Laurasiatheria Laurasiatheria Laurasiatheria is a clade of placental mammals that originated on the northern supercontinent of Laurasia 99 million years ago. The clade includes shrews, pangolins, bats, whales, carnivorans, odd-toed and even-toed ungulates, among others. Laurasiatheria was discovered on the basis of the similar gene sequences shared by the mammals belonging to it; no anatomical features have yet been found that unite the group. The Laurasiatheria clade is based on DNA sequence analyses and retrotransposon presence/absence data. The name comes from the theory that these mammals evolved on the supercontinent of Laurasia, after it split from Gondwana when Pangaea broke up.
Gondwana Ice House to Hot House. By the end of the Ordovician "Cooksonia", a slender, ground-covering plant, became the first vascular plant to establish itself on land. This first colonisation occurred exclusively around the Equator on landmasses then limited to Laurasia and, in Gondwana, to Australia. In the Late Silurian two distinctive linages, zosterophylls and rhyniophytes, had colonised the tropics. The former evolved into the lycopods, that were to dominate the Gondwanan vegetation over a long period, whilst the latter evolved into horsetails and gymnosperms. Most of Gondwana was located far from the Equator during this period and remained a lifeless