Ceratopsians - Indentations in Frills?

[dgmilner]

A number of models of ceratopsians that have circular indentations in their frills have been produced in recent years. I know that in some cases - Torosaurus, for example - there were holes in the frill bone but were there indentations in the skin where the holes were? What is the evidence for the indentations? 

[Papi-Anon]

Circular indentations I can't say anything about, but I had a professor show us slides years back of ceratopsian frills having indentations for blood vessels and proposing that the frills were a body-temperature regulating system similar to African elephants' ears.