologically possible. I know this kind of thing has been done before for the simple feathers many theropods had, but to my knowledge hasn't been discussed concerning scales.

[stoneage]

The largest animals today consist only of mammals, though, which don't show a big variety of bright colors in all kinds of sizes. Alligators and crocodiles aren't brightly colored as well and might never have been, so that is not really a good clue to follow.

But some reptiles do have bright scales, just not its larger members.  Big fish don't have bright scales either.  Birds have bright feathers but not bright scales.  Just because an animal doesn't need to be camoflaged doesn't mean it needs to be brightly colored. 

[Newt]

By phylogenetic bracketing, you would expect dinosaurs and pterosaurs to have any of the colors found in living reptiles and birds. So, the sky's the limit, really.

There are basically two ways to create color: pigments, which are colored molecules, and structural colors, which rely on the arrangement of molecules rather than their inherent color. The colors in a rainbow, for example, are structural, being based on selective reflection and interference of light from inherently colorless water droplets.

Blues, purples, and iridescent colors are typically structural, while blacks, browns, yellows, reds, oranges, silvers, and whites are typically pigment-based. Greens (in reptiles anyways, I don't know about birds) are usually a combination of blue structural color and yellow pigment. If you ever get a chance to tour a museum herp collection, note that all the animals that were green in life are pale blue in preservative- this is due to degradation of the yellow pigment, which fades soon after the animal dies.

[DinoLord]

Thanks for the reply Newt. I was wondering as to what colors were structural vs from pigment, and that really clears it up.

Good points stoneage. Though since you brought up fish, I thought of the example of the arapaima (largest freshwater fish in the world). Juveniles are dull grey while adults can get a really nice red coloration. There's also the cassowary, which has a pretty brightly colored head for a decently sized ratite. However I think you're right in that most cases large extant animals are dull.

[Newt]

Some more large, brightly colored animals:



http://newshour.s3.amazonaws.com/photos/2011/02/23/UF_Rhino_slideshow.jpg





http://ibc.lynxeds.com/files/pictures/P1120145.jpg

[tyrantqueen]

Don't forget koi carp, they can grow to quite large sizes and are colourful.

I found some others too:

[stoneage]

Although the Arapima does have some green and red I really don't see it as bright.  The Cassowary does have some bright colors as do the fish etc., but their still all under 500 pounds.  Really not comparable to a sauropod.  Why was the parrot included?

[DinoLord]

Not overly bright but the color is intense where it is.

[Gwangi]

Koi carp were created through selective breeding TQ, that's why they're colorful. It's not natural though. I still get your point though and yeah, as a major fish nerd I can think of a lot of examples of large, brightly colored or boldly marked fish.

Like the Opah or moon fish.


Red tail catfish.


I think people make the mistake of assuming since large mammals are generally bland in color (most mammals in general are) that dinosaurs were too but dinosaurs and mammals are too different to make that connection. Dinosaurs are reptiles so probably had great color vision, were mostly diurnal and relied a lot on display...like modern reptiles and birds. Mammals generally have poor color vision (aside from primates which need it to identify fruit and whatnot) and are nocturnal or crepuscular.

Unfortunately we just don't have a lot of large reptiles or birds alive today. The sample size is too small to really say "large=dull colors and markings". Examples like the cassowary, ground hornbill, oscillated turkey, peafowl, pheasants or macaws prove large birds can be colorful but they really don't come close to the size dinosaurs attained.

BTW, have you guys seen the oscillated turkey? Beautiful! I say with dinosaurs, given their relationship to reptiles and birds, anything goes.


EDIT: Some birds do have bright scales.

[DinoLord]

Thanks for the bird pics Gwangi. The oscillated turkey is one beautiful animal. I guess dinosaurs could have had bright blue scales...

Also good point on the sample size of large reptiles and birds and on color vision. Perhaps with larger sauropods sexual selection would have led adults to develop (potentially vividly colored) mating displays?

[Gwangi]

Thanks for the bird pics Gwangi. The oscillated turkey is one beautiful animal. I guess dinosaurs could have had bright blue scales...

Also good point on the sample size of large reptiles and birds and on color vision. Perhaps with larger sauropods sexual selection would have led adults to develop (potentially vividly colored) mating displays?

I don't think sauropods could have benefited from camouflage and they weren't mammals so there is no reason to think they shared mammalian color trends. They very well could have been colorful.

Like Newt said, phylogenetic bracketing allows dinosaurs to have had bright colors. They were reptiles after all and all the groups of reptiles have examples of brightly colored species. Again, ambush predators like large snakes and crocodiles need camouflage. I don't think it is their size so much as their way of life that prevents them from being overly colorful. Still, many had bold patterns and markings. I don't know what theropods would have been ambush hunters but they would actually have a good reason for dull coloration. Though as tigers show us, bold patterns and colors can act as camouflage too.

So even if some dinosaurs lacked bright colors, there is no reason to say they couldn't have looked like this...



If their lifestyle necessitated it.

[Newt]

A colorful (for a mammal) predator:



Mammals are not only limited by vision; they have lost many of the ancestral tetrapod pigment systems. The great majority of mammalian colors are produced with melanins alone, or else structurally (the blue of some primates' faces is produced by a particular arrangement of collagen fibers).

[amargasaurus cazaui]

I noticed the topic here Dinolord and wondered if you had examined the paper I recently offered based on a psittacosaurus specimen with preserved actual scales demonstrating both shape and colors.

[DinoLord]

I had not thought of that paper when thinking of this topic; will have to take a look when I have enough time to sit down and properly read through a paper. Thanks for the tip.