General Discussion by Florence Magovern
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Taxonomic nomenclature of dinosaur eggs is based on thin section analysis of shell fragments. There are four main parataxonomic families of eggs found in Henan Basin, Xixia County, China (1) Faveoloolithidae, (2) Dendroolithidae (3) Spheroolithidae and (4) Elongatoolithidae. Members of the parataxonomic family Faveoloolithidae were found in the earliest (deepest deposits) 20 meters below ground level and have a shell morphotype that is relatively primitive in comparison with the others. Members of the Spheroolithidae family are most commonly found in the middle layer of the egg bearing beds which were deposited in the middle of late Cretaceous period. The 17 inch long eggs of the Elongatoolithidae family were most commonly found in the upper layer associated with the most recent or latest of the late Cretaceous. (Zhao Zikui, 1979). Smaller examples (approximately 6 inches in length) of the Elongatoolithidae family are found in the Nanxiong Basin in Guangdong Province.

The fossilized remains of dinosaur eggs are, in most cases, limited to the egg shell. The embryos themselves were rarely preserved. The morphology and structure of the egg shells reveal few clues which can be cited to justify naming which taxon produced them. Only with fossilized remains of embryos in relatively advanced stages of development, can we begin to associate dinosaur types with fossilized eggs and egg shells.

Shell morphology is the basis that is used in naming the egg types. The structure of the shell in thin section analysis is used to identify the taxonomic family. The late Karl Hirsch was one of the leading experts in this country on eggs and eggshell fragments. He examined several shell fragments. These shell fragments were taken from several different types of dinosaur eggs from Henan Province, China. The following summary is based on thin section analysis and Chinese research papers.

The round, "cantaloupe" size and shape eggs with dark brown shells are the most common found in China. To date, no embryoinic remains have been found to identify the species of dinosaur. Instead, these eggs are classified by shell morphotype. The first shell morphotype is known as Dendrolithus. The shell has a continuous layer at the surface. The following nomenclature is used to refer to these dark brown cantaloupe shaped eggs.


Parataxonomic family - Dendroolithidae

Genus sp. - Dendroolithus sp.

Formation - Kaoguo

Age: Late Cretaceous

Location: Xixia Basin, Henan Province, China

The shell structure of these eggs is said to be Dendrospherulitic. The pore system is Prolatocanaliculate. These are the most common type of egg found in China. All shell fragments we collected during our visit to the newly discovered egg site in Central China were of this type. The Dendrospherulitic eggs appear to be related to the taxonomic group Ornithopoda?? We continue to search for embryonic remains as proof. At present these assumptions are based on comparisons with egg shell fragments found together with fossilized embryos and hatchlings found at other dinosaur nesting sites around the world. The vast majority of the eggs found in China are actually hatched. Click here to see a ct scan of one of these eggs showing the "hatching window."

A second, more rare type of eggs found in central China, is classified as Faveoloolithidae, Faveoloolithus sp. with the remaining information the same. They have the thickest shells of all the eggs from China. They are slightly larger in size than the Dendrolithus, generally flatter and have a rougher more undulating shell texture. The structural morphotype is named Filispherulitic. The pore system is multicanaliculate and there is no continuous layer at the surface of the shell.

The Chinese have published data which indicate that these eggs are most commonly found in the earliest of the late Cretaceous deposits, and that the prevailing climate of the period was hot and humid. Several species of sauropods inhabited China during the late Cretaceous.

The third major taxonomic family of dinosaur eggs found in Henan Province is Spheroolithidae. This type of egg is generally smaller in size with diameters ranging from 3 to 5 inches. The most notable feature is that the shell is often thin.

Parataxonomic family - Spheroolithidae

Genus sp. - Spheroolithus sp.

Formation - Kaoguo and Majiachun

Age: Late Cretaceous

Location: Xixia County, Henan Province, China


The shell structural morphotype is Prolatospherulitic with a pore system named prolatocanaliculate. Recent discoveries of embryos in one type of egg from China having this shell morphotype prove that the smaller eggs of this group are from a Therizinosaur called Segnosaur. These small round eggs formally called Oolithus by Chinese scientists are unique because of the calcite replacement of the egg contents. This created conditions ideal for the preservation of embryonic bones.

Therizinosaurs ("Scythe reptile") were named for their large bony claws. An aberrant group of theropod dinosaurs which, based on tooth structure, appear to be vegetarian yet sport a most formidable hand claw. One of the claws from the hand found in Asia measures 28 inches and this does not include the horny part of the claw which would have made it even longer! Just what these claws were used for is a mystery.

The photo here at right (click the image for a zoom) of a Segnosaur embryo exposed by a careful acid etching technique developed by Terry Manning of the Dinosaur Embryo Project, Leicester, Great Britain. Click here to learn more about Manning's work. See the May 1996 National Geographic Magazine for a color photo of this specimen.

The fourth major type of eggs from China are elongated eggs from Henan Province. They are classified in the parataxonomic family Elongatoolithidae. The name describes the shape of the egg and not the shell structure as in previously named groups. The largest dinosaur eggs found to date in the world, Macroolithus sp., are members of this family. Photo in May 1996 National Geographic, Pg. 99.

Nests of Elongatus eggs found in various locations in China indicate the eggs were laid in radial nests buried in sand or mud in layers as many as three deep. The eggs were evidently laid two at a time. The pairs of eggs were generally oriented at 40 degree angles from the next nearest pair forming a radial spiraling nest with each successive layer buried with a layer of sand or mud. Macroolithus, named for its relative size are found only in the upper strata or most recent deposit in Xixia Basin. The following information relates to this type:

Parataxonomic family - Elongatoolithidae

Genus sp. - Macroolithus sp.

Formation - Shiguo

Age: Late Cretaceous

Location: Xixia Basin, Henan Province, China

The basic type of eggshell grouping is Ornithoid with a ratite morphotype. The pore system is Angusticanaliculate. The Ornithoid or ratite grouping includes fossil eggshell linked to Theropods. Our "Dinosaur Baby Louie" is associated with a nest of this type of eggs. Living ornithoids including ostrich eggs and other large present day flightless bird eggs also have a ratite egg shell structure.

One additional type of dinosaur egg found in China comes from the Southern part in a area known as the Nanxiong Basin, a full days ride (100 km) on back roads north of Guangzhou. These elongated eggs also have a ratite shell structure but are much smaller than the Macroolithus eggs discussed previously.

Parataxonomic Family: Elongatoolithidae

Genus species: Elongatoolithus sp.

Formation: Nanxiong

Age: Late Cretaceous

Location: Guangdong Province, China

Identification by association: Raptor Type

Mark Norrell and others at the American Museum of Natural History have found similar eggs during expeditions to Mongolia. The photo shown here on the right from the cover of Science Magazine Vol. 266 November 4, 1994 shows an embryo preserved inside of one of these elongated eggs. The embryo found in this egg has been identified as an oviraptor.

The oviraptor (Egg Thief) was first described by Henry Fairfield Osborn during his 1920 expedition to Mongolia. The skull of one of these dinosaurs was found crushed and on the top of a nest of what was long believed to be a nest of Protoceratops eggs. Osborn speculated that the skull was crushed by an enraged Ceratopsian parent who caught the the unfortunate "raptor" in the act of stealing eggs.

The photo here on the left, from the cover of Nature Magazine, December 21-28, 1995 Volume 378, shows the mother Oviraptor shielding her nest from the unfortunate disaster which recorded this moment in time. It's discovery in 1993, again by a team of researchers from the American Museum of Natural History, is proof that this was, in fact, a caring parent defending her nest !

One final point of interest relating to dinosaur eggs in general .....Chinese scientists have conducted studies of changes in egg shell thickness over time. Comparison of shell thickness of eggs found in deepest egg deposits with those of the same species found nearer to the surface show a gradual thinning of the shells over time (Zhao Zikui, October 1978). Samples of pollen found in these deposits show a concurrent change in vegetation. This evidence shows a gradual change in climate from humid subtropical to an arid temperate one (Zhao Zikui, 1979). Thinning of egg shells due to environmental stresses in modern birds like the brown pelican has been shown to significantly reduce bird egg viability and could lead to eventual extinction of the species. Changes in climate and vegetation could have weakened the dinosaurs ability to produce viable eggs and hence could have led to their eventual extinction. A paper presented at the 1993 meeting of the Geological Society of America introduced a new theory that the percentage of oxygen in the atmosphere some 120 million years ago (Early Cretaceous) diminished significantly over a period of .5 million years. The percentage of oxygen measured in air trapped in amber went from a high of 35 percent to a low of 28 percent. Extrapolating these findings over time, one could speculate on a cause and effect relationship with the gradual changes in shell thickness observed by the Chinese scientists.

In August of 1995, we were very fortunate to be able to escort Dr. Philip Currie, Louie Psihoyos and John Knoebber to a recently discovered dinosaur egg site in Central China While Louie shot photos, Dr. Currie and Florence mapped 183 specimens of Dendroolithus eggs in and around a village situated at the base of Green Dragon Mountain. One of the photos taken by Louie during this visit is included in the Dinosaur Egg story in the May 1996 issue of National Geographic. The site is protected by the Chinese government.

We were allowed two hours to observe and measure....the culmination of a 10 day journey over the backroads of China. Charlie, here on the left, found one of the few complete eggs in the field. Most were cavities where eggs had been. Chinese officials watched carefully to see that nothing was removed from the site. We hope to return someday to have another look.

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A scene in Montana 75 million years ago, by James Gurney, 1997 commissioned by the United States Postal Service for a limited edition of collectible stamps now out of print.