rexy's got back

[paleoferroequine]

According to newer research, estimates of T.rex muscle mass in the tail may be off by as much as 45%. So time to redraw stuff yet again. ;D
www.physorg.com/news/2010-11-rex-big-tail-key-prowess.html
Also see discussion at the Dino Mailing List.

[sid]

So it means he could run faster than previously thought, and maybe he could have been able to chase, say, a jeep, eh? ;D

[Griffin]

Hmm. Well on land birds like ostriches are those muscles present? That would be a better model than crocodiles and lizards I would think. And I would assume that this applies to pretty much all theropods not just rex?

[paleoferroequine]

Nov 19, 2010 22:53:02 GMT Griffin said:

Hmm. Well on land birds like ostriches are those muscles present? That would be a better model than crocodiles and lizards I would think. And I would assume that this applies to pretty much all theropods not just rex?

Well, I'll let others more experienced discuss this but ostriches don't have big tails to attach those muscles to. There is physical evidence for these enlarged muscles not just an idea. It would probably apply to other theropods also(all? some? Don't know)

[Griffin]

In the case of an ostrich or other large ground bird, they have a tail its just not that long. And there are large muscle attachments there for running.

Also keep in mind that with crocodillians and lizards, there is no pressure to keep that tail lifted above the ground so it can probably afford to be pretty heavy cuz its just dragging on the ground anyway. Also their tails are used as weapons and in the case of the crocodile, its a primary source of propulsion when in the water (they freakn launch themselves out of the water with tail power alone!) so its no surprise that there are huge muscles there. But theropods....I dunno.

[fooman666]

ahhh, so were back to the fast agile tyrannosaurs now hey, lets see how long it takes for jack horner to make something up about how this also points to it being a scavenger

in all seriousness it is a rather interesting article.

[sid]

Nov 20, 2010 7:02:38 GMT Griffin said:

But theropods....I dunno.

Why? Bear in mind that mesozoic big theropods had long and heavy tails closer to crocodilians than to ratites (heck, you can't compare an ostrich pygostile to, say, an Allosaurus tail!), so it's very likely they had HUGE muscles down there

[foxilized]

Couldn't they have used the tails for swimming too?

At least the spinosauroids could have been amphibians just like crocs... Are there any differences in the tail vertebrae between spinosauroids and other theropods?

[Horridus]

Nov 20, 2010 13:40:15 GMT foxilized said:

Couldn't they have used the tails for swimming too?

Certainly!

This study adds to the evidence that Tyrannosaurus wasn't a slouch. While you can only go so fast when you weigh 6 tonnes, I think Greg Paul makes an excellent point when he says that Tyrannosaurus' legs are clearly far better adapted for fast movement than, say, an African elephant of similar weight.

[Griffin]

"Why? Bear in mind that mesozoic big theropods had long and heavy tails closer to crocodilians than to ratites (heck, you can't compare an ostrich pygostile to, say, an Allosaurus tail!), so it's very likely they had HUGE muscles down there"

Crocodillians use depend on their tails for swimming. Its their primary form of locomotion when in the water. I said it already but I'll say it again they launch themselves clear out of the water from a stand still using the tail muscles alone. So its a no brainer why their tails are so thick with muscle. Monitor lizards use their tails as weapons and like croc's they use them for swimming- same concept. Theropod dinosaur tails on the other hand were not flexible really, actually they were quite stiff. If you ask me they were really only there for balance and the base of it was used for big muscle attachments from the legs, sure. But keep in mind that unlike crocs and lizards they didn't drag them along the ground they needed to keep them up above the ground so really how heavy could they have been? I wouldn't go assuming that tyrannosaurus and allosaurus had big wide tail bases like a croc. They weren't crocodiles. Sure they are relatives but they had totally different body designs.

"Couldn't they have used the tails for swimming too?

At least the spinosauroids could have been amphibians just like crocs... Are there any differences in the tail vertebrae between spinosauroids and other theropods?"

As far as I know body-wise, nothing really sets spinosaurs apart from other theropods as being amphibious. Really the only thing they have in common with crocodillians is the long snout, and even that is pretty different if you really look closely. Honestly, if you ask me, they were most likely wading around in shallow water and striking fish out of the water with their snouts and claws like a giant heron or grizzly. Think about it, everything about a crocodillian is designed for being a water predator. Their eyes, ears and nostrils are at the top of their heads, they have very flexible spines and tails. A spinosaur, just like most other theropods is laterally compressed body-wise, they had long legs for walking/running, the vertabrae were NOT flexible at all. In fact dinosaur spines were rather rigid in general. The eyes and nostrils were not at the top of the skull they are on the sides like most other dinosaurs. IMO spinosaurs were not swimming around under the water like crocodiles. They were designed for walking around on the land just like other theropods.

Now do I think theropods could swim if they wanted to? Yes absolutely. But I don't think any of them would have been considered amphibious and super agile and fluent in the water. I think they could probably swim on the surface of the water to get from place to place, but if you look at their body design, they were really land animals.

The only theropod dinosaur that I think would have been a better than average swimmer that I can think of is Ceratosaurus. Its tail was actually much thicker and more flexible than the average theropod's.

[Horridus]

Plus don't forget that crocodilians were already filling that amphibious ambush predator niche.

[Griffin]

Nov 20, 2010 19:26:42 GMT Horridus said:

Plus don't forget that crocodilians were already filling that amphibious ambush predator niche.

Exactly.

[sid]

Nov 20, 2010 19:23:58 GMT Griffin said:

. Theropod dinosaur tails on the other hand were not flexible really, actually they were quite stiff.

Mostly agree with ya except for this point: theropods' tails were not as flexible as a lizard or even a croc, granted, but frankly i don't agree with the notion that their tails were stiff as a rod, unable to bend and such... That's just nonsense, considering that paleontologists even found a Velociraptor Mongoliensis tail bent in an S- shape (and they determined that it wasn't a tafonomic artefact, if i remember well the study)!

I'm not saying a Rex could swirl his tail "a là Harryhausen" ( ;D), but surely he hadn't a totally rigid rod-like tail stickin' out his ass

[Griffin]

Nov 20, 2010 20:54:32 GMT sid said:

Nov 20, 2010 19:23:58 GMT Griffin said:

. Theropod dinosaur tails on the other hand were not flexible really, actually they were quite stiff.

Mostly agree with ya except for this point: theropods' tails were not as flexible as a lizard or even a croc, granted, but frankly i don't agree with the notion that their tails were stiff as a rod, unable to bend and such... That's just nonsense, considering that paleontologists even found a Velociraptor Mongoliensis tail bent in an S- shape (and they determined that it wasn't a tafonomic artefact, if i remember well the study)!

I'm not saying a Rex could swirl his tail "a là Harryhausen" ( ;D), but surely he hadn't a totally rigid rod-like tail stickin' out his ass

I didn't say that. I said they were quite stiff. Certainly not flexible like a crocodile's or a lizards both of which use their tails for very specific things.

[[][][]cordylus[][][]]

Nov 20, 2010 20:54:32 GMT sid said:

Nov 20, 2010 19:23:58 GMT Griffin said:

. Theropod dinosaur tails on the other hand were not flexible really, actually they were quite stiff.

Mostly agree with ya except for this point: theropods' tails were not as flexible as a lizard or even a croc, granted, but frankly i don't agree with the notion that their tails were stiff as a rod, unable to bend and such... That's just nonsense, considering that paleontologists even found a Velociraptor Mongoliensis tail bent in an S- shape (and they determined that it wasn't a tafonomic artefact, if i remember well the study)!

I'm not saying a Rex could swirl his tail "a là Harryhausen" ( ;D), but surely he hadn't a totally rigid rod-like tail stickin' out his ass

Velociraptor had ossified tendons running the entire length of it's tail along it's vertebre, on the top and the bottom I believe. When there's tendons there as hard as bone, I don't think there's much bending that can happen there.

I'd like to think of rexy as being that badass who chased the jeep at 45 mph in JP but... I think I'm leaning more towards griffin's side of things here.

[stoneage]

Dr. Manning, who studied the Dinosaur Mummy Dakota, an Edmontosaurus, claims it was faster then Tyrannosaurus rex. The Hadrosaurs enormous hindquarters appeared to be 25 % larger then previously thought. He estimated it could run at a speed of 28 MPH which is 10 MPH faster then T-Rex. However others have pointed out that T-rex had much longer ankle bones then Hadrosaurs which had a similiar leg mechanism. The same holds true in lions and cheetahs. The cheetah has longer ankle bones then a lion and can run at 70 MPH compared to a lion which can almost reach 40 MPH. So I don't think we can be sure.
At one time they thought that sauropods had stiff necks, but now their saying they don't. So how can you be sure if the tail was stiff.
Also Dr. Manning found that Dakota had about a centimeter between each vertibrae, instead of being snug like many museum restorations, which could add at least a meter to some dinosaurs length.
Dakota also had a skin envelope that shows evidence that the Hadrosaur may have been striped and not block colored. This could have produced a striped camouflage pattern on some parts on the dinosaur.

[Griffin]

"At one time they thought that sauropods had stiff necks, but now their saying they don't. So how can you be sure if the tail was stiff."

In the case of velociraptor it would be the presence of ossified tendons. That would make it relatively stiff. Perhaps not like a wooden stick, but still quite stiff. Tyrannosaurus wouldn't have been this stiff but it def wouldn't be as flexible as a crocodillian's.

[foxilized]

Nov 20, 2010 19:23:58 GMT Griffin said:

But keep in mind that unlike crocs and lizards they didn't drag them along the ground they needed to keep them up above the ground so really how heavy could they have been?

Oh but unlike crocs and lizards, the theropods were supposed to "use" the tail to equlibrate the rest of the body, right? Being almost totally horizontal needs a sorta heavy tail at the end, I suppose. Otherwise the animal would bite the dust as happens with many of our figures wich aren't correctly equilibrated.

Nov 20, 2010 19:23:58 GMT Griffin said:

Honestly, if you ask me, they were most likely wading around in shallow water and striking fish out of the water with their snouts and claws like a giant heron or grizzly. Think about it, everything about a crocodillian is designed for being a water predator. Their eyes, ears and nostrils are at the top of their heads, they have very flexible spines and tails. A spinosaur, just like most other theropods is laterally compressed body-wise, they had long legs for walking/running, the vertabrae were NOT flexible at all. In fact dinosaur spines were rather rigid in general. The eyes and nostrils were not at the top of the skull they are on the sides like most other dinosaurs. IMO spinosaurs were not swimming around under the water like crocodiles. They were designed for walking around on the land just like other theropods.

That's very interesting and sounds pretty reasonable. I tended to think the crocodilian snout was a proof enough to consider them semi-aquatic, but it's also true they could have used the snout to catch the fishes from land, sumerging the head only. Instead of swimming after fishes, they waited for them to come close... The claw as a hook to catch fishes also sounds pretty reasonable -and fits with them being landish fishers-.
The only thing that still puzzles my mind is, unlike the Grizzlies -who fishes only once in a while- the Spinosaurids seem to be very spezialiced into fishing. The hook, the snout... This implies they were MAINLY fishers. Now, this means they eat A LOT of fish to survive, and if they were actually PASSIVE fishes -waiting for them to come close- this takes a lot of time and not too many catches... Right? If they swam after the fishes, then they could probably get more than just waiting... Isn't it?
Yes, I know they probably were also scavengers when needed, but their designs seems to imply they were primarily fishers, so how's that?
Were the fishes on the mesozoic so easy to catch?
Or is that they were so huge that one catch a day was enough?

Sorry, I'm getting really off-topic...

[sbell]

Nov 21, 2010 3:59:58 GMT foxilized said:

Nov 20, 2010 19:23:58 GMT Griffin said:

But keep in mind that unlike crocs and lizards they didn't drag them along the ground they needed to keep them up above the ground so really how heavy could they have been?

Oh but unlike crocs and lizards, the theropods were supposed to "use" the tail to equlibrate the rest of the body, right? Being almost totally horizontal needs a sorta heavy tail at the end, I suppose. Otherwise the animal would bite the dust as happens with many of our figures wich aren't correctly equilibrated.

Nov 20, 2010 19:23:58 GMT Griffin said:

Honestly, if you ask me, they were most likely wading around in shallow water and striking fish out of the water with their snouts and claws like a giant heron or grizzly. Think about it, everything about a crocodillian is designed for being a water predator. Their eyes, ears and nostrils are at the top of their heads, they have very flexible spines and tails. A spinosaur, just like most other theropods is laterally compressed body-wise, they had long legs for walking/running, the vertabrae were NOT flexible at all. In fact dinosaur spines were rather rigid in general. The eyes and nostrils were not at the top of the skull they are on the sides like most other dinosaurs. IMO spinosaurs were not swimming around under the water like crocodiles. They were designed for walking around on the land just like other theropods.

That's very interesting and sounds pretty reasonable. I tended to think the crocodilian snout was a proof enough to consider them semi-aquatic, but it's also true they could have used the snout to catch the fishes from land, sumerging the head only. Instead of swimming after fishes, they waited for them to come close... The claw as a hook to catch fishes also sounds pretty reasonable -and fits with them being landish fishers-.
The only thing that still puzzles my mind is, unlike the Grizzlies -who fishes only once in a while- the Spinosaurids seem to be very spezialiced into fishing. The hook, the snout... This implies they were MAINLY fishers. Now, this means they eat A LOT of fish to survive, and if they were actually PASSIVE fishes -waiting for them to come close- this takes a lot of time and not too many catches... Right? If they swam after the fishes, then they could probably get more than just waiting... Isn't it?
Yes, I know they probably were also scavengers when needed, but their designs seems to imply they were primarily fishers, so how's that?
Were the fishes on the mesozoic so easy to catch?
Or is that they were so huge that one catch a day was enough?

Sorry, I'm getting really off-topic...

It's more a matter of what the fish were--we are not talking about 6" pan fish here--they would have been more along the lines of 5-6' sharks, lungfish, coelacanths, Lepidotes and other huge fish. Plus, of course, turtles, crocs, etc. Put it all together and the menu was fairly large (in diversity and size). And I doubt they would turn away from a land-based prey item either.

[Seijun]

Sometimes I look at these threads just to see who wrote the biggest paragraph.