This month Fiann M. Smithwick and colleagues from University of Bristol describe the coloring of a small theropod that lived in the Early Cretaceous . 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.
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!”
- Paul Rincon, Dinosaur sported ‘bandit mask, in BBC News – Science & Environment 2017. http://www.bbc.com/news/science-environment-41763478
- 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:
Dinosaur bandit mask