Paleontologists have found a clutch of fossilized turtle eggs in the Lower Cretaceous Hasandong Formation in South Korea.
“Ever since the first recognition of dinosaur eggs from Mongolia, East Asia has produced an enormous record of fossil eggs,” said Dr. Seung Choi from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences and colleagues.
“However, fossil eggs from clades other than non-avialan dinosaurs are rare.”
“Turtle eggs are no exception and there are only a few reliable reports from East Asia, including Cretaceous eggs from Mongolia, China, and Japan.”
“There is still a large knowledge gap in the fossil record of East Asian turtle eggs and new findings could shed light on the reproductive history of turtles.”
The newly-discovered turtle egg clutch dates back 110 million years (Early Cretaceous period).
It contains at least 20 spherical to ellipsoidal eggs, around 17-21 mm in diameter; shell thickness is 0.27-0.31 mm.
The eggs belong to the oospecies Testudoolithus aff. curiosa with the smallest recorded egg size within its genus.
The specimens were recovered from a rock fragment of the Uppermost Hasandong Formation in the northwest outskirts of Jinju City, South Gyeongsang Province, South Korea.
“The Hasandong Formation is the lowest egg-fossil-bearing formation in the Korean Peninsula,” the paleontologists said.
“Thus, the find represents the oldest Korean fossil eggs along with theropod eggs.”
The researchers also detached two eggs from the clutch and cut them to expose radial sections of the eggshells.
The two exposed sections were used for polarized light microscopy (PLM) observation, EBSD, and Raman spectroscopy analysis.
During the detachment, seven eggshell fragments were obtained, and they were used for scanning electron microscopy (SEM) observations.
“Unlike all other amniotic eggs, which are composed of calcite, originally aragonitic turtle eggs provide an opportunity…
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