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Post by Grey on Dec 18, 2017 0:47:58 GMT 5
Post here your opinions, analysis or guess regarding the likelihood of this.
For the recall, this pliosaur specimen, variously estimated to have had a TL of 12-15 m has sometimes been described as a juvenile/subadult, raising the question of the size of an adult.
Furthermore, two of the describers claim one of the bite marks on a cranial bone suggest the agressor, likely another pliosaur, had a crown height of 30 cm.
They avoided to use a size figure in the literature but either in medias, interviews and email conversation, consider the agressor was in the 20-25 m range.
What would you think about the possibility of this ?
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Post by creature386 on Dec 18, 2017 1:59:15 GMT 5
I consider the a priori likelihood of it being that great to be small. Why? First of all, the ecosystem would have difficulties supporting such behemoths. Leedsichthys was way smaller than it and it would've been the only suitable food. Secondly, coherentsheaf made a good point about the a priori likelihood of exceptionally large animal: Nope. I view them as more likely because they are more likely. If we [w]ere to plot the totality of animal sizes on a density plot, the larger the animals are the fewer of them exist. From there it is a straightforward application of Bayes theorem that more conservative explanations should have more weight. If the a priori likelihood of the MoA being that large is small, the rule "extraordinary claims require extraordinary evidence" applies. The status of the known MoA specimen as a juvenile is dubious to say the least and a simple growth extrapolation is too weak evidence. |
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Post by Grey on Dec 22, 2017 9:58:52 GMT 5
I tend to agree but I'd like to really exclude any doubt about this.
I know that vertebral measurements in McHenry 2009 do suggest up to 12 m TL, compared with Kronosaurus. Are there other comparisons with other pliosaurs ?
The neural spine is reported 400 mm high in Aramberri. The neural spine in Andrews Liopleurodon is 170-173 mm high. This Liopleurodon has a maximum mandible length of 154 cm. Scaling up from the neural spine result in a mandible around 356 cm for Aramberri. Admitting this Liopleurodon was 6.4 m (Noé 2001), this results in a TL estimate of 14.8 m TL for Aramberri.
So is there any reason to thing vertebral measurements would be less reliable than the whole neural spine ?
Aramberri femoral head is 450 mm. Buchy (2006) compared it with the Tübingen Liopleurodon material and concluded a TL about 15 m as well...
I'd like to see other comparison of femoral measurements to be sure.
Also, what about the alleged juvenile/subadult status ?
This specimen has unfused vertebra. This is usually referred as a juvenile status (Brown 1981) but possible pedomorphy is said to be possible as well. The Svalbard specimens also have unfused vertebra but are adults in all other aspects (presence of a tuberosity on the humerus and a well developed anterior process on the coracoid, and abnormal hardening and increase in density of bone, indicate that both specimens were adult individuals).
So unfused vertebra seems unreliable to confirm immaturity. However Buchy 2006 reports that all the cranial bones in Aramberri show open sutures. Does that mean definitive immaturity ? I recall the arthritic pliosaur was confirmed as an adult because the skull bones are fused.
Since the Aramberri seems to not have fused bones, could that confirm a juvenile status after all ?
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Post by prehistorican on Dec 25, 2017 5:09:27 GMT 5
Haven't we seen unfused vertebrae in other adult pliosaurus like p. funkei? If there is no direct evidence for this extraordinary claim, them I would consider it unlikely. I think the max pliosaurus could hypothetically attain based off of the specimens we have are 15m.
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