Fabio Massimo Petti

The Dolomites (northern Italy) yield exceptional Permian–Triassic outcrops with well-developed biostratigraphic, chronostratigraphic, and magnetostratigraphic frameworks. This field guide provides a compact, field-oriented synthesis of key localities spanning the Permian to the Late Triassic. Day 1 focuses on the Permian record in the GEOPARC Bletterbach, where the Auer/Ora Formation (Athesian Volcanic Group) and its overlying terrestrial red-bed succession (Grödner Sandstein/Val Gardena Sandstone) document volcanic emplacement, landscape evolution, arid to semi-arid floodplain processes, and terrestrial ecosystems including plants, palynomorphs, and vertebrate track assemblages. Day 2 starts with the Permian–Triassic boundary at the Pufels/Bulla section, a key shallow-marine succession, and continues with the Seceda succession. The day concludes at Passo Gardena (Sella Massif), highlighting platform–basin architecture and mass-transport processes, including the Gardena Megabreccia and alternative genetic models. Day 3 explores the classic Carnian St. Cassian/San Cassiano Formation in the Pralongià-Stuores-Settsass area and links outcrop observations to the regional palaeontological heritage, including museum collections. At the Stuores Wiesen crops out the GSSP at the base of the Carnian, the so far only GSSP in the Dolomites. Together, these sites illustrate the integrated stratigraphical, sedimentological, palaeontological, and volcanological framework of famous reference sections and evidence environmental and climatic changes through the Permian–Triassic.

TThe one-day field trip to the Lavini di Marco tracksite (Trentino-Alto Adige/Südtirol, NE Italy) offers the opportunity to appreciate one of the most extensive and interesting European dinosaur tracksites. The ichnoassemblage, Hettangian in age, is constituted by numerous quadrupedal trackways, referred to medium-sized sauropodomorphs, and hundreds of tridactyl footprints, produced by small- to large-sized theropods. The itinerary, developed in six stops, will focus on the most significant occurrences of the tracksite, highlighting the theropod biodiversity revealed by numerous tridactyl tracks, such as ROLM 198, ROLM 137 and ROLM 219, and the most spectacular and relevant quadrupedal trackways, such as ROLM 26, known as the "rock-climbing dinosaur" trackway, and ROLM 577, holotype of the ichnospecies .

Dinosaurs diversified in two steps during the Triassic. They originated about 245 Ma, during the recovery from the Permian-Triassic mass extinction, and then remained insignificant until they exploded in diversity and ecological importance during the Late Triassic. Hitherto, this Late Triassic explosion was poorly constrained and poorly dated. Here we provide evidence that it followed the Carnian Pluvial Episode (CPE), dated to 234–232 Ma, a time when climates switched from arid to humid and back to arid again. Our evidence comes from a combined analysis of skeletal evidence and footprint occurrences, and especially from the exquisitely dated ichnofaunas of the Italian Dolomites. These provide evidence of tetrapod faunal compositions through the Carnian and Norian, and show that dinosaur footprints appear exactly at the time of the CPE. We argue then that dinosaurs diversified explosively in the mid Carnian, at a time of major climate and floral change and the extinction of key herbivores, which the dinosaurs opportunistically replaced.

The Permian–Triassic mass extinction (PTME) had an enormous impact on life in three ways: by substantially reducing diversity, by reshuffling the composition of ecosystems and by expelling life from the tropics following episodes of intense global warming. But was there really an ‘equatorial tetrapod gap', and how long did it last? Here, we consider both skeletal and footprint data, and find a more complex pattern: (i) tetrapods were distributed both at high and low latitudes during this time; (ii) there was a clear geographic disjunction through the PTME, with tetrapod distribution shifting 10–15° poleward; and (iii) there was a rapid expansion phase across the whole of Pangea following the PTME. These changes are consistent with a model of generalized migration of tetrapods to higher latitudinal, cooler regions, to escape from the superhot equatorial climate in the earliest Triassic, but the effect was shorter in time scale, and not as pronounced as had been proposed. In the recovery phase following the PTME, this episode of forced range expansion also appears to have promoted the emergence and radiation of entirely new groups, such as the archosaurs, including the dinosaurs.