Gondwana Massif have been dated at 320–330 million years old, indicating that the subduction process initiated in the early Carboniferous.This was relatively short lived (lasting about 20 million years), and initial contact of the two landmasses occurred in the mid-Carboniferous, with broader collision during the early Permian. In the Devonian an island arc named Chaitenia accreted to Patagonia in what is now south-central Chile. Gondwana and Laurasia formed the Pangaea supercontinent during the Carboniferous. Pangaea began to break up in the Mid-Jurassic when the Central Atlantic opened. In the western end of Pangaea, the collision between Gondwana and Laurasia closed the
Unenlagiinae allopatric speciation. 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