Mapusaurus roseae versus Tyrannotitan chubutensis

[gigadino96]

Mapusaurus roseae

Mapusaurus ("earth lizard") was a giant carnosaurian dinosaur from the early Late Cretaceous (Cenomanian stage) of what is now Argentina. It was similar in size to its close relative Giganotosaurus, with the largest known individuals estimated as over 10.2 metres (33 ft) in length* and weighing approximately 3 metric tons (3.3 short tons).[1] Mapusaurus was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation (Rio Limay Group, Cenomanian) at Canadon de Gato. It was described and named by paleontologists Rodolfo Coria and Phil Currie in 2006.[1]

The name Mapusaurus is derived from the Mapuche word Mapu, meaning 'of the Land' or 'of the Earth' and the Greek sauros, meaning 'lizard'. The type species, Mapusaurus roseae, is named for both the rose-colored rocks, in which the fossils were found and for Rose Letwin, who sponsored the expeditions which recovered these fossils.

*These sizes are good for the largest example of which was provided estimates. The maximum known size is 13.6 meters long and 9 tonnes of weight.



Tyrannotitan chubutensis

Tyrannotitan is a genus of huge bipedal carnivorous dinosaur of the carcharodontosaurid family from the Aptian stage of the early Cretaceous period, discovered in Argentina. It is closely related to other giant predators like Giganotosaurus and Carcharodontosaurus. Its fearsome appearance is reflected in the meaning of its name, "Tyrant titan". Tyrannotitan chubutensis was described by Fernando E. Novas, Silvina de Valais, Pat Vickers-Rich, and Tom Rich in 2005.[1] The fossils were found at La Juanita Farm, 28 kilometres (17 mi) northeast of Paso de Indios, Chubut Province, Argentina. They are believed to have been from the Cerro Castaño Member, Cerro Barcino Formation (Aptian stage) around 112.2 - 121 million years ago.

The holotype material was designated MPEF-PV 1156 and included partial dentaries, teeth, back vertebrae 3-8 and 11-14, proximal tail vertebrae, ribs and chevrons, a fragmentary scapulocoracoid, humerus, ulna, partial ilium, a nearly complete femur, fibula, and left metatarsal 2.

Additional material (designated MPEF-PV 1157) included jugals, a right dentary, teeth, atlas vertebra, neck vertebra (?) 9, back vertebrae (?)7, 10, 13, fused sacral centra (5 total), an assortment of distal caudals, ribs, the right femur, a fragmentary left metatarsal 2, pedal phalanges 2-1, 2-2, and 3-3.

The length of these animals has estimated at up to 13 meters and mass 8.9 tonnes.[2]

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Who win?

[theropod]

Mapusaurus: estimated at >12,2m
Tyrannotitan: estimated at <12,2m

For 12,2m just fill in the lenght of the Giganotosaurus holotype as both are probably based on it.
The largest Mapusaurus would be about 10% longer, and the paratype of T. chubutensis would be about the same size.

I would consider 12,4 or maybe a bit more a better estimate for the MUCPv-CH1, because 12,2m lacks given metods or visible evidence while the shorter of the two skeletals we have suggests 12,4m.
That'd make Mapusaurus 13,6-13,8m or more. I think based on the size of what we have Mapusaurus roseae impresses me more than Tyrannotitan chubutensis, but I unfortunately cannot read the description, neither is it very detailed from what I heard.

[creature386]

From all we know, Mapusaurus was likely larger, so I support it.

EDIT: Too slow.

[creature386]

Uhm, this paper seems to claim Mapusaurus got only up to 11 m long:
www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0063409
But it also seems to claim Mapusaurus was comparable to Giganotosaurus and Tyrannosaurus in size. I think when saying comparable in size to T. rex, these guys seem to count bigger than 10 m already as comparable (the 11,5 m Acrocanthosaurus was also claimed to be comparable in size to Giganotosaurus and Tyrannosaurus by Carrano).

[Grey]

As it seems Mapusaurus is the larger animal and especially the most advanced in this lineage, it takes it, not by a big margin.

[theropod]

@creature: That's definitely just a rough, cautious figure, you can read figures like that quite often, for example when in a sauropod paper they state the largest reached 50t or more.

Grey: What features and advantages is this "advanced" position in its lineage seen in?

[Grey]

The longer position and adaptability as an apex predator than its ancestor, size, skills, tactics up to date.

[theropod]

Mapusaurus and Tyrannotitan each are only known from a single stratigraphic location, hence there are no difference in the factor of longevity.
Having lived a bit later doesn't imply superior fighting skills or tactics, does it? And keep in mind we aren't talking about hundreds of millions of years, but about the difference between early middle cretaceous and late middle cretaceous, and generelly similarly optimised taxa with similar prey (which doesn't get better, but merely changes).


"Advanced" or "derived" are problematic terms and usually misunderstood. Everyone would agree the lack of a dermatocranium, laws formed by the viscerocranium and only connected to the hyomandibula alone and a cartilaginous skeleton are basal or "primitive" characters among vertebrates, which is why elasmobranchs are commonly used as examples of the plesiomorphic vertebrate jaw. Does this mean sharks are automatically screwed against a similar-sized "advanced" vertebrate, eg an odontocete, with similar ecology?
Basal characters alone do not imply inferiority. You can infer a lineage or taxon to be less "advanced" if you want, but it doesn't mean much except for phylogeny.

[Grey]

I assume an animal more sophisticated with passage of time, within the same lineage. Added to the most likely superior size...

[theropod]

I fully agree with the size-part, however being more derived in a lineage doesn't necessarily have any functional inferences for a fight scenario.

Evolution is about getting better suited for the changing enviroment, not about becoming a superior fighter. There is no higher selective pressure to be a better fighter on an ecologically nearly identical animal that lived some million years later.
What's indeed often seen is it becoming larger as the only specialisation left.

Edit: to be fair, the size is problematic since while the biggest M. roseae is almost certianly a good deal bigger than the T. chubutensis paratype, it is still difficult to say in how many specimens it's the biggest, and how many are adults.

[Grey]

I believe that the change in a giant apex predator through millions years of evolution cannot be really ignored in terms of reflex, skills, behavior, perhaps attacks technics, improvement of body constitution.

[theropod]

That would mean extant animals are always superior in all these terms, which they are not. "skills" frankly are no scientific term to refer to an animals capabilities. behaviour doesn't get "better", neither do reflexes (particularly in the latter case, is there anything to base that on?), attack techniques or body constitution.

In all these terms, Mapusaurus and its slightly more basal relative would be nearly identical.

Evolution simply isn't about becoming better and better. Taxa may show some specific adaption (eg. developement of intelligence in primates or cetaceans) that they enhance by speacializing, but such things are always payoffs. Animals do not improve fighting ability the longer they evolve. Stratigraphy alone is irrelevant to this fight or any other fight for that matter.

[Grey]

Modern animals in the same lineage can be "better" than their predecessors, not necessarily.

I did not argue it was a rule. But look closely at some lineages of predators, the latest is often the most powerful, the most dominant, the most sophisticated. Orca is much more powerful, macropredaceous than its direct ancestors. Megalodon was the ultimate species of its lineage. T. rex case is obvious...

In the case of Mapusaurus, we already suspect a superior size and a tendency to prey on gigantics preys. If it followed the same lifestyle than its ancestor, it appears to me improved. That's not always the case, but in the case of giants predators that's often the case.

Once again, both are poorly known but that's what suggest to me the actual datas.

[theropod]

Well, if they get larger, of course, but I was talking in relative terms.

I already agreed with your point about size, the largest specimens of Mapusaurus were probably somewhat larger than the paratype of T. chubutensis.

If we exclude size, predators cannot indefinitely continue to increase fighting abilities. Usually, once a group developes macrophagous behaviour, it will develope the fitting adaptions. From a docile to a macropredatory lifestyle, there is a huge change in functional morphology, that is absolutely true. But after the point that animals are optimized to kill large animals (herbivorous counterpart would be to defend themselves, as eg. in ceratopsians), they can only adapt to changing prey and environment, without further general improvements to how formidable they are at parity. That's the point were they usually increase size.

[Grey]

You forget that the preys evolve too and become harder to catch and thougher to subdue. This lineage of giants predators probably preyed on very large, powerful preys which themselves improved their morphology, behavior and lifestyle in response to these threats.