Agnatha
Sign in to saveAgnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both living (cyclostomes such as hagfishes and lampreys) and extinct clades (e.g. conodonts and cephalaspidomorphs, among others). They are sister to vertebrates with jaws known as gnathostomes, who evolved from jawless ancestors during the early Silurian by developing folding articulations in the first pairs of gill arches.
AI overview
Agnatha, also called jawless fish, is a group of vertebrate animals that lack jaws, including both living species like hagfishes and lampreys as well as many extinct ones. This group matters because it represents an early branch in vertebrate evolution—all modern jawed fish and other jawed vertebrates evolved from jawless ancestors like these when they developed hinged structures from their gill arches during the early Silurian period.
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Species
jawless fish
Infraphylum
- PhylumChordata
Habitatmarine, brackish, freshwater
via
Article
10 sectionsContents
- Metabolism
- Morphology
- Body covering
- Appendages
- Reproduction
- Evolution
- Classification
- Phylogeny
- See also
- References
Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both living (cyclostomes such as hagfishes and lampreys) and extinct clades (e.g. conodonts and cephalaspidomorphs, among others). They are sister to vertebrates with jaws known as gnathostomes, who evolved from jawless ancestors during the early Silurian by developing folding articulations in the first pairs of gill arches.
Molecular data, both from rRNA and from mtDNA as well as embryological data, strongly supports the hypothesis that both groups of living agnathans, hagfishes and lampreys, are more closely related to each other than to jawed fish, forming the superclass Cyclostomi.