Megalodonts
| Megalodonts | ||||||||||||
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“Cow step” on the foundation stone of a former alpine hut at the Lainl Alm near Jachenau in the Bavarian Prealps |
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| Temporal occurrence | ||||||||||||
| Ordovician to Upper Cretaceous | ||||||||||||
| approx. 471 to 65 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Megalodontoidea | ||||||||||||
| Morris & Lycett , 1853 | ||||||||||||
| Familys | ||||||||||||
Megalodonts (superfamily Megalodontoidea) are mostly large mussels (bivalvia) that belong to the order Hippuritoida within the superorder Heterodonta . The best-known representatives of this group are the so-called cow step clams from the Triassic , which can be found today as fossils, for example in the Dachstein limestone and similar rocks of the Northern Limestone Alps . The oldest representatives of the group appeared in the Ordovician . The superfamily died out in the Upper Cretaceous .
features
The housings are usually of the same type with a strongly developed and twisted vertebra. What is particularly noticeable in some species is the fact that the “vertebrae” of the mussel, i.e. its older shell parts, are not curled up next to one another, but instead twist like a corkscrew and therefore point away from the central plane like buck horns. However, this is only visible in specimens, because the mussels are preserved in random cross-sections on the rock surface, at least where the surface is not parallel to the layers. The lock edge is transformed into a wide lock plate with only a few large teeth. A relatively thick to very thick shell is also typical of megalodonts. The ligament is external. The sphincters are mostly irregular. The megalodonts inhabited shallow, warm seas, often on the edge of reefs or in the rear reef areas. They probably lived half buried in the sediment. Therefore, the mussels are very often embedded in the rock in their living position. It is assumed that the megalodonts lived in symbiosis with algae, similar to today's giant clams of the Indian Ocean, that is, they harbored green algae on their gills, which supplied the clams with nutrients.
The popular megalodons
The megalodonts of the Upper Triassic are popularly referred to as "deer" - or "cow kick". They were interpreted as traces of the " wild hunt " or as footprints of the " wild women"; in Franconia they were called "goat's feet". This has to do with the idea that forest spirits, albums and drudes did not have human but animal feet. These fossils were also used as a magic defense against evil. That is why their use as foundation stones for alpine huts, as in the two adjacent photos of the Lainl-Alm, is certainly no coincidence.
Conservation and Protection
The megalodonts almost always occur in pure limestone, which was muddy to fine sand during their lifetime and later turned to stone. You cannot knock them out of the rock without destroying them. For reasons of nature conservation, one must not damage the natural rocks in the high mountains. It is therefore better to search for fossils in quarries, for example on the Ofenauer Berg near Golling.
Systematics
Currently, three families are distinguished within the megalodontoid:
- Megalodontidae Moris & Lycett, 1853
- Dicerocardiidae Kutassy, 1934
- Wallowaconchidae Yancey & Stanley, 1999
swell
- ↑ Mayr, Helmut: Paläontologisches Museum München, email from October 10, 2005
literature
- LR Cox et al .: Treatise on Invertebrate Paleontology Part N Mollusca 6 Bivalvia (vol. 2 of 3). N491-N951, The University of Kansas & Geological Society of America, Boulder, Colorado, 1969.
- Michael Amler, Rudolf Fischer & Nicole Rogalla: Mussels . Haeckel library, Volume 5. Enke Verlag, Stuttgart 2000, ISBN 3-13-118391-8 .
