| P number: | P550269 |
|---|---|
| Caption: | Sternotaxis plana, a fossil echinoid. |
| Description: | Sternotaxis plana is a biostratigraphically useful species; its geological range is short and it makes a good zone fossil. It is particularly useful for correlating geographically separate exposures of the late Cretaceous Chalk in southern England. It is found in the Turonian part of the Chalk, which accumulated about 90 million years ago. Sternotaxis plana has a high and inflated test and although it is a heart-shaped echinoid, the frontal furrow is shallow and not strongly emphasised. The ambulacral plates are marked out by the double rows of pores. Echinoids (sea urchins) have lived in marine habitats since the Ordovician times, about 450 million years ago. They still live today, inhabiting many shallow, near shore seas around the world. As fossil echinoids resemble living species, we have an idea how they must have lived. They had spines which are used for protection. Some species protected themselves from carnivores by having poison-tipped spines while others had large, unpalatable solid spines. Echinoids burrowed into the sand or crawled over the sea floor on their tubed feet, which extended from the paired pores on the star-like or petal-like areas (the ambulacra). They grazed and scavenging algae and plants or ate small particles in the sandy substrate. |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Landscape |
| Size: | 427.36 KB; 1000 x 954 pixels; 85 x 81 mm (print at 300 DPI); 265 x 252 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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