Sauropod Nest

[andrewsaurus rex]

Can someone point me to a link that has good, accurate information on sauropod nests.  I'm finding the info online to be incomplete and contradictory.  Info for brachiosaurus ideally, although I don't think there is much.

I know that titanosaur eggs were a bit bigger than ostrich eggs and roughly spherical.  It's the nests I can't find good information on (size and shape).

I'd like to make a nest with eggs for my new JW Brachiosaurus.  I see that Rebor made a sauropod nest a few years ago but from what I've read it wasn't very accurate, but I don't know what was wrong with it.  It's just as well as it's pretty much impossible to find now anyway.

Any info appreciated.

[Varanops]

Evidence of sauropod eggs may be fragmentary (ouch!), but several good nesting sites -- in South America especially -- seem to indicate that a marked preference was often shown for proximity to geothermal heat sources (presumably to facilitate incubation).  This would lend itself to a really cool (ouch again!) diorama.  I think there may have been another reason that mother-to-be sauropods chose such locations: namely the sulfuric smells of the mephitic gases often associated with geyser-rich or less spectacular sub-surface heat-generating mechanisms may have masked nest odors which must otherwise have guided potential oophagic predators to the nursery before the chicks hatched.  Turtles dig blind secondary side-pits lard them with a "dud" egg or two, and seemingly scent them attractively to deceive nest-raiding foes, distracting them from the real nest; and at least one modern bird (a megapode, I believe) lays its eggs preferentially in heated regions (e.g., sun-soaked beaches) or near geothermal vents, as well.  Predatory dinosaur brain case molds often indicate generous space dedicated to olfactory function, so I feel my thought has possible merit.

[amargasaurus cazaui]

Not so much a link but a suggestion...buy the book," Eggs, nests and baby Dinosaurs" written by Ken Carpenter...its the most comprehensive source for information I have seen ever put together on dinosaur nesting, eggs and so forth.

As to the nuts and bolts of the thing, I havent read up lately on the topic but my latest understanding was that sauropods likely used a trench method for building nests, perhaps digging a long single wide trench, then walking back over it and deposting the eggs within as the walked down its length. This would make covering the eggs with a shallow layer of soil or perhaps decaying vegatation simple enough. (source of potential warmth) since obviously most sauropods would be large and far too heavy to roost their own eggs.

https://www.bing.com/images/search?view=detailV2&ccid=e0%2fKrvVd&id=E5D7220D00ABE9CBEE1E60827239CDCE7E0E1CB3&thid=OIP.e0_KrvVdaOpEsH_BmRJcIwHaFf&mediaurl=https%3a%2f%2fupload.wikimedia.org%2fwikipedia%2fcommons%2f4%2f49%2fTitanosaur_nesting.jpg&exph=1525&expw=2057&q=sauropod+trench+nesting&simid=608043802977131931&ck=E34917167F71FD6D0833CE983E7F789E&selectedIndex=0&FORM=IRPRST&ajaxhist=0

[Dinoguy2]

As others have said, it appears most dinosaurs including sauropods buried their eggs. Sauropods, at least titanosaurs (so this would likely apply to Brachiosaurus too) seem to have used the trench method described by Amargasaurus.  Hadrosaurs like Maiasaura, as is well known, dug dish-shaped nests but buried the eggs with vegetation. I recall a paper on the evolutionary history of nesting behavior that suggested the most basal known case of exposed nests was in oviraptorosaurs, and those eggs seem to have only been partially exposed (i.e. the egg was partly buried in soil), with a parent brooding the exposed part. So most non-avian dinosaur nests would have been more like croc nests or turtle nests than typical bird nests. Of course some modern birds do use the burial method too, like megapodes.

[andrewsaurus rex]

thanks for all the interesting replies, gang.

I actually ended up finding  a pretty interesting reference on titanosaur nests.  As mentioned they dug a trench with one of their back feet (called scratch digging) and laid around 25 eggs in it.  From porosity, it has been proposed that while many nests were buried, some were left unburied.  To me this suggests that the titanosaurs must have protected the nests, to some degree.  Wide open eggs would have no chance of maturing to the point of hatching, with predators around, unless so many eggs were laid all at once that the local predators could not possibly eat all of them before some hatched.  To me this is unlikely as it is felt that it took 60+ days for the eggs to hatch.

Whether the adults looked after the chicks once they hatched is another matter and from what I've read elsewhere, it seems the chicks were on their own.  Here's the reference:

https://www.researchgate.net/publication/44593490_3-D_Modelling_of_Megaloolithid_Clutches_Insights_about_Nest_Construction_and_Dinosaur_Behaviour#pf11

As far as oviraptorid nests, while there has been much conjecture that they brooded their eggs, many disagree with that conclusion.  For one thing, the large oviraptorids, were too large to brood and this is reflected by the nest construction, which has a central perch surrounded by a wide ring of eggs.  The eggs are too far away from where the adult would have perched to be brooded, so the adult may have merely been guarding them.

The same is felt for the smaller oviratporids.  While the nests were much more compact and the adult's weight was not an issue, meaning brooding was possible, the fact that all but the tip of each egg was buried meant that heat transfer from the adult to the egg would be very minimal.  That plus the fact that only the inner ring was within the oviraptorids 'breeding patch' would mean that that the outer rings of eggs (up to 3) would not benefit from any adult warmth at all.  So again, many feel that the adult in the middle was merely protecting the eggs...I think this may have been done at night when small predators could more easily sneak in and steal eggs.

[amargasaurus cazaui]

thanks for all the interesting replies, gang.

I actually ended up finding  a pretty interesting reference on titanosaur nests.  As mentioned they dug a trench with one of their back feet (called scratch digging) and laid around 25 eggs in it.  From porosity, it has been proposed that while many nests were buried, some were left unburied.  To me this suggests that the titanosaurs must have protected the nests, to some degree.  Wide open eggs would have no chance of maturing to the point of hatching, with predators around, unless so many eggs were laid all at once that the local predators could not possibly eat all of them before some hatched.  To me this is unlikely as it is felt that it took 60+ days for the eggs to hatch.

Whether the adults looked after the chicks once they hatched is another matter and from what I've read elsewhere, it seems the chicks were on their own.  Here's the reference:

https://www.researchgate.net/publication/44593490_3-D_Modelling_of_Megaloolithid_Clutches_Insights_about_Nest_Construction_and_Dinosaur_Behaviour#pf11

As far as oviraptorid nests, while there has been much conjecture that they brooded their eggs, many disagree with that conclusion.  For one thing, the large oviraptorids, were too large to brood and this is reflected by the nest construction, which has a central perch surrounded by a wide ring of eggs.  The eggs are too far away from where the adult would have perched to be brooded, so the adult may have merely been guarding them.

The same is felt for the smaller oviratporids.  While the nests were much more compact and the adult's weight was not an issue, meaning brooding was possible, the fact that all but the tip of each egg was buried meant that heat transfer from the adult to the egg would be very minimal.  That plus the fact that only the inner ring was within the oviraptorids 'breeding patch' would mean that that the outer rings of eggs (up to 3) would not benefit from any adult warmth at all.  So again, many feel that the adult in the middle was merely protecting the eggs...I think this may have been done at night when small predators could more easily sneak in and steal eggs.

Trying to visualize what you have stated there but it does not fit well with the knowledge we have of oviraptorids and their nests. Inner ring seems confusing to me, as there would not be "inner rings" nor other rings....the oviraptorids appeared to all fairly uniformly lay their eggs in a single large circle...two per position as if numbers on a clock face. As the season progressed the female would continue laying eggs in the circle until it was full, at which point she would then begin laying eggs stacked on the next layer upwards, in the empty slots, filling those each with two eggs each as she rotated around the circle....when she moved to the next layer she would then lay her eggs in the empty notches from the previos layer creating one single large circle of eggs she could quite easily brood. She would of course rest on the central or middle raised area, but her entire body cavity would be around the eggs quite effectively. I have never seen anyone challenge this theory to any great effect.....ken Carpenter seemed to suggest it was likely in his book as well. We have multiple brooding samples of oviraptorids on nests in the fossil record.....and as far as I have read noone has substantially presented anything to suggest otherwise...did you have the papers where you saw this stated or some useful citations for that information?
    As to sauropods, I think that many have stated, and I know Ken Carpenter did as well, that he felt the sauropod nesting sites were more like a nursery guarded by the mature members of the herd....as the juveniles hatched they were kept within that area and away from the adults to avoid crushing, predation and loss as much as possible. As far as evidence I have seen most seem to agree sauropods either covered their nests with vegatation or soil, to prevent theft and provide warmth. There are samples in the fossil record of saurpods in large groupings with small groups of infants present as well ....suggesting that parental care was in fact given in some cases to sub adults.

[andrewsaurus rex]

as to the sauropods protecting their young.....I have done little investigation on this subject and have basically gone by what I've casually read.  There was a post on here quite recently by someone who seemed to be in the know, that sauropods did not take care of their young, instead adopting a strategy of laying huge numbers of eggs, so that a few would make it to adulthood.  That's not to say they didn't protect nesting grounds, but that after hatching, the young were pretty much on their own.  Also, if you read the article in the link I posted it does state in there that it is believed that some sauropod species laid eggs that were not covered...I found that surprising.

edit: here's the thread I am referring to: http://dinotoyblog.com/forum/index.php?topic=9416.0  ...it's the post by stargatedalek that implies that sauropods did little to protect their young.  I would be interested to know more information on this subject, as it's one I haven't yet got around to investigating

As to overaptorid nests, a while back I made a little model of an ovaraptorid nest and put a modified schleich oviraptor on it.  I got very into the project and ended up doing a lot of reading on the subject.  I found some great info on it too.  I understand the layout you are describing but it does not jive with all the info I gathered.  The arrangement you describe would result in layers of eggs (which could be described as 'rings' of stacked eggs).  This arrangement would result in a sort of bowl shape formed by the layers or rings of eggs.

So the middle perch would have to rise with the laying of each new layer/ring of eggs in order for the oviraptorid in the middle to be able to sit on top of the clutch.  I guess it's possible that they brought dirt into the middle perch to build it up as each layer of eggs was laid, but it would be awkward for them to do that.  Also, the eggs were placed at about a 40 degree angle to the ground, eggs laid on top of them would slide off.  In addition, the oldest eggs would be on the bottom layer/ring.  Since they would hatch first, it seems to me that the hatchlings would have a difficult time getting out from under that pile of eggs.

The way I have interpreted things, is that the eggs were laid in concentric rings, on a mound like structure.  The eggs were laid in pairs in a communal nest, that several females contributed to.  Some of the oviraptorid nests contained 20, 30, or even 40 eggs......it is very unlikely one female laid them all.  It is more likely that a harem of females, or perhaps a whole group of females laid their eggs in one large communal nest, to make them easier to protect.

I looked at artist representations of oviraptorid nests and what I saw seemed to support the arrangement I have described above.  But perhaps I have totally misinterpreted what I read and saw.  If so, I would appreciate being corrected. 

The way I see an oviraptor building its clutch of eggs is the following: a mound of earth is created.  Eggs are placed, in pairs, around the edges of the mound at about a 40 degree angle to the ground.  Once there is no more room, those eggs are covered in dirt, except for the tips at the top, and another ring of eggs are placed outside of the first ring.  If that ring gets filled then it is covered in dirt and a third ring is started.  There have been nests found with up to four rings of eggs.  Here are pics of what I am describing:

https://media.sciencephoto.com/image/c0285950/800wm ...keep in mind this nest was squashed during fossilization, the eggs would have been laid at about a 40 degree angle to the ground

https://www.goodnewsnetwork.org/wp-content/uploads/2021/03/By-Andrew-McAfee-for-study-published-in-Science-Bulletin-2020-Carnegie-Museum-of-Natural-History-1024x497.jpg

https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTgxOTQ4MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzODI2NDE1MH0.c41fiwLz7bRZwT1Tj4Un2-LoRliaT2fyv50NsoZiDQk/img.jpg?width=1245&quality=85&coordinates=0%2C460%2C0%2C94&height=700

You can see in the two illustrations that there is no way the oviraptorid on the nest could be brooding the eggs.....some of them its not even touching.  When modern birds brood they have a 'brooding patch' which is a small area on their abdomen without feathers...this is what comes in contact with their eggs to warm them.  So for the oviraptorid to brood its eggs, they would have to be directly under it and not buried in dirt, as they could not be warmed by the oviraptorids body.

Here's a link to the oviraptorid nest article: http://www.app.pan.pl/archive/published/app64/app004972018.pdf  ...it's a long read but packed with great info and pictures

[amargasaurus cazaui]

As to sauropods and young, when Sue the T rex was found with bones from I believe at least one if not two sub adults it was strongly suggested she and her offspring had been ambushed or attacked but were moving more or less as a family type pod or grouping.
Working within that context I know of several sauropod sites that were populated with both adults and sub adults suggesting the juveniles were being attended by the adults to some degree or method....I believe in particular that Jack Horner had mentioned one such excavation in one his books. Carpenter also references similar such in his book as well if memory serves, so there does appear to be some potential evidence suggesting parental yada yada sauropods etc.

Stargate is quite intelligent and if she has information to add I hope she does, I always find her takes well thought out, and informed, always a pleasure.

I  can offer that your understanding of oviraptorid nests does appear badly flawed to me ...in many ways. First, the actual fossil evidence does nothing to support multiple rings and rather demonstrates precisely that the multi layered stacked ring is precisely what was done. 
Regarding the middle perch wouldnt it be possible the male and female took turns nesting the eggs? why would anyone assume that she alone attended the duty .Also why assume dirt ...they could have had the entire nest covered in vegetation which increased as the nest grew.

I can offer you this much as fossil direct evidence to demonstrate some of the issues with your assertions....the oviraptorid eggs I have and have seen or handled all demonstrate some obvious traits...one of these is that the eggs laid in higher layers DIRECTLY  over other eggs, fossilize in contact with those eggs ....and when the eggs from the nest are seperated it creates a "bare" shadow on the surface of the eggs where the contact was from eggs above or below...meaning if you get an egg for your collection that was between two layers it is highly likely to have a shadow both above and below where it was contacting the other eggs and when seperated, the shell was fused to the point that only one egg of the stack would come out with more or less most of its shell. Many lower grade oviraptorid eggs came to market with this particular set of markings which vividly demonstrate the eggs were stacked in layers just as I described. I own a citipatti egg myself that demonstrates just such markings. This also destroys the idea the eggs were buried in soil, they simply were not...as that would have protected them from fusing together as they did so often.

Finally , and this one someone will have to help me a bit with , but even in extant birds that revist and lay eggs over an extended period there is a term that describes what happens, but basically the chicks still hatch at the same time period regardless if towards the first of the clutch or towards the upper part. I am not familiar enough with modern birds to describe it well, but Carpenter covers it in his book quite well.

The artwork and illustrations you have provided are lovely pieces but they give the eggs far more slant outwards than the fossil nests that we have as evidence portray , and quite clearly so.

Essentially how do you go from the first image you posted....an actual photograph of an oviraptorid nest and the slant of those eggs, etc and then infer the artwork posted? That nest in that photograph is not squashed, the eggs are fully inflated and evenly layered and notice they are STACKED not outward ringed as proposed above.

I have seen nests of fifty eggs in a circular pattern like this that never break into a second or third circle..but lets suppose for a moment your point is taken...how would you then see the egg laying dinosaur able to move in a larger circle outside the first or second or third without stepping on and crushing her own eggs? isnt that even harder to entertain than a center mound that gradually becomes built up from vegatation or nesting debris? Also wouldnt your concept be expanding the size of the nest which would place the offsring at much more risk to predators and such?

Finally there is another piece of evidence that conflicts with your concept here badly....and that is simply understanding the nature of a dinosaur egg....its surface is covered in patterning called ornamentation, which tends to serve the function of preventing the surface from blocking the pores of that egg allowing nitrogen to escape and water and oxygen to enter the egg.....without this function the egg dies. Period. Game over. Dead chicks. burying the egg in soil unless broken up with vegatation or other methods to prevent the blocking of the eggshell means dead young. This in itself argues heavily against the egg being buried with soil at all. ....
Within the fossil record have been found many many examples of unhatched chicks within eggs....unborn dinosaur eggs. The cause or reason for most if not all was either quick burial, flooding, or volcanic activity but in all cases it was likely due to the unborn chick inside being unable to get water, or air within the egg or to expel waste products.....so covering the eggs unless they were often uncovered and reburied is a definite no.
Probably more than I have posted here on this forum in three years or whatever and I think I have covered it well enough..I do strongly suggest you purchase the book by Carpenter, Eggs, nests and Baby Dinosaurs" as it is the most exhaustive source of information on the topic you will find. He covers most of the things you mention here quite well for my thoughts at least.

[andrewsaurus rex]

wow, very interesting post and it turns my understanding of oviraptorid nests on its head.  I'll respond in more detail later, when I have more time but I just wanted to make a quick post now.

If you read the pdf file I posted, pictures clearly show layers of dirt between 'rings' of eggs.....it's even point out in the captions...don't get me wrong, I was initially confused by descriptions of stacked eggs and others of concentric rings of inclined eggs.  I finally decided the concentric rings of inclined eggs was the correct choice, given the artwork and SOME pictures of actual nests I had seen.  Also, there is a lengthy discussion of how the nest was squashed during fossilization, and mathematical formulas are used to determine the original angles the eggs were laid at (which is purported as 35-40 degrees) ie NOT just stacked on top of each other in a vertical pile.

One more quick point....being able to enter the nest without stepping on eggs is also addressed in the pdf I posted.  There was a path left by the adult which it could navigate through to get to the center perch.

Anyway, more later once I get my work done for the day.. 

Edit:  one other point I should make is that when I made my little nest model, I was specifically focused on making a Citipati nest, as I am using the Schleich Oviraptor figure as a 1/18 scale Citipati.  I wonder if that would change the nest configuration, as Citipati was one of the largest oviraptorids.  The pictures I've seen of what could be described as stacked eggs were for much smaller species of oviraptorids than Citipati.  I have a link for the nest configuration of the largest oviraptorid, which has its eggs in a ring very spread out from the center, as it was too heavy to brood them.  I'll look for that link and post it later.

[amargasaurus cazaui]

Skimmed through the paper you posted, rather quickly..will do so more thoroughly when time allows but even within the paper it is constantly stated "superimposed rings of eggs" meaning rings literally laid right over the previous one.  The do mention the soil between the eggs, a thin covering at one end, rather than fully buried eggs. They make it clear the blunt end of the eggs was open, and only the more pointy end itself was buried in soil.
  I did see mention of the layers of dirt between the eggs, but it would seem quite possible it is simply infill, from being buried in porous sand, and they do state it is only a thin layer, nit actually Burying the eggs .

   As for being able to enter and exit without stepping on the eggs, no, they do suggest that the empty area on the lowest circle might have been random or could have been for that purpose, but if it were that would fail to explain why no corresponding opening on the other layers higher in the stack. From the wording it appears they did not make a determination one way or the other, but clearly an exit would be one that protected all rings of the nest, not simply the lowest ring.

Also citipatti was a medium size oviraptorid, when you allow for Gigantaraptor for instance. Citipatti was in fact barely much larger than Oviraptor itself based on what complicated mess we have of remains from both types. (9-13 feet) Also it bears noting that most brooding fossils thought to be Oviraptor are in fact Citipatti specimens ...but the entire story of those two species and what fossil belonged to which has gotten quite distorted.

Personnal note, I always loved the Citipatti...or "gods of the funeral pyre", named specifically for the brooding fossils found of this species. My citipatti egg is around 7 inches long and weighs over 5 pounds ....it is a good full inch and a half longer than my Oviraptor egg .

it would be quite interesting to get ahold of the responses and comments that the paper is given, and discussion that follows.

[andrewsaurus rex]

one thing the paper does make very clear is that the eggs were placed on the nest inclined at an angle of about 35-40 degrees.  For the egg rings to have been stacked on top of each other, they would have to be lying on their sides.  Otherwise, the uppermost layers of eggs would slide off, given the angle they were lying at was as much as 40 degrees....unless they were super sticky.  The layer of soil between the eggs would not be enough to prevent the eggs from sliding off either, not with that much inclination.  Are you suggesting there was something around the outside perimeter of the stacked rings of eggs, that would prevent the uppermost layers of eggs from sliding off?  The only way I can see that being possible is if the eggs were buried in a circular pit, but every description of an oviraptorid nest I have seen describes them as being a mound, not a hole in the ground.  I noted the 'superimposed rings' comment when I read the article, which is one thing that has lead to my confusion on this issue......many descriptions of oviraptorid nests I have read describes them as 'concentric rings'.  Which means one ring outside of the other, not directly on top of each other. Technically, superimposed does not mean directly on top of, it means partially covering, with both things (in this case the lower and upper eggs) being still evident.  So I took that, along with the other info I have read, as the author describing pretty much what the illustrations I posted show...the lower (inner most) ring of eggs are partially covered by the higher (outer most) rings of eggs because they are partially overlapping...by strict definition that fits the bill of 'superimposed'.

I knew the layer of dirt between rings of eggs was thin.......I guess my wording of 'buried in dirt' was misleading, but the thin layer of dirt did cover most of the egg, with only the blunt end not being covered, as you noted.

My sticking point is that I just don't see how the eggs can be stacked in rings directly on top of each other AND be inclined at a 40 degree angle to the horizontal....those two ideas seem completely in opposition to me, unless there was something surrounding the stacked egg rings preventing slippage.

And how could so many artist representations of oviratorid nests be wrong....I can find at least 10 that all look very much like the 2 illustrations I posted.  I can't find any showing the nest as you describe it......do you have any illustrations you can post...one picture may clear up this mental block I seem to have.

Edit: a couple more pictures

https://www.insidescience.org/sites/default/files/2020-05/Oviraptor_Senckenberg.jpg  ...museum display showing 2 rings of eggs, inclined but looks like less than 40 degrees....this is pretty much how I have come to see oviraptorid nests and what the illustrations I posted above look like

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTj6PSdUckdEoLfkiF1N2-l3an90ccp0_lPIA&usqp=CAU  top view of nest showing a couple of rings of eggs, looking to be inclined.  I don't see any significant amount of dirt between the top layer of eggs and the bottom..this too is pretty much how I see oviraptorid nests being constructed (except for the lack of a dirt layer between rings)...of note is the very obvious pairing of the eggs, in both layers....I've never seen it more clearly evident in any other nests.

[Dinoguy2]

A problem with using illustrations like the ones a few posts back is that, one, they're designed specifically for news articles and need to show the eggs. If the artist designed the oviraptorid differently you may not be able to tell at a glance what is being portrayed. Which leads to two, the volume of feathers there is total speculation. You could easily have longer, bushier body feathers sufficient to cover all the eggs.

[amargasaurus cazaui]

I have mostly stated what I can here other than again saying, buy the book by Carpenter, it is rather definitive. Regarding how the eggs were placed and so forth, I think the best evidence I can see is obviously look at fossi nests.

My only other response for you here is that you posted the photograph in the previous post

"
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTj6PSdUckdEoLfkiF1N2-l3an90ccp0_lPIA&usqp=CAU  top view of nest showing a couple of rings of eggs, looking to be inclined.  I don't see any significant amount of dirt between the top layer of eggs and the bottom..this too is pretty much how I see oviraptorid nests being constructed (except for the lack of a dirt layer between rings)...of note is the very obvious pairing of the eggs, in both layers....I've never seen it more clearly evident in any other nests."


     I offer this idea about that final nest....be quite careful what you accept as actual representations of nests from photographs. One clear and obvious clue this nest has been totally and completely altered from how it was found is that every egg has been removed, entirely cleaned of matrix, cleaned with micro jacks and likely given a coating of B12 or a preservative.....it is highly likely the image represents a "commercialy" cleaned and sold nest rather than one done by a qualified museum for research purposes. The only reason I caught it so quickly is I own a fully prepped ovirapotorid eggs and there is a marked difference between one removed from the nest, entirely cleaned and then replaced. In the image you have here, you have no valid methid of determining once that top row was removed and cleaned if....1) the eggs all came from this nest
                                                                                        2) they were all positioned as they are now
                                                                                        3) there were only two rows, or more eggs of lesser quality present that were removed and
                                                                                        sold
                                                                                       4) the eggs in the nest pictured ALL show little damage, shell loss, or compression suggesting           
                                                                                        possible broken, damaged or incomplete eggs were removed.
                                                                                       5) is original base matrix original, altered, restored or replaced to give many lose eggs a
                                                                                       display
                                                                                       6) do we know this is an actual fossil and not a well cast and painted replica? It does offer
                                                                                       some potential problems with far too constant quality, shape and coloration of every single
                                                                                        egg. (looks far too consistent and perfect for an actual nest)
      If you look at enough actual nests that were not this heavily cleaned and prepped you realize rather quickly that these questions make anything potentially revealing or obvious about the pictured piece to be highly dubious if not outright false.
Context of any fossil is tantamount to the final determination of facts. It isnt present here for this one you posted....

                        Incidentally you mentioned the pairing that seems constant..yes, that is due to the cloaca being used to lay the eggs, being a duel opening type operation. Essentially the hen was laying them two per drop, side by side, as that was how she is physically configured. We have fossil dinosaurs with unlaid eggs in the pelvis that solidify that as mentioned in your paper. We know that the eggs were paired two per set . We know there were gaps between each pair...especially in the bottom layer, and the laying hen would then lie her next round in the openings of that previous circle..thus "superimposing" the next ring over the previous and so on, rather than creating another ring OUTSIDE the first....the ring would only appear concentric because it would be tilted from the eggs at the edges of the openings providing lift to the ones underneath as the rings grew higher. Physically when you examine the nest, you would then see the stacking rather than concentric rings radiating outwards.

[andrewsaurus rex]

so the nest would look like this then:

https://s.wsj.net/public/resources/images/BN-ND732_DinoBi_M_20160318114155.jpg ........it's a hollowed out mound, with a small gap in the center (the 'perch') which is surrounded by rings of eggs stacked on top of each other....the upper ring(s) are angled (inclined)because the eggs underneath act like a bit of a wedge and the upper rings of eggs don't slide off because the inside lip of the hollowed out mound supports the outer ends of the eggs.

I was aware that oviraptorids had twin oviducts......I wondered whether the eggs would be laid simultaneously, but it makes sense they would be.  I still have to wonder about the adult sitting on the nest was actually brooding as I can see little body heat from the adult being transferred to the lower rings of eggs.

[andrewsaurus rex]

Toys R Us had a sale on Jurassic World toys....25% off so I bought a second Brachiosaurus.  I've decided to do more than just make a nest, i'm gong to pose her laying eggs; I just need to heat and bend the back knees, which i'm pretty confident I can do and the rest of the pose is easy.  I'll make the nest and cloaca from sculpey.  Having a bit of problem finding eggs.  I was hoping to use some type of candy that's spherical but everything is too big.  I need something the size of a standard marble or a little smaller.  Marbles themselves are too difficult to paint.  Beads are no good because they have holes in them.

Hopefully I can find something, i'm not really thrilled with the thought of making and painting 20 little eggs from sculpey.

[amargasaurus cazaui]

Toys R Us had a sale on Jurassic World toys....25% off so I bought a second Brachiosaurus.  I've decided to do more than just make a nest, i'm gong to pose her laying eggs; I just need to heat and bend the back knees, which i'm pretty confident I can do and the rest of the pose is easy.  I'll make the nest and cloaca from sculpey.  Having a bit of problem finding eggs.  I was hoping to use some type of candy that's spherical but everything is too big.  I need something the size of a standard marble or a little smaller.  Marbles themselves are too difficult to paint.  Beads are no good because they have holes in them.

Hopefully I can find something, i'm not really thrilled with the thought of making and painting 20 little eggs from sculpey.

I do highly suggest reading the book I suggested before you expend much cash or resources moving forward. It is possible that you could make an assumption leading to inaccuracy later for something you spent hard work and cash at.

By example we do not know if Brachiosaurus "hunched" down and Squatted as close as possible to the ground to lay its eggs, or if the dinosaur might have had some form of ovipositor. It does present a problem with soccer ball sized eggs dropping more than a few feet to hard ground.
Since behavior and soft tissue do not preserve that makes it problematic to know things for sure.

One possible method might have been to dig a long trench and create a mound alongside of vegetation, debris and soil....if the eggs were laid on the mound, then a sweep of the tail might shove eggs, and all into the trench.  The simple answer is we do not know for sure how they accomplished this part ......

As for eggs, you might try shapeways and see if someone sells anything remotely similar. Also visit your local gem and mineral shop, most carry a nice selection of smaller eggs, marbles, etc, and perhaps you could find something to your liking that does not require paint even.

Just some things to think about....I did all the same things as I created my displays myself.

[andrewsaurus rex]

hm......interesting comments.  Thank you.   I was concerned a bit about the drop distance of the eggs.  I'll be able to get the cloaca to about 2 inches off the ground, which is 3 scale feet. To be honest I have my doubts about the ability of a 30 ton animal to squat any further down, although brachiosaurus' forward center of gravity would help a bit.  The eggs were probably soft shelled but that's still quite a drop.  I was thinking that there could be vegetation IN the nest itself to soften the landing..  The idea of having it beside and then sweeping the eggs into the nest is clever.  I wonder if it is too clever for a dinosaur to evolve?

When doing projects like this, one has to make assumptions and decide a course of action and proceed, knowing full well it could be wrong.  The way I look at this hobby is everything in my collection is wrong.....it's just a matter of how wrong it is.  There is almost no chance one could guess behaviour and appearance, colour etc accurately so I just take my best guess and then correct as i learn new information 

I am going to go with the titanosaur model of the scratch dug nest for sure.   I was going to have a fairly extended cloaca which would lessen the fall a bit and use vegetation in the nest to soften the blow.  If I learn its wrong I can always change things.....i'm doing it all the time with my collection anyway; regularly re-doing figures as new info comes in or is learned by me. 

Do any vertebrates have ovipositors?  I think some fish do but I thought that was mostly an insect trait.  I guess my extended cloaca is sort of along the lines of an ovipositor.

I've read that titanosaur eggs were only a bit bigger than ostrich eggs, so i'm guessing 7 inches in diameter.  I was going to make them white just because I've not read anything about them being coloured (as opposed to oviratporid eggs which are thought to have been a shade of green).

I have found a couple of very detailed references online that I planned to read before proceeding...and then blunder in.  If  there is a choice to be made or I am in doubt I usually go with the thing that looks the coolest and then correct it if I find its wrong...    So for now, the plan is a squatting Brachiosaurus mother, laying white eggs into a scratch dug trench nest lined with vegetation.  Subject to change...

[amargasaurus cazaui]

hm......interesting comments.  Thank you.   I was concerned a bit about the drop distance of the eggs.  I'll be able to get the cloaca to about 2 inches off the ground, which is 3 scale feet. To be honest I have my doubts about the ability of a 30 ton animal to squat any further down, although brachiosaurus' forward center of gravity would help a bit.  The eggs were probably soft shelled but that's still quite a drop.  I was thinking that there could be vegetation IN the nest itself to soften the landing..  The idea of having it beside and then sweeping the eggs into the nest is clever.  I wonder if it is too clever for a dinosaur to evolve?

When doing projects like this, one has to make assumptions and decide a course of action and proceed, knowing full well it could be wrong.  The way I look at this hobby is everything in my collection is wrong.....it's just a matter of how wrong it is.  There is almost no chance one could guess behaviour and appearance, colour etc accurately so I just take my best guess and then correct as i learn new information 

I am going to go with the titanosaur model of the scratch dug nest for sure.   I was going to have a fairly extended cloaca which would lessen the fall a bit and use vegetation in the nest to soften the blow.  If I learn its wrong I can always change things.....i'm doing it all the time with my collection anyway; regularly re-doing figures as new info comes in or is learned by me. 

Do any vertebrates have ovipositors?  I think some fish do but I thought that was mostly an insect trait.  I guess my extended cloaca is sort of along the lines of an ovipositor.

I've read that titanosaur eggs were only a bit bigger than ostrich eggs, so i'm guessing 7 inches in diameter.  I was going to make them white just because I've not read anything about them being coloured (as opposed to oviratporid eggs which are thought to have been a shade of green).

I have found a couple of very detailed references online that I planned to read before proceeding...and then blunder in.  If  there is a choice to be made or I am in doubt I usually go with the thing that looks the coolest and then correct it if I find its wrong...    So for now, the plan is a squatting Brachiosaurus mother, laying white eggs into a scratch dug trench nest lined with vegetation.  Subject to change...

Anything done in regards to dinosaur anatomy, mating and such is open to speculation and as new evidence presents itself, change as well. that being said, the concept of plowing forward with such things without reading the most established literature published on a given topic seems to invite problems needlessly, hence my suggestion you buy the book.

As for eggs being swept into the nest, it is merely a speculation of my own...and nothing more. As for being too clever for a dinosaur to evolve, as a famous actor once said...."Life finds a way"
Seahorses for instance have ovipositors....you have to ask yourself, do any living vertebrae have many other characteristics that a sauropod does....and if not then why would you eliminate this possibility.

Titanosaur eggs would resemble a mildy deflated soccer ball in size and shape at least, but I have no idea the coloration
Oviraptor eggs are normally considered more blue tinged with green than actual green.

https://www.theguardian.com/science/2017/oct/11/duck-egg-blue-and-oviraptor-green-study-reconstructs-colour-of-dinosaur-eggs

https://www.nationalgeographic.com/science/article/dinosaurs-eggs-blue-fossils-china-paleontology-science


usually at the end of the day what might "look the coolest" is perhaps the most unlikely possible answer....conjecture and speculation are always fun, and admittedly most things involving this topic remain largely unknown...but where there is evidence for it and the effort made to provide it, I find it best to listen to that

[andrewsaurus rex]

those are sage words.

So I've identified 3 snags with Brachiosaurus egg laying.

Snag 1:  The brachiosaurus would have to place the vegetation, whether in the nest or beside it, with her mouth.  I was wondering whether a brachiosaurus could put its head all the way to the ground, as I thought the change in blood pressure could cause serious problems for the brain.  However, giraffes have no problem (albeit they are much smaller) and I assume Brachiosaurus had to drink water and would need to put her head all the way to ground level for that (unless sufficient water was absorbed from the vegetation she ate, which I doubt).  So, overall I think this snag is solved.

Snag 2: How did the female aim her eggs to land in the nest?  She is huge, with her body in the way and the nest so far away from her eyes (could be 70 feet or more).   It seems unlikely to me such an enormous animal could be precise with such an activity.  So, I wonder if this is how they did it: the female just chooses an area she likes, stops and lays her eggs on ground (whether by ovipositor or squatting).  She then digs the nest beside the pile of eggs with one of her back feet.  This would require much less precision then aiming eggs into a nest.  At that point she sweeps the eggs into the freshly dug nest.  This is a slight modification of your suggestion.  It would mean the female would have needed to lay all her eggs at once (but given how relatively small they are I don't see that as much of an issue) OR she would have to dig a new nest every time she laid a clutch of eggs, which doesn't seem unreasonable at all.  This means I would have to either pose my brachiosaurus laying eggs, with no nest yet OR pose her sweeping the eggs she has laid into the freshly dug nest, but not laying eggs in or beside a nest, which was my original plan.  I think this scenario for mama brachiosaurus egg laying is very likely.

Snag 3: not a major snag but if the eggs are dropping some distance to the ground, they will land on previously laid eggs, perhaps resulting in further damage to them or at the very least they could bounce and roll around, scattering them over a wide area.  Whether this would make it more difficult to sweep them into the nest, I don't know.  Probably not, but it is something to consider.

So the big question now for me, is whether to have mama Brachiosaurus squatting, standing with a long ovipositor or some combination of the two (which is the way I am leaning now......squatting somewhat with a highly extended cloaca/ovipositor depositing the eggs....something like what the alien queen did in Aliens....or at least the way I remember it.....haven't seen the movie in many years.

[amargasaurus cazaui]

Science can be so fun..with each set of questions you answer it asks a new set to solve...

Perhaps one of the best papers written about titanosaurids and nesting and eggs is this one

https://www.researchgate.net/publication/228782405_The_Late_Cretaceous_nesting_site_of_Auca_Mahuevo_Patagonia_Argentina_Eggs_nests_and_embryos_of_titanosaurian_sauropods


The only thing I wondered at via your last post was that sauropods would have used their mouths to move vegetation....using the sweeping method I suggested would allow them to use their tails of course...but what if they chose an area intentionally that was already thick in foliage and plants and as they laid the eggs and such it trampled the material into the architecture of the nest? Perhaps a generous piling of ground debris...leaves, plants, or such would have been the ticket where to locate the nest.