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Vertebrates share these characteristics with other chordates. [4] Vertebrates are distinguished from all other animals, including other chordates, by multiple synapomorphies: namely the vertebral column, skull of bone or cartilage, large brain divided into 3 or more sections, a muscular heart with multiple chambers; an inner ear with ...
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.
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
Haeckel's Paleontological Tree of Vertebrates (c. 1879). The evolutionary history of species has been described as a "tree" with many branches arising from a single trunk. While Haeckel's tree is outdated, it illustrates clearly the principles that more complex and accurate modern reconstructions can obscure.
From about the 1940s to the 1990s, family trees based on embryological and morphological features placed brachiopods among or as a sister group to the deuterostomes. [63] [64] a super-phylum that includes chordates and echinoderms. [65] Closer examination has found difficulties in the grounds on which brachiopods were affiliated with ...
Despite their simple appearance and very different adult form, their close relationship to the vertebrates is certain. Both groups are chordates, as evidenced by the fact that during their mobile larval stage, tunicates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, post-anal tail, and an endostyle. They resemble a tadpole.
Below is a phylogenetic tree of the phylum Chordata. Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, †. Some groups in this tree (lancelets and tunicates) are invertebrates. The positions (relationships) of the lancelet, tunicate, and craniate clades are as reported.
Invertebrate chordates are close relatives to vertebrates. In particular, there has been discussion about how closely some extinct marine species, such as Pikaiidae, Palaeospondylus, Zhongxiniscus and Vetulicolia, might relate ancestrally to vertebrates. Invertebrate chordates are close relatives of vertebrates