palaeofail-explained:

palaeofail-explained:

None! All known quadrupedal dinosaurs were obligatory or facultative herbivores.

Spinosaurids have, at various times, been suggested to have been quadrupedal; I don’t find this likely, however, as their hands don’t show any weight-bearing adaptations and I can see no reason why they would need to be.

The ankylosaur Liaoningosaurus has been suggested to have been piscivorous due to apparent preserved fish in the gut and supposed aquatic adaptations. I have my doubt about this; I don’t see why the fish bones in the body couldn’t have been from either scavenging fish or that they were simply washed in. Some of the supposed swimming adaptions have either been shown to be inaccurate (the “belly armour” was probably preserved skin) or may not be piscivorous adaptions (lack of fusion, odd proportions may be due to juvenile specimens).

#this is so whack#i wonder why that is

The ancestor of all dinosaurs was a biped. So, why did quadrupedal dinosaur evolve quadrupedality?

For sauropods, the answer is guts. Plants are way harder to digest and are less nutritious than meat, so herbivores need to be able to have massive guts in order to hold large amounts of plants and break them down over long periods of time. (This may also be the case in silesaurids, a group closely related to dinosaurs)

Ornithischians got around this by changing their hip configuration so that their guts could go back further, and indeed many ornithischians were bipedal. So why did some become quadrupedal? In thyreophorans, they evolved heavy bony armour, likely to prevent predation from theropods. In ceratopsians, their heads became very large, in part due to increased space for anchoring jaw muscles (for chewing plants) and and defence against predators. Ornithopods always retained some bipedal capabilities, and only started walking quadrupedally when they got really big, and the weight of their guts couldn’t all be compensated for by moving it backwards.

If we look at it this way, it seems that dinosaurs only evolved quadrupedality when they had to due to the effects of being an herbivore.

This is probably due in large part to the evolutionary history of dinosaur ancestors. The earliest tetrapods were superficially lizardlike animals; they walked with a sprawled posture.

(A typical sprawled-stance tetrapod. Image by Deror Avi)

This is a very energetically efficient posture, as the animal doesn’t have to waste energy holding itself up. There is a big downside though – animals with this posture waggle their bodies back and forth when they run, meaning that their lungs collapse and they can’t breathe while running. The ancestors of dinosaurs solved this problem by adopting an erect stance, which allowed them to breathe while they ran.

(Coelophysis, an early dinosaur. Image in public domain)

The transition from sprawled posture to erect (yes, yes, you’re very mature), however, had the side effect of effectively locking the hands in a position where the palms face each other. This was really always the case – in sprawled-stance animals, the palms are in this position as well. The arms were just swung out to the side so that the palms were flat down.

Humans have the luxury of being able to rotate our forearm bones past each other, so we tend to assume this is the case for everything. It’s not. We can only rotate our wrists because of a special cylindrical joint between the two bones in our forearm that lets one turn while the other stays still. Dinosaurs didn’t have this.

(Human radius/ulna from Pearson (source); Deinocheirus by Ryan DeLuca on Flickr)

In dinosaur lineages that took to all fours, they couldn’t simply turn their wrists and go; they were locked in position. Some groups (namely sauropods and thyreophorans) evolved twisted forearms that were locked with palms facing backwards (or “down”); others (namely ceratopsians and ornithopods) kept the palms facing inwards and just walked with their hands turned like that. (We don’t really know much about the hands of silesaurids, but i suspect they did something similar to this as well)

(Iguanodon, an ornithopod. By Scott Hartman @skeletaldrawing (source))

So, why didn’t theropods ever evolve quadrupedality? Because of their evolutionary history, dinosaurs were kind of up a blind alley when it came to re-evolving quadrupedality. The lineages that did take to four legs likely did so as side-effects of their herbivory, and there wasn’t really any factor that was strong enough to push (known) theropods into quadrupedality.

gallusrostromegalus:

excessively-english-little-b:

penfairy:

penfairy:

I visited the museum and I heard two bros in the dinosaur exhibit having an earnest discussion about the best way to kill a T-Rex with a sword and what kind of armour should be worn into the battle and they spoke with such passion I really wish the scientific community could have heard them. I’d love to know how palaeontologists would weigh in on The Great Debate.

For instance, was the bro in the weed shorts right? Is it pointless to wear heavy armour when battling a T-Rex? Is it truly better to go into battle naked wielding dual swords? Or was the bro in the backwards cap correct? Should you go for a double-handed sword and iron armour? Will light bouncing off the armour really confuse and blind the beast? Realistically, what protection is armour against a dinosaur? Was Weed Shorts right when he proposed to use his superior agility to slash its tendons and stab the eyes when he brought it down? Or was Backwards Cap right when he said charge and slash open its soft belly?? What is the truth??!??

Hello, palaeontologist-in-training here! Thought I’d have a little think into this because hey, who wants to do coursework on trilobites when you could be considering T. rex instead?

• Light and maneuverable is probably best when facing a rex. It’s big and it’s powerful but it’s not going to making any quick sharp turns any time soon.
• According to our current estimates, a T. rex would be able to crush a small car with its jaws, so realistically, no amount of armour is gonna protect you if it grabs you.
• If the T. rex manages to grab you you’re dead regardless. It could probably eat you within a couple of bites if it was trying.

Figures 1 & 2: Theoretical T. rex bite-force model fucking up a mini. Thank you, Bill Oddie and BBC’s The Truth About Killer Dinosaurs.

As far as armour goes, lighter is better, and at the end of the day isn’t going to mean shit anyway. T. rex can’t slash at you with claws, so it’s bite or bust, and if it bites YOU’RE bust. So, lets say a point to Weed Shorts. Why NOT fight a T. rex butt naked with swords.

• T. rex had good binocular vision. Don’t believe Jurassic Park’s lies –T. rex was a hunter and could probably see you brilliantly whether you moved or not.
• That said, a T. rex’s eyesight will work about the same as modern birds of prey. Think hawk, or eagle. I reckon light bouncing off anything would be a fairly minor hindrance, or at least, wouldn’t affect it any more than any other hunting bird.

So, using light to blind and confuse the rex? May potentially work but might be hard and wouldn’t do much for long. Don’t rely on this for strategy.

• T. rex actually had gastralia, sometimes called ‘belly-ribs’. These protected and supported the internal organs.There would also be some seriously thick abdominal muscles to get through.
• Unless you’re planning to do some precision stabbing with a very long sword, chances are you’re not gonna be killing a rex by slicing open it’s stomach. Also, being under its stomach is gonna put you in-reach of the Jaws Of Death.
• I’m not sure how easy it would be, or how well it would work, to try and cut a T. rex’s tendons. Theoretically, sounds like it should work. However, you’re gonna need a lot of strength to get through them, probably.
• I’d personally cut the throat rather than stab through the eyes once the rex is down, but that’s probably personal preference. Once you’ve felled it, it’s dead either way! A T. rex unable to hunt is a dead T. rex.

Figure 3: The gastralia of a T. rex. Bless u Scott Hartman for your skeletal references.

As far as attack goes, the belly is not as weak a spot as it seems. So, point to Weed Shorts on his execution plan. Sounds pretty solid.

Overall, I’d say that Weed Shorts had the best plan to defeat the mighty Tyrannosaurus rex. If you ever see him again, congratulate him on his solid plan of attack.

My favorite thing about paleontologists (and any scientist really, but paleontologists in particular) is that you can ask them COMPLETELY BATSHIT INSANE questions and by God, they will give you a completely Serious answer.

Also @assassinahsoka this reminds me of your guy who wanted to eat a t rex.

lavenderek:

darkequidae:

cluckyeschickens:

chickenkeeping:

without question

Without remorse.

Without hesitation

without a napkin

I think someone wrote a book with that plot called Jurassic Park.