A new exceptionally preserved ichnofauna from the lower Permian of the Southern Alps: insights into the continental ecosystems after the Artinskian warming event

In the central portion of the Orobic Basin (Trabuchello-Cabianca anticline), on the Valtellina side of the Orobic Alps, the Val D’Ambria (Sondrio, Italy) represents a site of exceptional paleontological richness, both for the high quality and quantity of data.

This sedimentary basin is renowned for its geological complexity and the preservation of a thick stratigraphic sequence dating back to the early Permian. The fossils found at the site belong to the Kungurian Pizzo del Diavolo Formation and are characterized by remarkable diversity, consisting primarily of tetrapod footprints, invertebrate traces, and sparse macroflora remains. The vertebrate footprints represent a diverse ichnofauna, with at least eight different ichnogenera identified, including Amphisauropus, Batrachichnus, Dimetropus, Dromopus, Erpetopus, Hyloidichnus, Limnopus, and Varanopus. Among these, Dromopus and Erpetopus are the most common, whereas footprints assigned to Dimetropus are the rarest and, therefore, of particular interest. These fossil tracks suggest that the area was frequented by a community of terrestrial animals, including reptiles, amphibians and rare synapsids.

In addition to the tetrapod footprints, the discovery of invertebrate traces and macroflora remains provides crucial data for interpreting the depositional environments, as well as the climatic and ecological conditions of the early Permian in the Southern Alps. The combination of these paleontological data, stratigraphic logs, and detailed descriptions of sedimentary facies will allow for a more precise reconstruction of the paleoenvironmental and palaeoecological evolution of the Orobic Basin during the time interval in which these biotas thrived.

Preliminary analyses suggest that the Orobic Basin, located in the paleoequatorial domain, may have hosted diverse depositional settings, under alternating semi-humid and dry seasonal conditions. These frequent changes are characteristic of specific present-day fluvial-lacustrine landscapes, which feature extensive alluvial sand-to-mud flats, playa and ephemeral lakes, situated not far from the basin margins. Further analyses of palynological data and other methodologies, such as C and O stable isotopic analyses as paleoenvironmental indicators on clay deposits and geochemical analyses on volcanic deposits, are expected to provide a better understanding of the climate change during this time interval in the studied area.

Since the late Pennsylvanian, the Palaeozoic was interested by global warming and progressive depletion of the Southern Pole glaciers, which culminated in the Artinskian Warming Event and the subsequent establishment of greenhouse-like-conditions that lasted for the rest of the Permian. Thanks to the different data gathered in the Val D’Ambria locality, its rich fossil record can highlight the consequence of the increased aridity and seasonality on the low-latitude biota during the Kungurian, and potentially provide information regarding the purported Olson’s Extinction (or Olson’s Gap).

The ongoing field research at this site will provide increasingly detailed insights into the biodiversity of this region during the early Permian, enriching our understanding of the dynamics of life and climate change at the end of the Paleozoic Era.