Diplodocus longus

NPS / Bob Walters and Tess Kissinger

 

Diplodocus longus is a species of sauropod dinosaur from North America. It lived during the Late Jurassic Period, about 150 million years ago. Diplodocus was one of the most abundant sauropods (long-necked dinosaurs) in the Morrison Ecosystem. Its pencil-like teeth were only in the front of the mouth and likely were used to strip leaves off of low-growing plants. It could get up to 92 ft (28 m) in length and probably traveled in small herds. Despite its length, Diplodocus was lightly built compared to other sauropods. An Apatosaurus would've probably weighed 2 to 3 times more than a Diplodocus of similar size.

 

Diplodocus Facts

• Diplodocus longus was the longest dinosaur found in the Carnegie Quarry, and was probably the longest dinosaur of the Morrison Ecosystem.
• Diplodocus longus was about 80 feet (24.3 meters) long from head to tail. It had about 80 vertebrae (back bones) in its tail alone!
• Diplodocus is Greek for "double-beam." The name refers to the unique shape of its tail vertebrae. Each vertebra has two structures on the bottom, called chevrons, that are parallel to one another.

 

 

A Very Long Dinosaur

Diplodocus longus was first described in 1878 by the paleontologist, Othniel Charles Marsh. Marsh was one of the predominant figures who participated a tense but productive period of paleontogical history known as "The Bone Wars," which lasted from the 1870s through the 1890s. The name Diplodocus means "double beam" in Greek. It was inspired by the two long parallel protrusions, called "chevrons," that appear on the bottom of some of the tail vertebrae. Diplodocus longus was an exceptionally long dinosaur whose skeleton was made up of almost 300 bones. However, its tail alone was comprised of about 80 vertebral bones (bones from the spinal column). That means that almost one-third of a Diplodocus's body was just tail! Both adults and juveniles of Diplodocus longus were preserved in the Carnegie Quarry at Dinosaur National Monument, including 3 of the most complete Diplodocus skeletons ever found. Many Diplodocus longus bones are still preserved on the Wall of Bones at the Quarry Exhibit Hall.

 

The long white rope-like structure embedded in the wall above the mules is actually a tail from Diplodocus. Here, they have already been plastered over in preparation for removal.

NPS Douglass Collection, edited by Evan Hall

Preserving Tiny Tail Bones
Based on the length of its skeleton, scientists estimate that the average Diplodocus probably measured about 80 feet (24.3 meters) long as an adult. Excavations of the Carnegie Quarry at Dinosaur National Monument produced 3 of the best Diplodocus longus skeletons ever found. One specimen found at the monument included 82 of the dinosaur's tail bones still connected in the right order as they would have been in life. The last third of Diplodocus's tail tapers down to a "whiplash," made up of very tiny bones. The last and smallest tailbone of an adult Diplodocus was only about the length of a human pinky finger, and could easily fit into the palm of your hand. Usually, body parts this thin and delicate are some of the first things to decay. Since the dinosaurs of the Carnegie Quarry were swept into their current location by a river, it's surprising that these tiny tail bones weren't carried away by the current and lost forever. However, during the Late Jurassic Period, the part of the river that became the Carnegie Quarry sandstone was a catching-place for debris, like a bend or a sandbar. This allowed bones and body parts to pile up and get buried very quickly in the fine sediments, which preserved even very small and delicate bones.

 

"Skulls!"

One of the most astounding finds of the Carnegie Quarry was the number of skulls that were preserved. In general, skulls are incredibly rare to find because of their delicate nature. Several skulls from adult and juvenile Diplodocus were uncovered during the Carnegie Quarry excavations that happened between 1909 and 1924. Earl Douglass, the paleontologist who found the Carnegie Quarry and oversaw excavations there for 15 years, was elated by the number of skulls that were preserved. One of his journal entries dating to November 15, 1910 is titled, "SKULLS!" In it, Earl Douglass describes how the excitement of uncovering a Diplodocus skull the day prior disrupted his sleep before he got up to excavate it.

"Dreamed the greater part of the night working on diplodocus skull... uncovering the bones of the back portion time after time until morning. I would awake and get up and then go to bed and dream it over and over... I went down later, raised the plaster up we had put on, took out a fresh piece of rock, and behold a SKULL." — Earl Douglass

 

Diplodocus Questions and Answers

Could Diplodocus's tail break the sound barrier?

Probably not. Based on its tail anatomy, scientists have determined that Diplodocus had an extremely flexible tail, like a lizard. Some studies have suggested that Diplodocus may have been able to lash its tail so dramatically that the force of it could've broken the sound barrier, creating a loud whip-crack sound. However, a more recent study which built models of Diplodocus tails and subjected them that kind of force suggested otherwise. It found that while a Diplodocus could certainly whip its flexible tail, cracking it with enough force to break the sound barrier would've done incredible damage to the bones and ligaments. That study found that the speed of a Diplodocus tail-whip was still very fast though, capable of rushing back and forth at about 62 mph (100 kph). Scientists have suggested that the tail may have been used as a weapon, or perhaps as a form of communication with other dinosaurs.

If sauropods were plant-eaters, why did they have pointy teeth?

Many people know about a certain tooth trend common among animals. Carnivores (meat-eaters) tend to have pointy teeth, herbivores (plant-eaters) have flat teeth, and omnivores (animals that eat both plants and meat) have a mix of teeth. However, this tooth trend is much more common among mammals than reptiles. Unlike reptiles, mammals can have many different kinds of teeth in one mouth, with each tooth-type serving a different purpose. This is because mammals usually have to chew their food or use their teeth to crack open bones. Reptiles generally don't do this. They just take a bite and swallow it whole, so their teeth don't need to be fancy.

Like most modern reptiles, dinosaurs don't usually have a bunch of different tooth-types in their mouths. Some teeth may be larger or smaller than others, but in general, each tooth in the mouth of a single dinosaur looks the same. Many sauropods had small peg-like or pencil-shaped teeth only in the front of their mouths. Based on the shape and scratch patterns on the teeth of dinosaurs like Apatosaurus, Diplodocus, and Barosaurus, scientists think their teeth worked like a rake. They probably fed by biting onto a plant and pulling their head backwards. The teeth would pull fresh new plant material into the dinosaur's mouth, which it likely swallowed whole. Some sauropods, like Camarasaurus, had broad spoon-shaped teeth. These more robust teeth probably allowed it to feed on tougher, woodier plants.

 

For More Information

Visit the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, or the Smithsonian National Museum of Natural History to see Diplodocus longus fossils collected from Dinosaur National Monument. The Utah Field House of Natural History State Park Museum in Vernal, Utah, is only a 30 minute drive from Dinosaur's Quarry Exhibit Hall. It is the closest museum to Dinosaur National Monument that has a mounted skeleton of Diplodocus on display. The closest place with a Diplodocus longus on display from Dinosaur National Monument is at the Denver Museum of Nature and Science, a 6 hour drive from the monument.