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The basal ganglia are present in all vertebrates, and so their evolution probably substantially predates the emergence of reptiles. Similarly, brain structures included in the paleomammalian complex are not unique to mammals, and many non-mammalian vertebrates display the nurturing and child-rearing behaviors attributed to it. Sauropsids, a classification encompassing birds, reptiles, and dinosaurs, were all subsequently discovered to have brain structures similar in function to what MacLean called the neomammalian complex, which indicates that the evolution of these structures also predates the evolution of mammals. Sophisticated mental abilities once thought to be exclusive to mammals, such as toolmaking, are also present in some species of birds.