What Caused Gigantism in Spinosaurs?

Makaveli7

MemberCompsognathusJuly 23, 20132083 Views8 Replies

As we all know, spinosaurs were particularly huge for carnivores. With at least four species topping 40 feet and most of the others being at least 30, we can safely say that they were huge. But why? Gigantism is usually caused by island gigantism, abyssal gigantism, mutations or from competition with other large predators. Island gigantism occurs when a small animal like a Rhea gets somehow stranded on an island and over the course of hundreds of thousands of years the population turns into 12 foot tall Moas due to a lack of competition and lack of predators, but then eagles that end up on the island start evolving into giant Haast's Eagles to prey on the Moas. [img]http://cdn-www.cracked.com/articleimages/wong/evolution/kiwi3.jpg[/img] [img]http://img467.imageshack.us/img467/8084/moa3nt.jpg[/img] Abyssal Gigantism occurs when an animal lives in the deep sea and grows huge presumably because there's a giant monster that will eat it if it doesn't, resulting in giant and colossal squids. [img]http://animalpicturesarchive.com/ArchOLD-4/1127460649.jpg[/img] [img]http://scienceblogs.com/deepseanews/wp-content/blogs.dir/414/files/2012/04/i-3fe2a049ec4409b37829619490e7273c-DSCN0270.jpg[/img] [img]http://4.bp.blogspot.com/_LbccUVbSRd8/RYhNSbXsPFI/AAAAAAAAACs/0BmgAHbpzfE/s400/giantisopod_knuttz1net.jpg[/img] [img]http://files.abovetopsecret.com/images/member/6de16bf14bbb.jpg[/img] There's mutations that occur when one animal grows huge due to a pituitary problem and is bred with another huge specimen and it creates huge offspring and so on. [img]http://www.hoax-slayer.com/images/giant-rabbit3.jpg[/img] Then there's gigantism due to competition. One carnivorous animal shares a food source with another carnivore and to outcompete the other one will eventually start growing to unnatural sizes and when the other does as well you will come out with two huge animals, one ultimately bigger than the other. Island gigantism could have sort of played a role in spinosaurs' gigantism because the water they fished in was like an island on the sense that they were isolated in a place that had few other predators and they may have grew due to lack of true competition. Obviously abyssal gigantism is out of the question because they didn't live in ocean trenches and mutation is unlikely because nobody was forcing huge specimens to breed. Perhaps they grew huge to handle huge prey like the Haast's Eagle? Gigantism due to competition is likely. Spinosaurus, the Horror Mouth, Oxalaia and Suchomimus all shared habitats with Sarcosuchus and carcharodontosaurs as well as other giants in the form of Sauroniops, Giganotosaurus, Mapusaurus, Carcharodontosaurus, Bahariasaurus and Ekrixinatosaurus, all of which would have competed with spinosaurs at some point. [img]http://3.bp.blogspot.com/-5aw1t_RJoLA/ThDoag7EHXI/AAAAAAAAAkQ/GbJ8QN3bEBg/s400/Carcharodontosaurus-vs-spinosaurus.jpg[/img] [img]http://www.raul-martin.net/raulmartin/uno/sarcosuchus.jpg[/img] Why do you think spinosaurs were so huge? What about carcharodontosaurs?

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July 23, 2013

I would like say that not all spinosaurs were massive. Big, but not massive. Irritator is a good example. It was roughly 20-25 ft long, big, but not gigantic. Anyways, I think the truly big ones like Spinosaurus or Oxalaia were giant because of competition. Even though my estimates are smaller than most, they are still big, Spino roughly 7 tons and Oxalaia at 5 tons. Same size class as the other super predators like Giga and Rex. While I don't think Spino attacked really big prey like Carchar, it still probably hunted a number of smaller animals and fish(smaller in my opinion goes up to around 20 ft). Carchar would have been willing to hunt these animals too(minus fish). It's not just the really big predators too. The spinosaur family also competed with a number of other medium sized and mildly large sized carnivores like Rugops, Deltadromeus, and Aucasaurus in the south, and Tarascosaurus or Neovenator in the north(for Baryonyx). These carnivores were still big and may have hunted in groups which would make up for their being slightly smaller. The same would go for the other families(allosaurian and abelisaurs) The only group that did not get huge because of competition was the tyrannosaurs. They had their domain all to themselves. They got huge because there was nothing to stop them from doing so( really big tyrannosaurs like Tyrannosaurus rex, Tarbosaurus, and Z-Tyrannus). That's what I think. Sorry if it's a little lengthy ;) Sizes based on my estimates and theories.

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futurepaleontologist1
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July 23, 2013

I think that Gigantism through competition and isolation and straight up splendor. Spinosaurus was the only African therapod that preyed on fish at the time. There was little competition, plenty of food and room to grow. Those three factors add up to a really big dinosaur

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futurepaleontologist1
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July 23, 2013

Well not the only one, but still there were very few

Pity is for the living. Envy is for the dead. -Mark Twain

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July 23, 2013

I was gonna say, Suchomimus for one. But I get what you mead futurepaleontologist.

"Men like me don't start the wars. We just die in them. We've always died in them, and we always will. We don't expect any praise for it, no parades. No one knows our names." ―Alpha-98

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July 23, 2013

Here, this should help get the point across that the spinosaurs were big. Even I admit they were huge. Just not as huge as other people think ;) [img]http://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Spinosauridscale.png/800px-Spinosauridscale.png[/img]

"Men like me don't start the wars. We just die in them. We've always died in them, and we always will. We don't expect any praise for it, no parades. No one knows our names." ―Alpha-98

Deltadromeus
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July 23, 2013

One reason spinosaurs could grow huge is because they were light. When you are 60 feet long (in Spino's case) then there is only so much weight your legs can carry. There are several spinosaurs over thirty feet long. Remember, Baryonyx was found as a sub adult, and that specimen could have gotten bigger. An abundance of big prey also leads to big predators. Take South America for example. There are at least four predators over 40 feet, and two of them are around fifty feet. (Giganotosaurus and Oxalaia). Then you have horror mouth, ( I call him Deinognathus). It is though to be 40+ feet. These are my estimates by the way.

Gigadino
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July 24, 2013

I think that Spinosaurus was larger than the other Theropods because it has a different life style.

Godzillasaurus
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November 28, 2013

Not all spinosaurs were necessarily massive. Only spinosaurus truly attained large sizes (compared to most other large theropods). All other spinosaurs grew to smaller sizes than the largest tyrannosaurids and carcharodontosaurids. The only truly "large" spinosaur was spinosaurus, that is the bottom line, and that is all that needs to be said.

@Deltadromeus, spinosaurus was not necessarily light. It was lightly-built, but it still was not light per-se. Spinosaurus, despite being a generalized piscivore, was actually quite bulky, especially in comparison to baryonichines, which were quite gracile.