Dinosaurs are a diverse
group of animals of the clade Dinosauria. They first appeared during
the Triassic period, 231.4 million years ago, and were the
dominant terrestrial vertebrates for 135 million years, from the
beginning of the Jurassic (about 201 million years ago) until
the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene
extinction eventled to the extinction of most dinosaur groups at the close of
the Mesozoic Era. The fossil record indicates that birds evolved
from
theropod dinosaurs during the Jurassic Period and, consequently, they are considered a subgroup of dinosaurs by many paleontologists.[1] Some birds survived the extinction event that occurred 66 million years ago, and their descendants continue the dinosaur lineage to the present day.[
Dinosaurs had adaptations which
helped make them successful. The first known dinosaurs were small predators that walked
on two legs. All their descendents had an upright posture,
with the legs underneath the body. This transformed their whole life-style.
There were other features. Most of the smaller dinosaurs had feathers, and
were probably warm-blooded. This would make them active, with a higher metabolism than
modern reptiles. Social interaction, with living in herds and
co-operation seems very likely for some types.
The first dinosaur fossils were
found in the early 19th century. They are major attractions at museums around
the world. Dinosaurs also became part of popular culture. There have been
many best-selling books and movies. New discoveries are widely covered in the media.
0 comments :
Post a Comment