Читать книгу The Skull of Quadruped and Bipedal Vertebrates - Djillali Hadjouis - Страница 11

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Proboscideans: The Mammoth (Mammuthus primigenius)

Super-Order Proboscidea.

Order Elephantoidea.

Family Elephantidae.

Genus Mammuthus Brooks, 1828.

Species Mammuthus primigenius Blumenbach, 1799 (woolly mammoth).

1.1. Chronological, geographical and morphological indications of the species

In the species of the Elephantidae Family, the orbits are very advanced on the antero-posterior axis of the skull and open in front of the jugal teeth; these are anatomical characteristics of animals without snouts. In general, in Mammals, the orbits open above the last molars (Lecointre and Le Guyader 2001).

The nose and upper lip are replaced by a flexible tube used for breathing, drinking, picking things up, etc. The lower canines are lost and the upper incisors are transformed into tusks that are continuously developing (Figure 1.1).

The species belongs to one of the three related genera regrouping mammoths and elephants (Mammuthus, Elephas and Loxodonta) included in the Family Elephantidae and classified in the Super-Order Proboscidea. These trunk bearers have provided no less than 170 fossil species, the oldest dating back 55 million years (Eocene). The first Elephantidae appeared in Africa 7 million years ago, the first mammoths 3–4 million years ago. Great confusion reigned for a long time among specialists for the classification of the mammoth and its origin. Today everyone is unanimous in classifying the first mammoths in Africa.

The arrival of mammoths in Europe and Asia took place around 2.6 million years ago. Three main Euro-Asian species followed one another. The southern mammoth (Mammuthus meridionalis), known in Saint-Vallier, Senèze and Chilhac, had a size exceeding 3 meters at the withers, large slightly curved tusks and jugal teeth whose hypsodontic character was still weak. The steppe mammoth (Mammuthus trogontherii), descendant of the previous one, was known in Sussenborn and Mosbach (Germany), in Abbeville and Saint-Acheul (France) and in Great Britain. With a height of more than 4 meters at the withers, this mammoth was considered the largest species in Europe. The woolly or Siberian mammoth (Mammuthus primigenius) is the best known. It appeared about 190,000 years ago and remains the most documented of all fossils due to the many discoveries of whole animals preserved in the permafrost (Guérin 1996a).

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Figure 1.1. Skull of a young present-day Asian elephant in left lateral view. Note the position of the orbits above the maxilla and not behind it (© Éditions Belin/Dominique Visset)

1.2. Mammoth discoveries in Île-de-France

The Fifth International Conference on Mammoths and their Families, held in 2010 in Le Puy-en-Velay, brought together the discoveries of this trunk fossil in more than 20 countries of Eurasia, Africa and America. Even though the Île-de-France region was not represented at this meeting, there have been a large number of remains of woolly mammoths in the departments of Hauts-de-Seine, Seine-Saint-Denis, Val-de-Marne, Yvelines, Essonne, Seine-et-Marne and Val-d’Oise, most of which were cleared during the 19th and 20th centuries as a result of quarrying on the outskirts of Paris. The latter also had its share of discoveries, sometimes complete skeletons, such as that of the Montholon Square near the Montmartre cemetery. In the department of Val-de-Marne, several bony and dental remains of woolly mammoths (M. primigenius) have been found since the end of the 19th century on the banks of the Seine and its confluence with the Marne (Ardouin et al. 2009; Hadjouis 2020a). Thanks to the land development of the last 40 years carried out along the river banks, preventive archeological operations have brought to light new discoveries in well-dated biostratigraphic contexts.

Although the remains of ancient mammoths and elephants unearthed in this small department of south-eastern Paris have been numerous (remains preserved at the Muséum national d’Histoire naturelle, Musée de Saint-Maur-des-Fossés and Musée d’antiquités nationales), most of them were transported and deposited on the banks of the Seine or in the loop of the Marne (Le Perreux, Nogent-sur-Marne, Saint-Maur-des-Fossés, Créteil, Valenton, etc.) without great chronostratigraphic precision.

Appearing in Eastern Siberia around 800,000 years ago, the woolly mammoth’s existence was known in Western Europe 200,000 years ago in chronocultural contexts of the Middle Paleolithic. With the exception of some spectacular specimens, it is mainly mandibles, cranial portions or isolated teeth that are found during archeological excavations or chance discoveries. Among the fossils recently dated by radiometric methods (uranium/thorium and carbon 14), two stand out: the young mammoth from Maisons-Alfort and the skull from Bonneuil-sur-Marne.

1.3. A young mammoth in Maisons-Alfort

The development operations of the Seine-Marne confluence, which began in the 1980s as part of the Seine-Amont project, have highlighted major sites such as Alfort 1 in Maisons-Alfort, located on the left bank of the Marne, a few hundred meters from its confluence with the Seine. One of the plots excavated in 1995 revealed a Neanderthal occupation of the Middle Paleolithic within the alluvial formations (Durbet et al. 1997). The association of identified animal species (aurochs, bison, red deer, Mosbach horse, wolf, mammoth) and the presence of a lithic industry shaped by Neanderthals allowed the reconstruction of paleoenvironments suggesting a cold and dry glacial climate. Several datings on fossil remains ranging from 160,000 to 200,000 years BCE give an image of a glacial environment in the Paris region inhabited by both humans and animals.

Usually, the attribution of Proboscidian species (Elephas, Loxodonta and Mammuthus) is based on complete third molars. It is indeed this last molar which delivers the greatest number of distinctive dental criteria (tooth shape, number of blade teeth and their index, enamel character and their plicature, sinus morphology, etc.). The milk tooth of the Maisons-Alfort baby mammoth was an incomplete lower third milky premolar (D3) with four blades (length: 36.2 mm; height: 44.6 mm).

1.4. A woolly mammoth skull in the reserves

The inventory of Vertebrate faunas carried out at the request of the director of the Val-de-Marne Departmental Archaeology Laboratory, Philippe Andrieux, in the 1990s included a fossil, which exceeded in volume and significance all other bone and dental remains. The skull without mandible of a woolly mammoth, perfectly preserved, had been waiting to be studied since 1923.

Without the short note Les gros blocs quaternaires du port de Bonneuil by Paul Lemoine and Teilhard de Chardin published in the journal La Nature in 1923, no one would know the exact origin of this Propboscidian. The authors describe the work carried out on Barbière Island, a commune of Bonneuil, located between the Marne and Morbras rivers, in order to dig the future coal port of Paris. The dredging of alluvium and blocks of local origin (coarse limestone with ceriths, Champigny limestone, Brie millstone and Fontainebleau sandstone) had yielded the fossil remains of M. primigenius and Bos. The woolly mammoth skull discovered during these dredging operations was not described in this note, but was obviously part of the port works.

It was in the 2000s that we studied it, starting with radiocarbon dating. C14 analyses of the radiocarbon laboratory of Villeurbanne gave dates around 45,000 years BCE, the Middle Paleolithic period. Although more recent than the dates of the Middle Paleolithic site of Alfort 1 (190,000 BC), which also yielded mammoth remains, the fact remains that the skull of Bonneuil figures as a spectacular piece within the Quaternary bestiary of Île-de-France. Although it shows traces of anthropic activity that suggest human intervention, there is nothing to distinguish between hunting and natural death. Similarly, the intervention on its carcass must have taken place in two stages after death.

Another individual was found in the same conditions in Bonneuil-sur-Marne, notably a tusk with traces of anthropogenic cutting.

1.5. A mammoth skull with removed tusks

As mentioned above, the Bonneuil-sur-Marne fossil was not found in welldocumented stratigraphic levels or in a chronocultural context of the Paris Basin. However, its fortuitous discovery during the dredging of the coal port works in 1923 does not in any way detract from its exceptional character. The 45,000 year dating corresponds to a period of cold and dry climate in the Middle Paleolithic. Anthropic indications found on this skull without a mandible suggest hunting practices or the recovery of tusks from a dead animal.

The morphological criteria found on the maxillary teeth show the typical characters of the woolly mammoth (weak enamel with sinuous sinuses, high hypsodontia index and strongly folded enamel ribbons (Hadjouis 2016b)). The age given to this animal at the time of death is estimated to be between 22 and 34 years. It is based on criteria such as the partial wear of the molars, the clearing of their roots and the absence of wear of the last molar, some of whose distal blade teeth were still embedded in the alveolus. Three jugal teeth were still active on their maxillary medium: the second molars on both sides and the right third molar (Figure 1.2). The two anterior molars were in the process of being replaced.

The skull without its mandible, but especially without its tusks, is neither accidental nor a phenomenon of taphocenosis. The very careful cutting of the alveolar banks that surround the tusks testifies to their intentional recovery. Indeed, the posterior paired parts of the alveoli of the tusks were carefully and deeply cut out so as to be able to recover the ivory teeth in their totality.

This practice could only have been carried out by hunters or scavengers in two periods: either the individuals were contemporaries or they were post-Neanderthals. In any case, they recovered the tusks from the carcass of the slaughtered or naturally dead animal to transform ivory materials or for any kind of development.

Figure 1.2. Lower view of a mammoth skull (Mammuthus primigenius), found in the gravel of Bonneuil Port, showing the replacement of the jugal teeth (© Hadjouis)

1.6. A particular tooth eruption

The most evolved Proboscidians of the genera Elephas and Mammuthus adopt/adopted a horizontal type of dental eruption of the jugal teeth, different from the other groups of the Mammalian class whose vertical eruption first concerns the deciduous teeth, replaced by the permanent teeth. In the woolly mammoth (M. primigenius), whose life expectancy was around 60 years, a second tooth eruption would not have been sufficient during its lifetime and all the teeth would have been worn down to the root, causing a final fall of the last stumps. Only the upper incisors called tusks saw two permanent and milky dentitions. To meet the biological longevity of the Elephantidae, a dental replacement cycle exists whose eruptive mechanism will be renewed six times. The mammoth’s extinction coincided with the total stop of this cycle.

When the premolar and molar teeth were drilled, the mesial (anterior) blades of each jugal tooth appeared first, whose tooth wear was not balanced with the distal (posterior) blade teeth, because they were still embedded in the alveolus. This mechanism of pushing from the back to the front, especially in the case of M3s, caused the anterior teeth to fall out, regardless of the dental row (premolars or molars), as they erupted until the end of a cycle. In the end, it was the last molar (M3) that occupied the alveolar spaces of both jaws (Figure 1.3).

Figure 1.3. Replacement of jugal teeth in the mammoth. Premolars and first molars were expelled from the back to the front, keeping only the M3 in each half jaw (© Anthony)