Vulcanodon

Vulcanodon (meaning "volcano tooth") is an extinct genus of sauropod dinosaur from the Early Jurassic of southern Africa. The only known species is V. karibaensis. Discovered in 1969 in Rhodesia (now known as Zimbabwe), it was regarded as the earliest known sauropod for decades, and is still one of the most primitive sauropods that has been discovered. As a quadrupedal, ground-dwelling herbivore, Vulcanodon already showed the typical sauropod body plan with column-like legs and a long neck and tail. It was much smaller than most other sauropods, measuring approximately 6.5 metres (20 ft) in length. Vulcanodon is known from a fragmentary skeleton including much of the pelvic girdle, hind limbs, forearms, and tail, but lacking the trunk and neck vertebrae as well as the skull.

Originally, this genus was believed to be a prosauropod because of the knife-shaped teeth found near its fossils, which fit in with the idea that prosauropods were omnivorous. Scientists now know that the teeth belonged to an unidentified theropod that may have scavenged on the Vulcanodon carcass. Vulcanodon is now known to be a true sauropod. Upon the discovery of the related Tazoudasaurus, both animals were unified in the family Vulcanodontidae, though this has not been universally accepted.

Etymology
Vulcanodon (lat. Vulcanus – Roman god of fire; gr. odon – "tooth")[1] was named by Michael Raath in 1972. The name points to the fact that the skeleton was found in a small body of sandstone that is sandwiched between two lava flows, and emphasizes the peculiar knife-shaped teeth that are now known to belong to a theropod.[2] The species name, karibaensis, refers to the place of discovery on a small island in Lake Kariba.

Description
Vulcanodon was a small sauropod, measuring approximately 6.5 metres (20 ft) in length.[3][4] As one of the earliest and basalmost sauropods, it is important for understanding the early evolution of this group. Sauropods descend from basal sauropodomorphs (informally called "prosauropods"), which were primitively bipedal (two legged).[5] While Vulcanodon already was fully quadrupedal (four legged), its limb proportions were intermediate between those of its prosauropod ancestors and those of later, more derived sauropods.[5] Its limbs were sturdy and column-like,[2] and its forelimbs were already proportionally long, reaching 76% of hindlimb length.[6] Its lower leg, metatarsus, and toes were shortened in comparison to its bipedal ancestors, but still not as short as in later sauropods.[5] The posture of the foot is unclear; it either was digitigrade as in "prosauropods" (only the digits touch the ground) or semiplantigrade as in later sauropods (both the digits and parts of the metatarsals touch the ground).[5] The sacrum was made out four fused sacral vertebrae; "prosauropods" possessed only three sacrals. The tail vertebra bodies already showed an incipient excavation of their lateral sides, saving weight and giving them a waisted appearance when viewed from below. In later sauropods, this excavations were enlarged to form extensive pockets called pleurocoels.[7] Contrasting the many sauropod-like features of the skeleton, the pelvis was relatively primitive, reminiscent of its "prosauropod" ancestors.[5]

The hallux (the first toe of the foot) showed a large claw that was flattened laterally, as seen in "prosauropods".[7] However, the claws of the second and third toe were unusual in being nail-like and broader than deep.[2][8] This feature was also found in the probably closely related Tazoudasaurus, but is absent in all other sauropods.