Dicraeosaurus

Type Species: Dicraeosaurus hansemanni

Classification: Dinosauria – Saurischia – Sauropoda – Gravisauria - Eusauropoda - Neosauropoda - Diplodocoidea - Flagellicaudata – Dicraeosauridae

Time Period: Late Jurassic

Location: Africa (Tanzania) 

Diet: Herbivore   

The small-sized sauropod Dicraeosaurus lived in eastern Africa in what is now modern Tanzania. Its remains have been uncovered in the Tendago Formation, which dates from the Middle Jurassic to the Early Cretaceous and which is divided into six ‘zones’ corresponding to different time periods. The Tendagu Formation of the Late Jurassic was located in the subtropical southern hemisphere, and it would’ve been a semi-arid environment with seasonal rainfall. The Tendagu has given us a wealth of fossils from this period in earth’s history, not only dinosaurs but also early mammals, crocodylomorphs, amphibians, fish, invertebrates, and flora. The environment in which Dicraeosaurus lived included a coastal region of beaches and lagoons; further inland were coastal plains with brackish lakes and ponds. Dicraeosaurus lived among other herbivores such as the brachiosaurid Giraffatitan and the stegosaur Kentrosaurus; it may have been hunted by the carcharodontosaur theropod Veterupristisaurus. 

Dicraeosaurus’ name means ‘two forks’ in reference to the neural spines of the backbone that branched (or ‘forked’) in two. In life, this was likely a ridged back of fleshy skin. This type of backbone design is rare, and it’s far more pronounced in the later Amargasaurus. The ridged back came from the neural spines that projected upwards from its backbone, running from its tail to its neck. Each spine opened out at the top to form a ‘Y’ shape to which muscles were attached. Some scientists believe these were bony anchors for a thin, low, sail-like structure. The sail would’ve made it look bigger in profile as a deterrent to predators; or it may have served as a display for species recognition or attracting mates, in which case it was likely brightly colored or vibrantly patterned; another theory is that the sail would’ve served for thermoregulation. In the latter case, the large area of the sail, when positioned at a right angle to the rising sun, would’ve absorbed warmth and passed it, via the blood flowing through it, into the animal’s system. This would quickly raise the animal’s body temperature to allow more and faster activity after the cool of night; conversely, standing in the shade and at a right angle to the breeze would cool the body. 

Dicraeosaurus had a relatively short, wide neck with only twelve vertebrae, less than any other late Jurassic sauropods other than Brachytrachelopan. Its tail had the typical diplodocid ‘whiplash,’ though it was nowhere near as ‘whippy’ as more derived (and larger) diplodocids. Its eyes were set high atop its skull; its snout was long, low, and horse-like; and its teeth were fine and pencil-shaped, set in two curved clusters toward the front of the jaws. These teeth were designed for stripping foliage. The design of its neck – coupled with its low stature – meant that it fed at ground level up to ten feet off the ground.