Cambrian Explosion: e xtends into the Ordovician (Introduction)

by David Turell , Tuesday, October 10, 2023, 19:54 (200 days ago) @ David Turell

New forms appear:

https://www.newscientist.com/article/2396825-ocean-life-surged-500-million-years-ago-du...

"A period of global cooling around 500 million years ago may have triggered Earth’s largest surge in marine biodiversity.

"The Great Ordovician Biodiversification Event marked a dramatic explosion in marine biodiversity between approximately 490 and 440 million years ago, resulting in the emergence of several new orders, families and genera of life that we still see today, such as sea stars and sea urchins.

“'[It] is one of the key diversifications of life in Earth history, often referred to as ‘diversity’s big bang’,” says David Harper at Durham University, UK, who wasn’t involved in the study.

"Proposed ideas for what sparked the event include sea level rises induced by continental drift, an increase in atmospheric oxygen and even meteors.

"Another possible explanation is the global cooling that occurred during the period, which earlier studies found reduced tropical sea surface temperatures from around 40°C to 30°C (104°F to 86°F). Now, Daniel Ontiveros at the University of Lille in France and his colleagues have found that this was probably the case.

"The team combined a climate model, based on fossil data and our knowledge of land configuration at the time, with an ecological model that mapped biodiversity patterns in the oceans.

"The combined model suggests that, as the oceans cooled, they became more conducive to life, leading to the rapid emergence of new species. Existing species also moved from waters around the north and south poles towards the equator.

“'At the start of the Ordovician, the ocean was very warm,” says Ontiveros. “Only a few species could withstand the high temperatures.” That is why aquatic life was mostly constrained to the colder, higher latitudes at the beginning of the Ordovician, he says. As the climate cooled, tropical waters became more habitable."

Comment: more forms with no precursors. This period exactly follows the Cambrian.