I recently saw a claim that Gallifreyans are reptiles.
I know that their normal internal temperature is significantly lower that that of humans.
From Wikipedia (emphasis mine):
Physiological differences from humans include two hearts which normally beat at 170 beats per minute, an internal body temperature of 15 degrees Celsius (59 degrees Fahrenheit) and a "respiratory bypass system" that allows them to survive strangulation. Time Lords can also survive full exposure to the vacuum of space with no ill effects, though when in a vacuum for an extended period, a Time Lord must take a supply of air along or suffocate. Time Lords also seem to have an increased resilience to higher frequencies of sound, as seen in "The Christmas Invasion" and "Partners in Crime". If severely injured, Time Lords can go into a healing coma which lowers their body temperature to below freezing.
However, that alone does not indicate being reptiles. It doesn't even indicate their being ectothermic (cold blooded). They could be endotherms with a lower internal body temperature than humans.
Is there any definitive evidence in the show (books, comics, etc) or in interviews or behind-the-scenes resources as to this?