First record of Faveoloolithidae eggshells from the late Maastrichtian of the Lago Colhué Huapi Formation, Golfo San Jorge Basin, Argentina

Abstract

This study reports the first occurrence of Faveoloolithidae eggshells from the “upper section” (late Maastrichtian) of the Lago Colhué Huapi Formation, Chubut Group, in the Golfo San Jorge Basin, Argentina. A total of 161 eggshell fragments were examined using a binocular microscope, petrographic microscope, and scanning electron microscope. The specimens show morphological features consistent with the oofamily Faveoloolithidae, including a dinosauroid-spherulitic basic organization, a filispherulitic structural morphotype, and a multicanaliculate pore system. However, as evidenced by other South American records, their well-developed external ornamentation and greater thickness distinguish them from other ootaxa within the oofamily; therefore, they are assigned to Faveoloolithidae indet. These eggshell fragments were recovered within deposits interpreted as low-energy, shallow water bodies, developed in floodplain environments near the coastline. These levels are characterized by a remarkable abundance of hadrosaurid remains and, to date, the absence of sauropod fossils. Although an association with hadrosaurids might be suggested, a titanosaurian affinity cannot be excluded, as these sauropods are traditionally linked to Faveoloolithidae eggshells. This uncertainty reflects the complexity of taxonomic assignments in fragmentary oological records.