Context: The superclass Tetrapoda (Ancient Greek s tetrapods, "four-footed"), or the tetrapods , comprises the first four-limbed vertebrates and their descendants, including the living and extinct amphibians, birds, mammals, reptiles and some ancient, exclusively aquatic creatures such as the Acanthostega. Tetrapods evolved from the lobe-finned fishes around 390 million years ago in the middle Devonian Period, with modern tetrapod groups having appeared by the late Devonian, 367.5 million years ago. The specific aquatic ancestors of the tetrapods, and the process by which land colonization occurred, remain unclear, and are areas of active research and debate among palaeontologists at present., Lungfish (also known as salamanderfish) are freshwater fish belonging to the subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton., Actinopterygii , or the ray-finned fishes, constitute a class or subclass of the bony fishes., Vertebrates comprise all species of animals within the subphylum Vertebrata (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 64,000 species described. Vertebrates include the jawless fish and the jawed vertebrates, which include the cartilaginous fish (sharks and rays) and the bony fish. , A fish is any member of a group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered obsolete or paraphyletic by excluding the tetrapods (i.e., the amphibians, reptiles, birds and mammals which all descended from within the same ancestry). Because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology. The traditional term pisces (also ichthyes) is considered a typological, but not a phylogenetic classification., A clade (from , "klados", "branch") is a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single "branch" on the "tree of life"., The Sarcopterygii or lobe-finned fish (from Greek  "sarx", flesh, and  "pteryx", fin)  sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek  "krossos", fringe)  constitute a clade (traditionally a class or subclass) of the bony fish, though a strict cladistic view includes the terrestrial vertebrates. The living sarcopterygians are the coelacanths and lungfish; additionally, all tetrapods are sarcopterygians or descendants of them., Osteichthyes / stiki.iz / , popularly referred to as the bony fish , is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue , as opposed to cartilage . The vast majority of fish are members of Osteichthyes , which is an extremely diverse and abundant group consisting of 45 orders , and over 435 families and 28,000 species . It is the largest class of vertebrates in existence today . The group Osteichthyes is divided into the ray - finned fish ( Actinopterygii ) and lobe - finned fish ( Sarcopterygii ) . The oldest known fossils of bony fish are about 420 million years ago , which are also transitional fossils , showing a tooth pattern that is in between the tooth rows of sharks and bony fishes . Osteichthyes can be compared to Euteleostomi . In paleontology , the terms are synonymous . In ichthyology , the difference is that Euteleostomi presents a cladistic view which includes the terrestrial tetrapods that evolved from lobe - finned fish , whereas on a traditional view , Osteichthyes includes only fishes and is therefore paraphyletic . However , recently - published phylogenetic trees treat the Osteichthyes as a clade ., Bone tissue, or osseous tissue, is the major structural and supportive connective tissue of the body. Bone tissue forms the rigid part of the bones that make up the skeleton., A bone is a rigid organ that constitutes part of the vertebrate skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions. , The coelacanths constitute a now rare order of fish that includes two extant species in the genus "Latimeria": the West Indian Ocean coelacanth primarily found near the Comoro Islands off the east coast of Africa ("Latimeria chalumnae") and the Indonesian coelacanth ("Latimeria menadoensis"). They follow the oldest known living lineage of Sarcopterygii (lobe-finned fish and tetrapods), which means they are more closely related to lungfish, reptiles and mammals than to the common ray-finned fishes. They are found along the coastlines of the Indian Ocean and Indonesia. Since there are only two species of coelacanth and both are threatened, it is the most endangered order of animals in the world. The West Indian Ocean coelacanth is a critically endangered species., Subject: osteichthyes, Relation: taxon_rank, Options: (A) branch (B) class (C) form (D) genus (E) group (F) order (G) phylum (H) species (I) subclass (J) superclass (K) variety
Output: superclass