Sarcopterygians, also known as lobe-finned fish, are a group of fish characterized by their fleshy, lobed fins. These fins are supported by bone structures similar to those found in the limbs of tetrapods, which include amphibians, reptiles, birds, and mammals. Sarcopterygians are believed to be the ancestors of all land vertebrates. This group includes both extant species, like the coelacanth and lungfish, and extinct species that lived millions of years ago. Sarcopterygians played a crucial role in the evolution of vertebrates, as their adaptations allowed some species to transition from water to land during the Devonian period.