Sea Level Changes Caused Earth's Oldest Sea Turtles to Become Extinct

Changes in sea level reportedly caused Earth's oldest sea turtles to become extinct, providing insight into what could possibly happen to modern-day turtles battling climate change-related sea level rise.

Little is known about the earliest sea turtle species that inhabited Earth millions of years ago. Although, in 2009 scientists discovered the remains of Hispaniachelys prebetica - supposedly the oldest sea turtle in southern Europe - in the Baetic Cordillera, in Jaén.

They thought they had a new species of turtle on their hands they could tell them more about its ancient environment. However, until this latest study it was still not clear what group the primitive turtle belonged to. After reinterpreting some of its features and gathering new information on its morphology, researchers found something they did not expect.

"Hispaniachelys prebetica cannot be recognized as a valid species. Nevertheless, it is identified as a member of a group of turtles exclusive to the European Jurassic called Plesiochelyidae, which were very diverse," researcher Adán Pérez-García said in a statement.

Around 160 million years ago, primitive Plesiochelyids roamed the waters of countries such as the United Kingdom, France, Switzerland, Germany, Portugal and Spain. Now, with the identification of the specimen in Jaén, the research team is gaining a better understanding of this group.

Specifically, they inhabited warm, shallow seas of Europe, but "they were not as agile in this environment as today's sea turtles, who are able to cover very large distances and cross seas and even oceans," explained Pérez-García. "Due to their anatomy, these Jurassic turtles were restricted to coastlines."

Unfortunately, their dependency on ocean coastlines led to their downfall. Changes in the sea level which occurred at the end of the Jurassic period - around 145 million years ago - had a drastic impact upon the environments they lived in. As a result, "these turtles, in addition to other groups of sea reptiles, became extinct at that time," Pérez-García concluded.

And with global sea level rise picking up speed today, researchers are becoming increasingly worried for many modern-day sea turtle species - especially the loggerhead and Kemp's ridley, which are endangered.

The study results are described in the journal Acta Palaeontologica Polonica.

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