New Spinosaurus Paper

[Carnoking]

Been chipping my way through this one (I have a hard time digesting the language of these scientific papers in one setting, which is why I always appreciate the summaries like Suspsy shared) and I did have one pressing question. Was there something I missed that explains the return to the U shaped sail, or is the shape of the sail still largely up for questioning?

[Remko]

Been chipping my way through this one (I  have a hard time digesting the language of these scientific papers in one setting, which is why I always appreciate the summaries like Suspsy shared) and I did have one pressing question. Was there something I missed that explains the return to the U shaped sail, or is the shape of the sail still largely up for questioning?

I think the idea for the U-shaped sail, was that there never has been conclusive evidence for the M shaped sail. So, like you said, the actual shape of the sail is still largely unknown.

I've been reading up the comments about that 2,6 meter is pretty deep water, even for big fish, and mostof the large fish found in similar deposits as Spinosaurus would have been right at home there.
Arapaima's are big, and they live in relatively shallow waters. Sure, all true.

But Arapaima's or other large fish don't have to deal with 12 to 14 meter long giant carnivores out to get them.
So even if they have no problem swimming in only 2.6 meter deep water, they probably wouldn't, because that's where the predators are. They will try to stay in the deeper areas.

Besides, fish like Mawsonia are predators them selves. Probably ambush predators as well. And hiding an up to 5 meter long Coelacanth in only 2,6 meter deep water, is pretty difficult. And if they were like modern coelacanths, they would have preferred deeper waters anyway.

So, like I said earlier, we have a lot to learn about how Spinosaurus lived and hunted if it couldn't swim very well or dive.
Who knows, perhaps in the next couple of years we learn that Spinosaurus had a special organ or ability of some sorts that did made it possible for it to dive and hunt under water.

[andrewsaurus rex]

That's an interesting picture from Pterosaur Heresies....it brings home the environment much more clearly.  BTW what is wrong with Pterosaur Heresies?

I don't think there's anything wrong with that picture specifically, but for general problems with Pterosaur Heresies see this post from Darren Naish.

Ah, I get it now.  Thanks for the info.

[andrewsaurus rex]

Been chipping my way through this one (I  have a hard time digesting the language of these scientific papers in one setting, which is why I always appreciate the summaries like Suspsy shared) and I did have one pressing question. Was there something I missed that explains the return to the U shaped sail, or is the shape of the sail still largely up for questioning?

I think the idea for the U-shaped sail, was that there never has been conclusive evidence for the M shaped sail. So, like you said, the actual shape of the sail is still largely unknown.

I've been reading up the comments about that 2,6 meter is pretty deep water, even for big fish, and mostof the large fish found in similar deposits as Spinosaurus would have been right at home there.
Arapaima's are big, and they live in relatively shallow waters. Sure, all true.

But Arapaima's or other large fish don't have to deal with 12 to 14 meter long giant carnivores out to get them.
So even if they have no problem swimming in only 2.6 meter deep water, they probably wouldn't, because that's where the predators are. They will try to stay in the deeper areas.

Besides, fish like Mawsonia are predators them selves. Probably ambush predators as well. And hiding an up to 5 meter long Coelacanth in only 2,6 meter deep water, is pretty difficult. And if they were like modern coelacanths, they would have preferred deeper waters anyway.

So, like I said earlier, we have a lot to learn about how Spinosaurus lived and hunted if it couldn't swim very well or dive.
Who knows, perhaps in the next couple of years we learn that Spinosaurus had a special organ or ability of some sorts that did made it possible for it to dive and hunt under water.

Unless i'm missing something, I think the illustration of Spinosaurus posted on page 1 of this thread shows most of the sail shape made from combined specimens...most of the sail is complete, albeit made up from parts of different animals....or am I interpreting the illustration incorrectly?

You bring up a good point....you'd think large fish would learn to avoid the shallow waters inhabited by predators like Spinosaurus....all they'd have to do is go out a few feet deeper and apparently they would be safe from Spinosaurus. 

I know the author of the paper is a smart guy and lots of time and research went into it, but something about it still doesn't seem right.  A predator that makes its living along a shoreline having short legs......short legs that are neither very good for chasing prey on land nor wading very deep into the water.  And apparently it wasn't much of a swimmer either.   Just makes me go hmmm....

Now maybe one day the direct ancestor of Spinosaurus will be discovered......and it will have even shorter legs, relatively.  Then Spinosaurus would make more sense, as the leg length would be shown to be increasing over time.

[Lynx]

According to users on Dinopedia, the model is very off and the study ignores the bone density study. Would not take this paper's word for it just yet.

[Gwangi]

I've been reading up the comments about that 2,6 meter is pretty deep water, even for big fish, and mostof the large fish found in similar deposits as Spinosaurus would have been right at home there.
Arapaima's are big, and they live in relatively shallow waters. Sure, all true.

But Arapaima's or other large fish don't have to deal with 12 to 14 meter long giant carnivores out to get them.
So even if they have no problem swimming in only 2.6 meter deep water, they probably wouldn't, because that's where the predators are. They will try to stay in the deeper areas.

Besides, fish like Mawsonia are predators them selves. Probably ambush predators as well. And hiding an up to 5 meter long Coelacanth in only 2,6 meter deep water, is pretty difficult. And if they were like modern coelacanths, they would have preferred deeper waters anyway.

To counter that point, these large fishes may be prey, but they are also predators. If smaller fishes live in the shallow water then that's where the predators have to go to hunt them. And the presence of predators will not necessarily discourage them. As an example, I am an avid fisherman, and in my favorite fishing hole virtually all the fish are hugging the bank, they're not out in the deeper water. It's kind of frustrating really, because it is hard to get to them. They are right up against the shore, in water no deeper than my forearm. We're talking pickerel, largemouth bass, northern snakehead. The apex predators of their pond ecosystem. The shallower water has more cover to hide in...floating and emergent plants, downed trees, etc. That's where the greatest concentration of prey is too...amphibians, invertebrates, small fish. But that's also where the herons hunt. The presence of the herons does not deter the fish, they rely on the cover that shallow water provides. It allows them to hunt while also remaining camouflaged. It is also no secret that nearshore, shallow habitats are the most productive spots in aquatic environments, and hold the highest concentration of biodiversity.

And again, we're talking about fish that are around today and live in those same shallow water environments. Lungfish, sawfish, and polypterids. They live in these environments today despite the presence of crocodilians, and various predatory birds. The predators are not as large as a Spinosaurus but they're still large enough to eat these fish. To me, it seems like Spinosaurus is adapted to this specific sort of environment to hunt these specific prey animals. Predators are adapted to hunt where their prey lives. A heron would never eat if all the fish got wise to them and just went to deeper water to avoid them.  But the fish cannot do that, they are also bound to the habitat to which they evolved to occupy. They need to be there if they also want to feed.

As for Mawsonia, as I already pointed out, shallow nearshore habitats with cover are ideal habitats for ambush predators. It lived in freshwater and brackish ecosystems where extant coelacanths do not occur. And despite being a "coelacanth", Mawsonia and extant coelacanths belong to different families so I'm not sure they can be compared to that closely. And it appears that Mawsonia was either suction feeding, or feeing on mollusks, either strategy can be employed in shallow water environments.

EDIT: And lets also consider that deeper water might be rare in the habitats that Spinosaurus lived in. Tidal flats, estuaries, marshes...these types of places don't generally have deep water. They're vast expanses of shallow water.  Look at places like the Everglades, Okovango delta, the Sunderbans. Water is not deep there. The average depth of the Chesapeake Bay is only 7.62  meter, and it's the largest estuary in the United States. Over a quarter of the Chesapeake is less than 2 meters, and there are fish there, despite all the eagles, osprey, and herons.

[suspsy]

Nothing I can add to what Gwangi just wrote.

[andrewsaurus rex]

thanks Gwangi, that was an excellent explanation. 

I've been wondering about some things.  Does the size of the predator, (eg a Heron vs Spinosaurus)  make a difference to your explanation?  Spino is going to need a lot more food than a Heron and also, it may be tougher for a huge Spino to catch fish, than it is for a Heron....i'm assuming Spino would be slower, due to its size and fish are quick and agile.   I was also thinking that maybe Spino fed infrequently, perhaps only when huge numbers of fish were about eg for spawning, where the pickings would be easy and it could gorge itself and the rest of the time it survived on fat stored in its hump........has it been conclusively proven that the sail was not a fat storage device?

Also, Spinos didn't start off 45 feet long.  At some point in their life they were 2 feet long, 5 feet long, 10 feet long etc.  Would this have made a difference to their lifestyle?  Perhaps when they were smaller they were better swimmers, for example.

[stargatedalek]

This study relies heavily on the body shape but does not account for the unknowns of neck length, back shape, back thickness (ridge vs sail vs sail only at the end), and has a weirdly enlarged tail. Plus ignoring the bone density... I genuinely don't think anything can be meaningfully gleamed from this.

[dinofelid]

According to users on Dinopedia, the model is very off and the study ignores the bone density study. Would not take this paper's word for it just yet.

Link? I checked Dinopedia and didn't see any discussion in the talk section of the Spinosaurus article, there's a discussion of the paper here but it doesn't talk about bone density.

[Lynx]

According to users on Dinopedia, the model is very off and the study ignores the bone density study. Would not take this paper's word for it just yet.

Link? I checked Dinopedia and didn't see any discussion in the talk section of the Spinosaurus article, there's a discussion of the paper here but it doesn't talk about bone density.

There was some small talk here: https://dinopedia.fandom.com/f/p/4400000000000115718

[dinofelid]

@Lynx Thanks. I see the original paper on Spinosaurus having denser bone structure and therefore engaging in "subaqueous foraging" is Fabbri et al. here. Looking into this a little more, apparently the authors of the recent paper had an earlier preprint in April where they criticized the idea of Spinosaurus as a subaqueous forager, Myhrvold et al. here (you can click the 'full text' tab to see the whole thing), and Fabbri et. al had a response to that here. Fabbri also has a twitter thread criticizing the criticism of Myhrvold here.

Incidentally it's not the case that the recent paper just ignores the Fabbri paper and the bone density claims, they discuss it in appendix 1 where they say "Enhanced bone strength is an alternative explanation for solid hind limb long bones in S. aegyptiacus, a very large bipedal theropod with reduced hind limbs. Similar long bone infilling occurs in other large-bodied bipedal and quadrupedal dinosaurs and mammals (Vanderven et al., 2014; Houssaye et al., 2016)." In the "Author response" section at the very end of the paper they also indicate that they are working on a longer response to Fabbri et al. but that it hasn't been submitted yet. This seems like a pretty technical scientific dispute so personally I wouldn't put much trust in the internet commentators with strong opinions on the matter one way or another.

[Gwangi]

thanks Gwangi, that was an excellent explanation. 

I've been wondering about some things.  Does the size of the predator, (eg a Heron vs Spinosaurus)  make a difference to your explanation?  Spino is going to need a lot more food than a Heron and also, it may be tougher for a huge Spino to catch fish, than it is for a Heron....i'm assuming Spino would be slower, due to its size and fish are quick and agile.   I was also thinking that maybe Spino fed infrequently, perhaps only when huge numbers of fish were about eg for spawning, where the pickings would be easy and it could gorge itself and the rest of the time it survived on fat stored in its hump........has it been conclusively proven that the sail was not a fat storage device?

Also, Spinos didn't start off 45 feet long.  At some point in their life they were 2 feet long, 5 feet long, 10 feet long etc.  Would this have made a difference to their lifestyle?  Perhaps when they were smaller they were better swimmers, for example.

I'm not as sure about that one but generally speaking, with endothermic animals, smaller animals need to feed more often than larger ones. As an example, a hummingbird needs to feed more than a heron does, and the heron can miss more meals. Or a lion can miss more meals than a shrew can. This is because the smaller animals have faster metabolisms, it takes more energy to keep them warm and they don't have a lot of reserves. I imagine that compared to a heron a Spinosaurus would probably need to feed less often. And, most of these fishes that lived alongside Spinosaurus, like lungfish, are generally slow moving too. I'm confident that if a grizzly can catch a salmon, a Spinosaurus would have no issues snaring a lungfish from the mud. Keep in mind that we live in a world where the largest animals survive by eating the smallest, so that should tell you something. If filter feeding whales and sharks didn't exist we would probably find the idea that they could exist absurd.

[Prehistory Resurrection]

Video about the latest developments about Spinosaurus. Video credit: E.D.G.E Youtube Channel.