Order Summary for Rajiformes
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Main Ref |
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Order |
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Rajiformes skates and rays |
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Class |
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Elasmobranchii |
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Sister Order |
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Torpediniformes 50 M years |
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Ref.. |
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First Fossil Record |
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early Tertiary |
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Occurs in |
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Marine |
Fresh |
Brackish |
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Remark |
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Gill openings ventral; anterior edge of the greatly enlarged pectoral fin attached to side of head, anterior to the gill openings; anal fin absent; eyes and spiracles on dorsal surface; anterior vertebrae fused to form a synarcual; suprascapulae of pectoral girdles joined dorsally over vertebral column and articulating with column of synarcual or fused with synarcual; nictitating membrane absent, cornea attached directly to skin around the eyes; body generally strongly depressed; jaws protrusible in most; teeth pavementlike; in most, water for breathing taken in chiefly through the spiracle rather than the mouth (except for those living off the bottom); most give birth to live young (some have eggs encased in a horny capsule); the snout may function as an electroreceptive organ (as may be true for all elasmobranchs). |
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Classetymology |
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Greek eulanein, elasmos = metal beaten out + Greek brangchia = gills. Ref. 45335. |
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Orderetymology |
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Latin, raja = ray + Latin, forma = shape (Ref. 45335). |
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Families |
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