As a first blog post I want to talk about the origin of amphibians and reptiles, which although it may be a somewhat confusing and heavy topic, I think may be a good basis for future articles.
The evolutionary process of amphibians and reptiles began about 370 million years ago in the Devonian period. Certain lobe-finned fishes (Sarcopterigios) developed certain traits that allowed them to explore the terrestrial environment for the first time since the aquatic environment was very unstable and with desiccation problems, which drove them to make small incursions into the terrestrial world. Some modifications were related to the pharynx, where a cavity was developed that was filled with air and even internal nostrils that allowed them to introduce oxygen-rich air to perform the gas exchange. This first group of animals that managed to adapt in a limited way to an intermediate life between the aquatic and terrestrial environment later developed the own adaptations of the tetrapods.
These adaptations can be summarized in the formation of the lung for optimal breathing out of water and a double blood circulation, evolution of the extremities from the fins of fish to reach the extremity type of tetrapods called chiridium, which allowed the heavy body to move in the terrestrial environment. There was also a greater development of eyes and ears, reinforced pectoral and pelvic waists and the lower jaw is attached to the skull. These characteristics can be observed in Ichthyostega and Acanthostega as representatives of the first group of tetrapods that could get out of the water.
At the same time, in the upper Carboniferous, different groups of primitive "amphibians" were developed until they reached the modern amphibians Lissamphibia, of which it is not known for sure which group they can prevent; and the amniotes, which would give rise to the current reptiles among others.
The amniotes would be related to a group of anamniotes called Anthracosauria of the Carboniferous and would develop a series of own and optimal characteristics for the terrestrial life away from the aquatic environment, like the appearance of the amniotic egg allowing a greater protection against blows, a greater transference of oxygen and smaller loss of water, a thick, keratinized and impermeable skin that would limit water loss, an
internal fertilization without larval phases and metamorphosis eliminating the need for aquatic environments, present cranial fenestration bringing lightness to the skull and a new zone of anchorage for muscles that can generate a greater force to the jaws to crush the prey, circulatory system functionally divided into pulmonary and systemic circuits, exclusively pulmonary breathing, greater development of the nervous system and are ectothermal.
All of these characteristics have given reptiles the ability to conquer practically any ecosystem on the planet successfully.
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