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The evolution and function of thyreophoran dinosaur scutes: Implications for plate function in stegosaurs

Published online by Cambridge University Press:  08 April 2016

Russell P. Main
Department of Organismal and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138. E-mail:
Armand de Ricqlès
Équipe Formations Squelettiques, URA CNRS 11 37, Université Paris VII, 75251 Paris cedex 05, France, and Collège de France, Paris, France. E-mail:
John R. Horner
Museum of the Rockies, Montana State University, Bozeman, Montana 59717-0040. E-mail:
Kevin Padian
Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, California 94720-3140. E-mail:


The evolution of scutes in thyreophoran dinosaurs, based on Scutellosaurus, Scelidosaurus, Stegosaurus, and several ankylosaurs, began with small rounded or ovoid structures that typically had slight, anteroposteriorly oriented keels. These scutes were elaborated in two general and overlapping ways: they could flare laterally and asymmetrically beneath the keels that mark the anteroposterior axis, and they could be hypertrophied in their distal growth to produce plates, spikes, and other kinds of ornamentation. Stegosaurus plates and spikes are thus primarily hypertrophied keels of primitive thyreophoran scutes, sometimes with elaboration of dermal bone around their pustulate bases. Histologically, most thyreophoran scute tissues comprise secondary trabecular medullary bone that is sandwiched between layers of compact primary bone. Some scutes partly or mostly comprise anatomically metaplastic bone, that is, ossified fibrous tissue that shows incremental growth.

The “plumbing” of Stegosaurus plates was not apparently built to support a “radiator” system of internal blood vessels that communicated with the outside of the plates and coursed along their external surfaces to return heated or cooled blood to the body core. Possibly a purely external system supported this function but there is no independent evidence for it. On the other hand, many of the vascular features in stegosaurian plates and spikes reflect bautechnisches artifacts of growth and production of bone. Surface vascular features likely supported bone growth and remodeling, as well as the blood supply to a keratinous covering. When the gross and microstructural features of the plates and spikes are viewed in phylogenetic context, no clear pattern of thermoregulatory function emerges, though an accessory role cannot be eliminated in certain individual species. It seems more likely, as in other groups of dinosaurs, that the variation of dermal armor form in stegosaurs was primarily linked to species individuation and recognition, perhaps secondarily to inter- and intraspecific display, and rarely to facultative thermoregulation.

Copyright © The Paleontological Society 

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Literature Cited

Barrick, R. E., Stoskopf, M. K., Marcot, J. D., Russell, D. A., and Showers, W. J. 1998. The thermoregulatory functions of the Triceratops frill and horns: heat flow measured with oxygen isotopes. Journal of Vertebrate Paleontology 18:746750.CrossRefGoogle Scholar
Beresford, W. A. 1981. Chondroid bone, secondary cartilage and metaplasia. Urban and Schwarzenberg, Munich.Google Scholar
Blows, W. T. 1987. The armored dinosaur Polacanthus foxi from the Lower Cretaceous of the Isle of Wight. Palaeontology 30:557580.Google Scholar
Blows, W. T. 2001. Dermal armor of the polacanthine dinosaurs. Pp. 363385in Carpenter, 2001b.Google Scholar
Buffrénil, V. de, Farlow, J. O., and de Ricqlès, A. 1986. Growth and function of Stegosaurus plates: evidence from bone histology. Paleobiology 12:459473.CrossRefGoogle Scholar
Carpenter, K. 1997. Ankylosaurs. Pp. 307316in Farlow, J. O. and Brett-Surman, M. K., eds. The complete dinosaur. Indiana University Press, Bloomington.Google Scholar
Carpenter, K. 1998. Armor of Stegosaurus stenops, and the taphonomic history of a new specimen from Garden Park, Colorado. Modern Geology 23:127144.Google Scholar
Carpenter, K. 2001a. Phylogenetic analysis of the Ankylosauria. Pp. 455483in Carpenter, 2001b.Google Scholar
Carpenter, K. 2001b. The armored dinosaurs. Indiana University Press, Bloomington.Google Scholar
Colbert, E. H. 1981. A primitive ornithischian dinosaur from the Kayenta Formation of Northern Arizona. Museum of Northern Arizona Press Bulletin 53.Google Scholar
Farlow, J. O., Thompson, C. V., and Rosner, D. E. 1976. Plates of the dinosaur Stegosaurus: forced convection heat loss fins? Science 192:11231125.CrossRefGoogle ScholarPubMed
Galton, P. M., and Upchurch, P. 2004. Stegosauria. Pp. 343382in Weishampel, D., Osmolska, H., and Dodson, P., eds. The Dinosauria, 2d ed.Princeton University Press, Princeton, N.J.CrossRefGoogle Scholar
Geist, V. 1968. Horn-like structures as rank symbols, guards and weapons. Nature 220:813814.CrossRefGoogle ScholarPubMed
Gould, S. J. 1974. The evolutionary significance of “bizarre” structures: antler size and skull size in the “Irish Elk,” Megaceros giganteus. Evolution 28:191220.Google Scholar
Gould, S. J. 2002. The structure of evolutionary theory. Belknap Press of Harvard University Press, Cambridge.Google Scholar
Gould, S. J., and Lewontin, R. C. 1979. The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London B 205:581598.CrossRefGoogle Scholar
Haines, R. W., and Mohuiddin, A. 1968. Metaplastic bone. Journal of Anatomy 103:527538.Google ScholarPubMed
Hoefs, M. 2000. The thermoregulatory potential of Ovis horn cores. Canadian Journal of Zoology 78:14191426.CrossRefGoogle Scholar
Horner, J. R., de Ricqlès, A. J., and Padian, K. 2000. The bone histology of the hadrosaurid dinosaur Maiasaura peeblesorum: growth dynamics and physiology based on an ontogenetic series of skeletal elements. Journal of Vertebrate Paleontology 20:109123.CrossRefGoogle Scholar
Levrat-Calviac, V., and Zylberberg, L. 1986. The structure of the osteoderms in the gekko: Tarentola mauritanica. American Journal of Anatomy 176:437446.CrossRefGoogle ScholarPubMed
Norman, D. B. 1985. The illustrated encyclopedia of dinosaurs. Salamander Books, London.Google Scholar
Norman, D. B. 2000. Professor Richard Owen and the important but neglected dinosaur Scelidosaurus harrisonii. Historical Biology 14:235253.CrossRefGoogle Scholar
Norman, D. B. 2001a. Scelidosaurus, the earliest complete dinosaur. Pp. 325in Carpenter, 2001b.Google Scholar
Norman, D. B. 2001b. The anatomy and systematic position of Scelidosaurus harrisonii Owen, 1861. Journal of Vertebrate Paleontology 21(Suppl. to No. 3):84A.Google Scholar
Ostrom, J. H., and McIntosh, J. 1966. Marsh's dinosaurs: the collections from Como Bluff. Yale University Press, New Haven, Conn.Google Scholar
Owen, R. 1846. Archetypes and homologies of the vertebrate skeleton. John Van Voorst, London.Google Scholar
Owen, R. 1861. A monograph of the fossil Reptilia of the Liassic Formations, Part first. Scelidosaurus harrisonii. Palaeontographical Society, London.Google Scholar
Owen, R. 1863. A monograph of the fossil Reptilia of the Liassic Formations, Part second. Scelidosaurus harrisonii. Continued. Palaeontographical Society, London.Google Scholar
Padian, K. 1987. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona). Geology 17:438441.2.3.CO;2>CrossRefGoogle Scholar
Padian, K. 2001. Cross-testing adaptive hypotheses: phylogenetic analysis and the origin of bird flight. American Zoologist 41:598607.Google Scholar
Padian, K., de Ricqlès, A. J., and Horner, J. R. 2001. Dinosaurian growth rates and bird origins. Nature 412:405408.CrossRefGoogle ScholarPubMed
Phillips, P. K., and Heath, J. E. 1992. Heat exchange by the pinna of the African elephant (Loxodonta africana). Comparative Biochemistry and Physiology A 101:693699.CrossRefGoogle Scholar
Picard, K., Festa-Bianchet, M., and Thomas, D. 1996. The cost of horniness: heat loss may counter sexual selection for large horns in temperate bovids. Ecoscience 3:280284.CrossRefGoogle Scholar
Picard, K., Thomas, D., and Festa-Bianchet, M. 1999. Differences in the thermal conductance of tropical and temperate bovid horns. Ecoscience 6:148158.CrossRefGoogle Scholar
Price, T. 1998. Sexual selection and natural selection in bird speciation. Philosophical Transactions of the Royal Society of London B 353:251260.CrossRefGoogle Scholar
Reid, R. 1996. Bone histology of the Cleveland-Lloyd dinosaurs and of dinosaurs in general, Part I. introduction: introduction to bone tissues. Brigham Young University Geological Studies 41:2571.Google Scholar
Ricqlès, A. de, Superbiola, X. Pereda, Gasparini, Z., and Olivero, E. 2001. Histology of dermal ossifications in an ankylosaurian dinosaur from the Late Cretaceous of Antarctica. Asociación Paleontológica Argentina, Publicación Especial 7:171174.Google Scholar
Rosenbaum, J. N., and Padian, K. 2000. New material of the basal thyreophoran Scutellosaurus lawleri from the Kayenta Formation (Lower Jurassic) of Arizona. PaleoBios 20:1323.Google Scholar
Sampson, S. D. 1999. Sex and destiny: the role of mating signals in speciation and macroevolution. Historical Biology 13:173197.CrossRefGoogle Scholar
Scheyer, T., and Sander, P. M. 2004. Histology of ankylosaur osteoderms: implications for systematics and function. Journal of Vertebrate Paleontology. 24:874893.CrossRefGoogle Scholar
Sereno, P. C. 1986. Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2:234256.Google Scholar
Stonehouse, B. 1968. Thermoregulatory function of growing antlers. Nature 218:870872.CrossRefGoogle Scholar
Taylor, C. R. 1966. The vascularity and possible thermoregulatory function of the horns in goats. Physiological Zoology 39:127139.CrossRefGoogle Scholar
Vrba, E. S. 1984. Evolutionary pattern and process in the sister-group Alcelaphini-Aepycerotini (Mammalia: Bovidae). Pp. 6279in Eldredge, N. and Stanley, S. M., eds. Living fossils. Springer, Berlin.CrossRefGoogle Scholar
Waldo, C. M., Wislocki, G. B., and Fawcett, D. W. 1949. Observations on the blood supply of growing antlers. American Journal of Anatomy 84:2761.CrossRefGoogle ScholarPubMed
Wheeler, P. E. 1978. Elaborate CNS cooling structures in large dinosaurs. Nature 275:441443.CrossRefGoogle ScholarPubMed
Wilson, J. W. 1994. Histological techniques. Pp. 205234in Leiggi, P. and May, P., eds. Vertebrate paleontological techniques, Vol. 1. Cambridge University Press, New York.Google Scholar
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