On the tracks of ancient reptiles

In March 2010 the discovery of a new site with fossil footprints from the Triassic in the province of Trentino was announced, adding an ulterior chapter to the rich geological and paleontological history of the pale mountains - the Dolomites.
These rich fossil deposits, the geology and the significance for the development of geological sciences of this area were reasons to insert the Dolomites in June 2009 in the list of World Heritage sites.

The first recognition of fossil traces of vertebrates dates back to 1800-1802, when a young student discovered dinosaur footprints in the Jurassic sediments of Connecticut.
But ichnology, the study of fossil tracks, was not establishes as independent science until 1950. Considering this, the Dolomites have played an important role in the history and development of ichnology.

In 1891, in a sandstone quarry near the villages of Glen and Montan, Province of Bolzano, the amateur naturalist F. Gasser picked up a strange piece of rock. He sent the presumed fossils to the Austrian palaeontologist Ernst Kittel, who recognizing similarities between the imprints on the rock with the footprints of a reptile (Chirotherium) discovered in 1833 in Triassic sediments (Buntsandstein) of Thuringia. Kittel in the same year published a brief account of the discovery in the journal of the Austrian Tourist Club - the first report of fossil tracks found in South Tyrol.

The notice (and translation) of the discovery of the reptilian trackway as published in the journal of the 'Österrischen Tourist Clubs "in 1891:

“Saurierfährte von Bozen: Aus der Umgebung von Bozen kennt man schon seit einiger Zeit Sandsteine, welche den Porphyr überlagern, und welche in gewissen Lagen ganz ähnliche Erscheinungen zeigen, wie die Buntsandsteine von Hessberg in Thüringen, nämlich auf den Schichtflächen erscheinen "Rippelmarken" (durch Wellenschlag oder Wind erzeugte wellenförmige Furchen), ausgefüllte netzförmige Trockenrisse und Fährten unbekannter Saurier, die man Chirotherium und Saurichnites nennt. Wenn nun auch diese Erscheinungen aus der Gegend von Bozen angeführt werden, so gelangen solche Stücke doch sehr selten in die Museen, was gerade nicht für ihre Häufigkeit spricht. Im naturhistorischen Hofmuseum befinden sich z.B. nur Trockenrisse von Saltern, dann Rippelmarks von eben demselben Orte, die ziemlich undeutlich sind. Eine unzweifelhafte "Saurierfährte" aus einem Steinbruch am Westgehänge des Mte. Cislon etwa zwischen Gleno und Montan nächst Neumarkt bei Bozen hat Herr Dr. F. Gasser in Atzenbrugg an die Section eingesendet. Dieselbe ist freilich nicht so gut erhalten, wie die Stücke von Hessberg, jedoch immerhin ist der erhabene Abdruck einer gefingerten Tatze erkennbar. Es wäre nur zu wünschen, dass uns etwas mehr von diesen Funden zukäme, damit genauere Vergleiche mit besser bekannten anderen Saurierfährten ermöglicht würden.
Die Fundstelle am Hessberg gehört bekanntlich zum "Buntsandstein", dagegen rechnet man die Bozner Sandsteine zum "Grödener Sandstein", welcher für älter als Buntsandstein gehalten wird und daher meist für "oberpermisch" gilt. Weitere Mittheilungen derartiger Funde sind sehr erbeten.”

"Reptile tracks of Bozen: In the vicinity of Bozen there are known sandstones, which are superimposed on the porphyry, and which in certain layers show properties that are very similar to the ones of the red sandstone of the Hess Mountains in Thuringia, so there appear on the layer surfaces "ripple marks" (wave-like furrows generated by water or wind), reticulate cracks and tracks of unknown reptiles, called Chirotherium and Saurichnites.
Even if these peculiarities are known from the area of Bozen, examples of these features are very rare in the museums, which speak not for their frequent discovery.
In the natural history museum for example are known only mud-cracks of the area of Saltern, and then indistinct ripple marks from the very same place.
An unquestionable "reptilian track" was send to the section by Dr. F. Gasser from Atzenbrugg, it comes from a quarry on the western flank of Mount Cislon, approximately between Gleno and Montan, in the vicinity of Neumarkt, near Bolzano. The same is certainly not as good as the specimens of the Hess Mountains, but after all a fingered paw is recognizable. I only wish that some more of these findings are send to us, it would allow more accurate comparisons with other better-known reptilian tracks.
The site in the Hess Mountains, as it is well known, belongs to the "Buntsandstein", but the sandstones of Bozen are included in the "Grödener Sandstone", which is considered to be older then the “Buntsandstein” and attributed to the "Upper Permian".
Other communications of such finds are much appreciated."

Only years later, in the summer of 1931, Gualtiero Adami, an engineer and employee of the Natural History Museum of the former Province of Venezia Tridentina, discovered during an excursion near the village of Piné a rock on which, at is seemed, was engraved a figure similar to a lizard.
The fossil was consigned into the custody of local museum and later studied by the geologist Giorgio del Piaz. During a meeting of the Italian Society for the Advancement of Science in September of that year he announced the preliminary study and the "discovery of a new genus, likely a paleolacertide, collected near Piné and found in a thin bed of tuff, interbedded within the Permian porphyry”.
The fossil also confirmed the hypothesis that reptiles were the authors of the footprints found in the same or overlying formations. The fossil, however, after these announcements was not studied further and put aside, first treasured in Milan, then in 1938 brought to Padua. In 1942 the palaeontologist Giambattista Dal Piaz briefly mentions the finding, referring to it as "a beautiful lizard-like reptile, certainly from a terrestrial habitat.”
The fossil finally was (and still is) exposed in the museum of the Geological Institute of Padua with the denomination “Tridentinosaurus antiquus by GB Piaz”, but only in 1959 the specimen is described scientifically by the palaeontologist Piero Leonardi, who recognizes it’s significance, as a vertebrate in peculiar preservation condition (skeletal remains surrounded by a carbonaceous patina of soft parts) and the oldest body fossil of the Southern Alps. It’s suggested by some authors, based on the preservation of the fossil, that the animal was killed during a volcanic eruption by a pyroclastic surge.

Fig.2. Tridentinosaurus.

For further signs of reptilian activity in the geological past of the Dolomites, we have to wait until 1946, when the geologist Piero Leonardi begins to study the Permian flora of the Val Gardena sandstone, formation with important fossil bearing sites known since 1877.
Intrigued by an account of the fossil flora of the Bletterbach canyon near the villages of Aldein and Radein, he contacts the author, the engineer Leo Perwanger. Together during field excavations they find more fossils, and some plates with the trackways of reptiles. After some supplementary field season in 1951 Leonardi publish the results, and realizes the importance of the site.

He continues the research and is joined by the palaeontologist and expert for fossil trackways Accordi and his students. Leonardi in the summer of 1951 discovers an ulterior site, on the flank of Mount Seceda in the Val Gardena, where a large succession of Permian yellow to red sandstones is outcropping. Yet other sites were discovered in 1955, along the road between Pause and Doladizza on the left side of the Etsch-Valley, and the following year near the pass of San Pellegrino.

Fig.3. Tetrapod tracks and skin impressions (right below). Strati di Werfen - Formation, Triassic - Passo Palade.

Research in the gorge of Bletterbach is continuing from 1973 until today. The creek on the bottom of the gorge has carved into the side of the mountain a large geological scar, offering the possibility to observe and cross the entire upper Permian and lower Triassic sedimentary succession. From here comes one the most comprehensive footprints collection of Permian terrestrial reptiles, with so far 9 ichnospecies comprising 8 ichnogenera, some of them attributed to Synapsids, which makes this site even more exceptional.

Fig.4. Visit to the gorge of the Bletterbach (BZ).

References:

AVANZINI, M. & WACHTLER, M. (1999): Dolomiti La storia di una scoperta. Athesia S.a.r.l. Bolzano: 150
AVANZINI, M. & TOMASINI, R. (2004): Giornate di Paleontologia 2004 Bolzano 21-23 Maggio 2004 Guida all´escursione: la gola del Bletternach. Studi Trentini di Scienze Naturali - Acta Geologica Supplemento al v.79 (2002):1-34
LEONARDI, G. (2008): Vertebrate ichnology in Italy. Studi Trent. Sci. Nat., Acta Geol., 83 (2008): 213-221