Exceptional mammoth discovery from the North Sea

Dick Mol (The Netherlands)

If we consider the huge number of fossil remains of ice age mammals dredged up from the floor of the North Sea, we can only conclude that the Pleistocene era must have resembled a paradise between what is now the UK and the Netherlands. The majority of the remains date from the late Pleistocene (somewhere between 100,000 and 10,000 years ago), and we are speaking of TONS of bones, mammoth molars, tusks, hooves, teeth, and so on.

These are the remains of large grazers, especially the mammoths. It appears that the area between the UK and Holland was not the North Sea we know today. Rather, it was a huge, mostly treeless, dry steppe, where the Thames from the West and the Rhine, Meuse and Schelde from the East meandered into river deltas before entering the Atlantic Ocean way to the North. This was the typical landscape at that time, the megafauna steppe, found stretching across the land masses of the Northern Hemisphere in which the mammoths, rhinos, steppe bison and their associated, large predators were thriving.

Mammoths

The enormous amounts of mammoth remains in the North Sea suggest that large herds of these pachyderms roamed the area: in terms of a larger time frame, think of hundreds of thousands of animals. The most abundant remains are molars, due to their hardness and durability. The abundance of the last molars, the M3/m3, also reveals that animals were attaining advanced ages, suggesting good health and, therefore, suggests the presence of good environmental conditions. Nevertheless, remains of juvenile animals are also a common phenomenon.

Unfortunately, complete skeletons have never been found in the North Sea. Sometimes, matching fossils are found in the nets of the fishermen when they dredge the sea floor for flatfish. For instance, the upper and lower jaw of the same individual may be found together. This indicates that the animal must have lived and died in that area instead of being transported there over a great distance from the mainland to the sea by rivers or ice sheets.

Giant catches

For more than a hundred years, beam trawlers have fished the North Sea using sophisticated gears gently touching the sea bottom to activate the flatfish in the sand to capture them in the nets. However, the shallow, buried fossil remains are also stirred up in this way and end up in the net. This is how several fishermen have dredged up and secured many scientifically valuable specimens. So, every Friday, when the trawler fleet returns to harbour, they may encounter a crowd of researchers, eager to take charge of those Pleistocene fossil remains.

Thanks to the close co-operation between these fishermen and palaeontologists, many shelves of museums in the Netherlands and private collectors house impressive collections of mammoth remains and other species, containing the full range of individuals from unborn, foetal specimens to juvenile and adult remains.

In June 2005, Skipper Pieter Oost from Stellendam was fishing in the Eurogeul or Euro Gully with his beam trawler “Zeearend”, just within the 12-mile zone of Holland. This gully happens to be very rich in mammoth fossils. It is continually kept deep enough for large ships to reach the Port of Rotterdam. The sand is blown up and sucked away, which leaves the heavier buried fossils exposed on the sea floor, to be dredged up eventually by fishermen. They know that, so they are not surprised to find all kinds of bones, tusks and molars in their nets.

However, in June 2005, the fishermen were surprised to see a very large and unusual shape when they hoisted their net onto the deck. It was a large and complete mammoth skull with only the tusks being broken. A complete mammoth skull is not a common specimen. Complete lower and upper jaws are common but they often heavily damaged. However, a big, intact and complete skull is a rarity and this one was among the biggest ever found in The Netherlands.

The tusk remains have a length of 107cm and 84cm and its large diameter (177mm) suggest that the original length would have been around 3m. Furthermore, the skull without tusks weighed around 100kg. Each tusk weighed something like 40 to 50kg, which is only slightly less than those of another skull caught at the same location during 2002. This other skull still carried a complete tusk of slightly over 3m in length. Both skulls are superb museum-quality and belonged to large mammoth bulls that roamed the area some 40,000 years ago. The condition of the upper molars suggests that the animals had reached a respectable age of about 45 years at death.

The mammoth skull

Compared to its body, a mammoth skull appears to be oversized. However, it is not very heavy since it has an open structure consisting mostly of air chambers, which give the skull lots of volume and strength without weighing too much. On the other hand, the tusks are very heavy indeed, composed of massive ivory. Some tusks are known to weigh over 80kg individually, together more than the skull that carries them.

This makes one wonder how it was possible for the animal to carry those immense weights around. Actually, it was because of the very high structure of the skull. It not only has a high forehead but also a high back and this can be seen very well in these large skulls. The back of the skull was attached to large muscles that were attached at the other side to the high dorsal spines of the first thoracic vertebra. These massive muscles ensured a strong attachment to the body and enabled the animal to lift its skull with the massive tusks relatively easily.

Normally, the tusks are anchored in a long alveolus or tusk socket, for about one third of its total length. Furthermore, these tusks do not have roots, which means that after death and decay the tusks can easily be removed from the skull of elephants and mammoths since both these two genera are very closely related.

Conservation

Under normal conditions, animal remains usually decompose completely. However, when they get covered with sand or other sediments, especially in water, there is not much oxygen and the decay stops before the hard parts like molars and bones decompose. This may explain why the Eurogeul is so rich in fossils. Geological research has demonstrated that the Eurogeul site was part of a paleo-river delta of the paleo-Meuse and Rhine. It is quite possible that these animals, after having grazed the tough grasses of the steppe, went there to drink in the abundant meanders of these rivers and somehow died in that area. Then, during higher water levels, the carcasses may have been dragged into deeper water, where they sank and became covered with sediments, ensuring conservation of the hard parts.

Both of the mammoth skulls from the Eurogeul discussed in this article are in the collection of Mr Klaas Post of Urk and have been conserved using special agents. They have been completely preserved in the state they were found, with just some small damage being repaired. The first specimen was found in 2002 and is displayed in the palaeontology Museum “De Groene Poort” in Boxtel in the Netherlands. The second one was found in 2005 and was displayed immediately after the catch for three months unpreserved, in its original wet beauty, in the Dutch Naturalis National Natural History Museum in Leiden. Now, this cranium is an eye-catcher in Mr Post’s office until it finds its last and final resting place in a Dutch public museum.