Stable isotope analysis of cervids and equids teeth enamel as a proxy for paleoenvironmental reconstruction at the early Middle Pleistocene site of Ponte Molle (Rome, central Italy)

The Middle Pleistocene locality of Ponte Molle is one of the most important sites of Rome in terms of the number of fossil remains (Iannucci et al., 2023). The locality was exploited for gravel quarrying activities from the 1800s to the early 1900s, resulting in the recovery of a diverse and abundant collection of fossil mammals. Stratigraphic and historical evidence agree in interpreting the Ponte Molle fauna as having been recovered from the lower gravelly level of the Valle Giulia Formation (MIS 13, ca. 500 ka) (Mecozzi et al., 2021). The faunal assemblage includes numerous remains of common species such as Palaeoloxodon antiquus, Bos primigenius, and Cervus elaphus, as well as documenting the presence of more elusive taxa in the early Middle Pleistocene of Europe, such as Sus scrofa, Castor fiber, and Crocuta crocuta (Mecozzi et al., 2021).

This study applies stable isotope analysis (δ¹³C and δ¹⁸O) to the enamel of 29 teeth (12 equids, Equus mosbachensis and 17 cervids, Cervus elaphus and Dama clactoniana), part of the historical collection from Ponte Molle, in order to reconstruct dietary patterns and infer local habitat variability. Carbon isotope ratios (δ¹³C) range from –14.55‰ to –11.61‰ (VPDB), indicating a diet dominated by C₃ vegetation and suggesting temperate woodland to open forest environments. The values obtained for cervids indicate a large interspecific overlap, while differences emerge with respect to equids. Equids exhibit slightly higher mean δ¹³C values (–11.06‰; SD = 0.4) than cervids (Cervus elaphus –12.08‰, SD = 1.3; Dama clactoniana –11.69‰, SD = 1.2), consistent with more open foraging areas; the difference between the mean values of Equus mosbachensis and Cervus elaphus is statistically significant (p<0.05). Oxygen isotope values (δ¹⁸O) range from –6.51‰ and –4.01‰ (VPDB), suggesting variability in water sources. In this case, the difference between mean values is not statistically significant suggesting that the relatively wide range of oxygen isotope values may be related to local hydrological conditions. These results contribute to refining palaeoecological models for central Italy during MIS 13 and highlight the potential of herbivore isotopic signatures as proxies for reconstructing Middle Pleistocene ecosystems. This work has been supported by the Italian Ministry of University and Research, PRIN 2022 scorrimento – Prot. 2022JWFEKE “The evolution of mammals in changing ecosystems of the Middle Pleistocene of Italy”.

References

Iannucci A., Conti J., Curcio F., Iurini D.A., Mancini M., Mecozzi B., Strani F., Sardella R. (2023). Middle Pleistocene mammal faunas of the area of Rome: recent results and ongoing work on the MUST collection. Journal of Mediterranean Earth Sciences 15, 19–37.

Mecozzi B., Iannucci A., Mancini M., Sardella R. (2021). Redefining Ponte Molle (Rome, central Italy): an important locality for Middle Pleistocene mammal assemblages of Europe. Alpine and Mediterranean Quaternary, 34, 131–154.