Have I missed something ? There are really evidences of 20 m pliosaurs ?

[Komodo]

I thought it was well known since a decade how the pliosaurs have been over-inflated in size by the popular medias and that anything over 15 m was baseless and suspicious. I think the latest modern analysis of upper size for these beasties was about 12-13 m (McHenry 2009).

But still, I see here and there claims that there are evidences of sperm whale-size pliosaurs (20 m or more), though I have never seen these in the scientific litterature, and I don't think any private has such material indicating this.


I have missed something or is this simply sheer internet fanboyism ?

[Komodo]

No one is aware of something new about this so far ?

[Halichoeres]

Who's making the claim? Have any links?

[Libraraptor]

Our admin will know the answers!

[Dinoguy2]

But still, I see here and there claims that there are evidences of sperm whale-size pliosaurs (20 m or more), though I have never seen these in the scientific litterature,

There's your answer, if it's not in the scientific literature it's a baseless claim.

[Komodo]

I don't have any clear links. That's a claim still well frequent among paleo-enthusiasts. That's apparently based on the premise about the Aramberri pliosaur that it was 15-18 m, not fully grown and apparently killed by an even larger pliosaur.

I think Dr. David Martill still argues about super-sized Liopleurodon-like beasties from the Oxford Clay on the basis of isolated fragmentary remains.

A novelist named Max Hawthorne (there is a review of his novel on plesiosaur bites) regularly argues to his followers that there are scientific evidences of 20 m + pliosaurs (but some people told me this guy is somewhat of a pliosaur fanatic with a propencity to exaggerate...).

As for the litterature, there is this recent account :

https://books.google.fr/books?id=hQgiAwAAQBAJ&pg=PA87&lpg=PA87&dq=300+mm+crown+pliosaur&source=bl&ots=FWj6Tci29X&sig=fAtTCZIZKPCnUssofTilm_OBLVY&hl=fr&sa=X&ved=0CBsQ6AEwAGoVChMIh5acloaAyQIVgW8UCh1LpQJp#v=onepage&q=300%20mm%20crown%20pliosaur&f=false

The authors say the tooth that punctured the skull of the Aramberri pliosaur needs to have had a 300 mm long crown to pierce through the pterygoid bone.

An estimated 6.4 m Liopleurodon had its largest crown length about 75-85 mm long, so you do the math for a 300 mm long crown... Even if scaling from tooth is probably filled with a potential large error bar, there is little doubt that a pliosaur with crowns around 300 mm would be gigantic. But is there such a large isolated crown known from private collections or Museums ?

[DinoToyForum]

You haven't missed anything. You've nicely summed up the state of affairs as things stand. There is more speculation than fact...

This is Adam Smith by the way.

[Komodo]

Oh hello Adam !

There is more speculation than fact, but is this utterly baseless speculation ?

Is it really necessary the animal that killed the Aramberri pliosaur needed a crown length of 30 cm to puncture the pterygoid bone ?

The authors avoid speculations in the paper but elsewhere they seem confident that there were 20 m plus pliosaurs, unless it is a post WWD Liopleurodon effect...

[DinoToyForum]

Oh hello Adam !

There is more speculation than fact, but is this utterly baseless speculation ?

Is any speculation truly completely baseless? Let's put it this way: there's no verified scientific basis for pliosaurs over 12-13m.

Is it really necessary the animal that killed the Aramberri pliosaur needed a crown length of 30 cm to puncture the pterygoid bone ?

Here's how the book describes the tooth marks:

"Two of the skull bones, the pterygoid and the jugal, show bite marks produced by massive teeth, most likely of another pliosaur. The bite that hit the dorsal face of the horizontal ramus of the pterygoid was produced by a tooth with a diameter of about 60 mm near the crown tip. The tooth penetrated the skull, most likely through the supratemporal aperture, suggesting a crown length of about 300 mm. Despite the massive injury, the puncture is sealed with callus. The victim thus survived the bite. In contrast, the bite mark on the external face of the jugal (Fig. 5.5B) shows sharp margins and was produced by a tooth about two-thirds the diameter of the one that punctured the pterygoid. This bite was likely lethal to the animal. " (p. 87)

That's all I know. This implies that the monster wasn't killed by the first injury, but got away. There's a lot of speculation in the above interpretation. Here are a few possible caveats that come to mind.

1. Maybe it isn't a tooth mark at all. It could be a pathology or other injury. If the callus is a misinterpretation then it could even be taphonomic in origin, or just damage caused during excavation.
2. Maybe it wasn't caused by a pliosaur, but some other animal. They only say "most likely".
3. Maybe the tooth penetrated from below, rather than through the supratemporal above. Again, they only say "most likely". To be honest, I struggle to visualise how a single tooth can pass through the supratemporal fenestra and puncture the pterygoid (on the palate) without the adjacent teeth and opposing teeth causing other damage or killing the animal. If it came from below then the tooth wouldn't need to be so long. Similarly, if the callus is a misinterpretation then the tooth mark may have been caused when the animal was dead. In this case, the skull could have been compressed/crushed and the distance the tooth had to travel (even from above) would be reduced.
4. Length to width ratios of pliosaur teeth vary, and their cross-sectional shapes vary. Basically, the length estimation is a guess.
5. Accurately estimating total animal length from a single tooth is impossible, even when the tooth length is known with certainty.
6. The 'second' tooth mark, the one without callouses, may be due to scavenging rather than the result of a killer blow.

I'm not saying any of the above is true, and I'm certainly playing devil's advocate in places, but it helps to show just how circumstantial this evidence actually is. I haven't seen the material myself, so I can't give my personal interpretation. As far as I'm aware the 'first' tooth mark has never been figured.

The authors avoid speculations in the paper but elsewhere they seem confident that there were 20 m plus pliosaurs, unless it is a post WWD Liopleurodon effect...

Where specifically?

Finally, why does it matter how big pliosaurs got?

[Komodo]

Let's put it this way: there's no verified scientific basis for pliosaurs over 12-13m.

Even from some English collections (large teeth and vertebra...) ?

1. Maybe it isn't a tooth mark at all. It could be a pathology or other injury. If the callus is a misinterpretation then it could even be taphonomic in origin, or just damage caused during excavation.
2. Maybe it wasn't caused by a pliosaur, but some other animal. They only say "most likely".
3. Maybe the tooth penetrated from below, rather than through the supratemporal above. Again, they only say "most likely". To be honest, I struggle to visualise how a single tooth can pass through the supratemporal fenestra and puncture the pterygoid (on the palate) without the adjacent teeth and opposing teeth causing other damage or killing the animal. If it came from below then the tooth wouldn't need to be so long. Similarly, if the callus is a misinterpretation then the tooth mark may have been caused when the animal was dead. In this case, the skull could have been compressed/crushed and the distance the tooth had to travel (even from above) would be reduced.
4. Length to width ratios of pliosaur teeth vary, and their cross-sectional shapes vary. Basically, the length estimation is a guess.
5. Accurately estimating total animal length from a single tooth is impossible, even when the tooth length is known with certainty.
6. The 'second' tooth mark, the one without callouses, may be due to scavenging rather than the result of a killer blow.

I'm not saying any of the above is true, and I'm certainly playing devil's advocate in places, but it helps to show just how circumstantial this evidence actually is. I haven't seen the material myself, so I can't give my personal interpretation. As far as I'm aware the 'first' tooth mark has never been figured.

I admit I had in mind some of these points. Clearly, the specimen lacks figures and examination by other fellow 'pliosaurologists'.

There is also the point that the Monster was at least juvenile/immature  which is used as argument for supersize in the adults. I have seen that P. brachydeirus, P. brachyspondylus and P. portentificus, are known exclusively from immature individuals. Isn't it a solid argument for speculations about 20 m individuals (though I don't know the exact size of these specimens) ?

Where specifically?

In various interviews since the first description of the specimen. In this presentation of the Univsersity of Heidelberg by Stinnesbeck : http://www.uni-heidelberg.de/fakultaeten/chemgeo/geow/forschungsgruppen/palaeontologie/aramberri.html

A German contact said me Frey is arguing the Monster was a sperm whale-sized baby and that it was killed by a larger individual in this video :

https://www.youtube.com/watch?v=D07b-kmpa8E

Here again, I find there is a lack of observations by others pliosaurs researchers (Knutsen, Druckenmiller, Benson, yourself...), but I understand the material is hardly accessible currently.

Finally, why does it matter how big pliosaurs got?

Well, on ecological grounds, there would be different implications between a 10 m pliosaur and a 20 m one that would weigh about eight times more. And of course, as badass-looking beasts, the scientific veracity of a 20 m pliosaur would be awesome  (not that I don't consider a 10 m pliosaur with a 2 m skull badass...)

[DinoToyForum]

Thanks for the links.

One point about the Monster of Aramberri being a juvenile. Paedomorphism is common in plesiosaurs, that is, retention of juvenile characteristics in sexually mature adults. This is a possible explanation for the apparent immaturity of the Monster of Aramberri.

By the way, I need to update my blog article (http://plesiosauria.com/news/index.php/mines-bigger-than-yours-the-monster-of-aramberri-predator-x-and-other-monster-pliosaurs-in-the-media/) with the new information from the Dinos of Mexico book...

[Komodo]

Thanks for the links.

One point about the Monster of Aramberri being a juvenile. Paedomorphism is common in plesiosaurs, that is, retention of juvenile characteristics in sexually mature adults. This is a possible explanation for the apparent immaturity of the Monster of Aramberri.

By the way, I need to update my blog article (http://plesiosauria.com/news/index.php/mines-bigger-than-yours-the-monster-of-aramberri-predator-x-and-other-monster-pliosaurs-in-the-media/) with the new information from the Dinos of Mexico book...

Apparently they base their observation of immaturity on the unfused cervical vertebra.
Are there pliosaurs specimens known with totally fused vertebra ?

[DinoToyForum]

Thanks for the links.

One point about the Monster of Aramberri being a juvenile. Paedomorphism is common in plesiosaurs, that is, retention of juvenile characteristics in sexually mature adults. This is a possible explanation for the apparent immaturity of the Monster of Aramberri.

By the way, I need to update my blog article (http://plesiosauria.com/news/index.php/mines-bigger-than-yours-the-monster-of-aramberri-predator-x-and-other-monster-pliosaurs-in-the-media/) with the new information from the Dinos of Mexico book...

Apparently they base their observation of immaturity on the unfused cervical vertebra.
Are there pliosaurs specimens known with totally fused vertebra ?

This is a question I'm currently exploring. If you (or anyone) is aware of any thalassophonean cervical vertebrae where the neurocentral sutures are completely fused, please let me know!

[Komodo]

Thanks for the links.

One point about the Monster of Aramberri being a juvenile. Paedomorphism is common in plesiosaurs, that is, retention of juvenile characteristics in sexually mature adults. This is a possible explanation for the apparent immaturity of the Monster of Aramberri.

By the way, I need to update my blog article (http://plesiosauria.com/news/index.php/mines-bigger-than-yours-the-monster-of-aramberri-predator-x-and-other-monster-pliosaurs-in-the-media/) with the new information from the Dinos of Mexico book...

Apparently they base their observation of immaturity on the unfused cervical vertebra.
Are there pliosaurs specimens known with totally fused vertebra ?

This is a question I'm currently exploring. If you (or anyone) is aware of any thalassophonean cervical vertebrae where the neurocentral sutures are completely fused, please let me know!

I think Buchy 2007 and McHenry 2009 talk about that.

Mesozoic marine reptiles from north-east Mexico: description, systematics,
assemblages and palaeobiogeography Marie-Céline Buchy 2007

Thus UANL-FCT-R2 represents the most complete very large pliosaur known to date, and
additionally exhibits an immature osteological condition, raising the question of the size, a fully
ossified member of the same taxon could have reached. It was shown that forms with unfused
neural arches represent juveniles in small (some meters long) plesiosaurian taxa (Brown, 1981).
Fusion of the neural arch to the vertebral body may have occurred earlier in life in pliosaurs than
in crocodiles (Buchy et al., 2006d); the growth rate of crocodiles most likely cannot be used to
estimate growth rate in pliosaurs. Crocodiles are small when they hatch because they have to
develop within the restricted space of an egg; on the contrary it was argued that pliosaurs were
ovoviviparous (Cheng et al., 2004; Buchy et al., 2005a). Thus newborns could be larger compared
to adults than are hatchling crocodiles, and the growth rate during the first months or years were
not necessarily similar. Another aspect is sexual maturity, which might have occurred before
osteological maturity, a phenomenon that is quite common, and possibly advantageous in
evolutionary terms (e.g. Gould, 1977; McKinney, 1988): the parents of UANL-FCT-R2 were not
necessarily much larger than it was when it died. Other far (but possibly closer) relatives are
lizards. Recent forms, however, differ from pliosaurs in many aspects, such as size, anatomy,
mode of life, etc., so that they cannot represent a reliable model for pliosaurs (see Buchy et al.,
2005a). Moreover, osteological maturity might never have been reached in very large pliosaurs, a
partly cartilaginous skeleton being then no sign of young individual age: adult giant pliosaurs
might have retained juvenile features including non-fusion of the bones (contra Buchy et al.,
2006d) as a consequence of e.g. enormous metabolic requirements or to save weight. Cartilage
might have played an essential role in their biomechanics. It is usually argued that cartilage is less
solid than bone, less resistant against the tensions created by muscles and movement; though, it is
also better absorbing shocks and loads (e.g. Evans, 2005 and references therein). Another, indirect
argument in favour of preservation in adult giant pliosaurs of a partly cartilaginous skeleton is the
rarity of such remains in the fossil record, when marine environments offer better opportunities
for fossilisation than continental ones and remains of sauropods as large as or larger than UANLFCT-
R2 are relatively common. Giant pliosaurs must have been rare in Late Jurassic ecosystems,
as are normally large carnivores as compared to herbivores; during geological time it must still
have represented series of populations comprising a sufficient number of individuals to breed. A
partly cartilaginous skeleton would help explain why so few among these were fossilised or had
their remains correctly identified.


'Devourer of Gods'
The palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus
A dissertation by
Colin Richard McHenry B.Sc.(Hons)

Buchy et al. (2003) estimate total size in the Aramberri specimen at 15 metres, on the basis of scaling from a much smaller specimen of Liopleurodon ferox. The potential problems of this approach cannot be over-estimated. Further, they claimed that the Aramberri specimen represented a juvenile ontogenetic stage, citing lack of fusion of the neural arches to the centra. However reliable this character may be in other groups of reptiles, its validity as an indicator of ontogenetic stage in pliosaurids and brachaucheniids is doubtful. Very few pliosaurid and no brachaucheniid vertebrae have the neural arches fused to the centra (pers. obs.); unless all of the large Kronosaurus specimens are interpreted as juveniles, it appears that this particular feature is paedamorphic in large pliosaurs and that claims that the Aramberri specimen is a juvenile are misplaced.


Claims of juvenile ontogenetic stage in the Aramberri specimen – and hence an implication of larger size in 'adults' – contradict the observed vertebral morphology of all Cretaceous large pliosaur material.

They seem pretty affirmative that unfused vertebra are not indicative of young age but still McHenry mentions "very few pliosaurids" with fused arches. Why this would occure in some specimens and not in others ?

In the description of Pliosaurus kevani :

At first glance, the Late Jurassic pliosaurid assemblage seems not to consist only of large-bodied species. Some specimens are smaller than 1700–2100 mm long, including the holotype of Pliosaurus brachydeirus (OXFUM J.9245), Knutsen's [34] proposed 'neotype' of P. brachyspondylus (CAMSM J.35991 [52]), and Gallardosaurus iturraldei [12] (Table 1). However, these specimens show juvenile features, indicating their small size is the result of incomplete growth, and suggesting that Late Jurassic pliosaurid body size diversity may have been low. These juvenile features include incomplete fusion of the atlas-axis complex (pers. obs. of CAMSM J.35991; and [12]) and possibly incomplete ossification of the proximal convexities of the radius and tibia (CAMSM J.35991; OXFUM J.9245). The cervical and dorsal vertebrae of these specimens preserve disarticulated centra and neural spines, indicating unfused neurocentral sutures, commonly also interpreted as a juvenile feature in reptiles. They also have dorsoventrally short neural spines, with incompletely ossified dorsal ends. This is also indicative of ontogenetic immaturity in sauropterygians [48]. However, the neurocentral sutures remain unfused in very large thalassophonean individuals, including Late Jurassic specimens such as CAMSM J.35990 [57], the holotype of Pliosaurus carpenteri (pers. obs. of BRSMG Cd6172) and the large Mexican specimen [2]. Thus, it is possible that vertebral sutural fusion was extremely delayed or never occurred in thalassophoneans. If so, vertebral sutural fusion cannot be used as a reliable indicator of ontogenetic stage in Thalassophonea (contra [2]). Alternatively, it is possible that despite their large body sizes, these specimen do represent juveniles, and truly adult specimens have yet to be discovered.

Could it be possible that the vast majority of the recorded pliosaurs specimens are actually immatures ? I think this case exists with some dinosaurs taxa, known by numerous specimens but all immature. But then, wouldn't we find some isolated very large pieces from adults ?

But Knusten et al. 2012 found another way to determine adult or juvenile stage in pliosaurs other than the neural arches fusion.

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.


Strangely Knutsen et al. say neural fusion has not been observed in any large pliosaur, but McHenry says this has been seen in very few specimens.

Also, I see that arthritis specimen is identified as an old adult on the basis of the fused skull bones.

So this would mean unfused skull bones are indicative of young age but not unfused vertebral bones ?

[Kovu]

Just being devil's advocate here, but couldn't preservation bias play a role, and with marine environments be taken to the extreme? There are parts of the prehistoric oceans that have been oceans throughout their history. Could smaller species and juveniles been living relatively closer to shore while truly massive pliosaurs been living far, far, far offshore? So far that when they died there's no hope of paleontologists ever even learning of their existence because any and all fossils are miles beneath the ocean surface and that's why there's only rumored fused verts?

This is something I've always wondered. Pliosaurs and other marine species aren't really something I'm particularly well versed in though, so if I'm wrong, sorry.

[Komodo]

Just being devil's advocate here, but couldn't preservation bias play a role, and with marine environments be taken to the extreme? There are parts of the prehistoric oceans that have been oceans throughout their history. Could smaller species and juveniles been living relatively closer to shore while truly massive pliosaurs been living far, far, far offshore? So far that when they died there's no hope of paleontologists ever even learning of their existence because any and all fossils are miles beneath the ocean surface and that's why there's only rumored fused verts?

This is something I've always wondered. Pliosaurs and other marine species aren't really something I'm particularly well versed in though, so if I'm wrong, sorry.

This could be applied to any kind of extinct large organism. But we already have found specimens of very large ichthyosaurs (Shonisaurus, Shastasaurus, Temnodontosaurus...), very large cetaceans (Basilosaurus, Livyatan, undetermined balaenopterids and cetotherids from Miocene and Pliocene) and very large sharks (Carcharocles megalodon), all of them likely reaching or exceeding 15 m. So we have indications of such large behemoths but nothing certainly reaching or exceeding 15 m in pliosaurs.

Sampling bias ? Not sure.

Adam Smith, you're investigating the central fusion of pliosaurs. At this stage do you still think plausible the Aramberri pliosaur could have been a young individual like suggested in its initial description ?
If true this could put some weights to the speculations of Frey and Stinnesbeck about the likelihood of much larger pliosaurs in the area at the time.

[stargatedalek]

Who's to say this wasn't a very specialized Pliosaur, with unusually large teeth. Speculation can take us anywhere remember, that's its beauty

[DinoToyForum]

Just being devil's advocate here, but couldn't preservation bias play a role, and with marine environments be taken to the extreme? There are parts of the prehistoric oceans that have been oceans throughout their history. Could smaller species and juveniles been living relatively closer to shore while truly massive pliosaurs been living far, far, far offshore? So far that when they died there's no hope of paleontologists ever even learning of their existence because any and all fossils are miles beneath the ocean surface and that's why there's only rumored fused verts?

This is something I've always wondered. Pliosaurs and other marine species aren't really something I'm particularly well versed in though, so if I'm wrong, sorry.

This could be applied to any kind of extinct large organism. But we already have found specimens of very large ichthyosaurs (Shonisaurus, Shastasaurus, Temnodontosaurus...), very large cetaceans (Basilosaurus, Livyatan, undetermined balaenopterids and cetotherids from Miocene and Pliocene) and very large sharks (Carcharocles megalodon), all of them likely reaching or exceeding 15 m. So we have indications of such large behemoths but nothing certainly reaching or exceeding 15 m in pliosaurs.

Sampling bias ? Not sure.

Adam Smith, you're investigating the central fusion of pliosaurs. At this stage do you still think plausible the Aramberri pliosaur could have been a young individual like suggested in its initial description ?
If true this could put some weights to the speculations of Frey and Stinnesbeck about the likelihood of much larger pliosaurs in the area at the time.

Because my research is ongoing I don't want to talk about it too much. All I'll say is that paedomorphism is an alternative explanation for large 'immature' bones, and different parts of the skeleton, even different parts of the vertebral column, mature at different rates.

[Komodo]

So far, no example of fused neural arches in pliosaurs ?

[Komodo]

I quote here the analysis on FB of Max Hawthorne about a recently found Liopleurodon skull.

Putting his obvious fanboyism apart I'm curious to see your comments about this.

"MAX HAWTHORNE PLIOSAUR UPDATE



This rare skull of a juvenile Liopleurodon ferox was discovered in the Oxford Clays off of Petersborough and was recently put on auction. The skull measured around 43" and was partially intact. 

What is excellent about this particular piece is what can be deduced from it. Of particular use is the tooth laying directly behind the exposed eye orbit (just right of center). This is a complete tooth, root and crown. 

The tooth's positioning is fortuitous, as it enables us to do some quick calculating. The tooth measures approximately 1/8th of the skull's complete length. With this hard evidence in hand, we can use it as a starting point and then scale up using other fossil material.

For example, there are several teeth in the LMNH measuring 16" in length (400 mm). By multiplying the size of that tooth times 8 (tooth to skull length ratio) we can infer that the entire skull of that animal measured around 128" or 10 feet 8 inches (3.26 meters for those favoring metrics).

Liopleurodon was a Jurassic Thalassophonean, and as such, typically had a skull measuring 1/6 to 1/7 of its entire length. At 1/6 ratios, this would indicate the owners of these 16" teeth measured somewhere around 64 feet, or close to 20 meters. 

Interestingly, paleontologist/plesiosaur expert Richard Forrest has calculated on his web site (http://plesiosaur.com/other/general.php#largest) that the owners of some of the giant pliosaur teeth, mandible, and vertebrae they have in storage, indicate an animal around 21 meters in length.

My conclusion is that Richard is 100% right in his calculations. and I stand by my figures. At 64 feet (and around 80 tons), these animals may not have been the biggest pliosaurs, but they were monstrous beasts nonetheless. Slowly but surely, proof is coming to light that shows these scaly macropredators were both the most massive and the deadliest marine predators of all time. 

At least, so far "

Is it a valuable insight or just an attempt pliosaurs the biggest and baddest ?