| P number: | P550277 |
|---|---|
| Caption: | Pseudodiadema, a fossil echinoid. |
| Description: | Pseudodiadema evolved very early in the Jurassic (Hettangian) about 205 million years ago and is very long ranging as it did not become extinct until the mid-Cretaceous times (Aptian) 115 million years ago. It is geographically widespread, being found in Europe, North Africa and India. Pseudodiadema is a regular echinoid, the anus being situated at the top of the domed test. The large mouth is situated in the central part of the underside and bears several gill slits. Each of the plates that comprise the test has a large tubercle and several small tubercles that radiate out from the centre with five-fold symmetry. The ambulacra, which are picked out by a series of pores, have smaller tubercles. 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: | 524.31 KB; 1000 x 984 pixels; 85 x 83 mm (print at 300 DPI); 265 x 260 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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