A New Look for Sinosauropteryx

Last week, a [paper] came out discussing the color patterns on the theropod dinosaur Sinosauropteryx. This dinosaur was a small-bodied meat eating dinosaur from the Cretaceous (133-120 million years ago) of China.

Figure 1 from the paper showing one of the specimens of Sinosauropteryx.

The authors took photos of 2 specimens of Sinosauropteryx under special lighting conditions. This helped them see the feathers that surround the skeletons. Feathers that had color in them are preserved more easily than feathers without color. So looking at the fossils helps us understand how colors were distributed on the animal. Artists then made reconstructions to show how the colors appeared on the dinosaur. They found that Sinosauropteryx had a striped tail, a bandit mask around its eyes, and a brown back with a white belly.

Figure 2A from the paper showing the color reconstruction on Sinosauropteryx.

The authors also wanted to test what the colors could tell us about what kind of habitat Sinosauropteryx lived in. Animals that live in open habitats (like deserts or grasslands) usually have darker colors on their back and lighter colors on their bellies. This helps break up their body shape so that predators have a harder time seeing them. Animals that live in closed habitats (like forests) usually are darker everywhere and have fewer areas with lighter colors. Think of the color differences between an antelope that lives in the grasslands, and an okapi that lives in the rainforest.

An antelope on the left showing coloration for open habitats. An okapi on the right showing coloration for closed habitats. Okapi from here.

To do this, the authors 3D printed models of the dinosaur and photographed it twice: once when it was fully sunny and once when it was completely cloudy. The full sun imitates the open habitat and the cloudy day imitates the closed habitat. They found that the shadows cast on the model on the sunny day match the color distribution found on the fossils. This means that Sinosauropteryx lived in open habitats.

Figure 2B from the paper showing how the open habitat where Sinosauropteryx lived and its coloration.

It probably used its bandit mask to reduce the sunlight entering its eyes. The striped tail, dark color on its back and light color on its belly helped camouflage it in open habitats, making it harder for predators to see it, and making it harder for prey to see it coming. This study shows us how new techniques can help us answer questions about how dinosaurs lived.

A New Look for Psittacosaurus

At the end of September (2016), a new [look] was identified for a dinosaur named Psittacosaurus. Psittacosaurus is an early member of the horned dinosaurs that lived in China in the Early Cretaceous (around 133 to 124 million years ago).

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A black and white image of Psittacosaurio. Made by V. Nikolov.

This specimen was found in the Jehol Formation of China, is relatively complete, and preserves the cells that produce scale color (called chromatophores). The specimen has been in a museum display for many years and was recently re-examined by the authors of this paper. The authors wanted to know if the coloration of the specimen could tell us about the environment in which it lived.

How is that possible? Well, many animals today use distinctive color patterns, or coloration, to camouflage themselves or to identify each other in their environments. Animals in open environments, like the plains of Africa, have sharp transitions between their dark and light colors. Animals in closed environments, like in the rainforest, have more of an even coloration, with colors that change more gradually. These differences help animals stay camouflaged and hide the outline of their bodies against the environment. Additional features like stripes help to confuse predators as well.

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A Thompson’s gazelle showing coloration for an open environment.

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An Okapi showing coloration for a closed environment.

To answer their question, the authors created a life size model of the animal using the most up-to-date calculations on their muscles, organs, and volume. They put the model outside on a sunny day and on a cloudy day, in a field and in the woods and took photos of it under each condition. They used the shadows that the sun cast on the model to predict where the scale color patterns would be for an open and closed environment.

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Figure 4 from the article showing the model they made and the photos they took. Closed environment in A-C. Open environment in D-F. The colors they found correspond to a closed environment.

Then they examined the chromatophores in the fossil and mapped the color pattern onto a computer model of Psittacosaurus. The authors found that the coloration on the fossil matches what they would expect from an animal living in a closed environment, like a forest! A dark face could have helped with keeping the sun out of their eyes, balancing body temperature, or signaling to other Psittacosaurus.

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Figure 3 from the paper showing the new look for Psittacosaurus.

Fossil plants from the Jehol Formation confirm that the area was heavily forested in the Early Cretaceous. So the evidence all fits together! Psittacosaurus lived in the forest of China during the Early Cretaceous and its coloration helped it stay camouflaged from predators.