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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).
Cyclostomi, often referred to as Cyclostomata / s ɪ k l oʊ ˈ s t ɒ m ə t ə /, is a group of vertebrates that comprises the living jawless fishes: the lampreys and hagfishes.Both groups have jawless mouths with horny epidermal structures that function as teeth called ceratodontes, and branchial arches that are internally positioned instead of external as in the related jawed fishes. [1]
Thelodonti ('feeble-teeth') are a group of small, extinct jawless fishes with distinctive scales instead of large plates of armour. There is much debate over whether the group of Palaeozoic fish known as the Thelodonti (formerly coelolepids [11]) represent a monophyletic grouping, or disparate stem groups to the major lines of jawless and jawed ...
A newfound fossil of a jawless fish is the oldest known vertebrate cranium preserved in 3D. The 455 million-year-old find could illuminate how vertebrate heads evolved.
Hagfish, of the class Myxini / m ɪ k ˈ s aɪ n aɪ / (also known as Hyperotreti) and order Myxiniformes / m ɪ k ˈ s ɪ n ɪ f ɔːr m iː z /, are eel-shaped jawless fish (occasionally called slime eels). Hagfish are the only known living animals that have a skull but no vertebral column, although they do have rudimentary vertebrae. [3]
Rhenanida ("Rhine fish") were flattened, ray-like, bottom-dwelling predators with large, upturned mouths that lived in marine environments. The rhenanids were once presumed to be the most primitive, or at least the closest to the ancestral placoderm, as their armour was made of unfused components—a mosaic of tubercles—as opposed to the ...
Arandaspis prionotolepis. This list of prehistoric jawless fish is an attempt to create a comprehensive listing of all genera from the fossil record that have ever been considered to be jawless fish, excluding purely vernacular terms.
The class Osteostraci (meaning "bony shells") is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known ...