The most powerful and fearsome predatory reptile of all time

[coherentsheaf]

Jun 6, 2013 1:44:49 GMT 5 theropod said:

13m is a conservative estimate, and a very speculative one since nobody knows how much of that mandible is reconstructed. 15m is a plausible size for some of the largest pliosaurs (Buchy gave this as "at least 15m", furthermore estimating the mandible at 3m, and noting both P. macromerus and a "recent description from the Kimmeridge bay" also attaining this size. The femoral head suggests 16m)

The vertebral remains of the MoA are larger than P.funkei and Kronosaurus but ot by much. I think the 12m 15tonne estimate by McHenry is plausible.

[Grey]

Jun 6, 2013 1:44:49 GMT 5 theropod said:

13m is a conservative estimate, and a very speculative one since nobody knows how much of that mandible is reconstructed. 15m is a plausible size for some of the largest pliosaurs (Buchy gave this as "at least 15m", furthermore estimating the mandible at 3m, and noting both P. macromerus and a "recent description from the Kimmeridge bay" also attaining this size. The femoral head suggests 16m)

You did no read the passionnating thesis Theropod ?

12,7 m is no conservative but a mean estimate. Based on the vertebras measurements, he found that the MoA was smaller than the Cumnor Pliosaurus, though a very large pliosaur by any standard. Coherentsheaf already suspected this.

In terms of size, MoA is interesting but I believe in McHenry works which re the most advanced and up to date. Only, the possibiity remains that the animal itself was not fully grown, though this is not well supported neither by Buchy and McHenry.

15 m for pliosaurs is highly possible, but not confirmed, neither in Cumnor, MoA, and Svalbard, despite the initial claims. P. kevani was in the first reports even reported at 18 m...


It seems that experts do not rule out the hypothesis that some mosasaurs could have been larger and fiercer than the pliosaurs. I would not rule out these guys strictly.

[Venomous Dragon]

I feel this should have terrestrial and aquatic catagory.

[Fragillimus335]

Jun 6, 2013 1:47:22 GMT 5 Grey said:

The thesis of McHenry is several hundreds of pages, nowhere he alludes to some cartilage adding significant body length.
No self-science here...

No blind ignorance either please. All animals have cartilage, and aquatic animals seem to have a ton of it.

[Grey]

Jun 6, 2013 4:04:07 GMT 5 Fragillimus335 said:

Jun 6, 2013 1:47:22 GMT 5 Grey said:

The thesis of McHenry is several hundreds of pages, nowhere he alludes to some cartilage adding significant body length.
No self-science here...

No blind ignorance either please. All animals have cartilage, and aquatic animals seem to have a ton of it.

And nobody has speculated to overgrown these animals based on this. Read McHenry's doctorial thesis if you want learn the pliosaur's size question.

[creature386]

Jun 6, 2013 1:15:40 GMT 5 Fragillimus335 said:

but with crocodile-like cartilage the 12.7 meter estimate would become ~14+ meters.

This is a valid hypothesis, but we have no idea on the size of the cartilage, so it is the best to ignore it, until we know more.

[theropod]

Based on the vertebras measurements, he found that the MoA was smaller than the Cumnor Pliosaurus

But the Cumnor Pliosaurus is merely an incomplete mandible, it doesn't include vertebrae.

I would like to point out what McHenry actually writes:

In many ways, pliosaurs were the Mesozoic equivalent of modern toothed whales,
matching odontocetes in the range of body sizes (from 2 metres for the smallest to
15-18 metres for the largest) and geographical distribution, but greatly exceeding the
30 million years that toothed whales have managed so far.

The question was not that much whether MoA or P. macromerus are bigger, both are very big, but the size estimate is far from certain and rather low.

Another interesting thing:

Figure 1-2: The teeth of ‘Pliosaurus grandis, as figured by Owen (1869). The tooth was figured
at actual size – a length of 33cms, although 2/3 of this is the root. Presuming that this was
the largest tooth in the maxillary row, the minimum length of the animal would have been
~10 metres – slightly longer than large modern killer whale.

The 45cm specimen is at least 36% bigger (the size figure assumes it to be the largest tooth).

Pliosaurus in general seems to have been a really huge pliosaur, bigger than Liopleurodon.

And another thing, he mentions a 1,8m Liopleurodon skull, that's likely were the 9-10m come from.

McHenry et al. 19961 reidentified an isolated vertebra (PETMG R272 – previously
identified as from a sauropod dinosaur) from the Oxford Clay near Peterborough as
a pliosaur cervical vertebra: by comparison with the Harvard Kronosaurus mount, they
estimated the length at between 15-18 m. However, the assumption of accuracy in
the Harvard mount (see below), and the identity of the Peterborough vertebra, have
been questioned (A. Cruickshank, pers. comm.): the vertebra may well belong to a
sauropod after all, although consensus has not been reached on this matter (D.
Naish, pers. comm.).

I think there are pliosaurs topping the 15m.

[theropod]

My point about mosasaurs was that while comparable in lenght, they are mostly much more slender, and have smaller, less massive skulls.

[Grey]

I would like to point out what McHenry actually writes:
In many ways, pliosaurs were the Mesozoic equivalent of modern toothed whales,
matching odontocetes in the range of body sizes (from 2 metres for the smallest to
15-18 metres for the largest) and geographical distribution, but greatly exceeding the
30 million years that toothed whales have managed so far.


The question was not that much whether MoA or P. macromerus are bigger, both are very big, but the size estimate is far from certain and rather low.

By that, he does not mean that pliosaurs reached 15-18 m, he explains that these animals matched the size range of odontocetes (refer yourself to the part about the impact of size in historical oceanic predators). The sizes estimates are the most up to date and the most rigorous to now. Nowhere, they can be seen as "low" (I don't understand why you suggest this), as they are for most mean estimates between more conservatives and more liberal.


I think too that pliosaurs could have reached 15 m, but there are no conclusive evidences to now. 12,7 m for P. macromerus is the largest rigorously estimated size in pliosaurids in recent years.

The pattern of variation of body size across a taxonomic group should preferably be based upon more complete specimens that include substantial portions of the cranial and/or post-cranial skeleton, and the currently known extent of this range for large pliosaurid and brachaucheniid pliosaurs is shown in Figure 6-22. These show that the largest pliosaur specimen known from non-fragmentary remains is OUMJ.10454 (the ‘Cumnor mandible’), currently referred to Pliosaurus macromerus (Noè et al. 2004), which is here estimated (by comparison with the BMNH model) to have been 12.7 m in Total Length, with a body mass of 19.2 tonnes. Of the estimates for fragmentary specimens given above, this size is exceeded only by taking the maximum estimates calculated for PETMG R272 and the ‘NHM symphysis’, although as discussed below those maximum estimates are of doubtful validity. The Aramberri specimen is estimated to be a smaller individual than the Cumnor specimen, even using a maximal estimate of size in the former for comparison.


"Mega-pliosaurs?

Prior to the present analysis, the largest published length for a pliosaur known from substantial remains was Romer and Lewis’ figure of 12.8 metres for the MCZ specimen of Kronosaurus (Romer and Lewis 1959). Even though the reconstructed length of this specimen has herein been reduced to 10.5–10.9 metres, the Cumnor mandible represents an animal of a similar length to Romer and Lewis’s reported figure and 12–13 m can be considered as the upper range of body size that can be reconstructed on the basis of substantially complete cranial or post-cranial remains. As has been mentioned above, there has recently been speculation that some fragmentary fossils from the Middle–Late Jurassic may represent pliosaurs that exceeded have 12.8 metres in length, here termed ‘mega-pliosaurs’15. Coincidentally, under the BMNH model, this total length corresponds with a body mass of almost exactly 20 tonnes.
Potential mega-pliosaurs are stratigraphically limited from the Callovian to the Tithonian. Five are discussed here; the Aramberri specimen, the Peterborough vertebrae, the NHM symphysis, the holotype of Megalneusaurus rex, and the recently discovered Svalbard material.

The Aramberri specimen (Kimmeridgian) preserves a series of posterior cervical to pectoral vertebrae and a propodial head, and is unquestionably pliosauroid; on the basis of the sub-central foramina preserved on the vertebrae it can be excluded from the Brachaucheniidae and is most likely a pliosaurid. It is certainly large: the dimensions given by Buchy et al. (2003) for the vertebrae reconstructed here as the first dorsal exceed the comparable dimensions of the Kronosaurus specimens examined in the present work. For a specimen such as the Aramberri material, however, there are two significant problems; (1) known pliosaurid specimens that could potentially serve as an anatomical template for size estimates are significantly smaller than the Aramberri specimen (the problems with extrapolation of body size over orders of magnitude are considered above); (2) the only fossils that can serve as useful templates, and which are from specimens not too much smaller than the Aramberri specimen, i.e., Kronosaurus, are from a family known to have different vertebral proportions to pliosaurids. On the basis of reported vertebral length, the Aramberri specimen is smaller than the large Kronosaurus specimens; however, the vertebral width and height of the Aramberri specimen are considerably greater than in any of the Kronosaurus specimens, and scaling by these produces size estimates of 11.7–12.2 metres total. Accepting that, between species with different vertebral counts, comparing the diameter of individual vertebrae produces more reliable estimates than comparing vertebral length (see above), the Aramberri specimen therefore seems to represent a very large pliosaur, but not one that is larger than the more reliable size estimate for the Cumnor mandible. The status of the Aramberri specimen as a ‘mega-pliosaur’ is thus subject to question.
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.

Unlike the Aramberri specimen, the Peterborough vertebra (Callovian) may not represent a pliosaur: the overall shape of the centrum is consistent with that of a pliosaur cervical, but the sub-central foramena and the costal facets are of a divergent morphology to the typical state in pliosaurids. It is, however, a very large element, exceeding the Aramberri specimen in diameter, and as pectoral/ anterior dorsals are always larger than cervicals from the same animal, if it is a pliosaur it is undoubtedly from a larger animal than the Aramberri specimen. Exactly how much larger is uncertain – unlike the Aramberri specimen, an isolated pliosaur cervical vertebra is very difficult to place accurately in the cervical series and, cervical vertebrae vary more than do those of the pectoral region. Comparison with the width of anterior cervical vertebrae of Kronosaurus suggest a size of 11.6–14.2 metres (14.6–26.7 tonnes), with a mean estimate of 12.6 metres and 18.8 tonnes. If the Peterborough vertebrae is a pliosaur, it might thus (taking the maximal estimate) represent a true mega-pliosaur (i.e. > 20 tonnes). However, the identification of this fossil remains in dispute; it is considered here to be, on balance, too likely to be a sauropod to warrant status as a confirmed mega-pliosaur.

The NMH symphysis (Callovian) is certainly more pliosauroid, but there is little information other than been collected from the Oxford Clay. It is of the ‘short symphysis’ type (Noè 2001, Noè et al. 2004, Tarlo 1960) but beyond that its taxonomy is difficult. The marine fauna from the host unit, the Oxford Clay, is perhaps the best studied of any worldwide: if the NHM symphysis represents a large individual from a species already described from the Oxford Clay, present knowledge suggests either Simolestes vorax of Liopleurodon ferox. Of the other pliosaurs known from that fauna, Peloneustes has a much longer symphysis, while symphyseal length in Pachycostasaurus dawni is unknown (Noè 2001). Alternatively, the NMH mandible indicates a ‘short’ symphysis species known thus far from different strata, such as the Kimmeridgian Pliosaurus macromerus. All of these candidate species can be distinguished on the basis of the ornament and morphology of the tooth crowns, but no teeth are preserved with the NHM symphysis. For ‘short symphysis’ extant crocodilians, symphyseal tooth counts are consistent within species for individuals across all size classes (pers. obs.), indicating that this feature does not vary ontogenetically. Symphyseal tooth count is considered to be a robust taxonomic character in pliosaurs (Noè et al. 2004): by this criterion, NMH mandible is perhaps therefore more likely to represent Simolestes vorax than Liopleurodon ferox or P. macromerus, although Pachycostasaurus remains a logical possibility.

However, the proportions of the symphysis are somewhat different to that of Simolestes, or indeed of any other pliosaur known from the Callovian-Kimmeridgian. In addition to being absolutely large, the NHM symphysis is massive: for its length, it is very robust. The ‘macrocephalic’ growth pattern seen in some modern crocodilians and turtles has not, as yet, been documented in pliosaurs, but the NHM symphysis suggests that very large individuals may have shared this growth pattern. Assuming, that this is the case, we should expect to see that the proportions of the symphysis are relatively wider in a macrocephalic adult, compared with a smaller individual of the same species. By this logic, the NHM symphysis could possibly be Liopleurodon ferox or Pliosaurus macromerus, but not Simolestes vorax. Conversely, if symphyseal tooth counts are taxonomically robust, then the NHM symphysis is neither L. ferox or P. macromerus. It appears on balance to represent a different taxon to any of these.

Most large pliosaurs have head proportions broadly similar to Liopleurodon or Pliosaurus. Assuming that the NHM symphysis is from a macrocephalic adult of a similarly proportioned taxon, and that, in macrocephalic specimens, body length will correlate with jaw length (or part thereof), rather than jaw width or height, the best estimate for body size in this taxon is that based on comparison with symphyseal length in Liopleurodon, i.e. a TL of 9.1 m and a body mass of 7.1 tonnes. However, in macrocephalic individuals, overall girth of the body may increase for little or no proportional increase in length, and this weight estimate is likely to be conservative. The estimate based upon mandible width in Liopleurodon can be excluded as a logical possibility; the mean of the remaining estimates is 10.8 m TL and 14 tonnes body mass.

As shown above, the Stretham (Kimmeridgian) and Stewartby (Callovian) specimens each represent animals similar in size to large Kronosaurus, underlining the consistency of the 10 – 11 m range of total length as the upper limit for most well preserved pliosaurs in the Middle – Late Jurassic and the Early Cretaceous. The holotype of Megalneusaurus rex (Oxfordian) comprises a series of vertebrae and limb elements: the propodial is reconstructed as 990 mm long, slightly larger than any propodial known from Kronosaurus and larger than the femur of the Stretham specimen (and, probably, the Stewartby specimen). The allometry of pliosaur propodials is not sufficiently known to allow quantitative estimates of body size; qualitative estimates of size in M. rex depend upon whether the propodial is a humerus or a femur. If a femur, it is a large pliosaur, possibly 11–12 m TL or slightly larger. If a humerus, it is a very large pliosaur, perhaps the largest known. However, the vertebral dimensions described by (Knight 1895) are not obviously larger than those of Kronosaurus: in all likelihood, the propodial is a femur and Megalneusaurus rex is a pliosaur slightly larger than the largest Kronosaurus and the Stewartby and Stretham pliosaurs. The same logic applies to size estimates based upon early reports of the Svalbard pliosaur (Tithonian – P. Druckenmiller, pers. comm.).

There seems, therefore, to be no strong evidence for pliosaurs that exceeded 20 tonnes. Of the specimens considered above, the only possibility for a pliosaur longer than 12.8 m is the Peterborough vertebrae, and that by taking the upper estimate of size for the specimen. The doubtful taxonomic assignment of this specimen casts further doubt on that specimen. There is, however, convincing evidence for pliosaurs in the 10–20 tonne size range; not only from the fragmentary material claimed to indicate mega-pliosaurs, but the more reliable Cumnor mandible as well, and the larger specimens of Kronosaurus are at the lower end of this scale. Historically, Kronosaurus has been the benchmark for body size in large pliosaurs. Between the original and revised lengths of body size in Kronosaurus (12.8–10.8 m respectively), there is a potential size class for pliosaurs that may have been very large, i.e. between 10 and 20 tonnes. From the evidence available to date, it appears that mega-pliosaurs remain a myth, but that very large pliosaurs were a reality."

[theropod]

2-18m is not the size range of odontocetes, that would be 1,5-20,5m. I think he is taking a cautious approach, nothing wrong with that, but that doesn't mean the sizes were necessarily that limited.

[creature386]

Jun 7, 2013 1:11:15 GMT 5 theropod said:

2-18m is not the size range of odontocetes, that would be 1,5-20,5m.

Only if the 20,5 m Sperm Whale is no freak.

[coherentsheaf]

Jun 6, 2013 23:21:56 GMT 5 theropod said:

I think there are pliosaurs topping the 15m.

I think no material we have indicates pliosaurs in this size range.

[Grey]

Jun 7, 2013 1:11:15 GMT 5 theropod said:

2-18m is not the size range of odontocetes, that would be 1,5-20,5m. I think he is taking a cautious approach, nothing wrong with that, but that doesn't mean the sizes were necessarily that limited.

This takes all the global range, no need to focuse on this 20,5 m mention. The clssical size figure for the sperm wale is 18,3 m (Lambert).

Anyway, there's no evidences at now for pliosaurs bigger than macromerus.

There are evidences of several pliosaurids that were in the 10-20 tons range. There are no evidences for "mega-pliosaurs", understand pliosaurs exceeding 20 tons.

I think people tend to always envision extraordinary numbers and don't realize what 20 tons would represent in a 13 m predatory sea reptile. That's two to three times the mass of a T. rex in a body of similar length, packed with larger and more powerful jaws. No need to undermine a guy like this.

[Grey]

Regarding the mosasaurs, here are quotes from McHenry :

By comparison of TL with modern crocodilians, the largest mosasaurs Tylosaurus and Mosasaurus (Late Cretaceous) may have weighed up to 30 tonnes, although given the likely ‘eel-like’ body form of these taxa this must be considered a maximum estimate and a range of 10–15 tonnes is perhaps more likely.

Modern marine carnivores never exceed 10 tonnes. Given that a similar patterns holds – with the notable exception of Carcharocles – for fossil marine ecosystems in the Cenozoic and most of the Mesozoic, it may be that 10 tonnes is close to the upper limit of body size that is viable for marine carnivores.(This interpretation depends on the assumption that Basilosaurus and the largest mosasaurs, such as Tylosaurus and Mosasaurus, are not significantly larger than 10 tonnes. Although these taxa are much longer than any pliosaur, they have a highly elongate body form and their mass, in proportion to body length, is likely to be even lower than in balaenopterids or crocodilians. Any further work on the macroevolutionary patterns outlined here will need more reliable estimates of body shape in these taxa. Even if they do exceed 10 tonnes, the implications of their elongate form for locomotor mechanics may preclude them from the ecomorphs occupied by pliosaurs and lamnids.)

All of the large other pliosaur specimens known thus far represent animals close to 10 tonnes or less: this body size as been a remarkably consistent upper limit for marine carnivores since the Middle Triassic, breached only by the Miocene lamnid shark Carcharocles megalodon and possibly, depending on further refinements of body size estimates, Basilosaurus and the largest mosasaurs.

Note : he only notes the Miocene Carcharocles being the only exceeding this size range as the Miocene Livyatan was not yet described. It seems that both of these predators may have exceeded that mark due to their specific evolution in the Miocene marine communities and the rise of the baleen whales. Physeter is not counted, as a teutophagous predator.

But my point is that it is possible that the largest mosasaurs may have rivaled some of the largest pliosaurs in size and especially ferociousness. We have to remember these guys successfully outclassed the mighty large lamniforms, something the last pliosaurs failed to perform. Some will say this is not strictly related to the strength of the animals, I say this is not only for other reasons. Mosasaurs were true monsters, some bulkier than we thought and armed with powerful jaws. Something like a large Prognathodon would be a match for some of the very large pliosaurs IMO.

[theropod]

Keep in mind the skull of Prognathodon measured 1,4m, about the same as that of T. rex. The largest plisoaur-skulls are 2m+
I don't think concerning the formidable killing apparatus prognathodon can rival the largest pliosaurs.

Also, the weight figure obviously bases on very high lenght estimates, as the only way an upscaled crocodile would approach 30t is by being 18m+ in lenght. I have tried to relocate the notes on Oceans of Kansas, but failed to find what I had previously read about mosasaurs exceeding 15m.

Of course pliosaurs are far bulkier than theropods. However a 13m pliosaur even at the same proportions would be more than 18% heavier than T. rex. These guys are larger than theropods in every regard.