The Sevsk woolly mammoth (Mammuthus primigenius) site in Russia: Taphonomic, biological and behavioral interpretations
Introduction
Remains of the woolly mammoth, Mammuthus primigenius, are common in late Pleistocene sediments of the Russian Plain. The locality reported here, near Sevsk (Bryansk Region, Russia) (Fig. 1A), differs from other large localities in Russia and elsewhere in Europe in representing a natural, catastrophic accumulation of mammoth remains, permitting us to reconstruct the environment, mode of life, and cause of death of a mammoth herd that inhabited this region at the end of the Pleistocene. Detailed studies of pollen, diatoms and small mammals were significant in this analysis. The results indicate a specific taphonomic setting that allows us to document for the first time a family group within a population of M. primigenius.
The bone bed was discovered in the summer of 1988 during excavations in a sand quarry near the town of Sevsk. The remains were concentrated in a small area, where a local company was mining sand for municipal road construction. The fossil discovery was reported to the Paleontological Institute by engineer S.N. Seregin. Before the team from the Paleontological Institute began work at the locality, about 500 m2 of the bone-bearing sand had been removed by the quarrying operation. Commercial operations at the quarry halted in 1991 but have since been resumed.
The quarry is exposed in the terrace on the east side of a 1.5 km long ravine running parallel to the Sev River valley. The ravine is obviously part of the late Pleistocene Sev River channel. The terrace, including the fossil locality, forms a sort of peninsula, previously eroded by the river on the west side, when it formed the ravine, and now eroded on the east side by the present-day river. The present-day Sev River channel is several hundred meters from the quarry, and the locality occurs about 6 m above the present water level. During the past 50 years, the base level of the Sev River has dropped 1.0–1.5 m, and the river is eroding sediments deposited in recent time. Before the commercial operations at the quarry began, the terrace deposits were not exposed.
Section snippets
Stratigraphy and age of the site
The bone-bearing deposits consist of alluvial sands and clay (Fig. 1B). The thickness of the section exposed during commercial quarrying is about 5 m (Lavrov, 1992; Maschenko, 1992, Maschenko, 2002). The base of the section lacks vertebrate remains. Higher in the section, alluvial sands, occurring up to a depth of 240 cm beneath the present-day surface, are replaced by alluvial sands of cut-off origin that contain most of the bone material (up to a depth of 210 cm). This 240–210 cm depth interval
Analysis of the diatom flora
Diatom species change appreciably through the section. Fifty-eight species belonging to 18 genera of the classes Centrophyceae and Pennatophyceae were identified. Eunotia, Pinnularia, Cymbella, and Gomphonema are the most diverse genera. All forms are relatively rare (the occurrence is 1–10 frustules per slide) (Fig. 3).
The diatoms are subdivided into two main ecological groups: planktonic and benthic. There are three planktonic species (5.3% of total species richness); Aulacosira italica
Palynology of the Sevsk locality
The palynological data are correlated with absolute dates from the locality. Pollen spectra are best represented for the bone-bearing layer and overlying strata (Fig. 4). Pollen of tree-shrubs (up to 53%) are predominant through the section. Pinus silvestris and Pinus sibirica (up to 94%) are most abundant. Pollen of Betula pubescens and B. nana is scarce. Pollen of other coniferous (Larix, Abies) and broad-leaved species (Alnus, Quercus, and Fraxinus) are represented by single grains.
Analysis of the Sevsk microvertebrates
About 30 specimens of rodents were found by washing 500 kg of sediments from the main bone-bearing layer at Sevsk. Ten specimens of Lagurus lagurus (Pall.) and one specimen of Microtus gregalis (Pall.) were identified. Two other specimens identified as Microtus sp. probably belong to the same species.
Neither L. lagurus nor M. gregalis occurs in the modern fauna of the Bryansk region. The former presence of these species at Sevsk indicates that they were common in the small mammal fauna at the
Archaeological materials at Sevsk
Sixteen worked flint pieces were found at Sevsk. All flint implements occur at the base of the main bone-bearing layer, primarily towards the center of the lens. However, there is no evidence of human processing of the mammoth remains, such as cut-marked bone. There are no hearths, no killing implements, no burned bones, and no activity areas for butchering or processing. Therefore, it is inferred that Paleolithic humans were not responsible for the accumulation of mammoth material at Sevsk.
Taphonomy of the mammoth bone bed
The entire excavation area encompassed nearly 1200 m2, of which the bone-bearing lens occupied about 800 m2, including the portion of the unit destroyed by commercial quarrying (Fig. 2A). The bone-bearing lens is elongate in plane view. The bones were distributed unevenly, both horizontally and vertically. In some instances, mammoth skulls, partial skeletons, and isolated bones were stacked vertically in two or three layers. Three nearly complete and two partially preserved skeletons of baby
Analysis of the mammoth bone assemblage
The minimum number of mammoths preserved at Sevsk was determined by identifying long bones from the right-hand side of the body and by counting crania, mandibles and pelvic elements. Six fairly complete skulls and 16 partial skulls exhibiting various degrees of preservation were identified. Tusks were preserved both separately (Fig. 6B–D) and in the alveoli of skulls (Fig. 7B, E, D). In tallying the long bones, epiphyses without diaphyses were viewed as complete elements in some cases.
Ribs,
Age and sex profile
The 33 mammoths recovered at Sevsk are divided into five age groups. Group I includes animals from 1–2 months to 2 years old; group II from 2 years to 5–6 years old; group III from 6–7 to 11–13 years old, group IV from 13 to 35 years old; and group V over 40 years old. The determination of the boundaries of size variability in group III posed the greatest difficulty. The most exact chart for this group was made from the tibia. For groups I, II, IV, and V, only the sizes of bones of the
Summary
Sevsk mammoths are characterized by small size and weak sexual dimorphism. Sexually related size variability in L. africana can sometimes reach 40% (Haynes, 1991). The smallest tibia from Sevsk (Fig. 11A) that has completely fused epiphyseal sutures is 42 cm long and belongs to a female. The skeletal height of this smallest adult specimen does not exceed 190 cm. Thus, the range of body-size variability between the largest and smallest animals from Sevsk is about 20%.
It is likely that most of the
Conclusions
The unique materials from the Sevsk locality provide a special opportunity for the studies of biology and natural history of the woolly mammoth. It particular, some important features of mammoth ecology and ethology become clear.
Owing to specific geological conditions, it is reliably established that the Sevsk mammoths died simultaneously, during one season. The main bone-bearing layer of the locality is homogeneous and preserved most of the mammoth remains in situ. Only a minor part of the
Acknowledgments
The representatives of the Sevsk Municipal Authorities provided the organizational and technical assistance that allowed us to undertake the excavation during 1989–1991. The head of the Mammal laboratory of the Paleontological Institute of Russian Academy of Sciences (PIN RAS), V. Yu. Reshetov, supervised the administrative and organizational preparation of field work in the Bryansk Region and gave valuable advice during the excavations. The professional work of the following technicians from
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