nonamniotes

Nonamniotes are a group of tetrapods, or four-limbed vertebrates, that do not lay amniotic eggs. This group includes amphibians and their extinct relatives. The term "nonamniote" is used to distinguish these animals from amniotes, which are tetrapods that do not require water for reproduction and instead lay amniotic eggs. Nonamniotes are characterized by their permeable skin, which allows for gas exchange and water absorption, and their dependence on aquatic environments for reproduction. They have a larval stage, often called a tadpole, which undergoes metamorphosis into an adult form. Nonamniotes are further divided into two main groups: Lissamphibia, which includes modern amphibians like frogs, salamanders, and caecilians, and Temnospondyli, which are extinct and include animals like the rhynchocephalia and the seymouriamorphs. The study of nonamniotes provides valuable insights into the evolution of tetrapods and the transition from aquatic to terrestrial environments.