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Mammals did not evolve from dinosaurs.
Birds branched off from a group of dinosaurs called theropods, the two-legged carnivores that included T. rex and Velociraptor. Even before birds evolved many theropods already had feathers, probably for insulation. From here there are two main hypotheses about how these dinosaurs evolved into birds.
First is the "ground up" hypothesis, which proposes that small theropod dinosaurs held their arms out in chasing prey such as insects. Certain arrangements of feathers might have allowed them to run faster or lighter, which became enhanced as the arms became precursors to wings. This then gradually transitioned into "wing" aided jumping, then gliding, and finally true flight.
Second is the "trees down" hypothesis. It proposes that small, tree-climbing theropods that jumped from branch to branch were able to use their feathers on their arms and legs for gliding, this gradually developed into true flight. Fossils that may match this description have been found.
What else can I help you with?
Which are older mammals or birds?
Mammals are older. The first mammals evolved around 220 million years ago, not long after the first dinosaurs. Birds evolved from small carnivorous dinosaurs about 160 million years ago.
Did mammals evolve from dinosaurs?
No. Mammals evolved from synapsid reptiles, a group not closely related to dinosaurs. Dinosaurs are more closely related to modern reptiles and birds than they are to mammals.
What did birds and mammals descend from?
Mammals evolved from mammal-like reptiles called synapsids in the late Triassic period. Birds evolved from theropod dinosaurs in the late Jurassic.
Why aren't dinosaurs mammals?
Dinosaurs and mammals evolved from two separate branches of reptiles. Mammals evolved from synapisid reptiles (all of which are not extinct) while dinosaurs along with the modern branches of reptiles evolved from sauropsids. So dinosaurs are more closely related to modern reptiles than they are to mammals. In more recent years scientist tend to agree that birds are in fact a surviving branch of dinosaurs.
Are dinosaur birds mammals?
Birds are now classed as dinosaurs, but most dinosaurs were not birds. Neither dinosaurs nor birds are mammals.
Which animal was alive first birds or dinosaurs?
Dinosaurs evolved first and then some dinosaurs evolved into birds. So all birds are technically dinosaurs.
Are dinosaurs ancestors of humans?
No. Humans are mammals, which evolved from mammal-like synapsid "reptiles," which were not closely related to dinosaurs. Birds are the only living remnants of the dinosaurs.
Did dinosaurs evolve into reptiles?
No. Dinosaurs evolved from reptiles. Birds evolved from dinosaurs.
Mammals and birds are descended from what group of vertebrates?
Mammals and birds are both descended from a group of vertebrates known as archosaurs. This group included early reptiles and gave rise to both dinosaurs (which birds evolved from) and the ancestors of mammals.
Are animals related to birds?
Birds are more closely related to reptiles than they are to mammals. Birds, reptiles, and mammals all belong to a group of vertebrates called amniotes, which split off from amphibians. Amniotes split into two groups soon after they evolved: true reptiles and synapsids. Mammals are the only living synapsids today. Dinosaurs branched off from the reptiles and birds then evolved from the dinosaurs.
What reptile feature evolved into feathers?
Yes. Birds are animals that have feathers.
Why do scientists believe that birds evolved from dinosaurs?
Scientists believe birds evolved from dinosaurs because of several pieces of evidence, such as shared skeletal features, fossil records of "transitional" bird-like dinosaurs, and genetic similarities. These connections suggest that birds are the descendants of a group of small theropod dinosaurs.
