Purussaurus mirandai vs. Euoplocephalus tutus

[dinosauria101]

Purussaurus mirandai 

upload.wikimedia.org/wikipedia/commons/7/76/Purussaurus_BW.jpg

Order: Crocodyliformes
Family: Alligatoridae
Length: 8 meters
Mass: 2.6 tonnes
Diet: Large herbivores
Age and Location: Miocene epoch, 13.8 to 11.8 million years ago, Colombia
Killing apparatus: Crushing jaws
Was one of the largest species of crocodilian. Had a very strong bite proportionately.

Euoplocephalus tutus

wonjae.files.wordpress.com/2010/02/euoplocephalus.jpg

Order: Thyreophora
Family: Ankylosauridae
Length: 6 meters
Mass: 2.5 tonnes
Diet: Plants
Age and Location: Late Cretaceous period, 75 million years ago, Canada and the United States
Killing apparatus: Tail club
One of the largest and best known ankylosaurs. Covered in heavy armor for protection.

[6f5e4d]

Purussaurus only barely is heavier than Euoplocephalus, and that club is going to devastate the caiman, so Euoplocephalus wins the battle.

[dinosauria101]

I'd favor Euoplocephalus as well - a decent reach advantage and the club would be devastating. 1 good hit can probably crack Puru's head open

[Ceratodromeus]

I thought this would be relevant
 On Paul's estimate of ~2.5t that the OP derives the figure from:
"Paul (2010) estimated a mass of 2.5 tonne for a 5.5
metre long unidentified Euoplocephalus specimen,
and a few years later Paul (2016a) also estimated a
mass of 2 tonne for a 5.3 metre long unidentified
specimen. In his mass table Paul (2016b) identified
the Euoplocephalus tutus AMNH 5404 specimen with
a calculated mass of 1.95 tonne and a length of 5.47
metres. It should be noted that the Euoplocephalus tutus AMNH 5404 specimen appears to be relatively
less massive that the unidentified specimens. In general, the reconstructions show a light and agile looking animal. Paul was a student of Bakker, so perhaps
it is not surprising that his restorations show a fast
and agile Euoplocephalus."

"In general it would appear that many early estimates
of Euoplocephalus reconstructed it as a fast and agile
animal with a low mass in the 2.5 tonne range. But
why would such a fast and agile animal have devoted
so many resources to producing external armour?
Some of the more up-to-date reconstructions show
an animal that was a lot bulkier and sturdier. This
would certainly seem to correlate well with an animal
that had an impressive array of external amour.
Accordingly, a mass of 3.4 tonne was chosen as the
best estimate."^{1}



And on P.mirandai size^{2}



References
^{1}Hurrell, Stephen W. "A Palaeogravity calculation based on weight and mass estimates of Euoplocephalus tutus."
^{2}Moreno-Bernal, Jorge W. "Size and paleoecology of giant Miocene South American crocodiles (Archosauria: Crocodylia)." Journal of Vertebrate Paleontology 27.3 (2007).

[dinosauria101]

Would someone be able to tell me what (Cerato's post above) says? The device I am on won't let me scroll down to see it for some reason

[Ceratodromeus]

The tldr version of it is that the 2.5t figure given by paul in his book is undersized and a better estimate of ~3.4t is given, for P.mirandai using large alligators and saltwater crocodiles as a base, estimates for two specimens were 1.7 and 2.1t respectively.

[dinosauria101]

Can't really see that either. For that matter, I cannot actually see this thread from Cerato's first post and down.

What the heck, I'll reply to it later. This isn't a very good device.

[dinosauria101]

Ah, I see now. P. mirandai may have a good size advantage.

I would still favor the ankylosaur due to reach, mobility, and the club, but probably closer than I thought.

[Infinity Blade]

No, it suggests Euoplocephalus may have a good size advantage. 3.4 tonnes>2.156 tonnes.

That said, I'm not very sure of 3.4 tonnes for Euoplocephalus. Stephen Hurrell (here's-> the full publication that Cerato took a shot from, for anyone interested) gets this mass estimate from using a commercially available model. He justifies using it in that it was apparently sculpted by a paleoartist and seems to be high-quality, but I'm not really confident in the rigor of such an estimate. Also, he himself even brings up mass estimates from the scientific literature that are based upon limb bone circumference equations, suggesting an animal weighing some 2.2 or 2.3 tonnes. If this means that the leg bones of Euoplocephalus cannot withstand the mass of an animal weighing more than ~2.2 tonnes (correct me if I'm wrong on this), then I question the methodology obtaining 3.4 tonnes.

This may not seem like a problem to Hurrell, who believes Earth's gravity was lower in the past and takes all of this to calculate that the Earth's gravity was 0.65 g* 76 Ma, but...I don't assume any of us here actually believe that, right?

*2.21/3.40=0.65. Note how he calls the stylopodial shaft circumference estimates "weight" and not "mass". What he's basically saying is that leg bones that can bear a weight of up to 2.21 tonnes can hold up a body with an actual mass of 3.4 tonnes if Earth's gravity is lower at 0.65 g. But again, I don't suppose any of the posters here also subscribe to the Expanding Earth theory.

[dinosauria101]

Oops. Got that backwards.

So it's POSSIBLE for Euoplocephalus to be a good bit larger here, but that's to be taken with a grain of salt as per what was said above?

Edit: ok, looks like Euoplocephalus is the bigger animal here pretty much no matter how you slice it, though how much bigger is up for debate.