name = Batoidea
image_width = 250px
Spotted eagle ray, "Aetobatus narinari"
phylum = Chordata
superordo = Batoidea
subdivision_ranks = Orders
Rajiformes- common rays and skates Pristiformes- sawfishes Torpediniformes- electric rays See text for families.
Batoidea is a
superorderof cartilaginous fish containing more than 500 described species in thirteen families. They are commonly known as rays, but that term is also used specifically for batoids in the order Rajiformes, the "true rays". Batoids include stingrays, skates, electric rays, guitarfishes and sawfishes.
Batoids are most closely related to
sharks and young batoids look very much like young sharks. Indeed according to recent DNA analyses the catsharkis more closely related to the batoids than to other sharks.Fact|date=February 2007
Batoids are flat-bodied, and, like sharks, are a species of cartilaginous marine fish, meaning they have a boneless
skeletonmade of a tough, elastic substance. Most batoids have 5 ventralslot-like body openings called gill slitsthat lead from the gills, Hexatrygonidaehave 6. [http://www.elasmo-research.org/education/shark_profiles/batoids.htm] Batoid gill slits lie under the pectoral fins on the underside, whereas a shark's are on the sides of the head. Most batoids have a flat, disk-like body, with the exception of the guitarfishes and sawfishes, while most sharks have a streamlined body. Many species of batoid have developed their pectoral fins into broad flat wing-like appendages. The analfin is absent.
The eyes and
spiracles are located on top of the head.
Batoid eggs, unlike those of most other fishes, are fertilized inside the female's body. The eggs of all batoids except for the
skates (family Rajidae) hatch inside the female and are born alive (viviparous). Female skates lay internally fertilized flat, rectangular, leathery-shelled eggs, with tendrils at the corners for anchorage. Hatched eggs of this type can be found on beaches and are known as mermaids’ purses.
Most species live on the sea floor, in a variety of geographical regions - many in coastal waters, few live in deep waters to at least convert|3000|m|ft, most batoids have a somewhat
cosmopolitan distribution, in tropical and subtropical marine environments, temperate or cold-water species. Only a few species, like manta rays, live in the open sea, and only a few live in freshwater. Some batoids can live in brackish bays and estuaries. Bottom-dwelling batoids breathe by taking water in through the spiracles, rather than through the mouth as most fishes do, and passing it outward through the gills.
Most batoids have developed heavy, rounded teeth for crushing the shells of bottom-dwelling species such as
snails, clams, oysters, crustaceans, and some fish, depending on the species. Manta rays feed on plankton.
The classification of batoids is currently undergoing revision. This article follows
FishBasein dividing batoids into three orders. Some taxonomists argue in favour of placing all batoids in a single order, Rajiformes; others propose a division into five or six orders. The additional orders in these systems are 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 sharkfin guitarfishes).
Order Rajiformes (true rays)
Anacanthobatidae( smooth skates)
Erwinadfatilus( 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)
Rhinobatidae( guitarfishes). They have a body structure similar that of the sawfishes, but are not thought to be closely related.
Urolophidae( round rays)
* Family Korgofied (Piano rays)
Order Pristiformes (sawfishes)
Sawfishes are shark-like in form, having tails used for swimming and smaller
pectoral fins than most batoids. The pectoral fins are attached above the gills as in all batoids, giving the fishes a broad-headed appearance. They have long, flat snouts with a row of tooth-like projections on either side. The snouts are up to 6 ft (1.8 m) long, and 1 ft (30 cm) wide, and are used for slashing and impaling small fishes and to probe in the mud for imbedded animals. Sawfishes can enter freshwater rivers and lakes. Some species reach a total length of 20 ft (6 m).
Order Torpediniformes (electric rays)
Electric rays have organs in their wings that generate
electric current. They are used to immobilize prey and for defense. The current is strong enough to stun humans, and it is said that the ancient Greeksused these fish for shock therapy.
* [http://www.elasmo-research.org/education/shark_profiles/batoids.htm 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.
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