Just before the hatchlings are born, their hip bones are exactly the size of a dinosaur’s pelvis.

Just before the hatchlings are born, their hip bones are exactly the size of a dinosaur's pelvis.
The quail hindquarters of the embryo with green bones, the veins are blue in color and the muscles are red in color. The pelvis of this quail fetus has just changed to a relatively “modern” bird configuration. Credits: Christopher T. Griffin and Bharat-Anjan S. Bhullar.

Have you ever wondered what dinosaurs really looked like? If so, let go of your reptile-centric, Spielberg-perverted preconceptions for a second and look out the window for signs of chirping.

Birds aren’t just descendants of dinosaurs – they’re dinosaurs. or a type of dinosaur to be more precise, belonging to the same theropod group of dinosaurs that includes t rex, Theropods are all bipedal and some of them share more bird-like characteristics than others. 150 million years old archeopteryx — a hybrid creature discovered in 1861 with feathered wings but with teeth and the long bony tail of a dinosaur — long was the only truly bird-like dinosaur we knew. Later, scientists found that velociraptorWhich dates from the Late Cretaceous (100–66 million years ago), had bird-like feathers covering its body and other features that made it closely related to modern birds.

The fact that birds and dinosaurs are evolutionarily intertwined is reinforced by a fascinating new study in which researchers at Yale University show how developing baby birds have — just moments before hatching — hips. The bones of which are like a small replica of a dinosaur’s pelvis.

“Every single bird, in its early life, possessed this dinosaurian form,” said Bharat-Anjan S Bhullar, assistant professor of earth and planetary sciences at Yale and senior and corresponding author of the new study. “Then, at the last minute, it seems to remember it’s a bird and needs a bird’s pelvis.”

Bhullar and his team are experts in using computer tomographic (CT) scanning and microscopy to create 3D images of embryos from various animals. Previously, they had visually documented dinosaur inner ears, bird beaks, mammalian rolling jaws, and the evolution of vision in vertebrates. These types of investigations can be extremely valuable because they can reveal important evolutionary transitions among non-avian dinosaurs, reptiles and birds.

This time, Bhullar and his colleagues applied the same technique to study the pelvic development of alligators, domestic chickens, Japanese quail, Chilean tinamou and parakeets. They then compared the stages of embryonic development with those of dinosaurs, including feathered species. archeopteryx,

By tagging the fetal hip bones with antibodies, and then using confocal microscopes and CT scanning, researchers can create fascinating images of translucent-looking fetuses that clearly show the bones, muscles and nerves of the developing hip. in all three dimensions.

Just before the hatchlings are born, their hip bones are exactly the size of a dinosaur's pelvis.
parakeet Velociraptor. Credits: Christopher T. Griffin, Daniel Smith-Paredes, and Bharat-Anjan S. Bhullar.

In this way they learned that during a brief phase of its evolution, the bird pelvis is almost a one-to-one replica of a dinosaur’s pelvis, an example of what scientists call a “terminal joint”—when ancestral features appeared in the evolution of a beast. For example, embryonic parrots have pelvis that closely resemble those of Velociraptor.

“It was unexpected to see these early stages of bird evolution look like the hips of an early dinosaur,” Christopher Griffin, a postdoctoral associate in Bhullar’s lab and lead author of the new study, said in a statement. “Over the course of just two days, the developing embryos change in a way that reflects how they changed in development, transitioning from looking like an early dinosaur to looking like a modern bird.”

Dinosaurs don’t swim or fly, not even the famous bird-like archeopteryx, Pterosaurs do not count because they were reptiles. However, in many birds, the design of the hip bone is critical to their ability to maintain powered flight, so these latest observations may help scientists unravel the mystery of how flight evolved among birds.

“The bird’s body has been incredibly modified in almost every way to create an optimized flying machine,” Bhullar explained. “Its physical structure is tightly constrained by the requirements of aeronautical design.”

The findings appeared in the journal Nature.


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