Fabio Massimo Petti

Dinosaur Tracks as Paleogeographic Constraints: New Scenarios for the Cretaceous Geography of the Periadriatic Region

A really unexpected finding of sauropod and theropod footprints in southern Latium raises to four the number of the trampled levels recognized in central and southern Italy. After the recent findings in Latest Jurassic and Early, mid and Late Cretaceous carbonate platform deposits of the Periadriatic region, dinosaur footprints seem to provide very important paleogeographic constraints for reconstructing the geodynamic history of the Mediterranean area. The presence of a varied ichnoassociation makes acceptance of the current paleogeographic models concerning the relative and absolute position of the Laziale-Abruzzese-Campano and of Apulian-Dinaric domains during the Late Cretaceous more and more problematic. Dinosaur footprints, combined with other paleontological data, demonstrate that these areas were never completely pulled apart by deep seaways, while frequent or continuous links between them, and to southern and northern mainlands, probably persisted. These data also allowed us to improve our understanding of the timing of the Mesozoic plate motion in this segment of the Western Tethys.

The Origin and Early Radiation of Archosauriforms: Integrating the Skeletal and Footprint Record.

We present a holistic approach to the study of early archosauriform evolution by integrating body and track records. The ichnological record supports a Late Permian–Early Triassic radiation of archosauriforms not well documented by skeletal material, and new footprints from the Upper Permian of the southern Alps (Italy) provide evidence for a diversity not yet sampled by body fossils. The integrative study of body fossil and footprint data supports the hypothesis that archosauriforms had already undergone substantial taxonomic diversification by the Late Permian and that by the Early Triassic archosauromorphs attained a broad geographical distribution over most parts of Pangea. Analysis of body size, as deduced from track size, suggests that archosauriform average body size did not change significantly from the Late Permian to the Early Triassic. A survey of facies yielding both skeletal and track record indicate an ecological preference for inland fluvial (lacustrine) environments for early archosauromorphs. Finally, although more data is needed, Late Permian chirotheriid imprints suggest a shift from sprawling to erect posture in archosauriforms before the end-Permian mass extinction event. We highlight the importance of approaching palaeobiological questions by using all available sources of data, specifically through integrating the body and track fossil record.

Dinosaur tracks in a marginal marine environment: the Coste dell'Anglone ichnosite (Early Jurassic, Trento Platform, NE Italy)

Bipedal tridactyl dinosaur footprints dominate the Early Jurassic Coste dell’Anglone tracksite, located on the eastern slope of the Mt. Biaina-Mt. Brento chain (Trentino Alto-Adige, NE Italy). The site yielded 544 tridactyl footprints, arranged in 20 long trackways, and belongs to the upper part of the Calcari Grigi Group (lower portion of the Rotzo formation). All the tracks can be attributed to smalland medium-sized theropods. Trace fossils were discovered in a peri tidal carbonate succession deposited in a marginal area of the Trento carbonate Platform, which has so far been considered fully marine (subtidal) in origin. The Coste dell’Anglone outcrop represents one of the most extensive Early Jurassic dinosaur tracksites in the Southern Alps and is probably the last dinosaur occurrence on the Trento Platform. The ichnological and sedimentological analyses of the track-bearing sequence indicate a depositional setting corresponding to a tidal flat embayment, positioned on the westernmost sector of the Trento Platform, close to the Lombardy pelagic basin. Stratigraphical data indicate that dinosaur populations lived in this area until the Sinemurian. A comparison with the Early Jurassic theropod tracks global record is here provided, along with an investigation into the possible trackmaker. The tracks share unambiguous similarities with the tridactyl tracks discovered at the Lavini di Marco tracksite, in the basal portion of the Calcari Grigi Group (Monte Zugna formation, Hettangian) and with theropod tracks from the Lower Jurassic of Poland, France and the United States. This new discovery therefore supports calls for a re-examination of the palaeogeographic reconstruction of the Southern Alps during the Early Jurassic

MIDDLE JURASSIC - EARLY CRETACEOUS INTEGRATED BIOSTRATIGRAPHY (AMMONITES, CALCAREOUS NANNOFOSSILS AND CALPIONELLIDS) OF THE CONTRADA DIESI SECTION (SOUTH-WESTERN SICILY, ITALY)

Facies and biostratigraphic analyses of the Contrada Diesi succession, cropping out along the northern slope of Mt. Magaggiaro (Sciacca, SW Sicily), provided new data on the Middle Jurassic-Early Cretaceous pelagic sedimentation in the Saccense domain. The richness in ammonites allowed the identification of Bathonian-Kimmeridgian Biozones and Subzones, while the Tithonian-Valanginian interval was defined mainly by calpionellids and calcareous nannofossils. Facies and microbiofacies analyses of the Jurassic-Cretaceous pelagic sediments of the area, together with ammonite, calpionellid and calcareous nannofossil integrated biostratigraphy, were very effective tools for comparison of biostratigraphic events. Many gaps in sedimentation were recognized, the most important spanning the middle and late Berriasian and part of the early Berriasian. The Contrada Diesi succession provides new litho-biostratigraphic data on the Saccense Domain. It suggests a high degree of internal variability tied to the irregular paleotopography of the carbonate platform substrate (Inici Fm.), derived from Early Jurassic tectonics. Gaps in sedimentation in the Contrada Diesi sections indicate that the environment of the Saccense Domain was characterized by a variable rate of sedimentation and energy changes.

The Mesozoic Vertebrate Radiation in Terrestrial Settings

In the last three decades vertebrate ichnology went through a renaissance due the discovery of new tracksites and the application of rigorous analytic methods (e.g., synapomorphy analyses). This finally allowed full hypothesis testing and a better integration of vertebrate ichnology in paleobiologic, paleoecologic and paleobiogeographic studies. In this chapter we provide a review of recent advances in vertebrate ichnology, focusing on Mesozoic terrestrial reptiles.

Dinosaur footprints as ultimate evidence for a terrestrial environment in the late Sinemurian Trento Carbonate Platform

ABSTRACT Three dinosaur footprints were found, preserved as natural casts, on the roof of a First World War tunnel in the Pasubio Massif (Trentino Alto-Adige, northeastern Italy). The Austro-Hungarian Army used the tunnel until 1918, presumably to connect the front- with the back line. The tracks are tridactyl, two of which are organized in a trackway, and provide evidence for the presence of medium-sized theropods. The track-bearing horizon is situated at the base of the Rotzo formation (Calcari Grigi Group), within shallow-water black shale deposits characterized by oligotypic small bivalves, oligohaline ostracodes, and thecamebians. Vertebrate remains, represented by crocodyloform teeth and fish scales, were also identified from the same stratigraphic portion. The occurrence of dinosaur footprints from black shale levels sheds light on their controversial interpretation, confirming the occurrence of terrestrial environment in the Trento carbonate platform during the late Sinemurian. Dinosaur tracks indicate the emersion of a sector of the tidal flat during the deposition of the basal Rotzo formation, and suggest a complex paleonvironmental scenario in which tidal flats were associated with freshwater ponds and islands.

Dinosaur diversification linked with the Carnian Pluvial Episode

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.Dinosaurs originated ~245 million years ago (mya) but did not diversify until some time in the Late Triassic. Here, Bernardi and colleagues synthesize palaeontological and dated stratigraphic evidence to show that dinosaur diversification followed the Carnian Pluvial Episode 234–232 mya.

Vertebrate and Invertebrate Trace Fossils in the Late Pennsylvanian (Carboniferous) Fluvio-Lacustrine San Giorgio Basin (South-West Sardinia): Remarks on the Oldest Continental Ichnoassociation of Italy

ABSTRACT A new study of the ichnotaxonomy and palaeoecology of the Late Pennsylvanian San Giorgio Basins trace fossils was carried out. The tetrapod tracks were attributed to Batrachichnus salamandroides and to indet. tracks with a possible small temnospondyl and/or lepospondyl affinity. The invertebrate trace fossils include locomotion traces (Diplichnites isp.), grazing traces (Cochlichnus anguineus), and feeding structures (Treptichnus bifurcus, Treptichnus isp.). The trace fossils were evaluated by means of ichnofacies, highlighting a transitional Scoyenia-Mermia ichnofacies, typical of Carboniferous freshwater settings. The trace fossil co-occurrence and taphonomy was utilized to give a new interpretation of the fossil-bearing lithofacies, which are dolomitic mudstones-fine sandstones expression of marginal lacustrine environments repeatedly subject to flooding (three different ichnoassociations highlight different bathymetry/emersion). This is the oldest continental ichnoassociation of Italy, and its moderately high diversity and complexity suggest further study of this important Carboniferous trace fossil locality.

Soldier Tracks in a First World War Fort (Valmorbiawerk, Trento, Italy)

A set of partial or complete boot tracks is described from the floor of a tunnel in a First World War fort in the Trentino Alto Adige region. The tracks belong to the right and left boots of the same person. The deepest imprints have been left by the heels, which were reinforced by rectangular and square-shaped hobnails. From studying all the tracks, it has been possible to reconstruct the complete hobnail set of both boots and compare them with coeval boots used by soldiers. Depending on the nationality and branch of the armed services, the nails had different shapes and arrangements. The layout and the shape of the tracks perfectly match the mountain footwear used by the Austro-Hungarian army. The succession of events during the building of the Valmorbiawerk indicates that the tracks could have been imprinted between spring 1914 and May 1915.

LATE TRIASSIC (EARLY-MIDDLE CARNIAN) CRUROTARSAN TRACKS FROM THE VAL SABBIA SANDSTONE (EASTERN LOMBARDY, BRESCIAN PREALPS, NORTHERN ITALY)

A new Late Triassic tetrapod tracksite was discovered north of the Zone village, on the north-eastern side of the Iseo Lake (Southern Alps, Brescia, Lombardy). The tracks are preserved on two distinct bedding planes, belonging to the lower/middle Carnian Val Sabbia Sandstone. The ichnoassemblage is composed of about seventy footprints, organized in six quadrupedal trackways exhibiting both wide and narrow gauge. All the trackways can be attributed to a crurotarsan archosaur trackmaker and at least three of them could be assigned with confidence to the ichnogenus Brachychirotherium Beurlen 1950. If we exclude a dubious Brachychirotherium specimen track from Mt. Pelmetto (Dolomites), the Zone material represents the first well documented report of this ichnogenus from the Upper Triassic of Northern Italy. The footprints have been analyzed both with traditional methods, and with 3D technologies, such as the terrestrial laser scanner. The ichnoassemblage, although not exceptionally preserved, adds new important data for the stratigraphic distribution of crurotarsan tracks in the Triassic of Southern Alps.