Do iguanas have an amygdala?

[thelurkinghorror]

@Wesley_Clark

The amygdala is part of the limbic system, and my understanding is the limbic system is not present in reptiles.

I presume that’s based on MacLean’s theory (low “reptile brain”, middle “old mammalian brain” w/ limbic system, high “new mammalian brain”)? Evidence suggests that this is an oversimplification, and shouldn’t be treated as a hard division. Reptiles have a system of structures that work similar to a limbic system, no matter what name you actually give it.

@Wikipedia

However, while the categorization into structures is reasonable, the recent studies of the limbic system of tetrapods, both living and extinct, have challenged several aspects of this hypothesis, notably the accuracy of the terms “reptilian” and “old mammalian”. The common ancestors of reptiles and mammals had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established. Further, birds, which evolved from the dinosaurs, which in turn evolved separately but around the same time as the mammals, have a well-developed limbic system. While the anatomic structures of the limbic system are different in birds and mammals, there are functional equivalents.