Birds are relatives of the long-extinct dinosaurs. They are diverse, living on every continent and coming in various sizes and shapes.
Scientists believe their ancestors, the maniraptorans, survived mass extinction because of their beak shape, intelligence, and small size.
So, how did avian dinosaurs survive when all others died?
Avian Dinosaurs Before the KT Extinction Event
Pterodactyls and other pterosaurs are not avian dinosaurs. They were flying reptiles that lived millions of years ago alongside dinosaurs. However, they were part of a different animal group. Pterosaurs died out alongside many ancient marine reptiles long before the KT extinction.
Avian dinosaurs (also known as birds) are descendants of dinosaurs. More specifically, birds are descendants of theropods, which were the two-legged, flesh-eating dinosaurs that roamed Earth millions of years ago. Theropods included a wide range of dinosaurs, including the famous T-Rex.
The closest descendants of ancient birds were raptors, however. The oldest bird fossils are 150 million years old. These birds had sharp teeth and looked like tiny dinosaurs but were about the size of a duck.
Feathers developed on dinosaurs long before flight. Nowadays, it is believed that most dinosaurs possessed feathers of some sort. There were probably used for thermal insulation. However, feathers were also important for the development of flight.
As certain dinosaurs began to evolve smaller, their feathers could be used to glide through trees. From gliding, flight became possible.
The archaeopteryx, a dinosaur that live 150 million years ago, could probably take short, low-level flights. This was probably one of the first leaps in evolution towards the development of birds.
Archaeopteryx were theropods with teeth and bony tails. They had a wishbone, or furcula, which helped them to fly. Most of today’s birds have this bone, too. They also had long claws.
When archaeopteryx was first found, in 1861, they believed they had found the world’s first bird. Yet, since then, many other bird-like dinosaurs have been discovered.
The Dinonynchus was a small, carnivorous dinosaur that lived during the Cretaceous period. It had one huge claw on each foot that it used to rip apart its prey. This group of small dinosaurs was part of a group called maniraptorans, which are believed to be early descendants of birds.
Scientist John Ostrom started to piece together the connection between archaeopteryx and deinonychus in the late 1960s. He began to give evidence for the evolutionary links between dinosaurs and birds based on these two dinosaurs’ fossils. Before this, scientists saw a loose connection but weren’t 100% sure they were directly related.
In 1996, when more therapods were discovered to have feathers, it became more apparent that birds descended from them. More maniraptorans were discovered that had many of the characteristics that make birds distinct.
Archaeopteryx is considered the first avian dinosaur or bird, but Deinonychus is a step on the evolutionary stairway to birds.
Why Didn’t They Die with the Other Dinosaurs?
When the asteroid hit Earth, it blocked out the sunlight with a large dust cloud. This killed off much of the plant life. Without large plants, the gigantic herbivorous dinosaurs starved and died out. Without prey to feed upon, the carnivorous dinosaurs followed.
Avian dinosaurs were smaller and better able to adapt to the changing environment more quickly. Smaller animals don’t need to eat as much and reproduce quicker. This means that with each generation, they were able to adapt to the new situations, and natural selection was able to allow these avian dinosaurs to fit into the now vacant niches throughout the world.
Their beak shapes gave them the ability to eat a wider variety of foods, from plants to seeds to small animals. This meant they didn’t have to rely on one food source to survive.
Flight also gave them the advantage of being able to move around more quickly and easily. They could find food in wider ranges and get away from unsafe environments more quickly.
Nowadays, birds serve as a link to the ancient dinosaurs that roamed the Earth millions of years ago. They have a great history with missing links still yet to be discovered, but each year scientists learn more about the journey these creatures took from dinosaur to bird.
Birds have diversified to fit into every climate and continent in the world. They come in all shapes and sizes and possess a myriad of different skills and adaptations. These remarkable creatures still share many of the characteristics of their ancient ancestors. Looking at a bird is like getting a glimpse into ancient history.