Naslov
Dinosaur tracks as an evidence for the terrestriality in the Late Jurassic sediments of Istria, Croatia

Autori
Mezga, Aleksandar ; Bajraktarević, Zlatan ; Cvetko Tešović, Blanka ; Gušić, Ivan

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
22nd IAS Meeting of Sedimentology, Opatija - September 17-19, 2003, Abstracts Book / Vlahović, Igor - Zagreb : Institute of Geology-Zagreb, 2003, 126-126

Skup
22nd IAS Meeting of Sedimentology

Mjesto i datum
Opatija, Hrvatska, 16.09.2003. - 19.09.2003

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
dinosaur; footprints; Late Jurassic; Istria

Sažetak
All fossil remains of dinosaurs on the Adriatic carbonate platform (which is now outcropping along the eastern coast of the Adriatic Sea) came from the Cretaceous sediments ; the oldest find being of Hauterivian age (Dalla Vecchia et al. 2000). Recently, a new locality with the dinosaur footprints have been discovered. The site is situated in an active quarry front near the village Kirmenjak in the central Istria.. The age of the trackbearing sediment is Upper Tithonian and represents, so far, the oldest proof of dinosaur presence on the Adriatic carbonate platform. The site consists of the peritidal limestones which represent the lithostratigraphic unit "Kirmenjak stylolitised micrites" (Velić & Tišljar 1988). This unit represents the first part of the second transgressive-regressive megasequence of Jurassic - Cretaceous shallow-water carbonates of Western Istria (Velić et al. 1995a) and is composed of typical shallowing-upward cycles, ranging from black-pebble breccias and light-colored stylolitized mudstones to fenestral mudstones and grainstones. The Upper Tithonian age was proved by microfossil assemblage found in stylolitised mudstones: Clypeina jurassica FAVRE, Salpingoporella annulata CAROZZI, Campbelliella striata (CAROZZI) and Favreina sp (Velić et al. 1995b). The footprints are situated on the top of a fenestral mudstone layer that could be interpreted as an emersion surface ; the intertidal environment and influence of meteoric water are indicated not only by fenestral fabrics but also by geopetal infillings of cavities, desiccation cracks and the presence of dinosaur footprints. The site is very rich in footprints, some few hundreds of them have been found on the outcrop. The majority of the footprints show an oval or horse-shoed shape without clearly visible digit impressions and are relatively shallow (10-20 mm). Although the state of preservation is far from ideal, it is concluded that the prints, regarding morphology, belong to the sauropod dinosaurs. The oval prints would respond to the pes prints and the horse-shoe shaped ones to the manus prints. The footprints are of various dimensions ; manus prints show the length range between 100 - 250 mm, pes prints between 350 - 500 mm. The calculated height at the hip ranged between 2.06 - 2.95 m. Dozens of trackways can be observed on the outcrop and they frequently overlapp. There are also some areas which are heavily trampled by sauropod foots. The main direction of dinosaur movements was toward E-NE and because there are a number of parallel trackways it could be concluded that some of the individuals were moving together (indication of gregarious behavior). A large number of the trackways disappeared below the quarry surface and probably extend further. Some of the trackways show characteristics of a narrow-gauge type, some of them are slightly wider but none shows the wide-gauge character. The pace and stride lengths indicate slow walk of the individuals. The ichnocoenosis from this outcrop could be assigned to the Brontopodus ichnofacies which is characterized by sauropod footprints in the carbonate platform environment (Lockley et al. 1994). The presence of the large sauropod dinosaurs on the Adriatic carbonate platform during the Upper Jurassic could be explained by its connection with the African continent via its southern margins. The sauropods could have migrated into the area during an emersion phase when the platform was exposed to subaeric conditions. There had to be a widespread continental area in the hinterland in order to support the survival of such large terrestrial herbivores as were the sauropod dinosaurs. REFERENCES Dalla Vecchia, F.M., Tarlao, A., Tentor, M., Tunis, G. & Venturini, S. (2000) First record of Hauterivian dinosaur footprints in southern Istria (Croatia). Proceedings of the Second Croatian Geological Congress, Cavtat 2000, 143-149. Lockley, M. G., Hunt, A. P. & Meyer, C. A. (1994) Vertebrate tracks and the Ichnofacies Concept: implication for paleoecology and palichnostratigraphy. In: The Paleobiology of Trace Fossils (Ed. by S. Donovan), pp. 241-268, Wiley & Sons, New York. Velić, I & Tišljar, J. (1988) Litostratigrafske jedinice u dogeru i malmu zapadne Istre (zapadna Hrvatska, Jugoslavija). Geološki vjesnik 40, 149-168. Velić, I., Tišljar, J. & Matičec, D. (1995a) Opći prikaz geološke građe Istre (A Review of the Geology of Istria). In: Excursion Guide Book, The First Croatian Geological Congress, Opatija 1995 (Eds. by I. Vlahović & I. Velić), pp. 5 - 30, Institute of Geology, Zagreb. Velić, I., Matičec, D., Vlahović, I. & Tišljar, J. (1995b) Stratigraphic Succession of Jurassic and Lower Cretaceous Carbonates (Bathonian - Upper Albian) in Western Istria (Excursion A). In: Excursion Guide Book, The First Croatian Geological Congress, Opatija 1995 (Eds. by I. Vlahović & I. Velić), pp. 31 - 66, Institute of Geology, Zagreb.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA