Fossil Friday #8 - Sinosauropteryx

One of the most common misconceptions about dinosaurs is that there is no way of knowing what colour they were. This relates to the belief that the only evidence we have of prehistoric life is from fossilised bones. Neither of these statements is true, and one dinosaur in particular that highlights this is the rather iconic Sinosauropteryx prima.

Hailing from the Yixian formation in China, a site famous for its exceptionally preserved Early Cretaceous dinosaurs, the first specimen was discovered in 1996 by amateur palaeontologist, Li Yumin, and sold to the National Geological Museum in Beijing. When images of the specimen had reached the United States, many Palaeontologists were excited by its discovery, including Dr John Ostrom, the man who arguably started the Dinosaur Renaissance in the 1960s with the discovery of Deinonychus antirrhopus (Chen et al, 1998).

Looking at the holotype specimen, it is easy to see why this discovery caused so much excitement. Not only was Sinosauropteryx beautifully preserved with almost a complete skeleton, but it had conclusive evidence of feathers present on the specimen. This came at a time when the presence of feathers on non-avian dinosaurs was a particularly debated topic, with not much evidence to support their presence. This was the first dinosaur outside of the Avialae clade to ever be found with evidence of feathers on the animal. Since then, more evidence has been found, and it is widely accepted today that many species of Compsognathid and Maniraptoran dinosaurs had feathers, concluding that the earliest feathers first evolved in the Late Jurassic period, about 150 million years ago (Evan and Gelernte, 2018; Ji and Ji, 1996)

Holotype specimen of Sinosauropteryx prima, with feathers visible along the spine and tail

The presence of feathers, however, is perhaps the second most fascinating quality of this specimen. This is because Sinosauropteryx was also preserved with melanosome structures, which have been analysed to hypothesise the colour of the animal. It has been found that this particular specimen was reddish-brown in colour with white bands on its tail, and a light underside and face. This shows that Sinosauropteryx displayed countershading, being dark on top to be less visible to large predators that would be looking down to the ground, whilst also being less visible to small prey that would be looking upwards towards the sun-lit sky (Evan and Gelernte, 2018; Zhang et al, 2010).

Reconstruction of S. prima, demonstrating countershading.

References

Chen, P.; Dong, Z.; Zhen, S. (1998). "An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China" (PDF). Nature. 391 (8): 147–152.

Evan T. Saitta; Rebecca Gelernte; Jakob Vinther (2018). "Additional information on the primitive contour and wing feathering of paravian dinosaurs" (PDF). Palaeontology. 61 (2): 273–288.

Ji, Q.; Ji, S. (1996). "On the discovery of the earliest bird fossil in China (Sinosauropteryx gen. nov.) and the origin o. Chinese Geology. 10 (233): 30–33.

Zhang, F.; Kearns, S.L.; Orr, P.J.; Benton, M.J.; Zhou, Z.; Johnson, D.; Xu, X.; Wang, X. (2010). "Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds" (PDF). Nature. 463 (7284): 1075–1078.