Tweaking the beak: Retracing the bird's beak to its dinosaur origins, in the laboratory

May 12, 2015
Artist's rendition of the nonavian dinosaur Anchiornis and a modern tinamou with premaxillary and palatine bones highlighted. Credit: John Conway

Scientists have successfully replicated the molecular processes that led from dinosaur snouts to the first bird beaks.

Using the fossil record as a guide, a research team led by Yale paleontologist and developmental biologist Bhart-Anjan S. Bhullar and Harvard developmental biologist Arhat Abzhanov conducted the first successful reversion of a bird's skull features. The scientists replicated ancestral molecular development to transform chicken embryos in a laboratory into specimens with a snout and palate configuration similar to that of small dinosaurs such as Velociraptor and Archaeopteryx.

Just don't call them dino-chickens.

"Our goal here was to understand the molecular underpinnings of an important evolutionary transition, not to create a 'dino-chicken' simply for the sake of it," said Bhullar, lead author of the study, published online May 12 in the journal Evolution.

Finding the mechanism to recreate elements of dinosaur physiology has been a topic of popular interest for some time. It has been featured in everything from molecular biologist Jack Horner's 2009 book, "How to Build a Dinosaur," to the upcoming Hollywood movie "Jurassic World."

In this case, the fascination derives from the importance of the beak to avian anatomy. "The beak is a crucial part of the avian feeding apparatus, and is the component of the avian skeleton that has perhaps diversified most extensively and most radically—consider flamingos, parrots, hawks, pelicans, and hummingbirds, among others," Bhullar explained. "Yet little work has been done on what exactly a beak is, anatomically, and how it got that way either evolutionarily or developmentally."

Tweaking the beak: Retracing the bird's beak to its dinosaur origins, in the laboratory
Experimental restoration of predicted ancestral expression, with skulls from a chicken (left), experimental animal (middle), and alligator (right). Credit: Bhart-Anjan S. Bhullar

In the new study, Bhullar and his colleagues detail a novel approach to finding the involved in creating the skeleton of the beak. First, they did a quantitative analysis of the anatomy of related fossils and extant animals to generate a hypothesis about the transition; next, they searched for possible shifts in that correlated with the transition.

The team looked at gene expression in the embryos of emus, alligators, lizards, and turtles. The researchers discovered that both major living lineages of birds (the common neognaths and the rarer paleognaths) differ from the major lineages of non-bird reptiles (crocodiles, turtles, and lizards) and from mammals in having a unique, median gene expression zone of two different facial development genes early in embryonic development. This median gene expression had previously only been observed in chickens.

Using small-molecule inhibitors to eliminate the activity of the proteins produced by the bird-specific, median signaling zone in chicken embryos, the researchers were able to induce the ancestral molecular activity and the ancestral anatomy. Not only did the beak structure revert, but the process also caused the palatine bone on the roof of the mouth to go back to its ancestral state. "This was unexpected and demonstrates the way in which a single, simple developmental mechanism can have wide-ranging and unexpected effects," Bhullar said.

The work took Bhullar from the alligator nests at Rockefeller Wildlife Refuge in southern Louisiana to an emu farm in Massachusetts. He extracted DNA from various species in order to clone fragments of genetic material to look for specific gene expression.

Bhullar said the research has several implications. For example, he said, if a single molecular mechanism was responsible for this transformation, there should be a corresponding, linked transformation in the fossil record. "This is borne out by the fact that Hesperonis—discovered by Othniel Charles Marsh of the Yale Peabody Museum of Natural History—which is a near relative of modern birds that still retains teeth and the most primitive stem avian with a modernized beak in the form of fused, elongate premaxillae, also possesses a modern bird palatine bone," he said.

Premaxillae are the small bones at the tip of the upper jaw of most animals, but are enlarged and fused to form the beak of birds.

Bhullar noted that this same approach could be used to investigate the underlying developmental mechanisms of a host of great evolutionary transformations.

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3.7 / 5 (3) May 12, 2015
"The beak is a crucial part of the avian feeding apparatus

...and flight apparatus. I think a snout/flat face would not be well suited for flight.
5 / 5 (2) May 12, 2015
"The beak is a crucial part of the avian feeding apparatus

...and flight apparatus. I think a snout/flat face would not be well suited for flight.

So what about bats?
3.7 / 5 (3) May 12, 2015
Bats make up for this with another mechanism
1 / 5 (5) May 12, 2015
All organs in living organisms are usefull only when they are fully completed structurally and functionally. Each organ or system is controlled by hundreds of interrelated genes and this harmonic relations should emerge simultaneously to allow the organism to be functional. All organs interact and change in the behavior of given organ or system affect the whole organism. There is no mechanism for selection of random mitations by which to achieve targeted accumulation of little random changes in the genetic information in specific direction to emerge a new organ or system. The wings of birds are no exception and is quite fun to read articles related to the weak attempts of some researchers to explain the impossible by wishful thinking.
5 / 5 (3) May 12, 2015
@viko It is difficult to tell if you are as stupid as your comments make you sound or if you are deliberately making statements designed to annoy and anger anybody who can think for themselves. If you do know better then that would make your statements lies and consequently that would make you a sin on your way to hell.

It is clear that you are some kind of creationist - there are as many different creationists it seems as there are creationists which would be another feather in the cap of evolution if only you the eyes to see.
1 / 5 (5) May 12, 2015
I do not heard your arguments. People here hardly interested in your emotional state.
Can you expalin for example how mamals emerge?
5 / 5 (1) May 13, 2015
Viko, that is because you refuse to hear it. http://en.m.wikip..._mammals . are you truly willing to give up your stubborn bible based views on evolution and creation if enough evidence is presented?
What evidence would you need to do so? We want to help you understand but you need to open your mind past your god and the book that's you believe is his word.
not rated yet May 13, 2015

...and flight apparatus. I think a snout/flat face would not be well suited for flight.

Such as the ones of the chiroptera and megachiroptera for instance ?

5 / 5 (1) May 13, 2015
If you go to the early birdlike dinosaur models then you notice that the beak has a steering function. Bats have a more flexible wingstructure and can make for this through deformation of the wings.

If you look for efficiency you will find contradicting reports
Birds better:
Bats better:

But when all is said and done: Birds certainly are capable of migrating far greater distances than bats.
1 / 5 (3) May 14, 2015
Without useless links explain how mamals emerged and very complex functionality for early stage development in womb, breastfeeding in mother, sucking instinct of new born and adjustment of its metabolism for milk food, which is only temporary? If the theory of evolution has a scientific explanation for this phenomenon, should not be difficult its defenders in this forum to explain it.
5 / 5 (2) May 15, 2015
"The beak is a crucial part of the avian feeding apparatus

...and flight apparatus. I think a snout/flat face would not be well suited for flight.

4.5 / 5 (2) May 15, 2015
Without useless links explain how mamals emerged and very complex functionality...

There is still an observable continuum of functionality in the animal kingdom when it comes to mammalian features such as the uterus and mammary glands. Monotremes such as echidnas, which diverged from the placental mammal evolutionary branch over 200 million years ago, have much simpler nipple-less mammary glands similar to apocrine glands and less elaborate placenta. While they lay eggs, the eggs of monotremes are withheld in the mother for some time and the yolks are provided with nutrition. Reptiles and birds display some uterine secretion as well so only amphibians and fishes are on the other end of the continuum.

The lesson here is that there is no sharp dividing line in the animal kingdom in the specialization of various organs but instead we see a gradual continuum between derived and basic features consistent with evolution.

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