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Just as predicted six years ago by Andcrea Cau in his blog, and four years ago by user :iconpalaeozoologist: , "Amphicoelias fragilimus" is now redescribed as a new rebbachisaurid taxon;  Maraapunisaurus fragillimus by no less than the renowned doctor in paleontology Kenneth Carpenter, the same sciencist that catapulted the 60 meters diplodocid version to fame in 2006.

The publication suggests that the morphological characters of AMNH 5777 show shared apomorphies (defining characters) with rebbachisauridae, and that thus should be considered to be part of said group. Going by this, Maraapunisaurus fragillimus would be the largest and oldest member known of this peculiar family; perhaps meaning that the clade could have originated in what today is north america in the upper Jurassic, archieving practically wordlwide distribution by the early cretaceous (exceptuating Asia and Antartica).

Carpenter2018-amphicoelias-fragillimus-is-maraapun by FranoysFragillimusrebbachisaurid by Franoys


To the left (shown above; original drawing by Cope (1878) labeled in Willson et al (2011). To the right, it compared with dorsal vertebrae of other rebbachisaurids (Rebbachisaurus grasbae and Histriasaurus boscarollii).

Maraapunisaurus fragillimus is known from a single partial neural arch of massive dimensions if we go by Cope's measurements (total elevation of neural arch preserved, 1500 mm; elevation of posterior zygapophyses, 585; transverse expanseof posterior zygapophyses, 190; vertical diameter of base of diapophysis, 390) . The older reconstruction by Carpenter of the complete vertebra was 2.7 m tall, and newer one is 2.4 m, just twice the height as the preserved dorsal vertebra of Limaysaurus tessonei (120 cm). This leaves us with an animal 2x the linear dimensions of Limaysaurus tessonei and 8x (2^3) it's mass asuming perfect isometry, although the distance between the neural canal and the postzygapophysis seems larger in proportion in Maraapunisaurus fragillimus than in Limaysaurus, meaning that this discrepancy could have been smaller and not a direct translation on how the vertebral heights correlate.

Asuming perfect isometry in reconstructed vertebral height, the length of Maraapunisaurus fragillimus would be between 28.6 and 30 m (going by the skeletal restorations of Limaysaurus by :iconpalaeozoologist: and Gregory S.Paul) and the mass between 56 and 61.6 metric tonnes ( mass of Limaysaurus is 7 t going by Greg Paul's estimate in the priceton field guide 2016, 7.7 t going by :iconspinoinwonderland: GDI of a slightly edited :iconpalaeozoologist: Limaysaurus restoration using my matlab script (specific gravities applied are 0.7 for the head, 0.6 for the neck, 0.9 for the torso, 1 for the tail and limbs).

Link to Limaysaurus GDI estimate.
i.imgur.com/Gkn1P7o.png

Diagram from Carpenter 2018, showing relative dimensions between the newer and the older version of his reconstruction of AMNH 5777. Old estimate involved a 2.7m high vertebra using a D.carnegii like body plan:

Amnh 5777 by Franoys

There is a posibility that the neck was slightly more elongated than what isometry predicts, as the neck length in several neosauropods scale with torso dimensions to the power of 1.35 as described by Parish (2006). This augments the posible linear dimensions up to 32 m, with mass increasing only slightly, as sauropod necks are not very massive in proportion and heavily pneumatized.

What happens with Amphicoelias as a whole, and with Amphicoelias altus specifically?


This would make it so M.fragillimus stops being closely related to Amphicoelias altus, and thus Amphicoelias altus survives as their own genus and species. Cope came to this conclussion in 1878 since A.altus was the only diplodocoid he had named, and while they still have the general resemblance expected in two diplodocoid taxa, M.fragillimus shares at least 2 apomorphies with all of rebbachisauridae, and other characters in common with some of them. Amphicoelias altus has been recovered within apatosaurinae according to Tschopp & Mateus 2017 analysis, and it's femoral dimensions (177 cm maximum length as indicated by Osborn & mook 1921) are close to that of B.louisae specimen CM 3018: with femoral length 178.5 cm and an estimated mass 22.4 tonnes by GDI analysis by myself using Scott Hartman's skeletal with a dorsal view by Gregory S.Paul ;Greg Paul's own estimate for this taxon is 18 tonnes) ,so despite the genus surviving, it now doesn't hold any record holder in terms of size.

Is M.fragilimus the largest sauropod dinosaur (and thus, largest terrestrial vertebrate) ever found according to this information?


Mazzeta et al 2004 proposed a mass of 73 t for Argentinosaurus huinculensis based on a referred femoral shaft using regression equations; an estimate close to a GDI done in :iconrandomdinos: 's Argentinosaurus reconstruction (in which I collaborated), that yielded between 71.4 and 75.4 metric tonnes depending on varying the ribcage width between plausible values. Patagotitan mayorum as described in Carballido 2017 could be slightly smaller than Maraapunisaurus fragillimus, with a convex hull +21% model of 55 t, though the maximum model (reconstructed with much more soft tissue than that applied to Limaysaurus mass estimates) yielded up to 77 tonnes.

Here is a comparison of M.fragilimus and A.huinculensis: (Argentinosaurus huinculensis by :iconrandomdinos:, Maraapunisaurus fragillimus silhouette by :iconrandomdinos: using Limaysaurus tessonei skeletal by :iconpalaeozoologist: as a base)
Fragilimuscomp by Franoys

Here is the great SVPOW post on the matter:

svpow.com/2018/10/21/what-if-a…

And the original publication, discussing certain matters much further than I and SVPOW members did.

www.utahgeology.org/publicatio…

Congratulations are in order for fellow deviantartist :iconpalaeozoologist: that has actually been acknowledged in the publication. 

Here is the original post that he made in this very same site:

Was Amphicoelias a rebbachisaur?Update (10/22/18): Dr. Ken Carpenter has recently published a new paper supporting the view below (and cites me favorably), but I would also be remiss to not recongize Dr. Andrea Cau for having thought up this idea 2 years before me. Sadly, he was not cited in Carpenter's paper. He and I both were unaware of Cau's work.
The last time I wrote about the size of Amphicoelias, I still used Diplodocus as a comparison. One of the comments that was made was that my size estimate was likely wrong, as Amphicoelias was probably a basal diplodocoid, not a diplodocid proper. After a little investigation, it turned out that two phylogenetic analyses have been published that included Amphicoelias, and both found Amphicoelias to be a basal diplodocoid. Whitlock (2011) was


References:

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:iconchristina1969:
christina1969 Featured By Owner Nov 5, 2018
"Maraapunisaurus fragillimus by no less than the renowned doctor in paleontology Kenneth Carpenter, the same sciencist that catapulted the 60 meters diplodocid version to fame in 2006."

Actually, Carpenter estimated it to be 58 meters long in 2006, not 60. It was Gregory S. Paul who estimated it between 40 and 60 meters in the 90's.
Reply
:iconthe-nerdinator:
The-Nerdinator Featured By Owner Oct 26, 2018
Apatosaurus louisae hasn't been reclassified into Brontosaurus, on what basis do you say that?
Reply
:iconfranoys:
Franoys Featured By Owner Oct 27, 2018  Student Digital Artist
It's based on the abstracts of SVP 2016 (page 19) in which they speak about how it ends more related to Brontosaurus than to Apatosaurus in a newer anaylsis, though it is not published yet. Personally I wrote it almost unconciously. cdn.discordapp.com/attachments… .
Reply
:iconthe-nerdinator:
The-Nerdinator Featured By Owner Oct 29, 2018
Unpublished, you say? Explains why I couldn't find why half of DeviantArt just suddenly decided to use B. louisae.

In all honesty, I'm gonna stick with A. louisae until this paper gets published and other scientists weigh in on it. Remember, just because it seems like a good idea doesn't mean it's the best idea, and this abstract doesn't go into detail about why they made the change. So until they explain what anatomical basis they used to reclassify A. louisae, I'm not going to use it.
Reply
:iconanomally:
anomally Featured By Owner Oct 24, 2018
The dream of a 100 ton plus sauropod is over:(. Maybe we are seeing the plateau of land based animal size limit, at around Argentinosaurus?
Reply
:iconmezothebugfield:
MezoTheBugfield Featured By Owner Oct 30, 2018
Cough BYU 9024 Cough
Reply
:iconalmostthere99:
Almostthere99 Featured By Owner Oct 23, 2018
8/10, not enough big.
Reply
:iconalmostthere99:
Almostthere99 Featured By Owner Oct 23, 2018
yes, enough big.
Reply
:iconmezothebugfield:
MezoTheBugfield Featured By Owner Oct 23, 2018
It traded it's size for a higher credibility of existing. Fair trade, i guess. Either way, if it does exist, It being a Rebbachiosaurid, and one that big at that is cool awesome epic
Reply
:icondinopithecus:
Dinopithecus Featured By Owner Oct 23, 2018
Okay, so we still have a pretty big animal, but technically holds no records for largest sauropod (let alone largest animal) ever anymore. I can live with that. Not that I have an option lol.
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:icon105697:
105697 Featured By Owner Oct 23, 2018
Technically, its the tallest sauropod (and thus dinosaur) by hip (lower back?) height.
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:iconacepredator:
acepredator Featured By Owner Oct 24, 2018
What?!
Reply
:icon105697:
105697 Featured By Owner Oct 24, 2018
Shows right there on the chart. The lower back/hip height is 7 meters or so, which is taller than the lower back/hip height of any dinosaur.

Argentinosaurus still outweighs and outreaches it by a noticeable margin though.
Reply
:icondinopithecus:
Dinopithecus Featured By Owner Oct 24, 2018
That's true (7 meters? Holy shit). I was only thinking about body mass when I wrote that.
Reply
:iconmajestic-colossus:
Majestic-Colossus Featured By Owner Oct 23, 2018
Yeah. 7 meters tall on the back. It dwarfs pretty much any sauropod when it comes to this. I can't wait for the French monster to be described, maybe it was even taller than that (it seems unlikely, but who knows?).
Reply
:icontyrannosaurusprime:
TyrannosaurusPrime Featured By Owner Oct 23, 2018
"Mr. Cope, I don't feel so huge....."
Reply
:iconsaberrex:
Saberrex Featured By Owner Oct 22, 2018  Hobbyist General Artist
Whoa!
Reply
:iconmark0731:
mark0731 Featured By Owner Oct 22, 2018
"Mazzeta et al 2004 proposed a mass of 73.5 t for Argentinosaurus huinculensis..." Wasn't it 73 tonnes? I thought 73.5 tonnes is the newest GDI made by Henrique.

Reply
:iconfranoys:
Franoys Featured By Owner Oct 23, 2018  Student Digital Artist
It is just 73 t,indeed.
Reply
:iconrhe416:
rhe416 Featured By Owner Oct 22, 2018  Hobbyist Traditional Artist
The mystery is finally solved
Reply
:iconpeteridish:
PeteriDish Featured By Owner Oct 22, 2018  Hobbyist General Artist
and this is exactly why I always take sensationalistic reports on sauropods of unusually large dimensions with a grain of salt. They never hold up to scrutiny.
Reply
:iconspinosaurus14:
Spinosaurus14 Featured By Owner Oct 22, 2018
This new information is like a kick in the balls for me, 30 m? Really? Why the hell did maraapunisaurus have to be related to the proportionally shortest mfs in the sauropod kingdom? It's as if the universe intentionally did it to annoy me, at this point amphicoelias might have also been a 2 m long dromaeosaurid with an exceptionally big spinal tumor... I am not arguing agaist science here, I'm just sharing my mild disappointment
Reply
:iconforbiddenparadise64:
ForbiddenParadise64 Featured By Owner Oct 22, 2018
A suitable name for the beast at least. Now the only current challenger to Argentinosaurus’ crown is BYU 9024, depending on where in the neck it is and whether allometry is at play (and if so, how much). Even if it’s just C11 (isometric scaling means it would be 5.64 timed as massive) and there’s significant allometry, it’s hard to get it under 50 tonnes due to the sheer proportions of it. 
Reply
:iconshinreddear:
ShinRedDear Featured By Owner Oct 22, 2018  Hobbyist Traditional Artist
Andrea Cau also suggested that conclusion, even before Palaeozoologist.
Reply
:iconfranoys:
Franoys Featured By Owner Oct 23, 2018  Student Digital Artist
I didn't know when I wrote this. Now he was credited as well.
Reply
:icontherabbitwhohovers:
TheRabbitWhoHovers Featured By Owner Oct 22, 2018  Hobbyist Writer
I love how despite the 190 foot long diplodocid image now being destroyed, we still have what is basically a blue whale sized rebbachiosaurid (waaaaay bigger then any rebbachiosaurid we knew prior)
Reply
:iconmezothebugfield:
MezoTheBugfield Featured By Owner Oct 23, 2018
Blue whale sized is like, a really big exaggeration but okay
Reply
:icontherabbitwhohovers:
TheRabbitWhoHovers Featured By Owner Oct 24, 2018  Hobbyist Writer
I meant length wise, since the estimates give it a length between 99-104 feet
Reply
:iconcjcroen:
CJCroen Featured By Owner Oct 21, 2018  Hobbyist Traditional Artist
It's definitely still a big fella, at least!
Reply
:icondeinocheirusmaster:
deinocheirusmaster Featured By Owner Oct 21, 2018  Hobbyist Traditional Artist
I'm surprised that this came out just in time while I was about to draw my reconstruction of this dinosaur. I'm glad though I'm able to draw new one. Awesome journal!
Reply
:iconelsqiubbonator:
ElSqiubbonator Featured By Owner Oct 21, 2018
Alas, 200-foot 100-ton Amphicoelias, we hardly knew ye. 
Reply
:iconacepredator:
acepredator Featured By Owner Oct 21, 2018
That’s a weird, unusually large rebbachisaur...
Reply
:iconmajestic-colossus:
Still beautifully massive. Its torso was incredibly tall.

Can't wait for the french monster to be described, also.
Reply
:icondeinocheirusmaster:
deinocheirusmaster Featured By Owner Oct 21, 2018  Hobbyist Traditional Artist
French monster?
Reply
:iconmajestic-colossus:
Majestic-Colossus Featured By Owner Oct 22, 2018
www.deviantart.com/paleo-king/…

It may have been a massive turiasaurid or somphospondylan. Regardless of its affinities, the French monster is clearly among the largest dinosaurs ever found. Personally, I think it was probably bigger than Patagotitan, but smaller than Argentinosaurus.
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:icondeinocheirusmaster:
deinocheirusmaster Featured By Owner Oct 22, 2018  Hobbyist Traditional Artist
Very interesting! 
Reply
:iconacepredator:
acepredator Featured By Owner Oct 21, 2018
Giant French sauropod known from some limb bones and a huge claw. It’s big, we do not know just how big.
Reply
:iconspinoinwonderland:
SpinoInWonderland Featured By Owner Oct 21, 2018
This was an odd outcome. I do question the use of Limaysaurus as a base given that it has no overlap with the M. fragillimus (better name than Dynamoterror BTW).

I'm thinking that the centrum size estimation could probably be much larger based on the proportions of Histriasaurus, which as a more basal form than both the derived forms Rebbachisaurus and Limaysaurus, seems to be a better base.

I'm not leaving any comment on overall body size until I start reconstructing it myself.
Reply
:icon105697:
105697 Featured By Owner Oct 21, 2018
Nice post!

Finally, we can (hopefully) settle this debate once and for all.
Reply
:iconpaleop:
Paleop Featured By Owner Oct 21, 2018  Hobbyist General Artist
And just like that, the largest diplodocid sauropod has been destroyed leaving only maximum baro to surpass titanosaurs
Reply
:iconfranoys:
Franoys Featured By Owner Oct 21, 2018  Student Digital Artist
We shall see what the future holds.
Reply
:iconpaleop:
Paleop Featured By Owner Oct 21, 2018  Hobbyist General Artist
much alometry
Reply
:iconpaleonerd01:
Paleonerd01 Featured By Owner Oct 21, 2018  Hobbyist Traditional Artist
Very interesting. I’ll have to update my reconstruction then. Great post by the way. 
Reply
:iconfranoys:
Franoys Featured By Owner Oct 21, 2018  Student Digital Artist
Thank you!
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