Further Evidence That Spinosaurus Was Aquatic

[suspsy]

https://www.sciencedirect.com/science/article/abs/pii/S019566712030313X

Abstract
A new locality near Tarda on the northern margin of the Tafilalt, south eastern Morocco exposes extensive sequences of the Ifezouane and Aoufous formations of the fluvial Kem Kem Group (Cretaceous, ?Albian-Cenomanian) on the south western flank of Ikfh n'Oufza escarpment of the Hamada du Meski. The stratigraphic sequence here differs significantly from better known exposures of the Kem Kem Group in the southern Tafilalt, and includes a heterolithic sequence of alternating grey mudstones and fine sandstones and a thin (∼1.5 m) marine limestone. The locality is noteworthy for three vertebrate-bearing horizons within the upper part of the Ifezouane Formation. The upper two (Sites 1 and 2 in ascending order) are dominated by dental remains of the sawfish Onchopristis and the aquatic theropod dinosaur Spinosaurus. Significantly, the remains of terrestrial dinosaurs constitute less than 1 % of the total dental assemblage at Site 1 and 5.6% at Site 2. At Site 2 teeth of Spinosaurus outnumber the rostral "teeth" of Onchopristis. The remarkably high abundance of spinosaur teeth compared to remains of terrestrial dinosaurs, and even some aquatic animals strongly supports Spinosaurus being an aquatic animal spending much of its life in water where its teeth were shed and preserved.

[Tyto_Theropod]

The plot thickens!  This is fascinationg, @suspsy, so thanks for sharing.  What a lot we've learned about Spinosaurus in the last decade!  I wonder if how much the Spinoaurus fossils had to do with the marine deposits?  I've always imagined it skulking around in lakes, rivers and brackish mangrove type areas like some sort of outsized saltwater crocodile, but this makes me wonder if the 'Cretaceous whale' theory that's been floating around isn't as far-out as I've always thought.  Or maybe it was more comparable in lifestyle to a seal?  Or a coast-hugging dolphin?  Or maybe just an oversized otter?  So much food for fishy thoughts!

It's also exciting that they've found a new locality for the Kem Kem Group.  I just hope it can be well-documented before there's too much attention from unscrupulous commercial fossil hunters.  I guess that's a vain hope, but still.

[suspsy]

It may also strengthen the argument that Oxalaia is just another species of Spinosaurus that swam across the relatively narrow ocean between Africa and South America.

[Tyto_Theropod]

Definitely a reasonable argument, and probably one we can expect a lot of debate on.  We'd probably need more 'Oxalaia' material to be sure, which is anything but certain given the nature of the sediments its fossils were found in.

[Faelrin]

If last year was the year for figures of Spinosaurus, then this would be the year for all the Spinosaurus discoveries. Really cool find though, and not just because of Spinosaurus. It gives us a better look at its habitat too, which is always good.

[Dinoxels]

So, are they basically saying that just because it's teeth for found in marine deposits means that it was fully aquatic?
It likely shed it's teeth when it was fishing (which we have evidence it did) and those teeth may have been fossilized in said deposits. This study appears to be jumping to conclusions really quickly. Either that or I am misinterpreting the study. I will add that I think Spinosaurus probably did swim towards South America, but there was probably an abundance of islands involved. 

[suspsy]

That abstract clearly states at the end that the evidence suggests Spinosaurus was "an aquatic animal spending much of its life in water."

Much =/= fully aquatic. They are not jumping to conclusions too quickly at all.

[Kapitaenosavrvs]

The plot thickens!  This is fascinationg, @suspsy, so thanks for sharing.  What a lot we've learned about Spinosaurus in the last decade!  I wonder if how much the Spinoaurus fossils had to do with the marine deposits?  I've always imagined it skulking around in lakes, rivers and brackish mangrove type areas like some sort of outsized saltwater crocodile, but this makes me wonder if the 'Cretaceous whale' theory that's been floating around isn't as far-out as I've always thought.  Or maybe it was more comparable in lifestyle to a seal?  Or a coast-hugging dolphin?  Or maybe just an oversized otter?  So much food for fishy thoughts!

It's also exciting that they've found a new locality for the Kem Kem Group.  I just hope it can be well-documented before there's too much attention from unscrupulous commercial fossil hunters.  I guess that's a vain hope, but still.

I like the big Otter. Or a huge Newt.

[elfwink]

That abstract clearly states at the end that the evidence suggests Spinosaurus was "an aquatic animal spending much of its life in water."

Much =/= fully aquatic. They are not jumping to conclusions too quickly at all.

Yeah... I am still not convinced of it being 100% aquatic. I still want to believe it's a semi-land-dwelling animal.

[suspsy]

Pretty sure nobody is claiming that it was fully aquatic. Crocodilians aren't fully aquatic. Pinnipeds aren't fully aquatic. Penguins aren't fully aquatic. Yet they are definitely more adapted for the water than they are for the land. Spinosaurus appears to have been that way as well. At the very least, it would have hauled out on land to lay eggs or bask in the sun.

[Tyto_Theropod]

Pretty sure nobody is claiming that it was fully aquatic. Crocodilians aren't fully aquatic. Pinnipeds aren't fully aquatic. Penguins aren't fully aquatic. Yet they are definitely more adapted for the water than they are for the land. Spinosaurus appears to have been that way as well. At the very least, it would have hauled out on land to lay eggs or bask in the sun.

I agree, hence why I pointed out seals and otters as potential mammalian analogues (mammanalogues?).  I still don't go for the really radical theories people have come out with, like the idea that Spinosaurus might have given birth to live young.  As Carl Sagan so famously said, extraordinary claims require extraordinary evidence.  Anyway, I know that it's controversial to compare dinosaurs to mammals, and understandably so, but I still think it's useful to get the point across as they're the current dominant megafaunal group and the one people are familiar with.  Otters especially, as like Spinosaurus they're long-bodied and short-legged (albeit quadrupedal), and also potentially like Spinosaurus, they swim with their front legs tucked in and a lot of their propulsion coming from the tail.  I've heard a swimming otter described as working like one big, supple, wiggly muscle, and I can imagine a swimming Spinosaurus having a similar degree of suppleness.

But you're right, from the point of view of other Archosaurs, penguins and crocodilians are probably a way better comparison.  Also, whilst the majority are flighted, it occurs to me that cormorants might also be a good analogue.  I can easily imagine a Spinosaurine employing cormorant-style hunting techniques (and a Baryonychine perhaps being more like a heron).  This video is a bit long, but it has some good examples of cormorant hunting behaviours, and also shows just how well-suited a tweaked Theropod body plan is for this kind of lifestyle.  It's also interesting to note that, possibly like Spinosaurus, the propulsion comes from the rear and the head can shoot forward to grab prey.

https://www.youtube.com/watch?v=rF5gAUJUZXA

I've watched my local great cormorants (Phalacrocorax carbo) swimming around duck-style on the surface and then diving with a fluid, rapid movement - very like a tiny cetacean, in fact.  I imagine it would have been a pretty impressive sight if Spinosaurids had done the same kind of thing - it would certainly have made one heck of a splash!  And being egg-laying terrestrial breeders, cormorants also need to exit the water to sun themselves for extended periods, because their feathers aren't fully waterproof and need to be dried out after fishing trips.

There are also grebes and loons, but they're basically fully aquatic - so much so that in the case of grebes that I believe their legs can't really support their weight properly if they have to walk around.  I doubt the same was true of Spinosaurus, but it's interesting to speculate that its lineage might have been heading that way.

So yeah.  Spinosaurus, a giant ottercormorant with teeth.  Yay?

[suspsy]

I think Spinosaurus probably hunted in manner pretty much the same way as crocodilians. Seek out a prime location, then hold perfectly still and wait for fish to swim close enough to lunge and seize them. I have trouble envisioning it actively swimming after its prey like a dolphin or a sea lion. Crocodilians certainly don't waste energy in such a pointless endeavour.

The sail would also come in handy, as the shade it provides would help attract fish. Many fish are attracted to shade; it's how Australian Aborigines were able to spear them simply by standing perfectly still on a rock in the middle of a river. Patience and discipline pay off in fishing.

[Tyto_Theropod]

I think Spinosaurus probably hunted in manner pretty much the same way as crocodilians. Seek out a prime location, then hold perfectly still and wait for fish to swim close enough to lunge and seize them. I have trouble envisioning it actively swimming after its prey like a dolphin or a sea lion. Crocodilians certainly don't waste energy in such a pointless endeavour.

The sail would also come in handy, as the shade it provides would help attract fish. Many fish are attracted to shade; it's how Australian Aborigines were able to spear them simply by standing perfectly still on a rock in the middle of a river. Patience and discipline pay off in fishing.

This is definitely a reasonable hypothesis considering the animal's size.  Something so large and heavy moving about like the cormorant in my example would after all have caused a lot of disturbance in the water, so your theory probably makes more sense from that point of view.  Another archosaur group that employ a similar energy-conserving ambush tactic, albeit above water rather than in it, are the herons, to which Spinosaurids have already been compared on multiple occasions.  I'm not sure how much their shadows come into play, though.  However, I find the idea of a heron-like hunting strategy highly plausible for longer-legged Spinosaurids like Suchomimus.  So perhaps Spinosaurines were the result of an initially heron-like morphology and ambush strategy gradually evolving into a more crocodile-like one?

[stargatedalek]

I've called it before that Spinosaurus hunted like auks and I'll just say it again.
-Isotope data that indicates submerged lower body with skull held out of the water the majority of time.
-Known from coastal deposits with an abnormally high amount of young specimens for the number of remains we have.
-Poorly adapted for moving on land, regardless of how they were doing it.
-Study (with numerous issues) suggests floating.
-Webbed feet for diving, plus specialized finned tail, implies either multiple mods of swimming (floating vs diving?) or behaviour warranting significant propulsion.

And now remains from near shore deposits.