Alt text: Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.
Alt text: Detectives say the key to tracking down the source of the kites was a large wall map covered in thumbtacks and string. 'It's the first time that method has ever actually worked,' said a spokesperson.
XKCD 3122: Bad Map Projection: Interrupted Spheres
Alt text: During the most recent glacial maximum, it's believed that land bridges extended from the surfaces and connected several of the spheres together.