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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).
Fish without scales usually evolve alternatives to the protection scales can provide, such as tough leathery skin or bony plates. Jawless fish (lampreys and hagfishes) have smooth skin without scales and without dermal bone. [59] Lampreys get some protection from a tough leathery skin.
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 ...
Thelodonts (nipple teeth) are a class of small, extinct jawless fishes with distinctive scales instead of large plates of armour. There is debate over whether these represent a monophyletic grouping, or disparate stem groups to the major lines of jawless and jawed fish. [19] Thelodonts are united by their characteristic "thelodont scales".
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. ... Scales wrapped around ...
Thelodonti (from Greek: "nipple teeth") [4] is a class of extinct Palaeozoic jawless fishes with distinctive scales instead of large plates of armor. There is much debate over whether the group represents a monophyletic grouping, or disparate stem groups to the major lines of jawless and jawed fish. Shielia taiti