Egg Study Points Evolution of Dinosaurs to Birds With Brooding
Which came first—the brooding dinosaur or chicken?
Researchers at the University of Calgary and Montana State University have discovered that a North American dinosaur called Troodon incubated its eggs similarly to brooding birds. The egg study may point to an evolutionary link between the two and likely eliminates a previous theory that dinosaurs covered their eggs in nest materials like crocodiles. Researchers believe the dino's eggs would have been partially buried in mud on the bottom, but the tops would have been left exposed.
"Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do," said study co-author Darla Zelenitsky.
"Both the eggs and the surrounding sediments indicate only partial burial," Zelenitsky said. "Thus an adult would have directly contacted the exposed parts of the eggs during incubation."
Paleontologists have unearthed fossils of the small, meat-eating dinosaur from Texas to Alaska and discovered that it lived around the Late Cretaceous period. Troodon had one of the largest brains per body mass and large, pointed eyes utilized for hunting.
While Troodon's style isn't similar to most birds, it does bear resemblance to one species—the Egyptian Plover.
"There are similarities with a peculiar nester among birds called the Egyptian Plover that broods its eggs while they're partially buried in sandy substrate of the nest," researcher David Varricchio said.
The first comparisons between birds and dinosaurs occurred in 1969 when J.H. Ostrom described Deinonychus antirrhopus and its similarities to Archaeopteryx. Since then, scientists have been searching for proof that these comparisons hold real value.
"For now, this particular study helps substantiate some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds," Zelenitsky said. "It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs."
The study was published in the journal Paleobiology.