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| Oxalaia quilombensis v Suchomimus tenerensis | |
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| Tweet Topic Started: Jul 3 2014, 09:41 PM (4,685 Views) | |
| Taipan | Jul 3 2014, 09:41 PM Post #1 |
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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. ![]() 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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| Jinfengopteryx | Jul 6 2014, 05:40 AM Post #16 |
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Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
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This was some time ago, he now isn't like that anymore and doesn't just favor animals because they can slice. Sorry, but this was basically an ad hominem attack that has nothing to do with the content of his argument. |
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| Ceratodromeus | Jul 6 2014, 05:52 AM Post #17 |
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Aspiring herpetologist
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Back on topic, this is a pretty close match-up...i say 65-45 in favor of Sucho |
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| Hatzegopteryx | Jul 6 2014, 07:07 AM Post #18 |
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Unicellular Organism
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Spotting hypocrisy doesn't make one's point less true. It's like if my friend was in truth doing something wrong, and I was doing the same thing, I'd be hypocritical if I made a critique about his behaviour, but I wouldn't be wrong. And yes, spotting hypocrisy (tu quoque) is a special case of argumentum ad hominem. Edited by Hatzegopteryx, Jul 6 2014, 07:09 AM.
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| The Reptile | Jul 6 2014, 11:48 PM Post #19 |
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Herbivore
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Ok fine I get it, I slipped up... Carnosaur, can you elaborate? |
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| Hatzegopteryx | Jul 7 2014, 12:35 AM Post #20 |
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Unicellular Organism
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I don't really think this is far from 50/50. |
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| Ceratodromeus | Jul 7 2014, 12:54 AM Post #21 |
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Aspiring herpetologist
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Sure. Both Spinosaurs' jaws aren't all that powerful, but they have those grappling arms. I don't know how much use they would be tackling an equally sized predator, but they'll certainly do some damage. Sucho was a bit more heavily built(possibly) so i think that's why it has the edge. We really don't have a whole lot of Oxalaia, so it's just plain hard to tell. |
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| The Reptile | Jul 7 2014, 11:40 AM Post #22 |
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Herbivore
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By "heavily-built" what are you exactly referring to? Body shape? Skull morphology? What? Body-wise, baryonychines were not very bulky at all and in fact seemed to have been very slender (not to mention how spinosaurids would not be overpowering prey animals anyway regardless of bulk , unless a huge size difference was present). Whether or not this applied to spinosaurines like oxalaia is beyond me- but some have agreed that allometrically it is definitely possible that spinosaurines would have been bulkier (but again, bulk seems to be mainly hypothetical in paleontology). And in terms of skull morphology, each animal had its advantages and disadvantages- and neither possessed rostra or dentaries suited for macrophagy (both animals possessed very slender and specialized skulls). I must add that it is downright possible that spinosaurines were more well adapted for powerful killing (albeit not absolutely adapted, as I have pointed out), but that is my hypothesis only |
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| theropod | Jul 7 2014, 08:28 PM Post #23 |
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palaeontology, open source and survival enthusiast
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When someone writes "heavily built", referring to an animal, usually the whole animal is what is meant. Allometric variations in bulk are irrelevant when talking about animals of the same size. A baryonychine would be bulkier than a spinosaurine smaller than itself too in all likelyhood. |
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| retic | Jul 8 2014, 11:13 AM Post #24 |
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snake and dinosaur enthusiast
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at even weights i would say this is 50/50. |
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| Ceratodromeus | Dec 17 2014, 02:05 AM Post #25 |
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Aspiring herpetologist
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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. |
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| Hatzegopteryx | Dec 17 2014, 02:09 AM Post #26 |
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Unicellular Organism
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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. |
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| Ausar | Dec 17 2014, 05:22 AM Post #27 |
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Xi-miqa-can! Xi-miqa-can! Xi-miqa-can!
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I'm still not really flat out 100% sure on quadrupedality in S. aegyptiacus. |
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| Spinodontosaurus | Dec 17 2014, 10:57 PM Post #28 |
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Herbivore
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I'm not sold on it at all. The proportions of the new specimen I have no problem with - besides the fact that having 'problems' with objective fossil measurements is hard to accomplish - but there is nothing in that material that supports a quadrupedal gait. Ok, so it's Center of Mass is too far forward to hold the typical theropod gait. So perhaps it held its body differently. Therizinosaurids and Deinocheirus held their bodies more upright - why not Spinosaurus? |
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| Teratophoneus | Dec 17 2014, 11:00 PM Post #29 |
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Herbivore
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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. |
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| Ceratodromeus | Dec 18 2014, 03:28 AM Post #30 |
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Aspiring herpetologist
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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." ![]() "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!" ![]() Functionally it makes sense and seeing how Russel proposed this "U-shaped" neck for Sigilmassasaurus, now synonymoys with S.aegyptiacus, it makes sense 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.
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.
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. Edited by Ceratodromeus, Dec 18 2014, 03:43 AM.
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