Answer:
When people think of dinosaurs, two types generally come to mind. There were the huge herbivores,
like Apatosaurus, with their small heads and long tails. There were also those fearsome carnivores,
like Tyrannosaurus rex, that walked on two legs and had a mouthful of teeth like kitchen knives.
Living Dinosaurs
These large dinosaurs are no longer around, but dinosaurs still live among us today. They are the
birds. It's difficult to imagine that a bird on your window sill and a T. rex have anything in common.
One weighs less than a pound. The other was the size of a school bus, tipping the scales at eight
tons. But for all their differences, the two are more similar than you might think. In fact, birds and T.
rex are close relatives. They all belong to a group of dinosaurs called theropods.
This is a cladogram, a "" showing the relationships among organisms. The group called dinosaurs includes the extinct dinosaurs
and all their living descendants. All its members, including living birds, descended from the very first dinosaur-their common ancestor.
That's why birds are a kind of dinosaur (just as humans are a kind of primate).
Skeletal Evidence
When paleontologists compare a skeleton of a living bird to the
fossilized skeleton of a non-bird theropod, like Sinornithosaurus,
they see many similarities. They both have a hole in the hipbone, a
feature that distinguishes most dinosaurs from all other animals.
This feature allows an animal to stand erect, with its legs directly
beneath its body. All theropod dinosaurs, including birds, have a
furcula, also known as a wishbone. Another shared characteristic is the presence of hollow bones.
Hollow bones reduce the weight carried by an animal. This feature enables the animal to run faster. It
probably also played a role in the evolution of flight.
thought to have evolved for flight. The discovery of more and more non-flying dinosaurs with feathers
disproved that explanation. For these dinosaurs, feathers may have served other functions, like
gliding, insulation, protection, and display. Feathers play that same role in many bird species today.
Based on the evidence of shared characteristics, scientists have concluded that birds are a type of
Birds are the only dinosaurs with the ability to fly. This is
very interesting to scientists who want to know when the
capability of flight emerged. To find out, some scientists
study the brains of bird and non-bird dinosaurs. Soft
tissue, such as brains, is almost never preserved in the
fossil record. What is preserved is the imprint the brain
left on the inside of the skull. Now scientists are using
computed tomography (CT) scanners to create
endocasts. These are detailed, three-dimensional
reconstructions of the interiors of fossilized skulls.
In a recent study, researchers were able to peer inside
the braincases of more than two dozen specimens.
"Technology allows us to look inside these specimens
without destroying them," says Dr. Amy Balanoff, a
Museum research associate. "It's a non-destructive way
to basically slice up a dinosaur brain. We look inside and see what it can tell us about the evolution of
the brain within dinosaurs. Most of us grew up thinking that dinosaurs had tiny brains, but actually
some had really big brains."
The endocasts allow Balanoff and other researchers to
explore the outer shape of the brain in more detail. In
addition, the casts also provide new information about
the volume and shape of different regions of the brain.
For example, scientists looked at a detailed view of the
dinosaur cerebrum, a region of the brain related to
cognition and coordination. They found that this region
was very large in non-bird dinosaurs closely related to
birds. Dr. Balanoff's research suggests that these
dinosaurs developed big brains long before flight and that
these bigger brains prepared the way for them to fly.
When examining skeletal, behavioral, and brain
evidence, scientists see that birds and non-bird dinosaurs
share many features. This helped them conclude that
dinosaurs aren't extinct after all. They're living among us today.
(Im a really fast Typer and Thinker)
Have a nice day