Supersaurus

Chapter • Meet the dinosaur

Overview

Supersaurus was a diplodocid sauropod and one of the longest land animals science has ever documented. Its body followed the familiar diplodocid blueprint seen in its close relative Diplodocus: an extraordinarily long neck, a barrel-shaped but surprisingly narrow torso, four pillar-like legs, and a whip-thin tail that made up close to half of the total length. What sets Supersaurus apart is sheer scale. Individual neck vertebrae exceed a metre in length, and the shoulder blade that first came out of the ground measures roughly 2.4 metres. The vertebrae were riddled with large air-filled cavities, which made the skeleton far lighter than its dimensions suggest. The animal walked on all fours at all times, carrying its neck and tail roughly horizontally rather than dragging the tail, as older artwork used to show. Because Supersaurus is known from limited material, its behaviour has to be inferred from better-preserved relatives and from trackways. Sauropod tracksites in the Morrison Formation often preserve several animals of the same kind moving in the same direction, suggesting that these giants could travel in loose herds, at least seasonally. The long neck most likely worked as a horizontal feeding reach, letting the animal strip vegetation from a wide arc without moving its enormous body. Growth-line studies on large sauropods indicate rapid growth to near-adult size within a few decades, followed by a long adult life. A fully grown Supersaurus had few natural enemies, but juveniles were probably vulnerable to predators such as Allosaurus and Torvosaurus. Supersaurus was strictly a plant eater. Diplodocids carried slender, peg-like teeth concentrated at the front of the mouth, ideal for raking conifer foliage, twig tips and ferns but useless for chewing. Food was swallowed almost whole and fermented in a vast gut with the help of microbes. An adult would have needed several hundred kilograms of plant matter per day, browsing both low among ferns and cycads and higher in the branches of conifers. The first bones were found in 1972 at the Dry Mesa Quarry in Colorado by collectors Vivian and Eddie Jones, and the animal was named in 1985 by James A. Jensen, who honoured Vivian Jones in the species name vivianae. Jensen also named Ultrasauros and Dystylosaurus from the same quarry; most researchers now regard Dystylosaurus as the same animal as Supersaurus. A more complete individual nicknamed "Jimbo" (WDC DMJ-021) was excavated in Wyoming and has helped refine body proportions. No skull has ever been found, so the head is reconstructed from Diplodocus and Barosaurus. In 2022 Brian Curtice and colleagues published new estimates that make Supersaurus a strong contender for the longest known dinosaur, at roughly 39–42 metres — figures that remain debated because the material is incomplete.

Chapter • Where it lived

Habitat

Supersaurus lived in the Late Jurassic, roughly 155–145 million years ago, in the landscape now preserved as the Morrison Formation of western North America. This was a broad lowland of braided rivers, seasonally flooded plains and ribbons of conifer forest along the watercourses, surrounded by more open ground covered in ferns, horsetails and cycads. The climate was warm with a pronounced dry season, which made river margins especially important feeding grounds. Fossils are known from the Dry Mesa Quarry in Colorado and from sites in Wyoming, where the more complete specimen "Jimbo" was recovered. Possible Portuguese material has been discussed, but those bones are usually assigned to the closely related genus Dinheirosaurus.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy