What is "subtiliolithus"

Subtiliolithus is an oogenus of fossil egg from Nemegt Formation of Mongolia. The eggs are notable for a very thin eggshell. It contains two oospecies: S. kachchhensis, and S. microtuberculatus. They were originally classified as a distinct oofamily, Subtiliolithidae, but numerous similarities to Laevisoolithus have led to their reclassification as Laevisoolithid eggs. A complete skeleton of Nanantius valifanovi was found associated with Subtiliolithus eggshells, indicating that the oogenus represents eggs of enantiornithine birds.