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The Basic Dinosaur Egg Guide

Many people often mistake a concretion for an egg, to help clarify what is a concretion, and what is a real egg, here is a guide.
 

A quick overview with examples:

 

 

 

How to spot a concretion:

 

 

How are they different from eggs?

 

 

A concretion is a rather common rock made of tightly compressed minerals. Typically, concretions are a smooth sphere or oval with little to no surface texture or just a few bumps. Often nearly a perfect sphere, sometimes more of an oval. In a concretion, there is no eggshell. If you cannot see eggshell then you do not have an egg. If it looks the same shape as modern egg, such as from chicken then you do not have an egg. Concretions may have fragments breaking off and these will tend to be smooth on both sides. They tend to be dull earthy colors with a different composition in the center, as seen by a change in color. A different color in the center normally means you do not have an egg. Often circular bandings can be seen around exterior of concretions. Sizes of concretions range from just an inch, or a few millimeters, up to more than 10 ft (3 m). Egg sizes, along one side, range from just an inch or a few millimeters and top out at around 8 in (20 cm). If you find an oval or round shape, which is larger than 8 in (20 cm) along a side then it is probably not an egg.

 

 

For more information on concretions:
https://www.priweb.org/index.php/education/education-projects-programs/earth-101/concretions

 

http://tumblehomelearning.com/geologists-find-largest-dinosaur-eggs-in-the-world-another-fraudulent-fossil/

https://en.wikipedia.org/wiki/Concretion

In video form: https://www.youtube.com/watch?v=B5IoyLEwkMY

 

Example of concretions, these three were incorrectly given an ID as “dinosaur eggs” however they are clearly not:
5c5f387d59424_concretionlikeegg.jpg.6df130db2ea9360d08afa0bfed3c1873.jpg
From Tumblehome Learning, link above

 

 

Pseudofossils:

 

 

There are some pseudofossils, which can have a similar appearance to an actual egg, right down to seeming like there are bits of eggshell.

This pseudofossil does look similar to an egg and even seems to have eggshell, however it is not an egg and is actually geologic. The surface ranges too much in texture and composition. Pic from Montana State University, taken by P. Germano
pseudofossil.thumb.jpg.cace49eab686610623dab871800c7099.jpg
 

Trace fossils:
 

 

Many times, an actual trace fossil can be mistaken for an egg, common examples of this are pupa cases and cocoons. As one can see below, they do tend to have an egg-like shape and are yet another perfect example of why shape alone should not be used when trying to identify eggs. The three below are important trace fossils, just not eggs.


 

Fossil-Cocoons-Montana1.jpg.9e57243a5573f12180d3ddee73a121d0.jpg.eb89e790b4c0d7193e5e04a5bd208672.jpg
Pic by Tony Martin, Ph.D.

 

 

How to spot a real egg:



The best and only true sign you have an actual egg is eggshell actually being present. Eggs come in many shapes from a semi-rounded, elongated oval to a perfect sphere and many others. Shape is not a good indicator of an egg. It is useful but only when combined with other details. Eggshell often has surface ornamentation that gives it a unique texture which can be seen by the naked eye or with a hand lens. There are many such ornamentations and they are used to help distinguish one egg type from another. On the surface look for little bumps, ridges with valleys, river channels, and similar textures. Individual fragments of eggshell are rather common in some geologic formations so be on the lookout for a larger grouping of eggshell. 

 


 

5c5f39bf84186_EggshellSurfaces.JPG.54f812d924550e33d5b39649bff3367c.JPG
From University of California Museum of Paleontology


 

Also read:

http://www.thefossilforum.com/index.php?/topic/59654-dinosaur-eggs-lowell-carhart-guide/

 

 

 

Examples of real eggshell:

 

 

 

Example of eggshell fragments:

 

maiasaura_eggshell.jpg
An eggshell fragment from Maiasaura, which is the oogenus Spheroolithus oosp.  Pic by W. Freimuth.

 

 

Examples of real eggs:


9325347404_1014e3c1f9_b.jpg
A clutch of Troodon formosus eggs, which are the oospecies Prismatoolithus levis. Pic from Museum of the Rockies

 

 


Do I have embryos inside this egg?

Most likely no. Embryonic remains are extremely rare within eggs, and you add that with the rarity of eggs to start and it is a remote possibility. No fossilized yolks have been found and since they are soft tissue, it is near impossible for any to fossilize.
 


I still think this is an egg!

If you still think you have an actual egg, then please start a thread. Take close detailed pictures with something for scale such as a ruler and provide all the information you can about it--like where it was found. Good pictures will help greatly with a proper and correct ID.

Below is an example of how to best photograph an egg or eggshell. There is clear lighting, a background which is clearly different than the eggshell in question and a scale bar. Lights can be as simple as a desk lamp; a scale bar can just be a ruler and the background can be very simple, in the example just a paper towel.

5c5f3adda26cf_Kmegaloolithus.thumb.jpg.a48fb10bb7ec9fb38e99024ecdc15bdd.jpg
Megaloolithus egg. Pic from Montana State University, taken by P. Germano

 

 

 

If you would like to learn much more on eggs, here is the advanced egg guide which goes in depth. Also, see the advanced guide for sources.

 

Eric P.

Edited by CBchiefski
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  • I found this Informative 24
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Just want to add to your excellent thread this older topic in TFF. :)

 

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  • 4 weeks later...

Hello I really enjoyed your information. Thank you so much for taking the time to help us novices.

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On 3/6/2019 at 2:23 PM, Ms Michal said:

Hello I really enjoyed your information. Thank you so much for taking the time to help us novices.

Am delighted to hear that and happy to share what little I know.

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Darn good guide on eggs. Thanks for doing this

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Great post really enjoyable and sure many members will find it as useful as it is fascinating. Bobby 

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  • 10 months later...

Ok, that clutch of eggs made me a tad nauseous lol but thank you for more info.  I actually made a new friend of mine a little miffed because she screamed out (which almost made wet my pants) “I found an egg!” And proceeds to dance a real Irish jig, there was so much mud it looked like a   Lord of the Dance video( no Michael Flarraty Though, bummer!)   When I calmly walked to her and said,”Nope, not an egg!” She got miffed so I apologized, and explained al the advice I’ve found on it here.   Told her she might want to carry it to the high school before she spent money to have some smack an ID on it.  She called me later and said yep, just a rock... thank you for leaving me the smartest in my friend group (doesn’t say much for us lol) by the way I’m just joking I’m not a know it all.  It’s 3inches long about 2 inches deep.  It’s so smooth and under a harsh bright white bulb you can see small banding. (And it’s about as boring tan as you can get)

A65CCE98-4469-46FB-9574-414B8B442A79.jpeg

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On 1/31/2020 at 11:35 PM, Pbassham said:

Ok, that clutch of eggs made me a tad nauseous lol but thank you for more info.  I actually made a new friend if mine a little miffed because she screamed out (which almost made pee my pants) “I found an egg!” And proceeds to dance a real Irish jig, there was so much mud it looked like a   Lord of the Dance video( no Michael Flarraty Though, bummer!)   When I calmly walked to her and said,”Nope, not an egg!” She got miffed so I apologized, and explained al the advice I’ve found on it here.   Told her she might want to carry it to the high school before she spent money to have some smack an ID on it.  She called me later and said yep, just a rock... thank you for leaving me the smartest in my friend group (doesn’t say much for us lol) by the way I’m just joking I’m not a know it all.  It’s 3inches long about 2 inches deep.  It’s so smooth and under a harsh bright white bulb you can see small banding. (And it’s about as boring tan as you can get)

 

Sorry they made you a bit nauseous and it is a joy to hear you found my guide useful. Your story made me laugh, thanks for sharing. Over the summer I found a concretion, near a trackway, which was trying very hard to fool some of the less experienced crew members, see below.

DSC_0011.JPG

Edited by CBchiefski
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  • 3 weeks later...

Yes, I have found some just like that, welll once I cut them open. I always get a little scared before I bust something open. Your information has been very valuable especially in keeping our expectations moderate not going over the top and in excitement but not giving up hope either and seeing the value in even poop, lol. A couple of weeks ago I actually got caught up teaching my son’s third grade class because everybody brought a rock and said it’s a dinosaur egg. Of course I’m no expert but for some reason my son made it appear that I was. I later told his teacher that I was just a kid who never grew up he still wants to dig in the mud. I did introduce her to this site and told her that by far this was the most valuable tool I had access to.This is going to be my next thread topic I need help identifying this.. this is going to be my next thread topic.  I going to need lots of help identifying this.Of course all of y’all are so good it’ll probably be identified in like an hour

CE6117D5-6EE9-4BA0-9A53-59808A6B10A2.jpeg

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  • 4 months later...

Wow! Your guide is so informative! I'm a fossil virgin and so posts like this are going to teach me SO much. Thank you.

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