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Submitted on
March 11, 2012
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Brachiosaurus altithorax hi-fi skeletal by Paleo-King Brachiosaurus altithorax hi-fi skeletal by Paleo-King
Brachiosaurus altithorax

Family: Brachiosauridae (intermediate position)
Time: Late Jurassic, Kimmeridgian-Tithonian epochs, ~150 mya
Location: Morrison Formation (brushy basin member), Colorado, Wyoming and Utah, USA

*Now upgraded with additional referred specimens; skull also updated* 


The original, classic namesake of the brachiosaur family, and for a long time the biggest dinosaur known (though much of what was assumed about it was actually based on its more complete African cousin Giraffatitan brancai ). First found in 1900 and described in 1903, Brachiosaurus altithorax is based mainly on the type specimen FMNH P 25107, which comprises a partial dorsal column, hip material, a humerus, femur, coracoid plate, and a rib. Despite being downright colossal, this animal, roughly 80 feet long and 37 tons, was still not fully grown.

More recently several isolated bones and a skull (long forgotten in a Smithsonian museum vault) have turned up, which may belong to Brachiosaurus or at the very least, to a closely related genus. There is also neck material from the same quarry at the Smithsonian, which may belong to this individual. The skull is originally from a smaller individual about half the size of the holotype, but judging by other sauropods known from more complete growth series, the proportions of the skull probably didn't change much as the animal grew up. There is also a partial Morrison brachiosaur skull at Yale (just the maxilla and dentary) which was discovered by O.C. Marsh in the late 1800s, well before the description of Brachiosaurus - Marsh incorrectly used this same set of jaws as part of the basis for his bizarre and fanciful "Brontosaurus" skull reconstruction:…… .

The headless juvenile sauropod skeleton known as "Toni" was initially mistaken for a diplodocid, and commercial fossil casting companies still reconstruct it as such, though in 2010 it was redescribed as a brachiosaur in a phylogenetic analysis by Carballido, et. al., falling in most closely with B. altithorax. Indeed the robust dorsals, short sacral spines, and front-heavy ilia of "Toni" are remarkably similar to those of Brachiosaurus, and rather different from what one sees in Diplodocus and Apatosaurus, even in juvenile specimens. The long-shafted scapula is also very brachiosaurid in appearance.

The large Dry Mesa Quarry brachiosaur material discovered by Jim Jensen in the 1980s (including the huge"Ultrasauros" shoulder blade and another, less complete one) is not included here, as it probably belongs to another genus. Other recently found remains, like BYU 13023 (Curtice and Stadtman, 2001) and the LACM humerus, are probably from other brachiosaurid taxa. The Potter Creek specimen, one of the largest North American brachiosaurs on record, appears to belong in Brachiosaurus at least on the generic level. The dorsal vertebra of this specimen was heavily restored in plaster by Jensen, and may have looked more similar to B. altithorax than it currently appears in its restored state. Whether this specimen was fully grown is debatable, as no shoulder material was found. There are roughly 30 or so other partial specimens referred to either Brachiosaurus altithorax or Brachiosaurus sp. though most have never been formally published. A few are even photographically documented:… . I have used some of these (scaled to the teenage holotype) to fill in the major gaps in our knowledge of B. altithorax.

Despite its iconic popularity in books and movies, Brachiosaurus is relatively rare in the fossil record, though many undescribed brachiosaur bones which may or may not belong to it have turned up recently. It appears to have been a highland animal, avoiding the low fern prairies which were dominated by Diplodocus and Apatosaurus. As a result it may be that Brachiosaurus was actually more common than the fossil record indicates, and that a disproportionately small number of Brachiosaurus got fossilized due to being far from the lowland alluvial plains of flooding rivers which preserved most dinosaur fossils. Adults were probably too large for predators to tackle, though younger individuals faced danger from Torvosaurus and large allosaurs like Saurophagnax.

*Note: NO GSP. This is an entirely original skeletal based directly off of photos of the type and referred material. Many Thanks to Mike Taylor of SV-POW for the photos of the referred BYU neck vertebrae. No Greg Paul skeletals were used or injured in the making of this far more accurate schematic 8-)


Carballido, J., Schwarz-Wings, D., Marpmann, S. & Sander, P.M. (2010) "Systematic reevaulation of “Toni“ the juvenile sauropod from the Morrison Formation" Society of Vertebrate Paleontology Abstracts with Programs, 69A

Carpenter, K. and Tidwell, V. (1998). "Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado." Pp. 69–84 in: Carpenter, K., Chure, D. and Kirkland, J. (eds.), The Upper Jurassic Morrison Formation: An Interdisciplinary Study. Modern Geology, 23(1-4).

Curtice, B. and Stadtman, K. (2001). "The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae." Mesa Southwest Museum Bulletin 8: 33–40.

Riggs, E.S. (1901). "The largest known dinosaur". Science 13 (327): 549–550.

Riggs, E.S. (1903). "Brachiosaurus altithorax, the largest known dinosaur." American Journal of Science (series 4) 15(88): 299-306.

Riggs, E.S. (1904). "Structure and relationships of opisthocoelian dinosaurs. Part II. The Brachiosauridae"…

Taylor, M.P. (2009). "A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914)." Journal of Vertebrate Paleontology, 29(3): 787-806.…
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Turtleosaurus Featured By Owner Jun 28, 2014
What's the neck length difference between Brachiosaurus and Giraffatitan just out of curiosity because on sv pow the cervical vertebrae comparison (of Sauroposeidon Giraffatitan Brachiosaurus and Angloposeidon) showed Giraffatitan vertebrae as being only 33mm longer than Brachiosaurus's  I know they state the Brachiosaurus's vertebrae as being a c10 whereas Giraffatitan is a c8 but still surely the total neck wouldn't be massively different or am I barking up the tree. I've still got a lot to learn about anatomy so just tell if I'm completely off the mark.  
Paleo-King Featured By Owner Jun 29, 2014  Professional Traditional Artist
I think you're overall on the right track. Giraffatitan's neck proportions are indeed more elongated than those of Brachiosaurus, but not by some radically high amount. It's not that Giraffatitan has a shorter neck than previously thought - quite the OPPOSITE in fact! It was longer than even Greg Paul restores it, since he inexplicably leaves out some of HMN SII and similar-proportioned specimens, and instead frankensteins HMN SI (probably a different and shorter-necked species) onto the top of the neck. But rather, what happened is that Brachiosaurus turns out to have a longer neck than most authors assumed.

Right now there is neck material of Brachiosaurus known from at least 3 specimens (4 vertebrae in total). One is a teenage specimen (the thick BYU 10th cervical that SV-POW sometimes posts pictures of) similar in size to the holotype. The second is an anterior cervical from BYU that's from a smaller animal. The third is a specimen at the Smithsonian/USNM (two vertebrae) which is even smaller than that one! Since none are fully grown, it's possible that even the rather long neck in my skeletal here (which is based on both specimens) may actually have been even longer on the holotype, not to mention an adult like perhaps the Potter creek specimen. It is known that adult sauropods tend to have proportionally more elongated necks than half-grown ones. But how rapid and extreme the change was, it hard to say. It may be that since the neck proportions don't seem to change much between the USNM and the anterior BYU cervicals, that perhaps adults didn't elongate that radically in a final growth spurt.

All the same, even these immature specimens indicate that the neck was already very long by the time the animal was around 50% adult size. Much more elongated than the hypothesized "camarasaur-like neck proportions" that many authors have been bandying about without actually studying the bones. And the large BYU vertebra is already holotype-sized so I doubt the adults would have much more extreme proportions than that. That would mean my skeletal is accurate for adult Brachiosaurus proportions too. It does rival Giraffatitan for neck length more than, say, Mike Taylor's version... So it depends on WHICH Brachiosaurus and Which Giraffatitan you compare. Assuming the holotype + the larger BYU vertebra represent animals of similar age to HMN SII, then you have teenage Brachiosaurus with a neck only a little shorter than teenage Giraffatitan.

Then again it's possible that the comparison you see may be off..... the big BYU cervical appears to have a thicker centrum than Giraffatitan HMN SII. So we may be looking at a bigger Brachiosaurus and a smaller Giraffatitan. And even then, the Giraffatitan has a longer neck. If both animals had the same centrum thickness, there would be a greater difference in neck length. But if you scale the two animals to the same overall length (not to centrum diameter) then the Brachiosaurus will have less extreme neck length, a bigger tail and longer belly, and bigger centra in both cervicals and dorsals. So that's why simply comparing vertebra length can be misleading, the centrum thickness could indicate rather different-sized animals. Giraffaittan has shockingly small centra in its dorsals. You get the idea that the top-heavy neural arches/zygapophyses are taking most of the weight, especially in the last few dorsals. D9 and D10 of HMN SII actually exhibit a very bizarre "lordosis" kink in their articulation which appears totally natural and makes the joint much stronger at the zygapophyses, to reduce stress on the centrum of D9. This feature isn't found in any other brachiosaur or any other sauropod for that matter!
Cool thanks for reply. Can't wait till you finish Giraffatitan and Lusotitan reconstructions. Just thinking could the squatter, thicker Cervicals of Brachiosaurus mean it had a more flexible neck than the more elongated ones of Giraffatitan resulting with Giraffatitan having a stiffer straighter neck, or are the differences in the cervicals to slight to affect the neck physiology in any major way.  
Paleo-King Featured By Owner Jul 3, 2014  Professional Traditional Artist
Thicker cervicals do not equal a more flexible neck. Quite the opposite in fact. The most flexible longs necks in the animal kingdom are those of ostriches, which have very slender cervicals relative to body size.
Conversely, Apatosaurus has very thick cervicals (and deep) and because of this, the range of motion is far more limited - they can't turn too far without colliding with the cervical ribs or other protruding parts of another vertebra.

In the comparison of Brachiosaurus vs. Giraffatitan, it's therefore likely that Giraffatitan had the more flexible neck, but probably not by much. Both animals had long cervicals and relatively flexible necks. However, the larger BYU cerivcal, if it's Brachiosaurus, indicates that this animal had a bit less flexibility than Giraffatitan for another reason - the cervical rib's anterior portion is much thicker and therefore less flexible. Something similar is present in the cervical ribs of Euhelopus, yet its higher vertebra count makes up for this in flexibility. The real secret of flexible necks appears to be slender cervicals, and lots of them.
Turtleosaurus Featured By Owner Jul 16, 2014
I wonder why Giraffatitan and Brachiosaurus had these different adaptations with Giraffatitan obviously being more height oriented  with being a more "extreme animal" "longer arms, longer neck" and Brachiosaurus being stouter and tubbyer, probably a reflection of their environmental pressures?
Paleo-King Featured By Owner Jul 17, 2014  Professional Traditional Artist
Possibly. Giraffatitan was a more tropical-latitude animals, and it was coastal, whereas Brachiosaurus was a highland dweller. Different types of forest, different environments.

However this by itself is not enough to explain the difference. There are some Giraffatitan-like (and some Archbishop-like) vertebrae known from the Morrison formation, so Brachiosaurus was not the only brachiosaur species in the formation. In fact there were probably at least 3 or 4 others, obscure but distinct from each other.

The difference in proportions may be explained by the fact that Brachiosaurus and Giraffatitan were from different branches of Brachiosauridae to begin with. And the Archbishop and some of the North American forms (including the shoulder material "ultrasauros" perhaps) belong to yet a third, narrow-bodied branch. And Astrodon/Pleurocoelus, Abydosaurus, and Cedarosaurus, may form yet another branch, which only became common in the Cretaceous.
thedinorocker Featured By Owner Jun 21, 2014
Great work Nima!
Now I am waiting for the updated Giraffatitan (after your blog post about G.brancai dorsals).

Ps- Can I have your e-mail adress to send you "my" M.sinocanadorum (it s finished)?
Paleo-King Featured By Owner Jun 22, 2014  Professional Traditional Artist
Yes. It's

Thanks! I'm updating both Giraffatitan and Lusotitan. Giraffatitan is planned to be a multi-view. And yes the dorsals are even steeper than before. This animal was so steep the only logical conclusion is a vertical neck.
Dontknowwhattodraw94 Featured By Owner Jun 20, 2014  Hobbyist Traditional Artist
This really nice, didn't know Brachiosaurus grew that big. I always thought he wasn't taller than 13 metres. 
About the juvenile specimen: are there any estimates about how old he was? 
Paleo-King Featured By Owner Jun 20, 2014  Professional Traditional Artist
Not yet. There hasn't been much histological work done on the bones to see its age. My best guess is that "Toni" was only 1 or 2 years old max.

Most "official" brachiosaur height figures are too low. It's because they were calculated decades ago based on outdated thinking - with the dorsals not tilted high enough, or a droopy neck, like you see in old books from the 1950s.
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