What is the Evolutionary History of Amphibians?
Amphibians are a class of animal that includes modern-day frogs, toads, salamanders, newts, and caecilians (limbless amphibians). Amphibians first evolved from lobe-finned fish and primitive tetrapods about 340 million years ago. Sometimes this date is incorrectly given as 400 or 380 million years ago, but amphibian fossils have not been unearthed from these periods. Before there were any amphibians, about 380 million years ago, during the Devonian period, some fish began to evolve legs and digits. These early “tetrapodomorphs” lacked the chracteristics that define amphibians, hence they are classified as basal tetrapods rather than amphibians. Decades ago, they were classified as amphibians, though taxonomists have changed their view on the matter. This is why the origin of amphibians is sometimes incorrectly cited as 380 million years ago. Some of the earliest tetrapods include Tiktaalik, among the earliest tetrapods with a weight-bearing wrist structure, and Acanthostega, which had
