How likely do you think it is that sauropod females had ovipositors?

[Halichoeres]

A plausible alternative to an ovipositor would be an extended cloacal chamber running along the underside of the tail. This would place the vent somewhere along the length of the tail and permit the sauropod to lay her eggs at or near ground level merely by lowering her tail. A similar design (if for a different purpose) exists in turtles, where males of many species have an enlarged tail base which houses the penis, and the vent is placed well back along the tail (contra females, which have the vent in the traditional spot near juncture of tail and pelvis).

Somehow I was not aware of the chamber on the tails of females. Turtles do all the weird things.

[Newt]

@Halichoeres - This tail situation is actually one of the easiest ways to sex turtles (though not all turtles show this condition). It's pretty dramatic in some emydids and kinosternids, among others, in which the male's vent is very near the tip of the tail.

That's ignoring all the weird, species-specific secondary characteristics that some species develop, like enlarged heads with broad triturating surfaces (females in some Graptemys, males in some Sternotherus) or the freaky long manus claws of male Chrysemys-group emydids (used for an elegant underwater fingernail dance). Or the most pronounced female-dominant size dimorphism among tetrapods in some trionychids and emydids.

Turtles are pretty fantastical. I've been trying to prod my superiors at the zoo into diversifying our collection (which is not bad now, but you can't have too many turtles).

Anyways, back to sauropods - A @andrewsaurus rex , I was thinking about your idea of eggs that start rubbery and harden after being layed. Another possibility would be that the eggs were preceded by and/or enveloped in some sort of cushioning material when laid - a frothy cloacal secretion, or even feces - that would help break the fall. This material might need to be washed away afterwards, but that's not a big obstacle; the mother could simply follow oviposition with a sluicing of water from the cloaca (once again, as turtles do, though they carry water to moisten the nest hole - if you've ever picked up a turtle and it "peed" on you, it was almost certainly a female on her way to oviposit).

[andrewsaurus rex]

that's an interesting idea, the cushioning material could even just rot away naturally, long before the hatchlings try to break out.  If any remained they could push through it or even eat their way through it.   

It would be nice to know how it was actually done, wouldn't it?   

btw....turtles are pretty interesting....

[TheCambrianCrusader]

@Halichoeres - This tail situation is actually one of the easiest ways to sex turtles (though not all turtles show this condition). It's pretty dramatic in some emydids and kinosternids, among others, in which the male's vent is very near the tip of the tail.

That's ignoring all the weird, species-specific secondary characteristics that some species develop, like enlarged heads with broad triturating surfaces (females in some Graptemys, males in some Sternotherus) or the freaky long manus claws of male Chrysemys-group emydids (used for an elegant underwater fingernail dance). Or the most pronounced female-dominant size dimorphism among tetrapods in some trionychids and emydids.

Turtles are pretty fantastical. I've been trying to prod my superiors at the zoo into diversifying our collection (which is not bad now, but you can't have too many turtles).

Anyways, back to sauropods - A @andrewsaurus rex , I was thinking about your idea of eggs that start rubbery and harden after being layed. Another possibility would be that the eggs were preceded by and/or enveloped in some sort of cushioning material when laid - a frothy cloacal secretion, or even feces - that would help break the fall. This material might need to be washed away afterwards, but that's not a big obstacle; the mother could simply follow oviposition with a sluicing of water from the cloaca (once again, as turtles do, though they carry water to moisten the nest hole - if you've ever picked up a turtle and it "peed" on you, it was almost certainly a female on her way to oviposit).

What zoo do you work at if you don't mind me asking?

[Brocc21]

i'm not so sure sauropods were able to sit or lie down.   Their enormous weight could have caused major damage to internal organs and they many not have been able to breath properly.  It would not surprise me at all to discover adult sauropods spent their entire lives standing.   Horses rarely sit or lie down, usually only when they are sick or injured and even with horses that weigh 1/40 to 1/400 of an adult sauropod, it's bad for them to lie down too long.

Plus it would be difficult for an adult sauropod to sit/lie down then somehow scootch  her backside around to line up her cloaca with the relatively small hole she dug.

I remember having a discussion on this topic a couple years ago. We we're discussing whether or not sauropods slept standing up, and I was supporting the standing theory. It would've been incredible to stumble upon an entire herd of massive titanosaurs standing motionless in the middle of the night.

[ceratopsian]

As a former multiple horse owner whose husband still owns a horse I can assure you it is completely untrue that horses rarely lie down unless sick or injured. A relaxed horse loves to lie down. Not necessarily while being watched by a human though.  The RSPCA gets frequent phone calls from the public to say a horse in a field is dead or injured - but it's just dozing or relaxing in the sun. In a herd they like to have one member on guard. However, there is a limit to how long they can stay lying down before they suffer problems from supporting their weight. But this is not a question of minutes!!  This can be an issue for surgery and post surgery. Or indeed if a horse gets cast in its box But it isn't a problem for normal equine life.

i'm not so sure sauropods were able to sit or lie down.   Their enormous weight could have caused major damage to internal organs and they many not have been able to breath properly.  It would not surprise me at all to discover adult sauropods spent their entire lives standing.   Horses rarely sit or lie down, usually only when they are sick or injured and even with horses that weigh 1/40 to 1/400 of an adult sauropod, it's bad for them to lie down too long.

Plus it would be difficult for an adult sauropod to sit/lie down then somehow scootch  her backside around to line up her cloaca with the relatively small hole she dug.

[Newt]

@TheCambrianCrusader - Nashville Zoo. If you're ever visiting Music City, come by and see us!

[andrewsaurus rex]

it would've been just as incredible to see a herd of titanosaurs all lying down snoozing........in fact it would have been incredible just to see a herd of titanosaurs. 

Ceratopsian:  thanks for the information; something I did not realize.

[ceratopsian]

You are welcome A @andrewsaurus rex. I think it's a not uncommon misconception, hence my keenness to correct it!  The background on my phone is actually a pony called Maisie having a snore while lying down in her box after a hard night eating grass in the field.

Titanosaurs. Yes, I often think of all the sights I would like to see if given the proverbial time machine, a herd of titanosaurs would be the most awe-inspiring.

it would've been just as incredible to see a herd of titanosaurs all lying down snoozing........in fact it would have been incredible just to see a herd of titanosaurs. 

Ceratopsian:  thanks for the information; something I did not realize.

[Fossilized-Rubber]

Re: How likely do you think it is that sauropod females had ovipositors?

I'd say significantly more likely than sauropod males.

Joking aside, you're in luck - this week I visited the Titanosaur exhibition at the Natural History Museum!

On display they had a Titanosaur egg - previously believed to be a geode and stored in the mineral department. The egg is slightly larger than a cricket ball and significantly smaller than a bowling ball. The size would play a large part in its density and integrity for resisting a few knocks and bashes.

You will also be very interested to know that:

"Only about one in every 100 titanosaur hatchlings survived into adulthood because their parents did not look after them. Like turtles, snakes and many other reptiles today, Patagotitans laid many eggs in their lifetime, so there was a good chance that some survived."

They estimate a Patagotitan would hatch 7,500 eggs in its life.

Patagotitan hatchlings also had pointy bumps on their snouts (egg teeth) for breaking free of the eggs. This is a trait seen in chickens to this day.

Titanosaurs also have a wide gait with broad hips/shoulders which allowed them to support their weight, and an expansive ribcage which supported their internal organs against compression. After seeing the reconstruction I can entirely believe they could lie down or squat for egg laying.

An extra interesting aside: the exhibitors considered Tyrannotitan Chubutensis a contemporary predator, with many of their teeth found among the bones. It is not clear whether the Tyrannotitans were responsible for the deaths of the large group of Patagotitans at the site, or if they were scavenging.

[Fossilized-Rubber]

Note the spade-like shape of the rear legs. The claws would form a flat surface when pressed together. This gives a nice, rounded profile for the dug nest.

[Fossilized-Rubber]

Sorry for posting so often - here's a picture of the full skeleton with its wide gait, solid rib cage and smiley face.

[andrewsaurus rex]

Interesting information, F-R.   

Is it possible to determine how thick fossilized eggshells were?   With the very large number of titanosaur eggs that have been discovered around the world, it would stand to reason that if some came out of the female with extra thick shells, which then dissolved or were absorbed by the hatchling inside, there would be some evidence of it.  Also, there might be some evidence of some  eggs with a more soft rubbery shell.   If there isn't any evidence, this may tend to rule those ideas out.

As for lying down to lay eggs, even if it is possible to lie down, I just don't see it being practical.  How on earth would a 30 ton female titanosaur lie down so that her cloaca is lined up right over the relatively small hole she dug (roughly 7 feet by 3 feet for the larger nests).  And I can't imagine she'd be able to slide her rear end around to line it up with the nest, especially given that she would not even be able to see what she was doing as her big body is blocking her view.

As for squatting, i'm still not convinced that ms. sauropod would be able to squat far enough to get her cloaca close enough to the ground for the eggs to withstand the drop, keeping in mind the eggs are not just falling on top of soft sand, many of them will be falling on top of other eggs that have been laid.

Someone suggested that another titanosaur would catch the eggs in their mouth as they come out of the cloaca  and lower them into the nest.  I think the suggestion was tongue in cheek to a degree but that's not looking like such a bad idea anymore.....although I think it unlikely that's the way it was done.

Laying the eggs on some soft cushion or elevated position and then moving them into the nest by mouth.   But even then eggs will be falling on top of one another during the laying process and would run the risk of many being cracked, unless the female  laid one or two eggs, moved them into the nest, the laid one or two more etc.....very labour intensive. 

Now, maybe many of the eggs DID get damaged during the laying process and that's another reason titanosaurs laid so many eggs, but I don't know if there is any evidence of that.

So back to an ovipositor, or  cloacal extension down the underside of the tail of some kind......

[Fossilized-Rubber]

If you doubt that the titanosaur could line up with a hole it dug with its own feet, you could try digging a small patch of dirt with your foot and squatting over it without looking. The body/hole ratios are basically the same. It's surprisingly easy if you are aware of where your own limbs are.

It seems that your theory hinges mostly around the belief that:

a) these dinosaurs were so large as to be comically clumsy

b) they can't lie down

I think you'd only have to look at elephants to dispell both of those presumptions. Like someone else mentioned, the cases of ovipositors in non-insect animals are so very rare.

It seems unlikely that creatures unconcerned with childcare would have some complex ritual of catching the eggs in their peg-toothed mouths as they were passed and gently lying them to rest, only to just immediately stomp off and leave them to it.

But if we're to continue on the path of wild guessing: maybe it used its tail to helter-skelter the eggs into the nest like hotwheels cars.

[Halichoeres]

I've been thinking of a turtle-like egg chute along the underside of the tail, as opposed to a free, separate ovipositor, and I think the former would be much easier from both the standpoint of development, and from the standpoint of mechanics. The tail already has muscles and proprioceptors so the animal can control its position, whereas a free ovipositor would need those to evolve with it, which might be just a little harder.

[andrewsaurus rex]

ok, so another question.  IF momma sauropod did lie down to lay her eggs, how would the rear legs be positioned?  The front legs are pretty obvious.....forward like a dog when lying on its belly.   Would the rear legs swing forward at the hip or backwards at the hip, for egg laying?

[Fossilized-Rubber]

ok, so another question.  IF momma sauropod did lie down to lay her eggs, how would the rear legs be positioned?  The front legs are pretty obvious.....forward like a dog when lying on its belly.   Would the rear legs swing forward at the hip or backwards at the hip, for egg laying?

Judging from the pose of the skeleton at the titanosaur exhibit at NHM, forward at the hip, like a dog.