Who has never heard of Diplodocus? Since its discovery in the 19th century, Diplodocus has built up a solid reputation, to the point of being able to represent in the minds of the general public the reptile of the Mesozoic Era par excellence, this great large animal which immediately comes to our mind when we think about dinosaurs, with a small head at the end of a very long neck, more than 23 feet ( 7 meters )! With a minimum brain (1/100,000th of the weight of the beast) for a maximum body (about ten tons), its reputation as a not very smart animal sticks to its skin. It has even been said that it could have been nibbled on its tail without noticing it, as the nerve impulse would have taken so long to reach the brain…
The Diplodocus belongs to the Sauropods group, a group that did not specialize in either chewing plants or locomotion, they were rather slow because of their weight. In spite of this, their success has not waned and it is no coincidence that the Diplodocus was one of the first dinosaurs discovered and the first to be reconstructed: the size of the Sauropods is impressive and commands respect, as does their distribution over almost the entire surface of the Earth and for more than 100 million years.
Illustration of a diplodocus herd
The discovery of the first Diplodocus bones dates back to the year 1877, just a few years after Richard Owen invented the word 'dinosaur' ('Terrible Reptiles') to describe animals completely different from anything known until then. The end of the 19th century was indeed a prosperous period for dinosaurs, which were already beginning to fascinate both researchers and the public; it was a real "bone rush", with competition between the teams of two famous American paleontologists: Edward Drinker Cope and Othniel Charles Marsh, who in 1878 described a new dinosaur that he named Diplodocus longus.
The name Diplodocus ("double-beamed") refers to the unusual appearance of the herringbone bones below the tail vertebrae: they were shaped like two small beams - or two runners - which was thought to be unique to Diplodocus, but is also present in more recently discovered dinosaurs: Apatosaurus and Cetiosauriscus. These bones provide protection for the blood vessels and tissue under the tail.
The first Diplodocus connected skeletons were discovered in 1899 in Wyoming (USA) and since then almost all its bones have been discovered, allowing very precise studies to be made on this dinosaur.
Seeing this representative of the Sauropods, one would think that it was heavily built, giving it a clumsy look. On the contrary, the skeleton of the Diplodocus is extremely light. Thus, we can say that, compared to other Sauropods, Diplodocus has a wasp waist... For nearly 33yd (30 meters) long, it weighs only 10 tons, which is only 1/8th of the weight of the Brachiosaurus and 1/3 of that of the Apatosaurus, while these two dinosaurs are shorter!
The vertebrae are a key element in the lightening of the skeleton since they are practically hollow. The remaining bony stems are strong enough to support the animal's large frame.
A well-preserved fossil skeleton attributed to Diplodocus was found in Wyoming at the beginning of the 20th century, thanks to an expedition financed by the American billionaire Andrew Carnegie. Several casts of this skeleton are thus spread over 8 museums around the world, including those of New York, Paris, London. Everywhere, these casts caused a sensation in front of the public, contributing to the popularity of this dinosaur and provoking the beginning of a real Dinomania, which is still going on today.
Unfortunately, the original specimen was incomplete. To finish the mussels, the scientists of the time, therefore, made do with what they had on board. They simply fill in the missing bones with those of other dinosaurs. Thus, all the original mussels in this specimen actually have the feet of the dinosaur Camarasaurus, a contemporary of the Diplodocus. We know today that, contrary to what these casts show, the Diplodocus actually had one toe (the inner finger) with just one claw and not 3. The other toes must have had rounded pads, probably horny, like today's elephants.
Diplodocus Skeleton at the Houston Museum of Natural Science
Perhaps the Diplodocus used to stand up on its hind legs, its tail resting on the ground to stabilize itself. This acrobatic posture must have been quite costly in energy; it is therefore rather likely that it was only used when necessary, to defend itself against a predator for example. His tail could then help him by acting as a whip. The last few meters of the tail are made up of dozens of tiny vertebrae about 30 mm in diameter.
So when the Diplodocus wiggled the tail, the tip would move at supersonic speeds and snap like a whip. Too fragile, however, to inflict injury on opponents, the tail would just sniff in the air, disturbing a hungry Allosaurus, for example...
Diplodocus Tail Bones
It is also possible to think that in normal times, tail slapping could be used as a social link between the members of a group: regular and reassuring slapping of a mother Diplodocus for her cubs; more violent slapping in case of stress; slapping to signal her presence in the herd and her social position...
Since its discovery, the Diplodocus has undergone some important changes in its reconstructions by paleontologists.
At the beginning of their discovery, the Sauropods were victims of their disproportionate size compared to present-day animals and of their similarity to the group of lizards. Thus, the first Sauropods were depicted crawling, with their tails dragging on the ground. This is not the case. The fossil tracks left by these animals show that only their legs touched the ground.
Second reconstruction error: the Diplodocus had cutaneous dorsal spines. This was discovered recently, in 1992, by the American paleontologist S. Czerkas. He discovered fossilized imprints of the skin of a Wyoming Diplodocid, showing the existence of a row of conical-shaped dermal spines (up to 18 cm high) along the tail. It is likely that this row extended over the trunk and neck, giving the animal a curiously spiny appearance, much like a modern iguana. Since they do not fossilize, these spines remained unsuspected for a long time and show how difficult it is to reconstruct dinosaurs when only the bones are known.
Finally, an in-depth study of the skeleton and its reconstitution by computer showed that the body of the Diplodocus was horizontal, like a suspension bridge. The neck and tail were held horizontal by huge ligaments attached to the vertebrae. Thus, the tail could not drag on the ground even though some museums continue to depict it in this way. The horizontal neck was not very mobile, but the Diplodocus could still turn its head by describing long arcs of a circle, allowing it to graze on a wide radius around it, within a 90° limit.
This arrangement of the body of the Diplodocus has forced museums to revise the orientation of the head as well: downwards to allow it to graze. The horizontal body prevented it from straightening its neck to graze on the cones and needles of the highest Jurassic conifers. The Diplodocus thus resembled cows more than giraffes, unlike the Brachiosaurus.
What could the Diplodocus feed on? Plants, you might say... Logical for a Sauropod... Yes, but not just any plant from the Jurassic period. As we've just seen, the movements of its neck prevented it from grazing on the cones and needles of the tallest conifers. One wonders whether the fact that cones usually ripen in the tallest branches is an evolutionary ploy of conifers to keep the fruit out of reach of most herbivores.
If you are a herbivore too and want to claim it.
In fact, the food consumed by the Diplodocus depends very much on its teeth. If we look a little closer at their skull, we can notice that Diplodocus have pointed teeth and are located only on the front of the jaw. The mouth of these dinosaurs could, therefore, function as a comb or rake raking ferns and low vegetation. This way of feeding causes accelerated wear of the teeth, but fortunately for our friends the Diplos, the worn teeth were replaced by new ones.
To compensate for the low power of the jaws, the Diplodocus also swallowed stones that helped to grind food in the stomach. Once worn and rounded, these stones, called gastroliths, were discarded. Their appearance is characteristic and was found associated with many other Sauropods such as the French Ampelosaurus, a dinosaur which lived in France 70 million years later.
Because of their smaller size, young Diplodocus must have had a slightly different diet, consisting rather of young shoots, mosses, mushrooms, and small ferns.
The Diplodocus was therefore specialized in grazing plants, but this food is very poor from an energetic point of view. Like all Sauropods, the Diplodocus was therefore obliged to gulp down huge quantities of food to satisfy its needs. In other words, it probably had to eat all the time. It is easy to imagine the devastating impact of a herd of Diplodocus on the Jurassic forests. The luxuriance of this period, due to a more humid climate, allowed the Sauropods to expand considerably on all the continents, which were then separated into two groups (Laurasia and Gondwana).
It is, therefore, no coincidence that it is in the United States of America that the largest areas of Diplodocus have been found, in what is known as the Morrisson Formation. It corresponded to the Jurassic in a vast lush plain, covered with more or less dense tropical forests and eaten by herds of Sauropods. According to some paleontologists, the passage of a herd of Diplodocus could have razed entire forests, gradually replaced by steppes, and then becoming forests again after many years. Diplodocus herds would have been forced to live in perpetual migration.
The appetite of the Diplodocus depended largely on its metabolism ("warmblood" or "cold blood"). Warm-blooded animals (like Mammals and Birds) expend large amounts of energy to keep their temperature around a certain value, so they need more food. If the Diplodocus was a homeothermic animal, calculations show that it would have to ingest several tens of tons of plants every day! This argument has long been used to denigrate the warm-blooded dinosaur hypothesis. However, the imposing size of the adult Diplodocus must have been sufficient to allow certain thermal inertia: it must have taken a long time for them to warm up or cool down. Thus, even if they did not have the mechanisms to precisely control their temperature, the Diplodocus (like probably most Sauropods) still had to have a relatively constant internal temperature.
Representation of a sauropod feeding itself
The Diplodocus probably lived in herds of 20 to 30 individuals. Predators were never far away, on the lookout for the most vulnerable: carefree youngsters; sick; Diplodocus at the end of their lives... Unfortunately, there are no clues as to the organization of these herds: was there a dominant animal? If so, was it a male or a female? etc.
The growth of the Diplodocus probably continued throughout their lives, but at a lower rate than in childhood. Thus, rare bones discovered and attributed to the genus Diplodocus belonged to individuals over 44yd (40 meters long)! These must have been old Diplodocus, which lived long enough to reach such a size. Some paleontologists have suggested the possibility of several hundred years of age before reaching this respectable size.
It is possible to imagine a whole ecosystem living on the skin of the Diplodocus. This is not the place that was supposed to be missing! Little Pterosaurs could have come and clung to it, feeding on the insects and parasites living on the surface of the Diplodocus' skin, the droppings of these Pterosaurs ending up "coloring" the skin of their hosts?
The best defense of the Diplodocus was probably the imposing size of the adults. The only carnivores of the time to be able to compete with them were the Allosaurs. And yet, next to a 30-meter long Diplodocus, any Allosaur must have looked like a dwarf.
However, there is evidence that this theropod could very well attack such animals: traces of Allosaurus teeth have been found on the bones of Apatosaurus ( another sauropod ).
Allosaurus Skeleton, Cleveland-Lloyd Dinosaur Quarry museum, Utah, USA
In addition to a deterrent force (imposing size, tail slapping like a whip), the Diplodocus could probably protect itself by standing up on its hind legs during an attack, threatening its opponent with its claw on its front paw. It is likely that the Diplodocus then possessed ventral ribs ("gastralia") protecting its belly from a possible claw from an Allosaur.
On the contrary, young Diplodocus were much more vulnerable and at the mercy of small predators like the Ornitholestes. How long could this period of vulnerability last for the Diplodocus? The Diplodocus laid eggs the size of a rugby ball, so the newborns were only 40 inches long ( one meter ) when they hatched, compared to the 100 inches ( 2.5 meters ) of some Ornitholestes... Studies of the fossil bones of young Sauropods have shown that they have an exceptional early growth rate (around 2 kg/day in their early years), making them grow to a reasonable size in just a few years, protecting them from most predators.
Meanwhile, strength in numbers: of the number of young Diplodocus that emerge from the eggs laid by a herd, most will feast on the carnivores, letting some reach adulthood. The sacrifice of the newborn is part of the survival strategy of its species and thus allows the selection of those ablest to escape from their predators. This is the principle of natural selection...
Against large predators, the size of the young Diplodocus must surely allow them to take refuge in the depths of the forest. One can imagine that the color of their skin served as their camouflage clothing, but unless they resurrect these dinosaurs, the color of the dinosaurs' skin will remain a matter of pure speculation.
So, nothing surprising that the Diplodocus, this fascinating and surprising dinosaur, is often seen as the witness of the apogee of the Sauropods. The Sauropods have evolved until the disappearance of the dinosaurs, but the lightening of the skeleton has almost reached its peak here. The Diplodocus has long remained the longest known dinosaur, but it was dethroned in the 1970s by Supersaurus and Ultrasaurus. More recently, Paralititan, discovered in 2000, is more than 27 yd ( 25 meters ) long and the Argentinosaurus is more than 44 yd (40 meters long)!
The Diplodocus genus includes 5 species: Diplodocus longus (described in 1878 by Marsh), Diplodocus carnegii (described in 1901 by Hatcher), Diplodocus hayi (described in 1924 by Holland), Diplodocus lacustris (described in 1884 by Marsh) and Diplodocus hallorum (the new name of the species Seismosaurus halli).