Recent molecular evidence suggests that pinnipeds evolved from a bearlike ancestor about 23 million years ago during the late Oligocene or early Miocene epochs, a transitional period between the warmer Paleogene and cooler Neogene period.
By studying the Rocky Mountains in Colorado, Idaho, and Wyoming, Leopold helped recreate the paleoenvironment of the Paleogene and Neogene periods.
The term was used as a rock type name for some of the Paleogene igneous rocks of Scotland.
Birds, which were already well established by the end of the Cretaceous, also experienced an adaptive radiation as they took over the skies left empty by the now extinct Pterosaurs.
Taken together, these fossils place the origin of the Papilionoidea in the latest Mesozoic or early Paleogene, while the extant families emerged approximately the early Eocene onwards.
The mountains consist primarily of sedimentary rock, limestone, sandstone and shale, of Jurassic, Cretaceous and Paleogene origin on a Precambrian granitic basement.
They are sometimes placed as a tribe Eobelini, but the tribes of Belinae are attested in the Paleogene; the radiation of the Belinae subfamilies thus probably took place later in the Cretaceous.
The Flora family of asteroids may be the source of the Chicxlub (Cretaceous–Paleogene) impactor, the likely culprit in the extinction of the dinosaurs.
The main evidence for the Alvarez hypothesis that a single impact resulted in the Cretaceous–Paleogene extinction event that killed the dinosaurs has come from the presence around the world of shocked quartz granules, glass spherules and tektites embedded in a layer of clay with extremely high levels of iridium, all signs of an asteroid impact.