Timeline of egg fossil research

=== Late Paleolithic to early Neolithic === • Mongolians fashioned fossil dinosaur eggshell into jewelry. Precolumbian North America • A common theme in Navajo stories about Water Monsters involve the human theft of Water Monster eggs or young and the angry Monsters pursuing humanity through a series of worlds. Stories like this influenced the Navajos to fear large fossil bones, which they felt shouldn't be disturbed, because doing so might awaken the enraged ghosts of the Water Monsters, who might resume their rampage with apocalyptic results. Stories like this may have been based on the discovery of fossil eggs in western North America. Fossil eggs and nests from this region that may have inspired the legend were left behind by creatures like possible aetosaurs, giant condors, duck-billed dinosaurs, possible phytosaurs, large theropods, and sea turtles. ==19th-century paleontology==

'' egg. === 1859 === • The first scientifically documented dinosaur egg fossils were discovered in southern France by a Catholic priest and amateur naturalist named Father Jean-Jacques Pouech. These fossils were large chunks of eggshell that date back to the Late Cretaceous. Pouech mistook them for the shell of a giant bird's eggs. === 1869 === • French geologist Philippe Matheron made a fossil discovery in the same general region as Pouech. Matheron discovered the fossil bones of an animal he named Hypselosaurus. Matheron thought Hypselosaurus to be a crocodile-like animal, but it is now recognized as a long-necked herbivorous sauropod dinosaur. Eggshell fossils were found associated with the remains. Matheron presented the shell fossils to the director of comparative anatomy at Paris' Natural History Museum, Paul Gervais. Gervais examined thin sections of the shell fossils and compared them with similar thin sections of eggs laid by modern birds and reptiles. He found them to be most similar to turtle eggs, but recognized that since dinosaur eggs had not yet been described scientifically, he could not rule out that possibility. ==20th-century paleontology==

=== 1913 === • While prospecting on the Blackfoot Reservation of northern Montana on behalf of the National Museum of Natural History, Charles W. Gilmore found a deposit of apparent freshwater clam fossils. • Karl Hirsch disputed Romer and Price's claim to have discovered a Permian hard-shelled egg, since the fossil in question didn't show evidence for the calcite that should have composed the shell. Hirsch found enough phosphorus in the object's outer layer to propose that the fossil was actually an egg, with a leathery shell. • Erben and others found isotope ratios of Carbon and Oxygen in French dinosaur eggs similar to those found in Mongolian dinosaur eggs by Folinsbee and others in 1970. The ratios are indicative of a diet of C3 plants and hot living conditions. === 1991 === • Jim Haywood and others were studying the nests of ground-nesting gulls buried by the Mount St. Helens eruption. They found that the volcanic ash was acidic enough to dissolve most of the eggshell in only two years. • Sarkar found isotope ratios of Carbon and Oxygen in Indian dinosaur eggs similar to those found in Mongolian dinosaur eggs by Folinsbee and others in 1970. The ratios are indicative of a diet of C3 plants and hot living conditions. Early to mid-1990s • Russian paleontologist Konstantin Mikhailov brought attention to Zhao's classification system for egg fossil in the English language scientific literature. ==21st-century paleontology==

''. === 2009 === • Steve Etches, Jane Clarke, and John Callomon reported the discovery of eight clusters of ammonite eggs in the Lower and Upper Kimmeridge Clay of the Dorset Coast in England. The eggs are subspherical to spherical in shape. Some are isolated but some were also found in association with the shells of perisphinctid ammonites. They were interpreted by the researchers as ammonite eggs sacks and are the best preserved specimens of such known to science. The parents of the egg sacks are thought to be two local ammonite genera co-occurring with the eggs, Aulacostephanus and Pectinatites. • Description of dinosaur egg fossils from the late Early Cretaceous Chaochuan Formation (Zhejiang, China) is published by Zhang et al. (2019), who name a new ootaxon Multifissoolithus chianensis. • Dinosaurs eggs assigned to the oofamily Dendroolithidae are described from the Late Cretaceous Zhaoying Formation (China) by He et al. (2019), who name a new ootaxon Pionoolithus quyuangangensis. • Dinosaurs eggs assigned to the oofamily Faveoloolithidae are described from the Upper Cretaceous (Coniacian–Santonian) siltstones within the Daeri Andesite of the Wido Volcanics (South Korea) by Kim et al. (2019), who name a new ootaxon Propagoolithus widoensis. ==See also==