(from Greek meaning flesh fin) contains the so called lobe-finned
fishes, further divided into the coelacanths and lungfish. Importantly,
the limb like fins of sarcopterygiians are so similar to the expected
ancestral form of tetrapod limbs that the scientific consensus
has emerged they are the ancestors all tetrapods. Sarcopterygians
are placed in the Osteichthyes group (bony fishes), because their
skeleton is bone rather than cartilage, and are therefore most
closely related to the Actinopterygians.
The oldest which appear in the late Silurian closely resemble
Rhipidistia (ancestors of the tetrapods)
Sarcopterygians lineage split in the lower Devonian into the Coelacanths
and the Rhipidistia. The fossil records suggests that the Coelacanths
peaked during the Carboniferous. They were believed to have gone
extinct at the end of the Cretaceous, until the genus Latimeria
was discovered off the east coast of South Africa in 1938; since
then, other Latimeria have been discovered in Kenya, Mozambique,
Tanzania, Madagascar, and South Africa. Coelacanths are often
considered to be living fossils.
appeared with the Coelacanths, but migrated from marine to freshwater
habitats, probably initially near the mouths of rivers. The Rhipidistia
lineage split into two major groups, lungfishes and tetrapodomorphs.
The lungfishes evolved the earliest primitive lungs and limbs,
peaked in the Triassic, and remain an extant though minor taxon.
Lungfishes used their stubby fins to walk on land and find new
water if their waterhole was depleted, with their lungs breathing
air, just like modern species do. Rhipidistia is now understood
to be an ancestor for the whole of Superclass Tetrapoda.
The tetrapodomorphs had essentially the same anatomy as lungfishes.
Tetrapods comprise amphibians, reptiles, dinosaurs, birds, and
mammals and even snakes by descent, the groups that would go on
to dominate the land, and result in the appearance humans very,