Top Dog

[blaze]

If the guy has a hand similar in size to mine, the tooth is ~24cm long as preserved with a crown (I think) of ~12cm, could this be the first photos of the infamous 30cm teeth?

[coherentsheaf]

Whats your guess for width?

[blaze]

Shy of 6cm at the base of crown.

[Grey]

If the crown is 12 cm, the complete tooth could be 36 cm.

There are larger ones in their collection.

[blaze]

Yeah, I compared it with the Liopleurodon teeth drawings in Andres (1913) and got a total length including root of about 33cm, 36cm doesn't seem bad if measured following the curves rather than in an straight line.

[Grey]

I m not sure though if part of the crown isn't eroded as well. The curvature of the alleged root part makes me wonder if the crown wasn't a bit larger than 12 cm.

Also, was it systematically the largest tooth in the dentition...

[Grey]

I've done some additionnal research tonight. I don't say than further information won't say otherwise (as often in paleo research) but I think our best evidence for a 20 m plio remains the Peterborough vertebra. The points about them are listed below :

- actually there are two of these huge vertebra ( Martill said me) and Richard reports three of them on his website. Leslie Noé said me he has seen similar sized specimens in private collections.

- only one of them has been studied and is reported in the paleo litterature.

- it was for years identified as a sauropod vertebra, painted in blue (!) and used as a doorstop in its Museum (!!!).

- in 1996, McHenry, Noé, Arthur Cruickshank (deceased since) and Martill reidentified it as a pliosaur vertebra and estimated that based on the 13 m Harvard Kronosaurus it suggested a 17-20 m pliosaur.

- it is exactly 252 mm in diameter.

- since, there has been uncertainties about its identity. McHenry revised his opinion and thinks it's from a sauropod after all.

- Noé, Martill and Cruickshank were mostly of the opinion it was a pliosaurid, and McHenry said he leaves the exact identification to anyone else more familiar with Jurassic England sauropods/pliosaurs vertebra.

- because of this, I think they most likely are pliosaurids.

- even if it is from a pliosaur, McHenry estimated the size of the pliosaur in his thesis about 12-14 m, based on his revised size estimate for Kronosaurus.

- however, the largest vertebra in Kronosaurus are cervicals, while in the Jurassic pliosaurs they are thoracic, and these isolated vertebra are apparently thoracic.

- also, the ratio skull/body size in Kronosaurus is 1/4-1/5 while it is 1/6 in Jurassic pliosaurs (Noé, pers. comm)

- so, I suggest that using Kronosaurus as proxy is probably less valid.

- also as said earlier, there is still the (less likely) possibility that Kronosaurus may have been 13 m after all rather than 11 m.

- one of the problem while scaling large animals from isolated body parts is the allometry factor. Larger animals don't have the same body proportions than smaller ones. As fr example, the skull grows proportionnally larger in the largest crocodiles than in the smaller individuals. This potentially complicates estimates based on skull fragments.

- however, I've seen McHenry mentionning that isolated vertebra might be a more reliable indicator of size than skull parts because they're not subject to allometry.

- thus, using this isolated vertebra from even a much smaller related pliosaur might be less problematic than using other body parts.

- using the data based on the Tübingen Liopleurodon skeleton, assuming it might have been actually 5.5-5.6 m (as suggested by its skull length about 94 cm) and using its 70 mm wide vertebra, this suggests the Peterborough pliosaur at 19.8-20.2 m.

- I ignore the size of the other vertebra. IIRC, they were stated to be 40-50 % larger than Kronosaurus. I can't claim anything but this would mean one of them was about 270 mm in diameter.

- 270 mm in diameter is the max known in the ichthyosaur S. sikanniensis, measuring 21 m. Ichthyosaurs and pliosaurs are certainly very different but incidentally could there be a similar vertebral width between them at the same length ? I need to verify this. I also need to confirm if vertebral based measurements are really less or not affected by allometry.

Of course, all of this is from an educated research of mine, but I can't claim it is absolutely certain. But from the data I've gathered, I think this is objective, I don't count only the hits.

Given their scanty nature of this and the fact that even specialists are not necessarilly aware of all the updated data about this material and research, I think it will be difficult to get a conclusion.
But after all, Dave Martill is quite affirmative about this.
And of course, if only one of these pliosaurs that we have remains from was about 20 m, it is difficult to argue it was systematically the largest of the species...

[Grey]

Regarding the big Liopleurodon tooth posted earlier, the length in straight line is 22.5 cm and the crown height is 13.1 cm. The crown base indicates a size similar to an alveoli they measured in kevani, 51 mm. They estimate it came from an approx. 12 m Liopleurodon. It is growing. It seems like crown measurements are more usefull than the whole tooth measurement.

[blaze]

I think we have ignored some interesting data from Andrews (1913). First the largest tooth preserved with the largest skull, crown height 75mm, crown base width 30mm, based on the measurements above given by Grey the giant tooth is 75% taller and 70% wider, assuming isometry and a 1.6 ratio (which I'm still not convinced about) it suggest a total body length of ~13m. However we have to keep in mind comparisons with other specimens like R2680 whose largest tooth has a crown 85mm in height and its base is 28mm, the giant one then is 54% taller and 82% wider, following the same procedure as above it suggest a total length of 10-12m not to mention that if this tooth is comparable to those from P. kevani which has an skull with a CBL of 180cm then we could be looking at a max a little below 11m even assuming the 1:6 ratio.

Furthermore there are vertebral measurements of the same specimen as the largest skull, there's only measurements of 7 with the two widest being the 17th and 23rd, listed as cervical and pectoral, at 128mm and 125mm, respectively. They are probably not the largest the animal had and yet they are over a third wider than would be expected from isometry when compared to the Tubigen specimen. I think this is important for the Peterborough vertebrae, the centrum width of Jurassic pliosaurs appears to grow allometrically with ontogeny/ body size thus using isometric scaling to estimate their sizes based on this measurement appears misleading.

[Grey]

I have to precise this estimate is from one of the authors of the P. kevani description. I think the estimate derived from this tooth is only approximative and just based on the P. kevani skull. They couldn't suggest what was the size of the complete tooth. It is well possible that root length is more subject to variability and that crown measurements themselves are (slightly) more reliable. They also conservatively assumed the tooth was the largest in the dentition. But it is well possible it wasn't the case. I certainly agree though that teeth based measurements are certainly problematic but this approx. figure compared with kevani seems pretty good to me. Liopleurodon is suspected to have exceeded 10 m since a long anyway.

P. kevani CBL isn't rather 2.1 m ? I've always wondered why the initial measurements reported it at 2.4 m.

I'm skeptical that scaling vertebra measurements would be allometric, McHenry suggests otherwise, at least less subject than skull based estimates. The fact the two specimens by Andrews have very few vertebra explains why the body size estimates were extrapolated from skull length. But based on what Noé repeatedly stated about the skull size ratio, I think the published sizes estimates for these specimens are significant (or very conservative) underestimates.

I'm pretty certain that the skull/body ratio for Jurassic pliosaurs is nearer to 1.6 than 1.5 given that the Tübingen skeleton is obviously not complete.

If that's true, it can be noted that the sizes estimates for P. funkei, a Jurassic Pliosaurus based on Kronosaurus vertebra could as well suggest underestimates. The larger individual is estimated to have a skull 2-2.5 m. If Noé is right, this suggests "Predator X" in the 12-15 m range.

I clearly need some confirmation about that, but I definitely have my doubts about 1.5 ratio for Jurassic pliosaurs, unless treated as pretty conservative figures.
Even doubting this, are really vertebral measurements from Kronosaurus a really good proxy for P. funkei or any other L.J. pliosaurids ?

[blaze]

It has been suspected to exceed 10m based on pretty much hearsay and erroneous assumptions (the 1.7 ratio), this is somewhat of a revival (if they are indeed Liopleurodon) but is still all unpublished.

The skull of P. kevani is ~2.03m in greatest length, premaxilla to quadrate, the condylobasal length is shy of 180cm based on the photos in the paper.

The comparison I made between R3536 and the tubigen specimen was not based on published total length estimates but on the CBL of their skulls, that of R3536 is 35% greater, but the difference in their vertebral width is up to 83% and this is comparing cervical vs pectoral, and since the later are supposedly bigger then this a lower bound.

[Grey]

That's odd since initial measurements of the skull were about 2.4 m.

Interestingly, estimating TL using the largest R3536 vertebra from the Tübingen specimen vertebra, you get 10.05 m TL.

Frankly there is something strange. I've compared the 128 mm cervical centra of R3536 with a cervical centra of PMO 214.136 (Predator X) measuring 172.5 mm wide (figure 16 of Knutsen et al). I don't think it is the largest vertebra in the specimen but I doubt the largest in it are much larger as Pliosaurus funkei max vertebral width is anyway smaller than in the Aramberri pliosaur (200 mm).

If you consider R3536 as 6.39 m, using this vertebral comparison "Predator X" would be only 8.6 m.
If using the 1/6 skull ration for R3536, so 7.56 m, you get 10.18 m for Predator X which is still an underestimate considering the upper size proposed by Knutsen et al. (and even more if PMO 214.136 indeed needs a 1/6 skull ratio).

If you consider R3536 is 10 m long, then you get 13.5 m for Predator X, about only 0.5 m over its upper size proposed in Knusten et al.

If one can identify the largest vertebra measurement in PMO 214.136, this calculation can be tweaked.

Using vertebral measurements thus is certainly problematic but I really think that the usual 6.39 m figure is a big underestimate for R3536, because this yeilds big underestimates for the larger P. funkei (itself based on Kronosaurus data).

I'm gonna ask to Noé. But I think there's a good reason if Buchy mainly used the uncatalogued but more complete Tübingen skeleton rather than Andrew's data for estimating Aramberri. It is noteworthy that all the body parts of Aramberri suggest 15 m or more based on the Tübingen, not only the vertebra.

[theropod]

The skull of Pliosaurus kevani is very large, measuring 1995 mm
along the dorsal midline of the cranium and with a mandibular
ramus length of 2045 mm excluding the retroarticular process.

Benson, Roger B. J.; Evans, Mark; Smith, Adam S.; Sassoon, Judyth; Moore-Faye, Scott; Ketchum, Hilary F.; Forrest, Richard: A Giant Pliosaurid Skull from the Late Jurassic of England. PLoS ONE, Vol. 8 (2013); 5; pp. 1-34

Note how the occipital condyle is significantly more anterior than the posterior edge of the skull at the midline, that’s where the different measurements come from. But dorsally measured skull lenght in P. kevani is very close to 2m. 2.4m though, it would appear, are just another one of those laughable media fabrications.

[coherentsheaf]

Vertebral widt of PMO 214.316

156mm 160mm 180mm 220mm

All cervicals. Note these are smaller than in MCZ1285. MCZ1285 has larger cervicals than dorsals. PMO 214.315 has similar dorsals to cervicals.

[blaze]

^See, 220/128*6.39= 10.98m.

That also works when you compare their vertebral lengths, Liopleurodon and P. funkei have similar centrum width/length ratios of their cervicals, between 2.5 and 2.8, for comparison the ratio in MCZ 1285is 1.8-2 but in K. boyacensis it is 2.4-3.4, the two Kronosaurus specimens are similar in size when total length is concerned and yet it appears one has shorter and wider cervicals than the other.

Either way remember that Knutsen et al (2012) estimated an skull length possibly as low as 2m for PMO 214.316 (according to Benson et al 2013, their cervical centra and occipital condyle equations gave 2.04m and 2.19m respectively, I suppose the 2.5m comes from the limbs) this is consistent with the measurements of the occipital condyle: 105mm high and 150mm wide vs 107mm and 104mm in P. kevani and 125mm and 180mm in MCZ 1285 and although the width of that of P. kevani is odd, overall it indicates an skull smaller than in MCZ 1285 by 25%, since the later is about 2.3m (McHenry, 2009) this results in an skull length of ~184cm, almost the same as in P. kevani (!).


This reminds me a bit to the supersized Spinosaurus of a while ago, 20t (13m) pliosaurids with heads a full half a meter shorter than in pliosaurids half their weight? why not?