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DrScottHartman's avatar

Don't mix and match your Tyrannosaurus?

I mentioned awhile back that I was overhauling my specimen-based T. rex comparison chart (and perhaps adding to it). This is a quick update showing the differences between the type specimen (CM 9380) and the famous New York specimen (AMNH 5027). These were the first two specimens (of any completeness) ever found, and because they are fairly similar in size they have been combined to create the traditional T. rex mounts you see in many museums world wide.

With a century of hind-sight available I'm not convinced this was a good idea. While it's obviously hard to compare much between the two animals (the AMNH specimen lacks any limb material, while the Carnegie specimen is missing almost all of the neck and tail) they still show off some interesting differences. The pelvis of the type specimen really does come across as rather robust (the pubis seems to match Sue's in heft), but oddly the skull appears to be slightly shorter (based primarily on the lower jaw),

This could easily be chalked up to individual variation (compare your average NBA player with Jay Leno and you see far greater diversity), but it does emphasize the importance of looking at individual specimens in a species, rather than assuming you can mix and match them at will.

P.S. I know many of you care about size estimates. Hopefully it's clear that we have no way of knowing which of the two specimens was actually larger, given how much is missing. I gave a very slightly longer estimate to the CM specimen because that's what I come up with, but that's assuming a tail that is similar in proportion as the AMNH specimen, and as we just discussed that's not necessarily a safe assumption.
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Pyranniosaurusrex44's avatar
yeah tyrannosaurus!!!T. rex Roar Icon 
kirkseven's avatar
if the tail on CM 9380 was more similar to that of sues how long would the total length be?
Paleo-reptiles's avatar
ribs in AMNH 5027 is more rubust than Sue or this issue just related to our art skill?
DrScottHartman's avatar
That is how they are portrayed in the AMNH monograph. I agree it seems odd, but I haven't been back to the AMNH since I did the skeletal. But maybe if it turns out that there really are two morphs of T. rex one will have robust ribs (or maybe Osborn just got carried away).
Paleo-reptiles's avatar
Wonderful! Thank you for share us these beautiful scientific art!
randomdinos's avatar
I do realize why Paulian-style lumping such as Velociraptor= Deinonychus or Apatosaurus=Barosaurus=Amphicoelias make little sense, but what about things like Velociraptor=Tsaagan or Tyrannosaurus=Tarbosaurus? They seem to have less variation between the genus than things like Panthera onca/tigris, which are in the same genus, and two very similar genus being lumped into one has happened before; Megapnosaurus=Coelopysis, IIRC.
DrScottHartman's avatar
That's a fine question, but one without a satisfying answer I'm afraid. So as a past supporter of Tyrannosaurus bataar here's the reality I finally came around to: there is no consistency in terms of lumping vs splitting of extant genera, so it probably makes little sense to try and pretend we are capturing some vital information signal by arguing over what is and is not a fossil genera. Heck, we're almost certainly making mistakes at the species level in some cases, either because key components are not testable (e.g. some extant species have almost indistinguishable skeletons, while others have a lot of morphological variety) or because we don't even have a properly formulated concept of how to apply it to the fossil record (what does the biological species concept EVEN MEAN once significant time is applied - does it mean that if you take an animal in a time machine backward or forward by 3 million years and they still mated that they're the same species? That's not even hypothetically testable!).

So given all that it's probably best to recognize that genera are just containers we made up that don't reflect an actual natural item. As such, I've switched to being in favor of splitting fossil taxa into more genera, because makes it harder to hide diversity when doing phylogenetic analyses (e.g. how long did Apatosaurus louisae stand in for all Apatosaurus and Brontosaurus specimens, because it had the best known skeleton?). 

For people who really do like debating generic-level taxonomy and fossils there may be a new hope - the methodology used in the Apatosaurus/Brontosaurus paper of measuring how many character differences there are between genera in order to make the splits represent character diversity is an interesting concept to pursue. Of course characters are also somewhat arbitrarily selected, and in some groups they have a strong taphonomic bias, but it does point a possible path towards a future where fossil genera represent some actual indicator of evolutionary difference.

Until then I'm content to work on everything _except_ these sorts of debates, which I leave to those really interested in them.
randomdinos's avatar
Very interesting and unexpected answer! I was partially sure you'd say that it's unreasonable to consider two species that actual paleontologists note as different to be the same or the opposite, but just how uncertain we are about the consistency of fossil genera surprised me. Well, at least until the Brontosaurus method is applied to every dubious genus/species, if that ever happens.

*secretly cheering the idea of being able to lump certain species without seeming stupid*
AJChelett's avatar
I've heard rumors of the "Sampson" specimen being possibly taller than Sue, yet still not as long. I'm currently sceptical about the accuracy of those claims. Do you have any thoughts or measuments on Sampson, or any future plans of drawing the specimen?
Franoys's avatar
The mount does look very tall, it's legs look huge when compared to the full body length and skull size.…

You can see it just by eyeballing a photograph of the specimen, but it can be missleading since the pose of the legs it's very upright and I don't know how much of the leg belongs to the specimen.
DrScottHartman's avatar
That mount is tall because the knee is hyperextended, making the leg taller than it could have been in life.
DrScottHartman's avatar
That looks pretty spot on to me.
DrScottHartman's avatar
I've got nothing on Sampson, outside of some marketing photographs that were sent out years ago. But without knowing which bones are real and which ones have been reconstructed it's pretty much a crapshoot right now.
AJChelett's avatar
Well, that's unfortunate. It seems to be a very excellent find, yet there's also no information on the specimen anywhere.
DrScottHartman's avatar
It's very unfortunate - I hate knowing there is data available that isn't currently accessible. Hopefully that changes soon!
thedinorocker's avatar
And this is Why I don' t trust an isometrical 8% Giganotosaurus larger than the holotype or a gigantic Spinosaurus based on Dal Sasso specimen (I saw than rostrum many time) or a oversized (and frammentary) T.rex.

Ps- Well donnedonne
MesozoicMasacre's avatar
Are you going to make full skeletal reconstructions like you did with Stan and Sue? Or are you just going to leave at as it is?
DrScottHartman's avatar
BTW, I don't advise anyone (myself included) to make a "rigorous" skeletal without first product a fully restored version. It's too easy to make basic errors in where the bones go otherwise.
DrScottHartman's avatar
I already made them. Whether I post all of them is another issue.
Is it true that you get a free cast of AMNH 5027's skull when you apply for a museum license?
DrScottHartman's avatar
The basic license comes with the plaque-mount Coelophysis and a 5th generation cast of the London Archaeopteryx. It's only sustaining members that also get the AMNH 5027 skull cast ;)
SaberToothedCatsFan's avatar
Are there any weight estimates ??
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