MEGALOOLITHID EGGS AND NESTS FROM THE LATE MAASTRICHTIAN OF SEBES AREA (TRANSYLVANIAN BASIN, ROMANIA)

MATYAS VREMIR; DANIEL BARTA; M. S. FERNÁNDEZ; DAN GRIGORESCU; TOTOIANU; WATANABE; MARK NORREL

Caparica

Simposio; VI Symposium of Eggs and babies; 2017

Late Cretaceous (Maastrichtian) megaloolithid dinosaur eggs are well known from a number of localities in the Hateg Basin, south-west Romania. Four sites, namely Tustea, Livezi, Vadu and Totesti, provided data on egg and clutch/nests morphology, egg-clusters distribution, ootaxonomy and possible identity of parent animals. Most of megaloolithid eggs from Hateg basin have been assigned or conferred to M. siruguei oospecies, but in Totesti locality have been described several eggs with titanosaurs embryos inside, which have been related to the same oospecie from Auca Mahuevo. These eggs have been described as spherical to sub-spherical in shape, 14 to16 cm in diameter, exhibiting profuse nodular ornamentation and shell thickness of 2,2 to 2,8 mm (average 2,4 mm). Numerous egg-clutches and nests were documented, particularly at Tustea nesting-site, were hatchling or neonate hadrosauroid bones were found closely associated with the eggs/nests. Controversies regarding the parent animals in the Hateg nesting-sites are an ongoing topic, and indeed, a clear answer is impossible to obtain without diagnostic in-ovo embryonic remains. However, there are not too many choices: besides the already mentioned and rare hadrosauroids (Telmatosaurus) the titanosaurids (Magyarosaurus, Paludititan) are rather frequent, alongside numerous rhabdodontid (Zalmoxes) fossils. Given the relative frequency of various unrelated dinosaur groups, their abundance in certain paleoenvironmental settings, and distribution of egg/nesting-sites, may indicate homoplasy ? respectively a certain degree of convergence in egg or nest morphology and nesting behaviour within a range of dinosaur taxa. A recently discovered late Maastrichtian megaloolithid egg/nesting site in SW Transylvania near Sebes, outside the Hateg basin, provide new data regarding the megaloolithid ootaxonomic diversity, nesting behaviour and possible parent animals identity. Several egg-clusters/clutches and nest structures were identified, and the preliminary evaluation, indicate the presence of isolated or grouped megaloolithid eggs, distributed in at least three egg-horizons, in brick-red silty-claystone flood-plain unit. The clusters may contain up to 24 eggs, with grouped-linear arrangement, sometimes in two or even three levels. Majority of egg /clusters are laid on the ground surface or shallow pits, being surrounded by numerous rhysolites/shrub roots. A pit-like nest structure on sandy substrate, containing a closely packed group of eggs is also documented. The megaloolithid eggs are sub-spherical in shape (many deformed/compressed), with diameters of 13 to 16 cm (volume up to 1480 ccm), showing very fine compactituberculate ornamentation, tubospherulithic morphotype, tubocanaliculated pore canal system, egg-shell thickness range in 0,7-0,9 mm and 1,4-1,6 mm respectively. Preliminary data indicate the presence of two nest-structure types, two egg-shell thickness classes and possibly two different parent animals.