Post by ted on Apr 5, 2011 19:30:07 GMT
After further contact with pliosaurs experts, I've came to the conclusion (their own conclusion), that there was no 20 m or more pliosaurs :
First an email from Dr Richard Forrest, plesiosaur expert :
I haven't seen the Aramberi specimen, but all the large pliosaurspecimens I have examined have characters which appear juvenile. Ithink that this is because paedomorphosis, but extending the period ofmaximum rate of growth is the mechanism which allowed them to reachsuch extreme sizes.
About size estimates of pliosaurs :
I'd be cautious about these estimates of size. The Weymouth Baypliosaur has an exceptionally well-preserved skull which allowsaccurate measurement of its length, but the Svalbard specimens arebadly frost-shattered and will take a lot of preparation to give muchof an idea of how big they actually are. Jorn Hurum has a reputationfor exagerating the significance of specimens!
About the bite marks on the skull of the Aramberri Monster (7 cm wide for the largest)
A width of 5-7 cm is equivalent to the root diameter of the Svalbardspecimen, and close to that of the largest teeth on the Weymouth Bay specimen. It is possible that the size of the bite mark on Aramberri specimen is enlarged by movement of the animal when the tooth of thepredator was embedded. I've seen this in several of the tooth-marks I have studied on smaller pleiosaurs.
About the theory of more than 20 m pliosaurs :
I have some reservations on this. My personal view is that these three specimens represent the most extreme size possible for an activepredator. It is close to that of the largest mosasaurs andichthyosaurs. I would think that there are biomechanical and metabolic constraints on the size of these mega-predators.
About the durability of pliosaurs to wounds :
is it possible for a pliosaur to survive a such nasty wound, maybe being as durable as crocodiles ?
Most certainly! I have studied bite marks on numerous specimens of smaller plesiosaurs, and some of them suffered severe injuries fromwhich they recovered. The tips of the lower jaws of both large pliosaur skulls in Bristol Museum have been bitten off, and have healed. The most severe injuries I have come across are on a juvenilespecimen of the long-necked plesiosaur Cryptoclidus. The pelvic girdle has been crushed and badly distorted, but shows a growth of bone around the fractures showing that it was able to survive a savageinjury. Both femora of this individual have several bite marks, one ofthe associated with a deep, smooth-sided excavation into the bone which looks very much like a necrotising fascitis.
About the weight estimates he gives to pliosaurs :
It's very hard to calculate the weight of an animal known only fromits bones. My estimates are based on measuring the displacement of apliosaur model, and assuming a density the same as that of water,which seems reasonable for an aquatic animal. However, that relies onthe accuracy of the model. It's worth noting that because weightincreases with the cube of linear dimensions - an animal twice as longwill be eight times the weight - an 18 meter pliosaur is almost twice the weight of a 15 meter pliosaur.
Email for Espen M Knutsen (Svalbard pliosaurs), also about the MOA and Predator X weight:
The weight of the pliosaur was calculated by a third party for the documentary that was made. It is of course an estimate based on assumptions of the bulk size of the animal (which is unknown). So there is room for error here. It is however not unlikely that the animal reached such a weight as this increases rapidly with length. As for the status of the 'Aramberri monster' I know that Buchy et al. based their assumprion of the animal being a juvenile on the lack of fusion between neural arches and vertebral centra. This is used in other plesiosaurs as well. However, none of the reported pliosaurs ever found show this fusion. It would be very unlikely that all pliosaurs ever found are juveniles. The other and ,in my opinion, more likely explanation is that pliosaurs exhibited some degree of paedomorphy. If one looks at other remains of pliosaurs it is evident that all are adult animals in all other respects. And I am sure that this is also true for the Aramberri monster. I know that they also have allegedly found a tooth mark/punchture in the cranium of the Aramberri monster, and that the tooth crown making the mark is estimated to ~30 cm long. Since the tooth crown in pliosaurs only constitute one-third of the total tooth length, this must mean that the tooth was 90cm long, which sounds totally unreasonable. I do not believe that any of the known types of pliosaurs exceeded 15 m in body length. There just aren't enough evidence to support this.
And now from Dr Marie-CĂ©line Buchy, french pliosaurs expert, discoverer of the MOA which she wrote some papers.
She said me :
The journalists are often too enthousiastic for really listen the answers. The Monster of Aramberri measured around 15 metres long. There is no indication of the 18 m which are seen on the internet. With "only" 15 metres long, it is yet the largest pliosaur known, or surely identified.
I don't think that it was a juvenile in the mammal's way. That the serious paleontolgists say by "juvenile", is that the skeleton is only partially ossified. I think that it not means that it didn't have reached its sexual maturity. In fact, the found of Epsen in Svalbard which have around the same lenght, indicates that may have been a "normal" size for these beasts. A partially ossified skeleton (even for the adults) allowed to economise weight and calcium. Which explains also why we know so little of these big fossil beasts, as the cartilage generally isn't preserved, so the skeletons should quickly be dislocated and the bones scattered.
We are talking about animals which spent all their life in the open sea, so died there, in places somewhat favorable for fossilization, and isolated bones can be confused with those of dinosaurs, etc..
The Monster would be sperm whale-sized. Of course, we can speculate on the size that a very old individual could have reached, as the Monster wasn't too old when it died, but there is no fossil proof for now.
As for the bite marks, they are located in a region of the skull which is not very high, even in a large pliosaur, and and since the mandible is very long, the culprit could also be around 15 m long, not necessarily more.
I will write the next answer of Dr Buchy later.
So far, it seems that pliosaurs, as mean and powerful they were, didn't reach the 20 m range.
For what we know today :
Predator X : 15 m
MOA : 15 m
Weymouth Bay : 10-16 m, likely 12 m.
The Cumnor Monster (Pliosaurus macromerus) : 15-18 m.
First an email from Dr Richard Forrest, plesiosaur expert :
I haven't seen the Aramberi specimen, but all the large pliosaurspecimens I have examined have characters which appear juvenile. Ithink that this is because paedomorphosis, but extending the period ofmaximum rate of growth is the mechanism which allowed them to reachsuch extreme sizes.
About size estimates of pliosaurs :
I'd be cautious about these estimates of size. The Weymouth Baypliosaur has an exceptionally well-preserved skull which allowsaccurate measurement of its length, but the Svalbard specimens arebadly frost-shattered and will take a lot of preparation to give muchof an idea of how big they actually are. Jorn Hurum has a reputationfor exagerating the significance of specimens!
About the bite marks on the skull of the Aramberri Monster (7 cm wide for the largest)
A width of 5-7 cm is equivalent to the root diameter of the Svalbardspecimen, and close to that of the largest teeth on the Weymouth Bay specimen. It is possible that the size of the bite mark on Aramberri specimen is enlarged by movement of the animal when the tooth of thepredator was embedded. I've seen this in several of the tooth-marks I have studied on smaller pleiosaurs.
About the theory of more than 20 m pliosaurs :
I have some reservations on this. My personal view is that these three specimens represent the most extreme size possible for an activepredator. It is close to that of the largest mosasaurs andichthyosaurs. I would think that there are biomechanical and metabolic constraints on the size of these mega-predators.
About the durability of pliosaurs to wounds :
is it possible for a pliosaur to survive a such nasty wound, maybe being as durable as crocodiles ?
Most certainly! I have studied bite marks on numerous specimens of smaller plesiosaurs, and some of them suffered severe injuries fromwhich they recovered. The tips of the lower jaws of both large pliosaur skulls in Bristol Museum have been bitten off, and have healed. The most severe injuries I have come across are on a juvenilespecimen of the long-necked plesiosaur Cryptoclidus. The pelvic girdle has been crushed and badly distorted, but shows a growth of bone around the fractures showing that it was able to survive a savageinjury. Both femora of this individual have several bite marks, one ofthe associated with a deep, smooth-sided excavation into the bone which looks very much like a necrotising fascitis.
About the weight estimates he gives to pliosaurs :
It's very hard to calculate the weight of an animal known only fromits bones. My estimates are based on measuring the displacement of apliosaur model, and assuming a density the same as that of water,which seems reasonable for an aquatic animal. However, that relies onthe accuracy of the model. It's worth noting that because weightincreases with the cube of linear dimensions - an animal twice as longwill be eight times the weight - an 18 meter pliosaur is almost twice the weight of a 15 meter pliosaur.
Email for Espen M Knutsen (Svalbard pliosaurs), also about the MOA and Predator X weight:
The weight of the pliosaur was calculated by a third party for the documentary that was made. It is of course an estimate based on assumptions of the bulk size of the animal (which is unknown). So there is room for error here. It is however not unlikely that the animal reached such a weight as this increases rapidly with length. As for the status of the 'Aramberri monster' I know that Buchy et al. based their assumprion of the animal being a juvenile on the lack of fusion between neural arches and vertebral centra. This is used in other plesiosaurs as well. However, none of the reported pliosaurs ever found show this fusion. It would be very unlikely that all pliosaurs ever found are juveniles. The other and ,in my opinion, more likely explanation is that pliosaurs exhibited some degree of paedomorphy. If one looks at other remains of pliosaurs it is evident that all are adult animals in all other respects. And I am sure that this is also true for the Aramberri monster. I know that they also have allegedly found a tooth mark/punchture in the cranium of the Aramberri monster, and that the tooth crown making the mark is estimated to ~30 cm long. Since the tooth crown in pliosaurs only constitute one-third of the total tooth length, this must mean that the tooth was 90cm long, which sounds totally unreasonable. I do not believe that any of the known types of pliosaurs exceeded 15 m in body length. There just aren't enough evidence to support this.
And now from Dr Marie-CĂ©line Buchy, french pliosaurs expert, discoverer of the MOA which she wrote some papers.
She said me :
The journalists are often too enthousiastic for really listen the answers. The Monster of Aramberri measured around 15 metres long. There is no indication of the 18 m which are seen on the internet. With "only" 15 metres long, it is yet the largest pliosaur known, or surely identified.
I don't think that it was a juvenile in the mammal's way. That the serious paleontolgists say by "juvenile", is that the skeleton is only partially ossified. I think that it not means that it didn't have reached its sexual maturity. In fact, the found of Epsen in Svalbard which have around the same lenght, indicates that may have been a "normal" size for these beasts. A partially ossified skeleton (even for the adults) allowed to economise weight and calcium. Which explains also why we know so little of these big fossil beasts, as the cartilage generally isn't preserved, so the skeletons should quickly be dislocated and the bones scattered.
We are talking about animals which spent all their life in the open sea, so died there, in places somewhat favorable for fossilization, and isolated bones can be confused with those of dinosaurs, etc..
The Monster would be sperm whale-sized. Of course, we can speculate on the size that a very old individual could have reached, as the Monster wasn't too old when it died, but there is no fossil proof for now.
As for the bite marks, they are located in a region of the skull which is not very high, even in a large pliosaur, and and since the mandible is very long, the culprit could also be around 15 m long, not necessarily more.
I will write the next answer of Dr Buchy later.
So far, it seems that pliosaurs, as mean and powerful they were, didn't reach the 20 m range.
For what we know today :
Predator X : 15 m
MOA : 15 m
Weymouth Bay : 10-16 m, likely 12 m.
The Cumnor Monster (Pliosaurus macromerus) : 15-18 m.