''Subtiliolithus'' is an

oogenus Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains ...

fossil egg Egg fossils are the fossilized remains of eggs laid by ancient animals. As evidence of the physiological processes of an animal, egg fossils are considered a type of trace fossil. Under rare circumstances a fossil egg may preserve the remains of ...

from the

Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians ...

of Mongolia and the

Ohyamashimo Formation The Ohyamashimo Formation(大山下層) is an Early Cretaceous (Albian) geologic formation in Japan. It has been dated to the early-mid Albian, between 112.1 ± 0.4 Ma and 106.4 ± 0.4 Ma. Dinosaur remains have been discovered from this formatio ...

of Japan. The eggs are notable for a very thin eggshell. It contains three oospecies: ''S. hyogoensis'', ''S. kachchhensis'' and ''S. microtuberculatus''. They were originally classified as a distinct oofamily, Subtiliolithidae, but numerous similarities to ''

Laevisoolithus ''Laevisoolithus'' is an oogenus of fossil egg. Its sole oospecies, ''L. sochavai,'' is native to the Nemegt Formation in Mongolia. ''Laevisoolithus'' is characterized by its thin, smooth eggshells. These eggs were probably laid by a bird or a s ...

'' 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 The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and c ...

birds.Kurochkin, E.N., S. Chatterjee, and K.E. Mikhailov. (2013) "An Embryonic Enantiornithine Bird and Associated Eggs from the Cretaceous of Mongolia." ''Paleontological Journal'' 47(11):1252-1269.

References

Egg fossils Fossils of Mongolia Maastrichtian life Nemegt Formation Fossil parataxa described in 1991 {{eggshell-stub