The Advanced Dinosaur Egg Guide What Is So Special About Eggs?
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Dinosaur Egg Guide- Advanced pdf The Fossil Forum: http://www.thefossilforum.com/ This guide online: http://www.thefossilforum.com/index.php?/topic/92371-advanced- dinosaur-egg-guide/ The Advanced Dinosaur Egg Guide Please share this with those who have egg questions. When possible, technical terms were avoided or defined. Every effort has been made to ensure accuracy, but it is always important to do your own research. This guide is merely a snapshot of information taken from many scientific publications. I am not an expert on eggs, rather I just love sharing what little I have learned over the years, what science has learned over the years. For an overview on how to spot a fossilized dinosaur egg and the sizes of eggs, see the basic guide: http://www.thefossilforum.com/index.php?/topic/92370-think-you-found-an-egg-read-this-first- dinosaur-egg-guide-basic/ Somewhat outdated yet still a good overview of dinosaur reproduction and eggs, with a focus on Mongolia: https://youtu.be/uChHLNTOmZI?t=483 What is so special about eggs? The amniotic egg is one of the most significant evolutionary adaptations as it allowed vertebrate life to permanently exist on land. Long before the dinosaurs and their modern descendants including the chicken, the egg came first. In fact, the better question to ask is “Which came first? The lizard or the egg?” Before the amniotic egg, amphibians and some fish were the only vertebrates able to even venture on land and only for rather short periods of time. A great deal of information has come from studying eggs. What we have learned is summarized as: From University of California Museum of Paleontology Egg Anatomy: Using the best known modern avian dinosaur, the chicken--scientifically Gallus gallus, let us go over the different parts of an egg: “(A) The generalized anatomy of an egg. (B) The chicken eggshell comprises three crystalline layers, including the mammillary layer, prismatic layer, and external layer. The cuticle layer overlying the calcareous eggshell is further divided to two layers, including a HAp inner layer and a proteinaceous outer layer. The shell membrane, namely membrane testacea, is also characterized by two layers. (C) SEM image of the cuticle on the surface of the Gallus eggshell, showing a patchy and cracked pattern. (D) SEM image of the radial section of the Gallus eggshell. The white arrow indicates the cuticle layer that lies on the calcitic eggshell.” From Yang et al. 2018 Fig. 1 Those were technical terms, so how about we simplify. The chicken egg has three distinct shell layers mainly made of calcite, then a soft membrane on the inside of that. What is known as egg whites are the albumen which surrounds the yellow yolk located near the center. The embryo develops within the albumen and is fed with nutrients stored in the yolk. The surface of eggshell is full of openings, tiny pores, and these allow for gas to pass through the shell. A developing embryo needs to breathe just like any animal. Additional information: http://www.ucmp.berkeley.edu/science/eggshell/eggshell1.php How to spot a fake egg: First, the best way to avoid fake eggs is to go and collect them yourself. Always make sure to follow the laws and have permission to collect. In the United States, typically a good way to follow the law is through collection on private land with expressed permission from the landowner. Views of paleontologists do range on private ownership of fossils with many not condoning or endorsing. I personally have little issue with it since amateur collectors have made countless important finds while prospecting for their personal collection. If you are going to buy, do everything possible to ensure the egg or any fossil was legally collected. Often with fake eggs everything seems too perfect. Eggs are delicate and easily crushed or damaged so if there are no signs of any damage or natural alterations be very wary. If the surface has ridges, check to see those ridges continue across a crack or break of the shell. Many fake eggs are mosaics made up of real eggshell fragments assembled together in an egg shape. These mosaics tend to not have the eggshell match on opposite sides of a crack. If you would like more information beyond what is provided or have an unanswered question, feel free to start a thread. If after reading, you want to purchase an egg then please ask the seller for the best pictures they can provide of that egg with something to show scale such as a ruler and start a thread. There are many on the forum who are happy help determine if an egg is in fact real. Just please, whether collecting or buying, make sure you know the laws and follow them. A few good threads on real vs fake eggs: http://www.thefossilforum.com/index.php?/topic/69391-examples-of-commonly-faked-dino- eggs/ http://www.thefossilforum.com/index.php?/topic/83533-red-flag-on-hadrosaur-egg/ http://www.thefossilforum.com/index.php?/topic/71462-beware-of-hadrosaur-eggs/ http://www.thefossilforum.com/index.php?/topic/79465-this-is-how-realistic-a-fakereplica- oviraptor-egg-looks/ How are eggshell and eggs classified? Many people try to name an egg to a specific dinosaur, usually incorrectly. With embryonic remains, however, an egg can be scientifically linked to a particular dinosaur (explained in the next section). Another accepted way for eggs to be linked is through a pregnant female, there are examples of females which died while carry eggs internally. Adults on top of a clutch can be used however only with caution. Eggs are given their own naming scheme just as animals have theirs. In normal taxonomy, we have species, genus, and family whereas eggs have an oospecies, oogenus, and oofamily. The term used for egg taxonomy is parataxonomy. Parataxonomy is used in place of traditional taxonomy when an actual animal or plant cannot be linked, for example-- from a lack of data. In the case of Troodon formosus, its eggs are the oofamily Prismatoolithidae, oogenus Prismatoolithus, and oospecies levis. Parataxonomy is the same system used for trace fossils, such as footprints which are normally not linked to the dinosaur who made them. What is inside a fossilized egg? Is there a yolk? What about bones? Very rarely are embryonic bones found, typically eggs have been filled in with sediments. These then lithify (become rock) and so the inside of nearly all fossil eggs is rock that is similar, if not identical, to the surrounding rock. Eggshell is brittle by its nature and so often cracks, these cracks allow whatever sediments are surrounding to fill in the egg and, depending on how recent it was laid to said crack, allow the amniotic sac and other fluids to drain out. Here is a CT scan of some eggs I am working on. You can see how the surrounding rock is very similar to the inside of the eggs. http://www.thefossilforum.com/index.php?/topic/85649-ct-scan-of-dinosaur-eggs/ In addition to looking for embryonic material, the scan gives us information on the infill, the true shape of the eggs, and reveals anything which could otherwise not be seen within them. Sometimes insects can be found near an egg, for example. Embryonic bones from the oviraptor Citipati, this embryo is curled within the egg. From Wikimedia Commons Importance of Embryonic bones: https://youtu.be/cubdagTiRHE?t=48 Embryonic remains are vital for an actual animal ID, so any chance of them being present must be investigated. If you have any tiny bones which can be seen inside an egg or directly near it, I would strongly encourage you to take the specimen to your nearest paleontology related museum or university. If it does have embryonic remains in or near, then the specimen is invaluable to science. The presence of those tiny remains allows for the next question to be asked. Do we know who laid this egg? Which particular dinosaur? Most likely no, there are some wonderful exceptions though. Several ootaxa (eggshell type) are known to the dinosaur genus or family they were laid by. Here are some examples of eggs and eggshell which were linked scientifically to a particular dinosaur from embryonic remains. Dinosaur or family and its known egg type, oogenus or oofamily. This list is not comprehensive as new discoveries and revisions are made every year. Allosaurus sp. known to Preprismatoolithus coloradensis. (This is debated) Beibeilong (Oviraptor) known to Elongatoolithidae. Citipati (Oviraptor) known to Elongatoolithidae. (See the picture above) Gobipipus (Avian) known to Gobioolithus minor. Heyuannia (Oviraptor) known to Elongatoolithidae. Hypacrosaurus (Hadrosaur) known to Spheroolithus oosp. Lourinhanosaurus (Theropod) known to cf. Preprismatoolithus. Maiasaura (Hadrosaur) known to Spheroolithus oosp. Oviraptorid known to Elongatoolithidae. Therizinosauroid (med to large theropod) known to Dendroolithidae. Titanosaur (Sauropod) known to Megaloolithus patagonicus. Troodon (small Theropod) known to Prismatoolithus levis. Generally, be wary of any claim that an egg was laid by a certain dinosaur! Additional information: http://www.ucmp.berkeley.edu/science/eggshell/eggshell3.php What groups of dinosaurs do we have eggs for? The vast majority of eggs are from non-avian theropods. This group includes dromaeosaurs (like Velociraptor), allosaurs, and tyrannosaurs. We also have eggs from Mesozoic aves (birds), hadrosaurs (duck-billed dinosaurs) and sauropods (long-necks). It is worth noting when we say that the majority of eggs are therapod we mean it. Around 61% of the eggs found globally are therapod and between 41-64% are maniraptorans (birds and their closest non-avian dinosaur relatives). For the others the numbers are much smaller: 7% are sauropods, 13% are ornithischians (hadrosaurs and relatives) with 19% still unknown and that is no yolk.