Finding fossilized prehistoric turtle fossils and eggs in South Alberta

Scientists at the University of Calgary and the Tyrrell Royal Paleontological Museum have recently discovered a 75-million-year-old fossil of a pregnant sea turtle along with fossilized eggs in the barren land on the side. southeast Alberta. Fossils are provoking ideas about the evolution of reproduction and egg laying in tortoises and sea turtles.

This is the first time a pregnant sea turtle fossil has been discovered. The discovery was published on August 27 in Biology Letters.

The Tyrrell team found that the mother turtle fossil carrying eggs in 1999 and the egg nest was discovered in 2005 by Darla Zelenitsky of the University of Calgary and the lead author of the study and an expert of the site. fossil. Both fossils are found in the Manyberries area located 85 kilometers south of Medicine Hat.

Darla Zelenitsky, who also participated in the discovery of the fossil-bearing dinosaur fossil, said: 'Although it is difficult to find fossil eggs and young offspring of extinct animals, finding them they are more difficult in the body of the mother. '

The fact that scientists realized fossilized mother turtle carrying eggs happened very casually. François Therrien - co-investigator of the research and management of dinosaur paleontology at the Tyrrell Museum - said: 'Fossil turtles have been partially broken when we first discovered it. . The random rupture revealed the fossil as a mother turtle '.

Darla Zelenitsky said: 'Although it is difficult to find fossil eggs and young offspring of extinct animals, it is more difficult to find them in the mother's body.' (Photo: Ken Bendiktsen)

The rest of at least 5 pinched eggs can be observed inside the fossilized mother turtle's body. CT scans reveal more eggs hidden beneath the crust. The estimated turtle is about 40 cm long, probably laying about 20 eggs. The fossilized egg nest is found in another mother turtle with 26 eggs approximately 4 cm in diameter.

Both fossil specimens are of extinct tortoise named Adocus, which is a large river turtle that lived at the same time as dinosaurs and is quite similar to white-spotted sea turtles on the face today.

Adocus's eggs are extremely thick and hard, while most modern turtle eggs are thinner and softer. Thick eggshell may have evolved to protect the eggs from drying out in a dry environment or to protect them from predation by predators in the dinosaur era.

Zelenitsky argues that the pregnant turtle fossil and fossilized eggs have shed light on the evolution of reproductive traits in modern turtles, especially those related to eggs and egg nest. Therrien said: 'Based on the fossils discovered, we have determined that the ancestors of the neck-billed turtles are in existence today, mostly sea turtles and tortoises, laying many eggs and shells. hard'.

The pregnant turtle fossil will be on display at the Royal Tyrrell Museum at Drumheller from August 29.