Coupling tooth microwear and stable isotope analyses for palaeodiet reconstruction: the case study of Late Middle Pleistocene Elephas (Palaeoloxodori) antiquus teeth from Central Italy (Rome area)

摘要

The identification of mammal palaeodiet is a useful tool for the reconstruction of palaeoenvironmental conditions. From the second half of the last century, two methodological approaches based on microwear enamel defects, produced on tooth enamel by the attrition with food particles, and on stable isotope analyses have been of increasing interest. The analysis performed on the two sets of Elephas (Palaeoloxodori) antiquus Falconer and Cautley, 1847 last molars, belonging to late Middle Pleistocene faunas from La Polledrara di Cecanibbio and Casal de' Pazzi (Central Italy, Rome area), highlights the possibility of establishing the dietary adaptation of elephants, on the basis of a large data set and of a multidisciplinary approach. Elephants from La Polledrara di Cecanibbio and Casal de' Pazzi are characterised by prevalently an intermediate type of dietary adaptation (grasses, leaves, bark and coarse stem), although the average microwear topographies of the samples are different in the two sets. In La Polledrara di Cecanibbio molars, coarse, often crossed scratches prevail, and pits, either large or small, occur in about the same percentage as striations. The Casal de' Pazzi sample is characterised by a larger number of mixed (coarse and fine) scratches and a lower percentage of pits. For these elephants, the amount in their diet of gramineae or vegetables relatively rich in phytoliths was important. During the deposition of fossiliferous levels, similar features characterised the palaeoenvironment: wooded grassland in moderately humid and temperate climate conditions. The results of isotope analyses suggest differences in terms of temperature or humidity: warmer or more arid conditions for La Polledrara than for Casal de' Pazzi. Taking into account that grazing among elephants may be related to increasing availability of grass during more humid periods, whereas browsing is augmented when the grass tend to be withered, as reported for extant savannah, the different patterns in microwear seem to be consistent with oxygen isotope data. Carbon isotope measurements on structural carbonate of biogenic apatite (enamel) suggest a more closed canopy forest at Casal de' Pazzi and more arid climate at La Polledrara di Cecanibbio. Strontium isotope composition (~(87)Sr/~(86)Sr) helps to define the geographical area where the two populations were living, which is confirmed to be limited to the volcanic province of Latium.