One of my favorite words. I know what it means... do you?
2007-03-08 19:51:40 · 4 answers · asked by jennafingers 1 in Education & Reference ➔ Words & Wordplay
Agnatha (Greek, "no jaws") is a paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. Agnatha have existed since the Cambrian, and continue to live in modern times. There are two extant groups of jawless fish (sometimes called cyclostomes), the lampreys and the hagfish, with about 60 species between them. In addition to the absence of jaws, Agnatha are characterised by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches. The branchial arches supporting the gill pouches lie close to the body surface. There is a light sensitive pineal eye (homologous to the pineal gland in mammals). There is no identifiable stomach. Fertilization is external. The Agnatha are ectothermic, with a cartilaginous skeleton, and the heart contains 2 chambers.
Although they are superficially similar, many of these similarities are probably shared primitive characteristics of ancient vertebrates, and modern classifications tend to move the hagfish into a separate group (the Myxini or Hyperotreti), with the lampreys (Hyperoartii) being more closely related to the jawed fishes.
2007-03-08 20:01:01 · answer #1 · answered by fitforlife0032 2 · 0⤊ 0⤋
An Agnathan is a member of Phylum Chordata, subphylum Vertebrata, and superclass Agnatha, the jawless fishes. They are ancient, having survived with few anatomical changes since the Cambrian Explosion. Lampreys are a good example. Agnathans have a notochord but do not have paired fins. They are ectotherms with a two chambered heart and they have a skeleton made of cartilage. They are mostly parasitic, and enormously scarey looking!
2007-03-09 04:07:19 · answer #2 · answered by deleemar1 3 · 0⤊ 0⤋
any of the class Agnatha of primitive, jawless fishes that includes the lampreys and hagfishes (order Cyclostomata), as well as extinct groups.
Hagfishes are minor pests of commercial food fisheries of the North Atlantic, but because of their parasitic habit, lampreys have been a serious pest of food fisheries in the Great Lakes in North America, where they have reduced…
agnathan...
2007-03-09 04:01:59 · answer #3 · answered by Sumita T 3 · 0⤊ 0⤋
I can only find agnate. Related by common descent through a male.
Please let me know if there is another meaning....
2007-03-09 03:56:13 · answer #4 · answered by celianne 6 · 0⤊ 0⤋