Fossil Friday: Apatosaurus

This Apatosaurus is Louise. She's a good friend of Ajax.

Species: Apatosaurus ajax (Ah-pat-oh-sore-us ae-jacks)

What it means: Deceptive lizard

Other Species: Apatosaurus louisae

Where I live: Western U.S.A.- The Morrison Formation

When to find me: The Late Jurassic period, about 152 million years ago.

My favorite food: Plants! I’m an herbivore.

Most Apatosaurus wouldn't be quite as large as some sources portray them. That said, they're still enormous! This one is a modest size, just small enough to tickle her belly.

My neighborhood: The Morrison Formation covers a huge expanse of land with a variety of different habitats teaming with life. Most of it was very much like the Serengeti of modern day Africa, only with prairies of drought-tolerant ferns and cycad relatives instead of grass. Dense woodlands of tall conifers like the modern araucaria, ginkgoes, and tree ferns would only lie in places of plentiful water such as the few permanent rivers. Other areas had far more sparse and shrubbier vegetation like the open woodlands of acacia trees in the Serengetti.

Life in this environment would’ve adapted to long months of harsh drought, followed by a few months of monsoon that flooded the rivers. Many of the larger herbivores may have migrated like the herds in Africa do today, while most carnivores stayed behind to feast on the dead and dying, or else become opportunistic hunters of less traditional diets for lean times, such as fish or turtles in the rivers.

A few of my neighbors: First let me share my herbivorous friends…

  • Long-necked sauropods like Brachiosaurus, Camarasaurus, Diplodocus, Barosaurus, Suuwassea, Supersaurus, Haplocanthosaurus, and Dystrophaeus.
  • Armored dinosaurs like Stegosaurus, Hesperosaurus, Mymoorapelta, and Gargoyleosaurus.
  • Two-legged ornithopods like Dryosaurus, Camptosaurus, and Nanosaurus

The predators in the neighborhood include dinosaurs like Allosaurus, Torvosaurus, Ceratosaurus, Saurophaganax, Marshosaurus, Stokesosaurus, Ornitholestes, Coelurus, Tanycolagreus, Elaphrosaurus, and Koparion.

Plus there are all the tiny critters on the ground I try not to step on…countless lizards, crocodile relatives on land and water, mammals, frogs, turtles, fish. Some of the pterosaurs flying in the sky help me with any bugs that might try to bite me.

Fun Facts:

  • Apatosaurus gets its name from the greek apate/apatelos (deception/deceptive) + sauros (lizard). The paleontologist Othniel Charles Marsh named it for the chevrons, which are long, thin bones on the underside of the tail. He thought they looked more like the chevron bones of mosasaurs (a large, marine reptile) than other dinosaurs.
  • The type species is named after Ajax, a hero in Greek mythology. But the few fossil specimens of this species are incomplete, and the holotype (fossil specimen that determines which fossils are Apatosaurus) is a juvenile. The second and far more well known species is Louisae, named after Louise Carnegie. Her husband, Andrew Carnegie, helped fund much of the field research to find more complete dinosaur skeletons in the American West and founded the Carnegie Museum. Of the two valid species, A. lousiae is the most well studied because its fossils are much more numerous and complete, including a few skulls.
  • Othniel Charles Marsh named Brontosaurus when there were still few fossils known for Apatosaurus. Like many new species named at the time, it appeared very different from what he had, and so was given a new genus name. Years later, more fossils like those of “Brontosaurus” were discovered, but it looked like the only differences from Apatosaurus had to do with age. Since the Apatosaurus holotype was only a juvenile, it was determined that there were not enough differences to make Brontosaurus a separate genus from Apatosaurus. Elmer Riggs published the paper in 1903, which stated that Brontosaurus was not a valid genus.
  • In April 1905, the “mounting of the largest skeleton, the Amphibious Dinosaur Brontosaurus,” was finished at the American Museum of Natural History. It was the most complete sauropod ever discovered, only missing the head, feet, and parts of the tail.
  • Dinosaur enthusiasts (including myself) were forever correcting the masses, and saying “It’s Apatosaurus, not Brontosaurus!” Until at last Brontosaurus got its awesome name back and was reestablished as its own genus in 2015.
  • The first, and nearly complete, fossils of Apatosaurus loiusae were described and named in 1916. A head was found nearby, but it was so small and delicate compared to the rest of the skeleton that the few who thought it was the correct one where considered crazy by the scientific community. The skeleton was mounted at the Carnegie Museum, headless.
  • The Carnegie Apatosaurus was finally given a head in 1934, but the head was a cast of a Camarasaurus skull. Camarasaurus was a smaller sauropod than Apatosaurus, but the head is larger, stronger, and more boxy in shape, a head that looked suitable for the huge and robust Apatosaurus. The mounted skeleton had the wrong head until 1979, when sauropod expert J.S. McIntosh and Carnegie Museum Paleontologist David Berman determined that the delicate skull first found near the original fossils was most likely the head after all.

Fossil Finds: Many individuals, especially of A. louisae. Most fossils are fragmentary, especially adult specimens, but a few are almost complete. Combined with tracks and other trace fossils, we have great knowledge about Apatosaurus.


Mathew, W. D. (1905) “The Mounted Skeleton of Brontosaurus.” The American Museum Journal.

Foster, John. Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press, 2007

Parson’s, Keith M. “The Wrong-Headed Dinosaur.” Internet Archive Wayback Machine,

“Apatosaurus.” Wikipedia,

6 thoughts on “Fossil Friday: Apatosaurus

  1. Awesome review! Which dinosaur in the movie “Jurassic Park” is the one which “sneezed” on the girl when she got too close? Was it Brontosaurus, Apatosaurus or some other large herbivore? Also, did these dinosaurs drag their tails when they walked are were they totally suspended in the air and used for balance/defense only? How could it coordinate movement of all of its body parts with a head and brain that small?


    1. Thank you, I’m glad you liked it! And these are some great questions! πŸ˜€

      The dinosaur that sneezed all over the girl in “Jurassic Park” is supposed to be Brachiosaurus, but dino nerds (like me lol) will tell you that it’s technically Giraffatitan. What’s the difference? Brachiosaurus lived in North America, and has a much gentler slope to its forward than what is portrayed in the movie. It also has a slightly longer body and tail. Elmer here at the shop is a Brachiosaurus.

      Giraffatitian is Brachiosaurus’ African cousin. “Jurassic Park” has some inaccuracies of course, but it’s basically what Giraffatitan looks like. πŸ™‚

      Sauropod dinosaurs typically held their tails off the ground with no effort. They have bones called chevrons along the underside of the tail, especially close to the base, plus tall neural spines (the part of the vertebrae that sticks up along the spine). Together these bones make a very strong and relatively rigid base for the tail to anchor powerful muscles that attach to the legs, and limit any up-and down movement. This is where they get all of the walking power, so these muscles are immense! In fact, a sauropod pushes with its back legs to move forward, and most of muscle power behind this push comes from a sideways swipe from the base of the tail to pull the leg back, which would then sway the entire tail from side to side as it walked.

      As you get further down the tail’s length, there would be a lot of swishing and movement at the thinner, more flexible ends, because the bones get much smaller and thinner. A bit like our finger bones, with few muscle attachments. This varies depending on the sauropod.

      In some this flexibility is extreme, like in Diplodocus and Apatosaurus, and some speculate scales like a sort of tassel to make a whiplash crack. It may not be uncommon to have the ends of tails broken or bitten off during confrontations, and they would be lethal weapons. Even a 6 foot monitor lizard has the strength to do serious damage to an adult human with just a swipe of its tail, so imagine the power behind a sauropod’s tail!

      As for how it can coordinate movements? The brain itself doesn’t have to control the legs at all. There is a bundle of nerves near the pelvis often called a “second brain” by some people. It’s not a brain, but just a concentration of nerve cells, and it helps with the automatic function of the legs and tail. We actually have this too, it’s just much, much smaller. The spinal chord also does a lot of automatic direction of movement, so really they weren’t as slow as we may think. They’re not going to be thinking about much of course, unless they see or smell a predator, but then what little thinking they do may be along the level of a fish or lizard, just on a much larger scale.

      Also, we do not have much to go on when it comes to reconstructing the brains of dinosaurs. Some dinosaurs preserve amazing brain cases, so we can get an idea on the shape of the brain, but even with that we have no idea on how many folds and neurons there might be, so the actual surface area of the brain may be bigger than what it appears all squished in the brain case. and most sauropod fossils are missing a head!

      In any case, sauropods where hugely (lol, pun not intended, honest) successful animals that thrived from the late Triassic all the way to the end of the Cretaceous (the Titanosaurs in South America where definitely among the biggest behemoths ever to walk), which is about 149 million years. Keeping in mind that it’s only been about 65 million years since the non-avian dinosaurs met their demise and mammals have had full reign of the Earth. So sauropods definitely had the reflexes and enough brain power (however little lol) to handle whatever was tossed their way. πŸ™‚


  2. So cute!! πŸ˜€ I really like the style experiment! You were able to get that adorable, squishy, cuddly look while still aiming for accuracy. Also cool to hear about the story of Brontosaurus. You mentioned it was reestablished as its own genus in 2015 (yay!). Did it also live the Jurassic along with Apatosaurus?


    1. Hi Brownie, thank you so much! I’m glad you like Louise (she’s a friend of Ajax πŸ˜‰ )

      The story between Apatosaurus and Brontosaurus is fascinating, and I was super happy when Brontosaurus was reestablished as its own genus in 2015. Thunder Lizard is too cool a name to be stuck as a nomen dubium!

      Brontosaurus bones are known from the Morrison Formation, so it was definitely around, but I’m not sure as to the exact time and place. The Morrison Formation actually covers a huge amount of land and quite a bit of time, so there are little localities where some critters are from and others aren’t. Like Fruitachampsa from the Fruita locality within the Morrison Formation. It is unique to the Fruita locality, and there are many with similar habits in other localities.

      For an animal as large as Brontosaurus though, plus how common Apatosaurus was in many localities (especially A. louisae), it’s not improbable to think it would’ve come across Brontosaurus. A bit like impala, wildebeast, and gnu roaming the savanna. These animals are all antelope, and still share the same space with other animals competing for similar resources like zebra, giraffe, gazelles, etc…

      The mind-boggling thing is there are so many huge sauropods sharing the same space! Though it is a little less surprising when we remember that this area covers the entire western and part of central North America. Mostly in what is now the USA, but it does stretch a little bit into Canada. πŸ™‚

      Now how often Brontosaurus would’ve come across Apatosaurus, and if they cared about it, I have no idea. πŸ˜€

      Liked by 1 person

  3. Fantastic review, Ms. Bujard-Schlichting. I do think though that you should replace Apatosaurus (when it comes before Suuwassea for Brontosaurus) and mention Allosaurus in the predator section. But I can thank the creature Ajax is for having its own profile. The Morrison has a diversity of species, but I think you can make it through. Harpactognathus, Fruitafossor, Haplocanthosaurus, Stokesosaurus (which by the way, you spelled incorrectly), Tanycolagreus, Kaatedocus, and Glyptops are what I’m most excited for.


    1. Thank you Angel! Oops, I forgot to edit the dinosaur names listed when I copied it from the Allosaurus post. Thank you for catching that. I also edited the typo. I may or may not rearrange them in alphabetical order later. The order the names are in now is the order they were listed in my primary reference book, so that’s how it happened.

      We’ll be staying in the Morrison Formation for a long while, since there are so many species. So I’m glad you’re excited for them! πŸ™‚


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