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Argyrosaurus superbus by Paleo-King Argyrosaurus superbus by Paleo-King
Forgotten Giants species #4: Argyrosaurus superbus

Location of holotype site: Left bank of the Río Chico, near the Pampa Pelada, to the northeast of Lake Colhué-Huapi, Chubut, Argentina.
Length: ~90+ ft.
Mass: ~70 tons
Time: Late Cretaceous, but beyond that, estimates vary. Its formation, the Bajo Barreal, has been dated using some methods to the Santonian and Campanian epochs, but by others to the earlier Cenomanian. Its contemporaries include dinosaur species which sometimes overlap into the Allen formation and other faunas considered to be Campanian in age, so the former estimate is what I find more likely.

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After a LONG time of studying and cross-scaling, here is the FIRST EVER scientific restoration of the mysterious "silver lizard" of Argentina, Argyrosaurus superbus. Named for its proximity to silver mining towns, this is one of the largest and strangest giant dinosaurs ever found - and ironically it was also one of the first to be named.

The obscure discovery of this massive plant-eater over a century ago was barely reported in the papers, but for a while Argyrosaurus was actually the largest dinosaur known to science. Described a full 10 years before Brachiosaurus, and over three decades before its record was beaten by Antarctosaurus giganteus, this monster is still known from only a handful of remains, yet they indicate a creature unusually massive and large even by the standards of other South American titanosaurs.

Argyrosaurus is characterized by very long, wide humeri proportionally similar to a giant snowboard, and massive femora wider than those of almost any other known sauropod, which rival those of Antarctosaurus giganteus for sheer size. The lower arm is relatively short, the shoulder blade large and deep, and the vertebrae massive and roughly similar in shape to those of Epachthosaurus.

Several likely specimens of Argyrosaurus are known, mostly just isolated limb bones from individuals of spanning a wide range of sizes and ages. The most complete specimen is the referred teenager PVL 4628, which includes both limb elements and vertebrae, and is the only specimen complete enough to give an idea of the overall proportions of Argyrosaurus. Thus it is the critical "keystone" specimen for unlocking the secrets of this mysterious dinosaur and its relatives. The isolated scapula indicates that PVL 4628 was not a mature animal, as its coracoid and scapula were not yet fused. It would have been roughly 65-70 ft. in length at the time of its death, while the largest individuals, known only from colossal limb bones, could have topped 90 ft. And given the extremely robust proportions of this dinosaur, it would have been several times as massive as most dinosaurs of similar length.

Argyrosaurus is the founding member of a family which currently contains only one other genus, the even more incompletely known Paralititan, which was similarly robust and heavy-bodied for its length even by titanosaur standards. Their closest relative outside the family appears to be the far smaller Epachthosaurus, which puts the Argyrosauridae in a relatively derived position - more primitive than Antarctosaurids and Saltasauroids, but more advanced than Lognkosaurians.

This animal is also remarkable in having a highly weird and RECURRING tendency to leave behind its right femur as fossil evidence, and not much else.* :XD:

******************************

References:

Lydekker, R., 1893. "Contributions to the study of the fossil vertebrates of Argentina. I. The dinosaurs of Patagonia", Anales del Museo de la Plata, Seccion de Paleontologia 2: 1-14

Powell, J.E., 2003, "Revision of South American titanosaurid dinosaurs: palaeobiological, palaeobiogeographical and phylogenetic aspects", Records of the Queen Victoria Museum 111: 1-173

von Huene, F., 1929. Los saurisquios y ornitisquios del Cretacéo Argentino. Anales del Museo de La Plata (series 3) 3: 1–196. [In Spanish]

******************************

Some referred remains:

The assigned material comes from 8 localities, some of which do not correspond to the provinces of Chubut and Neuquén. For this reason, they are listed with geographic, stratigraphic, and chronologic provenance. The old geo-terminology "pre-Maastrichtian Senonian" refers to two consecutive Late Cretaceous epochs, the Santonian and Campanian, which were respectively the third-last and second-last epochs of the entire Mesozoic.

1. An anterior caudal vertebra (Huene, 1929:79). West bank of Lake Colhué-Huapi, Chubut Province. Chubut Group, Castillo Formation or Bajo Barreal Formation. Pre- Maastrichtian Senonian.
2. Two caudal vertebrae “…of the region of Neuquén” (Huene op. cit.:7). Geographic and stratigraphic provenance unknown.
3. An incomplete femur (Lydekker, 1893, pl. 5, 2; Huene, 1929:80, pl. 38, 1). To the south of the bend of the Río Sengerr, Chubut Province, probably Bajo Barreal Formation. Pre-Maastrichtian Senonian.
4. An incomplete right femur (Huene, op. cit.:80, pl. 38, 2). Near the railroad bridge over the Río Neuquén, Neuquén Province. Neuquén Group, Río Colorado Formation, perhaps Bajo de la Carpa Member. Pre-Maastrichtian Senonian.
5. A complete right femur (Huene, op. cit.:80-81, pl. 38, 3). Sierra San Bernardino, 45 km west of Colonia Sarmiento, Chubut Province. Chubut Group. Bajo Barreal Formation. Pre-Maastrichtian Senonian.
6. A humerus of a juvenile individual, referred with doubts to Argyrosaurus (Huene, op. cit.:81, pl. 37, 6). Probably from Neuquén. Uncertain geographic and stratigraphic provenance.
7. A left humerus, referred with doubts to Argyrosaurus superbus Huene, op. cit.:81, pl. 37, 4). Left margin of the Río Uruguay, near Colón, Entre Ríos Province. ?Asencio Formation. Upper Cretaceous.
8. Caudal vertebrae (Huene, op. cit.:79). To the east of the Río Leona, between lakes Viedma and Argentino, Santa Cruz Province, Upper Cretaceous (Dibenedetto, pers. comm.).

Source: Dinodata


*NOTE: the unnamed and uncatalogued "Argyrosauridae" femur from Powell (2003) is most likely a lognkosaur judging from its proportions, not an Argyrosaur.
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:iconalgoroth:
Algoroth Featured By Owner Feb 5, 2013  Professional General Artist
Just a small, tiny question. AHEM! Should the limb elements of upright quadrupeds be restored in terms of what we can see of sprawlers, like crocs and lizards, or upright animals, like birds and mammals? Just asking.

Frankly, I think most all of us have them wrong, including me, you, Zack, Jurassic Park, and most of the dino documentaries I have seen. I think many artists have theropod hindlimbs correctly, but few correct (IMO!) front limbs.
Reply
:iconpaleo-king:
Paleo-King Featured By Owner Feb 10, 2013  Professional Traditional Artist
What do you mean? The articulation of sauropod from limbs clearly only makes sense in a vertical upright posture. Not that it had to be PERFECTLY vertical (there was a slight 10-15 degree bowing at the elbow when either arms was in rear stride - this is normal in elephants and such today). But they were definitely not build for sprawling. Also their rib cages are usually so deep that if they had sprawled, they would have needed to find giant ruts to run in, because their bellies would have been well below the ground level of the hands and feet (and all their joints would have to be dislocated).

Plus it's also important to note that sauropods evolved from bipedal (and warm-blooded) ancestors. Crocs and lizards did not. To date there has never been a group of quadrupedal animals whose forelimbs have a completely different posture from their hindlimbs - it's literally impossible to coordinate movements in such an animal especially with spines as rigid as most large dinosaurs. And dinosaur footprints all point to erect forelimbs in quadrupeds.
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:iconalgoroth:
Algoroth Featured By Owner Feb 11, 2013  Professional General Artist
I was talking about lower limb robustness compared to upper limb robustness, not the vertical positioning, about which you are absolutely correct. Most upright quadrupedal animal and bipedal animals (birds and the occasional human ;)) have lower limbs that can be downright thin. But the upper limbs are often so well muscled they can scarcely be seen, as in horses, canines rhinos, etc. Even elephants' legs are well integrated with the upper bodies (skin-wise, yes, but not separate almost all the way to the shoulder), and are not thin.

When we get to sprawlers, we have a different picture. The upper limbs are mostly separate and the lower limbs, especially in the large species....crocs and large varanids...are close to being as thick as the upper limbs.

None of this is proof, of course, but, since dinosaurs and birds are so similar, why do we...me included...so often make the upper and lower limbs so alike in muscularity...whether thick or saran-wrap style?
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:iconbrolyeuphyfusion9500:
Argyrosaurus was never the largest dinosaur known to science...

Amphicoelias fragillimus was discovered in 1878, which was about 15 years before Argyrosaurus was discovered.
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:iconpaleo-king:
Paleo-King Featured By Owner Jun 13, 2012  Professional Traditional Artist
Yeah but A. fragillimus wasn't really "known" at the time aside from a handful of field workers and Cope himself. He published a brief paper on it which included no size estimates, it was soon lost or destroyed, and even at the same time many people considered it a hoax.

Most scientific publications of the 20th century listed Brachiosaurus as the biggest dinosaur (in fact up until the 80s even most paleontologists said so in their books; they forgot about Argyrosaurus and "Antarctosaurus" giganteus even though these were never lost or destroyed.) So while they were saying Brachiosaurus was the biggest, there was something larger (at least in terms of mass) discovered 10 years earlier, with published photos rather than sketches, more than a single bone, assigned an actual museum catalog number, and the material is still in existence.
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:iconteratophoneus:
Teratophoneus Featured By Owner May 11, 2012
Hey Nima, I amplanning to use this as a reference for a scientific reconstructuion of elaltitan-or better Argyrosaurus itself as you said the bone of elaltitan is that of a argyrosaurus. For this I have to know how big the specific specimen (length and height) of the elaltitan/argyrosaurus was. I hope you can help me :)
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:iconpaleo-king:
Paleo-King Featured By Owner May 11, 2012  Professional Traditional Artist
Use the scale bar, it's there for a reason LOL! :D

Both the adult and the teenage Argyrosaurus (aka "Elaltitan") are to scale with the scale bar.

The teenager is roughly 70 ft. long if I remember from last time I re-scaled it. Of course the live animal may have looked nothing like this. This is just my interpretation of how it looked based on the few bones found, and comparing it with other large titanosaurs like Alamosaurus.
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:iconpalaeozoologist:
palaeozoologist Featured By Owner May 7, 2012  Hobbyist General Artist
The dorsal vertebrae, anterior caudal vertebra, scapula and the pelvic and forelimb elements of PVL 4628 have now been referred to a new genus and species, Elaltitan lilloi, so you should probably change the name on your image for the smaller individual.

Ref--

Mannion, P. D.; Otero, A. (2012). "A reappraisal of the Late Cretaceous Argentinean sauropod dinosaur Argyrosaurus superbus, with a description of a new titanosaur genus". Journal of Vertebrate Paleontology 32 (3): 614-638.
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:iconpaleo-king:
Paleo-King Featured By Owner May 11, 2012  Professional Traditional Artist
Thanks Zach. But given what I've seen of this animal, I don't see a basis for the reclassification. Mannion previously also made some statements about titanosaur taxonomy that I consider unwarranted and flat-out wrong (such as claiming Ruyangosaurus wasn't even a titanosaur in his redescription of Andesaurus).

Based on Powell 2003 (the better scans of it anyway) PVL 4628 has basically the same arm morphology as the Argyrosaurus holotype. So much so that there is little point in referring it to "basal titanosauria" while putting PVL 4628 in derived lithostrotia.

The differences that Mannion does cite in the abstract are a bit obscure as he only says: "This specimen
is distinct from *Argyrosaurus* and can also be differentiated from other
sauropods based on an unusual character combination (including plesiomorphic
tarsus), plus one autapomorphy."

VAGUE VAGUE VAGUE. I will not endorse this conclusion until I read the paper (which is locked up behind a paywall... I wonder how much of the paleosphere is actually paying attention to SV-POW and the point they're making). One autapomorphy, plus plesiomorphic tarsus (?) and an unusual character combination.... Well it's too premature to separate it from Argyrosaurus based on ANYTHING other than a comparison of the arms, since that's all the Argyrosaurus holotype is. And the tarsus is not in the arm. A single autapomorphy (which may or may not overlap with the Argyrosaurus holotype skeletally) is pretty weak proof. It would be more parsimonious to classify PVL 4628 as an immature Argyrosaurus sigen overall morphology of the arm, and the matching formation/time horizon.

For my part I suspect any differences in the arms of the two individuals are minor enough that they can be put down to ontogeny (PVL 4628 is clearly immature based on the scapula not being fused to a coracoid), the arm elements of both individuals are very similar in overall shape and proportions. The ulnae are SO similar it's kind of freaky. So YES I am lumping. Go sue me Dr. Mannion LOL 8-)

BTW I'm curious, how did name "Elaltitan" come about? I've heard some weird rumors. Is it really named after an airline?
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:iconpalaeozoologist:
palaeozoologist Featured By Owner May 15, 2012  Hobbyist General Artist
Just because Phil Mannion has made statements in the past that you consider wrong on titanosaur phylogenetics, doesn't mean he is wrong here. I think we can both agree that Ruyangosaurus needs to be redescribed before judgement can be passed on its phylogenetic relationships. I'm aware you think it is a lognkosaur, but until it is properly scored, put in a comprehensive phylogenetic analysis, I think that is a untested hypothesis/assumption (especially since not all lognksaurs have super-wide diapophyses on their dorsal vertebrae, i.e. Mendozasaurus and Drusilasaurus). But I digress.

I'm also having a hard time seeing why you think Mannion is being vague when he says (and I quote), "Argyrosaurus can be diagnosed by five autapomorphies (marked by an asterisk), as well as a unique combination of character states: (1) medial margin of humerus forms a transversely wide ridge that projects prominently anteriorly∗; (2) midshaft of humerus extremely compressed anteroposteriorly (transverse to anteroposterior width ratio = 2.6)∗; (3) transverse width of distal end of radius only slightly greater than midshaft width (ratio = 1.3)∗; (4) radius is subtriangular in distal end view∗; (5) presence of ossified carpals; (6) extreme elongation of metacarpals (longest metacarpal to radius length ratio = 0.6)∗;(7) metacarpals II and III longest elements in metacarpus." (p. 615-616)

On Elaltitan he says, "Elaltitan can be diagnosed by an unique combination of character states, as well as one autapomorphy (marked by an asterisk): (1) spinopostzygapophyseal laminae in middle–posterior dorsal vertebrae bifurcate into medial and lateral branches; (2) dorsoventrally tall neural arch restricted to anterior half of centrum (excluding condylar ball) in anterior-most caudal vertebrae∗; (3) astragalar ascending process does not extend to the posterior margin of the astragalus; (4) presence of a calcaneum." (p. 623)

I'm sorry, but I'm having a hard time seeing how this is "vague".

Also, the arms don't have the same proportions:


Humerus: Elaltitan: 1300 mm, Argyrosaurus: 1370 mm
Radius: Elaltitan: 730 mm, Argyrosaurus: 858 mm
Ulna: (lft)Elaltitan: 827 mm, Argyrosaurus: 965 mm
Ulna: (rght)Elaltitan: 880 mm, Argyrosaurus: not preserved

H-R ratio: Elaltitan: 1.780821918, Argrosaurus: 1.596736597
H-U (both lft) ratio: Elaltitan: 1.571946796, Argrosaurus: 1.419689119
R-U ratio (both lft): Elaltitan: 0.882708585, Argrosaurus: 0.889119171
R-U (left,right)(Elaltitan only): 0.829545
H-U (left,right)(Elaltitan only): 1.477273

Only the Radius-Ulna ratios are similar, but the Humerus-radius and Humerus-ulna ratios are quite a bit different.

I also find it odd that you think the holotype Argyrosaurus specimen and the Elaltitan specimens are of differenet ontogenetic stages. Based on what? The scapula is not preserved with the holotype specimen so you can't compare the ontogeny of the two specimens without a histological analysis (which has not been done AFAIK). Size is very misleading when it comes to ontogeny (as Triceratops specimens show), and smaller specimens of the same species can actually be more mature than larger specimens.

Their arm proportions are actually different (see my comparisons above). Another interesting difference between them, in Elaltitan, "At midshaft,the humerus has a transverse to anteroposterior width ratio of just under 2.0" (p. 629) whereas in Argyrosaurus it is "At midshaft, the humerus is strongly compressed anteroposteriorly, and it has the highest transverse to anteroposterior width ratio of any known sauropod (2.64 [measured on the anteroposteriorly thicker medial side]; see Table 1)[...] we regard the extreme condition in Argyrosaurus as an autapomorphy of the genus."

BTW, the tarsus autapomorphy for Argyrosaurus is not used to distinguish it from Elaltitan, but from other titanosaur sauropods (i.e., it is currently diagnostic when compared to other titanosaurs for which it can be compared).

There are other differences between Elaltitan and Argyrosaurus in the morphology of the radius and ulna such as:

* distal end of radius is mediolaterally expanded in comparison
to the shaft - ratio of 1.7 in Elaltitan compared to 1.3 in Argyrosaurus

*proximal end transverse width to ulna length ratio of 0.45,and differing from the more gracile morphology seen in Argyrosaurus ratio of 0.34

Mannion lists other differences that I will not go into here, but I hardly think they and the ones I have mentioned are "vague".

One point that I might concede is that it is possible for arms to change proportions through ontogeny, this is known to be the case in Alamosaurus for instance, where the humerus gets proportionally longer. However, the other differences in the ratios are not so easily chalked up to ontogeny. In any case, I think the case for taxonomic distinction has been proved beyond a reasonable doubt with the current amount of evidence available.

I also think it is interesting that you think that Elaltitan could morph into Argyrosaurus gaining an autapomorphic medial ridge on the humerus, but you feel that fenestration in Triceratops-Torosaurus is impossible. In other words, Triceratops and Torosaurus share every diagnostic feature except their frills, whereas Elaltitan and Argyrosaurus differ in every diagnostic feature that we can compare them on.

As for the name, the paper says, "EtymologyElal (ee-lal), the creator god of the Tehuelche people of Chubut Province; titan, giant in Greek mythology. Specific name in honor of Miguel Lillo, for his contribution and legacy to natural sciences in Tucuman." So no airline, AFAIK.
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