Field of Science

Dinosaurs rewrite the palaeogeography of the Tethys

During the First World War notable effort was invested in the construction of streets and ways to enable the save transport of supplies to the frontline in the Dolomites. In 1917 in the Pasubio Massif (North of Vicenza) a mule-track with 50 tunnels in the 712m high cliffs of the Hauptdolomite Formation was excavated.

Almost 70 years later, during an excursion the geologist Marco Avanzini noticed on the roof of one of the galleries a number of bulges immediately attributed to dinosaur footprints preserved as natural casts.
Many dinosaurian footprints were known from the H
auptdolomit, all preserved in large blocks felt from the cliffs, but this was the first record of tracks found in situ and stratigraphic sequence.
Large theropods tracksites datable to the Triassic were discovered in the Dolomites at the Tre Cime di Lavaredo, in the surroundings of the city of Trento and in localities of the more eastern situated Carnia, also small theropods and prosauropod footprints occur in Carnia and in the Dolomites.

The 11 known footprints of the Pasubio Massif represent three morphotypes, one type is attributed to a sauropodomorpha trackmaker, and the other two types are attributed to theropods of variable size. The conserved stratigraphic succession, and the recovery of conodonts as guide fossils, enabled to date exactly the surface with the imprints to the Norian (211 to 206 million years).

In a recent press release the notice of three new imprints, discovered in the same region, but of different age (Rotzo Formation, Pliensbachian 183 - 189 Ma) was reported.

These imprints, attributed to theropods, add an ulterior ichnosite to the long Italian record.

Even if the first dinosaur footpr
int in Italy was described by the palaeontologist Friedrich von Huene in 1941 from Carnian sediments of Mount Pisano in Tuscany, this discovery was for long time considered more an extraordinary case then the rule.
But the discovery between 1992 and 2000 of many sites with dinosaur footp
rints demonstrated that many old preconceptions have to be reconsidered.

Fig.1. Examples of Italian dinosaur tracks recovered during quarrying activity at the quarry of Colmar, from the peninsula of Gargano, Calcari di Bari-Formation, Lower Cretaceous (Valanginian-Hauterivian, ca. 140-130 million years). First two specimens tridactyl footprints attributed to theropods, last probably a chubby footprint attributed to an ankylosaurid dinosaur.

The presence of dinosaurs can have a great impact on the proposed palaeoenvironments and the palaeogeography reconstructions of the Mesozoic Tethys Ocean.
The geological evidence suggested that the northern area of the Tethys was mainly a monotone, shallow marine environment with a vast carbonate platform surrounded by the Ocean. Classic reconstructions placed a deep-sea trough, penetrating from the Far East to the Alpine realm, between the platforms and the southern border of Eurasia.

The continuous and spatial distribution of ichnosites is however compelling evidence that the carbonate platforms of the Tethys surrounded wide land areas and not only small islands as previously thought. The landmasses acted probably as temporary bridges that connected Laurasia and Gon
dwana, allowing migrations. During periods of marine transgression these corridors got interrupted, forcing the evolution of endemic faunas in the now isolated central Tethys landmasses (see also the Hateg Biota).

Fig.2. The reconstructed extent of the carbonate platforms in the Periadriatic area during the Mesozoic: facies distribution in the Periadriatic area during the Norian/Rhaetian. Points indicate the sites with dinosaur fossils. The wide Triassic carbonate platform collapsed during the Jurassic, and became dissected by the Lombardy and Slovenian-Belluno-Ionian Basins, in this phase the dinosaur ichnological fossils were located only on the Trento Platform (DALLA VECCHIA 2008).

Based on the presupposed affinities in morphological characters of the Italian tracks to tracks recovered on the European mainland, and the temporal occurence of the old and new studied ichnostes, Avanzini proposes an alternative model to the east-west sea-branch of the Tethys Ocean. He reconstructed a more stable and long-lasting land corridor (until ca. 160 Ma) extending much more to the north of the Tethys Ocean, connecting the landmasses to the southern border of Eurasia.
However the last claim is still to be proven by further evidence, considering also that ichnites represent a polyphyletic "taxon" and the inferred relationships are thus questionable.

Nevertheless the possible use of dinosaurs in palaeogeography remains still intriguing.


BELVEDERE, M.; AVANZINI, M.; MIETTO, P. & RIGO, M. (2008): Norian dinosaur footprints from the "Strada delle Gallerie" (Monte Pasubio, NE Italy). Studi Trent. Sci. Nat., Acta Geol.(83): 267-275

DALLA VECCHIA, F.M. (2003): Dinosaurs of Italy. C.R. Palevol 2: 45 - 66
DALLA VECCHIA, F.M. (2008): The impact of dinosaur palaeoichnology in palaeoenvironmental and palaeogeographic reconstructions: the case of the Periadriatic carbonate platforms. ORYCTOS (8): 89 - 106

PAVIA, M. & ZUNINO, M. (2009): Giornate di Paleontologia IX Edizione - Apricena (FG), 28-31 maggio 2009 - Guida alle escursioni 30 e 31 maggio 2009.

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