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.

Brachiosaurus: Beast of the Week

 It's time to check out one of the most famous giant dinosaurs.  Make way for Brachiosaurus altithorax!

Brachiosaurus was a huge plant-eating sauropod dinosaur that lived in what is now Western United States during the late Jurassic period, about 153 million years ago.  It's genus name, Brachiosaurus, translates to "Arm Lizard/Reptile" because its arms were longer than its legs, and its species name, altithorax, translates to "Deep Chest" because of its particularly tall ribcage.  From snout to tail an adult Brachiosaurus is estimated to have been between 60 and 70 feet long and its head was held about 30 feet off the ground when standing.  

Brachiosaurus altithorax watercolor life reconstruction by Christopher DiPiazza.

Brachiosaurus was originally only known from a few bones, including the pelvis, some vertebra, and limb bones.  Over the years, however, more fossils from this dinosaur have been unearthed from multiple individuals that altogether give us a relatively complete skeleton. Sauropod skeletons are notorious for being found incomplete because they're so large and therefore their bones were more prone to getting eroded, carried away by predators, or scattered after death.  Fossilization most commonly happens when the animal's body is buried rapidly and completely after death.  Therefore it's takes a lot more forces of nature for this to happen to a large animal than a small one.

Brachiosaurus, as stated above, is famous for having longer arms than legs, which makes its family, brachiosauridae, unique among dinosaurs.  In addition, its arms were placed farther below its spine than its legs, causing it to be even taller in the front.  This unusual posture allowed Brachiosaurus to reach especially high with its already long neck to take advantage of leaves on the tops of trees that even other sauropods couldn't easily reach.  Unlike other sauropods, brachiosaurids had proportionally shorter back legs, and tail which were held relatively low because of this sloping build.  Having shorter back limbs also would have highly limited Brachiosaurus' ability to rear up on its hind legs, which other kinds sauropods, like the diplodocids, likely were able to do more easily.  Despite what that iconic scene in Jurassic Park* may show you, real brachiosaurs likely very rarely stood on just two limbs, and if/when they did, only for extremely short periods of time, like to mate or possibly intraspecies combat.  Since Brachiosaurus' center of gravity was in its torso, not its hips, that kind of posture would put extreme pressure on its back end which could seriously injure the dinosaur.  All things considered, if an animal could reach thirty feet in the air from a standing position...rearing up probably wasn't necessary often.

Brachiosaurus' neck bones were relatively rigid closer to the skull, but the part of the neck closest to the shoulders would have had more flexibility.  This means that despite its very front-loaded posture, it could still bend its neck so its head was close to the ground if it need be.  This would have been necessary when Brachiosaurus needed to drink, or maybe even eat certain kinds of low-growing plants at times.  It wouldn't have needed to bend or spread its front limbs in order to achieve this either.  The neck bones, along with many of its other bones, were hollow and would have been filled with air sacs in life.  Some of the spaces around the bones (which can be inferred by the negative space around the edges of the vertebra) was also filled with air sacs in life.  These structures were connected to the animal's respiratory system and allowed the body to be more efficient in distributing oxygenated air to where it needed to go.  This also made the animal much lighter for its size, so moving that neck around wouldn't have drained as much energy as it would have appeared.  

Brachiosaurus could have lowered its head down to ground-level relatively easily when it wanted to.

The skull of Brachiosaurus was found and published in 1998.  It had a relatively long snout with chisel-shaped teeth concentrated to the front of the mouth, an adaptation for stripping leaves off branches.  It had no teeth in the back of the jaws, implying it simply swallowed all its food and relied on its insides to do all the work of breaking everything down.  It is possible dinosaurs like Brachiosaurus swallowed rocks, which would stay inside the stomach for extended periods of time, which would have helped mechanically break down its food as they mixed around in the stomach, called gastroliths.  Brachiosaurus' eyes were set high, towards the rear of the skull and the naris (holes in the skull where nostrils were) are elevated in a sort of bony crest between the eyes.  For a long time it was thought that Brachiosaurus had its nostrils high on the head exactly where these openings are on the skull, but it is more likely that these openings were connected to soft tissue that placed the nostrils closer to the front of the snout.  The evolutionary reasoning why Brachiosaurus, and many other sauropods had these openings on the top of the skulls, if not the true placement of the nostrils, is still somewhat of a mystery.  Some have suggested that this area was a space where air could flow through and help keep the blood in the animal's head and brain from overheating.

Photograph of the mostly complete (partially reconstructed) Brachiosaurus skull from Carpenter's 1998 paper.

As an adult, Brachiosaurus likely had few to no predators to worry about.  It was just too big.  When imagining it in its environment I sometimes stop thinking of it as an animal and more as a roaming force of nature more than anything else.  That being said, young Brachiosaurus were probably easier prey for all sorts of predators from the moment they hatched for years until they hit a certain size.  These younger animals probably relied on camouflage or possibly living in groups to minimize their chances of becoming another animal's meal.  

Special thanks to Dr. Heinrich Mallison for lending his sauropod expertise during the process of me writing this post!  See you next time!

*The dinosaur in Jurassic Park that's referred to as Brachiosaurus is actually based on a close relative called Giraffititan.  Giraffititan used to be considered a species of Brachiosaurus back when the film was made, so it being referred to as such in 1993 wasn't wrong.  

References

Carpenter, Kenneth, and Virginia Tidwell. 1998. Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado. Modern Geology 23:69-84.

D'Emic, M. D.; Carrano, M. T. (2019). "Redescription of brachiosaurid sauropod dinosaur material from the Upper Jurassic Morrison Formation, Colorado, USA". The Anatomical Record. 303 (4): 732–758. 

Riggs, E.S. (1903). "Brachiosaurus altithorax, the largest known dinosaur". American Journal of Science. 4. 15 (88): 299–306.Taylor, M.P. (2009). "A re-evaluation of Brachiosaurus altithorax 

Russell, D. A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. p. 78. ISBN 978-1-55971-038-1.Witmer, L. M. (2001). "Nostril position in dinosaurs and other vertebrates and its significance for nasal function". Science. 293 (5531): 850–853.

Lycaenops: Beast of the Week

 This week we will be checking out a prehistoric creature that bears a striking resemblance to some modern-day animals.  Let's check out Lycaenops!

Watercolor life reconstruction of two Lycaenops angusticeps by Christopher DiPiazza.

Lycaenops was a meat-eating synapsid (wide group of animals that includes mammals) that lived in what is now South Africa during the Permian era, between 271 and 251 million years ago.  The genus name translates to "Wolf Face" because of it's relatively long snout and prominent canine-like fangs, which caused this creature to superficially resemble wolves, and other modern canids despite not being closely related.  From snout to tail, Lycaenops measured about three feet long, or a little under one meter.  There are several species within the genus, Lycaenops, which accounts for the relatively wide range of time in which this genus existed.

Lycaenops was part of a widely successful group of vertebrates that lived during the Permian, before the first dinosaurs, that are casually referred to as "mammal-like reptiles" even though they weren't mammals...and they weren't really true reptiles either.  They were somewhere in between and no living members exist today, which makes it even more difficult to visualize what they would have been like when alive.  Within this extremely expansive group, Lycaenops, was specifically a member of the gorgonopsid family.  These meat-eating synapsids all long, rectangular skulls with very long, curved fangs on the top and bottom jaws, in the same place that canines would be on some mammals, like dogs, bears, and cats.  This is an amazing example of convergent evolution, since these gorgonopsids were not directly related to any of these carnivorous mammals.  

Lycaenops ornatus skeletal mount on display at the American Museum of Natural History in New York.

Lycaenops probably specialized in hunting smaller prey.  The Permian was home to no shortage of small reptiles, amphibians, and other synapsids, so it is likely Lycaenops had a pretty expansive menu to choose from.  It's eye sockets are relatively large so it probably had decent vision, and its limbs were also pretty long in proportion to its body, which it appears to have carried under its body more so than many other reptiles and synapsids at the time, which had more sprawling postures, like today's lizards and crocodilians.  This combination of features probably gave Lycaenops its edge when pursuing meals when it was alive.  

It is important to keep in mind that Lycaenops lived right up to the very end of the Permian era, which is marked by a massive global extinction event, more destructive than the one that wiped out most of the dinosaurs millions of years later.  It was this extinction that actually leveled the playing field and allowed the dinosaurs to even evolve in the first place.  Because of this it is worth noting that Lycaenops and its relatives were extremely successful animals, and likely would have kept flourishing if it wasn't for that catastrophic event.  

References

Broom 1925 : On some carnivorous therapsids. Records of the Albany Museum, vol. 3, n. 4, p. 309–326.

Gebauer, E.V.I. (2007). Phylogeny and evolution of the Gorgonopsia with a special reference to the skull and skeleton of GPIT/RE/7113 ('Aelurognathus?' parringtoni(Ph.D. thesis). Tübingen: Eberhard-Karls Universität Tübingen. pp. 1–316.