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Gnathostomata is traditionally a infraphylum, broken into three top-level groupings: Chondrichthyes, or the cartilaginous fish; Placodermi, an extinct grade of armored fish; and Teleostomi, which includes the familiar classes of bony fish, birds, mammals, reptiles, and amphibians. Some classification systems have used the term Amphirhina.
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).
Entelognathus, a placoderm incertae sedis that combines features of primitive arthrodires with jaw anatomy otherwise only seen in bony fish and tetrapods. Qilinyu, a close relative of Entelognathus that further links Entelognathus as a transitional form between placoderms and other stem-gnathostomes and crown-group gnathostomes.
Articles related to the Gnathostomata, the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates.
The agnathans as a whole are paraphyletic, [13] because most extinct agnathans belong to the stem group of the gnathostomes, the jawed fish that evolved from them. [14] [15] Molecular data, both from rRNA [16] and from mtDNA [17] strongly supports the theory that living agnathans, known as cyclostomes, are monophyletic. [18]
Infraphylum Gnathostomata (jawed vertebrates) Class Placodermi † (armoured fish) Class Chondrichthyes (cartilaginous fish) Class Acanthodii † (spiny sharks) Superclass Osteichthyes (bony fish) Class Actinopterygii (ray-finned fish) Subclass Chondrostei. Order Acipenseriformes (sturgeons and paddlefishes) Order Polypteriformes (reedfishes ...
The Gnathostomata are a superorder of sea urchins, including the familiar sand dollars. Gnathostomatans are irregular in shape, but unlike other irregular sea urchins, possess a feeding lantern. The mouth is located in the centre of the lower surface, as it is in most other sea urchins, but the anus is found to one side of the upper surface ...
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage.Living representatives are the Myxini (hagfishes), Hyperoartia (including lampreys), and the much more numerous Gnathostomata (jawed vertebrates).