| P number: | P550292 |
|---|---|
| Caption: | Helix nemoralis, a Pleistocene pulmonate gastropod. |
| Description: | The genus Helix is a land snail, a pulmonate gastropod that has a kind of lung. It first evolved during Miocene times (between 5 and 25 million years ago). Helix nemoralis, the illustrated specimen, lived during the Pleistocene times (the last two million years ago) in Cambridgeshire. It was active in cool, wet periods, but sheltered in the damp soil during warmer and drier times. Helix nemoralis has a globose shell made of four whorls. The shell is thin and apart from fine growth lines, externally smooth. Fossils do not usually show signs of the original coloration, but the illustrated species is too young to be fully fossilised (in other words, the original shell has not yet been replaced by other minerals) and orange stripes can still be seen. 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: | 339.86 KB; 1000 x 839 pixels; 85 x 71 mm (print at 300 DPI); 265 x 222 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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