What was the first reptile?

Answered by Tom Adger

The first reptile is believed to have evolved from amphibians during the Carboniferous period, around 300 million years ago. This transition marked an important milestone in the evolution of vertebrates, as reptiles adapted to a more terrestrial lifestyle compared to their amphibian ancestors. The exact identity of the first reptile is uncertain, as the fossil record from this time period is incomplete. However, one of the oldest known reptile fossils, nicknamed Lizzie, was discovered near Edinburgh and is estimated to be around 330 million years old.

Lizzie, as she is affectionately called, provides important insights into the early evolution of reptiles. This fossil belonged to a group of reptiles known as reptiliomorphs, which were close relatives of the true reptiles. Reptiliomorphs had certain reptilian characteristics, such as scaly skin and a more efficient respiratory system, but still retained some amphibian-like features. They were likely semi-aquatic animals that inhabited both land and water environments.

The transition from amphibians to reptiles was a gradual process, with various lineages experimenting and evolving different adaptations. One of the key evolutionary innovations of reptiles was the development of an amniotic egg. Unlike amphibians, which rely on water for reproduction, reptiles were able to lay their eggs on land. The amniotic egg, protected by a leathery or hard shell, provided a secure and self-contained environment for the developing embryo. This adaptation allowed reptiles to colonize diverse habitats and become less dependent on aquatic environments.

Another significant characteristic of reptiles is their ability to regulate their body temperature. Unlike amphibians, which are ectothermic (rely on external sources of heat to regulate body temperature), reptiles are mostly ectothermic, but some groups, such as birds and mammals, have evolved endothermy (the ability to generate and maintain internal body heat). This thermoregulatory ability allows reptiles to thrive in a wide range of climates, from warm tropical regions to cold temperate zones.

Reptiles encompass a diverse group of animals, including lizards, snakes, turtles, crocodiles, and dinosaurs. They have adapted to various ecological niches and have colonized nearly every continent on Earth. Today, lizards still exist in warm countries, showcasing the resilience and success of reptiles as a group.

The first reptile is believed to have emerged from amphibians around 300 million years ago. While the exact identity of the first reptile remains uncertain, fossils like Lizzie provide valuable insights into the early evolution of reptiles. The transition from amphibians to reptiles involved the development of key adaptations, such as the amniotic egg and the ability to regulate body temperature. Reptiles have since diversified into numerous species, occupying a wide range of habitats and climates across the globe.