Comments on: Was Spinosaurus a Bison-Backed Dinosaur?

By: Ron-O-Saur

Ron-O-Saur — Sat, 21 Jul 2012 16:38:19 +0000

I think the hump-theory is basically rigth,
it works fine on the other spinosauridae family members,
as well as on Ouranosaurus.
But not on Spinosaurus himself.
If you look at their neural spines
the proportions are in range of present-day animals,
and as far as i can see they also have a concave shape.
So you put muscles at the sides,
and on the top you can run ligamentum supraspinale.
But if you look at these spines :

http://en.wikipedia.org/wiki/File:Spinosaurus_vertebrae.png

beside just appearing too long,
they don’t get wider at the top,
so you can hardly run the ligament there.
One of the neural spines also shows a deformation
in the upper third.
If this happened already during lifetime,
then muscles that were attached there could have caused problems.
Of course spinosaurus should have had some muscles,
but maybe a part, lets say this upper third, was exposed.
So what could be the reason for this ?
I think this could have been the ligamentum supraspinale.
In accelerated evolution it could look like this :
at one spinosauridae member the neural spines started to grow,
and became thinner, the bone mass was distributed in a different way.
This cut through the ligament,
but this sticked to the sides and widened where it was connected now,
coating the protruding part of the spines,
and allowing a more even distrubution of the stress.
So deformations at these tips weren’t so importand,
because they must be able to resist forces from the direction of the head,
but not downwards towards the spine, as muscles would cause.
This contruction should result in a highly elastic creature,
wich could be desireable for a fulltime fishlifter.
The tips itself could be covered with something like gristle,
adding some protection.

For the other spinosauridae i don’t see a reason for
exposing neural spines.
At suchomimus they are high compared to other theropodes,
but these proportion are common in dolphins,
so maybe he could move somewhat like them.
A flattened tail as beavers or maniti have could fit to this.
At irritator it’s somewhere between suchomimus and
spinosaurus.
But he was smaller than them, so maybe he could face fishlifting
without this modification.

At ouranosaurus i expect that this was for digging.
The proportions are between pig and buffalo.
His head was more shovel-shaped compared to his relatives,
and also reinforced( between eyes and nostrils ).
Having a hump between the shoulders as well at the hip
would let him choose between two-and forlegged digging,
wich should result in a greater variety of possible angles.

And this camel-back theory is odd, look at a camels neural spines,
and then try to attach such a hump over the spines of spino or ou..

By: dave14

dave14 — Thu, 20 Oct 2011 01:18:51 +0000

There’s talk on the web about new Spinosaurus remains found, including, for the first time, the hindlimbs! According to some, this awesome Spinosaurus model (from the “Dinossauri in carne e ossa” exposition from earlier this year in Italy) is actually based on those new remains.

https://lh4.googleusercontent.com/-oYhQwbOs8Ko/TXQI3n8Jc1I/AAAAAAAAANg/090o2SVpqDI/spino%2521.jpg

Looks like they mostly water born dinos and that they walked on all fours.

By: Tim Dunnicliff-Wells

Tim Dunnicliff-Wells — Mon, 08 Aug 2011 10:36:56 +0000

Whether a hump or sail, if Spinosaurus was wading to catch things in the water then having a significant weight above the water would help it counteract the buoyancy of the lower half of the body in the water. This would help the legs grip the bottom giving it an advantage chasing fish or other smaller animals that might have been crossing a river, especially if the prey was swimming and Spinosaurus was able to grip the bottom and move against (or stand still in) a current. This would be a bit like crocodiles ambushing wildebeest etc crossing rivers today, except the crocodiles rely on being strong swimmers not their size and long legs. If this is the case then I suppose it would help to have a heavier hump than a lighter sail. How much it would help or hinder having heavy hump is the question. Heavy sail? Thin hump?
Having robust arms would also help a Spinosaurus that hunted in shallow water because it might have been scrambling and tripping more while hunting or just getting out of the water.
This doesn’t necessarily explain why Ouranosaurus would need this feature, except possibly to escape predators in a similar fashion. I expect that there was no single use for the hump/sail, that it was just a feature that proved to be useful, possibly even for storage, display thermal regulation and (maybe) ballast.

By: Petrina Kleid

Petrina Kleid — Mon, 13 Jun 2011 00:44:03 +0000

A hump make sense!
Maybe the hump was actually a form of protection. If the Dimetrodon had the same bacteria fighting abilities that the crocodile has, then maybe having a large mass of flesh at the top of their bodies for predators to bite at, meant their vital organs were safe, lower down towards the ground. Their limbs are so strong, they seem tough enough to carry a large mass about. They also have huge scapulas! They may have crouched very low to the ground, when approached by a predator, and so they were protected. They also have very small necks, as if to minimize the area around the neck for a predator to bite.
Having flesh around the bones makes sens, since the bones seem like they would be too fragile, simply rising up off the backbone the way they do.

By: JerkyD

JerkyD — Thu, 09 Jun 2011 04:30:29 +0000

The following quote sums up my opinion on the matter.

Naish ( http://scienceblogs.com/tetrapodzoology/2010/09/concavenator_incredible_allosauroid.php ): “I have one more thing to say: what were the tall neural spines for? Ortega et al. (2010) conclude that we just can’t say, though they note that thermoregulatory, display or energy storage functions have all been suggested. I tend to prefer the display option, but only by analogy with the extant tall-spined reptiles that everyone seems to ignore whenever they talk about tall neural spines. Sure, maybe these structures were partially buried in fat or muscle, but the implication from some that they simply must have been like this, and that the existence of ‘dorsal sails’ is a total no-no (Bailey 1997) ignores the fact that all tetrapods aren’t mammals. There are living reptiles with dorsal sails: I really must get photos of sail-backed chameleon neural spines some time [adjacent photo shows body of Meller's chameleon Chamaeleo melleri - best I can do at short notice. Photo by Adrian Pingstone, from wikipedia].”

By: Dan Peterson

Dan Peterson — Tue, 07 Jun 2011 15:04:56 +0000

Bailey is essentially right, for the rather broad nature of these neural spines suggest a great deal of tissue HAD to be attached to them, much like a Bison. So if it is indeed a ‘sail’ and not a ‘hump’, it is going to still be a rather thick, meaty hump, much like the spinosaur in Jurassic Park. So like it or not, and even if it were used for sexual display, the structure would have added a fair amount of weight to the creature, even in ‘lean’ times. Even though Spino lived in a lush enviroment, there may have been times of feast and famine just as with some modern Nile Crocodiles, who take in most of the year’s calories in a bare few days time when migratory herds must cross their river. Likewise, there may have been a time of year when the spinos enjoyed a great feast, and evolved another place to store it in addition to flanks and tail.

As for Ouranosaurus, it’s sail may have evolved through the success of a herbivore ‘mimicing’ a dangerous predator. Those Ouranosaurs with the tallest spines resembled a deadly spinosaur and were therfore the most likely to survive and pass on their genes.

By: Dr.Dino

Dr.Dino — Mon, 06 Jun 2011 22:58:19 +0000

Nature rounds around sex. When a feature doesn’t “scream” an obvious function it usually used for mating roles.