Sarcopterygii

Lobe-finned fishes Temporal range: Late Silurian–Present, 425–0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N
From top to bottom and left to right, examples of sarcopterygians: Guiyu oneiros, West Indian Ocean coelacanth, Australian lungfish and the tetrapodomorph Panderichthys rhombolepis.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Superclass:	Osteichthyes
Clade:	Sarcopterygii Romer, 1955
Subgroups
†Megamastax ?†"Psarolepids" Guiyu Sparalepis Psarolepis Achoania Actinistia – coelacanths & relatives †Onychodontiformes Rhipidistia Dipnomorpha – lungfish & relatives Tetrapodomorpha – four-limbed vertebrates & relatives

Sarcopterygii (/ˌsɑːrkɒptəˈrɪdʒi.aɪ/; from Ancient Greek σάρξ (sárx) 'flesh' and πτέρυξ (ptérux) 'wing, fin') — sometimes considered synonymous with Crossopterygii (from Ancient Greek κροσσός (krossós) 'fringe') — is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. These vertebrates are characterised by prominent muscular limb buds (lobes) within their fins, which are supported by articulated appendicular skeletons. This is in contrast to the other clade of bony fish, the Actinopterygii, which have only skin-covered bony spines supporting the fins.

The tetrapods, a mostly terrestrial superclass of vertebrates, are now recognized as having evolved from sarcopterygian ancestors and are most closely related to lungfishes. Their paired pectoral and pelvic fins evolved into limbs, and their foregut diverticulum eventually evolved into air-breathing lungs. Cladistically, this would make the tetrapods a subgroup within Sarcopterygii and thus sarcopterygians themselves. As a result, the phrase "lobe-finned fish" normally refers to not the entire clade but only aquatic members that are not tetrapods, i.e. a paraphyletic group.

Non-tetrapod sarcopterygians were once the dominant predators of freshwater ecosystems during the Carboniferous and Permian periods, but suffered significant decline after the Great Dying. The only known extant non-tetrapod sarcopterygians are the two species of coelacanths and six species of lungfishes.