Paolo Mietto

Comparative analysis of Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco): implications for sauropod ichnotaxonomy

Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco) are described and compared. Emphasis is put on track preservation and trackway configuration. The trackways are similar with respect to preservation and the pes and manus track outlines, but they show a large range of trackway configuration. Only one of the trackways reveals digit and claw impressions, and thus differences in trackway gauge and the position of pes and manus tracks are the most explicit characters for their distinction. The Late Jurassic to Early Cretaceous ichnotaxa Brontopodus, Parabrontopodus and Breviparopus are reviewed and a differential diagnosis is given for the trackways studied. The reference trackway of Breviparopus corresponds to one of the studied trackways of Morocco. Parabrontopodus and Breviparopus are considered to be both valid ichnotaxa, even though we recommend the latter to be formally erected based on better-preserved tracks than those currently exposed. The analysed trackways and ichnotaxa suggest that trackway configuration, notably trackway gauge (width), is not decisively influenced by extrinsic factors such as ontogenetic stage, locomotion speed and substrate properties. However, it cannot be excluded that it is related to other factors such as individual behaviour or even sexual dimorphism.

THE PRATI DI STUORES/STUORES WIESEN SECTION (DOLOMITES, ITALY): A CANDIDATE GLOBAL STRATOTYPE SECTION AND POINT FOR THE BASE OF THE CARNIAN STAGE

The Prati di Stuores/Stuores Wiesen section (Dolomites, Italy) is proposed as a candidate Global Stratotype Section and Point for the base of the Carnian Stage. In addition to being a famous, richly fossiliferous locality, it includes the type-section of the Cordevolian substage. The section is located near Pralongia, along the southern slope of the crest separating the Badia/Abtei and Cordevole valleys. Below the levels with Trachyceras aon , the section contains a rich ammonoid fauna that chacterizes the lower part of the Regoledanus Subzone and subsequently records the first appearances of the mid-high latitude genus Daxatina ( Daxatina sp., D. cf. canadensis ) and of traditional Trachyceras with species different from T. aon . Moreover, the Daxatina cf. canadensis Subzone is recognised above the Regoledanus Subzone. Very rare conodonts of the Budurovignatus group and species of Gladigondolella from the diebeli Assemblage Zone occur. Gondolella polygnatyformis, already known from the Aon Subzone, is absent. Palynomorphs, foraminifers, gastropods, bivalves, brachiopods, microcrinoids and holothurian sclerites were studied. Variations in frequency and taxonomic diversity of these faunas suggest anaerobic-disaerobic bottom conditions for the lower-middle part of the section (0-105 m), followed by a more stable oxygen content in the upper portion. Magnetostratigraphy showed four intervals with normal polarity and three intervals with reversed polarity. The Daxatina cf. canadensis Subzone falls close to the normal polarity interval S2n. The present study proposes the FAD of the cosmopolitan genus Daxatina as a marker of the base of the Carnian Stage, placing it at a lower stratigraphic level than previously indicated in the Stuores area. The Prati di Stuores section is proposed as GSSP of the Ladinian-Carnian boundary.

Discovery of a major negative δ13C spike in the Carnian (Late Triassic) linked to the eruption of Wrangellia flood basalts

Major climate changes and mass extinctions are associated with carbon isotope anomalies in the atmosphere-ocean system and have been shown to coincide with the onset of large igneous provinces (LIPs) and, by association, their emissions of greenhouse gases and aerosols. However, climatic and biological consequences of some known LIP eruptions have not yet been explored. During the Carnian (Late Triassic) large volumes of flood basalts were erupted to form the so-called Wrangellia LIP (western North America). This huge volcanic province is similar in age to a major climatic and biotic change, the Carnian Pluvial Event (CPE), but no evidence of a causal relationship exists other than timing. Here we report a sharp negative δ 13 C excursion at the onset of the CPE recorded in organic matter. An abrupt carbon isotope excursion of ∼−4‰ occurs in terrestrial and marine fossil molecules, whereas total organic carbon records an ∼−2‰ shift. We propose that this carbon isotope negative shift was caused by an injection of light carbon into the atmosphere-ocean system linked to the eruption of Wrangellia flood basalts. This carbon-cycle perturbation occurs slightly before two major evolutionary innovations: the origin of dinosaurs and calcareous nannoplankton.

Palaeontology: Human footprints in Pleistocene volcanic ash

We have analysed three fossilized trackways of human footprints in a zeolite-rich pyroclastic flow dated to 385,000–325,000 years ago (kyr), discovered along the western margin of the Roccamonfina volcanic complex in southern Italy. We believe that these tracks are the oldest human footprints found so far and that they were made by hominids who had a fully bipedal, free-standing gait, using their hands only to steady themselves on the difficult descent.

Lavinipes Cheminii Ichnogen., Ichnosp. nov., A Possible Sauropodomorph Track from the Lower Jurassic of the Italian Alps

A new ichnotaxon is described from the Lower Jurassic (Upper Hettangian-Lower Sinemurian) carbonate tidal flats on the central-eastern Italian Alps. The narrow-gauge trackway is that of a large quadrupedal dinosaur. The pes is functionally tetradactyl with three rounded antero-medially directed digits, and the manus is pentadactyl. This quadrupedal form is close to Otozoum and Pseudotetrasauropus jaquesi both traditionally related to sauropodomorph trackmakers. The similarity with Otozoum is so marked that Lavinipes and Otozoum could be cogeneric. But the overall evidence today is that the Otozoum trackmaker was generally bipedal, whereas the trackmaker of L. cheminii is fully quadrupedal. The manual prints of L. cheminii show five short clawless digits and are different from the tetradactyl slender toed manual prints of Otozoum. The possible sauropodomorph affinity of the L. cheminii trackmaker is here discussed with an attempt to a revision of the Late Triassic-Jurassic tracks which have been traditionally related to sauropod and prosauropod.

The Devil's Trails: Middle Pleistocene Human Footprints Preserved in a Volcanoclastic Deposit of Southern Italy

Three fossilized trackways of human footprints were discovered in a pyroclastic flow dated to 385–325 ka, along the western margin of the Roccamonfina volcanic complex in Southern Italy. The pyroclastic flow is zeolite-rich and was probably emplaced at a relatively low temperature, forming a nonwelded pyroclastic deposit. The well-preserved footprints show the interesting strategies used by ancient humans in descending steep slopes. The footprints, short and very broad, are entaxonic, plantigrade, with an average length of 24cm and an average width of 10 cm. The three trackways are narrow with an oblique pace of about 60 cm and a stride of about 120 cm. If dating constraints are correct, the Roccamonfina human fossil footprints are the oldest known in Europe and among the oldest in the world. Moreover, they are preserved on a steep slope lying in a subaerial setting and are associated with handprints. For their potential in preserving evidence of behavior, these tracks provide unique insight into the activities of some of the earliest known Europeans.

A vertebrate nesting site in northeastern Italy reveals unexpectedly complex behavior for late Carnian reptiles

Abstract We interpret 13 large subcircular or horseshoe-shaped depressions discovered in Late Triassic peritidal carbonate rocks of the Dogna Valley in Udine Province, northeastern Italy, to be reptile nests. These trace fossils show truncation of strata, elevated ridges of massive sediment, and sediment infill within the depression differing in shape and sedimentary structures from the host sediment. The palynological assemblage of a shaly interbed close to the nest layer indicates a Tuvalian age (late Carnian). Archosaurian footprints, produced possibly by aetosaurs, are on a surface 130 cm above the nest-bearing layer. The trackmakers are considered the most probable nest makers.

SELECTED AMMONOID FAUNA FROM PRATI DI STUORES/STUORES WIESEN AND RELATED SECTIONS ACROSS THE LADINIAN-CARNIAN BOUNDARY (SOUTHERN ALPS, ITALY)

The ammonoid fauna of the Prati di Stuores/Stuores Wiesen section (Dolomites, north-eastern Italy) was studied in detail. This section was proposed as stratotype for the Carnian GSSP, with the first appearance of Daxatina cf. canadensis as primary marker, based on preliminary data. The validity of this proposal is confirmed by the present study, which integrates collections from the Prati di Stuores/Stuores Wiesen section and from others, particularly Bec de Roces (Passo Campolongo) and Antersass (Badia Valley). Ammonoids collected in these localities belong to three biostratigraphic units: regoledanus , canadensis and aon subzones. These subzones constitute, in the Southern Alps, the Ladinian/Carnian boundary interval. Regoledanus Subzone: the north American species Zestoceras enode is most probably documented in this biostratigraphic interval. Canadensis Subzone: the base is marked by the first appearance of Daxatina canadensis , and at least, another north American species, Daxatina laubei , seems to be present. Two species of Zestoceras were found: Z. barwicki e Z. lorigae sp.n. Two species o f Trachyceras , distinct from T. aon , are represented in the canadensis Subzone: T. muensteri and T. bipunctatum . These species predate the first appearance o f Trachyceras , justifying the canadensis Subzone to be included in the Carnian also on the basis of nomenclatural stability. Other significant taxa of this subzone are Rossiceras ? armatum and Sirenotrachyceras thusneldae . Aon Subzone: the ammonoid fauna of this subzone is extensively treated in existing literature and thus not further discussed. Taxonomical notes and stratigraphic consequences: the new subfamily Anolcitinae (family Trachyceratidae) is erected. At present, Frankites regoledanus , F. apertus and F. sp. A have been recognized in the Southern Alps. The lectotype of Ammonites ( Trachyceras ?) Regoledanus was defined. The latter species is exclusive of the regoledanus Subzone, whereas the distribution of the two other species encompasses the defined GSSP. The shell morphology of F. apertus and the north American species F. sutherlandi is identical. The suture line is also comparable, hence the two species are considered synonyms. This synonymy is relevant for long-distance correlations. The lectotypes o f Trachyceras ruturanum and T. laricum were also defined.

Magnetostratigraphy and biostratigraphy of the Middle Triassic Margon section (Southern Alps, Italy)

Abstract A magnetostratigraphic study has been performed on the paleontologically well constrained pelagic Middle Triassic (Lower/Upper Ladinian boundary) section at Margon (Trento, Southern Alps, Italy). Rock magnetic investigations indicate the presence of both, high and low coercivity minerals. Specimens subjected to progressive thermal demagnetization procedures show that nearly all of them exhibit a low temperature magnetization component, parallel to the present-day field before bedding correction, and a high temperature one, characterized by either positive or negative and opposite polarity, considered as the characteristic Triassic magnetization. The comparison of the Margon magnetic polarity zonation with those of two coeval sections poses some problems when ammonoid- and conodont-based stratigraphies have to be correlated. However, good correlation has been obtained for the recognized Middle Triassic ammonoid biozones in the Tethyan realm. Valuable data to the construction of a standard magnetostratigraphic and paleontological scale are contributed by the results from the Margon section.

REFINED AMMONOID BIOCHRONOSTRATIGRAPHY OF THE BAGOLINO SECTION (LOMBARDIAN ALPS, ITALY), GSSP CANDIDATE FOR THE BASE OF THE LADINIAN STAGE

A refined ammonoid biostratigraphy is reported for a critical interrval of the Bagolino section (Giudicarie Area, Northern Iraly), a candidate for the Anisian/Ladinian stage boundary. The Avisianum Subzone has been documented, and its boundary with the Crassus Subzone has been redefined, on the basis of new findings of Reitziites reitzi, Aplococeras aff. smithi, Aplococeras avisianum, Halilucites rusticus, Parasturia sp. and other significant ammonoids. Six potential criteria for the definition of the Anisian/Ladinian boundary can now be considered in this single stratigraphic section, so that the FO of Eoprotrachyceras curionii is no longer the unescapable choice at Bagolino. Despite several drawbacks, including the absence of palynomorphs and daonellid bivalves, the thermal history preventing the recovery of magnetic and isotopic signals, and a lower sedimentation rate with respect to many other sections of the Southern Alps, the Bagolino section is here accepted as stratotype for the Anisian/Ladinian boundary, but further paleontological and sedimentological studies should be considered.