The earliest examples of dinosaurs evolving into birds were found in China. The fossils that have been found are smashed flat because of the layers of debris that have been deposited over time. No one has been able to look at his head. A new study shows how a skull can be reconstructed to reveal more about a person's vision and sense of smell.
One of the authors of a book about the evolution of birds says that jeholornis is his favorite of all the birds. It's the first time we're getting at what the bird's skull looked like, and it's exciting.
The study's first author, Han Hu, went through 100 fossils at a museum in China and chose the one with the best-preserved skull. Due to the costs of high quality scanning and the fact that we won't know if one skull will give us the information we want before the scanning, we couldn't choose the best skull. Hu, a researcher at the Department of Earth Sciences, University of Oxford, UK, chose this one because it is relatively complete, and also because it is important that the skull is isolated from other parts of the body.
Since we won't chop the skull off from the skeleton if they are articulated, an isolated skull will reduce the size of the scanning area, which will increase the scanning quality. After the digital reconstruction, the specimen we chose here was almost a perfect one.
The bones were like the bottom of a bag of potato chips. We were able to take a bunch of X-rays and stack them together to create a 3D image, and then reconstruct the skull from all the bones.
Matteo Fabbri said that they were able to see different features of the skull that hadn't been seen before.
Soft tissues are rarely preserved, but bird and dinosaur brains are. Knowing the shape and dimensions of a fossil bird's skull tells us a lot about its brain. If you look at the brains of a frog, a human, or a fossil bird, you'll see that they all have the same brain structure.
Thanks to the long-standing placement of these structures, the researchers were able to determine how the brains of birds and dinosaurs compare.
In between what we see in non-avian dinosaurs and what we see in modern birds is the brain of jeholornis. If you look at the skulls of dinosaurs, you'll see that they have large olfactory bulbs and a reduced midbrain. They probably had a good sense of smell and not great sight. On the other hand, if you look at birds from the past, they do the same thing. They have a large olfactory bulb and a large brain. The man fell in the middle.
The Jeholornis had bigger olfactory bulbs than most modern birds, meaning that it relied more on smell than it has in the past. A recent study shows that the earliest known fruit-eating animal is Jeholornis. Fruits release a lot of chemicals when they are ripe. Having a better sense of smell might have aided in finding fruit.
The researchers found that the brain was adapted to smell better in the daytime. Birds have bones that tell them how much light goes into their eyes. owls have wider scleral ring openings relative to their eye sockets to let in more light while birds have narrower openings for light to go through. The scleral rings suggest that it was most active during the day.
The skull features give a better understanding of the lifestyle of this early bird. It's becoming more and more clear that the evolution of birds was more complicated than we thought. It is different from other early birds as well. It isn't a simple evolutionary story.
One of my favorites is the Jeholornis. It's position as one of the most primitive birds during the dinosaur-bird transition determines that completing its story will reveal the true scenery of that critical evolutionary period, and also, tell us why and how the modern birds evolved to be what we see now.
More information: Han Hu et al, Cranial osteology and palaeobiology of the Early Cretaceous bird Jeholornis prima (Aves: Jeholornithiformes), Zoological Journal of the Linnean Society (2022). DOI: 10.1093/zoolinnean/zlac089 Journal information: Zoological Journal of the Linnean Society
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