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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).
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]
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]
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.
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.
Jawless fish inhabit both fresh and salt water environments. Some are anadromous, moving between both fresh and salt water habitats. Extant jawless fish are either lamprey or hagfish. Juvenile lamprey feed by sucking up mud containing micro-organisms and organic debris. The lamprey has well-developed eyes, while the hagfish has only primitive ...
Jawless fish belong to the superclass Agnatha in the phylum Chordata, subphylum Vertebrata. Agnatha means 'un-jawed, without jaws' (from Ancient Greek). [11] It excludes all vertebrates with jaws, known as gnathostomes. Although a minor element of modern marine fauna, jawless fish were prominent among the early fish in the early Paleozoic.
Like most fish that live on the bottom of the ocean, the Atlantic Hagfish’s body color on the dorsal side varies depending on the color of the bottom of the ocean. The most common colors, are brown, reddish or purplish, brown, or grey, as for the ventral side the color will be paler.