Dino of the Week: Spinophorosaurus

Type Species: Spinophorosaurus nigerensis

Classification: Dinosauria – Saurischia – Sauropoda - Gravisauria 

Time Period: Middle Jurassic

Location: Africa (Niger) 

Diet: Herbivore 

The sauropod Spinophorosaurus was discovered in the late 2000s. The remains of two individuals were discovered in what had been, during the Bajocian-Bathonian stages of the Middle Jurassic, a river-valley system of lakes and rivers. Spinophosaurus was one of the first dinosaurs to have its skeleton 3D printed, and these prints were used to test locomotion and movement (by which it was determined that it was a high browser) and to experiment with different sauropod sex positions (naughty but fascinating!). Spinophosaurus reached thirty-eight feet in length, stood thirteen feet tall at the hips, and weighed around seven tons. It had tall shoulders and an elevated neck, giving it a vertical rather than horizontal posture (akin to the later Brachiosaurus and its contemporary Saharan sauropod Atlasaurus). Its braincase was short, deep, and broad, and it shows similarities between basal sauropodomorphs and more derived neosauropods. Its teeth were spoon-shaped and had large denticles at the top of the crown, an ancestral feature found in sauropods. Its neck is one of the most completely known among sauropods, and it contained thirteen vertebrae. The dorsal vertebrae had multiple air-filled internal chambers, something found in more derived sauropods such as the titanosauriforms and mamenchisaurids (two families which evolved them separately in cases of ‘convergent evolution’). Its tail was powered by strong musculature and had a rear section that was rigid due to long, overlapping chevron bones. 

Most artistic depictions of Spinophorosaurus (such the one below) depict it with two symmetrical pairs of long, sharp spikes reminiscent of those seen in the Jurassic stegosaurs. When Spinophorosaurus was uncovered, skeletal elements interpreted as a left and right osteoderms were found. These bones had a roundish base from which a spike-like projection protruded; the inner surfaces were rugose and concave. Although these bones were found in the pelvic region, the first scientists to study this sauropod believed that in life they were positioned at the tip of the tail, much like the later Shunosaurus had a tail club. However, this interpretation has recently fallen out of favor. Though the stiffening of Spinophorosaurus’ hind tail by elongated chevrons is observed in armored dinosaurs bearing clubs or spikes, Spinophorosaurus’ hindmost caudal vertebrae were likely too small to wield the weight of such a weapon. Later scientists pointed out that the osteoderms were not truly symmetrical and slightly differed in shape; this indicates that they didn’t form a pair but were more likely the mirror-inverted counterparts of one another. What, then, were these bones about? The current theory – embraced by further study in both 2015 and 2018 – is that these elements, which were found under the scapula, belonged to Spinophorosaurus’ clavicle. Although the image of a spike-wielding sauropod in prehistoric Saharan Africa is a wonderful one, it may not be reality.