Swiss Journal of Geosciences

, Volume 103, Issue 2, pp 173–185 | Cite as

Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora)

  • James O. FarlowEmail author
  • Shoji Hayashi
  • Glenn J. Tattersall


X-ray computed tomography and petrographic thin sectioning were used to study internal features of the plates of the thyreophoran dinosaur Stegosaurus and the osteoderms of Alligator. Infrared thermographic imaging of basking caimans was used to examine possible differential blood flow to osteoderms and other parts of the skin. Multiple large openings in the Stegosaurus plate base lead to a linear, mesiodistally oriented vestibule, which in turn apically sends off multiply branching “pipes”. The pipes are best developed in the basal half of the plate, and communicate with cancellous regions (some of which presumably were vascular spaces) throughout the plate interior. Some internal vascular features also connect with vascular pits and grooves on the plate surface. Alligator osteoderms show a similar internal vascularity. In crocodylians, the osteoderms serve as armor and help to stiffen the back for terrestrial locomotion, but their vascularity enables them to be used as sources of calcium for egg shelling, as sites of lactate sequestration, and possibly for heat exchange with the external environment, as suggested by our infrared thermographic imaging of basking caimans. Thyreophoran osteoderms presumably had multiple functions as well. In Stegosaurus the potential thermoregulatory role of the plates may have been greater than in other thyreophorans, by virtue of their extensive external and internal vascularity, their large size, thin cross-sections above the plate base, dorsal position, and alternating arrangement.


Stegosaurus Crocodylians Osteoderms Reptilian thermoregulation X-ray computed tomography Infrared thermographic imaging 

Institutional abbreviations


Denver Museum of Nature and Science, Denver, Colorado, USA


Hayashibara Museum of Natural Sciences, Okayama, Japan


National Science Museum, Tokyo, Japan


National Museum of Natural History, Smithsonian Institution, Washington, DC, USA


Peabody Museum of Natural History, Yale University, New Haven, Connecticut, USA



We thank H.J. “Kirby” Siber and the Sauriermuseum Aathal (Switzerland) for inviting our participation in the 2009 Symposium on Stegosauria. D. Brinkman, K. Carpenter, B. Dattilo, P. Galton, K. Deal, K. Endo, M. Fox, S. Ishigaki, W. Joyce, Y. Kobayashi, M. Manabe, L. McWhinney, M. Okumura, K. Padian, F. Paladino, B. Shadle, S. Suzuki, T. Takemura, D. Thomas, M. Watabe, and J. Whitcraft variously made specimens in their collections available to us for study, assisted with CT scans or other images, provided financial support, or simply provided useful discussion. R. Elsey (Rockefeller Wildlife Refuge, Grand Chenier, Louisiana) provided us with a sample of alligator osteoderms. Financial support was provided by the Jurassic Foundation. R. Redelstorff and an anonymous reviewer offered comments that greatly improved our text.


  1. Bakker, R. T. (1986). The Dinosaur Heresies: New theories unlocking the mystery of the dinosaurs and their extinction (481 pp.). New York: William Morrow.Google Scholar
  2. Bartholomew, G. A., & Lasiewski, R. C. (1965). Heating and cooling rates, heart rate and simulated diving in the Galapagos marine iguana. Comparative Biochemistry and Physiology, 16, 573–582.CrossRefGoogle Scholar
  3. Bartholomew, G. A., & Tucker, V. A. (1963). Control of changes in body temperature, metabolism and circulation by the agamid lizard, Amphibolurus barbatus. Physiological Zoology, 36, 199–218.Google Scholar
  4. Blows, W. T. (2001a). Possible stegosaur dermal armor from the Lower Cretaceous of southern England. In K. Carpenter (Ed.), The Armored Dinosaurs (pp. 130–140). Bloomington, IN, USA: Indiana University Press.Google Scholar
  5. Blows, W. T. (2001b). Dermal armor of the polacanthine dinosaurs. In K. Carpenter (Ed.), The Armored Dinosaurs (pp. 363–385). Bloomington, IN, USA: Indiana University Press.Google Scholar
  6. Brinkman, D. B., & Conway, F. M. (1985). Textural and mineralogical analysis of a Stegosaurus plate. Compass (Sigma Gamma Epsilon), 63, 1–5.Google Scholar
  7. Buffrénil, V. de (1982). Morphogenesis of bone ornamentation in extant and extinct crocodilians. Zoomorphology, 99, 155–165.Google Scholar
  8. Buffrénil, V. de, Farlow, J. O., & Ricqlès, A. de (1986). Growth and function of Stegosaurus plates: evidence from bone histology. Paleobiology, 12, 459–473.Google Scholar
  9. Buss, I. O., & Estes, J. A. (1971). The functional significance of movements and positions of the pinnae of the African elephant, Loxodonta africana. Journal of Mammalogy, 52, 21–27.CrossRefGoogle Scholar
  10. Carpenter, K. (1998). Armor of Stegosaurus stenops, and the taphonomic history of a new specimen from Garden Park, Colorado. Modern Geology, 23, 127–144.Google Scholar
  11. Carpenter, K., Miles, C. A. & Cloward, K. (2001). New primitive stegosaur from the Morrison Formation, Wyoming. In K. Carpenter (Ed.), The Armored Dinosaurs (pp. 55–75). Bloomington, IN, USA: Indiana University Press.Google Scholar
  12. Carpenter, K., Sanders, F., McWhinney, L. A. & Wood, L. (2005). Evidence for predator-prey relationships: examples for Allosaurus and Stegosaurus. In K. Carpenter (Ed.), The Carnivorous Dinosaurs (pp. 325–350). Bloomington, IN, USA: Indiana University Press.Google Scholar
  13. Chinsamy-Turan, A. (2005). The microstructure of dinosaur bone: deciphering biology with fine-scale techniques (195 pp.). Baltimore: Johns Hopkins University Press.Google Scholar
  14. Colbert, E. H. (1981). A primitive ornithischian dinosaur from the Kayenta Formation of Arizona. Bulletin of the Museum of Northern Arizona, 53, 1–61.Google Scholar
  15. Czerkas, S. A. (1987). A reevaluation of the plate arrangement on Stegosaurus stenops. In S. J. Czerkas & E. C. Olson (Eds.), Dinosaurs Past and Present (Vol. II, pp. 82–89). Seattle: University of Washington Press.Google Scholar
  16. D’Emic, M. D., Wilson, J. A., & Chatterjee, S. (2009). The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India. Journal of Vertebrate Paleontology, 29, 165–177.CrossRefGoogle Scholar
  17. Dilkes, D., & Sues, H.-D. (2009). Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology, 29, 58–79.CrossRefGoogle Scholar
  18. Dzialowski, E. M., & O’Connor, M. P. (2004). Importance of the limbs in the physiological control of heat exchange in Iguana iguana and Sceloporus undulatus. Journal of Thermal Biology, 29, 299–305.CrossRefGoogle Scholar
  19. Farlow, J. O., Thompson, C. V., & Rosner, D. E. (1976). Plates of the dinosaur Stegosaurus: forced convection heat loss fins? Science, 192, 1123–1125.CrossRefGoogle Scholar
  20. Ford, T. L. (2000). A review of ankylosaur osteoderms from New Mexico and a preliminary review of ankylosaur armor. In S. G. Lucas & A.B. Heckert (Eds.), Dinosaurs of New Mexico (Vol. 17, pp. 157–176). New Mexico Museum of Natural History and Science Bulletin.Google Scholar
  21. Frey, E. (1988). Das Tragsystem der Krokodile–eine biomechanische und phylogenetische Analyse. Stuttgarter Beiträge zur Naturkunde Serie (Biologie), 426, 1–60.Google Scholar
  22. Galton, P. M. & Upchurch, P. (2004). Stegosauria. In D. B. Weishampel, P. Dodson & H. Osmólska (Eds.), The Dinosauria (2nd ed., pp. 343–362). Berkeley: University of California Press.Google Scholar
  23. Gilmore, C. W. (1914). Osteology of the armoured Dinosauria in the United States National Museum, with special reference to the genus Stegosaurus. United States National Museum Bulletin, 89, 1–143.Google Scholar
  24. Gould, S. J., & Vrba, E. S. (1982). Exaptation—a missing term in the science of form. Paleobiology, 8, 4–15.Google Scholar
  25. Gower, D. J., & Schoch, R. R. (2009). Postcranial anatomy of the rauisuchian archosaur Batrachotomus kupferzellensis. Journal of Vertebrate Paleontology, 29, 103–122.CrossRefGoogle Scholar
  26. Grigg, G. C., & Alchin, J. (1976). The role of the cardiovascular system in thermoregulation of Crocodylus johnstoni. Physiological Zoology, 49, 24–36.Google Scholar
  27. Grigg, G. C., Drane, C. R., & Courtice, G. P. (1979). Time constants of heating and cooling in the eastern water dragon, Physignathus lesueruii and some generalizations about heating and cooling in reptiles. Journal of Thermal Biology, 4, 95–103.CrossRefGoogle Scholar
  28. Grigg, G. C., & Seebacher, F. (1999). Field test of a paradigm: hysteresis of heart rate in thermoregulation by a free-ranging lizard (Pogona barbata). Proceedings of the Royal Society of London B, 266, 1291–1297.CrossRefGoogle Scholar
  29. Hagan, A. A., & Heath, J. E. (1980). Regulation of heat loss in the duck by vasomotion in the bill. Journal of Thermal Biology, 5, 95–101.CrossRefGoogle Scholar
  30. Hayashi, S. (2009). Bone histology of thyreophoran osteoderms. PhD Thesis, Hokkaido University, Hokkaido, Japan, 154 pp.Google Scholar
  31. Hayashi, S., Carpenter, C., Scheyer, T. M., Watabe, M., & Suzuki, D. (2010). Function and evolution of ankylosaur dermal armour. Acta Palaeontologica Polonica, 55, 213–228.CrossRefGoogle Scholar
  32. Hayashi, S., Carpenter, C., & Suzuki, D. (2009). Different growth patterns between the skeleton and osteoderms of Stegosaurus (Ornithischia, Thyreophora). Journal of Vertebrate Paleontology, 29, 123–131.CrossRefGoogle Scholar
  33. Hill, R. V. (2005). Integration of morphological data sets for phylogenetic analysis of Amniota: the importance of integumentary characters and increased taxonomic sampling. Systematic Biology, 54, 530–547.CrossRefGoogle Scholar
  34. Hill, R. V. (2006). Comparative anatomy and histology of xenarthran osteoderms. Journal of Morphology, 267, 1441–1460.CrossRefGoogle Scholar
  35. Hill, R. V., & Lucas, S. G. (2006). New data on the anatomy and relationships of the Paleocene crocodylian Akanthosuchus langstoni. Acta Palaeontologica Polonica, 51, 455–464.Google Scholar
  36. Hochscheid, S., Bentivegna, F., & Speakman, J. R. (2002). Regional blood flow in sea turtles: implications for heat exchange in an aquatic ectotherm. Physiological and Biochemical Zoology, 75, 66–76.CrossRefGoogle Scholar
  37. Hoefs, M. (2000). The thermoregulatory potential of Ovis horn cores. Canadian Journal of Zoology, 78, 1419–1426.CrossRefGoogle Scholar
  38. Hutton, J. M. (1986). Age determination of living Nile crocodiles from the cortical stratification of bone. Copeia, 1986, 332–341.CrossRefGoogle Scholar
  39. Jackson, D. C., Andrade, D. V., & Abe, A. S. (2003). Lactate sequestration by osteoderms of the broad-nose caiman, Caiman latirostris, following capture and forced submergence. Journal of Experimental Biology, 206, 3601–3606.CrossRefGoogle Scholar
  40. Klein, N., Scheyer, T., & Tütken, T. (2009). Skeletochronology and isotopic analysis of a captive individual of Alligator mississippiensis Daudin, 1802. Fossil Record, 12, 121–131.CrossRefGoogle Scholar
  41. Levrat-Calviac, V., & Zylberberg, L. (1986). The structure of the osteoderms in the gekko: Tarentola mauritanica. American Journal of Anatomy, 176, 437–446.CrossRefGoogle Scholar
  42. Maidment, S. C. R., Norman, D. B., Barrett, P. M., & Upchurch, P. (2008). Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia). Journal of Systematic Paleontology, 6, 367–407.CrossRefGoogle Scholar
  43. Main, R. P., Ricqlès, A. de, Horner, J. R., & Padian, K. (2005). The evolution and function of thyreophoran dinosaur scutes: implications for plate function in stegosaurs. Paleobiology, 31, 291–314.Google Scholar
  44. Marsh, O. C. (1896). The Dinosaurs of North America. U.S. Geological Survey 16th Annual Report, 1894–1895 (pp. 133–244).Google Scholar
  45. Mateus, O., Maidment, S. C. R., & Christiansen, N. A. (2009). A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs. Proceedings of the Royal Society B, 276, 1815–1821.CrossRefGoogle Scholar
  46. McWhinney, L. A., Rothschild, B. M. & Carpenter, K. (2001). Posttraumatic chronic osteomyelitis in Stegosaurus dermal spikes. In: K. Carpenter (Ed.), The Armored Dinosaurs (pp. 141–156). Bloomington, IN, USA: Indiana University Press.Google Scholar
  47. Molnar, R. E. (2001). Armor of the small ankylosaur Minmi. In K. Carpenter (Ed.), The Armored Dinosaurs (pp. 341–362). Bloomington, IN, USA: Indiana University Press.Google Scholar
  48. Mortola, J. P., & Lanthier, C. (2004). Scaling the amplitudes of the circadian pattern of resting oxygen consumption, body temperature and heart rate in mammals. Comparative Biochemistry & Physiology A, 139, 83–95.CrossRefGoogle Scholar
  49. Moss, M. L. (1972). The vertebrate dermis and the integumental skeleton. American Zoologist, 12, 27–34.Google Scholar
  50. O’Connor, M. P., & Dodson, P. (1999). Biophysical constraints on the thermal ecology of dinosaurs. Paleobiology, 25, 341–368.Google Scholar
  51. Ostrom, J. H., & McIntosh, J. S. (1966). Marsh’s dinosaurs: the collections from Como Bluff (388 pp.). New Haven: Yale University Press.Google Scholar
  52. Phillips, P. K., & Heath, J. E. (1992). Heat exchange by the pinna of the African elephant (Loxodonta africana). Comparative Biochemistry and Physiology, 101A, 693–699.Google Scholar
  53. Phillips, P. K., & Heath, J. E. (1995). Dependence of surface temperature regulation on body size in terrestrial mammals. Journal of Thermal Biology, 3, 281–289.CrossRefGoogle Scholar
  54. Phillips, P. K., & Heath, J. E. (2001). An infrared thermographic study of surface temperature in the euthermic woodchuck (Marmota monax). Comparative Biochemistry & Physiology A, 129, 557–562.CrossRefGoogle Scholar
  55. Phillips, P. K., & Sanborn, A. F. (1994). An infrared, thermographic study of surface temperature in three ratites: ostrich, emu and double-wattled cassowary. Journal of Thermal Biology, 6, 423–430.CrossRefGoogle Scholar
  56. Picard, K., Festa-Bianchet, M., & Thomas, D. (1996). The cost of horniness: heat loss may counter sexual selection for large horns in temperate bovids. Écoscience, 3, 280–284.Google Scholar
  57. Picard, K., Thomas, D. W., Festa-Bianchet, M., Belleville, F., & Laneville, A. (1999). Differences in the thermal conductance of tropical and temperate bovid horns. Écoscience, 6, 148–158.Google Scholar
  58. Redelstorff, R., & Sander, P. M. (2009). Long and girdle bone histology of Stegosaurus: implications for growth and life history. Journal of Vertebrate Paleontology, 29, 1087–1099.CrossRefGoogle Scholar
  59. Reid, R. E. H. (1996). Bone histology of the Cleveland-Lloyd dinosaurs and of dinosaurs in general, Part I: Introduction: Introduction to bone tissues. Brigham Young University Geology Studies, 41, 25–71.Google Scholar
  60. Richardson, K. C., Webb, G. J. W., & Manolis, S. C. (2002). Crocodiles: inside out. A guide to the crocodilians and their functional morphology (172 pp.). Chipping Norton: Surrey Beatty & Sons.Google Scholar
  61. Robertson, S. L., & Smith, E. N. (1981). Thermal conductance and its relation to thermal time constants. Journal of Thermal Biology, 6, 129–143.CrossRefGoogle Scholar
  62. Scheyer, T. M., & Sánchez-Villagra, M. R. (2007). Carapace bone histology in the giant turtle Stupendemys geographicus (Pleurodira: Podocnemicae): phylogenetic and functional aspects. Acta Palaeontologica Polonica, 52, 137–154.Google Scholar
  63. Scheyer, T. M., & Sander, P. M. (2004). Histology of ankylosaur osteoderms: implications for systematics and function. Journal of Vertebrate Paleontology, 24, 874–893.CrossRefGoogle Scholar
  64. Seebacher, F. (2000). Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius). Journal of Theoretical Biology, 203, 97–109.CrossRefGoogle Scholar
  65. Seebacher, F., & Franklin, C. E. (2007). Redistribution of blood within the body is important for thermoregulation in an ectothermic vertebrate (Crocodylus porosus). Journal of Comparative Physiology B, 177, 841–848.CrossRefGoogle Scholar
  66. Seidel, M. R. (1979). The osteoderms of the American alligator and their functional significance. Herpetologica, 35, 375–380.Google Scholar
  67. Siber, H. J. & Möckli, U. (2009) The Stegosaurs of the Sauriermuseum Aathal. Aathal, 56 pp.Google Scholar
  68. Smith, E. N. (1976). Heating and cooling rates of the American alligator, Alligator mississippiensis. Physiological Zoology, 49, 37–48.Google Scholar
  69. Smith, E. N. (1979). Behavioral and physiological thermoregulation of crocodilians. American Zoologist, 19, 239–247.Google Scholar
  70. Smith, E. N., & Adams, S. R. (1978). Thermoregulation of small American alligators. Herpetologica, 34, 406–408.Google Scholar
  71. Smith, E. N., Robertson, S., & Davies, D. G. (1978). Cutaneous blood flow during heating and cooling in the American alligator. American Journal of Physiology, 235, R160–R167.Google Scholar
  72. Smith, E. N., Standora, E. A., & Robertson, S. L. (1984). Physiological thermoregulation of mature alligators. Comparative Biochemistry and Physiology, 77A, 189–193.Google Scholar
  73. Speakman, J. R., & Ward, S. (1998). Infrared thermography: principles and applications. Zoology, 101, 224–232.Google Scholar
  74. Tattersall, G. J., Andrade, D. V., & Abe, A. S. (2009). Heat exchange from the toucan bill reveals a controllable vascular thermal radiator. Science, 325, 468–470.CrossRefGoogle Scholar
  75. Taylor, C. R. (1966). The vascularity and possible thermoregulatory function of the horns in goats. Physiological Zoology, 39, 127–139.Google Scholar
  76. Tucker, A. D. (1997). Validation of skeletochronology to determine age of freshwater crocodiles (Crocodylus johnstoni). Marine & Freshwater Research, 48, 343–351.CrossRefGoogle Scholar
  77. Vickaryous, M. K., & Hall, B. K. (2008). Development of the dermal skeleton in Alligator mississippiensis (Archosauria, Crocodylia) with comments on homology of osteoderms. Journal of Morphology, 269, 398–422.CrossRefGoogle Scholar
  78. Vickaryous, M. K., & Sire, J.-Y. (2009). The integumentary skeleton of tetrapods: origin, evolution, and development. Journal of Anatomy, 214, 441–464.CrossRefGoogle Scholar
  79. Weathers, W. W., & White, F. N. (1971). Physiological thermoregulation in turtles. American Journal of Physiology, 221, 704–710.Google Scholar
  80. White, F. N. (1973). Temperature and the Galapagos marine iguana–insights into reptilian thermoregulation. Comparative Biochemistry and Physiology, 45A, 503–513.Google Scholar
  81. Wright, P. (1984). Why do elephants flap their ears? South African Journal of Zoology, 19, 266–269.Google Scholar
  82. Zylberberg, L., & Castanet, J. (1985). New data on the structure and growth of the osteoderms in the reptile Anguis fragilis L. (Anguidae, Squamata). Journal of Morphology, 186, 327–342.CrossRefGoogle Scholar

Copyright information

© Swiss Geological Society 2010

Authors and Affiliations

  • James O. Farlow
    • 1
    Email author
  • Shoji Hayashi
    • 2
  • Glenn J. Tattersall
    • 3
  1. 1.Department of GeosciencesIndiana-Purdue UniversityFort WayneUSA
  2. 2.Department of Earth and Planetary Sciences, Graduate School of ScienceHokkaido UniversitySapporoJapan
  3. 3.Department of Biological SciencesBrock UniversitySt. CatharinesCanada

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