Spinophorosaurus

Phylogeny: Dinosauria > Saurischia > Sauropodomorpha > Plateosauria > Massopoda > Sauropodiformes > Sauropoda > Gravisauria > Eusauropoda (?)

Overview: While largely obscure to the general public, Spinophorosaurus is an important taxon, being known from some of the most complete fossil specimens of any basal sauropod. The first of said specimens was unearthed in 2005 by a team of German paleontologists, from the rocks of Niger’s Irhazer Shale. Said rocks date back to the Middle Jurassic and are situated beneath the more famous Tiourarén Formation. Putting together the type specimen with those found later, about seventy to eighty percent of the creature’s skeleton is known. The official description of Spinophorosaurus was published in 2009. Spinophorosaurus means “spine-bearing lizard”, referring to a set of pointed, spike-like bones that were found in association with the holotype. It was assumed that these spines were situated on the end of its tail, like those of stegosaurs, but later studies would prove these bones were actually pieces of collarbone.

The wealth of fossils associated with Spinophorosaurus has revealed not only a great deal about this genus itself, but also of the evolutionary history of sauropods in general. Some of its more distinctive traits included its fairly long forelimbs, upwardly inclined pelvis, its rigid tail base, and its unusual rib anatomy (the ribs at the front of its torso were very different from those towards the back). Spinophorosaurus appears to have been around fourteen meters long, so average-sized for a sauropod of its time. How exactly it should be classified has been debated for some years. Originally, it was seen as a very basal sauropod, outside the Eusauropoda, close to sauropods like Barapasaurus or even Vulcanodon. Most studies nowadays place it within the Eusauropoda, as a basal member or possibly as a relative of the Mamenchisauridae. Some scientists even see Spinophorosaurus as a possible example of a basal mamenchisaurid.