The debate about how dinosuars evolved and when they migrated across the super-continent Panagea reached its conclusion with the discovery of the 213 million-years-old fossil of Tawa hallae in USA's New Mexico:

Dinosaurs originated and evolved under three lineages: the herbivorous saurpods, ornithiscians and the carnivorous theropods.

In the 1960s, a fossil named Herrerasaurus was discovered alongside the fossils of a sauropod and an ornithiscian in South America.

Herrerasaurus was a carnivore with theropod features but some of its attributes were atypical of a theropod thus sparking a debate on its origin.

Tawa is the missing link with all the theropod and Herrerasaurus features making the Herrerasaurus a definite theropod.

Tawa's discovery proves that dinosaurs originated and rapidly evolved into the three main lineages in South America about 230 million years ago.

Later when they migrated to North America, only the carnivores survived its climate and went on to spawn birds.


Down To Earth, January 2010