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Post by Godzillasaurus on Nov 30, 2014 23:43:13 GMT 5
Nope, we are not discussing the fulcrum of the jaws. Obviously an animal cannot bite there, the posteriormost point it can bite with is the last tooth position, and that’s also what posterior bite force numbers refer to. The specimen in question is Pliosaurus kevani. I’ve already made a thread posting its official description paper, several others in this thread have referred to it, and so has the article in question. The fulcrum is the point where the bite force would naturally be the strongest, simply because that is the area least-affected by distance from the origin of the force (jaw muscles). But just like you said, of course that is also the least-practical area to bite with in predator, unless of course that said animal is going to be crushing shellfish or turtles. |
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Post by Grey on Dec 1, 2014 5:14:33 GMT 5
coherentsheaf blazeWhat are your opinion about the ontogenetical stage of the Aramberri pliosaur and of others pliosaurs ? Since Benson says it's still possible that we have yet to found truly adults individuals for many pliosaurs species, I wonder. Same thing regarding the bite mark on the pterygoid bone of the specimen, if a gigantic tooth really did this like claim Frey and Stinnesbeck, is it surprising or not necessarily that we haven't found such large isolated teeth ? The bite marked bone. Frey says that three T. rex teeth could fit in it. 
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Post by Grey on Dec 1, 2014 6:39:28 GMT 5
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blaze
Paleo-artist 
Posts: 766
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Post by blaze on Dec 1, 2014 8:48:57 GMT 5
Large but not extremely so, the height and length given are for the full vertebrae, centrum width is ~175mm, for comparison the range of dorsal centrum width in the Harvard Kronosaurus is 158mm-192mm.
I really don't have an opinion on the ontogenic stage of large pliosaurs, I don't know much about it, about the bite mark I'm in the dark too haha I'll read up on it though.
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Post by theropod on Dec 1, 2014 11:07:53 GMT 5
Nope, we are not discussing the fulcrum of the jaws. Obviously an animal cannot bite there, the posteriormost point it can bite with is the last tooth position, and that’s also what posterior bite force numbers refer to. The specimen in question is Pliosaurus kevani. I’ve already made a thread posting its official description paper, several others in this thread have referred to it, and so has the article in question. The fulcrum is the point where the bite force would naturally be the strongest, simply because that is the area least-affected by distance from the origin of the force (jaw muscles). But just like you said, of course that is also the least-practical area to bite with in predator, unless of course that said animal is going to be crushing shellfish or turtles. The fulcrum of the jaw equals the craniomandibular joint. It's the least practical region to bite with because it does not bear teeth, and because the jaw muscles are in the way of putting something in there to bite it… |
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Post by coherentsheaf on Dec 1, 2014 11:34:55 GMT 5
There are other indicators of adulthood than sutures in plesiosaurs, discussed in the description of Pliosaurus funkei:
"In the vertebral column of PMO 214.135 and PMO 214.136,
none of the neural arches are fused to their centra. It is
noteworthy that the fusion of neural arches with vertebral
centra has not been observed in any of the Pliosaurus
specimens examined in this study, nor has this been previously
reported for any other of the large pliosaurids (e.g., Philips,
1871; Tarlo, 1959 a and b; 1960; Halstead, 1971; Buchy, 2007),
and it is therefore difficult to determine whether this is truly
a reliable indicator of a juvenile or whether it is possibly a
paedomorphic feature in pliosaurids. The humerus of PMO
214.135 has a distinct tuberosity that is partially separated
from the capitulum, suggesting it is a mature individual
(Brown, 1981). The coracoid bears a well developed anterior
process, normally seen in adult specimens, when present
(pers. obs., EMK). Wiffen et al. (1995) discussed potential
histological indicators of ontogeny in a Late Cretaceous
elasmosaurid and a pliosauroid. They noted that adult
specimens had an osteosclerotic pattern of growth compared
to the pachyosteosclerotic bones of juveniles (but see
discussion in Liebe & Hurum, 2012). The cervical vertebral
centra of PMO 214.135 and PMO 214.136 display a clear
osteosclerotic state with a very spongy internal structure. Thus,
morphological and histological characters indicate that both
Svalbard specimens were adult individuals."
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Post by Grey on Dec 1, 2014 12:36:03 GMT 5
Very good and highlighting points blaze and coherentsheaf.
Coherenthsheaf, I don't remember all the preserved parts in the Mexican specimen but does these features helping to identify ontogeny in the two Pliosaurus funkei specimens is available in the Aramberri pliosaur so far ?
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Post by Grey on Dec 1, 2014 13:29:37 GMT 5
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Post by theropod on Dec 1, 2014 19:46:58 GMT 5
That's interesting, I should not have missed is. In this case, neurocentral sutures really don't seem ti be a reliable indicator of ontogenetic stage in pliosauridae.
Perhaps Frey and Stinnesbeck are basing their assessment on the features quoted above, or the lack thereof, but of course that's not a necessary conclusion.
But I think what's in order is a histological analysis to evaluate what pliosaurid growth curves would look like. Perhaps the animals were quite old and large, despite the presence of active growth zones.
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Post by coherentsheaf on Dec 2, 2014 3:50:24 GMT 5
Excellent find grey. The article gives conflicting sizes. If the 2.7m long head/30 tonnes is correct that one is seriously massive. 20cm teeth and 10m total length on the other hand are in the normal huge range. Can a native speaker maybe translate/explan this?
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Post by coherentsheaf on Dec 2, 2014 3:52:53 GMT 5
Grey, the Wiffen et al. criteria should probably be applicable. Depending on completeness of propodials/ coracoids others should be applicable as well.
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blaze
Paleo-artist
Posts: 766
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Post by blaze on Dec 2, 2014 4:11:36 GMT 5
Native speaker here, the reference is a press release so don't expect much accuracy in their statements.
The specimen is said to be complete from snout to tail (only missing the right limbs) and measures 9.9m. It indeed says the head is 2.7m but given the total length such measurement is probably untrue. The press release does mention an estimate of 30 tonnes but says it's for the genus but in such a way as if treating "pliosaurs" as a genus. Either way who knows from where that number came from.
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Post by coherentsheaf on Dec 2, 2014 4:37:16 GMT 5
Thanks blaze. Anything interesting in the video?
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Post by coherentsheaf on Dec 2, 2014 4:43:48 GMT 5
Note: On other pages of the blog it is also mentioned with 2.7m skull length. Balze could you write them an email asking for clarification?
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Post by Grey on Dec 2, 2014 9:31:06 GMT 5
I think the 30 tons figure is a gross, unprecise estimate taken on the internet like dinosaurs.about. I also suspect the 2.70 m skull figure is taken from the usual size figures attributed to the Harvard Kronosaurus skull. The 9.9 m figure seems reliable though as it's quite precise. There's apparently not yet properly studied and published, but I'm surprised that none of the main marine reptiles experts report it. I'm gonna send this to Adam Stuart Smith.
That's very exciting, this guy is impressively complete and will clearly bring much more knowledge about the anatomy and proportions of these giants predators.
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