Defenses of dinosaurs without obvious weapons

[Infinity Blade]

Nima (Paleo-King) described the teeth of Giraffatitan as having sharp tips and akin to railroad spikes or bodkin arrowheads (thus believing it could actually bite predators).

antediluviansalad.blogspot.com/2014/10/thus-spoke-zarafasaura.html
svpow.com/2011/03/06/sauropods-stomping-theropods-a-much-neglected-theme-in-palaeo-art/

Do you guys think this is an accurate description?

Also, he says the head of Giraffatitan was large. It certainly would have been large in absolute terms, but does anyone know exactly how large it was?

Edit: read it again. Apparently a juvenile has a skull ~3 feet long, but Nima doesn't give a figure for an adult.

[blaze]

According to Janensch (1950b), the skull of the mounted Giraffatitan is 77cm long.

[creature386]

As for biting sauropods:
svpow.com/2011/11/28/accurate-vs-familiar-vs-usual-in-paleoart/
As noted here on SVPOW, if you want to imagine prehistoric animals, you can let them do them all that is physically possible and not utterly nonsensical (the article listed various examples for unusual behavior of animals today). So, biting was certainly possible and may have made some sense, but I personally believe that it was still extremely rare (if it was used) due to its inefficiency and the fact that using head/neck blows would have been an a lot more useful alternative in pretty much all situations I can imagine (unless the Sauropod for some reason wants to immobilize the predator in which case biting would be without an alternative, but I don't see why this should be done).

[Infinity Blade]

Here is some interesting information regarding the flexibility of ornithopod tails and ossified tendons. The use of the tail as a defensive weapon in hadrosaurs is an idea sometimes pooh-poohed because it is intuitively reasoned to have been stiffened by the ossified tendons (which, to be fair, is understandable). Apparently, though, there is no evidence that these would have affected lateral tail movement (Organ, 2006).

The semiaquatic hypothesis posits that the lattice of ossified tendons stiffened the tail mediolaterally (Norman 1986). Iguanodontoidean dinosaurs (hadrosaurs, iguanodons, and relatives) have not been viewed as semiaquatic animals for some time now. Still, reevaluating the ossified tendon evidence for this claim may be informative. For example, although current taphonomy and anatomy suggest that these animals occupied a terrestrial habitat, ossified tendons could still have played a functional role in swimming ability or in antipredator behavior through mediolateral support of the tail. Such ideas can be addressed by examining the results of loading the Tenontosaurus and Brachylophosaurus tails in the mediolateral direction (Table 2). The models provide no evidence that ossified tendons affected lateral tail undulations. The tendons must be located laterally distal to the spinous processes to have any effect on the tail of the Tenontosaurus model. But lateral placement of the tendons has virtually no effect on the Brachylophosaurus model. Regardless, comparative anatomy places these tendon networks near the spinous processes. Therefore, intratendinous ossification in Tenontosaurus and Brachylophosaurus likely had little effect on mediolateral caudal movements. This is because the architecture of the tendon networks in both animals is confined primarily to the parasagittal plane. These results do not suggest that the tail was not used for swimming or antipredator behavior, only that ossified spinal tendons do not appear to be adaptive in either capacity.

[Infinity Blade]

A couple questions about sauropods:

1.) I read that sauropods may have used their tail tips to aim for the eyes of attacking theropods (link 1, link 2). In the second link (SV-POW), Matt Wedel speaks especially of diplodocids and their tail whips, although the first link (a book that Wedel contributed to) says "With or without these structures" the tail tip could be aimed at the teeth and eyes (do "these structures" include the exceptionally thin and supple diplodocid tail ends?). He also implies that having an eye knocked out may be a potential consequence of such an attack. If sauropods did this, wouldn't this suggest that sauropods could and would have been quite a threat to even animals as big as they were? For example, if a Kaatedocus (I don't actually know how massive it was, but I've gotten the impression that it's on the small side for a sauropod) was confronted by a Saurophaganax, is it possible for the former to whip its tail tip at the eyes and possibly blind it by knocking them out?.........

2.) Sauropods also tended to have the pollex claws that some think that they could use as defensive weapons. Again, could these possibly be threats to even same sized animals (using the claws to create puncture wounds potentially causing blood loss comes to mind)?

I'm sorry if what I'm asking is completely outlandish, but I just had to get these curiosities out of my head.

[theropod]

1) Sure it is possible to knock out an eye with a whiptail (although knocking out both at once, in a carnosaur, seems well-nigh impossible).
That’s the sort of reason that makes any act of predation on a decent-sized animal risky, even if it is not a particularly formidable prey item. If I’m not mistaken orcas and great whites also employ cautious tactics when hunting seals for similar reasons. Eyes are fairly vulnerable parts independently of body size and overall durability, so it makes sense.

But I think a case could be made that in order to actually hit a theropod in the eye, thereby blinding it, a sauropod would have to get pretty lucky. It’s a small target to hit with the tip of a whip for a human, and I assume a sauropod using what is essentially functioning like a whip would, if anything, have a more difficult time than a human on account of coordination, visual acuity and cognitive capabilities. So I doubt it would stand there, aim carefully and reliably hit the eye of a theropod. Plus, even an attacking theropod faced with a comparatively small sauropod would be unlikely to just charge blindly into its defence, even if (or because) most hits would just be a painful nuisance. Modern predators don’t do that even with prey that poses a relatively minor threat to them.

[Infinity Blade]

Good points.

What of the second thing I mentioned? If a sauropod rears up and defends itself with its manual claws, couldn't it be about as dangerous as say, a ground sloth (which I think may be analogy to this action)?

[theropod]

I highly doubt you can in any way compare their forelimb anatomy. Sauropods have a claw on their forelimbs. And that’s really all the similarity there is. The claw differs massively in positioning and the rest of the forelimb is about as different as an elephant’s is from a bear’s. Most likely limbs that specialized for graviportal locomotion lack the lateral flexibility to perform the swinging motion that a ground sloth would rely on, and having permanently pronated, collumnar hands won’t help either.

The claws (in those sauropods that actually have them, especially diplodocids) might help in defense, but I don’t think they are anywhere close to ground sloth’s in terms of effectiveness.
The way they are positioned they tend to face downward and inwards, so stabbing or raking downwards seem like the most likely motions they could perform.

[Infinity Blade]

Time for yet another dreadful question from Ausar, this time regarding hadrosaurs (and possibly mega ornithopods in general).

I know we discussed hindlimb kicking as a possible defensive method. I got the impression that we were referring to backward kicks (like those in equids), but I'm kind of questioning that now. Apparently, theropod femora could not move to the point where the angle between the femur and the tail base was lower than 90 degrees (90 degree rule). This means that they could not move their femora very far backwards. Did the same thing apply to ornithopods?

[theropod]

Nov 12, 2016 20:07:04 GMT 5 Infinity Blade said:

Time for yet another dreadful question from Ausar, this time regarding hadrosaurs (and possibly mega ornithopods in general).

I know we discussed hindlimb kicking as a possible defensive method. I got the impression that we were referring to backward kicks (like those in equids), but I'm kind of questioning that now. Apparently, theropod femora could not move to the point where the angle between the femur and the tail base was lower than 90 degrees (90 degree rule). This means that they could not move their femora very far backwards. Did the same thing apply to ornithopods?

I may be missing something, but where specifically did you read that the hip could not be extended further than to a 90° angle in theropods?

I just checked Hutchinson et al. 2005 on the matter:

Furthermore,Charig (1972) and others since that classicstudy have assumed that the range of motionof the femur was restricted to the arc betweenthe pubis and ischium, or at least that the fe-mur could not be retracted past a line parallelto the ischium (e.g., Paul 1988). As some muscle origins lie outside this arc (e.g., M. iliotibialis 1 cranially; M. caudofemoralis longus caudally; Fig. 3), we find such assumptions questionable, especially as the lengths of those muscle fibers are uncertain (Hutchinson 2004b) and so it cannot presently be tested whether further motion was impossible.

Hutchinson, John R., Frank C. Anderson, Silvia S. Blemker, and Scott L. Delp. 2005. Analysis of Hindlimb Muscle Moment Arms in Tyrannosaurus rex Using a Three-Dimensional Musculoskeletal Computer Model: Implications for Stance, Gait, and Speed. Paleobiology 31: 676–701.

This seems to suggest that there’s no evidence for the range of motion being anywhere near that restricted, indeed it argues against a vastly less tight restriction. In their simulations they assumed a range of flexion and extension between 45° forwards and 65° backwards, and their full-extension model does actually seem to have the femur roughly parallel with the ischium, so that could realistically make the angle with the tail base as low as 25°.

Obviously ornithopods have different pelves and either way it’s hazardous to apply what we think we know about theropods to animals with such different anatomy, but likewise I see no reason why ornithopod femora would be so restricted in their backwards movement. It sure wouldn’t be useful for locomotion not to be able to extend the hip joint, especially with so much muscle mass in the tail base positioned so it has a long moment arm specifically at high angles of extension.

[Infinity Blade]

I read it here (clickable). It's a tutorial on how to illustrate theropod legs and it even cited a gif Scott Hartman made with a moving theropod leg, the femur never posteriorly moving past perpendicular to the ground. If there's no evidence that this was actually the case however, then that's that.

[theropod]

Well, perhaps the femur didn’t rotate past the vertical in some types of walk, that doesn’t mean it couldn’t. And unless he wrote that somewhere else, Hartman didn’t claim that either.

There’s no evidence that anything in the joint or musculature would prevent the femur from being pulled back further from what I can tell, and nowhere does this seem to be assumed in the scientific literature (both Hutchinson et al. 2005 and Stevens et al. 2008 depict the femur of T. rex being extended at least parallel to the ischium). Indeed in T. rex the M. caudofemoralis longus only really comes into its own in terms of leverage when the femur is extended well past the vertical according to Hutchinson et al.’s modelling of the moment arms.

I’m getting the feeling that the author got a little too absorbed with extrapolating everything from that chicken leg and in the process missed the important differences between bird legs and those of most non-avian theropods. Birds have no functional tail or caudofemoral muscles, no wonder they don’t rely on hip-extension, and their femora are often permanently flexed because they have to point forward to bring the feet under the COM. In result, birds use mostly knee-driven locomotion with much less involvement of the hip compared to non-avian theropods where extension of the femur obviously played a major role.

[Infinity Blade]

I had a look at an annotated bibliography of dinosaur paleopathology (link). Late Cretaceous hadrosaurs displayed broken ribs, and it's speculated that these were results of aggressive intraspecific behavior in the form of hind foot kicks...

[Infinity Blade]

Lateral hindleg raising as a defense mechanism in brachiosaurids and camarasaurids (clickable).

And for whatever it's worth, tails like telegraph poles and giraffe-like necking as a means of defense as supported by this book (link).

Edit 12/23/19: Actually, now that I think about it, plain tails of "vanilla" sauropods (consider Rhoetosaurus as an example) and hadrosaurs are not bad weapons at all. With a long, supple, yet muscular and overall massive tail, a swing from that thing could be really serious if swung at specific parts of the body (e.g. the head). The tail wouldn't even need to be as massive as the head of whatever animal it was in a confrontation with (just an example: a quick Google suggests that a heavy baseball bat could weigh 3.4 pounds, while the average human head apparently weighs 10-11 pounds; I trust I don't need to explain that a baseball bat blow to the head would obviously still be very damaging), but depending on how massive the tail in question is, it just might be.

Edit 1/22/20: Something Gregory S. Paul said on the DML regarding sauropod caudal defense before I was even born.

The probability that all sauropods used their tails for defense is high. Sauropods were often hunted by predators as big as rhinos and elephants. They were therefore in much greater danger of attack than are elephants. Female african rhinos tend to have longer, more forward directed nose horns than males. It is probable that they use these horns to defend their calves, which are nearly defenseless against lions and hyaenas (see R. Owen-Smith's 1988 classic Megaherbivores). The notion that big ungulates hardly ever use their horns for anti-predator defense is something of a myth, have seen many videos of them doing so.

The situation faced by sauropods was akin to that faced by similar sized whales, which come under attack from elephant sized orcas (a few million years ago, it was even more enormous sharks), as well as pygmy killer whales. Orcas have been filmed attacking solitary blue whales, just this year a pod of sperm whales. In the latter case the whales tried to use their tails for defense. Sperm whale pods have also been filmed under attack from pygmy killer whales. The latter are much to small to kill the giants. They just take big bites for their afternoon meal! In the Morrison, the 1-1.5 tonne common Allosaurus may have been attacking adult sauropods not to kill them, but to dine on their living flesh. Way cool if true. Young were subject to death. The much bigger, rarer Saurophagus (cool name) were probably out to kill adults. Large Yangchuanosaurus could probably kill Mamenchisaurus, elephant sized Giganotosaurus could probably kill fin whale sized Argentinosaurus.

A basic method of tail defense used by all sauropods was probably simply to use the fleshy midsection of the tail as a swinging beam to knock the bipedal predators off their feet. For example, the tails of Morrison diplodocids weighed about a tonne and a half (according both to my models, and to Myrvhold & Currie's calculations), about the same as the common allosaurs. The tail of Argentinosaurus probably weighed as much as Giganotosaurus. The effect of being walloped by a few tonnes of tail is obvious. Much more serious than the impact form a whale fluck, because of the associated effects of a fall in 1 G.

Another mode of caudal defense, the tail clubs found on some of the Chinese sauropods.

The question is whether supersonic whip tails were used for defense. Certainly they would be effective as a pain inducing deterrent. Force increases by velocity squared, so the impact of a supersonic whip an inch or more wide would leave a long, nasty, bleeding cut. Theropods could come to associate the sound of tail cracking with pain, and might be deterred from attacking by the sonic cracks produced by the members of a threatened sauropod/herd. The one problem with this scenario is one that Nathan has pointed to. It is not clear that sauropod whip tails could withstand such high levels of stress, nor are the the expected signs of damage present. Therefore, the whips are the least likely part of sauropod tails to be used for defense. However, even if the whips were not used for physical defense, tail cracking may have acted as a sonic clue to warn theropods that their targets were armed with very long, massive tails that could sweep them off their feet if the predators dared come too close.

GSPaul

dml.cmnh.org/1997Dec/msg00196.html

[Infinity Blade]

Oct 22, 2019 19:07:41 GMT 5 theropod said:

Oct 22, 2019 16:49:02 GMT 5 Infinity Blade said:

Okay then. How massive was the tail of:

• Brachiosaurus (or Giraffatitan if that suits people better; representative of our brachiosaurids)?
• Diplodocus (representative of our diplodocids)?
• Argentinosaurus?

I want to know the mass of the tail relative to total body mass as well. I tried to more or less convey the variation in proportional tail size here. If there are any other sauropods with relatively larger (or smaller) tails than any of these, mention them as well.

Sauropod body masses
I can look into that further and expand this post when I find the time. Off the top of my head, Argentinosaurus is probably too fragmentary to get a reliable estimate from (certainly one reliably different from related taxa), so it may be better to use a more complete large titanosaur like Futalognkosaurus or Dreadnoughtus.

You can find volumetric figures for Dreadnoughtus, Apatosaurus and Giraffatitan in Bates et al. 2015, [m&m] based on minimum convex hulling and testing various assumptions (such as +21%, and testing the original estimates based on limb-bone regressions).

[Results] minimum models:

Dreadnoughtus schrani (MPM-PV 1156) total volume 26.91 m³ SG 1000 kgm⁻³ mass 25 947.68 kg total (with respiratory structures) SG 821.9 kg/m³ mass 22,117.98 kg hindlimb volume 0.796m³ SG 1000 kgm⁻³ mass 795.80 kg forelimb volume 0.614 m³ SG 1000 kgm⁻³ mass 615.09 kg axial total volume 25.50 m³ SG 1000 kgm⁻³ mass 24,536.80 kg neck volume 3.110 (-0.49 m³) SG 1000kgm⁻³ mass 3109.99 kg (-486.48 kg) trunk volume 20.382 (-4.3 m³) SG 1000 kgm⁻³ mass 20,381.96 kg (-4303.67 kg) tail volume 1.011 SG 1000 kgm⁻³ mass 1011.35 kg

Apatosaurus louisae (CM 3018) total volume 26.63 m³ SG 1000 kgm⁻³ mass 26,699.01 kg total (with respiratory structures) SG 818.8 kg/m³ mass 21 803.21 kg hindlimb volume 1.289 m³ SG 1000 kgm⁻³ mass 1288.92 kg forelimb volume 0.722 m³ SG 1000 kgm⁻³ mass 722.62 kg axial total volume 24.62 m³ SG 1000 kgm⁻³ mass 24 687.47 kg neck volume 2.62 (-0.29 m³) SG 1000kgm⁻³ mass 2615.16 kg (-291.95 kg) trunk volume 20.12 (-4.6 m³) SG 1000 kgm⁻³ mass 20,187.65 kg (-4602.86kg) tail volume 1.86 SG 1000 kgm⁻³ mass 1861.20 kg

Giraffatitan brancai (HM SII) total volume 25.28 m³ SG 1000 kgm⁻³ mass 25,282.88 kg total (with respiratory structures) SG 788.8 kg/m³ mass 19 946.35 kg hindlimb volume 1.046 m³ SG 1000 kgm⁻³ mass 1045.88 kg forelimb volume 0.614 m³ SG 1000 kgm⁻³ mass 615.09 kg axial total volume 25.50 m³ SG 1000 kgm⁻³ mass 24,536.80 kg neck volume 2.46 (-0.33 m³) SG 1000kgm⁻³ mass 2461.00 kg (-332.54 kg) trunk volume 19.85 (-5.00 m³) SG 1000 kgm⁻³ mass 19 850.92 kg (-5000.39 kg) tail volume 0.78 SG 1000 kgm⁻³ mass 774.76 kg

[Discussion] The paper seems to suggest that the +21% models are likely more accurately reflecting real-life body masses, so perhaps the total body masses should be increased by that factor, but that doesn’t really affect the proportions.

This means the tail in Dreadnoughtus is about 4.6% of total body mass, in Apatosaurus it is about 8.5%, in Giraffatitan about 3.9%. The tail of Brachiosaurus altithorax would probably be somewhat larger (and so would total body mass) based on Taylor 2009’s redescription.

Reference:

Bates, K.T., Falkingham, P.L., Macaulay, S., Brassey, C. and Maidment, S.C. 2015. Downsizing a giant: re-evaluating Dreadnoughtus body mass. Biology letters 11 (6): 20150215.

Taylor, M.P. 2009. A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914). Journal of vertebrate Paleontology 29 (3): 787–806.

With these comparative masses, how severe would a tail slap be in intraspecific conflict between two giant sauropods of the species mentioned here? I remember the ankylosaur tail force paper by Victoria Arbour said that a tail blow could be made even more forceful through movements of the hips and hindlimbs, so that may need to be considered as well (although, I seriously doubt anyone's ever quantified how much more force this would add).