Olenekian
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The Olenekian (also known as the Yongningzhenian) is a stage of the Early Triassic epoch. It spans the time between 249.7 ± 0.7 Ma and 245 ± 0.7 Ma (million years ago). It is defined as starting near the lowest occurrence of Hedenstroemia or Meekoceras gracilitatis ammonites, and of the conodont Neospathodus waageni. It is defined as ending near the lowest occurrences of genera Japonites, Paradanubites, and Paracrochordiceras; and of the conodont Chiosella timorensis. Archosaurs are a group of diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian. It is named for Olenëk in Siberia.
[edit] Olenekian fauna
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| Triassic period | ||
|---|---|---|
| Lower/Early Triassic | Middle Triassic | Upper/Late Triassic |
| Induan | Olenekian | Anisian | Ladinian | Carnian | Norian Rhaetian |
