Wikipedia
Olenekian
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch or a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian follows the Induan and is followed by the Anisian.
The Olenekian saw the deposition of a large part of the Buntsandstein in Europe. Archosaurs - a group encompassing crocodiles, pterosaurs, dinosaurs, and ultimately birds - are diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian.
The Olenekian is roughly coeval with the regional Yongningzhenian stage used in China.