Ongoing research at the late Middle Pleistocene site of La Polledrara di Cecanibbio (central Italy), with emphasis on human–elephant relationships
Introduction
The site of La Polledrara di Cecanibbio (NW of Rome, Italy, Fig. 1) was identified in 1984 within a program of territorial surveys promoted by the “Soprintendenza per i Beni Archeologici di Roma” (Anzidei et al., 1988). Regular excavations started in 1985 and unearthed, over an area of more than 850 m2, a portion of paleosurface referable to the bed of a small water course, cut into a bank of compact granular tuffite. Faunal remains, mostly referable to large mammals and prevalently Palaeoloxodon antiquus and Bos primigenius, were distributed with variable density over the paleosurface, and associated with lithic and bone artifacts (Anzidei et al., 1988, Anzidei et al., 1989, Anzidei et al., 1993, Anzidei et al., 1999, Anzidei et al., 2001, Anzidei et al., 2004, Anzidei and Arnoldus Huizendveld, 1992, Anzidei and Arnoldus Huizendveld, 1993). Taphonomic observations indicated that the very large number of bones resting on the bottom of the bed had been initially transported during flood phases and then settled when the water level dropped. The alternation of these phases, separated by the same number of periods of normal flow, produced several erosive and depositional phenomena with the consequent dislocation of the bone remains. Furthermore, stratigraphic-sedimentological analysis revealed that the bed gradually became swampy with the accumulation of cineritic tuffite fluvial sediments and the formation of areas of stagnant and muddy pools where some elephants became trapped. Skeletal elements of these animals were found in partial anatomical articulation with some of them in living position, associated with lithic artifacts with fresh surfaces that, in several cases, even preserved use wear traces (Anzidei et al., 1999, Anzidei et al., 2004).
Because the site was excellent due to its state of preservation of its fossil remains, development of a museum began in 2000 and is still in progress now (Anzidei et al., 2004). The museum structure covered an area of 900 m2 and included a portion of the palaeosurface already brought to light in previous years and left in situ, as well as an unexplored part of the deposit where excavation is still in progress (Fig. 2).
Since 2006, excavations resumed with greater continuity and new and interesting data were acquired, significantly improving the knowledge of different aspects of the site. The aims of this paper, although only preliminary, are to: a) present the most recent interpretations about the reconstruction of the geological and depositional context of the site as well as the genesis and evolution of the palaeoenvironment; b) provide an updated faunal list and discuss the straight-tusked elephant remains in light of the variability of European palaeoloxodonts; c) report the discovery of a Homo heidelbergensis tooth; and d) describe the lithic complex associated with the remains of a carcass of an elephant, still in partial anatomical articulation, and still partially buried in the palustrine deposit.
Section snippets
Geological and sequence stratigraphic setting
The Pleistocene deposits cropping out in the western sector of the Rome area between the Sabatini volcanic complex and the Tyrrhenian Sea have been the subject of several geological, stratigraphic and palaeontological studies (Fig. 1). However, from the work of Conato et al. (1980), the deposits were subdivided into informal lithostratigraphic units named, from the oldest to the youngest, the Monte Mario (Lower Pleistocene), Ponte Galeria, S. Cosimato, Aurelia, and Vitinia formations, ranging
Palaeoenvironmental reconstruction
As recognised by several authors, the richness as well as the presence or absence of some taxa in a given vertebrate assemblage depends on taphonomic and/or random factors (Behrensmeyer, 1978, Behrensmeyer, 1982, Behrensmeyer, 1988, Behrensmeyer, 1991, Koster, 1987, Kidwell and Behrensmeyer, 1988, Allison and Briggs, 1991, Rogers, 1993, Lyman, 1994, Andrews, 1997, Martin, 1999, Martin et al., 1999, Rogers and Kidwell, 2000, Milli and Palombo, 2005, Milli et al., 2008) including the nature of
Fauna
During the more than twenty years of excavation, an extraordinarily rich sample of vertebrate remains, so far over 20,000 specimens, have been unearthed from the fossiliferous deposits at La Polledrara di Cecanibbio. The excellent state of preservation of the fossil remains is also thanks to the presence of fluorite in the sediments, a mineral that is closely connected to the collateral phases of the Sabatini Volcanism and, in general, to the presence of heavily mineralized fluids along
Anthropological remains
The tooth recovered at the site of “La Polledrara” is a deciduous second maxillary molar (Fig. 9f, g), probably belonging to a juvenile individual of Homo heidelbergensis (possibly H. heidelbergensis steinheimensis following Manzi, 2011), with an age at death of between 5 and 10 years (Ubelaker, 1987). The preservation state is not optimal, as the tooth lacks a portion of the crown on the distal side and almost all the roots, probably because of post-mortem fractures. The occlusal surface is
Morphology of the channel bed and the marshy areas
Recent excavations, although still in progress, allow a more complete view of the spatial distribution of the skeletal remains on the two banks of the water course. The left one was investigated before the construction of the museum, and the right one was recently identified. It is now possible to integrate the already published information with some hypotheses on the deposition mode of the skeletal and archaeological remains, based on the morphology of the bottom of the riverbed, the spatial
Homo/elephant relationships
The site of La Polledrara di Cecanibbio has a markedly palaeontological connotation. Human presence at the site is evidenced by lithic artifacts and manuports, a few bone tools and some intentionally fractured bone diaphyses, scattered over this naturally formed and complex deposit The lithic industry, collected during the excavation before the musealization of the site, includes about 500 artifacts obtained from flint and, more rarely, siliceous limestone pebbles, mainly of small size. These
Final remarks and research prospects
La Polledrara is an exceptionally interesting palaeontological site that documents a very well preserved Middle Pleistocene fluvial environment. The studies carried out so far allowed the reconstruction of most of its sedimentary environment. The environmental characteristics of the site, with the presence of the water course and marshy areas, made it particularly attractive for the human groups living in the territory who appreciated the extraordinary possibilities of exploitation of animal
Acknowledgments
We thank the two anonymous reviewers for their comments. Dr. Steven Thomas Haire revised the English version of the manuscript.
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