Question

Evidence of the reptilian origin of birds is the occurrence of
a.Scales
b.Hairs
c.Claws
d.Feathers

Answer 1

Birds belonging to class Aves have some unique features such as they are warm-blooded animals, forelimbs are modified into wings, etc.

Complete answer:
There are various theories regarding the evolution of birds. Let us analyse all the given options to find out the correct answer.

Option a: The scales of birds are composed of keratin. It is present on the beaks, claws, and spurs. They are found mainly on the toes and metatarsus but may be found further up on the ankle in some birds. Thus evidence for the reptilian origin of birds is the occurrence of scales. Therefore, this is the correct option.
Option b: Birds do not have any hair or instead, they have feathers. Feathers help in keeping birds warm and also help insulate them from the water. Reptilia also don’t possess hairs on their body. The presence of hair is a peculiar characteristic of class Mammalia. Therefore, this is an incorrect option.
Option c: Claw is found at the end of a toe or finger in many mammals, birds, and some reptiles. However not all the reptiles possess claws. Therefore, this is an incorrect option.
Option d: Earlier the feathers of birds were thought to evolve directly from reptilian scales, as once was thought. But current hypotheses suggest that they evolved through an invagination of the epidermis around the base of a dermal papilla. Therefore, this is an incorrect option.
Hence the correct answer is option ‘C’.
Note: It is to be noted that fossil records suggest that modern birds originated 60 million years ago, after the end of the Cretaceous, however molecular studies suggest that the genetic divergences between many lineages of birds occurred during the Cretaceous period.