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Early tetrapods probably had a three-chambered heart, as do modern amphibians and lepidosaurian and chelonian reptiles, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enters by separate atria, and is directed via a spiral valve to the appropriate vessel — aorta for oxygenated blood and pulmonary ...
This article contains a list of all of the classes and orders that are located in the Phylum Chordata. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it.
Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/toads, salamanders/newts and caecilians) — by the development of three extraembryonic membranes (amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage), thicker and keratinized ...
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.
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies ) that distinguish them from other taxa .
However, this group represents a paraphyletic grade of primitive stem-tetrapods and is not used by many modern researchers. Phylogenetic analysis has shown Ichthyostega is intermediate between other primitive stegocephalian stem-tetrapods. The evolutionary tree of early stegocephalians below follows the results of one such analysis performed by ...
Tetrapodomorpha (also known as Choanata [3]) is a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish.
The tetrapods evolved from the lobe-finned fishes about 395 million years ago in the Devonian. [23] 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.