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 b y the oxygen isotopic composition of bone phosphate (delta(p)). Intrabone a nd interbone delta(p) variations indicate heat flow within an individual an d can be used to establish thermoregulatory strategies such as homeothermy and regional heterothermy. This method is applied to an individual Tricerat ops skeleton where the results suggest very high and uniform heat flow thro ugh the parietal frill, maintaining mean frill temperatures between 0-4 deg rees 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 thermor egulatory structures with the horn cores interpreted as being especially im portant in the stabilization of brain temperatures at extreme ambient tempe ratures and the frill serving a more consistent role in body temperature re gulation.