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Bones and stones: vertebrate palaeontology and HK geology

with HKU palaeontologist Dr. Michael Pittman


Welcome back! In this article you will find out about some of my latest dinosaur research which extends the kind of information that we can extract from fossils. Ready to find out more about dinosaur appearance, anatomy and habitat? You can find out more about our current topic on Twitter @PalaeoPittman. Enjoy!

3D camouflage and tail bristle structure in the early Triceratops relative Psittacosaurus

Recently my collaborator Thomas G Kaye (Foundation of Scientific Advancement, USA) and I used a cutting edge laser-based imaging technique to help produce the most detailed colour reconstruction of a dinosaur ever made . The dinosaur, the 120-million-year-old early Triceratops relative Psittacosaurus, is known from hundreds of specimens ranging from hatchlings to adults, but our work focused on the specimen with the best soft tissue preservation (Fig. 1).

Fig 1: Photo of the study specimen: Psittacosaurus sp. SMF R 4970. The specimen is housed at the Senckenberg Museum of Natural History in Frankfurt, Germany. Credit: Jakob Vinther.

The new research led by Dr Jakob Vinther of the University of Bristol (UK) was published in the prestigious science journal Current Biology and reveals that Psittacosaurus had a lighter underside and a darker top (Fig. 2). This ‘countershading’ suggests that Psittacosaurus was able to disguise its 3D shape and improve its camouflage because it counteracted the pattern of shadow cast by the body under sunlight (Fig. 3 ). The boundary of the lighter underside and darker top is at a low level on the body (Fig. 1), matching the pattern found in living animals that live in closed habitats with more diffused light conditions like forests (as opposed to open habitats like savannah with more direct sunlight) (Fig. 4) . This fits with the known forest habitat of Psittacosaurus, suggesting that countershading was used by dinosaurs in the same way as living animals!

Fig. 2: Revised life reconstruction of Psittacosaurus sp. SMF R 4970 based on the results of the two recent studies. Psittacosaurus is a two-legged, dog-sized Triceratops relative. Credit: Bob Nicholls/Paleocreations

Fig. 3: Countershading disguises an animal’s 3D shape when it is under sunlight as the body’s patterning counteracts the distribution of light and shadow on the body. (i) An evenly shaded, roughly cylindrical object is easy to see because of the shadow it casts. (ii) Countershading is a pattern of colouration that matches light shading with the portions of the object that are typically in shadow and dark shading with portions that are commonly exposed to direct light. (iii) A roughly cylindrical object that is countershaded therefore appears flat, because its shading counteracts the effect of its shadow.

Fig. 4: Modern animals with countershading. Notice how the white underside is low on the body like in Psittacosaurus? That’s because both animals lived in forests where the more diffused light favours graded or low-level countershading. Credit: By Ceasar Choi

The laser-basing imaging that Mr. Kaye and I employed is called laser-stimulated fluorescence or LSF imaging and reveals the colour patterns of Psittacosaurus better than ever before due to the scales of the skin fluorescing brightly (Fig. 5). The imaging also helped to clarify the lighter colour of the belly scales which is obscured by dark melanin pigment (a resistant pigment which colours our skin and hair) (Fig. 5) that possibly leaked from internal organs during the animal’s decomposition. The LSF principle involves photons from the laser interacting with atoms in the minerals of the fossil and then losing energy that is released as a different colour photon – it fluoresces. The technique provides an instant chemical map of a fossil that often reveals anatomical information that is invisible under normal lighting. Our Psittacosaurus specimen also preserves some strange long bristles on the tail which the LSF imaging shows have a similar fluorescent colour to the preserved skin (Fig. 5). We attribute this to calcium phosphate mineral salts that were incorporated into the keratin of the animal’s scales and bristles, providing clues to the bristle’s material make-up.

Fig 5: Laser-stimulated fluorescence (LSF) image of Psittacosaurus sp. SMF R 4970 revealing its colour patterns in unparalleled detail. Note its darker top and lighter underside that demonstrates countershading in dinosaurs. Credit: Thomas G Kaye & Michael Pittman.

Fig. 6: The tail bristles look similar to the spines and filaments of some modern birds, but these structure aren’t true feathers. Scale is 1cm. Photo credit: Sven Tränkner/Senckenburg Museum of Natural History

In a separate study published at the end of August, Mr. Kaye, Dr. Vinther (and his student Evan Saitta) and I teamed up with Gerald Mayr of the Senckenberg Museum of Natural History in Frankfurt who led us in an unparalleled description of the tail bristles. We revealed that they are arranged in bundles and possess a pulp that widens towards their base. Thinner variations of these structures are found in two other ornithischian dinosaur species (ornithischians are one of the two main groups of dinosaurs, the other being the saurischians which include the theropods [T.rex and their kin]), but their anatomy has yet to be studied in detail with the new technique. The similarity of the Psittacosaurus bristles to the spine and filaments of some modern birds that are not true feathers (Fig. 6) makes it uncertain if the structures of dinosaur skin - scales, bristles, filaments and feathers - all evolved from the same ancestral structure (or structures) in the first dinosaurs. Our work is an important piece to a very popular unfinished puzzle so like my previous article we’ll have to see what future research can reveal.



1. Vinther, J., Nicholls, R., Lautenschlager, S., Pittman, M., Kaye, T. G., Rayfield, E., Mayr, G. and Cuthill, I. C. 2016. 3D Camouflage in an Ornithischian Dinosaur. Current Biology. PDF -
Video summary -

2. Mayr, G., Pittman, M., Saitta, E., Kaye, T.G. & Vinther, J. Structure and homology of Psittacosaurus tail bristles. Palaeontology, 1-10.


Media coverage:

> BBC science news:
> National Geographic:
> SciShow video report:
> Dinosaur George podcast: and


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