Silurian era

You may be looking for Age of the Silurians, also called the "Silurian Age".

The Silurian, also known as the Silurian Age, (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"]) was an era (TV: Doctor Who and the Silurians ^[+]Loading...["Doctor Who and the Silurians (TV story)"]) or period of Earth history spanning 443,000,000 to 416,000,000 (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"]) or 430,000,000 to 395,000,000 BC. (PROSE: The Universal Databank ^[+]Loading...["The Universal Databank (reference book)"]) The Silurian era saw the first bony fish evolve, and plants and insects began to live on land. (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"])

Following the Ordovician period, which was separated from it by the Ordovician-Silurian extinction event, the Silurian Age was a period of comparative stability; the first true plants migrated onto land, as did the first insects. In the oceans, the first bony fish evolved, to be preyed on by primitive squid and huge sea scorpions. There was a single large continent in the south, which was mostly desert. The atmosphere had only 70% as much oxygen as the 21st century and had a much higher carbon dioxide content; a human could breathe in the Silurian, albeit with discomfort. (PROSE: Prehistory Repeating Itself ^[+]Loading...["Prehistory Repeating Itself (feature)"])

After reading Dr Quinn's notes, the Third Doctor believed it was the era in which the Silurian race originated. He also noted that the Silurians had existed prior to the Great Continental Drift of 200,000,000 BC. (TV: Doctor Who and the Silurians ^[+]Loading...["Doctor Who and the Silurians (TV story)"]) The Third Doctor later believed Dr Quinn got the period wrong, saying they should be from the Eocene era. (TV: The Sea Devils ^[+]Loading...["The Sea Devils (TV story)"], PROSE: The Eight Doctors ^[+]Loading...["The Eight Doctors (novel)"])

Behind the scenes

Doctor Who and the Silurians made the error of suggesting that the reptilian Silurians were from the Silurian era. The earliest reptiles evolved in the late Carboniferous, over 100 million years after the Silurian. The correction in The Sea Devils was insufficient, as the Eocene is millions of years before the earliest ape-like humans. The dating issue of the Silurians has persisted throughout Doctor Who media.