Diplodocus

Where It Lived

Diplodocus lived during the Late Jurassic period, around 150 million years ago, in what is now the western United States. At that time, the region formed part of the Morrison Formation - a vast basin where rivers flowing east from the rising Rocky Mountains deposited layers of mud, sand, and silt across broad floodplains, lakes, and river channels. The climate was warm and semi-arid, with distinct wet and dry seasons that brought periods of heavy rain followed by long spells of dryness. This landscape supported a diverse community of life: other large sauropods such as Apatosaurus and Brachiosaurus, predators like Allosaurus, and plant-eaters including Stegosaurus and Camptosaurus. Smaller reptiles, early mammals, turtles, and crocodile-like animals lived alongside them, while pterosaurs glided overhead. The vegetation was dominated by conifers, cycads, ginkgoes, and ferns, with mosses and horsetails in wetter areas - an environment well suited to sustaining the giant herbivores of the Jurassic.

Discovery

Size and Description

Behavior and Activity

Because Diplodocus is known from so many well-preserved skeletons, scientists have been able to study almost every aspect of its biology in detail. Early paleontologists once imagined it as a slow, semi-aquatic creature that spent much of its time wallowing in swamps, supported by water. This idea came partly from the position of its nostrils high on the head, which seemed suited for breathing while submerged. But later research showed that the immense water pressure on the chest would have made underwater breathing impossible. Since the 1970s, studies have firmly established that Diplodocus was a land-dwelling herbivore, feeding among trees, ferns, and low vegetation.

Comparisons of the eye bones, called scleral rings, suggest that Diplodocus may have been active in short bursts throughout both day and night - a pattern known as cathemeral behavior. Scientists study the ratio between the opening in the scleral ring and the overall size of the eye socket, which in living birds and reptiles correlates with how much light their eyes are adapted to gather. Species active mainly at night tend to have proportionally larger openings, while daytime species have smaller ones. The measurements for Diplodocus fall between these ranges, implying it could see well in varying light conditions and was probably active at intervals across the day. However, this method only gives clues about light sensitivity rather than behavior itself, so while the results are suggestive, they aren't definitive.

Breathing and Circulation

Like other sauropods, Diplodocus faced biological challenges due to its size, particularly in breathing and circulation. Its long neck would have created a large "dead space" of air that made breathing less efficient if it relied on a reptile-like or mammal-like system. Most scientists now think it had an avian-style respiratory system, with air sacs that extended into the neck bones and allowed a continuous flow of air through the lungs, much like modern birds. This would have provided the oxygen needed to sustain such a massive body. Its heart and blood pressure systems remain subjects of debate - some earlier models suggested the need for "auxiliary hearts" to pump blood up the long neck - but most researchers now believe that its largely horizontal neck posture minimized the problem.

Neck Posture and Movement

That neck posture has been another area of shifting interpretations. Early reconstructions showed Diplodocus with its neck arched upward like a giraffe, but modern evidence suggests that its neck was usually held horizontally, supported by strong ligaments running from the back toward the head. This would have allowed it to sweep its head over wide feeding areas without expending much energy lifting it high. This posture appears to have been typical of Diplodocus and its close relatives, while other sauropods such as Brachiosaurus and Camarasaurus carried their necks more steeply, allowing them to feed from taller vegetation.

Some biomechanical models suggest that Diplodocus could rear up on its hind legs, using its powerful tail as a prop, potentially reaching food several meters above ground. However, later research suggests that this would have been very energy-intensive and probably not something the animal did often. Most scientists now think Diplodocus fed primarily by moving its neck side-to-side at roughly shoulder height, occasionally stretching higher when needed but rarely, if ever, adopting a full rearing posture.

Feeding Behavior

Reproduction and Growth

Little direct evidence survives of how Diplodocus reproduced, but studies of related sauropods indicate that it probably laid small eggs in shallow pits, possibly communally, to reduce the risk of predation. Despite their giant size, sauropod eggs were relatively small and numerous, allowing quick incubation. Growth studies of bone tissue show that Diplodocus grew rapidly, reaching adult size within a few decades, though some individuals, like D. hallorum, may have continued growing slowly for much longer.