The thermoregulatory functions of the Triceratops frill and horns:: Heat flow measured with oxygen isotopes

Variability of body temperature within fossil vertebrates can be measured by the oxygen isotopic composition of bone phosphate (delta(p)). Intrabone and interbone delta(p) variations indicate heat flow within an individual and can be used to establish thermoregulatory strategies such as homeothermy and regional heterothermy. This method is applied to an individual Triceratops skeleton where the results suggest very high and uniform heat flow through the parietal frill, maintaining mean frill temperatures between 0-4 degrees C below the body core. Heat flow to the postorbital horn-core is much more variable. The frill and horn cores of Triceratops were used as thermoregulatory structures with the horn cores interpreted as being especially important in the stabilization of brain temperatures at extreme ambient temperatures and the frill serving a more consistent role in body temperature regulation.