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Argentinosaurus skeletal by palaeozoologist Argentinosaurus skeletal by palaeozoologist
This is a very speculative multiple-view skeletal restoration of Argentinosaurus, one of the larger titanosaurs. Argentinosaurus is only known from 6 described dorsal vertebrae (with an additional undescribed seventh dorsal vertebrae apparently known - left out from this reconstruction), a partial sacrum, fibula (originally described as a tibia) and referred femurs and partial ilium (neither of which have been properly described or figured) (Bonaparte and Coria, 1993). As such, only about 15% of its postcranial skeleton is known from fossil material (none of the cranial material is known). All described or photographed material is in white, while unknown or non-figured material is left dark gray. Because it was so incomplete, missing material is based off of relatives, this includes Alamosaurus for the neck and tail (modified slightly in the case of the tail vertebrae to accommodate taller neural spines in the dorsal vertebrae), Opisthocoelicaudia for the limbs and scapula, and (because I could only find oblique views of the ilium) Neuquensaurus and Isisaurus for the ilium. Also the skull is modified from Adam Yate's reconstruction of the skull of Antarctosaurus which can be seen here: [link] . All of these species have been found to phylogenetically bracket Argentinosaurus more closely than other tianosaur taxa, and this is why I used them to fill in the missing parts (Curry Rogers, 2005).

I would not normally do a multi-view skeletal for such an incomplete taxon, but I did one anyways because I wanted to do a GDI mass estimate, since Argentinosaurus is normally listed as one of the larger dinosaurs. More on that technique here.

As restored here, Argentinosaurus is about 28.89 meters (94.75 ft) long with the neck raised or about 29.65 (97.25 ft) meters long with the neck straightened out. [Edit: I should point out that this is the projection of the length of the silhouette onto the ground, instead of the length that we usually think of in living animals, where they are measured along the back or belly. See comments by dracontes below] So it turns out to be a bit shorter than I have previously estimated (I thought it would come out at about 35 meters or so). The aforementioned GDI mass estimate gave a total volume of about 87.82 m3 and a resultant mass of 64.17 tonnes (70.5 US (short) tons). I used specific density estimates of 0.3 (300 kg/m3) for the neck, 0.8 (800 kg/m3) for the torso and tail and 1.0 (1000 kg/m3) for the limbs. This is considerably lighter than many previous mass estimates with often gave mass estimates in the 75-100 tonne range, although it is heavier than Greg Paul's most recent (2010) mass estimate of 55 tonnes.

My reconstruction conservatively restored the length of the torso and the densities I used may be considered on the low-end of the range of plausible densities, so it may be possible to add a few more tonnes. For example, increasing the density of the limbs to between 1.2 and 1.4 (which are equally plausible in my opinion) would lead to a mass estimate of between ~66 and ~69 tonnes. Also, the length of the missing dorsal vertebrae are restored with an average of the known dorsal vertebrae in size. This could lead to an underestimate because in at least some titanosaurs, the anterior dorsal vertebrae get longer as they get closer to the neck.

At any rate, with the available evidence, I think it looks like Alamosaurus probably got a bit larger than Argentinosaurus, although we have many more specimens of Alamosaurus so this could simply be sampling bias. Until recently, the largest available specimens of Alamosaurus were in the 15-20 meter range, with new discoveries potentially in the 25 meter range, so it may be that there were 35 meter, 110+ tonne Argentinosaurus specimens. We maybe just haven't found them yet. Until such specimens are found, I'm fairly comfortable with calling Alamosaurus larger.

Refs--

Bonaparte J, Coria R (1993). "Un nuevo y gigantesco sauropodo titanosaurio de la Formacion Rio Limay (Albiano-Cenomaniano) de la Provincia del Neuquen, Argentina". Ameghiniana 30 (3): 271–282.

Curry Rogers, K. A., 2005, "Titanosauria: A Phylogenetic Overview" in Curry Rogers and Wilson (eds), The Sauropods: Evolution and Paleobiology pp. 50–103

Paul, G.S."MASS ESTIMATE TABLE". 2010. [link]
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:iconbricksmashtv:
bricksmashtv Featured By Owner Aug 22, 2016  Hobbyist General Artist
I know you believe that Argentinosaurus is a rather advanced Titanosaur, but the last three major Titanosaur analyses found Argentinosaurus to be a basal Titanosaur of Andesauroid affinities. Waht's your take on it?

References
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Lacovara, Kenneth J.; Ibiricu, L.M.; Lamanna, M.C.; Poole, J.C.; Schroeter, E.R.; Ullmann, P.V.; Voegele, K.K.; Boles, Z.M.; Egerton, V.M.; Harris, J.D.; Martínez, R.D.; Novas, F.E. (September 4, 2014). "A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina"Scientific Reports4: 6196. doi:10.1038/srep06196PMID 25186586.

González Riga, Bernardo J.; Lamanna, Matthew C.; Ortiz David, Leonardo D.; Calvo, Jorge O.; Coria, Juan P. (2016). "A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot". Scientific Reports6: 19165. doi:10.1038/srep19165ISSN 2045-2322.

Gorscak E, O‘Connor PM. 2016 Time-calibrated models support congruency between Cretaceous continental rifting and titanosaurian evolutionary history. Biol. Lett. 12: 20151047. dx.doi.org/10.1098/rsbl.2015.1…

Supplementary for last paper
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Oct 19, 2016  Hobbyist General Artist
I wouldn't say 'believe', I would say that I favor the hypothesis that it would be in a more 'derived' position. What that means for titanosaurs - I'm not sure as some formerly regarded 'basal' titanosaurs are now hypothesized to be derived and vice-versa (ex: Tapuiasaurus). I think part of the issue is that Argentinosaurus is coded incorrectly for some characters. More specifically, how the hyposphene-hypantrum complex is coded. This is always coded as present, but the structure is not actually similar to that seen in other basal titanosaurs (such as Epachthosaurus), and appears to be a convergent structure. I would hypothesize that if it were coded correctly, it was probably be closer to Opisthocoelicaudia based on overall similarities. That said, I'm not committed to this. But until Argentinosaurus is properly described and coded, it will be hard to tell either way. Another problem is how incomplete it is, which could make it's position more unstable the more data we get from other taxa.
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:iconbricksmashtv:
bricksmashtv Featured By Owner Oct 19, 2016  Hobbyist General Artist
okay fair enough. I'd like to see a good description of Argentinosaurus that's for sure. 

Indeed incomplete taxa are far more unstable, and often times cladistic analyses are just too poorly made to handle these incomplete taxa (I mean Curry-Rogers initial cladogram in her 2005 paper was essentially a massive polytomy of Titanosaurs). Hence why some (such as Ken Carpenter and Fernando Novas) are skeptical of these analyses.
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:iconforbiddenparadise64:
ForbiddenParadise64 Featured By Owner Sep 23, 2016
Yeah his estimate for Argentinosaurus's size seems beyond conservative, even minimalist. We know that small necks and tails were counter-intuitive for a high browsing lifestyle, and that andesaurids and Ruwakatitan were close relatives instead, resulting in a much larger and longer beast than this. 33-35m and 80-85 tonnes seems plausible, given that it wasn't just a scaled up saltosaurus but a much more basal beast-(even Alamosaurus was much more elongated than saltosaurus, so there's no reason why this would be different).
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:iconbricksmashtv:
bricksmashtv Featured By Owner Sep 23, 2016  Hobbyist General Artist
Yes thank you! Finally someone other than me and Nima realize this!
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:iconforbiddenparadise64:
ForbiddenParadise64 Featured By Owner Sep 23, 2016
Also this guy's models (though good) seem very shrink-wrapped meaning disproportionately small soft tissue. Heck, I think Nima's constructions seem shrink wrapped, particularly the neck and face. And Scott's 55 tonnes for Argentinosaurus? That sounds more like a highly starved saltosaurus than a genuine giant. Four sauropods were almost certainly larger than Argentinosaurus now anyway, those being Puertosaurus, Alamosaurus, the Chubut Monster and the new Barosaurus data according to SVPOW.
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:iconbricksmashtv:
bricksmashtv Featured By Owner Sep 23, 2016  Hobbyist General Artist
Well in weight yes, but in length only the Chubut Monter (assuming the femora are 2.6m and not 2.4m) and of course Barosaurus.

And yea I would agree, Zach's is shrink-wrapped even by GSP standards (no offense Zach, but please, feed your Dinosaurs!).
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:iconforbiddenparadise64:
ForbiddenParadise64 Featured By Owner Dec 26, 2016
I got it wrong it wasn't Scott who did a 55 tonne argentinosaurus it was GSP lol.

Any predictions/hopes for next years paleontology? Maastrichian Australia is in my hopes :D
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:iconbricksmashtv:
bricksmashtv Featured By Owner Dec 26, 2016  Hobbyist General Artist
more Macronarians. Maybe some of these Tyrannosaurus specimens can get described finally (so I can prove they are separate species, muahahahahha).
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:iconforbiddenparadise64:
ForbiddenParadise64 Featured By Owner Dec 27, 2016
Lol, you nefarious beggar. That said, T.tex is shaping up well, so a tyrannosaur adapted along carcharadontasaur lines would be amazing to see.
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:iconblazze92:
bLAZZE92 Featured By Owner Sep 24, 2014
Could it have had a higher shouldered stance? the angle of the shoulder blade seems to be less than 30°, what about Schwartz et al. (2007) conclusions that the shoulder blade in sauropods was angled at ~60°?

You also mention that a longer femur (than 250cm) would give it very odd proportions but since now we know of other titanosaurus with even longer femora relative to the fibula (Dreadnoughtus) it wouldn't be that odd now, right?

Another question, in Dreadnoughtus, Epachthosaurus and Ophistocelicaudia the humerus is around 85% of the length of the femur, what lead you to give your Argentinosaurus a humerus only ~75% the length of the femur?
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Oct 19, 2014  Hobbyist General Artist
Follow-up on the shoulder stance: I remembered seeing something about less vertical shoulder blades. This post on the DML explains somewhat (and provides an abstract reference, although I don't think anything has been officially published): dml.cmnh.org/2003Oct/msg00029.… . The most relevant passage reads, "A flattened area on the lateral surface of dorsal ribs 2-5 in Apatosaurus indicates the likely position of attachment of the scapula to the trunk. If these contours indeed reflect the position of the scapula to the trunk, this would favor a subhorizontal orientation of the shoulder girdle." They also investigated something similar in Camarasaurus. I am not sure how this squares with Schwartz et al (2007), as they also investigate the Camarasaurus and find a subvertical posture.
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Sep 27, 2014  Hobbyist General Artist
 Yeah, I should have had a higher shoulder angle than I restored here, and I probably should update it accordingly. I overlooked that somehow when I did the restoration originally. However, depending on where you put the rest of the shoulder girdle in relation to the torso, it may or may not be more high shouldered than it is here.

You are correct that the proportions of the fibula to femur in Dreadnoughtus are potentially even lower than I restored it in Argentinosaurus (~53.9% vs 62%). However, the tibia is longer in Dreadnoughtus than the fibula (the reverse is true in Opisthocoelicaudia), which means the total lower leg length relative to the femur is at least 57% (the l. tib. is listed as 109 cm, while the r. tib. is 120 cm) or possibly ~62.8 %, which is quite close to how I restored it in Argentinosaurus. In some titanosaurs the fibula and tibia are very similar in length (in Opisthocoelicaudia they are 83 cm and 81 cm respectively), while in others there is a greater difference. I assumed that the tibia and fibula in Argentinosaurus were more similar in length in my discussion with EoFauna, so when I was talking about odd proportions, I mean the proportions of the entire lower hindlimb in total compared to that of the upper hindlimb. It also depends on how much "much longer" is for the femur. Is that 5% longer, 10% longer, 15% longer, etc.? So I would say that if the tibia was similar in length to the fibula in Argentinosaurus, than a much longer femur would still mean odd proportions for the hindlimb. Note that I am not saying this isn't possible, just "odd". Don't read into it too much ;)

The humerus and femur lengths in Opisthocoelicaudia are 100 cm and 139.5 cm respectively (according to Borsuk-Bialynicka, 1977) which gives a humerus:femur ratio of ~71.7%, not ~85%. Opisthocoelicaudia has been found to be close to Argentinosaurus in some phylogenies (see refs in the main deviation description above), which is why you see a similar ratio here (indeed the missing parts of the limbs are largely restored after Opisthocoelicaudia).
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:iconblazze92:
bLAZZE92 Featured By Owner Sep 28, 2014
Damn it, I don't know what happened with the humerus/femur ratio haha I did look at Borsuk-Bialynicka (1977), probably swapped the humerus length with that of the scapula by accident.

Thanks for your answer!
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:icondarklord86:
darklord86 Featured By Owner Mar 4, 2014
Cool!
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:iconalgoroth:
Algoroth Featured By Owner Jun 25, 2013  Professional General Artist
I could quibble about many points, Zach, but no good reason to do so comes to mind. As always, your skeletal is beautifully drawn, and quite iconoclastic and idiosyncratic. Bravo! One thing I can count on from you...and it's a quality I like a lot...is the feeling of WEIGHT you give both your reconstructions and restorations. Your giant dinosaurs obviously weigh tons, quite unlike a lot of other pics available on the web.
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:iconbealmeister:
Bealmeister Featured By Owner May 6, 2013  Hobbyist General Artist
Fantastic work!

I just have a quick question; with your permission can I use this picture as reference for a webcomic a friend and I are making?
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:iconpalaeozoologist:
palaeozoologist Featured By Owner May 18, 2013  Hobbyist General Artist
Thanks!

Yes, you can use this as a reference.
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:iconbealmeister:
Bealmeister Featured By Owner May 18, 2013  Hobbyist General Artist
thank you very much. :nod:
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:iconyty2000:
yty2000 Featured By Owner Mar 15, 2013
Good work!
I have two questions:
1. it looks like the overall reconstruction is based on Futalognkosaurus and Opisthocoelicaudia. Are these animals closely related? I was under the impression that Argentinosaurus is somewhat more basal.

2. Could it have had more than 10 dorsal vetebra and a longer tail that would add a few meters to total length?
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 15, 2013  Hobbyist General Artist
Thanks!

To answer your questions:

1. The cervicals/caudals are based off of Alamosaurus, with the limbs and dorsal ribs based off of Opisthocoelicaudia. AFAIK, Futalognkosaurus and Argentinosaurus have not appeared in the same phylogenetic analysis, so I can't say whether they are related, although I doubt it. But, Opisthocoelicaudia comes out consistently to be closely related to Argentinosaurus in at least three separate phylogenetic analyses (maybe more). And yes, Argentinosaurus has often been said to be "basal", but the most recent comprehensive phylogenetic analyses always seem to put it close to Opisthocoelicaudia, making it a "derived" saltasaur. Much of the confusion methinks comes from the supposed "hyposphene/hypantrum" that it has, which is a "basal" feature, but more recent interpretations show that this isn't a true hyposphene/hypantrum, but something else. I'm fairly comfortable with it being "derived", but new analyses could show something different.

2. Yes, it could have had more dorsal vertebrae, as Opisthocoelicaudia might have 11 or 12 dorsals depending on how you interpret the "cervico-dorsal transition". And yes, the tail could easily have been longer, but we don't have any caudals, so I extrapolated from Alamosaurus and Opisthocoelicaudia which have rather short tails. The neck could have been longer as well, because again, we don't have any Argentinosaurus cervicals. So yes, adding an extra 2 or 3 meters in length is plausible. On the other hand, the neck and tail could be too long, which could easily subtract 2 or 3 meters in length. A length estimate between 25 and 31 meters seems to be most likely.

Sorry my answers were so long. ;)
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:iconyty2000:
yty2000 Featured By Owner Mar 17, 2013
Thanks for the answers. My knowledge on titanosaur systematics is quite obsolete. I gotta read through some of the references you listed.
I stared doing some skeletal drawings myself. I'd like to get some input from you, if your schedule allows.
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 18, 2013  Hobbyist General Artist
No prob.

Titanosaur systematics is in a state of flux constantly, so one new study can appear and anyone who hasn't read it could be 'obsolete'. Recently, Mike D'Emic has helped sort out the base of the titanosauriformes which helps clarify some relationships.

I think your reconstruction of Daxiatitan is excellent. I'd be happy to provide input on others, although IMHO you are already doing really well on your own. You can either message me here on DA or email me if you want at zach (dot) armstrong64 (at) yahoo (dot) com.
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:iconeofauna:
EoFauna Featured By Owner Mar 14, 2013  Professional General Artist
Congratulations for your restoration. You have to now that the partial femur is much larger than your estimation, we have measured it but we can't share the information until publish a dinosaur book we are working on. You have apply too low SG, especially in the neck, even if the cervicals had an ASP of 0.95, would have considerably higher SG because the muscles and soft tissues volume, occupy over 40-50% of the neck total volume. Sauropods may had an overall density more near to 0.9 than 0.8 suggested by Wedel (2005). (Larramendi & Molina, in prep.).

By the way do you have information of the ilium breadth?

Thanks!
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
Thank you!

I restored the femur at about 250 cm long (when complete) based off of information in Mazzetta et al (2004). They referred to an abstract by Bonaparte where a complete femur measured 250 cm long, and they got a similar length based off of regressions on the incomplete femur they figure (fig. 5). A much longer femur would give the hindlimbs very odd proportions, as the fibula is already proportionally short. Interesting. Please let me know when this information is published and I will update my restoration accordingly.

My specific gravity for the neck is based on information in Henderson (2006), where he notes that the SG of a goose neck has been experimentally found to be 0.3. It should be noted that the cervical air sacs would have likely extended into the soft tissue of the neck, further reducing the overall density. So ASP is part of the picture, but doesn't tell us everything. That said, doubling the SG to 0.6 does not dramatically alter the mass, up to ~69 tonnes instead of ~64 tonnes, which leads to an overall density of 0.79 instead of 0.73.

I have no information on the breadth of the ilium. Nothing has been published and the few photos I have seen are not much help either.

Thank you for the comments! :)

Refs--

Mazzetta, Gerardo V.; Christiansen, Per; Fariña, Richard A. (2004). "Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs". Historical Biology 16 (2-4): 71–83. doi:10.1080/08912960410001715132

Henderson, Donald M. (2006)"Burly Gaits: Centers of Mass, Stability, and the Trackways of Sauropod Dinosaurs." Journal of Vertebrate Paleontology 26(4):907–921. DOI: 10.1671/0272-4634(2006)26[907:BGCOMS]2.0.CO;2
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:icondracontes:
dracontes Featured By Owner Mar 14, 2013  Hobbyist General Artist
I think what intrigues me more here is how you obtained a length that changes somewhat with the animal's posture. I take it then that it's the length of the sauropod's silhouette projected on the ground.
That's however not particularly comparable with lengths of living animals which are measured along the back or the belly, the former of which I assume would be the method used for sauropods were they living today. I am aware that it's a bit of a complication to obtain that measurement: at least you can be explicit on how you obtained the one you mentioned in the description.

"I used specific density estimates of 0.3 (300 kg/m3) for the neck, 0.8 (800 kg/m3) for the neck and tail and 1.0 (1000 kg/m3) for the limbs."
Surely you mean "torso" with that second "neck".

I'm slightly weirded out by the ribs on the front view: I would expect them to curve more medially at the distal portions. Then again my expectations and reality are two different things.

Otherwise great work: I hope you don't mind my niggling too much ;)
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:iconblazze92:
bLAZZE92 Featured By Owner Mar 15, 2013
Dinosaur lengths are normally reported as the length of the axial skeleton, so the method used by Zach is fairly accurate given how the neck and tail are straightened out in his skeletal.
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
Thanks for giving me a heads up on the typo about the densities, it is now corrected! :)

You are correct that my length estimate is for the silhouette projected on the ground. I agree that this is not how living animals are measured, but I have no easy way to do a similar measurement on my skeletal. I will make a note to that effect. If you know of a way, please let me know.

The dorsal ribs are based off of Opisthocoelicaudia in front view. Specifically based on fig. 5 in Borsuk-Białynicka (1977). I should have noted this in my description, but you are seeing the 4th dorsal vertebrae and ribs in my Argentinosaurus, which is the same as fig. 5 in Borsuk-Białynicka (1977). The ribs do not curve much medially in the distal proportions there, so I assumed something similar. Unfortunately, titanosaur dorsal ribs are rarely figured, so this is guess-work on my part to some degree.

BTW, I don't mind the "niggling", in fact, I appreciate it. I'd much rather have constructive comments than favs any day. :D

Refs--

Borsuk-Bialynicka, M. 1977. A new camarasaurid sauropod, Opisthocoelicaudia skarzynskii, gen. n., sp. n. from the Upper Cretaceous of Mongolia. Palaeontol. Polonica 37: 1–64.
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:iconfragillimus335:
Fragillimus335 Featured By Owner Mar 13, 2013  Hobbyist General Artist
What's up with the skull? Any reason for the Nigersaurus-ness of it?
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
The skull is modeled after Antarctosaurus, a titanosaur which has come out to be closely related to Argentinosaurus in some phylogenetic analyses. The skull of Antarctosaurus has some broad similarities in the overall shape to Nigersaurus, but it is clearly a titanosaur, not a rebbachisaur. So I would say this is convergence. Of course, the skull of Argentinosaurus might look nothing like this. This is just a guess based on some phylogenetic bracketing.
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:iconfragillimus335:
Fragillimus335 Featured By Owner Mar 14, 2013  Hobbyist General Artist
Ok, thats for the info.
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
No prob.
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:icontyrannosaurusprime:
TyrannosaurusPrime Featured By Owner Mar 13, 2013
The legs look quite short.... :O
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
Yeah, in comparison to Alamosaurus the femur comes out to be a lot shorter in proportion to the rest of the body.
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:icondinobirdman:
DinoBirdMan Featured By Owner Mar 13, 2013  Student Artist
That was a one giant sauropod!
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:iconpalaeozoologist:
palaeozoologist Featured By Owner Mar 14, 2013  Hobbyist General Artist
True that! :)
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:icondinobirdman:
DinoBirdMan Featured By Owner Mar 14, 2013  Student Artist
;)
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