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Order Summary for Squaliformes
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Main Ref |
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Order |
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Squaliformes sleeper and dogfish sharks |
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Class |
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Elasmobranchii |
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Sister Order |
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Squatiniformes 155 M years |
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Ref. |
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First Fossil Record |
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late Jurassic |
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Occurs in |
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Marine |
Fresh |
Brackish |
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Remark |
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Two dorsal fins, with or without spines; anal fin absent; five gill slits; spiracles present; nictitating lower eyelid absent. Many species are known from deep water. |
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Class etymology |
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Greek eulanein, elasmos = metal beaten out + Greek brangchia = gills. Ref. 45335. |
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Order etymology |
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Latin, squalus, squalidus = weak, pale, with rough skin + Latin, forma = shape (Ref. 45335). |
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Families |
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