Agnatha

Thesaurus

Noun

Agnatha - superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys; hagfishes; some extinct formssuperclass AgnathaCraniata, subphylum Craniata, subphylum Vertebrata, Vertebrata - fishes; amphibians; reptiles; birds; mammalsagnathan, jawless fish, jawless vertebrate - eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct formsorder Ostracodermi, Ostracodermi - extinct group of armored jawless vertebrates; taxonomy is not clearAnaspida, order Anaspida - extinct order of jawless vertebratesConodonta, Conodontophorida, order Conodonta, order Conodontophorida - extinct order of primitive vertebrates; the precise taxonomy is not clear; in some classifications considered a separate phylumCyclostomata, order Cyclostomata - primitive jawless aquatic vertebrate: lampreys; hagfishesclass - (biology) a taxonomic group containing one or more orders

Agnatha

[′ag·nə′thə] (vertebrate zoology) The most primitive class of vertebrates, characterized by the lack of true jaws.

Agnatha

a superclass of lower vertebrate animals. Agnatha are distinguished from all the remaining vertebrates, the Gnathostomata, by the absence of real jaws, and, in the ones living today, by the absence of paired extremities, as well as by the presence of an unpaired nostril. Agnatha are also called Marsipobranchia, because their gills look like pouches. The branchiate skeleton is located outside the pouches and has the appearance of a complete lattice (and not broken gill arches, as in fish) or is fused with the external shell. Agnatha is the most ancient group of vertebrates, widely distributed in the Silurian and Devonian periods. Fossil Agnatha (Ostracodermi) had a well-developed external and partially ossified internal skeleton. Their remains are the leading fossils for the Silurian and Devonian periods.

Of contemporary fauna, only representatives of the class Cyclostomata—the lampreys and hagfish—remain of the Agnatha.

REFERENCES

Berg, L. S. Sistema ryb. Moscow-Leningrad, 1940.
Osnovy paleontologii: Bescheliustnye, ryby. Moscow, 1964.

Agnatha

aquatic, jawless, fish-like vertebrates characterized by fewer than two pairs of limbs (fins). The group is often given the status of a subphylum to separate it from other vertebrates with jaws which are included in the subphylum Gnathostomata. The Agnatha includes lampreys, hagfish, and the fossil OSTRACODERMI.

Agnatha

Related to Agnatha: Osteichthyes

noun

Synonyms for Agnatha

noun superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys

Synonyms

superclass Agnatha

Related Words

Craniata
subphylum Craniata
subphylum Vertebrata
Vertebrata
agnathan
jawless fish
jawless vertebrate
order Ostracodermi
Ostracodermi
Anaspida
order Anaspida
Conodonta
Conodontophorida
order Conodonta
order Conodontophorida
Cyclostomata
order Cyclostomata
class