[Paleontology • 2016] 3D Camouflage in an Ornithischian Dinosaur, Psittacosaurus Countershading

Countershading matches diffuse light in Psittacosaurus.

Photograph: Jakob Vinther   cell.com

SUMMARY

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.

Jakob Vinther, Robert Nicholls, Stephan Lautenschlager, Michael Pittman, Thomas G. Kaye, Emily Rayfield, Gerald Mayr and Innes C. Cuthill. 2016.  3D Camouflage in an Ornithischian Dinosaur. Current Biology. 26, 1–7. 

http://www.cell.com/pb-assets/journals/research/current-biology/S200backup/vinther.pdf

DOI: 10.1016/j.cub.2016.06.065

twitter.com/CurrentBiology/status/776142869417586693

Scientists reveal most accurate depiction of a dinosaur ever created | Elsa Panciroli https://www.theguardian.com/science/2016/sep/14/scientists-reveal-most-accurate-depiction-of-a-dinosaur-ever-created

This Dinosaur Wore Camouflage http://on.natgeo.com/2cKd89s  via @NatGeo

    

[Paleontology • 2016] Structure and Homology of Psittacosaurus Tail Bristles

A, the ‘beard’ of the turkey, Meleagris gallopavo (Galliformes). B, the spine on the head of the horned screamer, Anhima cornuta (Anseriformes). C, bristles on the head of the Congo peafowl, Afropavo congensis (Galliformes).

 Psittacosaurus sp. from the Early Cretaceous Jehol Biota of China (SMF R 4970).  A, overview of specimen. B, detail of tail section with bristles. Both scale bars represent 10 cm. 

  DOI:  10.1111/pala.12257 

Abstract

We examined bristle-like appendages on the tail of the Early Cretaceous basal ceratopsian dinosaur Psittacosaurus with laser-stimulated fluorescence imaging. Our study reveals previously unknown details of these structures and confirms their identification as integumentary appendages. For the first time, we show that most bristles appear to be arranged in bundles and that they exhibit a pulp that widens towards the bristle base. We consider it likely that the psittacosaur bristles are structurally and developmentally homologous to similar filamentous appendages of other dinosaurs, namely the basal heterodontosaurid Tianyulong and the basal therizinosauroid theropod Beipiaosaurus, and attribute the greater robustness of the bristles of Psittacosaurus to a higher degree of cornification and calcification of its integument (both skin and bristles). Although the psittacosaur bristles are probably homologous with avian feathers in their origin from discrete cell populations, it is uncertain whether they developed from a follicle, one of the developmental hallmarks of true feathers. In particular, we note a striking resemblance between the psittacosaur bristles and the cornified spine on the head of the horned screamer, Anhima cornuta, an extant anseriform bird. Similar, albeit thinner keratinous filaments of extant birds are the ‘beard’ of the turkey, Meleagris gallopavo, and the crown of the Congo peafowl, Afropavo congensis. All of these structures of extant birds are distinct from true feathers, and because at least the turkey beard does not develop from follicles, detailed future studies of their development would be invaluable towards deepening our understanding of dinosaur filamentous integumentary structures.

Keywords:  ceratopsian dinosaur; feather evolution; LSF imaging; Psittacosaurus; tail bristles

Figure 4. A, the ‘beard’ of the turkey, Meleagris gallopavo (Galliformes; uncatalogued mounted specimen on display in Senckenberg Natural History Museum). B, the spine on the head of the horned screamer, Anhima cornuta (Anseriformes; uncatalogued mounted specimen on display in the Senckenberg Natural History Museum). C, bristles on the head of the Congo peafowl, Afropavo congensis (Galliformes; uncatalogued mounted specimen on display in Senckenberg Natural History Museum). D, detail of longitudinal section through the base of an Anhima spine attached to a macerated skull (SMF 2479) to show the pulp, which is infilled with dense connective tissue; the tip of this spine is broken. E–F, detail of two psittacosaur bristles with pulp indicated by dashed lines in the greyscale images to the right. All scale bars represent 10 mm.

  DOI:  10.1111/pala.12257

Figure 1. Psittacosaurus sp. from the Early Cretaceous Jehol Biota of China (SMF R 4970).
A, overview of specimen. B, detail of tail section with bristles. Both scale bars represent 10 cm. 

Gerald Mayr, Michael Pittman, Evan Saitta, Thomas G. Kaye and Jakob Vinther. 2016. Structure and Homology of Psittacosaurus Tail Bristles. Palaeontology. DOI: 10.1111/pala.12257

  

Gerald Mayr, D. Stefan Peters, Gerhard Plodowski and Olaf Vogel. 2002. Bristle-like Integumentary Structures at the Tail of the Horned Dinosaur Psittacosaurus. Naturwissenschaften. 89; 361–365.  DOI: 10.1007/s00114-002-0339-6

http://www.senckenberg.de/files/content/forschung/abteilung/terrzool/ornithologie/psittacosaur.pdf