Psittacosaurus Used Camouflage, New findings

3D Camouflage in an Ornithischian Dinosaur

Countershading was one of the first proposed mechanisms of camouflage . A dark dorsum and light ventrum counteract the gradient created by illumination from above, obliterating cues to 3D shape . Because the optimal countershading varies strongly with light environment , pigmentation patterns give clues to an animal’s habitat. Indeed, comparative evidence from ungulates shows that interspecific variation in countershading matches predictions: in open habitats, where direct overhead sunshine dominates, a sharp dark-light color transition high up the body is evident; in closed habitats (e.g., under forest canopy), diffuse illumination dominates and a smoother dorsoventral gradation is found. We can apply this approach to extinct animals in which the preservation of fossil melanin allows reconstruction of coloration . Here we present a study of an exceptionally well-preserved specimen of Psittacosaurus sp. from the Chinese Jehol biota . This Psittacosaurus was countershaded with a light underbelly and tail, whereas the chest was more pigmented. Other patterns resemble disruptive camouflage, whereas the chin and jugal bosses on the face appear dark. We projected the color patterns onto an anatomically accurate life-size model in order to assess their function experimentally. The patterns are compared to the predicted optimal countershading from the measured radiance patterns generated on an identical uniform gray model in direct versus diffuse illumination. These studies suggest that Psittacosaurus sp. inhabited a closed habitat such as a forest with a relatively dense canopy.

• •Preserved pigments in the dinosaur Psittacosaurus suggest countershading camouflage
• •We predicted the optimal countershading camouflage for different light environments
• •The dinosaur’s patterns would have been cryptic in a forest, but not open, habitat
• •We can also infer that dinosaur predators used shape-from-shading cues to detect prey

 Model of Psittacosaurus sp. based on skin and pigmentation patterns (specimen from the Senckenberg Museum, Germany). Image credit: Jakob Vinther et al.


Close examination of melanosomes preserved in the specimen of Psittacosaurus preserved with integument indicated that the animal was countershaded, likely due to preferring a habitat in dense forests with little light, much like many modern species of forest-dwelling deer and antelope; stripes and spots on the limbs may represent disruptive coloration. The specimen also had dense clusters of pigment on its shoulders, face (possibly for display), and cloaca (which may have had an antimicrobial function), as well as large patagia on its hind legs that connected to the base of the tail. Its large eyes indicate that it also likely had good vision, which would have been useful in finding food or avoiding predators. The authors were unable to determine which species of Jehol Formation Psittacosaurus the specimen belonged to due to the way the skull is preserved, but ruled out P. mongoliensis, based on hip features.

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* Jakob Vinther et al. 2016. 3D Camouflage in an Ornithischian Dinosaur. Current Biology 26: 1-7; doi: 10.1016/j.cub.2016.06.065