Underrated giant theropods

[Cross]

Created a thread specifically for non-mainstream giant members of theropoda that never get enough love.

To start tings off, why is it a poplar notion that Acrocanthosaurus is "slightly" smaller than Tyrannosaurus?
I know, FMNH PR 2081 and AMNH 5027 are probably several hundred (to thousand) kilograms heavier than NCSM 14345, but aren't the other Tyrannosaurus specimens like MOR 555, BHI 3033, and CM 9380 that are just in overlapping range in terms of length and weight? Wouldn't that make Acrocanthosaurus "comparable in size to T. rex"  as opposed to "slightly smaller"?

And can anyone shed some light on the big Avetheropod femur IPHG 1912 VIII 69 that (according to Mortimer) probably doesn't belong to either Bahariasaurus or Deltadomeus ? Likely from a completely different giant tetanuran.

[creature386]

There is no consensus on the average size of Tyrannosaurus. There were in fact debates about that on this forum. I guess most say that because they see the average Tyrannosaurus' size closer to 7 than to 6 t.

[theropod]

NCSM 14345 is comparable to, or slightly smaller than the average T. rex. But that’s also the biggest Acrocanthosaurus that I know of, so the species as a whole is slightly smaller based on what we have. Not as much smaller as commonly imagined, of course.

[blaze]

AMNH 5027, MOR 555, BHI 3033 and CM 9380 are all very similar in size and they seem to have at least a tonne on Fran if not more, it's very similar to the comparison of Sue vs MUCPv-CH-1, Fran is as long as them and looks comparable from the side but is more slender and narrower.

Yes I've heard of Chilantaisaurus, it is not as big as the other giant theropods you mention but a giant theropod nonetheless, it also has big arms.

[Deleted]

Suchomimus is often underrated in mass estimates. Just look at it, this thing is Tyrannosaurus-sized! Ok, it looks to be a bit below an average Tyrannosaurus and on par with small Tyrannosaurus, but it still falls within Tyrannosaurus' known size range...

Put it in a size comparison, and somebody tell me with a straight face that this thing is only as massive as a slightly-above-average Allosaurus fragilis. It's not really that slender either, googling "suchomimus front view" or "suchomimus skeleton front view" shows you that it's actually pretty bulky.

[theropod]

Some quick area measurements based on Hartman’s T. rex comparison and mass estimates based on the assumption of the width scaling in accordance with the lateral area (mass = (area/sue_area)^(3/2)*sue_mass). If any of you want to check, I used the file on deviantart and copied the image straight from my browser into GIMP after magnifying it, then removed the background, labels and watermark and colored everything that remained (i.e. the silhouettes themselves) black.

FMNH PR 2081 (12.3m, 8.4t)
area: 88847px [1.00]
mass: 8.4t [1.00]

CM 9380 (11.9m -> 7.6t)
area: 82821px [0.93]
mass: 7.6t [0.90]

AMNH 5027 (11.8m -> 7.3t)
area: 78437px [0.88]
mass: 7.0t [0.83]

BHI 3033 (11.3m -> 6.5t)
area: 75646px [0.85]
mass: 6.6t [0.79]

Jane (6.5m -> 1.2t)
area: 21048px [0.24]
mass: 1.0t [0.12]

Maybe that helps. I’ve added the isometrically scaled mass estimate (based on TL) as well, for comparison, and generally they weren’t that far apart (though stan "looks" slightly bigger than its length implies, while AMNH and Jane look a bit smaller).
This is just a more objective measurement of how big they look relative to each other in this comparison (i.e. how much area they cover). But it would be interesting to test it against blaze’s GDI.

[Deathadder]

Animals like very large megalosaurids and chilintarasaurus are pretty underated.

[blaze]

theropod
I'm incredibly unproductive, so far I've only corroborated Hartman's GDI of Sue and MUCPv-CH-1 and done that of CM 9380, 7,600kg.

[theropod]

Stacks up pretty well then, looking forward to whenever you do the rest. Doesn't look as if you were unproductive, I'd imagine it is quite a lot of work.
Based on Hartman's skeletals I definitely think Stan was overestimated by about a ton in Bates et al.

[blaze]

Is not that much work, what I mean is that I said I'll do them two days ago but I didn't start until last night haha, well, Stan's ready, 6,850kg. That's midway between the published volumetric estimates, main differences with that of Bates et al are the head and thighs while compared to that of Hutchinson et al. the main differences are the neck and tail.

[creature386]

Your estimates are pretty much what I get when combining Bates et al.'s estimate with Hutchison et al.'s density (the result are like 6.7 t). So, it indeed seems to be a midway.

P.S. You listed Hutchinson et al. twice, you may want to fix that.

[blaze]

Fixed! haha

[Deleted]

I think CM9380 would have been quite a bit less massive than the FMNH PR2081-based estimates here, I may just be eyeballing but it looks significantly narrower proportionally than Sue.



From this angle, it looks as if the width is roughly half of the torso depth, I guess it would probably be between ~60-70% of torso depth if viewed directly from the front. FMNH PR2081 seems to have a torso width more than ~85% or so of it's torso depth.

[spinodontosaurus]

I can only assume that the difference is down to rib articulation, maybe even how the ribs themselves are reconstructed seeing as CM 9380 is known from only a couple of ribs to begin with. The difference definitely isn't that dramatic in the 3D skeleton scans in Hutchinson et al.

In fact a while back I made a very crude estimate of CM 9380's weight partially using those scans and also Hartman's skeletals. Basically, Hartman's CM 9380 is ~97% the size of Sue in tip-to-tip length, and I used this scaling factor for depth too (because at equal tip-to-tip lengths his two skeletals are almost identical in depth). If I applied it to width as well it would result in an overall size ~90% as big as Sue, or roughly 7,600 kg. But I decided to base width off of the scans in Hutchinson et al. instead, and from that I estimated CM 9380's chest to be 92% as wide as Sue's. If I combined this with the estimated ~97% for both length and depth, I got an overall size ~86% as big as Sue, or roughly 7,200 kg.

blaze what are you basing the width of your GDI models off of?

Also I love how in a thread about "underrated giant theropods" meant to specifically focus on theropods not named Tyrannosaurus, Giganotosaurus etc. we are discussing GDI mass estimates of various Tyrannosaurus specimens. Oops.

[Deleted]

Jul 18, 2015 13:39:08 GMT 5 spinodontosaurus said:

I can only assume that the difference is down to rib articulation, maybe even how the ribs themselves are reconstructed seeing as CM 9380 is known from only a couple of ribs to begin with. The difference definitely isn't that dramatic in the 3D skeleton scans in Hutchinson et al.

In fact a while back I made a very crude estimate of CM 9380's weight partially using those scans and also Hartman's skeletals. Basically, Hartman's CM 9380 is ~97% the size of Sue in tip-to-tip length, and I used this scaling factor for depth too (because at equal tip-to-tip lengths his two skeletals are almost identical in depth). If I applied it to width as well it would result in an overall size ~90% as big as Sue, or roughly 7,600 kg. But I decided to base width off of the scans in Hutchinson et al. instead, and from that I estimated CM 9380's chest to be 92% as wide as Sue's. If I combined this with the estimated ~97% for both length and depth, I got an overall size ~86% as big as Sue, or roughly 7,200 kg.

blaze what are you basing the width of your GDI models off of?

Also I love how in a thread about "underrated giant theropods" meant to specifically focus on theropods not named Tyrannosaurus, Giganotosaurus etc. we are discussing GDI mass estimates of various Tyrannosaurus specimens. Oops.

It's because of the Acrocanthosaurus thing brought up in the OP.