Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora) James O. Farlow • Shoji Hayashi • Glenn J. Tattersall Received: 9 September 2009 / Accepted: 17 May 2010 Ó Swiss Geological Society 2010 Abstract 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. Mul- tiple large openings in the Stegosaurus plate base lead to a linear, mesiodistally oriented vestibule, which in turn api- cally sends off multiply branching ‘‘pipes’’. The pipes are best developed in the basal half of the plate, and commu- nicate 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 osteo- derms 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. Keywords Stegosaurus Á Crocodylians Á Osteoderms Á Reptilian thermoregulation Á X-ray computed tomography Á Infrared thermographic imaging Institutional abbreviations DMNH Denver Museum of Nature and Science, Denver, Colorado, USA HMNS Hayashibara Museum of Natural Sciences, Okayama, Japan NSM-PV National Science Museum, Tokyo, Japan USNM National Museum of Natural History, Smithsonian Institution, Washington, DC, USA YPM Peabody Museum of Natural History, Yale University, New Haven, Connecticut, USA Introduction Dermal ossifications have repeatedly evolved in amniotes: placodonts, pareiasaurs, chelonians, squamates, crocody- lians and closely related archosaurs, ceratosaurs, tita- nosaurs, thyreophorans, and cingulates (cf. Moss 1972; Buffre ´nil 1982; Zylberberg and Castanet 1985; Levrat- Calviac and Zylberberg 1986; Scheyer and Sander 2004; Hill 2005, 2006; Hill and Lucas 2006; Scheyer and Sa ´nchez-Villagra 2007; Maidment et al. 2008; Vickaryous Editorial handling: Jean-Paul Billon-Bruyat & Daniel Marty. J. O. Farlow (&) Department of Geosciences, Indiana-Purdue University, 2101 East Coliseum Boulevard, Fort Wayne, IN 46805, USA e-mail: [email protected]S. Hayashi Department of Earth and Planetary Sciences, Graduate School of Science, Hokkaido University, N10 W8, Sapporo 060-0810, Japan G. J. Tattersall Department of Biological Sciences, Brock University, St. Catharines, ON, Canada Swiss J Geosci DOI 10.1007/s00015-010-0021-5
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Internal vascularity of the dermal plates of Stegosaurus(Ornithischia, Thyreophora)
James O. Farlow • Shoji Hayashi • Glenn J. Tattersall
Received: 9 September 2009 / Accepted: 17 May 2010
� Swiss Geological Society 2010
Abstract 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. Mul-
tiple large openings in the Stegosaurus plate base lead to a
linear, mesiodistally oriented vestibule, which in turn api-
cally sends off multiply branching ‘‘pipes’’. The pipes are
best developed in the basal half of the plate, and commu-
nicate 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 osteo-
derms 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,
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