Mesozoic the Innuitian orogeny, the Brooks Range, the Verkhoyansk and Cherskiy Ranges in Siberia, and the Khingan Mountains in Manchuria. This orogeny was related to the opening of the Arctic Ocean and subduction of the North China and Siberian cratons under the Pacific Ocean. In contrast, the era featured the dramatic rifting of the supercontinent Pangaea, which gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast) today. By the end of the era, the continents had rifted into
Unenlagiinae Unenlagiinae Unenlagiinae is a subfamily of dromaeosaurid theropods. Unenlagiines are known from South America and Antarctica. Most unenlagiines have been discovered in Argentina. The largest was "Austroraptor", which measured up to 5–6 m (16.4–19.7 ft) in length, making it also one of the largest dromaeosaurids. The subfamily is distinguished from other dromaeosaurids by a tail stiffened by lengthy chevrons and superior processes, sharp articulate claws, and a posteriorly oriented pubis. Their distinct anatomy from Laurasian dromaeosaurids was likely a consequence of the breakup of Pangaea into Gondwana and Laurasia, where the geological isolation of unenlagiines from their relatives resulted in