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| Where does the name Belemnite come from ? | ||
| Pronounced 'BEL-EM-NIGHT', the name is believed to have originally been derived from the Greek language word 'belemnon', which is today translated as meaning the name of an object that is shaped like a dart or a javelin. | ||
| When were they alive on Earth ? | ||
| The Belemnites were present on the Earth for a period spanning over 140 million years. They first appeared on Earth some 208 million years ago, during the Carboniferous period. It is currently believed that they evolved from the same ancestors as the Ammonites. The Belemnites became extinct about the same time that the majority of the dinosaurs disappeared. This is believed to be at the end of the Cretaceous Period, some 65 million years ago, known in paleontology as the time of the K-T mass-extinction. | ||
| What did they look like in real life ? | ||
| Belemnites were marine animals that belonged to
the classification of Phylum Mollusca and to the Class Cephalopoda.
Today you would find their still living relatives, the squid and cuttlefish, within the
same classification. The similarities to their modern day relatives include ink sacs and
the presence of ten tentacles however, the design of their tentacles also forms a
difference between them; on the modern squid they have suckers in order to grab prey,
whereas Belemnite tentacles had hooks.
Belemnites were believed to be efficient carnivores that caught small fish and marine animals with their tentacles, and then ate them with their beak-like jaws. It is believed that Belemnites were built for speed and that they probably lived in shoals. Fossil evidence has shown that they formed a major part of the diet of Ichthyosaurs. |
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What do the fossils look like ? |
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One of the reasons for their presence in the fossil record is that Belemnites had a hard internal skeleton, which is well preserved in the stratigraphic record. The following image shows a section of a Belemnite fossil that was found inside a limestone nodule recovered from the Belemnite Marl bed under Stonebarrow Hill.
The complete Belemnite 'shell' consists of three parts; the guard, the alveolus and the pro-ostracum. The fossil remains most normally found are the part of the shell that was originally located in the tail of the Belemnite. This part is usually referred to as the guard (the correct name is the rostrum, the plural of which is rostra). This guard is elongated and bullet-shaped, cylindrical and either pointed or rounded at one end. It is this end that points towards the rear of the Belemnite. The hollow chamber at the front of the guard is called the alveolus.
Inside this chambered space went the rear part of the body of the Belemnite, called the phragmocone. Being made of soft organic material, this part of the Belemnite fossilised less easily than the guard and is thus rarely found. Fortunately I found this small crushed example on the foreshore under Stonebarrow Hill:
The pro-ostracum appears as a quill like extension to the guard over part of the phragmacone. This is very rarely found in the fossil record. In most Belemnite fossils, the guard is made from fibrous calcite, which grows inwards towards the center, very similar to the formation of the 'beef' in the Shales with Beef bed.
Sometimes though, the calcite grows in concentric patterns, like tree growth rings. In this instance the paler layers are composed of nearly pure calcite, whereas the darker layers are often discoloured due to the presence of organic matter or minerals. [ When I have collected and photographed a Belemnite fossil showing a good example of the calcite structure, I will replace the above image ] The Gottingen University website has a photo of a complete Belemnite fossil. |
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Are Belemnites all the same shape ? |
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The answer to this is a very loud NO. The shape of Belemnites is varied and the cross section can be described in terms of quadrate, pyriform, circular, elliptical depressed and elliptical compressed, as well as several other 'designs'. The apex (the pointed end), can be described as attenuate, very acute, acute, moderately acute, very obtuse and mucronate. Here are some sketches showing some of the possible shapes:
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Are there variations between the genera ? |
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Actinocamax sp - - Alveolus of guard either conical or broadly funnel shaped, and either in contact with the protoconch only or surrounding only the apical part of the phragmacone. Front part of guard often fragile and foliaceous owing to imperfect calcification. Atractites sp - The guard is long, with a very deep alveolus, such that the main part of it forms a sheath over the very long phragmacone. Belemnitella sp - - Similar to Belemnite but with a straight fissure in the guard on the ventral side of the wall of the alveolus. Distinct vascular impressions on the under surface of the guard. Cretaceous: Upper Greensand to Chalk 21+7 Belemnites sp Acoeli - - Without dorsal or ventral grooves. Belemnites sp Gastrocoeli - Distinct ventral groove. Belemnoteuthis sp - - Shell consisting of Belemnite type phragmacone, a horny dorsal pen with obscure lateral bands and a thin fibrous guard with two diverging ridges on the dorsal side. Middle Oolite: Oxford Clay. Mucrohibolites sp - -. Phragmoteuthis sp - - Trias. Pseudoduvalia sp - -. Xiphoteuthis sp - - Guard narrow and cylindrical, containing very long, deep-chambered, narrow phragmacone. Pro-ostracum greatly developed (12 inches), very narrow at base, widening out anteriorly and terminating in a pointed apex. Lias. |
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What types of Belemnites can be found around the Charmouth area ? |
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The various genera [families] of Belemnites found in the Charmouth/Lyme Regis/Seatown area include: Belemnites longissimus, Belemnites elongatus, Belemnites clavatus, Belemnites angeloteuthis, Belemnites bairstowius, Belemnites hastites, Belemnites passaloteuthis, Belemnites pseudohastites and Belemnites pollex. Many of the Belemnite genera have formal names ending in '-teuthis', which is the Greek word for 'squid'. |
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Were they always known as Belemnites ? |
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In several of the local dialects, Belemnites are known to have been called "thunderbolts", "thunder-arrows", or sometimes even "Devil's Fingers" or "St. Peter's Fingers". It was believed that during thunderstorms, the thunderbolts are hurled to the Earth along with the lightning strike. A person being struck by lightning was therefore thought to have been killed by a thunderbolt. Thunderbolts were supposed to only found in places where lightning had struck the ground. Local folklore comments that stomach-aches can be cured by scraping off and then swallowing a little of the 'thunderbolt'. |
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How can you find Belemnites ? |
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A walk along the shoreline from Seatown at low tide, on the eastern side of Golden Cap, allowed this photo opportunity:
It shows the surface of the Belemnite Marl bed which is exposed at this point. Being regularly washed by wave action at every high tide, the softer marl is soon eroded away from the harder calcite fossils. This results in the exposure of the calcite Belemnite guards. Closer inspection reveals several types of Belemnite embedded within the surface of the marl. With care the fossils can be extracted, however, the same wave action that exposes them, often results in the guards being broken. |
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How are the different types of Belemnite fossil classified ? |
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Is there a Belemnite database ? |
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Although far from complete, there is a list available of those Belemnites that I have been able to find information on, and it can be found here, although you should note that it is still being worked on. Additional information always welcomed! |
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Where else can I see Belenite fossil images ? |
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My Belemnite collection photographs |
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I have recently collected over 100 belemnite rostra from the Black Ven Marl, Belemnite Marl and Green Ammonite Beds of the Lower Jurassic. Unfortunately there is a limited amount of information as to the identification of different types of Belemnite. If you can help, please let me know, via e-mail or my guest book. As I photograph more of the collection, I will upload the images. The dimensions quoted below are the maximum measured on the specimen. With the exception of fossil GTC-044, all the rostra are complete and extend from the rear point to the remains of the phragmacone chamber.
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