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They had a tail fin but lacked the paired (pectoral and pelvic) fins of more advanced fish. Brain divided into three parts (further division created distinct regions based on function). The pineal gland of the brain penetrates to the level of the skin on the head, making it seem like a third eye. They evolved the first erythrocytes and ...
The evolution of fishes took place over a timeline which spans the Cambrian to the Cenozoic, including during that time in particular the Devonian, which has been dubbed the "age of fishes" for the many changes during that period. The Late Devonian extinctions played a crucial role in shaping the evolution of fish, or vertebrates in general. [1]
The bony fish evolved into two separate groups: the Actinopterygii (or ray-finned fish) and Sarcopterygii (which includes the lobe-finned fish). During the Devonian period a great increase in fish variety occurred, especially among the ostracoderms and placoderms, and also among the lobe-finned fish and early sharks.
The earliest known tracks on land named the Zachelmie trackways which are possibly related to icthyostegalians. [80] 375 Ma Tiktaalik, a lobe-finned fish with some anatomical features similar to early tetrapods. It has been suggested to be a transitional species between fish and tetrapods. [81] 365 Ma
Sarcopterygii (/ ˌ s ɑːr k ɒ p t ə ˈ r ɪ dʒ i. 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 ...
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez; from Ancient Greek ὀστέον (ostéon) 'bone' and ἰχθύς (ikhthús) 'fish'), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue.
Bony fish can be further divided into those with lobe fins and those with ray fins. Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. [16] Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extension an early ancestor of humans was a lobe-finned fish.
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.