| P number: | P550287 |
|---|---|
| Caption: | Emarginulina crassa, a gastropod with a slit. |
| Description: | Emarginulina is an archaeogastropod that may have evolved in Triassic times, but it is certainly known from the early Jurassic to modern times and is found all over the world. Emarginulina crassa is from the Pliocene deposits of south-eastern England, about 2-5 million years old. Emarginulina crassa superficially resembles Patella (limpets) found all round the coast of Britain. It has a conical shell with a pointed apex and ribs radiating out. An important feature for identifying this type of gastropod is the slit seen at the top of the illustration. It enabled water currents to leave the shell after washing waste away from the head. The slit retained its position with growth, so leaving a 'scar' down the front of the shell. Gastropods are molluscs with a muscular foot, eyes, tentacles, and a rasp-like feeding organ (a radula), although only the coiled or conical shell is fossilised. The earliest Cambrian species were marine, but gastropods now colonise fresh water and the land. Classification is based mainly on soft body parts, which are not fossilised, and although there is uncertainty, most fossils appear to fall into one of three groups: 1. Archaeogastropods which have two auricles in the heart, two gills and two kidneys. 2. Caenogastropods which have one gill, auricle and kidney and sometimes a siphon. 3. Pulmonates which have a lung. |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Landscape |
| Size: | 473.40 KB; 1001 x 799 pixels; 85 x 68 mm (print at 300 DPI); 265 x 211 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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