Aleksandar Mezga

FIRST RECORD OF DINOSAURS IN THE LATE JURASSIC OF THE ADRIATIC-DINARIDIC CARBONATE PLATFORM (CROATIA)

Abstract All previously known dinosaur remains on the Adriatic-Dinaridic carbonate platform (ADCP) were described from Cretaceous deposits. A new trackbearing locality is late Tithonian in age and represents the oldest evidence of dinosaurs on the ADCP. The site is in an active quarry near the village of Kirmenjak in western Istria. Almost a thousand sauropod footprints including 23 single trackways have been found on the outcrop. Oval impressions represent pes prints, and horseshoe-shaped impressions represent manus prints; pes prints are 23 to 52 cm long. Calculated heights at the hip range from 153 to 306 cm. The main direction of dinosaur movement was toward the northeast, and some of the individuals were moving together. The trackways show a characteristic narrow gauge, and pace and stride lengths indicate a slow walk. The footprints are similar to Parabrontopodus ichnogenus, and the ichnocoenosis could be assigned to the Brontopodus ichnofacies. The presence of the sauropods on the Adriatic-Dinaridic carbonate platform during the Late Jurassic could be explained by connection with the African continent via its southern margins during emersion.

A new dinosaur tracksite in the Late Albian of Istria, Croatia

A new site with dinosaur footprints has been found in the upper Albian sediments of Istria, Croatia. The site was discovered near the city of Pula, at the Zlatne Stijene locality. The carbonate succession of the Zlatne Stijene locality is characterized by thin bedded limestones deposited in peritidal and foreshore environments. The microfossil assemblage found at the site indicates a late Albian age. One clearly distinguishable footprint and four indeterminate rounded tracks were discovered at the investigated outcrop. The footprint is tridactyl and belongs to a medium-sized bipedal theropod dinosaur of approximately 3 meter in length. Regarding dimensions and morphology it is closely related to the other late Albian theropod footprints from the Adriatic-Dinaridic carbonate platform (ADCP). The Zlatne Stijene locality fits with the Brontopodus ichnofacies concept.

NEW DINOSAUR TRACKSITE IN THE LATE JURASSIC OF KIRMENJAK QUARRY (ISTRIA)

A new dinosaur tracksite was found in the Kirmenjak quarry in Istria. It is located about one kilometre from an already existing tracksite. The footprints are placed on a slightly inclined bedding plane at the base of the succession represented by heavily stylolitised limestones of the Kirmenjak informal lithostratigraphic unit. The age of the limestones is late Tithonian. Fifteen footprints of circular shape with no clear digit or claw impressions were found at the site and are interpreted to have been formed on a tidal flat during a sea-level fall. All of the footprints belong to sauropod dinosaurs. Pes prints are circular to elliptical in shape, whereas manus prints are more elliptical and of smaller size. The average length of the pes prints is 55 cm, which would correspond to a sauropod of approximately 16 meters in length. The trackway is of narrow-gauge type, where the internal trackway width often has a negative value. The length of the strides indicates slow movement of the individual with a speed of less than 2 km/h. Based on stratigraphic position and footprint morphology, the new and the pre-existing tracksites represent the same trackbearing layer.

DIGITAL MODELLING OF THE LATE ALBIAN SOLARIS DINOSAUR TRACKSITE (ISTRIA, CROATIA)

Abstract: The late Albian Solaris dinosaur tracksite in Istria (Croatia), which is characterized by an abundance of theropod and sauropod footprints, was surveyed using a combination of GNSS georeferencing, terrestrial laser scanning, and photogrammetry. The entire outcrop was digitally captured with millimeter-scale resolution and high spatial accuracy, allowing both outcrop-scale observations and analysis of fine morphological features at the scale of individual footprints. Quantitative ichnological data acquired from the digital model is equivalent to published results based on traditional methods. Inspection of the digital outcrop model has revealed a number of new tridactyl footprints previously undocumented at the Solaris tracksite. All of the newly identified prints are exceptionally shallow and bear characteristics typical of medium-sized bipedal theropod dinosaurs. The study testifies to how approaches involving digital modelling are able to supplement and improve upon traditional methods of field observation and help revise previous ichnological studies. They can be a particularly effective solution for studying complex, heavily trampled tracksites with highly variable print depths and preservation.

Dinosaur footprints in the Upper Hauterivian deposits of the Palud Bay in Istria, Croatia

Sixteen dinosaur footprints are exposed along the upper-bedding plane of a single Upper Hauterivian limestone layer in the Palud bay (western Istria, Croatia). This distinct footprint-bearing horizon is part of the thick Mesozoic Adriatic-Dinaridic Carbonate Platform stratal succession. Strata at the Palud site are characterized by peritidal (shallow subtidal to intertidal) limestone with several shallowing-upward cycles composed of mudstone, peloidal wackestone/packstone, peloidal packstone/grainstone and fenestral mudstone/wackestone with common geopetal infill. The Late Hauterivian age of these deposits is determined from their microfossil assemblage, which is dominated by ostracods, benthic foraminifera and calcareous green algae Dasycladales. The Palud site dinosaur footprints are circular to elliptical in shape, with no clearly visible digit impressions (except for one questionable example), and are rather large with average length of 30 cm. Most footprints have a well-defined expulsion rim that represents displacement and compression of soft, waterlogged sediment substrate by the weight of the dinosaur. All of the footprints are of nearly same shape and size, which indicates that they were produced by the same kind of tracemaker – likely a sauropod dinosaur. These animals left their footprints on top of a shallowing-upward succession of an intertidal environment during a short subaerial exposure of fine-grained carbonate sediment.

Stable isotope analysis of Upper Tithonian limestones with dinosaur footprints from Kirmenjak quarry (Istria, Croatia)

The Kirmenjak locality of western Istria, Croatia, represents the oldest evidence of a dinosaur presence on the Adriatic- Dinaridic Carbonate Platform (ADCP). In a quarry at this locality, almost a thousand sauropod footprints are recognized in one distinctive trackbearing horizon within the Upper Tithonian limestones. The stable isotopes of oxygen and carbon, in conjunction with microfacies analysis of carbonate rocks exposed in this quarry, unravel details about the marginal marine or coastal environments in which sauropods left their footprints. Rocks from the trackbearing horizon, and laterally adjacent area, represent intertidal fenestral mudstones that form the top of a shallowing- upward succession, capped with a thin peloidal packstone/grainstone layer and overlain by subtidal mudstone. The formation and preservation of footprints was favoured by short-duration exposure of muddy sediment and its rapid burial beneath more mud. The isotopic composition of the sample from the trackbearing horizon is not substantially different from those of an adjacent area without footprints and from the overlying mudstone. Stable isotope analysis supports petrographic observations that the conditions on the carbonate tidal fl at during formation of rocks with dinosaur footprints were not unique. Documented variations in stable isotope compositions refl ect minor differences in the depositional and diagenetic history of the Kirmenjak quarry succession.