Recently Discovered Turtle Fossil Challenges Theories On Origins

Scientists have discovered the fossilized remains of a turtle in southwestern China. The fossil is said to fill an evolutionary hole in how the reptiles developed features like a beak and the shell. The specimen discovered could help scientists determine when modern turtles developed those characteristics, but it has cast mystery on the origin of the group.

The fossil is a roughly 2-meter-long specimen that has been called "Eorhynchochelys sinensis" and it lived about 230 million years ago. The skull is like what we see in modern turtles, but the remainder of the animal's skeleton is similar to a turtle predecessor that lived 10 million years earlier.

The new species is said to fit the evolutionary image scientists have had for years with near perfection. Turtles have changed little in the past 210 million years with a top shell, bottom shell, and a sharp beak with no teeth. Turtles lack a common reptile feature, two holes behind their eyes in the skull where jaw muscles attack. With those holes missing scientists have struggled to fit turtles into the reptile family tree.

The new fossil fills a gap between a specimen discovered in 2008 and one discovered in 2015 that were separated by a span of about 20 million years. Studies over the last two decades have suggested that the closest evolutionary relatives to the turtle are crocodilians, dinosaurs, and modern birds. Other studies have suggested that lizards and snakes are the closest evolutionary relatives to turtles.

Researchers placing the new specimen's characteristics into the analysis with those older fossils have determined that turtles aren't as closely related to those other groups as past research suggested. They are an offshoot of earlier ancestors. Scientists do say that for now, they lack the information about early reptiles to know where turtles fall.

SOURCE: Nature