Question

Modern birds rose in
(a) Paleozoic
(b) Cenozoic
(c) Mesozoic
(d) Archaeozoic

Answer 1

The birds gradually evolved with the fall of dinosaurs around 65 million years ago with the end of the Jurassic period.
Modern birds rose in the Mesozoic era. The Mesozoic era lasted from 245 to 65 million years ago. In the Cretaceous period, the birds evolved gradually to form the modern birds.

Complete answer:
The evolution of birds began in the Jurassic period of the Mesozoic era. The earliest birds were derived from the dinosaur named Paraves. The small flying dinosaurs 'Archaeopteryx lithographica' is considered as the earliest bird and the link between the reptiles and birds. The skeletal system of all early birds is similar to that of the theropod dinosaurs. During the cretaceous period, the modern birds evolved to possess a more rigid rib cage, more developed pygostyle (boneless tail), and an alula to achieve better control overflight and landing.
The paleozoic era is the earliest era lasting from 541- 251 million years ago. It was further divided into six geological periods, namely, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Cenozoic era lasted for 65- 1.5 million years ago.
So, the correct answer is ‘Mesozoic'.

Note:
- The sequence of eras with the recent first is Cenozoic, Mesozoic, Palaeozoic, and Archaezoic. The Mesozoic era further consists of the Cretaceous, Jurassic, and Triassic periods.
- The modern birds are classified in Neornithes which is further classified into paleognaths and neognathae. It is also said that the neognaths even existed before the cretaceous period.
- The Cretaceous period gave rise to four different lineages of birds, namely, Paleognath, Anseriformes, Galliformes, and modern birds (Neoaves).