Agnatha

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.

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.

AI-generated from the Wikipedia summary — may contain errors.

Species

jawless fish

Infraphylum

PhylumChordata

Habitatmarine, brackish, freshwater

via

Wikidata facts

Image: Lampetra fluviatilis.jpg

Show 3 more facts

taxon common name: 無頷總綱
taxon name: Agnatha
start time: 535000000-

Sources (2)

via Wikidata · CC0

~17 min read

Article

10 sections

Contents

Metabolism
Morphology
Body covering
Appendages
Reproduction
Evolution
Classification
Phylogeny
See also
References

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.