| P number: | P549555 |
|---|---|
| Caption: | Monograptus, a Silurian graptolite. |
| Description: | Monograptus first evolved during the early Silurian (about 440 million years ago) and was amongst the last of the graptolites before they went into extinction in the early Devonian (about 390-415 million years ago). They are particularly common in the Silurian slates and shales of Wales. Monograptus was very common and very variable; some were straight and others were coiled, some had simple theacae but in others the thecae were hooked. The illustrated specimen has a slightly coiled initial part, but much of the rhabdosome is straight. The thecae are simple tubes arranged on one side of the organism. Graptolites are thin, often shiny, markings on rock surfaces that look like pencil marks (their name comes from the Greek meaning 'writing in the rocks'). They are the remains of intricate colonies, some of which accommodated up to 5,000 individual animals. The zooids lived in tube-like structures called thecae comprised of collagen. Whereas the cone-like dendroid graptolites were benthonic, graptoloids were planktonic. They first evolved in the Cambrian (about 520 million years ago) and they became extinct in the Carboniferous (about 350 million years ago). |
| Photographer: | Unknown |
| Copyright statement: | Unknown |
| Orientation: | Portrait |
| Size: | 578.72 KB; 811 x 1000 pixels; 69 x 85 mm (print at 300 DPI); 215 x 265 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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