Vulcanodon (meaning "volcano tooth") is an extinct genus of sauropod dinosaur from the Early Jurassic uppermost Forest Sandstone of southern Africa. The only known species is V. karibaensis. Discovered in 1969 in Zimbabwe, it was regarded as the earliest known sauropod for decades, and is still one of the most primitive genera 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 smaller than most other sauropods, measuring approximately 11 metres (36 ft) in length. Vulcanodon is known from a fragmentary skeleton including much of the pelvic girdle, hindlimbs, 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 they were omnivorous. Scientists now know that the teeth belonged to an unidentified theropod that may have scavenged on the Vulcanodon carcass, which is now known to be a true sauropod. Upon the discovery of the related Tazoudasaurus, both animals were unified in the family Vulcanodontidae, although this has not been universally accepted.
Description
Vulcanodon was initially thought have been a small sauropod. In 2010, Gregory S. Paul estimated its length at 11 metres (36.1 ft), its weight at 3.5 tonnes (3.9 short tons). Some books mention lower estimates of approximately 6.5 m (21 ft). However, in 2018, researchers have estimated a greater body mass of 10.3 metric tons (11.4 short tons). The thighbone was 110 centimetres (43 in) long. 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). 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. Its forelimbs were much more similar to later sauropods than basal sauropodomorphs because they are straight, much more gracile, and the proximal end of the ulna is v-shaped. Unfortunately, no skull or neck of Vulcanodon is known, although it is otherwise very well known.
Hindlimbs and pelvis
Vulcanodon's limbs were sturdy and column-like, and its forelimbs were already proportionally long, reaching 76% of hindlimb length. Its lower leg, metatarsus, and toes were shortened in comparison to its bipedal ancestors, but still not as short as in later sauropods. The sacrum was made out of 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 perforated pockets called pleurocoels. Contrasting the many sauropod-like features of the skeleton, the pelvis was relatively primitive, reminiscent of its "prosauropod" ancestors. One such feature is that the brevis shelf of the ilium has a fossa, which is not found in any more derived sauropods. The hallux (the first toe of the foot) showed a large claw that was flattened laterally, as seen in "prosauropods". However, the claws of the second and third toe were unusual in being nail-like and broader than deep. This feature was also found in the probably closely related Tazoudasaurus, but is absent in all other sauropods. The feet of Vulcanodon were semiplantigrade as in later sauropods (where both the digits and part of the metatarsals contact the ground), a derived feature not found in more basal sauropods like Isanosaurus. However, they also retained primitive features, like the fact that the phalanges were not reduced. Many of the features found in sauropods that basal sauropodomorphs lack are related to the change in body size. The greatest regions affected by this are the hind limbs and pelvis. For example, an elongating of the ilium, size reduction of the lesser trochanter shelf, and semiplantigrade posture are some features that indicate the amount and positioning of leg muscles being modified. Vulcanodon possessed these features, the latter of which is seen earliest in it. However, Vulcanodon does not have reduced distal phalanges, which are seen in Shunosaurus and all more derived sauropods. This means that while the muscle positioning of its legs were changing, they had not yet reduced in the distal region of the limb.
Discovery
… excerpt ends here. Continue reading the full article.
