Episode 39 is all about Brachiosaurus, a sauropod with longer forelimbs than hindlimbs.
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In this episode, we discuss:
- The dinosaur of the day: Brachiosaurus, whose name means “arm lizard”
- Brachiosaurus is a sauropod that lived in the Jurassic in North America
- Described by Elmer S. Riggs in 1903, based on fossils found in the Colorado River
- Type species is Brachiosaurus altithorax, and Riggs said it was “the largest known dinosaur“
- Brachiosaurus means “arm lizard”, named so because the length of its arms was unusual for a sauropod
- Name “altithorax” means “deep breastplate” because it had a deep, wide chest cavity
- Holotype is right humerus, right femur, right ilium, right coracoid, sacrum, trunk, two caudal (tail) vertebrae, and some ribs
- Type species based on a partial postcranial skeleton (fossils collected in 1900)
- Riggs and his team (from the Field Columbian Museum, now the Field Museum of Natural History of Chicago), went to the area after Riggs sent inquiries about fossil finds in 1899 to rural areas. S.M. Bradbury, a dentist and amateur fossil collector, responded
- Type species were not the first Brachiosaurus bones found, but it was the first attributed. A skull was found in 1883 in Colorado, sent to Charles Marsh, who used it in his restoration of Brontosaurus/Apatosaurus. In the 1970s Jack McIntosh and David Berman decided the skull was more like a Camarasaurus, but in 1998 Kenneth Carpenter and Virginia Tidwell analyzed it and found it to be somewhat in between a Camarasaurus and Giraffatitan bracai (considered Brachiosaurus brancai at the time). It’s not assigned to a species but it’s classified as Brachiosaurus
- Skull was loosely attached to its skeleton (like other sauropods), so after it died, easy to detach, either via predators or erosion (explains mix up in skull for Brachiosaurus v. Camarasaurus)
- Type species bones went on display at the Field Museum in 1908, but there was only 20% of the skeleton, so it wasn’t mounted. In 1993, “holotype bones were molded and cast” and missing parts based on Giraffatitan fossils. It was mounted in 1994 in the Field Museum, until 1999 when it was moved to United Airlines Terminal One in O’Hare International Airport so the museum could display the T-rex Sue. The same year, the museum mounted a second cast of Brachiosaurus outside the museum. Only the humerus and two dorals are real and on display in the museum
- Type specimen is the most complete one found so far (which isn’t very complete)
- The family, and the genus, has had some reclassificiations
- Until 2009, Giraffititan was considered to be a Brachiosaurus
- Giraffaititan is different from Brachiosaurus because it had different trunk vertebrae. Olshevsky made Giraffaititan its own genus and in 2009 Michael Taylor published a study on the differences and found 26 “distinct osteological (bone-based) characters), which is more than Diplodocus v. Barosaurus; Brachiosaurus had a 23% longer trunk vertebrae series and 20-25% longer body and a taller tail
- Also a shoulder blade assigned to Brachiosaurus that used to be considered part of the species Ultrasauros (episode 20)
- Kingham reassigned Brachiosaurus to the genus Astrodon in 1969, but not many accepted it
- Brachiosaurus fossils found in Colorado, Oklahoma, Utah, and Wyoming
- Rare sauropod of the Morrison Formation
- Morrison Formation was semiarid, with dry and wet seasons and flat floodplains. It had river lining forests (otherwise no other trees) of conifers, tree ferns and more. Other sauropods in the area included Apaotsaurus, Barosaurus, Camarasaurus, Diplodocus
- Brachiosaurus was rare in the area. John Foster found 12 specimens of Brachiosaurus versus 112 Apatosaurus and 179 Camarasaurus and 98 Diplodocus
- 2012, a juvenile sauropod postcranial skeleton found in Morrison Formation in Wyoming, probably a Brachiosaurus
- Because only incomplete specimens of Brachiosaurus have been found, a lot of estimates of how it looked are based on Giraffititan
- Michael Taylor analyzed Giraffitian and Brachiosaurus in 2009 and estimated Brachisaurus was about 82 ft (25 m) long
- May have weighed as much as 35 metric tons and 56 metric tons, though lots of size estimates are based on Giraffatitan (formerly Brachiocsaurus brancai) because it is more complete specimen
- A 2014 study in PLOS Biology estimated Brachiosaurus weighed 62 tons (56 metric tons)
- Had large air sacs in the neck and trunk (keep it lighter)
- Very long neck, small skull, and large body (like most sauropods), but forelimbs were longer than hindlimbs and tail was shorter compared to its neck
- Brachiosaurus skull was only 1/200th of its body volume
- Up to 4-50 ft (12-16 m) tall
- Very giraffe-shaped
- Could not actually rear on its hindlimbs (like in Jurassic Park)
- Could not rear up on hindlegs. Heinrich Mallison found that though other sauropods could do that, Brachiosaurus had too long of front limbs and would not have been stable, and also it didn’t matter since it could already reach plants at such a tall height, compared to other sauropods
- Neck was probably not very mobile but would have pointed upwards naturally
- Considered to be a “high browser”, eating vegetation that was 30 ft (9m) off the ground
- May have also eaten lower vegetation (10-16 ft or 3-5 m above ground)
- According to Wilkinson and Graeme Ruxton in 2011, Brachiosaurus, with its 30ft long (9m) neck, may have saved time and energy by low browsing for food (‘reduces the overall cost of foraging by 80 percent, compared with dinosaurs with shorter necks’)
- Probably ate ginkos, conifers, tree ferns, large cycads
- Ate in up and down motion of jaws, with teeth shearing plant matter when they closed
- 2008 study in the Royal Society said Brachiosaurus may have swallowed its food whole (teeth could strip plants but not break up large chunks)
- Would take soft-tissue analysis to know for sure if they were high browsers or low browsers
- However, being a high browser would mean it didn’t have to compete for food with other herbivores
- Spoon-shaped teeth
- Had 52 teeth, 26 on top and 26 on bottom
- Ate 440 to 880 (200-400 kilograms) of food every day, though more recent estimates put it at 260 pounds or 120 kilograms per day
- Probably traveled in herds and migrated for food
- Probably liked flat land, too much energy to climb hills and less likely to fall
- Brachiosaurus probably walked on its toes (digitigrade stance, like dogs and cats), compared to “plantigrade” like humans, where heels and toes touch the ground when walking
- Had a claw on the first toe of each front foot and claws on the first three toes of its rear feet (each foot had five toes)
- Was probably warm-blooded, like other sauropods, and the large nasal arch may have helped cool its brain (before the air sacs were known about and Brachiosaurus was thought to weigh a lot more, scientists thought it could not have been warm-blooded)
- Scientists used to think because it was so large it had high body temperatures, but in 2011 they were able to calcualte its temperature to be 100.8 degrees F (38.2 C), based on ratios of some isotopes in Brachiosaurus teeth, so it probably kept cool with a lower metabolism as an adult
- Lowering its body temperature and slowing metabolism would mean it would not have had to spend as much time eating
- Had large hearts and high blood pressure to pump blood up its neck to its brain (heads were held up high), so its blood pressure was possibly 400 mm Mercury, 3-4 times higher than a humans’
- Scientists used to think Brachiosaurus lived in the water, because its nostrils are at the top of its head, but Brachiosaurus had air-filled pockets in its bodies, so would have been too buoyant in water, according to a 2004 study in journal Biology Letters
- Arch of bone over the snout and in front of the eyes
- Nostrils were thought to be on an “enlarged bump in front of its eyes”, but in 2001 Lawrence Witmer analyzed muscle attachment scars on dinosaurs and present day animal skulls and found that Brachiosaurus nostrils were near the tip of its snout
- The crest that scientists used to think was the nose on top of its head now may be a resonating chamber to amplify sounds it made
- May have had a good sense of smell
- Adults had no predators (largest predators were Allosaurus, Ceratosaurus and Torvosaurus, which were half its size)
- Long tail could whip at predators
- May have lived as long as 100 years
- Had leathery skin
- Eggs found in linear pattern, so probably laid eggs when walking (and probably didn’t take care of eggs)
- Brachiosaurus has appeared in Jurassic Park and Walking with Dinosaurs, and a model from Jurassic Park was used in the 1997 special edition of Star Wars Episode IV: A New Hope
- The “rontos” from Taooine were based on Brachiosaurus from Jurassic Park (in Star Wars)
- 1991 GX7, a main belt asteroid, was named 9954 Brachiosaurus
- Family is Brachiosauridae (found in North America and Africa and Asia)
- Brachiosaurids were quadrupedal, with longer forelimbs than hindlimbs
- They probably went extinct in the early Cretaceous, though there’s some evidence some may have lived in the late Cretaceous
- Lots of debate over which animals are in this family
- Former Brachiosaurus include Lusotitan, Giraffatitan
- Other Brachiosaurids include Astrodon, Bothriospondylus, Dinodocus, Pelorosaurus, Pleurocoelus, and Ultrasaurus (but many are considered dubious)
- Another Brachiosaurid is Europsaurus holgeri, a dwarf sauropod (only 20 ft long) that lived on an island off the coast of Germany
- Another Brachiosaurid may be an Asian dinosaur, Qiaowanlong
