Wednesday, August 27, 2008

About 75 Million Years after Death Fossilized Pregnant Turtle Discovered

A turtle that toddled alongside the dinosaurs died just days sooner than laying a clutch of eggs. At present, about 75 million years later, paleontologists are publicizing their find of the fossilized mother-to-be and the eggs tucked within her body.

Scientists from the Royal Tyrrell Museum of Palaeontology in Canada revealed the turtle in 1999 in a mud-filled channel in the badlands of southeastern Alberta. After that, in 2005, University of Calgary scientists found a nest of 26 eggs laid by another female of the similar species in the same region.

The scientists say that both specimens, explained this week in the periodical Biology Letters, belong to an extinct turtle in the Adocus genus, a big river turtle that resembles today's slider and cooter turtles. The pregnant turtle signifies the first fossil turtle to be discovered with eggs still inside the body cavity.

Researcher Darla Zelenitsky, a geoscientist at the University of Calgary in Alberta, who was also involved in the first discovery of a dinosaur with eggs inside its body, said that "Although it is quite rare to hit upon the eggs and babies of extinct animals, it is even rarer to come across them within the body of the mother".

Fertile find

It was nearly by accident that scientists recognized that the fossil turtle had been pregnant. "The real reason we knew she was pregnant was since when the fossil was found the body was broken down," Zelenitsky told LiveScience, "therefore there was egg shell on the ground immediately below the fossil, it was falling out of the body".

The team spotted at least five crushed eggs inside the body of the fossilized female, and computed tomography (CT) scans discovered more eggs concealed beneath the turtle's shell. The turtle, expected to be about 16 inches (40 cm) long, could have produced about 20 eggs. When still intact, the eggs would have been sphere-shaped and about 1.5 inches (4 cm) in diameter. The eggs from the close by nest were about the same size and form. Both sets of eggs as well had very thick and hard shells, particularly relative to most modern turtles whose shells are moreover thinner or soft.


The thick eggshell can have evolved to look after the eggs from drying out or from greedy predators that lived during the Age of Dinosaurs. The pregnant turtle and nest specimens, the researchers say, shed light on the growth of reproductive traits of current turtles. François Therrien, the Museum's Curator of Dinosaur Palaeoecology, who worked on the turtle report in the journal said that "Based on these fossils, we have firm that the ancestor of living hidden-necked turtles, which are nearly all of today's turtles and tortoises, laid a big number of eggs and had hard, rigid shells".


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