Deep in the deep sea, researchers found fragments of a sea urchin’s spine 104 million years ago.

The deep sea is a strange place, the likely origin of the first simple life forms on Earth. Knowing how the number of species living on the sea floor has changed is hugely important, as some scientists believe deep-sea ecosystems have resurfaced after catastrophic oceanic disturbances and mass extinctions. All of this means that life on the sea floor would be very young compared to Earth’s history.

Despite this, there is more and more evidence that parts of the sea are much older than previously thought. In fact, a research team has now discovered the first fossil evidence of higher invertebrates colonizing the deep sea floor. What’s astonishing is that this evidence dates back to the Cretaceous period, at least 104 million years ago, which means that sea urchins (also known as irregular sea urchins) have been inhabiting the deep sea continuously since this time period.

Fossilized sea urchin spines have been found in more than 1,400 sediment samples from boreholes in the Pacific, Southern, and Atlantic Oceans, at depths between 200 and 4,700 meters (656 and 15,420 ft). 40,000 pieces of thistles were found, identified by their structure and shape.

set of spine

Image credit: PLUS ONE, 2023 Viez et al.

The researchers investigated the morphological characteristics of the spines of the samples and compared them to each other. There seemed to be a dramatic change at the end of the Cretaceous period 66 million years ago, when a devastating meteorite slammed into the Earth and caused a mass extinction of the dinosaurs and unrest in the deep sea.

The spines after impact were thinner and less varied in shape. This is known as the “Liliput effect”, when prehistoric organisms that survive a mass extinction event are often younger than those that lived before the event. This occurs because smaller species often have a higher survival advantage after the event, possibly due to a lack of food on the deep sea floor.

“We interpret changes in spines as an indication of continued evolution and emergence of new species in the deep sea,” explained lead author Dr. Frank Fessey, from the Department of Geobiology at the University of Göttingen, in a statement. .

He confirms another discovery: “About 70 million years ago, the biomass of sea urchins increased. We know that the water cooled at the same time. This relationship between deep sea biomass and water temperature allows us to speculate on how the deep sea cooled.” It will change due to human-caused global warming.”

This type of research is very important because it gives more knowledge about the mysterious depths of the sea.

This study was published in the journal PLOS ONE.

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