New Utahraptor Skeletal Drawing by Scott Hartman!

[CrypticPrism]

We're not saying it had a burrowing niche. We're just saying it made burrows to live in.

Edit:just realized how idiotic that sounded.

[stargatedalek]

I never said there was solid evidence it was a burrower, it's simply one potential explanation for these adaptations (and the only one I've heard thus far, but I'm sure there are others).

We're not saying it had a burrowing niche. We're just saying it made burrows to live in.

And also this.

[suspsy]

I can see how it's possible; I'm just not really convinced by any of the arguments presented thus far. But I could well be wrong.

[Halichoeres]

I don't think it's out of the question that Utahraptor used burrows, but to me it seems as though a hunting strategy consistent with this general build is sufficient to explain the tail morphology. Given that tails and ossified tendons cost energy to make, and given a robust, probably not very fast-moving animal that relies on overpowering rather than overtaking its prey, I wouldn't expect a long, rigid tail to be maintained by selection. I'm not sure ground sloths are a good analog, since the largest one known to have burrowed is Glossotherium, which is only 3 or so meters long and not nearly as formidable as a Utahraptor. Even if there are animals like Acrocanthosaurus or Siats running around, they're probably going to prefer an ornithopod given the likelihood of injury in a scrap with Utahraptor. None of which is to say that anything about this morphology falsifies a burrow hypothesis, but it definitely doesn't require it either.

[Sim]

How would it be a burrower? What would be the advantage of that?

Lack of competition for nesting space, safer from predators, and protection from the elements. Once you're this large running and tree climbing become far less appealing methods of defense, but I doubt Utahraptor had the bulk needed to deter all would be predators.

Utahraptor appears to have been the apex predator in its ecosystem.  James Kirkland has suggested Gastonia might have been so abundant because its armour effectively protected it against the apex predator of its ecosystem, Utahraptor.  Additionally, no larger theropods are known to have coexisted with Utahraptor.  Even if they did and they just haven't been discovered yet, I don't think any would prey on adult Utahraptor given just how formidable we now know Utahraptor was.

[irimali]

i could see utahraptor digging burrows to hide their young in while the adults are off hunting, like a wolf den.  Though I do have a question.  Birds can fold their wings up pretty tight, keeping wing feathers pressed up against the sides of the body.  Couldn't dromaeosaurs only bend their wrists about 90 degrees?  wouldn't their primary feathers get in the way of tunneling?

[Dinoguy2]

i could see utahraptor digging burrows to hide their young in while the adults are off hunting, like a wolf den.  Though I do have a question.  Birds can fold their wings up pretty tight, keeping wing feathers pressed up against the sides of the body.  Couldn't dromaeosaurs only bend their wrists about 90 degrees?  wouldn't their primary feathers get in the way of tunneling?

I don't think anybody is talking about "tunneling" here. Think more like bear dens, maybe not even something they'd be digging themselves, just finding crevices in hillsides. And anyway, primary feathers getting in the way isn't really a problem for flightless species. A lot of ground birds can be seen to have pretty darn beat up wing feathers much of the time. That's what occasional moulting is for.

[CrypticPrism]

i could see utahraptor digging burrows to hide their young in while the adults are off hunting, like a wolf den.  Though I do have a question.  Birds can fold their wings up pretty tight, keeping wing feathers pressed up against the sides of the body.  Couldn't dromaeosaurs only bend their wrists about 90 degrees?  wouldn't their primary feathers get in the way of tunneling?

I don't think anybody is talking about "tunneling" here. Think more like bear dens, maybe not even something they'd be digging themselves, just finding crevices in hillsides. And anyway, primary feathers getting in the way isn't really a problem for flightless species. A lot of ground birds can be seen to have pretty darn beat up wing feathers much of the time. That's what occasional moulting is for.

We're talking about tunneling.

[stargatedalek]

Not necessarily, secondary digging traits are just as common in animals that re-purpose old burrows, such as small tortoises.

[Sim]

I decided to make a separate post for this due to some things I wanted to add.

I don't think it's out of the question that Utahraptor used burrows, but to me it seems as though a hunting strategy consistent with this general build is sufficient to explain the tail morphology. Given that tails and ossified tendons cost energy to make, and given a robust, probably not very fast-moving animal that relies on overpowering rather than overtaking its prey, I wouldn't expect a long, rigid tail to be maintained by selection. I'm not sure ground sloths are a good analog, since the largest one known to have burrowed is Glossotherium, which is only 3 or so meters long and not nearly as formidable as a Utahraptor. Even if there are animals like Acrocanthosaurus or Siats running around, they're probably going to prefer an ornithopod given the likelihood of injury in a scrap with Utahraptor. None of which is to say that anything about this morphology falsifies a burrow hypothesis, but it definitely doesn't require it either.

Well put.  Scott Hartman said, "My best guess is that Utahraptor was using some sort of souped-up raptor prey restraint hunting technique, but for larger prey, hence the ridiculously robust hindlimbs and pelvis. It would also explain the more flexible tail, but that's a tale for another day."  He said this here: http://comments.deviantart.com/1/179491659/4360248481

My guess is surprising features of Utahraptor like the huge head, extremely robust build and more flexible tail are related to a change in hunting behaviour, similar to what you said.   I'm thinking it could be that an increase in prey size meant the prey would also be slower and more heavily built.  So Utahraptor was how it is in order to prey on such animals.  Some things to consider though:

1. There are a few dromaeosaurids besides Utahraptor that don't have the bony tail rods found in many dromaeosaurids, even though their tail morphology may differ from Utahraptor's.  As far as I know, the others known to lack the bony rods are Buitreraptor, Mahakala and Yurgovuchia.
Buitreraptor and Mahakala are gracile, long-legged and small.  Buitreraptor is especially different, having an extremely different head to Utahraptor and being long-armed (Utahraptor and even Mahakala are short-armed).  This shows that three very different dromaeosaurids all lack the bony rods.  I'd been thinking Buitreraptor and Mahakala lack bony rods due to coming from lineages that branched off of the dromaeosaurid family tree before the rods evolved, but I wonder about that now that it's known Utahraptor lacks them too.
Yurgovuchia is also much smaller than Utahraptor, but it appears to have coexisted with Utahraptor and be closely related to it.  I wonder if the lack of bony rods in Yurgovuchia is due to similarity to Utahraptor, perhaps being very similar to what Utahraptor evolved from?  Yurgovuchia is known from scraps though, so there's not much I can say about it.

2. Achillobator appears to be similar to Utahraptor, being robust, short-legged and close in size.  I get the impression that like Utahraptor, Achillobator was very strong and not a very fast runner.  However, Achillobator has bony tail rods.  I wonder if Achillobator hunted similar to Utahraptor, but the different ecosystems they lived in relates to Achillobator possibly being less robust than Utahraptor and having bony tail rods?  I hope more of Achillobator will be found in the future!

[CrypticPrism]

I just realized something. The papo feathered velociraptor makes a perfect utahraptor: chunky body, short tail, and a wonky lower jaw.

[Sim]

I just realized something. The papo feathered velociraptor makes a perfect utahraptor: chunky body, short tail, and a wonky lower jaw.

That figure doesn't look like Utahraptor.  Comparing the figure to Scott Hartman's Utahraptor skeletal:  The figure's head is a very different shape, longer and shallower compared to Utahraptor's head and it doesn't have the forward pointing teeth at the front of the lower jaw.  Its torso is shallow, not deep like Utahraptor's.  Its fingers don't look like Utahraptor's.  Its pubis is 'backward-pointing', not 'vertical' like Utahraptor's.  In all these areas, that Papo figure looks like Velociraptor.

[suspsy]

Yeah, just the head alone kills the Papo figure's chances of passing off as Utahraptor.

[danmalcolm]

I would say its the best option available, currently. As far as I'm aware.

[Takama]

I would say its the best option available, currently. As far as I'm aware.

ITs a Velociraptor through and through.   Saying that it makes the best Utahraptor  is like useing a House Cat in place of a lion

The Rebor modl (despite its MANEY and i mean MANEY shortcomeings)   is a better model to use

[CrypticPrism]

Not exactly. It's got similarities of both. More like having a lion to be a liger.

[Takama]

Lets compare the heads



Skull of the Real animal


Now how does that compare to the Utahraptor Skeletal?



In my eyes, they dont hold up.

[CrypticPrism]

Okay.

[Takama]

FYI dont take this the wrong way. nothing is stopping you from pretending its a Utahraptor anyways

[CrypticPrism]

Okay, thanks. I was gonna star him as a utahraptor in a DI- style series I'm doing.