ANALYSIS OF DINOSAUR EGGSSHELLS OF ALLEN FORMATION, UPPER CRETACEOUS OF THE RIO NEGRO PROVINCE (CAMPANIAN-MAASTRICHTIAN): USEFULNESS OF MACROCHARACTERS OF PARATAXONOMIC INTEREST

The present study is a further contribution to the parataxonomy knowledge of dinosaur eggshells from Salitral de Santa Rosa and Salitral Ojo de Agua, Rio Negro province, Argentina. We studied 4469 fragments of dinosaur eggshells Allen Formation, Upper Cretaceous (Campanian-Maastrichtian). Twelve of these shells were subject to a principal component analysis (PCA) to classify and establish the relationships between characters commonly used in parataxonomic classifications. We studied under binocular scope 4264 eggshells (BL), 57 eggshells under transmitted light microscope (TLM) and polarized light microscope (PLM), 14 eggshells under scanning electron microscope (SEM). We identified two main groups, type 1 eggshells related to the oofamily Megaloolithidae with five subtypes and type 2 eggshells, with no subtypes assigned. Relevant traits found with the ACP study were: shell thickness, the width of the shell units, the diameter of the nodules, and the diameter of the mamila. Different types of eggshells found were compared with various ootaxa from South America and other regions of the world.