The formation of "beak" also supports that birds are descendants of dinosaurs

In contemporary science, it is widely supported that birds are descendants of dinosaurs. The grounds are based on the analysis of the fossil of the excavated skeleton, but in an experiment conducted by an American research team using a fetus of a chick or the like, it goes back to the past growth process of the beakreverse engineeringI found out that a skeleton very similar to the dinosaurs is created and succeeded in supporting that birds are on the line of evolution of dinosaurs.

A molecular mechanism for the origin of a key evolutionary innovation, the bird beak and palate, revealed by an integrative approach to major transitions in vertebrate history - Bhullar - Evolution - Wiley Online Library
http://onlinelibrary.wiley.com/doi/10.1111/evo.12684/abstract;jsessionid=EC7B3E25B0B83620092756292A3019A1.f03t01

'Dino-chickens' reveal how the beak was born: Nature News & amp; Comment
http://www.nature.com/news/dino-chickens-reveal-how-the-beak-was-born-1.17507

This research was conducted by a research team by Dr. Bhart-Anjan Bhullar, a paleontologist at the University of Illinois at Chicago, USA. The paper is a scientific journal "Evolution" on the evolution of living organismsIt is posted(PDF file). The research team said that it was not intended to create "hybrid creatures" of chickens and dinosaurs, and to regenerate the dinosaur itself, with the objective "to spend 150 million years time on how the skeleton of the face is It is in knowing whether it has changed to a beak. "

It is considered difficult to find anatomical features that clearly distinguish between birds and dinosaurs, but birds change the skeleton that makes up the head in their evolution, and the physical features like present It is thought that you got it. Looking at the skeleton of the dinosaur, if it is a human face it will hit the part from the cheek to the noseAnterior mandibleBy extending the pair of left and right bones called the "forward"Snout(Snout) ", but as you evolve from there to the birds, the left and right bones protrude forward and join to one bone so that it gradually becomes a beak It is thought that it was supposed to have gotten.

Dr. Bhullar said about this, "Instead of having a skeleton that protrudes forward like a lot of vertebrates such as dinosaurs, birds have transformed the left and right bones forward and transformed them into one composition," We are talking about this, research team is a kind of chicken and ostrichEmuThe beak 's beak, and crocodiles and lizards, the anterior mandibular bone of the turtle, we analyzed growth in each fetal period. Prior to the experiment, the research team has hypothesized that "evapotransparents and dinosaur snouts evolved similarly from the anterior mandibular bone, but their evolution changed when they branched into birds."


For the formation of the skeleton of the face part, it is a type of proteinFGF(Fibroblast growth factor) andWnt signaling pathwayIt is known that a protein network called a large role is playing a role, but the research team has ascertained that these functions are different between birds and reptiles. In the reptilian fetus, the above-mentioned protein activity is active only in the two small areas that later form the face, whereas in birds' fetus the protein movement was activated more widely It was revealed. The research team considered this difference as important evidence that FGF and Wnt play an important role in the formation of bird's beak.

To prove this, the research team confirmed the change by injecting chemical substances that stop the protein's work to dozens of growing chicken fetuses. Although it seems that it was difficult to confirm the difference clearly from the appearance, comparing the actual skeleton, the state of the fetus which ordinary fetus and the protein stopped working is obviously different, and instead of the beak It turned out that a snout-like skeleton was formed.

The difference is as shown in the picture below. Compared to the normal skull written as "Control" of "a", in the "Experimental" produced by the experiment, the tip is divided into two as indicated by the "*" mark, the shape of the mouth is "Alligator" (Crocodile) and dinosaurs were confirmed to be similar to those of dinosaurs.


Also, by changing the state of skull change by computertomography(Fault image method), the skeleton shape inhabited about 140 million years agoArcheopteryxAnd about 80 million years agoVelkiraptorIt was found that it had characteristics that very closely resemble those of. In the following figures, the feature corresponds to the area shown in red, you can see that it is crossed by light blue birds and gray dinosaurs.


This research showed a part of the evolution from dinosaurs to birds from a skeleton perspective. According to Dr. Bhullar, "With this method we can reach a deep history of the past without a time machine," he said he plans to study the development of mammalian skulls and the process of development of the crocodile lower limbs from now on I am standing.