Jawless Fishes

Agnatha (IPA: /ˈæɡnəθə, æɡˈneɪθə/) is an infraphylum of jawless fish (IPA: /ˈdʒɔːləs fɪʃ/) in the phylum Chordata, subphylum Vertebrata, consisting of both present and extinct species. Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes.


All aquatic vertebrates with gills and fins are traditionally classified as "fishes". However, because it includes a wide variety of creatures, some of which lack jaws or skeletal skeletons, this definition is solely typological and not necessarily phylogenetic (based on the evolutionary history and relationships between species). In addition to the oceans, practically every body of water has fish. The diversity of fish was higher in the past than it is now, with many lineages going extinct throughout time and leaving only fossil remnants and traces to guide us. Currently, we know over 33,000 species of fish.

List of Jawless Fishes

Uncertain

Recent taxonomic investigations clearly occur among Haikouichthys, Palaeospondylus, Metaspriggina, and probably Tullimonstrum, despite the fact that some scientists still believe that the living agnathans are only superficially related and that many of these similarities are likely shared basal traits with ancient vertebrates.


Conodonts (Conodonta)

The Conodonts (Greek kōnos, "cone", + odont, "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. Some conodonts' "teeth" have been theorized to be filter-feeding devices that draw plankton from the water and send it down the throat. A "grasping and crushing array" has been used to describe some others. Some condoning pieces have wear patterns that imply they formerly served as teeth. Food and other materials may have caused these wear patterns to form.


Lampreys (Petromyzontiformes)

The Lampreys (IPA: /ˈlæmpreɪz/; sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes ([IPA: /ˌpɛtroʊmɪˈzɒntɪfɔːrmiːz/]), placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth. The most well-known species of parasitic carnivorous lampreys subsist by digging into the flesh of other fish and sucking their blood, although there are only 18 species of lampreys that live this micropredatory lifestyle. Nine of the 20 carnivorous species breed in both freshwater and saltwater, nine dwell solely in freshwater, and one coexists exclusively with Malzeno or Gaismagorm. Some of these species also have populations in saltwater.


Hagfish (Myxini)

Hagfish, of the class Myxini (IPA: /mɪkˈsaɪnaɪ/; also known as Hyperotreti) and order Myxiniformes [/mɪkˈsɪnɪfɔːrmiːz/], are eel-shaped, slime-producing marine fish (occasionally called slime eels). They are the only known living animals that have a skull but no vertebral column, although hagfish do have rudimentary vertebrae.


Pteraspidomorphs (Pteraspidomorphi)

The Pteraspidomorph (Pteraspidomorphi) is an extinct class of early jawless fish. They have long been regarded as closely related or even ancestral to jawed vertebrates, but the few characteristics they share with the latter are now considered as basal traits for all vertebrates. Pteraspidomorphs are characterized by their massive dermal head armour having large, median, ventral and dorsal plates or shields.


Thelodonts (Thelodontomorphi)

The Thelodonti (from Greek: "nipple teeth") is a class of extinct Palaeozoic jawless fishes with distinctive scales instead of large plates of armor. Thelodonts are united in possession of "thelodont scales". This defining character is not necessarily a result of shared ancestry, as it may have been evolved independently by different groups.


Anaspidomorphs (Anaspidomorphi)

The Anaspidomorphi (anaspidomorphs) is an extinct superclass of jawless fish. Anaspidomorphs were small marine agnathans that lacked a heavy bony shield and paired fins, but were distinctively hypocercal.


Cephalaspidomorphs (Cephalaspidomorphi)

The jawless fish family known as cephalaspidomorphs is named after the osteostracan Cephalaspis. The majority of biologists believe this taxon to be extinct, but because lampreys were originally believed to be linked to cephalaspids, the word is occasionally used to describe them. The known range of the group would be extended from the Silurian and Devonian eras to the present day if lampreys are included.

Foreign Languages

Lampreys (Petromyzontiformes)


Hagfish (Myxini)