Class Reptilia

These organisms were among the first to successfully adapt to life on land. They are thought to have descended from amphibians millions of years ago, according to evolutionary theory. On the planet, there are approximately 10000 different species of reptiles. Cold-blooded animals belonging to the phylum Chordata of the Animal kingdom, they are also known as polar bears.

The skulls of the reptiles have been modified in such a way that the reptiles can bite with an efficient and powerful jaw action. In addition, the modification makes the skull lighter.

Characteristics of Reptilia

The following are some of the most distinguishing characteristics of the animals that belong to the Class Reptilia:

These are terrestrial animals that creep and burrow through the ground and have scales on their bodies.

They are cold-blooded animals that can be found in most of the world’s more temperate climates.

Their skin is dry and rough, and it lacks any glands to protect them.

The body is divided into four sections: the head, the neck, the trunk, and the tail.

Only a few of these animals shed the scales on their skin in the form of skin cast.

It is the lungs that are responsible for the process of respiration.

The skull has a single condyle.

It is possible that limbs are present or not. In the event that they do have limbs, they are two pairs of pentadactyl limbs, each with a pair of claws. Snakes are devoid of any limbs.

The heart has three chambers. Crocodiles, on the other hand, have a heart with four chambers.

Cranial nerves are divided into 12 pairs, which make up the nervous system.

Reptiles do not have external ear openings, as do birds and mammals. The tympanum is the representation of the ear.

They have a cloaca that is typical of the species.

The majority of reptiles are uricotelic. Uric acid is the most common form of nitrogenous waste excreted by them.

Fertilisation takes place internally.

As oviparous as they are, their eggs are extremely yolky. The process of development is straightforward.

Snakes, turtles, lizards, and crocodiles are examples of such creatures.

Classification of Reptilia

The class Reptilia is differentiated into three major subclasses:

• Anapsida
• Parapsida
• Diapsida

Anapsida

• It is the dermal bones that provide a complete roof over the skull, as there are no temporal fossae.
• Cotylosauria and Chelonia are subdivided into the Cotylosauria.
• Chelonians of the modern era are classified according to the method by which they retract their heads into their shells.
• Turtles, tortoises, and terrapins are examples of animals that fall into this category.

Parapsida

One temporal fossa is present in the skull of these reptiles, which is located high on the skull.

This type of skull was found in Protosaurs, Nothosaurs, and Placodonts.

The Ichthyosaurs and the Plesiosaurus were the two most numerous groups of dinosaurs. Many other reptiles and dinosaurs perished at the end of the Cretaceous period, contributing to the extinction of this species.

Diapsida

There are two temporal vacuities in the skull, one on either side of the midline.

They are the most diverse group of reptiles.

This group includes the dinosaurs and pterosaurs, among other creatures.

Archosauria and Lepidosauria are the two major groups of dinosaurs that have been identified.

For example, Crocodilus and Chameleon

Extinct groups of class Reptilia

• Ichthyopterygia
• Lepidosauria
• Archosauria
• Synapsids

Ichthyopterygia

There are two temporal vacuities in the skull, one on either side of the midline, and they are located on either side of the midline.

These reptiles represent the most diverse group of all.

Among other creatures, the dinosaurs and pterosaurs are included in this group of creatures.

Currently, the Archosauria and the Lepidosauria are the two most significant groups of dinosaurs that have been discovered.

For instance, the Crocodilus and the Chameleon

Lepidosauria

All of the lizard-like reptiles were gathered in one place.

They had two temporal vacuities in their skulls, which was unusual.

For example, Youngina.

Archosauria

• The skulls were diapsid.
• Some were bipedal which gave rise to birds.
• They also gave rise to dinosaurs.
• Eg., Brontosaurus

Synapsids

• They had one temporal fossa on the lower side of the skull.
• These were the most dominant group of reptiles during the Permian period.
• The surviving Lepidosaurs in the Mesozoic era gave rise to mammals. The rest were replaced by dinosaurs.
• Eg., Plesiosaurus.

Characteristics Of Phylum Chordata

Phylum Chordata possesses the following characteristic features:

Notochord

Between the nerve cord and the digestive tract, it is a cartilaginous rod that runs longitudinally through the body. After the embryonic stage in all vertebrates, it serves as a support for the nerve cord and is replaced by the vertebral column after that stage.

Dorsal Nerve Cord

It is a bundle of nerves that runs along the “back” of the body and divides into two parts: the brain and spinal cord. It is hollow and is located dorsal to the notochord on the thoracic spine.

Pharyngeal Slits

As the name implies, they are the openings that allow water to pass through the mouth without entering the digestive system; in other words, they connect the mouth and the throat. The lateral sides of the pharynx on the lateral sides of all Chordates have these openings at some point in their lives.

Post anal Tail

It is a continuation of the body’s extension to the anus. Chordates have a tail that is made up of skeletal muscles that aid in locomotion in fish-like animals. It is not present in the majority of adult Chordates.

Chordates have a variety of other characteristics, including a body that is bilaterally symmetrical, triploblastic, coelomic, and segmented.The body design is complex and distinct from the rest of the vehicle.The organ systems of the body are the highest level of organisation in the body.

Conclusion

Reptiles are the animals that belong to the class Reptilia and are commonly referred to as such. Among the many fascinating aspects of reptiles is the widespread belief among scientists and researchers that they were the first creatures to establish life on the planet. Scientists also believe that the ancestors of the reptiles were amphibians, and that the Reptiles evolved from there approximately millions of years ago.