Question

Reptilian ancestry of birds is shown by the presence of
(a) Scales on the hind limb
(b) Non-cleidoic eggs
(c) Teeth in beaks of birds
(d) Three chambered heart

Answer 1

Hint: Theropod dinosaurs are characterized by hollow bones and three-toed limbs. They were the most diverse group of saurischian (“lizard-hipped”) dinosaurs, size ranging from the crow-sized Microraptor to the huge Tyrannosaurus rex. Many larger theropods had skin covered with small, bumpy scales.

Complete answer:
  Discovery of a specimen of archaeopteryx in the early 1860s has given rise to the concept that birds have evolved from small carnivorous dinosaurs (theropod) of late Jurassic ancestors of living birds. Since the body of a bird is covered with feathers and has scales on their legs and feet. Their beaks and claws also have scales that support the reptilian ancestry of birds.
Archaeopteryx shows the features of both the theropod dinosaurs as well as modern birds. Thus it is widely considered as a transitional fossil between the birds and reptiles.

Archeopteryx

Non-cleidoic eggs are not covered with shell and are laid in water without the sufficient nutritive material for the complete development of the embryo. These eggs generally hatch into a larva.
The three-chambered heart is the characteristic of amphibians and reptiles. There occurs some mixing of blood and has double circulation.

So, the correct answer is’ scales on hind limbs’.

Note:
1. The first specimen of Archaeopteryx was discovered(1860) and named(1861) by the German palaeontologist Hermann von Meyer near Solnhofen, Germany.
2. Theropods first appeared in the earliest part of the Upper Triassic about 230 million years ago. They were the sole large terrestrial carnivores from the Lower Jurassic until the close of the Cretaceous, about 65 million years ago.
3. The Discovery of four new fossils of Ichthyornis (bird of Cretaceous Period), which had both a beak and teeth and lived a lifestyle like modern gulls, played an important role in avian evolutionary history.