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The barndoor skate, ''Dipturus laevis'', is a species of marine cartilaginous fish in the skate family (family Rajidae) of the order Rajiformes. It is native to the northwestern Atlantic Ocean, and is found from the Grand Banks of Newfoundland and the southern side of the Gulf of St. Lawrence south to North Carolina. The fish is one of the largest skates found in the North Atlantic Ocean, reaching lengths of up to . It is carnivorous, feeding on invertebrates and other fish found near the sea floor. After peaking in the 1950s, the population of the barndoor skate dramatically declined in the 1960s and early 1970s as a result of overfishing. In 2003 it was listed as endangered by the World Conservation Union. Barndoor populations have increased substantially since 1990. In most cases, the barndoor skate is not intentionally harvested by the commercial fishing industry—it is usually considered by-catch in the trawling nets used to target other species of fish. ==Description== The barndoor skate is a flat-bodied fish with a large, disk-like body with sharply angled corners and a pointed snout. Its pectoral fins have evolved into broad, flat, wing-like appendages used to propel the fish through the water. These fins have a concave front edge with rounded posterior corners. Like sharks, it has a boneless skeleton made of cartilage, a tough, elastic substance composed of collagenous and/or elastic fibers, cells, and a firm, gel-like substance called the matrix. It has slot-like body openings called gill slits on the underside of the body beneath the pectoral fins that lead from the gills. The dorsal fins are close together and far removed from the tail. It has two eyes on its dorsal surface, located approximately apart.〔 The fish's upper surface is brown to reddish brown with many scattered darker spots, lighter streaks, and reticulations. The center of each pectoral fin is marked with an oval spot or blotch. The lower surface is light, white to grey, blotched irregularly with gray spots.〔 The barndoor skate is unique from other species of skate in its having a straight line that begins at the snout and ends at the anterior margin of the outer corner of the disk, but stopping short of the disk.〔 The barndoor skate is one of the largest skates found in the North Atlantic Ocean.〔 It can reach lengths of up to and can weigh up to . There have been unconfirmed reports of individuals reaching lengths of .〔 A barndoor skate weighs an average of .〔 The tail is moderately short and does not have large thorn-like structures called dermal denticles that are normally found on skates. This lack of denticles distinguishes it from all but two species of skates that are found in the western Atlantic.〔 Larger individuals do have three rows of smaller denticles on the tail, and mature females also possess denticles on the head and shoulders, and along the dorsal midbelt of the disk and tail. Denticles are completely absent on small individuals.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「barndoor skate」の詳細全文を読む スポンサード リンク
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