Modern birds have many similarities to dinosaurs, from their feathers and feet to hollow bones and laying eggs. Recently, paleontologists found another feature dinosaurs shared that is their unique way of hatching, called tucking.
Paleontologists also recently discovered a 66-million-year-old fossil egg that shows how similar a theropod dinosaur embryo and a modern bird embryo would appear before hatching, in a curled position. The main difference between both eggs is that the dinosaurs did not have wings, they had little arms and claws.
Oviraptorosaurs walked the Earth about 126 million years ago and had many similarities to modern birds. The Oviraptorosaurs had hollow bones, three-toed limbs, beaks and feathers on their arms, but they could not fly. They used their feathers to warm up their eggs.
Paleontologists have only found half a dozen embryonic dinosaur fossils, as they are very rare. Fion Waisum Ma, a paleontologist at the University of Birmingham in the United Kingdom said that, “Some embryos are quite well preserved but they don’t show this posture,” and “some are very fragmentary so it is difficult to see their posture clearly.” This fossil egg is even more rare because it shows “tucking.”
The tucking position has only been seen in birds; they get into this position a couple days before they hatch. If they are not able to get into the tucking position, they are not able to properly hatch. Tucking helps break the bird out of its shell by cracking the eggshell first. It restricts the movement of the head, allowing the head to poke the same spot and making it easier to break the eggshell. Other dinosaur embryos have shown “egg teeth,” which scientists believe were used to break out of their shells.
This embryonic similarity helps us understand the evolution of modern birds and their ancestors.
[Source: NBC News; USA Today; National Geographic; Britannica]