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Re: [dinosaur] The Dueling tyrannosaurid is not, repeat is not, Tyrannosaurus



I'm sending this on behalf of my friend Jonas Hakkens, who made the skeletal reconstruction that I linked. His reply didn't come through to the DML for some reason.

"I believe you have misscaled the arms. Pete Larson has provided quite a variety of comparisons between adult Tyrannosaurus rex and the Dueling Dinosaurs specimen on his social media. Here's a link to one of them (https://twitter.com/PeteLarsonTrex/status/762721220701847552), but keep in mind that the adult Tyrannosaurus has a flexed hand so it will appear smaller than it really is. Seeing as no measurements of the specimenâs forelimbs have been made public to my knowledge, I assume you used something similar to scale the specimen. None show the humeri as being of comparable size however.Â

Judging by the scalebar included in the comparison linked, the humerus is approximately 268 mm, compared to 380 mm for Sue. Using the same method we get 204 mm for the ulna compared to 214 mm for Sue, 92mm for the second metacarpal compared to 104mm for Sue, 51mm for carpal II-1 compared to 45mm for Sue, and 49mm for metacarpal I compared to 65 for Sue (measurements of Sue are from Brochu, 2003). Now going back to PIN 552-1 and PIN 552-2. The humerus of PIN 552-2 is 143 mm compared to 255 mm for PIN 552-1, the radius is 108 mm compared to 115 mm for 552-1, the second metacarpal is 45 mm compared to 60 mm for 552-1, phalanx II-1 is 45 mm compared to 35 mm for 552-1, and finally carpal I-1 is 35 mm compared to 38 mm for 552-1 (measurements from Maleev, 1974 and the Theropod Database). These two comparisons line up remarkably well.Â

Friendly greetings,Â
Jonas Hakkens"

On Sat, Nov 21, 2020 at 7:14 PM Gregory Paul <gsp1954@aol.com> wrote:
Good old 552-2 which I have seen is part of my Tarbo growth series in the Field Guide 2. Arm and hand is of normal and small tyrannosaurid proportions both relative to rest of animal (around 2/3s to 3/4s femur length) and in absolute terms relative to large forelimbs of adults . It is no where close to the enormous size of the Bloody Mary arm.Â

The arm of BM is about the same and quite large size relative to the legs of Drypotosaurus -- which is similar in over all size to BM -- at ~1.15 times longer than the femur, which further suggest BM might have been nontyrannosaurid product of Appalachia rather than an Asia-Laramidia tyrannosaurid. The Appalachia tyrannosaurs seemly being modest sized beasts with big two fingered arms. Then they ran into the western beasts with their whimsy arms when he seaway regressed.Â

I should have mentioned that my figure of skeletals is to the same scale. And please note that while the humerus BM and Sue are about the same length which itself is peculiar, the lower arm and hand of BM is about 50% longer in absolute size than that of Sue which overall is about 60% longer in total length, so the relative size shift would amount to a factor of about 2.5. I am not aware of any amniote in which a major appendage undergoes such severe absolute and relative shrinkage in the last stages of growth, much less in any dinosaur. If anyone knows otherwise please let us know. Â


-----Original Message-----
From: Tyler Greenfield <tgreenfield999@gmail.com>
To: Gregory Paul <gsp1954@aol.com>; dinosaur-l@usc.edu
Sent: Sat, Nov 21, 2020 7:17 pm
Subject: Re: [dinosaur] The Dueling tyrannosaurid is not, repeat is not, Tyrannosaurus

Have you ever looked at the arms of the juvenile TarbosaurusÂspecimen PIN 552-2 (former holotype of "Maleevosaurus')? The proportions look fairly similar to Bloody Mary to me.

Skeletal reconstruction of PIN 552-2:

On Sat, Nov 21, 2020 at 8:44 AM Gregory Paul <gsp1954@aol.com> wrote:
With the good news that the Dueling Dinos are now in an accredited museum that got me wondering if it is yet possible to verify the claim by Peter Larson that the arms and hands of the gracile specimen are so over sized that they prove it cannot be a juvenile Tyrannosaurus. I don't care one way or the other what the situation is, but would like to see the issue finally put to rest one way or another. And there are the Ânecessary images of the specimen that clearly show the forelimbs as perÂhttps://www.theguardian.com/science/2019/jul/17/montana-fossilized-dueling-dinosaurs-skeletons-dino-cowboy (best photos are further down in article).Â

The arms and hands are amazingly HUGE. Far larger relative to the rest of the animal than those of any known tyrannosaurid. The fingers broadly match the toes in robustness -- at first looking at one of the photos I thought they were toes until I realized bothÂactualÂfeet are near the pelvis and my mind boggled. And in absolute terms they are larger than those of adult Tyrannosaurus as my spiffy skeletals show (atÂgspauldino.com/tyrannoskels.jpgÂtheÂadult Tyrannosaurus is Sue, the gracile form is a combo of Jane and Dueling, the smaller former being scaled up ~15% to the possible adult latter which is said to be 22 ft long, humerus/femur ratio as per Dueling). Of course it is not possible for a majorÂappendage to actuallyÂshrink with growth so the Dueling beast cannot be a juvie Tyrannosaurus. There is no more reason to continue to assert that graciles are juv Tyrannosaurus justÂbecause the first are small and lived in the same habitat, than there is to say gracile Alioramus is a juv Tarbo when the first is small and lived in the same habitat. That issue is totally settled.Â

Note that in comparison a juvenile Gorgosaurus is nearlyÂidentical to the adult form except for some modestÂallometric shifts (the specimens are the ones at the AMNH).ÂMuch the same is true with the Tarbosaurus growth series in myÂPrinceton Field Guide. Dueling and Jane areÂso much more different from Tyrannosaurus that ontogeny isÂclearlyÂnot involved.Â

There being nothing else like them in known tyrannosaurids, the super sizedÂarms of Dueling were an apparently late appearing radicalÂdeparture from the tyrannosaurid norm, and leaves it anatomically and very possibly phylogeneticallyÂfurther from Tyrannosaurus than is Tarbosaurus, so unlike the latter Dueling cannot possibly be in the same genus, much less a juvenile of the giant. OneÂpossibility is that small armed tyrannosaurids were a feature ofÂAsia-Laramidia, the long arms of Appalachia as per Dryptosaurus (which may have had only two long fingers), and they meet as theÂseaway regressed. Maybe the Dueling specimen is not in Tyrannosauridae. Â

It has been bothering me that papers have been publishedÂsupposedlyÂproving that Nano is a juvie Tyrannosaurus when Larson has been warning that the Dueling specimen's forelimbs are too large for it to be a juv Tyranno. Remember that patience is a virtue. Â

All that said, it is not certain that the Dueling Nano is N. lancensis. As far as I know the Dueling specimens are from low in the Hell Creek, the N. lancensis may be from the middle of the Lance and hundreds of thousands of years younger, and could easily be a different species and maybe genus. Very hard to tellÂbecause the Nano type is just a seriously crushed skull with no arms. Nor am I sure what level of the Hell Creek that Jane is from, and its arms although they seem bigger than the tyrannosaurid norm do not appear to match those of the otherwise onlyÂmarginally bigger Dueling specimen. (If anyone has solid info the the levels of the Hell Creek and Lance these specimens come from please let me know). There could have been a whole lot of Nano evolution going on during the 0.7 to 1.5 million years that the Hell Creek/Lance et al. existed (it is not yet possible to accurately date the time span of the twoÂformations) -- I amÂnot even sure the graciles made it to the end of the Cretaceous.ÂLikewise Tyrannosaurus probably consists of two or three species, T. rex being confined to the top and probably including Scotty, and not including Sue or poor Stan. To put it another way, T. rex is veryÂunlikely to be the sole late Maastrichtian upper plains tyrannosaurid in multiple ways. ÂÂ