Hagfish 32-V
CHORDATA
Craniata
 
 
Mouth of a hagfish (Myxine sp.)
[Public Domain]



Chapter Outline
  1. Description of Chordata
  2. Classification of Chordata
  3. Tunicata
  4. Cephalochordata
  5. Craniata

Tree



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"The Craniata, or craniates, include all animals having a skull (or cranium, hence their name), be it cartilaginous or bony. Craniates comprise all fishes - including such jawless fishes as hagfishes and lampreys - amphibians, reptiles, birds and mammals, including Man. The earliest known undisputed craniates are jawless fishes which lived 480 millions years ago. Their evolutionary history took place first in the sea, then in fresh waters. Some craniates, the tetrapods or four-legged vertebrates, became terrestrial and arose about 370 millions years ago from fish ancestors. Now, the majority of the craniate species are represented by one group of fish, the actinopterygians, and the tetrapods. Other craniate groups (jawless fishes, sharks and chimeras, the coelacanth, lungfishes) are considerably depauperate, by comparison with their past diversity.

The Craniata fall into two major clades, the Hyperotreti, or hagfishes, and the Vertebrata. Since the early nineteenth Century, and until recently, the hagfishes were regarded as the sister-group of lampreys (Hyperoartia). The two groups were gathered into the clade Cyclostomi. However, lampreys share with jawed vertebrates, or Gnathostomata, a large number of morphological and physiological characteristics that occur neither in hagfishes, nor in non-craniate chordates (cephalochordates and tunicates). There is, therefore, a rather broad consensus over the theory that hagfishes are the sister-group of the Vertebrata (lampreys and gnathostomes)." - [Craniata: Animals With Skulls. Philippe Janvier. The Tree of Life Web Project. http://tolweb.org/tree?group=Craniata&contgroup=Chordata. 1997.]

Other craniates (the vertebrates) will be discussed in following chapters. This page will focus on the hagfishes. There is only one order (Myxiniformes) and one family (Myxinidae) of hagfishes.

  • Hyperotreti
    • Myxiniformes - Hagfishes
  • Vertebrata (Ch. 33) - Fishes, Amphibians, Reptiles, Birds, Mammals

Hagfishes are found in "marine, temperate zones of the world, all oceans except the Red Sea, Arctic, and Southern oceans; only deep water in tropical areas. Jaws absent, no bones. Body naked, eel-like. No paired fins, no dorsal fin. Degenerate eyes. Laterally biting mouth bearing barbels. Teeth only on tongue plus one on 'palate'. Important predators (often scavengers) on invertebrates and others, e.g., netted fishes and discard. One of the most abundant groups of demersal fishes in many areas. Prey item for marine mammals and large predatory invertebrates. Only vertebrates with body fluids iso-osmotic with seawater. About 100 cm max length." - [Fishbase]

Organisms:

  • California Hagfish (Eptatretus stoutii) - EOL
  • Hagfish (Myxine sp.) - EOL
Resources:


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