Dinosaur eggs are the organic vessels in which a dinosaur embryo develops. When the first scientifically documented remains of non-avian dinosaurs were being described in England during the 1820s, it was presumed that dinosaurs had laid eggs because they were reptiles. In 1859, the first scientifically documented dinosaur egg fossils were discovered in France by Jean-Jacques Poech, although they were mistaken for giant bird eggs.
The Puerto Yeruá Formation is a Late Cretaceous geologic formation in the Paraná Basin, pertaining to Entre Ríos Province, Argentina. Dinosaur remains are among the fossils that have been recovered from the formation, as well as egg fragments and fossilized wood.
The Sigou Formation is a Late Cretaceous geologic formation in China. Fossil dinosaur eggs have been reported from the formation, including Dictyoolithus.
Dictyoolithus is an oogenus of dinosaur egg from the Cretaceous of China. It is notable for having over five superimposed layers of eggshell units. Possibly, it was laid by megalosauroid dinosaurs.
Cairanoolithus is an oogenus of dinosaur egg which is found in Southwestern Europe. The eggs are large and spherical. Their outer surface is either smooth, or covered with a subdued pattern of ridges interspersed with pits and grooves. Multiple fossil egg clutches are known but the nest structure is unclear.
Megaloolithus is an oogenus of dinosaur egg. Some eggs belonging to this oogenus may have been laid by the titanosaur Hypselosaurus. They are known for having thick eggshells, at least 1.5 millimetres (0.059 in) thick, and the nearly spherical shape of the eggs. They are primarily found in India and Europe, but some specimens have been found in South America.
Sphaerovum is an oogenus of dinosaur egg that has only been discovered in South America.
Shixingoolithus is an oogenus of dinosaur egg from the Cretaceous of Nanxiong, China.
Spheroolithus is an oogenus of dinosaur egg.
Protoceratopsidovum is an oogenus of dinosaur egg from Mongolia. Despite its name, it does not represent the eggs of a protoceratopsid, but rather the eggs of maniraptoran theropods.
Pseudogeckoolithus is an oogenus of dinosaur egg. It is known from several fragments of eggshells. The outer surface of these are covered with little knobs and nodes. Some of the pores in the eggshell open through these nodes, similar to modern geckos, but unique among the dinosauroid-prismatic group of eggs. However, the microstructure of Pseudogeckoolithus shows that it is not actually of the geckoid type. It is possible that these eggs represent a new basic group of fossil eggs.
Subtiliolithus is an oogenus of fossil egg from the Nemegt Formation of Mongolia and the Ohyamashimo Formation 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 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.
This timeline of egg fossils research is a chronologically ordered list of important discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of egg fossils. Humans have encountered egg fossils for thousands of years. In Stone Age Mongolia, local peoples fashioned fossil dinosaur eggshell into jewelry. In the Americas, fossil eggs may have inspired Navajo creation myths about the human theft of a primordial water monster's egg. Nevertheless, the scientific study of fossil eggs began much later. As reptiles, dinosaurs were presumed to have laid eggs from the 1820s on, when their first scientifically documented remains were being described in England. In 1859, the first scientifically documented dinosaur egg fossils were discovered in southern France by a Catholic priest and amateur naturalist named Father Jean-Jacques Poech, however he thought they were laid by giant birds.
Egg paleopathology is the study of evidence for illness, injury, and deformity in fossilized eggs. A variety of pathological conditions afflicting eggs have been documented in the fossil record. Examples include eggshell of abnormal thickness and fossil eggs with multiple layers of eggshell. The identification of egg paleopathologies is complicated by the fact that even healthy eggs can be modified during or after fossilization. Paleontologists can use techniques like cathodoluminescence or thin sectioning to identify true paleopathologies in fossil eggs. Despite the diversity of paleopathologies known from fossil eggs, the vast majority of conditions known to afflict modern eggs have not yet been seen among fossils.
Reptile egg fossils are the fossilized remains of eggs laid by reptiles. The fossil record of reptile eggs goes back at least as far as the Early Permian. However, since the earliest reptile eggs probably had soft shells with little preservation potential, reptilian eggs may go back significantly farther than their fossil record. Many ancient reptile groups are known from egg fossils including crocodilians, dinosaurs, and turtles. Some ancient reptiles are known to have given live birth and are therefore not anticipated to have left behind egg fossils.
Hemifaveoloolithus is an oogenus of fossil dinosaur egg from the Tiantai basin in Zhejiang Province, China. It is a faveoloolithid, having spherical eggs roughly 13 cm in diameter. The shell is distinctive for being composed of four or five superimposed layers of shell units, and the honeycomb-like arrangement of pore canals.
Guegoolithus is an oogenus of fossil egg from the early Cretaceous of Spain. It is classified in the oofamily Spheroolithidae, and was probably laid by an ornithopod dinosaur.
Dictyoolithidae is an oofamily of dinosaur eggs which have a distinctive reticulate organization of their eggshell units. They are so far known only from Cretaceous formations in China.
The Dushihin Formation is an Early Cretaceous (Aptian) geologic formation in the Övörkhangai Province of Mongolia. The formation preserves fossils of Psittacosaurus mongoliensis and fossil eggs described as Trachoolithus faticanus.
Spheroolithidae is an oofamily of dinosaur eggs. It contains Guegoolithus, Spheroolithus, and Paraspheroolithus. Like modern birds, the eggshell membrane formed before the calcareous part of the shell.
