Craniate

A craniate is a member of Craniata (sometimes Craniota), a proposed clade of chordate animals that contains the Myxini (hagfish), Petromyzontida (including lampreys), and Gnathostomata (jawed vertebrates) as living representatives. As the name suggests, craniates are animals with a (hard bone or cartilage) skull in phylum Chordata.

Characteristics

In the simplest sense, craniates are chordates with 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.

In addition to distinct crania (sing. cranium), craniates possess many derived characteristics, which have allowed for more complexity to follow. Molecular-genetic analysis of craniates reveals that, compared to less complex animals, they developed duplicate sets of many gene families that are involved in cell signaling, transcription, and morphogenesis (see homeobox).