Question

Describe the origin of tetrapods and identify some of their key derived traits.

Short answer

The four-limbed tetrapod was found to evolve between 360 and 390 million years ago from the fin-lobed fishes during the Devonian period due to the development of breathing of air and resource available on the land. They are the present day's chordates with four limbs.

The most prominent trait is the presence of a distinct vertebrate in the neck that separates the head and the body. The fused structure of the pelvic girdle with the backbone is an inheriting derived trait.

Step-by-step solution

Origin of tetrapod

The tetrapod originated from the lobed fishes found in the Devonian period about 360 million years ago. These fishes developed adaptation for breathing air and acquired sources from the land by developing legs from the gills.

Key characters of tetrapod

All the chordates with four limbs, reptiles, and amphibians belong to the superclass Tetrapoda.

They have limbs for locomotion which is the most distinctive trait of the tetrapod. The cranial bone is a prominent feature separating the body from the head and providing stability to the head movement.

Other derived traits inherited are the development of a skeletal and muscular system that enables movement. The presence of cranial bone helps in head stability during motion.

The inheritance of fish traits

The limbs in the tetrapod are the evolved structures of the fins in fishes. Muscular tongues are also a representative structure in tetrapods. The presence of dead skin cells in reptiles and the absence of internal gills are also inheriting derived traits.