Where Did the Dinosaurs Go?

Bambiraptor, possibly an early link between birds and dinosaurs. Note the proto-feathers covering the animal. Image credit: http://www.amnh.org 

Bambiraptor, possibly an early link between birds and dinosaurs. Note the proto-feathers covering the animal.
Image credit: http://www.amnh.org 

Tyrannosaurus rex foot. Image credit: http://jerseyboyshuntdino aurs.blogspot.com

Tyrannosaurus rex foot.
Image credit:
http://jerseyboyshuntdino
aurs.blogspot.com

Adult Hoatzin with chick.
Image credit: 
http://jerseyboyshuntdino
aurs.blogspot.com

Close-up of chick’s wing with two claws.
Image credit: 
http://jerseyboyshuntdino
aurs.blogspot.com

We all know the prevailing theory about how the dinosaurs went extinct. A giant meteor collided with the earth in South America, sending up a huge cloud of dust that obscured the sun’s rays, resulting in climate change that was too much for cold blooded dinosaurs to survive.

But that’s not the whole story. One of the most iconic families of dinosaurs survived, and you see them every day! That family is Dromaeosaur, a group of theropod (bipedal) dinosaurs that includes, among others, Velociraptors and the dreaded Tyrannosaurus rex. But, how did these dinosaurs survive, and where are they today?

They became something else, birds! Evidence is mounting that describes an evolutionary link between modern day birds and Dromaeosaurs, through a common ancestor like Archaeopteryx.

They became something else, birds! Evidence is mounting that describes an evolutionary link between modern day birds and Dromaeosaurs, through a common ancestor like Archaeopteryx.

It is now generally accepted that many Dromaeosaurs had feathers, or proto-feathers, though their function is still debated.

Amazingly, we can still find physical vestiges of their dinosaur heritage in today’s birds. The legs of birds are very similar to Dromaeosaur legs. Birds and dinosaurs are the only obligate bipeds ever, meaning they must walk on their two hind legs. Additionally, running birds like ratites and gallinaceous species have feet that are almost identical to dino legs.

Dromaeosaurs also have modified wrist and arm bones that allow them to make the flapping motion required for flight.

Perhaps the most striking trait that still exists is the remnants of claws on the forearm of Dromaeosaurs. Many galliformes and ratites still have small claws on the ends of their finger bones, but they are obscured by feathers so we never see them. However, one bird still uses these claws, as chicks, to help climb around the precarious branches it is born in.    

The hoatzin is native to mangrove forests in the Amazon basin. Learning to fly in the branches of mangroves with nothing to fall into but water presents a problem for young birds. But, by using the claws on their first two fingers, the chicks can fall into the water and haul themselves back out, using their wings like arms.

So it seems the dinosaurs didn’t all go extinct, they just changed. Profound climatic changes killed off the icons like T-rex, but smaller, warm-blooded, feathered creatures were already taking to the air, to eventually colonize the entire world. Some of them survive to this day, filling the sky with their colors and the air with their music.

Cited works:
http://jerseyboyshuntdinosaurs.blogspot.com/2012/07/birds-are-dinosaurs-simple-fact.html
http://www.amnh.org/explore/science-topics/birds-are-dinosaurs
http://www.ucmp.berkeley.edu/diapsids/avians.html