The primitive mammal-like reptiles, the Pelycosauria, became extinct, but they left behind a variety of advanced mammallike reptiles collectively termed the Therapsida. Despite therapsid abundance and diversity during much of the Triassic, only one kind is portrayed here -- the imposing carnivorous beast Cynognathus -- the four-legged animal in the foreground. Many therapsids were able to assume a more nearly upright posture at times, in sharp contrast to the sprawling mode of the pelycosaurs and the labyrinthodonts.

True conifers made their appearance in the drier, more upland settings and assumed a steadily more important role as humid, equable climates deteriorated. The petrified logs found in Triassic strata of the Petrified Forest National Monument in Arizona are of the conifer Araucarioxylon, the majestic tree that towers over the beginning of the Triassic section of the mural. Cycads, with their crowns of palmlike leaves, appeared in the late Carboniferous and multiplied to become an important component of the vegetation. Coexisting with the true cycads was another type of gymnospermous seed plant, cycadeoids, that had a generally similar appearance.