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17/03/2009 10:07:34
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P number: P549532
Caption: Spirifer, a Carboniferous brachiopod. Specimen GSD 3567.
Description: Spirifer is a brachiopod that evoved in the early Carboniferous (about 350 million years ago), rapidly spread throughout much of the world's seas and became extinct in the late Carboniferous (about 300 million years ago). Its pedicle (a fleshy stalk) extended through the small opening seen near the umbone at the top of the specimen, and was attached to the substrate. Spirifer has two convex shells. The pedicle valve (the one through which the pedicle once extended) is the larger one and it has a sulcus (a furrow) running down the centre, whereas the smaller brachial valve, at the front of the illustration, has a fold running down the centre. It is covered by numerous ribs radiating out from the umbo (the pointed 'beak' at the top of the illustrated specimen). Brachiopods have a very long history. The oldest species lived during the earliest Cambrian time (545 million years ago) although strange animals that look like worms, but with a brachiopod-like shells each end suggest they evolved during the late Precambrian. They were particularly commmon during the Palaeozoic times (248 to 545 million years ago), but today they are rather rare. These animals are almost entirely marine, although some live in brackish waters. They have a shell usually attached to a firm substrate like a rock, by a pedicle, a fleshy stalk that extends out of an opening in one of the valves (the pedicle valve). The two valves are hinged so that they can be opened to allow water and food particles to wash through. Calcareous supports for the internal organs are sometimes preserved in fossils.
Photographer: Unknown
Copyright statement: NERC
Orientation: Landscape
Size: 393.66 KB; 1000 x 750 pixels; 85 x 64 mm (print at 300 DPI); 265 x 198 mm (screen at 96 DPI);
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