Kronosaurus queenslandicus vs. Cardabiodon ricki

[Infinity Blade]

Kronosaurus queenslandicus

Kronosaurus (/?kr?no??s?r?s/ kron-o-sawr-?s; meaning "lizard of Kronos") is an extinct genus of short-necked pliosaur. It was among the largest pliosaurs, and is named after the leader of the Greek Titans, Cronus. It lived in the Early Cretaceous Period (Aptian-Albian). Like other pliosaurs, Kronosaurus was a marine reptile. It had an elongated head, a short neck, a stiff body propelled by four flippers, and a relatively short tail. The posterior flippers were larger than the anterior. Kronosaurus was carnivorous, and had many long, sharp, conical teeth. Current estimates put Kronosaurus at around 9–10 meters (30–33 feet) in length. All Sauropterygians had a modified pectoral girdle that supported a powerful swimming stroke. Kronosaurus and other plesiosaurs/pliosaurs had a similarly adapted pelvic girdle, allowing them to push hard against the water with all four flippers. Between its two limb girdles was a massive mesh of gastralia (belly ribs) that provided additional strength and support. The strength of the limb girdles, combined with evidence of large, powerful swimming muscles, indicates that Kronosaurus was likely a fast, active swimmer. Body-length estimates, largely based on the 1959 Harvard reconstruction, had previously put the total length of Kronosaurus at 12.8 meters (43 feet). However, a recent study comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the Harvard reconstruction may have included too many vertebrae, exaggerating the previous estimate, with the true length probably only 9–10 meters (30–33 feet).


© @ puntotu

Cardabiodon ricki

Cardabiodon is an extinct genus of lamniform shark which existed in Australia, Canada, and Europe during the Cretaceous period. It was first named by Michael Siverson in 1999, and contains the species Cardabiodon ricki.

[Grey]

From Mike S. Western Australian Museum.

The giant pliosaurs of the late Early Cretaceous were replaced by giant lamniform sharks (cardabiodontids), letÂ’s put it that way. The earliest evidence we have of lamniform sharks reaching a size exceeding that of the modern white shark is in the earliest part of the late Albian. Obviously the giant pliosaurs, such as Kronosaurus, were not able to prevent the rise of these selachian giants. This situation is in stark contrast to the rise of the tylosaurine mosasaurs.



The cardabiodontids were not only reaching a considerable adult total length (probably closer to 9 metres in the Albian) they were also most likely stocky in their build (indicated by the morphology of the vertebral centra), even more so than a white shark of comparable length.



At a total length of 9 m they would have weighed about 6 metric tonnes if they had a girth similar to that of modern Lamna. At that size they were probably well beyond the upper prey-size range of adult Kronosaurus. They may simply have been more efficient at catching the same prey and thereby contributing to the demise of the giant pliosaurs.

[Infinity Blade]

Yep, I give Cardabiodon very high chances in this fight. I think you (Grey) also said once that outcompeting another animal has a partial link to physical ability.

[Grey]

Yes, unless the rising competitor has other evolutionnary advantages like pack hunting which was likely not the case in Cardabiodon. I know that Mike Everhart (and Siversson) suggested that the tylosaurines and mosasaurines outcompeted the sharks because mosasaurs had better reproduction skills and were able to grow larger way faster than the sharks, which explains their ultimate supremacy.
On the other hand, I don't think that Cardabiodon was more effective at reproducing or growing faster than Kronosaurus(large lamniforms have never been champions in terms of reproduction, that's their main problem today). I think that the superior ability to catch prey, in a predator similar in size to another with no other proeminent skills, is partially hinting the physical ability in an interspecific contest. That is debatable of course but if Kronosaurus had been physically superior to its solitary-living competitor, I don't think it would have been so clearly removed from the Early cretaceous top food chain.

I still have a slight doubt though because of the unknown maximum size of Cardabiodon. If really it equalled Kronosaurus in terms of mass, I give it the upper fin.

[theropod]

It was not removed that clearly at all. Much about the early upper Cretaceous remains to be learned, and Kronosaurus was not the last large pliosaur.

Advantages in efficiency (while hunting and in general), ie. fitting specializations for predominant prey, reproduction, locomotion and sensory systems are all very important factors for long-term evolutionary sucess, but none are necessarily important in a direct confrontations. Cardabiodon's vertebral anatomy suggests a fast (, endurant), tunniform swimmer with a rigid spine, so issues of swimming efficiency should be considered.

Kronosaurus has some really monstrous jaws and appears to have an overall mass advantage over (even) a 9m shark (since in 7 regression equations for lamniform lenght/weight relationships the highest number is 8t, vs 11t estimated for a large Kronosaurus), based on McHenry. In addition, it may not be as fast, but must have been very maneuverable and capable of rapid accelleration.

regarding its bulk:

Newbrey et al. said:

The centra of C.ricki are classified as round with
height equal to width (WAM 96.3.175.1; Siverson 1999: fig. 11.3A). Centra of
C. ricki are short (among all neoselachians)
ranging from 0.3 to 0.51 (ratio of length/width)
, but medium in length for lamniforms.
Centrum length is comparable to C. carcharias (0.51)

www.app.pan.pl/archive/published/app58/app20120047_acc.pdf
The same paper also estimates a specimen at 5.5m, based on a ~75cm lower-jaw perimeter.

Of course I would very much like to see further details on the jaw structure of Cardabiodon, if any such data is available...
The teeth in the profile picture above (and also those of C. venator in Siverson & Lindgren 2005) are strongly reminiscent of Parotodus, the dentition is described as quite unusual for a shark (no "but" since Parotodus' is too).

[Grey]

That's why I precised some cautiousness. All of this is based on the possibility that both are similar in size. I suggest to not compare the body mass estimates by McHenry and Siversson because Siversson seems to be more conservative than his colleague, and not only about sharks mass. He estimates Cardabiodon at 6 metric tonnes but also gives Kronosaurus some low figures. Whatever, he places both in the same class, considering Cardabiodon to be well beyond Kronosaurus upper prey size range.

My argumentation is that the physical potentially superior skills of Cardabiodon at catching preys compared to Kronosaurus have a possible impact on a direct confrontation. That is not determining but that cannot be excluded either.

Kronosaurus was not the last pliosaur but it is certain that large lamniforms sharks eventually replaced the last pliosaurs. Now we're here restricted to Early Cretaceous from Australian waters.

[theropod]

That's true, but it still does not seem as if any 9m shark would rival an 11t Kronosaurus in weight, 8t is the upper end, yielded by the most liberal regression available (btw the lowest result is still 680kg heavier than Siversson's 6t).

As long as whether and how it was superior at catching prey is not precised (or even known), we also shouldn't consider it for fight scenarios, since its relevance entirely depends on that. What we do now gives us no hint of it being the better fighter.

Besides, to date, it is generally agreed upon that there was an extinction event in the Turonian (even tough many taxa are turning out to have actually made it to the Maastrichtian, eg. Spinosaurs and Carcharodontosaurs, and there have been hints of Pliosaurs and Ichthyosaurs too, which I haven't investigated in detail yet).
So very likely either the time that Pliosaurs died out coincides with a mass extinction, or they actually survived to be repressed by a different group.

I'm not arguing sharks did not emerge as the new dominant predators (as some taxon always does after extinction events), or that they weren't tough competitors, but they likely did not do so because of direct physical superiority. Gastornithine birds and mesonychine eutherians were not physically superior to tyrannosaurines either, but could take over their niche.

Considering we heard little on Pliosaurid metabolism and hunting efficiency with regard to the evolution of prey animals during that time, it is better to search for explanations there than first consider the shark was the more powerful predator, since, after all, studies of evolution tell us it's usually not the more powerful predator that survives, but the more efficient and/or adaptable.

[Grey]

While comparing their respective size, don't forget that Siversson places Kronosaurus at a much lower figure than McHenry. I don't argue he's right (though some can speculate McHenry's figures are a bit too massive) but he seems to be conservative while using body mass estimates with any species. I don't know how he makes his estimates but what is certain is that he gave to Kronosaurus a body mass about 5 tonnes and for Cardabiodon 6 tonnes or more (stating these sharks were likely bulkier than white sharks).

As Siversson and McHenry are very colleagues and both work on overlapping fields, I cannot ignore one or the other. But I think that would be an interesting question to ask him, how does he base his weight figures in these species.

Yes efficiency is not synonymous with physical ability and we still ignore some biological features of pliosaurs. However, I find the comparison of T. rex with terror birds not related at all, as there is a great gape between both species and they've never interacted, whereas the large pliosaur and the large shark did.

What I say is that yes, this is the more efficient/adaptable which survives but it appears it can be, independantly of this, indeed the most powerful or become the most powerful with later evolution (later tylosaurines were more powerful than any Ginsu shark ever).

Cardabiodon was apparenty a big, stocky, powerful predator and even McHenry in his paper about Kronosaurus talked about an interaction between a large lamniform and a Kronosaurus individual, noticeably avoiding to establish that one had killed the other.

Another interesting question : why this mass extinction would have more affected the apex predators pliosaurs rather than the apex predators sharks ? Top predator sharks, as any other apex predators, are all sensitive to massive environnemental changes (just looking at our modern oceans), and I don't see any reason why something would have struck primarily the pliosaurs (which are themselves champions of survival).

I guess that's the basis of Siversson suggestion that beside any massive extinction event, competition from large sharks was at least a contribution to pliosaurs demise, and I don't think that a type of solitary predator physically clearly weaker than its opponent can really successfully outcompete it.

This match is very interesting because of all these factors, but I think it would be wise to ask more to Dr. Siversson.

In any case, this guy, with its huge size, heavy build and very numerous dagger-like teeth, was no clown.

[theropod]

For every top predator there comes a time to go extinct or lose it's niche.
One might ask why non-avian theropods (which are also champions of survival, as seen in their 170 million-year-long existence) went extinct, while crocodilians and sharks continued to exist.

Coelophysids lost their top-predator niche to carnosaurs, and northern-hemisphere carnosaurs lost it to tyrannosaurids later (and, considering the last reported carnosaur from North America is over 4 times the size of the first known tyrannosaurine, that existed 18 miy later, I'm prepared to argue this isn't due to physical superiority). Placoderms (sic!) lost their niche first to sharks (which weren't physically superior either), which then lost it to marine reptiles (which might have been, but more likely they had other evolutionary advantages, AND there were several mass extinctions involved), just to win it back again later.

Undoubtedly Cardabiodon is quite a monstrous creature, but we all know Kronosaurus is as well. Based on available data, it just doesn't seem as if Cardabiodon could match the latter's size.
There is no need to be a more powerful predator to win the evolutionary battle, and since everything suggests it isn't the case here, we should consider other options (many of whom exist and apply here).
Inferring Cardabiodon was more formidable based merely on evolution and weight estimates that seem inconsistent is a fairly weak approach. I agree we should ask more questions to Siversson regarding his methods and his opinion regarding McHenry's findings, perhaps he'll be able to tell us something that changes this situation.

My statement regarding their sizes is not affected by Siversson's opinion on it. Just based on a few simple points:
# if Kronosaurus was 5t, as per Siversson's figure, that would make it no heavier than a crocodile at lenght parity (actually rather less massive). Considering models presented here and elsewhere, both by fellow members and by scientists, that seems to be a highly unrealistic assertion.
# McHenry's model for Kronosaurus is probably the most elaborate weight estimate made for a pliosaur thus far (and, importantly, it is a volumetric analysis, not a guesstimate of some sort). Also note that based on his older DML posts he was once also of the opinion that Pliosaurs were very lightweight (50t for a 25m specimen), but apparently revised it himself.
# at the same time, 6t for the shark also seems a good deal too low. A better figure would be 7.5t, as is the mean of lamniform regression equations, or, if you want it more liberal, 8t, which is the maximum. That it may have been bulkier than Carcharodon (which I could find no strong support for in the paper I posted) does not mean it must have been heavier than that (let alone 40% heavier), since this is not isometric scaling.

Independantly, the best available estimates for both of them show that Kronosaurus has a weight advantage.

BTW which remains were used to conclude Cardabiodon (and Cretoxirhina too) could reach sizes of 9m?

[Grey]

I think these examples are not adequate as we are talking here about two apex predators of very similar size class, disputing the same trophic level, in the same geographical region. Not comparing different species on a longer temporal ranges. Comparing Gastornis and Tyrannosaurus with Cardabiodon and Kronosaurus is not the same thing.

I agree that some exterior events might have had played something in the demise of pliosaurs, only we cannot say why its affected pliosaurs more surely than sharks, and here we enter in a too mysterious field to discuss. The only suggestion, from Siversson, is that Cardabiodon was a better predator than Kronosaurus.

But regarding the size of Cardabiodon, it is clear that Siversson considers it "potentially heavier than the giants pliosaur Kronosaurus and that this shark might be potentially the heaviest predator in the Early Cretaceous". Check again his talk at around 18-19 min :
www.youtube.com/watch?v=e4p9EWuVxYQ

He reports large vertebra about 145 mm wide, and estimates the shark at 8.6 m and 7 tonnes.

I don't say that Cardabiodon was as heavy as Kronosaurus for sure, but I suggest to not compare McHenry's data with that, as Siversson works closely to McHenry and is certainly without a doubt aware of the results in McHhenry's thesis about Kronosaurus weight, they both work at the Kronosaurus Korner and their fields of research are clearly overlapping : www.kronosauruskorner.com.au/research

So, since Siversson is perfectly aware of McHenry's works and still suggests Cardabiodon as the largest predator, I'd not state with certainty that Kronosaurus was the largest. The best would be to ask him directly about Kronosaurus mass estimates and not arbitrary compare McHenry's works and Siversson's.

Also, I don't consider all coherentsheaf words as written in the stone, but in one post he said for some reasons that McHenry's estimates could be potentially a bit too massive, though I'm not certain of this.

[coherentsheaf]

McHenry could be too massive, Siverson is probably wrong: Even an elongate Rhomaleosaurus would weigh more than that at 11m length.

[Grey]

I'd say Siversson weight estimates are not wrong but very moderate/conservative, as his weight figures are not low only for the pliosaurs. I recall Forrest was even more conservative.

[blaze]

theropod

Pachyderms? lol I know what you meant though.

Is the 5 tonnes supposed to represent the biggest specimens? there's a fair amount of specimens less than 9m long, which will weight about 5 tonnes based on McHenry's estimate for the Harvard specimen, even then, that Kronosaurus weighted less than McHenry estimated is not that far fetched, based on McHenry's measurements, even the Harvard specimen had a body length of only around 3.3m, for comparison my reconstruction of the biggest Deinosuchus has a body length just above 3m and that of Sarcosuchus is 3.3m too, whoever is heavier at length parity depends on who has the more voluminous torso and what weights more, the crocodilians tail or Kronosaurus's head and neck, which compromises almost 40% of its total length.

[theropod]

Again, I do not compare McHenry's work to Siversson's, I'm well aware Siverson gives more conservative figures (as I noted in my post) in general. I'm simply comparing the weight for a 9m lamniform (based on several regression equations) to that estimated for a 10.5m Kronosaurus.
I gave reasons why I think 5t are not a realistic weight figure for the latter. Yes, closer for average-sized specimens of Kronosaurus, but so will be smaller figures for Cardabiodon.

Perhaps McHenry's estimate is a bit too massive, but based on Coherentsheaf's GDI of Rhomaleosaurus it would still have a weight advantage even then, and as he stated, Rhomaleosaurus is comparatively slender.

It is true Forrest was even more conservative, but neither he nor Siversson gave any method supporting such low weight figures.
EDIT: Nope, he isn't. going by 2.5t for a 7m Liopleurodon we arrive at more than 7t at 10m.
EDIT2: I got that wrong, he really is (as he states based on a very rough calculation tough). He didn't consider 7m to be the upper bound at all, but the whole think based on the 1/7 head-TL ratio and is thus of limited relevance here.

blaze: Not sure what it was meant to represent. But 9m doesn't seem to be the average Cardabiodon.
Sorry about the pachyderms

[coherentsheaf]

Jan 4, 2014 7:12:20 GMT 5 blaze said:

theropod

Pachyderms? lol I know what you meant though.

Is the 5 tonnes supposed to represent the biggest specimens? there's a fair amount of specimens less than 9m long, which will weight about 5 tonnes based on McHenry's estimate for the Harvard specimen, even then, that Kronosaurus weighted less than McHenry estimated is not that far fetched, based on McHenry's measurements, even the Harvard specimen had a body length of only around 3.3m, for comparison my reconstruction of the biggest Deinosuchus has a body length just above 3m and that of Sarcosuchus is 3.3m too, whoever is heavier at length parity depends on who has the more voluminous torso and what weights more, the crocodilians tail or Kronosaurus's head and neck, which compromises almost 40% of its total length.

Torso of pliosaurs is probalby more voluminous at equal length. When you look at relatively complete specimen it looks a good deal wider than deep.