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). The Olenekian is divided into the Smithian and the Spathian age. 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 -- a group encompassing crocodiles, pterosaurs, dinosaurs, and ultimately birds -- are diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian.

The stage is named for Olenëk in Siberia.

Contents 1 Vertebrate Fauna 1.1 Archosauromorphs (non-archosaurian) 1.2 Therapsids (non-mammalian) 2 See also 3 References

[edit] Vertebrate Fauna

• Gnathorhizids

• Archosaurs
• Erythrosuchids
• Proterosuchids
• Crurotarsi
  • Rauisuchia

[edit] Archosauromorphs (non-archosaurian)

†Non-archosaurian Archosauromorphs of the Olenkian
Taxa	Presence	Location	Description	Images
Chasmatosuchus

[edit] Therapsids (non-mammalian)

†Non-mammalian Therapsids of the Olenkian
Taxa	Presence	Location	Description	Images
Kannemeyeria				Kannemeyeria.

[edit] See also

• Geologic time scale

[edit] References

• GeoWhen Database - Olenekian

Triassic period
Lower/Early Triassic	Middle Triassic	Upper/Late Triassic
Induan | Olenekian	Anisian | Ladinian	Carnian | Norian Rhaetian