Birds evolved from reptiles in Mesozoic era and their ancestors are small dinosaurs called theropods while they belong to class aves.
Further Explanation
Birds as dinosaurs
They are evolved in Mesozoic era either from thecodonts or theropods. These are two possibilities.
Thecodonts hypothesis
These are earlier reptiles which gave rise to dinosaurs (arboreal dinosaurs called pterosaurs and crocodiles) in Mesozoic era. Their body was covered with scales.
Theropods
They were bipedal carnivorous dinosaurs having sharp teeth to tear their prey. Earlier they were non-flying and gave rise to small flying dinosaurs. Their fossil study reveals that they were similar to birds.
Birds as reptiles
Taxonomic study reveals that birds are descendants of reptiles and fossil of Archaeopteryx lithographica is the evidence.
<em>Archaeopteryx lithographica </em>
Archaeopteryx was first fossils of birds that was found in Bavarian quarry by a German naturalist. It was crow sized, bipedal, with small snout having sharp teeth, strong muscles and large furcula.
Archaeopteryx Vs modern birds
Modern birds possess larger brain with enlarged visual center as compared to archaeopteryx. Modern birds had evolved advance neural system for flight.
Aves
It is class of vertebrate birds having characteristics like bill, wishbone, pygostyle and furcula.
Answer details
Subject: Biology
Level: High school
Key words
Birds as dinosaurs
Thecodonts hypothesis
Theropods
Birds as reptiles
Archaeopteryx lithographica
Archaeopteryx Vs modern birds
Aves
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