Dimetrodon's sail

[Bowhead Whale]

The Ouranosaurus head may be big like that, but look at it compared to the body: it is pretty small. Way too small to necessitate long spines for muscle anchors for it! Horse have a much bigger head compared to their body and they don't have exaggeratedly long spines to have muscles to lift it. Those spines look way too exaggerated for the head just to be a purpose to attach muscles. It's like if Tyrannosaurus had big shoulder muscles to lift its tiny arms. To me, it looks like that. So, to me, it MUST have had another purpose. If not, there is too much of a contradiction there. No?

There is no contradiction. Animals have muscles because they use them, those muscles don't have to be literally supporting the weight of the head, they could also facilitate behaviours such as methods of feeding.

True, but big muscles are most of the time attached to big limbs, necks or heads. Not to small limbs, necks or heads.

[GojiraGuy1954]

it may also have benefits of keeping you warm when you're submerged.  However a sail is not useful if you are an ambush predator nor is it really useful for swimming under water, as it would act like a big, upside down keel creating resistance during lateral movement.

Stargatedalek: I looked at the Ouranosaurus skeleton and it seems to have long spines running the entire length of the back; maybe i'm just not understanding what you mean by 'forward facing'.

The sail is not a problem of ambush when you eat fish: fish do nont necessarily look at what is above water, unless they feed on insects. Spinosaurus skull has many holes on it like sharks and crocodiles. These holes were pressure sensors, like those of those modern animals. That means Spinosaurus ate fish, not land animals. No?

As for talking about Spinosaurus, well, I don't think we can understand the frill of Dimetrodon if we don't compare it with sails of other animals. When we want to understand a feature, we look at other animals with a similar feature. No?

These are not similar features. Spinosaurus had very large broad extensions of its vertebrae. These are broad as they are in bison and rhinoceros because they are attachments for musculature. Dimetrodon and kin have tiny thin shafts extending from the vertebrae, not large segments extending vertically. They are like the sail supporting structures of basilisks and similar lizards.

But the Spinosaur sail is so round shaped... what muscles could it support on the middle of the back? No, there is something else behind it, for sure.

Have you looked at rhinoceros or bison skeletons for reference?



It's plenty round, if not more round, and extends pretty far along the back. The musculature these structures support are somewhat sprawling, the intention is that they provide surface area to just lay out as many muscles as possible stretching out horizontally along the whole length of the back.

Bison and rhino skelettons show the roundness of the spines at the level of the SHOULDERS. The Spinosaurus' skeletton's spines show the roundness of the spines at the level of the MIDDLE OF THE BACK. If they were for muscle attachment, we would see the roundness at the shoulders and/ or at the hips. Not the middle of the back.

Have you seen a Spinosaurus skeleton lately? They are round over the shoulders and hips.

Look at the bison skeleton again, then back at these. The bisons spines are longer all the way into the middle of the back, despite being largest around the shoulders. Spinosaurus has large muscle attachments at the shoulders and at the hips, the high spines in the middle are also there on the bison just less obvious because it doesn't have higher sections on both ends.

The M sail is speculative

[stargatedalek]

The M sail is speculative

Less speculative than Hartmans weird sail everyone jumped on because they wanted to use his reconstruction that had longer legs.

[GojiraGuy1954]

The M sail is speculative

Less speculative than Hartmans weird sail everyone jumped on because they wanted to use his reconstruction that had longer legs.

I despise Hartman's skeletal

[Bowhead Whale]

The M sail is speculative

Less speculative than Hartmans weird sail everyone jumped on because they wanted to use his reconstruction that had longer legs.

Why would they want to do that? Why would anyone "want" an extinct animal to look like "this" instead of "that"?

[Rexy]

I'm leaning towards a combination of uses for the sail, both display and thermoregulation, but how about the possibility of the sail being used to help individuals recognize members of their own species? Perhaps the sail on each of the different species was a slightly different shape or size.

[Bowhead Whale]

I'm leaning towards a combination of uses for the sail, both display and thermoregulation, but how about the possibility of the sail being used to help individuals recognize members of their own species? Perhaps the sail on each of the different species was a slightly different shape or size.

Maybe... but why develop such a huge, complicated feature if it is just for recognition? Couldn't a single color pattern be sufficient to do so?