Based on evidence, why did dinosaurs evolve into birds?

[Jonathanaronda]

Hi, all! Based on evidence, I'd like to know how and why dinosaurs evolved into birds? What was the selection pressure for them to evolve wings? Also, why did they become smaller? Does it have to do with evolving wings for flight?

 

I was actually under the impression that the selection pressure for them to evolve into birds was due to the asteroid that hit Earth. I thought that because of the asteroid, food supply was short and this resulted in dinosaurs becoming smaller and flight based to hunt for bigger food. Turns out I may have been wrong with this assumption as pointed out by another poster in another thread I wrote awhile back.

 

And yes, I know google is friendly, but I love hearing the responses of other people on forums.

[Moontanman]

Hi, all! Based on evidence, I'd like to know how and why dinosaurs evolved into birds? What was the selection pressure for them to evolve wings? Also, why did they become smaller? Does it have to do with evolving wings for flight?

 

Birds started as small theropod type dinosaurs, they climbed trees and ran fast to catch their prey. Dinosaurs had already evolved feathers for warmth well before there were birds. The type feathers modern birds have possibly evolved for gliding and or to stabilize them as they ran. Some of these early birds actually had four wings, their hind legs serving was wings as well.

 

I was actually under the impression that the selection pressure for them to evolve into birds was due to the asteroid that hit Earth. I thought that because of the asteroid, food supply was short and this resulted in dinosaurs becoming smaller and flight based to hunt for bigger food. Turns out I may have been wrong with this assumption as pointed out by another poster in another thread I wrote awhile back.

 

 

No in fact there were birds well before the impact that killed the dinosaurs, there were birds with long tails, birds with teeth, birds with all sorts of features we do not see today. Only a small subset of birds survived the K/T extinction to radiate out into the species of birds we see today.

 

 

http://www.nytimes.com/2013/03/15/science/early-bird-species-had-four-wings-scientists-find.html?_r=0

 

http://www.google.com/search?q=primitive+birds&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=6dF2UZ6mAsfW0QX9-4HgCQ&sqi=2&ved=0CDkQsAQ&biw=1152&bih=777

 

http://www.livescience.com/16105-cosmic-impact-extinction-archaic-birds.html

 

BTW, pterosaurs were not birds or dinosaurs...

[StringJunky]

Here's four models for the evolution of avian flight that you might want to look into...a brief description of each is in the link:

• Cursorial Model
• Wing-Assisted Incline Running Model
• Pouncing Proavis Model
• Aboreal Model

http://en.wikipedia.org/wiki/Origin_of_avian_flight

 

 

[Protoart]

Well, at first a terrestrial coelurosaur needed to expand its range.

[BTF/PTM]

Dinosaurs didn't evolve into birds in the sense of a direct, species-wide change. The same is true for us, we did not evolve directly or species-wide from apes, one branch of a past ape species adapted characteristics that eventually led to us becoming us, and parallel branch species either adapted other characteristics or remained as they were. One branch of the dinosaur tree began to adapt characteristics that eventually enabled flight, and that branch eventually became the creatures we know as birds.

 

The evidence visible in birds are the many reptilian characteristics of birds, as well as dinosaur skeletons having recently been found with hollow bones and of course the numerous skeletons found with predecesors of modern feathers on their bodies.