Giraffatitan: Beast of the Week

Last time we did Brachiosaurus, now it's only fitting we cover its relative that everyone gets it confused with.  Enter Giraffatitan brancai!  Giraffatitan was a sauropod dinosaur that lived in what is now Tanzania, Africa, during the late Jurassic period, about 150 million years ago.  This plant-eater was huge, amongst the largest land animals of all time.  The most well-studied specimens of Giraffatitan are of an animal that was about 74 feet long when it died, however, this animal's bones show it was still growing at the time.  Some estimate this dinosaur could acheive lengths of closer to 85 feet long from snout to tail.  The name, Giraffatitan, translates to "Giraffe Titan/Giant".  This is in reference to its long neck and front limbs which are superficially similar to those of the comparably puny and unrelated modern giraffe.

Giraffatitan brancai watercolor life reconstruction by Christopher DiPiazza.

This dinosaur's long neck and legs would have been used to help it gain access to more vegetation high in the trees, which it would have eaten using its chisel-shaped teeth lining the front of it's mouth.  Since it didn't have any teeth designed for chewing in the back of its mouth, Giraffatitan, like many sauropods, would have swallowed mouthfulls of foliage whole.  Unlike other kinds of sauropods like Apatosaurus or Barosaurus, Giraffatitan wouldn't have been able to rear up on its hind legs very easily because it's center of gravity was near its chest and shoulders, not its hips.  This anatomical characteristic is common to all members of Giraffatitan's family, called Brachiosauridae.

Giraffatitan skull on display at Museum fur Naturkunde in Berlin, Germany.  Note the nostril cavity on the forehead.

Another interesting characteristic of Giraffatitan's anatomy is it skull, which possesses nostril holes on its forehead that form a bony crest.  Scientists used to believe that Giraffatitan, along with all other sauropods, lived a semi-aquatic lifestyle and that the nostril placement was for snorkeling.  We now know this is false since the water pressure would likely prevent the dinosaur from comfortable breathing if its chest was that far underwater.  Another idea suggested that Giraffatitan would have had a trunk since modern mammals with high nostril placement, such as tapirs and elephants, have trunks.  This hypothesis is likely false as well because a sauropod's teeth were designed for grasping food and some fossilized specimens even show wear from it.  Why would it need a trunk?  Both elephants and tapirs have chewing teeth in the backs of their mouths.  According to the most recent studies, it is most likely that Giraffatitan would have had fleshy nostrils near the tip of its snout that connected to the nostril openings at the top of the skull in life.

Giraffatitan skeletal mount on display in Berlin, Germany.

Giraffatitan used to be called Brachiosaurus and was one of two known species within its genus.  In fact, most reconstructions labelled as "Brachiosaurus" are based on Giraffatitan remains.  The famous 
"Brachiosaurus" from Jurassic Park, for instance, was based on Giraffatitan. (although at the time the movie was made it was still considered a kind of Brachiosaurus.)  It was realized that the animal now referred to as Giraffatitan and the other animal that used to share a genus with it, Brachiosaurus altithorax, had enough morphological differences so the genus was split.  The biggest notable difference between these two giant dinosaurs is their midsections and tails.  Brachiosaurus had a longer, more robust torso and a longer tail while Giraffatitan was more compact with a shorter tail.  

Giraffatitan scapula (shoulder blade) on display in Berlin, Germany.  5'1" wife for scale.

References

Russell, D., Béland, P. and McIntosh, J.S. (1980). "Paleoecology of the dinosaurs of Tendaguru (Tanzania)." Mémoires de la Societé géologique de la France, 59: 169-175.

Taylor, M.P. (2009). "A Re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropod) and its generic separation from Giraffatitan brancai (Janensh 1914)." Journal of Vertebrate Paleontology, 29(3): 787-806.

Witmer, L.M. (2001). "Nostril position in dinosaurs and other vertebrates and its significance for nasal function". Science 293 (5531): 850–853. doi:10.1126/science.1062681. PMID 11486085.