Defenses of dinosaurs without obvious weapons

[theropod]

That depends a lot on how quickly they could swing them, and what part of their opponent they hit.

Obviously a powerful blow to the head or neck might be quite dangerous.

[Infinity Blade]

I found this:

The impulses transferred by the moving neck and forelimb of a sauropod of a sauropod have the same order of magnitude as the impulse transferred by the entire body of a theropod (with a mass of less than 10 metric tons) as a potential predator. It is easy to understand than an attacker struck by a limb or a neck of sauropod dimensions runs a considerable risk!

Preuschoft et al. (2011) in Biology of the Sauropod Dinosaurs: Understanding the Life of Giants.

This seems to be talking about the neck of Brachiosaurus, but they also mention using "the Berlin Brachiosaurus" as their test subject. As I understand it, the Berlin "Brachiosaurus" is actually Giraffatitan, and is the specimen HM SII, the same one mentioned in theropod's GDI above. Given the size of Giraffatitan and the impulse of this magnitude (the same as that of the whole body of a <10t theropod!) generated by its moving neck or forelimb, I feel like a blow from either could be serious even to a same-sized animal.

[Infinity Blade]

How realistic is it that the tail whip of diplodocids was actually a damaging weapon? There's the whole supersonic tail whip proposal, but, at least from what I can tell, criticism of this idea has come in the form of whether or not the soft tissues of the tail could withstand being whipped around at those speeds on a regular basis without rupturing and tearing.

I feel like that as long as the distal end of the tail could be whipped at very high speeds (even if nowhere near supersonic speeds) it might actually create soft tissue damage on the intended target, especially considering the fact that there were dermal spines along the dorsal surface of the tail whip (at least some of which were large, laterally compressed, and sharp structures (Czerkas, 1992, Czerkas, 1994)). Although, Czerkas himself seems doubtful that the dermal spines would have had much defensive capabilities.

Edit: apparently, the dermal spines of the green iguana actually play a defensive role as well, according to one of Wikipedia's sources (Samuelson, Phillip (1995-06-01), "The Lizard King", Reptiles Magazine). I'm more confident that they would have played a defensive role in diplodocids too. Not really sure why Czerkas doubted their defensive capabilities.

[dinosauria101]

I think that's fairly feasible, ESPECIALLY if they had keratin spikes. Might be even stegosaur-like.

Brontosmash apatosaurines deserve a mention. They have what are essentially massive spiky clubs.

[roninwolf1981]

Seems like the whole idea of sauropods using the thumb claw as a weapon is almost debunked. I can accept that the thumb claw would be mostly used for traction during ambulation. If the claw isn't put to use, then perhaps it's the sheer mass of the sauropod that can be weaponized.

I recall the Dinosaur Revolution episode "The Watering Hole" where a Dinheirosaurus reared up and pinned down the Torvosaurus with its front legs, ultimately neutralizing it. It wasn't the thumb claw, but rather the combined mass and inertial force pressing down on the Torvosaurus that ended up killing it.

I would imagine that Shantungosaurus used a similar rearing stomp to discourage and/or outright eliminate predatory threats. I don't know if Edmontosaurus was truly smaller than Shantungosaurus, or if they were of equal size based on the larger estimates; I always felt that Edmontosaurus was easy pickings for a full adult T-rex, unless it could grow big enough to push around a Rex.

[Infinity Blade]

Seems like the whole idea of sauropods using the thumb claw as a weapon is almost debunked.

Not really, credible sauropod experts still seem to think the thumb claw of sauropods could have been used for defensive purposes. Most recently to my knowledge, such sentiments are expressed in the 2016 book The Sauropod Dinosaurs: Life in the Age of Giants->. This book even seems to suggest that the claw was often cocked upward and kept well off the ground. That would be great for keeping the claw sharp, but would kind of defeat the purpose of traction (not to say they never used the claw for traction if need be).

Edit: the claw being kept off the ground is corroborated here.

Function of the manual ungual is influenced by its orientation. Due to its slightly oblique metacarpo-phalangeal joint, phm I-1 points mediodistally and therefore away from the other digits. The fact that its lateral side is longer than its medial one (mostly because the lateral distal condyle is more pronounced than the medial one) and that also the proximal articular face of the claw is oblique results in an ungual that points posteriorly and nearly touches the ground with the distal end of its lateral side (Figure 6; see also Wright, 2005). Trackways showing manual claw imprints (e.g., Bilbey et al., 2005; Pascual Arribas et al., 2008) are consistent with the herein proposed articulation of the ungual (Figus figure 35re 35). The hypothesis of Thulborn (1989, 1990) that the claw is usually held in dorsolateral hyperextension is therefore rejected for Camarasaurus, also because both the distal articular surface of mc I and the one of phm I-1 curve further proximally on its palmar side than anteriorly, implying that the mobility was less restricted posteriorly than towards the front (see Farlow et al., 1989 for other objections). Anteroposterior movements of the pollex also appear to have been less constricted than the ones in the other fingers (Upchurch, 1994; Bonnan, 2003; Upchurch et al., 2004a), but the orientation of the joints in digit I indicates that motion mainly occurred in a more transversal plane, because of the oblique distal faces of the precedent elements (Upchurch, 1994). This leads to the conclusion that the pollex - although it was probably not separate as a whole (Paul, 1987) - was not as tightly incorporated into connective tissue as the other digits were. The absence of claw marks in some tracks might thus indicate that the ungual was habitually flexed posterolaterally during walking.

palaeo-electronica.org/content/2015/1284-manus-and-pes-of-camarasaurus

[Infinity Blade]

I recently wrote a rather long and detailed answer summarizing sauropod antipredator defense on Quora (last one down). Tell me what you all think of it.

www.quora.com/How-did-sauropod-dinosaurs-defend-themselves-from-predators

[talira]

Sauropods like Barosaurus, Diplodocus and Mamenchisaurus had incredibly long tails. The end of the tail was thin and could possibly have been used like a giant whip to cripple predators who got too close. Personally, I also believe they could have used their long necks as weapons in a behaviour known as "necking".

[6f5e4d]

Powerful defenses for sure. The sauropods could technically use it against any theropod dinosaur, not just the tyrannosaurs.

[creature386]

Apr 9, 2020 2:39:24 GMT 5 Infinity Blade said:

I recently wrote a rather long and detailed answer summarizing sauropod antipredator defense on Quora (last one down). Tell me what you all think of it.

www.quora.com/How-did-sauropod-dinosaurs-defend-themselves-from-predators

That's some great stuff, gave you an upvote there.

The only possible downside is that it is a bit AVA focused. Like, it's very focused on anatomical adaptations like the tail or the neck (with lots of cool details, BTW, like the one on Amargasaurus) with less more ecological defenses, such as fast growth or Living in herds. Then again, I have no idea what the questioner intended to hear. What I can tell is that your essay answers our thread's question very neatly.

[Infinity Blade]

Apr 9, 2020 17:42:11 GMT 5 creature386 said:

Apr 9, 2020 2:39:24 GMT 5 Infinity Blade said:

I recently wrote a rather long and detailed answer summarizing sauropod antipredator defense on Quora (last one down). Tell me what you all think of it.

www.quora.com/How-did-sauropod-dinosaurs-defend-themselves-from-predators

That's some great stuff, gave you an upvote there.

The only possible downside is that it is a bit AVA focused. Like, it's very focused on anatomical adaptations like the tail or the neck (with lots of cool details, BTW, like the one on Amargasaurus) with less more ecological defenses, such as fast growth or Living in herds. Then again, I have no idea what the questioner intended to hear. What I can tell is that your essay answers our thread's question very neatly.

That is true. At the time I felt like I just wanted to get those actual physical defenses out of the way first, since I assume the reason why this question was asked in the first place was an underlying assumption that sauropods were physically defenseless (other than in size). Should I edit my answer with those ecological defenses? I would need some data on sauropod growth rates compared to those of their predators for a solid explanation of growth rate, though (assuming that data exists to begin with).

[roninwolf1981]

Dec 21, 2019 9:30:17 GMT 5 Infinity Blade said:

Seems like the whole idea of sauropods using the thumb claw as a weapon is almost debunked.

Not really, credible sauropod experts still seem to think the thumb claw of sauropods could have been used for defensive purposes. Most recently to my knowledge, such sentiments are expressed in the 2016 book The Sauropod Dinosaurs: Life in the Age of Giants->. This book even seems to suggest that the claw was often cocked upward and kept well off the ground. That would be great for keeping the claw sharp, but would kind of defeat the purpose of traction (not to say they never used the claw for traction if need be).

Edit: the claw being kept off the ground is corroborated here.

Function of the manual ungual is influenced by its orientation. Due to its slightly oblique metacarpo-phalangeal joint, phm I-1 points mediodistally and therefore away from the other digits. The fact that its lateral side is longer than its medial one (mostly because the lateral distal condyle is more pronounced than the medial one) and that also the proximal articular face of the claw is oblique results in an ungual that points posteriorly and nearly touches the ground with the distal end of its lateral side (Figure 6; see also Wright, 2005). Trackways showing manual claw imprints (e.g., Bilbey et al., 2005; Pascual Arribas et al., 2008) are consistent with the herein proposed articulation of the ungual (Figus figure 35re 35). The hypothesis of Thulborn (1989, 1990) that the claw is usually held in dorsolateral hyperextension is therefore rejected for Camarasaurus, also because both the distal articular surface of mc I and the one of phm I-1 curve further proximally on its palmar side than anteriorly, implying that the mobility was less restricted posteriorly than towards the front (see Farlow et al., 1989 for other objections). Anteroposterior movements of the pollex also appear to have been less constricted than the ones in the other fingers (Upchurch, 1994; Bonnan, 2003; Upchurch et al., 2004a), but the orientation of the joints in digit I indicates that motion mainly occurred in a more transversal plane, because of the oblique distal faces of the precedent elements (Upchurch, 1994). This leads to the conclusion that the pollex - although it was probably not separate as a whole (Paul, 1987) - was not as tightly incorporated into connective tissue as the other digits were. The absence of claw marks in some tracks might thus indicate that the ungual was habitually flexed posterolaterally during walking.

palaeo-electronica.org/content/2015/1284-manus-and-pes-of-camarasaurus

I stand corrected.

Apr 9, 2020 7:35:10 GMT 5 talira said:

Sauropods like Barosaurus, Diplodocus and Mamenchisaurus had incredibly long tails. The end of the tail was thin and could possibly have been used like a giant whip to cripple predators who got too close. Personally, I also believe they could have used their long necks as weapons in a behaviour known as "necking".

That's one powerful clothesline, lol.

[Infinity Blade]

A note on titanosaur bulb and root osteoderms. The ornamentation of the bulb portion of these osteoderms does indeed suggest the presence of a keratin sheath, which could be used for defensive purposes (Vidal et al., 2017).

As in extant crocodiles, titanosaur osteoderms could have had several functions: (i) the ornamentation in the bulb of these osteoderms suggests the presence of a keratin sheath, which might imply display or defensive function of some sort; (ii) the well developed keels in the basal surface suggest the insertion of tendons and/or ligaments (there is an ossified tendon/ligament in the basal surface of HUE-00950; Fig. 3e), and some osteoderms being at least twice the length of a vertebra, imply a stiffening of the backbone. A similar function has been proposed for the armor of crocodiles and Thyreophora; (iii) dermal ossicles, at present only found associated with Saltasaurus loricatus, might have given reinforcement to the integument15; (iv) a thermoregulatory function in titanosaur osteoderms has been considered, but ruled out due their low surface area/volume ratios; and (v) the internal branching canals, the large trabeculae, the presence of Harvesian canals seen in histological sections and the hollow spaces associated with the branching canals (Figs 1c, 3 and 4) imply they could be a potential source of labile minerals.

This applies most strongly to osteoderms with prominent conical bulbs (Fronimos, 2021).

Vidal et al. (2017) [same authors as above] linked the bulb morphology of some titanosaur osteoderms to a possible display or defensive function, but this applies most strongly to those osteoderms with prominent conical bulbs (i.e., Ampelosaurus, Le Loeuff et al., 1994; Magyarosaurus, Csiki, 1999) and not to TMM 45888-1.

Brackets mine.


A recently described titanosaur osteoderm from Big Bend National Park, Texas, may have been capable of localized defense, though not whole body defense (Fronimos, 2021).

Although titanosaur osteoderms were first described by Depéret (1896), references to them as armor began with the description of Saltasaurus by Bonaparte and Powell (1980). Other authors (e.g., Dodson et al., 1998; D'Emic et al., 2009; Curry Rogers et al., 2011) rejected this hypothesis based on the relative scarcity of titanosaur osteoderms in the fossil record, taking this as evidence that they were not numerous enough on the body to form an extensive protective covering. Titanosaur osteoderms also do not fit together tightly, with the exception of the small dermal ossicles of Saltasaurus (Bonaparte and Powell, 1980), unlike those of many armored archosaurs and xenarthrans (Sanz and Buscalioni, 1987; Curry Rogers et al., 2011). Cerda et al. (2015) favored a defensive function for keeled osteoderms based on a fibrous texture that may have connected to the supraspinal ligament. TMM 45888-1 does not bear any articulations, so it was not part of an interconnected shield of osteoderms, nor does it bear a keel or fibrous texture. It is the only titanosaur osteoderm reported from the Javelina Formation of Texas, a unit otherwise rich in titanosaur remains (see summary in Lehman et al., 2018), consistent with a low number of osteoderms on the body of the animal, though a taphonomic bias cannot be ruled out (D'Emic et al., 2009). Thus, there is no direct evidence to support the hypothesis that TMM 45888-1 was part of a protective paravertebral shield.

A more localized defensive function remains possible if, as discussed by Cerda et al. (2015), osteoderms were restricted to specific regions of the body. In contrast to the apparent fragility of hollow osteoderms (Curry Rogers et al., 2011; Vidal et al., 2017), osteoderms with a spongy interior reduce the likelihood of catastrophic fractures under stress relative to exclusively compact bone (e.g., Alligator, Sun and Chen, 2013; glyptodonts, du Plessis et al., 2018). Putative bite marks on a titanosaur osteoderm from Brazil (MPMA 08-0058-11; Marinho and Iori, 2011) may provide direct evidence that titanosaur osteoderms could also withstand punctures without fracturing. Although large neurovascular channels occur in TMM 45888-1, these did not necessarily compromise the strength of the element. Experiments by Broeckhoven et al. (2017) on lizard osteoderms demonstrated a tradeoff between vascularity and puncture resistance, but the extent of vasculature in TMM 45888-1 most closely resembles the more resistant lizard osteoderms (Broeckhoven et al., 2017: fig. 2). Thus, the Texas specimen and other titanosaur osteoderms with a similar interior structure, such as those described by Cerda et al. (2015), may have been materially capable of defense, even if this was highly localized.