STL Science Center

STL Science Center

30 July 2011

Pictures and differences

©John Conway
Important in distinguishing the difference between B. altithorax and G. brancai are the illustrations of artists which are based upon the skeletal reconstructions of each animal. Though I have not put any illustrations of Brachiosaurus altithorax up to critique, the one above should suffice to act as a model against the other images contained herein. The first image I've used is John Conway's Giraffatitan to exemplify the enormous neck of the animal. B. altithorax also has a large neck, but Conway's Giraffatitan shows how thick and long the neck of the animal was due to the sheer size of the cervical vertebrae in the animal. Giraffatitan's cervicals are larger than Brachiosaurus' cervical vertebrae, thus causing that enormous neck in terms of girth, rather than length. The length of the neck is also greater, but from this perspective it would be difficult to tell which neck is longer. Either way, the neck is not so much longer that the unknowing observer would be able to tell 100% the difference between the animals.
copyright unkown

The next image was an unfound copyright, but skull can be seen, and that is what is important in this bit. The skull here is in a strange perspective but two things stand out that remind us of Brachiosaurus immediately: high nostrils and skull size. The dental battery in both animals is fairly similar; both dinosaurs exhibit a mouth full of long peg-like teeth on both maxilla and mandible. The difference comes in the length of that skull and the crest at the top. The length of this skull is somewhat difficult to see due to the perspective of the illustration, however, it is clearly of a fairly long length for a Brachiosaur. This is due to the fact that the skull of Giraffatitan is actually longer than that of Brachiosaurus and therefore this illustration of the skull is correct in that regard. The crest is set back further on the skull it appears, because the skull is in fact longer than that of its contemporary. The crest itself is also slightly larger than the nares of Brachiosaurus. Brachiosaurus actually possesses a nares much like Camarasaurus does which places the potential opening for the nostrils, if in the center of the nares, more between the eyes. If Giraffatitan were to have its nostrils at the center of its nares crest the nostrils would be just above the eyes and almost even with them rather than forward of them.

©Dmitry Bogdanov
The inclusion of Bogdanov's Giraffatitan is to exemplify the chest and tail of the animal. Brachiosaurus possessed a longer tail and a deeper trunk than did Giraffatitan. Here in this Giraffatitan we can see clearly that the shallow trunk does not extended below the knees and does not push forward of the knees either when standing at 90 degrees to the ground. It also does not slope downward as we continue backward but stays clipped level at about  and just above knee level from the coracoids to the pelvis. There we meet the iliac vertebrae joining to the caudal vertebrae and find a short tail by dinosaur standards extending only about the length of the trunk behind the dinosaur. Looking above you can see a pot bellied version, Brachiosaurus' belly going below his hind legs' knees while the chest remains deep.
©Greg Paul
Paul's 1988 Giraffatitan reconstruction

©Michael Taylor
Below I have included Paul's original 1988 reconstruction of Giraffatitan and Mike Taylor's composite of Giraffatitan and Brachiosaurus with his own captioning of the image to explain. This was taken from the Journal of Vertebrate Paleontology 29(3) 787-806. These are for reader's reference, and I will not critique them.

Skeletal reconstruction of Brachiosaurus altithorax. White bones represent the elements of the holotype FMNH P 25107. Light grey bones represent material referred to B. altithorax: the Felch Quarry skull USNM 5730, the cervical vertebrae BYU 12866 (C?5) and BYU 12867 (C?10), the “Ultrasauros” scapulocoracoid BYU 9462, the Potter Creek left humerus USNM 21903, left radius and right metacarpal III BYU 4744, and the left metacarpal II OMNH 01138. Dark grey bones modified from Paul’s (1988) reconstruction of Giraffatitan brancai. Scale bar equals 2 m.

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