Craniate
| Craniata Temporal range: Early Cambrian - Recent |
|
|---|---|
 |
|
| A Pacific hagfish, an example of a craniate | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: |
Craniata Lankester, 1877 |
| Included groups | |
|
|
| Synonyms | |
|
|
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage. Included in the clade are the vertebrates, and non-vertebrate chordates with skulls. Living representatives are the Myxini (hagfishes), Hyperoartia (including lampreys), and the much more numerous Gnathostomata (jawed vertebrates).
The clade was conceived largely on the basis of the Hyperoartia (lampreys and kin) being more closely related to the Gnathostomata (jawed vertebrates) than the Myxini (hagfishes); this suggested that the skull is more ancient feature than the vertebral column, and that the Myxini were descended from a more ancient lineage than the vertebrates. However recent studies using molecular phylogenetics has contradicted this view, with evidence that the Cyclostomata (Hyperoartia and Myxini) is monophyletic; this suggests that the Myxini are degenerate vertebrates, and therefore the vertebrates and craniates are cladistically equivalent, at least for the living representatives.
In the simplest sense, craniates are chordates with well defined heads, thus excluding members of the chordate subphyla Tunicata (tunicates) and Cephalochordata (lancelets), but including Myxini, which have cartilaginous skulls and tooth-like structures composed of keratin. Craniata also includes all lampreys and armored jawless fishes, armoured fish, sharks, skates, and rays, and teleostomians: spiny sharks, bony fish, lissamphibians, temnospondyls and protoreptiles, sauropsids and mammals. The craniate head consists of a brain, sense organs, including eyes, and a skull.
...
Wikipedia