The dinosaur-bird transition is among the most fascinating events in evolutionary history, but several aspects such as changes in reproductive system, nesting strategy, and body temperature are still poorly understood. New research led by Goethe University Frankfurt scientists shows that eggshells of modern reptiles and birds differ in their isotopic compositions. Interestingly, analyses of eggshells of Troodon formosus — a small, bird-like dinosaur that lived in North America during the Late Cretaceous epoch, some 77 million years ago — reveal that it retained a slower, reptile-like mineralization to produce its eggs, despite having already evolved the capacity of changing its body temperature (heterothermic endothermy) like modern birds. The findings also suggest that Troodon formosus possessed two functional ovaries and that their nests were shared by multiple females.
“Troodon formosus was about 2 m (6.6 feet) long and populated the vast semi-arid landscapes of North America about 75 million years ago,” said lead author Dr. Mattia Tagliavento from Goethe University Frankfurt and colleagues.
“Like some of its dinosaur relatives, it presented some bird-like features like hollow and light bones.”
“Troodon formosus walked on two legs and had fully developed feathery wings, but its relatively large size precluded it from flying. Instead, it probably ran quite fast and caught its prey using its strong claws.”
“The females laid eggs more similar to the asymmetric eggs of modern birds than to round ones of reptiles, the oldest relatives of all dinosaurs.”
“These eggs were colored and have been found half buried into the ground, probably allowing the females to sit and brood them.”
In their study, the authors examined the calcium carbonate of several well-preserved Troodon formosus eggshells.
Using a novel method called dual clumped isotope thermometry, they could measure the extent to which heavier varieties (isotopes) of oxygen and…
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