Tag Archives: Jakob Vinther

Dinosaur Face Coloring and Camouflage

In recent years, we have learned tons of things about Dinosaurs, including stuff that used to be thought beyond discovery, such as their color schemes.

We now have evidence about the camouflage schemes of dinosaurs, which are similar to contemporary animals. (Earlier posts here, here, here, here)

This month Fiann M. Smithwick
 and colleagues from University of Bristol describe the coloring of a small theropod that lived in the Early Cretaceous [2]. The work is based on three well preserved specimens from the prolific beds of Liaoning, China. These fossils have fairly complete skeletons, and trances of melanin that indicate the skin coloring. These little guys were about the size of a kitten, except for their half-meter long tail.

The new study found evidence that the tail was ringed, the body dark on top with light belly (countershatding) and the head had a “mask” that surrounded the eye.

Sinosauropteryx probably lived in open environments, under constant threat of predation Artwork Robert Nicholls:

All of these features are known form contemporary species (the BBC notes that this bandit mask is known in man contemporary species, including raccoons, badgers, and nuthatches, among others.) What evolutionary advantage may be incurred by a striped tail or bandit mask is not known.

To investigate the purported camouflage effects countershading coloration, the researchers conducted an interesting computer graphics aided study.

The idea is that “the pattern of pigmentation from the dorsal to ventral body regions should match the illumination gradient created by the lighting environment in which it lives”. The countershading serves to “self-shadow”, and reduce the visual cues that outline the animal’s body—ideally, making it less noticeable to any passing T. rex or its own small tasty lunch.

Specifically, out in a clearly lighted area, the shadows are sharp and high up on the body. In diffuse light of a forest, the shadows are softer. Thus, “Paleocolor can help predict paleohabitat.”

Using Blender, they created 3D computer models of the torso, which were 3D printed. The models could be photographed in different lighting conditions, to show how the shadows fall.

The research showed that in strong overhead light, the shadow transition falls in the area of the imputed countershading. This suggests that the animal was adapted to live in an open, well sunlit environment.

As a computer scientist, I noticed that the researchers didn’t trust the lighting algorithms of Blender for this exercise. I suspect they would have worked well. But, I grant you that this would have introduced complicated logical dependencies on the shading algorithms and software implementation.

The conclusion is that this small animal lived in open areas, where there was little cover to hide. They comment that one of the specimens had recently eaten a lizard at the time of its death, and that lizard resembles species that live in the open.

Paleocolor can help predict paleohabitat.”

This is a pretty cool study, demonstrating that color schemes may add to understanding of ancient species and ecologies.

The study shows that even without much direct data about the habitat,

reconstructing the color of extinct animals can inform on their ecologies beyond what may be obvious from skeletal remains alone.” (p.1)

It is also interesting that this and other studies of paleocolor adds to the evidence of similar adaptations among contemporary and ancient species. This can only improve understanding of the contingencies of evolution and adaptive advantages.

Oh, and also, “Yay for computer graphics and simulations!”


  1. Paul Rincon, Dinosaur sported ‘bandit mask, in BBC News – Science & Environment 2017. http://www.bbc.com/news/science-environment-41763478
  2. Fiann M. Smithwick, Robert Nicholls, Innes C. Cuthill, and Jakob Vinther, Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota. Current Biology, https://www.sciencedirect.com/science/article/pii/S0960982217311971

 

PS.  Several Ideas for Great Band Names:

Countershading
Banded tail
Dinosaur bandit mask
Paleocoloration

 

Dinosaur Camouflage: Hiding From Hunters

Regular readers know that I love dinosaurs.

T. rex. Avian and bird-like dinos.   Stegosaurs. Triceratops. So cool!

And how about ankylosaurs, the wild family of armored dinosaurs.

This month Caleb Brown and colleagues report on an astonishingly well-preserved fossil of an ankylosaur discovered in Alberta [1]. The specimen was tagged Borealopelta markmitchelli, and lived about 110 million years ago.

The animal was about the size of a rhinoceros or moose. It’s back and neck are covered with hard, spiky armor, so characteristic of ankylosaurs.

The biggest news, though, is that the scales are so well-preserved that it is possible to discern the pigments that indicate the skin color. These observations indicate that the Borealopelta had a camouflage scheme similar to deer and other heavily hunted species. The color scheme appears to be a darker brown on top, with light underbelly.

Royal Tyrrell Museum of Palaeontology, Drumheller, Image caption An illustration of the 110-million-year-old Borealopelta markmitchelli

 

The researchers indicate that the color scheme is an important indication that these animals were under significant pressure from predators. The “armor” of anlyosaurs has long been assumed to be defensive, though no direct evidence of predation is available. The new evidence of coloration suggests that this was indeed the case.

Preserved evidence of countershading suggests that the preda- tion pressure on Borealopelta, even at large adult size, was strong enough to select for camouflage from visual predator.” ([1], p. 6)

The paper points out that in living species, larger animals do not show countershading, nor to smaller animals with defensive equipment. The Borealopelta is large, yet still has both armor and camouflage. The researchers conclude that this means only one thing: they were prey for large, powerful, and visual hunters. The obvious candidates are theropods. What else could bring down such a large, heavily armored beast?

Finding a large, heavily armored herbivorous dinosaur is the most concrete evidence, therefore, for intense predation on very large prey in the Mesozoic.” ([1], Supplemental Discussion)

Neat!


  1. Caleb M. Brown, Donald M. Henderson, Jakob Vinther, Ian Fletcher, Ainara Sistiaga, Jorsua Herrera, and Roger E. Summons, An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics. Current Biology, http://dx.doi.org/10.1016/j.cub.2017.06.071
  2. Sarah Gabbott, Armoured tank-like dino used camouflage to hide, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-40815935

Fossil Suggests Dinosaur Camouflage Pattern

It is a great age for dinosaur studies, with more and more fossil evidence coming to light, including finds from China, South America, and other areas sparsely recorded until this century.

One of the most exciting developments has been the discovery of non-skeletal remains, which was considered unimaginable when I was a kid (i.e., when I first became interested in dinosaurs and fossils).

In recent years we have seen remarkably preserved feathers, not only proving that dinosaurs wore feathers, but giving us a detailed view of what the feathers look like. Even more, this gives an idea of the color scheme of the animal.

This month an international team led by Jakob Vinther reported a remarkably preserved Psittacosaurus with considerable amounts of skin closely associated with the skeleton. The residues contain melanin, and the distribution was used to infer the possible visible appearance of the animal. Overall, it appears to be a (not too surprising) “countershading” pattern, dark on top, and light underneath, as well as a black or dark face.

Moving rather farther from the fossil remains, they also conducted a computational study, projecting the inferred colors onto a 3D model of the reconstructed body. The resulting model was studied by applying different lighting, representing conditions in possible habitats (open desert, deep forest, etc.) They conclude that the pattern is an effective visual camouflage for a forest. The pattern might also suggest bipedal walking, though that is more speculative.

I note that Psittacosaurus has a rather mysterious bristles on the tail. These don’t resemble familiar avian species, and it is not clear what function they may have had. Dinosaurs are so weird, that’s part of what is so fun!

This is an outstanding find and it is so cool to get some real notion of what dinosaurs looked like.

It is also an interesting example of “computational” argument, sliding farther and farther from the fossil data, piling inferences upon inferences, and comparing models (theoretically based) with reconstructions from the data. The headline conclusions about color scheme and inferred habitat are based on a rather long chain of inference, as well as arguments based on computations.

I call this “computational” argument, though the computations were not fully digital as would be expected. Actually, the modelling in this case was surprisingly “analog”.  For some reason they eschewed the obvious digital modelling in favor of a much less convenient and accurate plaster model. The lighting was done in situ in a botanical garden, rather than using simulations that could explore a broad and continuous range of environments.

The final conclusions are scarcely controversial (countershading is a common adaptation, the fossil was found in a fossil forest environment). Still, I think it will be important to replicate this study, revisiting the assumptions and inferences explicit and implicit in the modelling and computer analysis. I’m not sure whether the published materials are sufficient for such a review or not.

This replicability problem is a perennial challenge for digitally enabled science of all kinds.


  1. Jakob Vinther, Robert Nicholls, Stephan Lautenschlager, Michael Pittman, Thomas G Kaye, Emily Rayfield, Gerald Mayr, and Innes C Cuthill, 3D Camouflage in an Ornithischian Dinosaur. Current Biology, http://www.sciencedirect.com/science/article/pii/S0960982216307060