Abstract

SIMON, María Edith. Dinosaur eggshells from the Allen Formation (Campanian-Maastrichtian), at Salitral Moreno, Río Negro Province, Argentina. Ameghiniana [online]. 2006, vol.43, n.3, pp.513-528. ISSN 1851-8044.

A detailed description of two morphotypes of dinosaur eggshells from Salitral Moreno, Rio Negro Province (Allen Formation, Upper Cretaceous) is presented. One of them is described as Patagoolithus salitralensis, a new oogenus et oospecies nov. belonging to the Megaloolithidae, and the second is referred as ?Faveoloolithidae, oogenus et oospecies indet. A detailed ultrastructural description of both morphotypes is provided, as well as, the chemical and mineralogical analysis of ?Faveoloolithidae oogen. et oospec. indet. In the studied sections, three eggshell-bearing levels were recognized. In the lower one (NH1) Patagoolithus salitralensis is associated to a diverse fauna of dinosaurs, chelonians and invertebrates, and the few shell fragments are dispersed, suggesting deposition in an alluvial plain or disintegrated eggs. In NH2 and NH3, only eggshells of ?Faveoloolithidae oogenus et oospecies indet. were found. NH2 shows lateral variations in the inferred degree of transport and density of the shell fragments in different sections. NH3 bears small shell fragments of the same morphotype decreasing in number towards the top. NH1 and NH3 bear rizolithes and alveolar structures, characteristic of calcretes, which could be indicative of palaeosoils.

Keywords : Eggshells; Dinosaurs; Histostructure; Microstructure; Río Negro Province; Upper Cretaceous; Argentina.