[Adam Khor]

Ok, so, lately I've been hearing rumours about a certain Spinosaurus specimen (a skull, supossedly) known as the Tucson Rock Show specimen, which would be in a private collection and thus not available for study. According to some, this creature had a 2.5 meter long skull, which would supossedly suggest an overall lenght of up to 25 meters long.
In interviews for Jurassic Park III, Jack Horner mentioned a 2.5 meter long Spinosaurus skull so this may be the same specimen, although he didn´t give much info on it.

Here's a scale showing the estimate sizes of several Spinosaurus specimens, the Tucson Rock Show specimen is shown in green. The smaller ones seem to be reconstructed with short legs as suggested by recent finds.




Some say that a 25 meter long Spinosaurus would weigh up to 30 tons, which would render it too heavy and slow. But then there's the question, too heavy and slow for what?
It would certainly not be running at high speed after prey, but did it need to? The latest theories indicate that it was a semi-aquatic animal, so it may have spent lots of time in the water where weight wouldn´t be so much of an issue. Even more, if paleontologists are correct and dinosaurs were much more light weight than usually thought, it may be that a 25 meter long theropod wouldn´t weigh as much as we imagine, and thus not be so greatly hindered by size.

There's also a bunch of Tyrannosaurus rex specimens said to be much larger than currently accepted, including a toe bone that comes from a specimen probably 15 meters long.
Again, many say such a giant would be hindered by its enormous weight, but I believe if it was an ambush hunter it wouldn´t be much of a problem. The larger a theropod would grow, the larger the prey it could catch (and the more attractive large prey would be) so it wouldn´t necessarily be a limitation IMHO.

So I start this thread for two reasons. One, to see if any of you has ever heard about this mysterious giant specimen, and two, to know what you think about the possibility of Spinosaurus reaching such a monstrous size, or even, of any theropod reaching such sizes.

[Kess73]

Saw the Horner interview for JPIII, but I tend to have an aversion to anything he says.


As for the weights you mentioned, and how it would potentially impact upon how the predators lived/hunted, I would more or less fall into the same line of thinking as yourself.


Large potential prey generally means large predators.

Then again to say a 25m Spino would weigh 30 ton is to use older methods of calculating weight, so using the newer method a 25m spino might be coming in around the 10 ton mark or lighter. Personally I think the newer method is flawed but we have already had that chat in another thread.

The semi aquatic theory backs the idea of a heavy animal, one that could prey on other aquatic/semi aquatic animals as well as being capable of ambushing animals that came to the water source to drink.

T Rex I would also think of as an ambush predator, and one that needed a fair bit of size/weight to be effective.

Then again people will come out and say that a heavy predator is too slow, but as you rightly point out, too slow for what? A predator does not always need to be quicker than it's prey, studies on extant creatures shows us that. A predator that uses ambush as a hunting technique generally does not have the ability to engage in a chase over distance, so why should it have been much different for extinct predators. A big Rex might have been the type to bite and release and then just follow the injured animal's trail until it dropped from shock/blood loss, or it may have been the type to bite and overpower quickly, but each scenario would require a fair bit of power/weight to ensure that the jaws had enough force behind them to do the right amount of damage.

[Galvasean]

Read this after coming home from the sauce at about 4am. Thought I was dreaming so didn't respond. Certainly a 25 meter, 10+ tonne Spinosaurus could have been a formidable ambush hunter like today's crocodiles (as it has been proven that Spinosaurus spent a lot of time in water). At that size one would imagine it could attack everything up to mid sized sauropods.
I'm speculating here, but if Spinosaurus' lifestyle was s much like a crocodile's then perhaps its mature size was just as varied? Mature adult sizes in individual crocodile species vary wildly based on how much food they eat and how much space they have. Maybe Spinosaurus averaged in at close to 15 meters as adults, with the occasional monster showing up from time to time that far exceeded the regular adult size.

[Kess73]

Originally Posted by Galvasean

Read this after coming home from the sauce at about 4am. Thought I was dreaming so didn't respond. Certainly a 25 meter, 10+ tonne Spinosaurus could have been a formidable ambush hunter like today's crocodiles (as it has been proven that Spinosaurus spent a lot of time in water). At that size one would imagine it could attack everything up to mid sized sauropods.
I'm speculating here, but if Spinosaurus' lifestyle was s much like a crocodile's then perhaps its mature size was just as varied? Mature adult sizes in individual crocodile species vary wildly based on how much food they eat and how much space they have. Maybe Spinosaurus averaged in at close to 15 meters as adults, with the occasional monster showing up from time to time that far exceeded the regular adult size.

Yep and that is just one of the reasons why I disagree with the new method of gauging the weight of extinct reptiles and other extinct animals.

If one is to look at Crocs, then a 15 ft Nile croc can weigh 500lbs, but a 15ft Nile croc can also weigh 1,500lbs and not have a huge difference in skeletal terms to the 500lbs croc. Spino could have been similar.

Totally agree with the idea of there being an average size with the occasional monster popping up every now and then. It pretty much happens with every animal on the planet, and I see no reason why the same did not happen with every extinct species as well.

[Adam Khor]

I totally agree with you guys. In fact, I remember reading about prosauropods- Plateosaurus, was it?- that varied enormously in size even in adulthood, probably because of the factors you mention- available food, etc. If I'm not mistaken there's huge variation in size in Allosaurus as well.

Now, a 25 meter long Spinosaurus IS quite a bit larger than any other specimen known but then again, how many Spinosaurus specimens do we know?
Last time I checked, they were less than ten, all of them very fragmentary. I seriously doubt we can have a good idea of the size range of an animal with less than ten partial specimens. It would be too much coincidence that we found the remains of the very largest individuals ever.

[Galvasean]

Originally Posted by Adam Khor

If I'm not mistaken there's huge variation in size in Allosaurus as well.

As far as I know most Allosaurus did not reach their maximum size due to living difficult lives, (Spending your days fighting the likes of Diplodocus and Stegosaurus isn't easy on the old bones.) with very few reaching their maximum size. Giant genera previously attributed to the likes of Epanterias and Saurophaganax are apparently just fully mature Allosaurus.

[Adam Khor]

Originally Posted by Galvasean

As far as I know most Allosaurus did not reach their maximum size due to living difficult lives, (Spending your days fighting the likes of Diplodocus and Stegosaurus isn't easy on the old bones.) with very few reaching their maximum size. Giant genera previously attributed to the likes of Epanterias and Saurophaganax are apparently just fully mature Allosaurus.

Actually, the last study did recognize Saurophaganax as a separate genus. Epanterias on the other hand does seem to be Allosaurus.

[Galvasean]

Originally Posted by Adam Khor

Actually, the last study did recognize Saurophaganax as a separate genus.

I guess Planet Dinosaur was right after all. Do you have a link to said study or at least a run down of it?

[Adam Khor]

Originally Posted by Galvasean

I guess Planet Dinosaur was right after all. Do you have a link to said study or at least a run down of it?

I don´t... I do remember it was by Thomas Holtz if not mistaken. I'll try to find it again.

[Galvasean]

Originally Posted by Adam Khor

I don´t... I do remember it was by Thomas Holtz if not mistaken. I'll try to find it again.

Had a peek at Wikipedia and apparently Currie was involved too. It's detailed in their latest version of the book 'The Dinosauria'. Been meaning to buy a copy of that for ages. It aint cheap though!

[Adam Khor]

Originally Posted by Galvasean

Had a peek at Wikipedia and apparently Currie was involved too. It's detailed in their latest version of the book 'The Dinosauria'. Been meaning to buy a copy of that for ages. It aint cheap though!

Welcome to my world. I have literally dozens of books in my "wish list" and not enough money to order even one of them. :S