Rajiformes
From Wikipedia, the free encyclopedia
| Rajiformes Fossil range: middle Eocene–Recent [1] |
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| Spotted eagle ray, Aetobatus narinari | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Superorder: | Batoidea |
| Order: | Rajiformes |
| Families | |
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Anacanthobatidae |
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Rajiformes is the order of true rays and skates, flat-bodied cartilaginous fishes related to sharks.
Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the body, and the gill slits on the underside. They have flattened, crushing teeth, and are generally carnivorous, although manta rays are filter feeders. Most species give birth to live young, although some lay eggs with a horny capsule ("mermaid's purse").[1]
[edit] Classification
There are several proposed classifications of fish in the superorder Batoidea. In some classifications the order Rajiformes is split into two or three orders, the additional orders being Myliobatiformes, containing the eagle rays and their relatives; Rhinobatiformes, containing the guitarfishes (which may be further split into Rhynchobatiformes, containing the shovelnosed guitarfishes, and Rhiniformes, the guitarfishes).
- Anacanthobatidae (smooth skates)
- Arhynchobatidae (softnose skates)
- Dasyatidae (stingrays). Named for the venomous spines along the tail; these contain a poison that causes pain and may cause symptoms such as nausea, vomiting, fever, chills, muscle cramps, tremors, paralysis, fainting, seizures, elevated heart rate, and decreased blood pressure (depending on the species). In addition, some species' toxins can be fatal to humans.
- Gymnuridae (butterfly rays)
- Hexatrygonidae (sixgill stingrays)
- Myliobatidae (eagle rays). The largest of rays, including the giant manta rays. Most eagle rays have one poison-carrying spine.
- Plesiobatidae (deepwater stingrays)
- Potamotrygonidae (river stingrays)
- Rajidae (hardnose skates)
- Rhinobatidae (guitarfishes). They have a body structure similar that of the sawfishes, but are not thought to be closely related.
- Urolophidae (Indo-Pacific round rays)
- Urotrygonidae (American round rays)
Fossil genera are:
- Rhombodontidae from the Maastrichtian stage of the Cretaceous period of Europe, Asia, Africa and the Americas[2].
[edit] References
- ^ a b "Rajiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2009 version. N.p.: FishBase, 2009.
- ^ http://www.elasmo.com/frameMe.html?file=genera/cretaceous/rhombodus.html&menu=bin/menu_genera-alt.html Rhombodus DAMES 1881 Extinct myliobatoid ray — Upper Cretaceous by Elasmo.com
- "Rajiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2006 version. N.p.: FishBase, 2006.
- Batoids: Sawfishes, Guitarfishes, Electric Rays, Skates, and Sting Rays
- J. D. McEachran, K. A. Dunn, T. Miyake (1996). "Interrelationships of the batoid fishes (Chondrichthyes: Batoidea)". In Interrelationships of Fishes, Academic Press.
- "Skate or Ray?". ReefQuest Centre for Shark Research. Accessed 20 March 2008.
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