| Diet | Herbivore |
| Height | 4m |
| Length | 22m |
| Weight | 12.7 tonnes |
| Environment | Land |
| Era | Jurassic |
| Period | Late Jurassic |
| Type | Sauropod |
| Location | North America |
Haplocanthosaurus was a massive sauropod dinosaur that thundered across the ancient landscapes of North America during the Late Jurassic period, around 155 to 152 million years ago. This gentle giant belonged to the diplodocoid group of sauropods, making it a relative of the famous Diplodocus, though it had its own unique characteristics that set it apart from its more well-known cousins.
Standing approximately 4 metres tall at the hip and stretching up to 22 metres from nose to tail, Haplocanthosaurus was an impressive sight. Despite its enormous size, weighing roughly 12.7 tonnes, this sauropod was actually considered medium-sized compared to some of its contemporaries. Its most distinctive feature was its relatively simple neural spines along its backbone, which gave the dinosaur its name meaning 'simple spine'.
Like all sauropods, Haplocanthosaurus was a herbivore that spent its days browsing on the abundant plant life of the Morrison Formation. Its long neck allowed it to reach vegetation at various heights, from ground-level ferns to tall conifer trees. The dinosaur's small head housed simple, peg-like teeth perfect for stripping leaves and soft plant material, which it would swallow whole to be processed in its massive digestive system.
Currently, scientists recognise two species of Haplocanthosaurus: H. priscus, the original species discovered in 1903, and H. delfsi, named after the young college student Edwin Delfs who found the fossils in Colorado. Both species shared the same time period and habitat, living alongside other famous dinosaurs including Allosaurus jimmadseni, Brontosaurus yahnahpin, and the armoured Hesperosaurus mjosi.
Haplocanthosaurus had notably simple, low neural spines along its backbone compared to other sauropods, giving it a less pronounced back ridge. Its neck was proportionally shorter than many of its diplodocoid relatives, and it possessed a more robust build overall.
Haplocanthosaurus likely lived in herds, moving slowly across the floodplains of the Late Jurassic in search of suitable vegetation. As a large sauropod, it would have spent most of its time feeding, requiring enormous quantities of plant matter daily to sustain its massive body.
Haplocanthus was first described by John Bell Hatcher in 1903. The original fossils were discovered at Morrison Formation, Colorado, USA.
