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Oxalaia quilombensis v Suchomimus tenerensis
Topic Started: Jul 3 2014, 09:41 PM (4,684 Views)
Taipan
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Oxalaia quilombensis
Oxalaia (a reference to the African deity Oxalá) is a genus of carnivorous theropod. It is a spinosaurine spinosaurid which lived during the late Cretaceous (early Cenomanian stage, about 98 mya) in what is now Brazil. Oxalaia is known from the holotype MN 6117-V, fused premaxillae of a very large individual and from the referred fragment MN 6119-V, an isolated and incomplete left maxilla, which were found on Cajual Island, Maranhão State of northeastern Brazil. Fossils of Oxalaia were recovered in 2004 from the Laje do Coringa locality of the Alcântara Formation, part of the Itapecuru Group of the São Luís Basin. Besides these bone fragments, numerous spinosaurid teeth had earlier been reported from the site. The genus was named by Alexander Wilhelm Armin Kellner, Sergio A.K. Azevedeo, Elaine B. Machado, Luciana B. Carvalho and Deise D.R. Henriques in 2011 and the type species is Oxalaia quilombensis. The specific name quilombensis refers to the quilombo settlements, such as on Cajual Island, which were founded by escaped slaves. Estimates suggest that it was 12 to 14 metres (39 to 46 ft) in length and 5 to 7 tonnes (5.5 to 7.7 short tons) in weight —- it is the largest theropod known from Brazil and the eighth officially named species of theropod from Brazil.

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Suchomimus tenerensis
Suchomimus ("crocodile mimic") is a genus of large spinosaurid dinosaur with a crocodile-like mouth that lived between 121–112 million years ago, during the late Aptian stage of the Cretaceous period in Africa. Unlike most giant theropods, Suchomimus had a very long, low snout and narrow jaws studded with some 100 teeth, not very sharp and curving slightly backward. The tip of the snout was enlarged and carried a "rosette" of longer teeth. The animal is reminiscent of crocodilians that eat mainly fish, such as the living gharial, a type of large crocodile with a very long, slim snout, from the region of India. Suchomimus also had a tall extension of its vertebrae which may have held up some kind of low flap, ridge or sail of skin, as seen in much more exaggerated form in Spinosaurus. Detailed study shows that the specimen of Suchomimus was a subadult about 11 meters (36 ft) in length and weighing between 2.9t and 4.8t, but scientists think that it may have grown to about 12 meters (40 ft) long, approaching the size of Tyrannosaurus. The overall impression is of a massive and powerful creature that ate fish and presumably other sorts of meat (carrion, if naught else) more than 100 million years ago, when the Sahara was a lush, swampy habitat.

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Teratophoneus
Jul 3 2014, 07:45 PM
What about Suchomimus v Oxalaia?
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Teratophoneus
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Ceratodromeus
Dec 18 2014, 03:28 AM
Hatzegopteryx
Dec 17 2014, 02:09 AM
Oxalaia quilombensis could have been, very likely, quadrupedal, just like Spinosaurus aegyptiacus. In that case, I support Suchomimus tenerensis, though the idea that Oxalaia quilombensis and Spinosaurus aegyptiacus were the same species would lead to a different result.
Have you seen cau's work on the matter? It's quite good imo:
"...Russell (1996) hypothesized that Sigilmassasaurus was a bizarre dinosaur with a neck "U", ie, with a sharp decline at the base of the neck, which was thus projected so sub-perpendicular to the axis of the spine. The hypothesis was based on the very peculiar shape of the vertebrae cervicodorsali: short, wide facet joint, convex anteriorly and expanded transversely, which suggests a marked mobility, coupled with a very small neural spines, and a well developed ventral hull, insertion of powerful flexor muscles.
We now know that those vertebrae belong to Spinosaurus, but what about the interpretation of Russell (1996)? It may be valid? If applied to Spinosaurus, produces a neck that, compared to the spine, is subvertical. This subverticalità is also accentuated by the fact that the neck vertebrae in spinosauridi produce a reduced sigmoidalità. Note that the reduced neural spines in the vertebrae cervicodorsali "allow" to extend the neck there is no contact between the cervical spine and cervicodorsali, or between them and the high spine vertebrae later.
Note that this posture is virtually absent from the iconography of Spinosaurus. But if it was correct (or at least possible), what would? Moreover, as it combines this posture of the base of the neck with the peculiar form of the skull base of spinosauridi?
In short, combining the hypothesis of the neck of Sigilmassasaurus to Spinosaurus, and inserting at the base of this neck head "tilted" deduced from the characteristics of the skull, is a posture "by pelican" for this theropode."
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"What can be the meaning of such a posture? One effect of this posture is that, compared to the "sub-horizontal" (followed by many reconstructions), the center of gravity of Spinosaurus would be much lower moved posteriorly. This result is very interesting, because it might imply that, despite the elongate dorsal and legs reduced, the center of gravity of Spinosaurus was not very "abnormal". This is crucial in solving the heated discussion that concerns around the new study, since Ibrahim et al. (2014), however, propose that, according to their model, the center of gravity of Spinosaurus was so as to impose a front posture quadruped. [Since I do not have the means to test the computer center of gravity in a reconstruction (including the one I propose here), the question of the center of gravity remains pending. Nevertheless, regardless of bipedia or fours, it is very likely that a posture "by pelican" can compensate (even in part) a potential imbalance front of the center of mass, and therefore should be considered by anyone who wants to quantify the center of gravity of Spinosaurus"

"Returning to the posture "by pelican", for it to be effective in an animal like Spinosaurus , much bigger than any pelican, with a skull over a meter and a half and relatively compact in the front, it must be that the head is held in suspension by passive some system of nuchal ligaments well developed. This ligament, inevitably, must be anchored to the dorsal neural spines, in analogy with what we observe today with large mammals with large skulls.A system of ligaments passive is much more useful to the less muscle work requires. For example, an elastic ligament which offsets the force of gravity automatically generates a stable system that requires no muscular effort. This strategy would be very advantageous for an animal like Spinosaurus , given the size of his skull.How to combine this interpretation with the posture of the neck suggested by Russell? A passive ligament to maintain erect neck (thus, overcome the force of gravity) probably requires a relatively high rear anchor on the dorsal region, in order to exploit in some way linked to the resultant force of gravity. We observe this adaptation in mammals grazers, in which the head tends to be positioned ventral to the chest, and this last port of the neural spines relatively elongated. Returning to our theropode, as we can anchor an elastic ligament to a head which in turn is suspended on a vertical neck? We could do it by lifting the anchoring of the ligaments to the level of the head. That is, we could develop the neural spines very high, as much as the high position of the head.And it is precisely what we observe in Spinosaurus when we articulate the neck with the posture of Russell!"
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Functionally it makes sense and seeing how Russel proposed this "U-shaped" neck for Sigilmassasaurus, now synonymoys with S.aegyptiacus, it makes sense
Teratophoneus
Dec 17 2014, 11:00 PM
Ceratodromeus
Dec 17 2014, 02:05 AM
ooof...my posts kinda sucked back then..

anyway, this probably isn't far from a 50/50. the 1.35 m estimate for oxalaia's skull isn't supported by much, the premaxillae isn't that large and beside that we don't have a whole lot of material. anyway, i got 1.18 m for oxalaia's skull, suggesting an overall body length of ~11 meters(sucho-sized)

for now, based on this, i say 50/50.
Actually, Hartman's skeletal was over 11 m long, close to 11.6-11.8 m long. And it wasn't fully grown. I believe that Suchomimus is the winner here, due to its larger size and its longer skull.
Are you talking about suchomimus or oxalaia?
Regardless "11 meters" includes 11.1-11.9, at least in the sense that i was using it.
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And it wasn't fully grown

Evidence for this? Nothing in A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids(Sereno, 1998) Suggested that S.tenerensis was immature.

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its longer skull

Assuming my 1.18 estimate for O. quilombensis is correct, nothing i've seen suggests
S. tenerensis had a skull any longer then this. And in any case, .10ths of a meter really wouldn't be a deciding factor here regarding skull lengths.
I'm talking about Suchomimus.

11 meters=11 meters, if you meant 11.1-11.9 m you had to say 11 m range.

Hartman's skeletal has a 143 cm long skull. If Oxalaia's skull was 1.1-1.2 m long, the difference is very substantial.

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Ceratodromeus
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i do not have to do anything. it's obvious from the context of my post what i meant. any way, if we round to the nearest digit(which you're opposed to for some reason)
S. tenerensis - 1.4 meters
O. quilombensis 1.2 meters

two .10ths of a meter is certainly not substantial. let alone be a defintive advantage.
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Teratophoneus
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Ceratodromeus
Dec 19 2014, 01:28 AM
i do not have to do anything. it's obvious from the context of my post what i meant. any way, if we round to the nearest digit(which you're opposed to for some reason)
S. tenerensis - 1.4 meters
O. quilombensis 1.2 meters

two .10ths of a meter is certainly not substantial. let alone be a defintive advantage.
No, it isn't obvious. You said ~11 m, and ~=about. 11.6 m, for example, isn't 11 m. When someone says ~11 m it's clear that he means that it's something like 10.9 or 11.1 m.

0.2 m of advantage is enough, especially when two animals are very similar.
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Ceratodromeus
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Okay, two theropods that are very similar. Based on various estimates carch and giga have skull lengths similar to each other, within a tenth of each other i believe. You believe that match is a 50/50, so why would this ~.2 meter longer skull have any more significant meaning in this match? do you have anything suggesting skull length differences of ~.2 meters to be a deciding factor in any interspecific conflict?

right now it just appears to be your opinion.
Edited by Ceratodromeus, Dec 19 2014, 12:08 PM.
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theropod
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It would have the significance of the difference between a 12m theropod and a 14m theropod, given that it was actually present.
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Ceratodromeus
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theropod
Dec 19 2014, 08:21 PM
It would have the significance of the difference between a 12m theropod and a 14m theropod, given that it was actually present.
Isn't ~14 meters based on spinosaurus?
Because, basing off of S.hartmans Spinosaurus is where i get the ~1.2meter skull length;
11.7 meters TBL.
At best it'd be marginally larger then Suchomimus, but i see nothing to really indicate a 14 meter animal.
Edited by Ceratodromeus, Dec 20 2014, 02:32 AM.
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theropod
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That wasn't my point, I haven't checked. The point is that a 1.4m skull is as much larger than a 1.2m skull as a 14m theropod is larger than a 12m one. That's a very significant difference, almost 60% in cubic terms.
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blaze
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I though you had realized that the 12-14m range for Oxalaia is scaled down from Dal Sasso et al. (2005) range of 16-18m for Spinosaurus.
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theropod
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I have, I wasn’t referring to the sizes of these two, I merely tried to point out just how big the difference between the two skull lenghts listed eariler is. I bet nobody would say that the difference between 14m and 12m or a 60% weight advantage doesn’t matter, yet it appears that because the absolute difference between 1.2m and 1.4m is just 20cm people are mistakenly considering it irrelevant.
If the longer skull one was not radically more slender (which is exceedingly unlikely), its actually a huge difference in terms of size. Leaving aside that it’s "just" 20cm, this 17% difference is probably not limited to skull size.
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blaze
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Oh, now I get it.

About that difference, you have a point but I it also depends in the reconstruction, Hartman's Baryonyx and Suchomimus have longer snouts than other, I guess comparing the two snouts would be best if trying to gauge the size of the specimens compared to each other.
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The Reptile
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Ausar
Dec 17 2014, 05:22 AM
I'm still not really flat out 100% sure on quadrupedality in S. aegyptiacus.
Spinodontosaurus had doubts too. Although it would definitely make a good deal of sense as long as balance was a contributing factor.
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Ceratodromeus
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theropod
Dec 20 2014, 10:15 PM
I have, I wasn’t referring to the sizes of these two, I merely tried to point out just how big the difference between the two skull lenghts listed eariler is. I bet nobody would say that the difference between 14m and 12m or a 60% weight advantage doesn’t matter, yet it appears that because the absolute difference between 1.2m and 1.4m is just 20cm people are mistakenly considering it irrelevant.
If the longer skull one was not radically more slender (which is exceedingly unlikely), its actually a huge difference in terms of size. Leaving aside that it’s "just" 20cm, this 17% difference is probably not limited to skull size.
didn't state it was irrelevent once. i was merely remarking on the difference.
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theropod
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Well, it’s a pretty significant difference if your estimates are correct, although as blaze pointed out issues related to the reconstruction should be taken into account here (and everywhere else for that matter).
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TheBeast
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Sucho wins. Why? He's more robust, and oxa has sail.
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theropod
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"Oxa has sail"?

How would you know?
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