An exquisitely preserved dinosaur embryo was discovered inside a fossilized egg in China dating back 72 million years and is one of the most complete dinosaur embryos ever found. The amazing discovery helps prove that feather and flight evolution began in dinosaurs
Birds, descended from feathered theropod dinosaurs, are the only known living dinosaurs. The fascinating evolutionary mechanism of flight started in the Cretaceous period, an extinction event period that occurred 66 million years, which caused a sudden mass extinction of close to 75% of the earth’s floral and faunal species. Pertaining to this very subject, a fascinating new study has been published in iScience magazine, which has analyzed the so-called “Baby Yingliang” dinosaur embryo, a fossilized dinosaur egg, to further support the notion that bird evolution began with a certain kind of dinosaur.
“This dinosaur embryo inside its egg is one of the most beautiful fossils I have ever seen,” said paper co-author and vertebrate paleontologist Steve Brusatte of the University of Edinburgh. “This little prenatal dinosaur looks just like a baby bird curled in its egg, which is yet more evidence that many features characteristic of today’s birds first evolved in their dinosaur ancestors.”
Based on Baby Yingliang’s Dinosaur Embryo
Dated to between 72 and 66 million years ago (or mya), the dinosaur embryo dubbed “Baby Yingliang” was discovered in the late Cretaceous rocks of Ganzhou in southern China, reports Archaeology News Network . The species, known as oviraptorosaurs, are toothless, beaked, theropod dinosaurs. The dinosaur embryo was discovered in the year 2000 and housed in the Yingliang Stone Natural History Museum in Xiamen, Fujian, China. The current study was led by paleontologists from the University of Birmingham, UK, China’s University of Geosciences (Beijing), and other researchers from China, the UK, and Canada.
This find is one of the most complete dinosaur embryos ever found. The posture of the dinosaur in the embryo fossil prior to hatching matches that of birds. The scientists estimate the dinosaur would have been about 10.6 inches (27 centimeters) long at birth. The egg itself is 6.7 inches (17 centimeters) long. Bruscatte added that this egg is “more evidence that many features of today’s birds first evolved in their dinosaur ancestors.”
The Baby Yingliang dinosaur embryo used in the latest study to show that dinosaurs first developed feathers and then flight. Source: iScience
Pre-Hatching Behavior: Link Between Past and Present?
In the Baby Yingliang dinosaur embryo the head lies below the body, with the feet on either side, and the back curled along the blunt end of the egg. This phenomenon, witnessed in modern birds , is called tucking. This posture is seen critical to hatching, and thus controlled by the central nervous system . This has led scientists from the current study to suggest that this pre-hatching behavior may have originated first amongst non-avian theropods.
“It is interesting to see this dinosaur embryo and a chicken embryo pose in a similar way inside the egg, which possibly indicates similar prehatching behaviors,” said Fion Waisum Ma, joint first author and PhD researcher at the University of Birmingham. She further added that the Baby Yingliang dinosaur embryo would help us to better understand dinosaur growth and reproduction. Dinosaur fossils are the rarest fossils in the world, and generally incomplete. The Baby Yingliang dinosaur embryo defies both those norms.
A coelurosaur, a subgroup of therapods who produced the archaeopteryx (a genus of bird-like dinosaurs) and modern birds. (Greg Goebel / CC BY-SA 2.0 )
Previous Finds that Support This Hypothesis
It was in China itself that early “feather” finds in an intermediary species helped first posit this theory. In the 1990s, a bunch of fossils were discovered that lacked wings, and had a panoply of plumage, fuzzy bristles, and fully articulated quills! Up until this point, paleontologists believed that feathers were unique to birds, but clearly there was an earlier history of feather evolution that originated before birds, as per this report in the Scientific American .
Interestingly, Professor Brusatte was also a co-author on a recent study published in Current Biology in 2014, that analyzed fossils from coelurosaurs, a subgroup of therapods who produced the archaeopteryx (a genus of bird-like dinosaurs) and modern birds. This study focused on small skeletal changes to show that there was no great leap, but instead involved small, gradual evolutionary steps over time.
“A bird didn’t just evolve from a T. rex overnight, but rather the classic features of birds evolved one by one; first bipedal locomotion, then feathers, then a wishbone, then more complex feathers that look like quill-pen feathers, then wings,” Brusatte said. “The end result is a relatively seamless transition between dinosaurs and birds, so much so that you can’t just draw an easy line between these two groups.”
It is clear that there is so much we don’t know but if anything the picture is becoming clearer on how dinosaurs evolved to become feather birds. Co-author on the current study, Xing Lida, sums up the find. She argues that the current hypothesis needs to be tested further with more embryo fossil finds, which are hard to come by, but worth the sweat and patience.