A research group including Tokyo City University has announced that the oldest sea turtle fossil in East Asia, including Japan, has been found in a geological stratum that is approximately 100 million years old on a remote island in Kagoshima Prefecture, and the sea turtle family is expanding its distribution around the world. This is an important discovery in exploring the process by which this process occurs.
The sea turtle fossils found include part of the neck bone, which is about 2.5 centimeters long, and part of the shell bone, which is about 4 centimeters wide.
A research group led by Associate Professor Yasutoshi Nakajima of Tokyo City University discovered it four years ago in the Cretaceous strata dating back approximately 100 million years on Shishijima in Nagashima Town, Kagoshima Prefecture.
When examined using CT scans and other methods, the shell fossil matched the characteristics of a sea turtle, as the joint surfaces between the bones were loose and flexible, and it was estimated that it was a large individual with a shell length of over 70 cm. is.
According to the research group, the oldest sea turtle fossil was found in South America, dating back 135 million years, but it is rare to find sea turtle fossils dating back 100 million years, during the late Cretaceous period, from the North Pacific Ocean. It is said to be the oldest not only in Japan but also in East Asia.
For this reason, the discovery is important for exploring the process by which sea turtles spread across the world's oceans.
Associate Professor Nakajima said, ``We believe that the fossils found this time are fragmentary and it is not possible to identify the type from these alone, so we would like to continue the field survey to see if there are any remaining bones or fossilized bones of other individuals.'' .
Fossil discoverer: ``I'm moved by what I've found and want to continue excavating.''
The person who discovered the oldest fossil of a sea turtle in East Asia was Satoshi Utsunomiya, a company employee living in Osaka.
He is known as an ``salaryman fossil hunter,'' and has discovered many fossils of paleontology, including the fossils of spinosaurs and the Kubinagaryu, which he named ``Satsumatsunomiyaryu.''
Regarding this fossil, they are proposing the name ``Satsumamuka sea turtle'' after Kagoshima Prefecture, where it was discovered, and Mr. Utsunomiya said, ``When you break the block of stone with a hammer, you can see the cross section of the bone inside. , I realized that it was a big discovery. Sea turtles are a group that survived the Great Cretaceous Extinction and are still alive today, so I was thrilled to find the oldest fossil that is close to their origin. In Kagoshima Prefecture. I have a feeling that there are still many amazing things that will come out of Shishijima, so I want to continue excavating."