Question

Which is a connecting link on the basis of anatomy?
A. Archaeopteryx between reptiles and mammals
B. Duck-billed platypus between reptiles and mammals
C. Lungfish between amphibians and birds
D. Seymouria between reptiles and birds

Answer 1

Hint: Connecting link is an organism with characteristics of two different groups. Represent both groups and thus help us to understand the evolutionary line.
Complete step by step answer:
Some well-known examples for connecting links are Archaeopteryx, Duck-billed platypus, Lungfish, Seymouria, Balanaglossus, Peripatus.

Connecting link	Group 1	Group 2	Common features of two different groups.
Archaeopteryx.	Aves.	Reptiles.	Body covered with scales has a long tail, solid bones, incomplete division of heart like that of reptiles, wings, and beak as in Aves.
Duck-billed platypus.	Reptiles.	Mammals.	An egg-laying mammal with the body covered with hairs. Resembles reptiles by having coracoid in the pectoral girdle and production of amniotic eggs.
Lungfish.	Pisces.	Amphibia.	Presence of lobed fins like that of Pisces and have the ability to breathe in air.
Seymouria.	Amphibia.	Reptiles.	Short limbs, labyrinthodont teeth, amphibian features, Cleidoic eggs, interclavicles like reptiles.

So, the correct answer to the given question is option B. Duck-billed platypus is the connecting link between reptiles and mammals. In all other options, the groups are incorrectly mentioned.

Note: A connecting link is a living link between two groups whereas, the missing link is an extinct organism that shows characters of both groups.
A connecting link is sometimes referred to as a coupling link. The study of connecting links is important to understand the evolutionary line.