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.2016 Sep 26;26(18):2456-2462.
doi: 10.1016/j.cub.2016.06.065. Epub 2016 Sep 15.

3D Camouflage in an Ornithischian Dinosaur

Affiliations

3D Camouflage in an Ornithischian Dinosaur

Jakob Vinther et al. Curr Biol..

Abstract

Countershading was one of the first proposed mechanisms of camouflage [1, 2]. A dark dorsum and light ventrum counteract the gradient created by illumination from above, obliterating cues to 3D shape [3-6]. Because the optimal countershading varies strongly with light environment [7-9], pigmentation patterns give clues to an animal's habitat. Indeed, comparative evidence from ungulates [9] 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 [10-15]. Here we present a study of an exceptionally well-preserved specimen of Psittacosaurus sp. from the Chinese Jehol biota [16, 17]. This Psittacosaurus was countershaded [16] 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. VIDEO ABSTRACT.

Keywords: Jehol biota; Lagerstätte; Yixian Formation; behavioral ecology; countershading; defensive coloration; paleocolor; paleoenvironment; soft-tissue preservation; taphonomy.

Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

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Figures

Image 1
Graphical abstract
Figure 1
Figure 1
Psittacosaurus sp. SMF R 4970, Whole Specimen (A) Specimen photographed under crossed polarized light. (B) Interpretative drawing, showing the distribution of pigment patterns, skin, and bones. Green indicates forelimb bones, blue indicates hindlimb bones, purple indicates sacral elements, red indicates cranial elements, and buff yellow indicates vertebral column.
Figure 2
Figure 2
Details ofPsittacosaurus sp. SMF R 4970, Photographed under Crossed Polarized Light Overview (A); tail region, showing countershading gradient (B); belly with lighter pigmentation (lower-left corner) and a dorsoventral pigmentation gradient (C); left forelimb with raised clusters of pigmented scales (D); left hindlimb preserving external disruptive patterns and striping on internal leg (E); head with patches of intensely pigmented integument (F); pigmented ischial callosity and cloacal region (G); integument associated with the right leg (H); detail of pigment patterns associated with the proximal tail region, dorsolateral surface (I); pigment patterns associated with the lateral torso (J); and pigment patterns associated with the distal tail region (K). Jb, jugal boss; Pfb, prefrontal boss. Scale bars represent 50 mm (B–G), 20 mm (H), and 10 mm (I–K).
Figure 3
Figure 3
Model ofPsittacosaurus Based on Skin and Pigmentation Patterns on SMF R 4970 Left lateral view (A), posterior view (B), right lateral view (C), and anterior view (D). See also Data S1 and S2.
Figure 4
Figure 4
TestingPsittacosaurus Countershading in Natural Conditions (A–F) Gray colored cast without bristles attached, imaged under “closed habitat” conditions (A–C) and direct illumination (D–F). The model is shown as imaged in natural environment (A and D), masked (B and E), and in inverse color (C and F). (G and H) Predicted boundaries of rapid transition from dark to light skin for countershading in the diffuse illumination of closed habitats (blue) and of direct lighting in a sunny open habitat (orange). Stippled lines indicate 95% confidence intervals.
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References

    1. Poulton E.B. Second Edition. Kegan Paul, Trench, Trübner; 1890. The Colours of Animals: Their Meaning and Use, Especially Considered in the Case of Insects.
    1. Thayer A.H. The law which underlies protective coloration. Auk. 1896;13:477–482.
    1. Ruxton G.D., Speed M.P., Kelly D.J. What, if anything, is the adaptive function of countershading? Anim. Behav. 2004;68:445–451.
    1. Caro T. Concealing coloration in animals. Q. Rev. Biol. 2014;89:63.
    1. Rowland H.M. From Abbott Thayer to the present day: what have we learned about the function of countershading? Philos. Trans. R. Soc. Lond. B Biol. Sci. 2009;364:519–527. - PMC - PubMed

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