Why is the amygdala sometimes called the archistriatum?

The amygdala is referred to as the archistriatum because it is the oldest component of the basal ganglia from a phylogenetic perspective.1

In the classification of these structures, the term "archistriatum" denotes this evolutionary seniority, distinguishing it from the paleostriatum (the globus pallidus) and the neostriatum (the caudate nucleus and putamen).1