A mosasaur egg?

[MLMjp]

https://www.npr.org/2020/06/17/877679868/scientists-find-the-biggest-soft-shelled-egg-ever-nicknamed-the-thing
A soft shelled egg that it's believed to be from a mosasaur. If it is indeed one, then I guess not all marine reptiles gave birth.

[Loon]

Very interesting, if this is really a Mosasaur. I'm guessing the behavior would would be similar to sea turtles, but I can't imagine a Mosasaur shimmying onto the land. But, who knows.

[stargatedalek]

I'm not sure how this "helps provide a piece of the puzzle" of egg evolution in vertebrates. Surely if anything this is a transitional form between eggs and live bearing? A large marine animal with eggs that were designed to open as they were laid to allow for underwater birth.

[Halichoeres]

I'm not sure how this "helps provide a piece of the puzzle" of egg evolution in vertebrates. Surely if anything this is a transitional form between eggs and live bearing? A large marine animal with eggs that were designed to open as they were laid to allow for underwater birth.

Wouldn't a transitional form be a piece of the puzzle? In any event, given that these come from the Maastrichtian, it strikes me as odd to refer to it as a transitional form, since the lineage was extinct soon after this. An end-Cretaceous mosasaur with leathery eggs suggests that mosasaurs might have used this strategy for the entirety of their existence. And there was very little physical evidence for fossil soft-shelled eggs before this. There's a tendency to dismiss unsurprising findings--and it is unsurprising that a lepidosaurian would lay soft-shelled eggs--as not adding to our knowledge. But they do! They confirm our hypotheses and that's important! Just like it's important that fossil trackways show bipedal pseudosuchians, even if that is what we should expect based on hip biomechanics. Those things absolutely add puzzle pieces.

[stargatedalek]

I'm not sure how this "helps provide a piece of the puzzle" of egg evolution in vertebrates. Surely if anything this is a transitional form between eggs and live bearing? A large marine animal with eggs that were designed to open as they were laid to allow for underwater birth.

Wouldn't a transitional form be a piece of the puzzle? In any event, given that these come from the Maastrichtian, it strikes me as odd to refer to it as a transitional form, since the lineage was extinct soon after this. An end-Cretaceous mosasaur with leathery eggs suggests that mosasaurs might have used this strategy for the entirety of their existence. And there was very little physical evidence for fossil soft-shelled eggs before this. There's a tendency to dismiss unsurprising findings--and it is unsurprising that a lepidosaurian would lay soft-shelled eggs--as not adding to our knowledge. But they do! They confirm our hypotheses and that's important! Just like it's important that fossil trackways show bipedal pseudosuchians, even if that is what we should expect based on hip biomechanics. Those things absolutely add puzzle pieces.

I meant that it doesn't add to our understanding of the development of eggs in vertebrates, as I assumed the text was implying, but rather paints a picture of a vertebrate evolving away from laying eggs. Though this presumably wasn't a transitional stage in mosasaurs themselves, it's transitional example in that it's a great example of the process we would expect any animal to go through as it adapts to giving live birth (even though mosasaurs seemingly didn't take the last few steps).

[Brocc21]

I'm not sure how this "helps provide a piece of the puzzle" of egg evolution in vertebrates. Surely if anything this is a transitional form between eggs and live bearing? A large marine animal with eggs that were designed to open as they were laid to allow for underwater birth.

Wouldn't a transitional form be a piece of the puzzle? In any event, given that these come from the Maastrichtian, it strikes me as odd to refer to it as a transitional form, since the lineage was extinct soon after this. An end-Cretaceous mosasaur with leathery eggs suggests that mosasaurs might have used this strategy for the entirety of their existence.

Well it's not like they planned on going extinct after this. Thing is we know other marine reptiles gave live birth, and I don't think a 60 foot long moasasaur could haul onto land. I'd assume the eggs hatch in the mother and she gives live birth afterwards. Hatching underwater doesn't seem like a very effective thing to do.

[Halichoeres]

I'm not sure how this "helps provide a piece of the puzzle" of egg evolution in vertebrates. Surely if anything this is a transitional form between eggs and live bearing? A large marine animal with eggs that were designed to open as they were laid to allow for underwater birth.

Wouldn't a transitional form be a piece of the puzzle? In any event, given that these come from the Maastrichtian, it strikes me as odd to refer to it as a transitional form, since the lineage was extinct soon after this. An end-Cretaceous mosasaur with leathery eggs suggests that mosasaurs might have used this strategy for the entirety of their existence.

Well it's not like they planned on going extinct after this. Thing is we know other marine reptiles gave live birth, and I don't think a 60 foot long moasasaur could haul onto land. I'd assume the eggs hatch in the mother and she gives live birth afterwards. Hatching underwater doesn't seem like a very effective thing to do.

Of course they didn't plan to go extinct, but calling something transitional is by definition retrospective. Are otters a transitional form on their way to becoming something fully aquatic? We can't possibly know that because their evolutionary trajectory depends on things we can't measure. If a lineage ends, then an organism close to its end can't sensibly be said to have transitional traits. It's definitely possible that the egg hatched internally, but I don't really see any reason that it couldn't hatch externally as long as it happened reasonably quickly. Whether its emergence is from a cloaca or an eggshell, it needs to get to the surface quickly for its first breath, but that's really the only constraint, and that's already satisfied by the shell being found in shallow water.

[MidnightSpino]

Today we have a small article about it in a newspaper, but only facts have been touched upon.  The suspicion of a mosasaur egg was not mentioned. The newspaper is the German "Mitteldeutsche Zeitung".

[Dinoxels]

https://www.youtube.com/watch?v=VxTbkwcxMrA

I will pass on Edge's video of it. It's most likely an Ankylosaur or Abelisaurid egg that washed out to sea.

[DinoToyForum]

The PDF of the article here: https://www.nature.com/articles/s41586-020-2377-7.epdf?sharing_token=pMjOSnn1WxAsFxOWZdegYtRgN0jAjWel9jnR3ZoTv0Nhc4rVkCnKY27TNfb218GiE3iCqZdb6rBu2MNvB3K-o3v9HKFxhnNNQhOtWtQr6nL4oqCqwycZzkXhMBzog4lNhpdkp3vF9vTsf6W2eLzBNOp7migASjvVirru3sByNlrSAZCSXYPo9tPTX-6GQsHEuCRIVmDcUAPHjid1CZx8TrbrbxXjWI8W4l-iRGaUr65_MvH5lRup9Yq949CGF3Oy&tracking_referrer=text.npr.org

I'm highly sceptical of the suggestion it belongs to a mosasaur – there's already a substantial body of evidence for viviparity in mosasaurs. A dinosaur egg washed out to sea seems more likely, although there seem to be anatomical differences.

Looking at the graph in Fig. 2a, however, there's another animal in the 'soft-eggs' plot: pterosaurs! The trend line for a speculative high mass 'soft-shell' pterosaur egg approaches Antarctioolithus.

The paper states "The only previously known fossil eggs that unambiguously lack a prismatic layer have been reported in choristoderes...and in pterosaurs...". But this is the only time pterosaurs are mentioned in the body of the paper.

So, the structure of this fossil egg - lacking a prismatic layer - seems to match some known pterosaurs just as well as it matches lepidosaurs. Large pterosaurs are known from the latest Cretaceous, including some fragments from Antarctica. So it fits stratigraphically and geographically as well. My hot take, then, is that it could be a giant azhdarchid egg. At least, I wouldn't rule it out. Perhaps it is simply too big for that?