Top Dog

[Grey]

Well there's something unclear somewhere. Post-cranial anatomy of very large Jurassic pliosaurs is poorly known anyway. McHenry said that his estimates are prone to numerous problematic factors.

But I tend to think that the latest published size estimates of Liopleurodon and Pliosaurus are subject to sensitive underestimate and that Kronosaurus based estimates for Peterborough can be questionned.

[Grey]

Frankly, looking at this, if teeth tell anything, and if there are really 40-45 cm pliosaurs teeth out there, I don't understand why +20 m pliosaurs aren't considered as a serious scientific possibility. I mean, all in all, such teeth would be twice larger than this material.

[theropod]

Look at the Tübingen Liopleurodon, its teeth are proportionately far longer than the ones that were preserved in P. kevani.

[Grey]

Yet Smith used the similar-sized kevani for comparison. To me the possibility seems to exist, it is not certain but certainly not speculative.

[theropod]

The question is how much of it is the effect of variation, and how much just preservation. But as I already mentioned, it looks like tooth size is very variable.

[creature386]

Feb 18, 2015 21:50:58 GMT 5 Grey said:

Yet Smith used the similar-sized kevani for comparison. To me the possibility seems to exist, it is not certain but certainly not speculative.

Unless there is a phylogenetic analysis that shows that the owner of the tooth is closer to Pliosaurus than to Liopleurodon, both are valid for comparisons.

[blaze]

Is that tooth supposed to be complete? in Liopleurodon the crown is only about a third of the whole length, that's why I estimated it at least 33cm before but if the whole teeth is actually 22.5cm and the crown is 13.1cm then we are looking at teeth with different proportions to Liopleurodon.

[theropod]

No, that tooth definitely isn’t complete. This is what a complete (or nearly complete) pliosaur tooth looks like:

The right hand side, obviously.

That one has most of its root missing. There is no other option than to go by width and crown height in such cases, that doesn’t automatically make crown heights more reliable.

By comparison with Liopleurodon, the crown height of a 45cm pliosaur tooth would be expected to be 16-18cm, that’s a far call from being twice the size of that giant tooth up there, but about 24-36% larger. Assuming that this tooth came from an individual similar in size to the Weymouth bay pliosaur, the dorsal skull lenght for a 45cm tooth would be ~2.5-2.7m, putting it approximately on par with the Oxford P. macromerus.

The question for estimating body size tough, remains whether the measurement reported for the Tübingen Liopleurodon is dorsal, condylobasal or maximum skull lenght, or perhaps mandibular lenght, and how long the specimen is when fully restored.

[Grey]

Adam Smith who studied the tooth and deduced the body size estimate doesn't know how much of root is lacking but not necessarilly much because for the longest crowned teeth in kevani (see my comparison) I very much doubt there's certainly 2/3 of root below. That doesn't make sense given the depth of the snout.

It is well possible that the "Pliosaurus grandis" tooth doesn't represent the largest caniniform, long crowned teeth in the dentition, the crown is not reminescent of the very longest crowns we can see in pliosaurs dentitions. I think that depending the position, the root constitutes either 2/3 or 1/2 of the tooth.

So the Liopleurodon ferox giant tooth here wasn't necessarilly 33 mm originally but a bit more than the measured 22.5 cm.

I agree that the fact the longest teeth from Andrews specimens can throw some cold water on it and makes a 40 cm toothed pliosaur more in the 15-17 m range (which is still enormous) and that given the variation there will be always uncertainties but until I (we) have a look at these gigantics specimens, the possibility of baleen-whale size is present. While comparing that Liopleurodon tooth with that kevani tooth within the skull, I justifiably wonder how large would be a pliosaur with the same tooth almost twice larger. But again we need a look at it.

Also, Leslie Noé certainly agrees that any size estimates for Jurassic pliosaurs based on Kronosaurus data from McHenry are conservative or underestimates. He also says that the often reported ~10 m length for Liopleurodon is based on isolated teeth, like this one. I surely believe that 6.4 m for Andrews 1.26 m skull is too low.

[theropod]

But the longest Liopleurodon teeth described by Andrews have a crown slightly over a third the entire tooth lenght (those are the proportions I used), quite similar to the P. grandis tooth, and these are very likely the largest, or among the largest in the dentition. Why should the longest teeth in the dentition would have disproportionately short roots?

The end of the tooth also looks like its broken off neatly at about the thickest part, apical to where the root gradually tapers in more complete pliosaur teeth. So unless against all indication some teeth had drastically different root morphology, there’s quite a big part missing in that specimen.

[Grey]

I surely think to have seen pliosaurs teeth where the root is more about 1/2 than 1/3. The short crown in the Pliosaurus grandis tooth makes me somwhat doubting it's the largest tooth in the dentition, expectedly the largest teeth are composed of a long blade-like crown.

Look at the P. kevani photo I've posted above or at this piece :



I very much doubt the root is twice the size of the crown seen here in that piece, or it would protrude out of the snout. Same case for the big tooth in kevani I've posted above. See my point ? So, I don't argue anything for now, but if this is the case in the giants teeth we're looking at, we could have crowns at 20 cm or more.

Also, I start to wonder if crown measurement isn't less variable than the root, and thus crowns could be (slightly) more reliable to use than a complete tooth.

BTW, this Kronosaurus snout piece was found in 1932 and is 54 cm long. They describe it as being from a 3 m skull originally but could someone try to compare it to a more complete Kronosaurus skull to get a possible estimate from this one ?

I've roughly measurement the big crown at 13 cm and 6.5 cm wide...


About the Monster of Aramberri, we've discussed something with coherentsheaf.

We know that unfused neural arches, seen in the Aramberri but in other giants pliosaurs as well (Svalbard), are apparently not necessarilly indicating a juvenile status.

We know that the Westbury pliosaur, a large-sized pliosaur, is authentified as an old adult, based on several factors including that sutural fusion in the skull of the specimen.

I've looked again at Buchy's thesis where she describes the specimen and found this :

Cranial fragments were found as isolated debris, although most are unidentifiable. All cranial fragments show open sutures

The Aramberri pliosaur shows open sutures not only in the backbone, but also in the skull fragments, unlike the confirmed adult Westbury pliosaur.

This strongly seems to suggest the Aramberri pliosaur to be a juvenile if you ask me but I'd like to see if others large pliosaurs skulls, considered adults, show fused sutures or not.



Another thing, I've foun this page with this very interesting and beautiful specimen. www.natural-history-conservation.com/pliosaurskull.htm

They report a skull size about 1.8 m but I have asked them for more precisions about it, awaiting the response.



Here again, I doubt the biggest crowns we see in that snout have a root twice their length.

[theropod]

Feb 20, 2015 12:09:38 GMT 5 Grey said:

I've looked again at Buchy's thesis where she describes the specimen and found this :

Cranial fragments were found as isolated debris, although most are unidentifiable. All cranial fragments show open sutures

It’s good that you looked it up, I seemed unable to locate the passage when I looked for it. So regardless of the diagnostic value of neural-arch-fusion, cranial fusion does occur in giant pliosaurs, but is not present in the Aramberri specimen. As Knutsen stated, perhaps this is related to something else, but so far ontogeny seems to be the most compelling explanation for it. It would be strange for some pliosaurs of equivalent ontogenetic stage and similar skull morphology to have kinetic skulls while they are fully co-osssified in others.

[Grey]

So maybe a juvenile status IYO ?

[theropod]

Rather subadult or young adult (depending on the exact onset of sexual maturity in these species), that seems realistic. But it requires further confirmation from a decent sample of skulls. Of course from what we have right now, it seems as if animals of this stage of maturity were exceedingly rare in pliosaurs, so there’s our problem. But ontogeny appears to be the most parsimonous explanation for variations in skull fusion, based on the size distributions.

[Grey]

I'd like to have data about the state of fused sutures in a subadult/young adult reptile taxon to get a comparison with Aramberri. And if there are or not other large pliosaurs specimens with unfused cranial sutures.