Agnatha (/ ˈæɡnəθə, æɡˈneɪθə /; [3] from Ancient Greek ἀ- (a-) 'without' and γνάθος (gnáthos) 'jaws') or jawless fish is a paraphyletic infraphylum [4] of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws.

agnathan, (superclass Agnatha), any member of the group of primitive jawless fishes that includes the lampreys (order Petromyzoniformes), hagfishes (order Myxiniformes), and several extinct groups.

Agnatha species, or jawless fish, are said to be the earliest vertebrates ever recorded, that are believed to be present during the Paleozoic era. In fact, the evolution of fishis claimed to have begun with jawless fish.

2024年4月12日 · The Agnatha, meaning “without jaws,” is a superclass of jawless fish within the phylum Chordata and subphylum Vertebrata. It encompasses both living species, known as cyclostomes, and extinct species like conodonts and ostracoderms.

2025年3月22日 · The term “Agnatha” is derived from Greek, where “a” means without, and “gnathos” means jaw. Agnatha can be categorized into Class Ostracodermi and Cyclostomata.

Agnathan - Evolution, Classification, Jawless: Superclass Agnatha have fossils dating from the Ordovician Period, and are distinguishable from the other craniates by their lack of jaws. Living orders are Petromyzontiformes (lampreys) and Myxiniformes (hagfishes).

2022年12月27日 · Agnatha are a group of jawless fish with few living species. Get to know these animals with us before they leave Earth altogether.

Class Agnatha consists of an ancient group of animals similar to fish but with some very noticeable differences. The agnathans lack jaws and paired fins. Instead of jaws, they have a cyclostomic (circular) toothed mouth with which they bore into the side of a fish and suck the blood of their victim.

The Agnatha (the most primitive vertebrate-a jawless fish) possess the alternative and lectin pathways while cartilaginous fish are the first group in which the classical pathway appears following the emergence of immunoglobulins.

Agnatha (Greek, "no jaws"), often considered a superclass within the subphylum Vertebrata, comprises the jawless fish —the oldest known vertebrates. The two extant groups of jawless fish (sometimes called cyclostomes) are the lampreys and the hagfish.