In this article, we will give a short report about the excavation, together with some information about this mastodon (Mammut borsoni).
During digging work in October 2006, a crane operator discovered a fossil tusk in a sandpit in Milia. He contacted Professor Evangelia Tsoukala of the Aristotle University. She is a palaeontologist, specialising in mammals and had already completed four excavation projects for Pliocene mammals in the Milia region, all of which were pretty amazing. One of these had resulted in finding the previous longest pair of tusks in the world.
These belonged to a mastodon, with the scientific name of Mammut borsoni, and measured 4.39m each.
The tusks are almost straight, hardly curved at all and, in a live mastodon, would have stuck out horizontally right in front. This Proboscidean differed from other species, like modern elephants, having a different body shape. It was much more elongated, while its teeth and metabolism were optimized for browsing twigs and leaves.
Borson’s mastodon
Honouring Mr Borson, he named this species, Mastodon borsoni. Nowadays, this species is put into the genus Mammut and, therefore, the current, correct name is Mammut borsoni. Both Mammut borsoni and Mammut americanum are put in the family of the Mammutidae, subfamily Mammutinae, being zygodont mastodons, with molars showing typical, comb-shaped ridges. M. borsoni was a massive sturdy pachyderm, with male bulls reaching shoulder heights of almost 4m and some developed gigantic tusks. It is also the largest known mastodon. Borson’s mastodon, which is found both in Europe and Asia, became extinct towards the end of the Pliocene about 2.5 to 3 million years ago, whereas the American mastodon survived, at least until the early Holocene, some 10,000 years ago.
We were very lucky to be in Greece participating at the 12th International Cave Bear Symposium and studying the collections of Evangelia Tsoukala when this new discovery was made. This opportunity fell right into our hands. Bothtusks, still in situ, were still being excavated and a measuring tape revealed that one was at least 5m in length. That certainly required more research. Evangelia Tsoukala included us in a plan for excavation to take place in July 2007, since there might be a lot more to be uncovered. The contractor agreed, albeit reluctantly, to postpone the digging activities in that part of the sand pit.
We were invited to participate in the excavation starting on 17 July 2007. Vigorous discussion took place about which part should be the first to be uncovered and how generally to proceed. The highly motivated excavation team of about 12 students was led by the principal investigator, obviously professor Evangelia Tsoukala, in close coordination with the co-principal investigator, Dick Mol.
To reach the layers quickly where the fossil remains were embedded about 2.5 million years ago, we used a large excavator to remove sand overburden. The next day, the first tusk was completely exposed and the second was localised, and found to be slightly shorter. Unfortunately, the state of preservation was not very good and, therefore, recovery would be very delicate. Meanwhile, it turned out that the excavation area of 8m by 4m, nicely marked out with red-white marker tape, contained a lot more remains of the original owner of these giant tusks. And a part of the skeleton was recovered in the next few days under a scorching hot sun, with temperatures of up to 45oC.
Apart from the giant tusks, parts of the upper jaw bone (with a splendid molar) were uncovered, followed by the lower jaw with molars somewhat later. Although broken, it was in excellent condition. This mandible had lost the lower tusks, but the tusk-sockets were well preserved. Mammut borsoni had rather large lower tusks with a diameter of 6cm to 8cm at the symphysis of the mandible. The last and penultimate molars are present, revealing not only that this mastodon must have been a browser, but also something about its age when it died. From these particular fossil remains, we concluded that its age must have been between 25 to 30 years at time of death. The huge limbs reveal the enormous dimensions of this bull in his prime. These discoveries are unique and very spectacular.
That day, some digital pictures were released to the BBC and, one hour later, these appeared on the news website of the BBC. The Mastodon of Milia-5 was now world news. More requests followed for more pictures and information from all over the world, keeping the team busy. However, there was no time for too much diversion, as there was a deadline to meet – Evangelia Tsoukala had an appointment with the local authorities from the Prefecture of Grevena on Saturday, 28 July. They were going to examine the results of the excavation team and the tusks had to be properly conserved and on display by then in the small palaeontological exhibition centre of Milia.
All remains unearthed had to be measured and drawn, which is a meticulous job. No data should be lost. Next, all skeleton parts (some 30 in total) had to be plastered for protection, preventing further damage during transport to the museum. These fossils had been subject to high pressure due to the weight of the almost 20m of overlying sand layers, and this caused deformation in many cases.
Accordingly, the tusks were shattered into several pieces and their enormous length prevented the crew from picking these up and transporting them all in one piece. These activities also had to be done in scorching hot weather and work went on until 22:30. Only drinking many litres of cold water kept the crew going.
But a deal is a deal, and on Saturday afternoon, 17:00 sharp, both tusks (a matching left and right pair) were put into position in the magnificent little museum in Milia. Their sizes, measured along the outside of the curvature (that is, the underneath surface) are 4.58m and 5.02m respectively. Therefore, these are the longest tusks in the world – another new world record.
One wonders how an animal could live with those tusks. How could they have manoeuvred with them? The sheer inertia of their mass would cause significant complications making turns, not to mention avoiding obstacles, like rocks and trees. However, unlike elephants, the tusks do not point downwards but more forwards and one third of the tusk is also embedded in the dental socket. Moreover, the animal was a large bull in its prime, standing an estimated 3.30m to 3.50m at the shoulders.
So, this is how the palaeontological exhibition centre of Milia acquired an unique specimen, which attracts visitors from afar. However, they come not only to see the Borson’s mastodon, but also the other fossil mammal remains, collected in recent years, and nicely on display in the museum. Some are contemporary to the mastodon – antelopes, rhinos and a sabre-toothed cat, also excavated by Professor Tsoukala’s team. There are also remains of a second mastodon species, Anancus arvernensis, the mastodon of the Auvergne (see box).
The mastodon of the Auvergne – Anancus arvernensis
The mastodon van Auvergne – Anancus arvernensis (Croizet & Jobert, 1828) – is a so-called bunodont mastodon, having molars with blunt dental knobs that are paired, lined up next to each other, forming transverse ridges. These molars suggest that the mastodon had a diet of softer food, like leaves, fruit and small twigs.
The worn-down knobs of the upper jaw molars form a clover leaf pattern in profile, which makes them easy to distinguish from the lower molars. The relatively small and hardly-bent tusks are also characteristic for this species (Anancus = without a curve). Moreover, the lower jaw tusks are not present in many specimens, while the upper jaw tusks are covered with a thin layer of enamel. As indicated, these are near straight, bent only slightly outwards.
The discovery of the longest tusks in the world has had a significant impact on the palaeontological centre at Milia. This has resulted, not only in more visitors, but also an increased supply of fossil remains, from a source that readers might not expect – local shepherds. They are the best eyes and ears of the palaeontologists in the area around the village.
As the sheep roam the hills, they trample the soil with their slender feet, sometimes uncovering fossil remains. And several local shepherds have found some very interesting fossils. Now, they are prompted to bring them to the museum, together with information about the location and conditions where they were found. Whenever professor Tsoukala is in Milia, she explores the area, like during the summer of 2008. A shepherd reported the finding of bones on a certain slope. Closer investigation revealed that it was the skull of an extinct rhino species, discovered by the trampling of sheep and a small team of students and experts went to the area. Some haste was required since sheep tend to walk the same paths again and again and might have damaged or even shattered the skull.
The expedition returned in the evening and, in the back of the car, was a delicate, almost complete skull of a Pliocene rhino. The finding place was documented with GPS so that it could be relocated for subsequent exploration. After all, it could be that a complete rhino skeleton was hidden in the soil there. Time will tell.
