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anastasis008

So i recently visited this forum and i read somewhere that we haven't yet discovered spinosaurus legs and its appearance regarding its feet and legs may be just speculation. The argument that was made was whether spinosaurus was a species of crocodile rather than a dinosaur because he may had small legs. So could that be the case? 

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gigantoraptor

We have more complete fossils from other Spinosaurids like Baryonyx walkeri and Suchomimus tenerensis. They are not crocodiles so why would Spinosaurus be one?

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Bguild
5 hours ago, gigantoraptor said:

We have more complete fossils from other Spinosaurids like Baryonyx walkeri and Suchomimus tenerensis. They are not crocodiles so why would Spinosaurus be one?

 

That's what I would point out as well. There are many dinosaurs where we just have a piece or two of the skeleton. Paleontologists often recreate these species based on close relatives with more complete skeletons documented.

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LordTrilobite

Spinosaurus is a theropod dinosaurs like all other Spinosaurids.

 

What Spinosaurids did have were a set of adaptations that made them similar in some ways to crocodiles. Note the slender snout of Spinosaurids that are great for catching slippery fish as well as the pointed conical teeth just as crocodiles have.

 

This is simply a case of convergent evolution. Two separate unrelated groups of animals (spinosaurids and crocodiles in this case) evolved to suit a certain environment and lifestyle. There seems to be some overlap in the Spinosaurid lifestyle, and so there is some overlap in what these animals look like. And Spinosaurus in particular seems to have gone a bit further and might also have had shorter legs than any other theropod dinosaur, making it look even more crocodile like. But however croc-like it might have looked, it can't escape it's heritage. It will always remain a theropod dinosaur because it's ancestors were theropod dinosaurs. Just like birds today are also a subset of theropod dinosaurs.

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Ptychodus04

I think that it should also be noted that Spinosaurs show cranial morphology more closely related to other theropod dinosaurs than to crocodilians. The placement of a specimen in a particular clade is based on derived features rather than overall shape and function.

 

Good question still. We learn by asking and be being challenged.

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Randyw

Ahhhh! Now here is a subject near and dear to my heart! I’ve actually been following this debate! With the 2004 discover of the legbones and hips of Spinosaurus Aegyptiacus it reignited the debate and in 2014 Nizar Ibrahim and several coauthors have attempted to redescribe this magnificent hodgepodge beast. The leg bones and hips they found are shorter and heavier then had previously been suspected indicating a paddling or swimming creature. They believe these bones more match the bones of early whales and other animals transitioning back to an Aguatic lifestyle.along with a shorter flatter foot with broad claws. They are arguing that the spinosaurus is a quadruped. ( no front legs have yet been found last I heard) that spent 95% of its time swimming and paddling around in water coming onto land to sleep and lay eggs similar to a crocodile. Other paleontologists like Hartman and Thomas Holtz are arguing against that. They are redoing it as a shorter part time quadruped that would walk both on two legs and four at will. living beside the water like grizzly bears. Both sides are using parts of the fossils as ammo for their arguments. It absolutely fascinating!

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Randyw

The bones in red are the bones that they actually have. The other colors are either taken from other animals or guessed at etc.

 

AEC15C60-A7DC-4272-8A24-354588216312.jpeg

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LordTrilobite
On 6/12/2019 at 10:20 PM, Ptychodus04 said:

I think that it should also be noted that Spinosaurs show cranial morphology more closely related to other theropod dinosaurs than to crocodilians. The placement of a specimen in a particular clade is based on derived features rather than overall shape and function.

 

Good question still. We learn by asking and be being challenged.

Oh yes, I didn't mean to imply that the skull of spinosaurs actually makes it look like it actually is a crocodile. Yes, the general shape and function may be similar, but the underlying structure that is derived from it's ancestors remains and betrays it's ancestry. Even a weird theropod skull that superficially looks like something else should still be recognisable as a theropod skull due to it's structure.

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anastasis008
On 12/06/2019 at 2:43 PM, gigantoraptor said:

We have more complete fossils from other Spinosaurids like Baryonyx walkeri and Suchomimus tenerensis. They are not crocodiles so why would Spinosaurus be one?

yeah thats a fair argument

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Ptychodus04
On 6/13/2019 at 3:38 PM, LordTrilobite said:

Oh yes, I didn't mean to imply that the skull of spinosaurs actually makes it look like it actually is a crocodile. Yes, the general shape and function may be similar, but the underlying structure that is derived from it's ancestors remains and betrays it's ancestry. Even a weird theropod skull that superficially looks like something else should still be recognisable as a theropod skull due to it's structure.

Agreed, I understood your point. I may have worded my comment confusingly. I was agreeing with your convergent evolution comment and going further to bring up the topic of cladistics and what places a specimen into a particular clade. We're on the same page: superficial resemblance and similar niche rolls aren't grounds for lumping organisms into the same clade. If it were so, phytosaurs would be considered crocodilians. :thumbsu:

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