Vulcanodon
Vulcanodon | |
---|---|
Skeletal diagram showing the known remains | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | †Sauropodomorpha |
Clade: | †Sauropoda |
Clade: | †Gravisauria |
Family: | †Vulcanodontidae |
Genus: | †Vulcanodon Raath, 1972 |
Type species | |
†Vulcanodon karibaensis Raath, 1972
|
Vulcanodon (meaning "
Originally, this genus was believed to be a prosauropod because of the knife-shaped teeth found near its
Description
Vulcanodon was initially thought have been a small sauropod. In 2010, Gregory S. Paul estimated its length at eleven metres, its weight at 3.5 tonnes.[1] Some books mention lower estimates of approximately 6.5 m (21 ft).[2][3] However, in 2018, researchers have estimated a greater body mass of 10.3 metric tons (11.4 short tons).[4] The thighbone was 110 centimetres (43 in) long.[5]
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).[6] 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.[6] 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.[7] Unfortunately, no skull or neck of Vulcanodon is known, although it is otherwise very well known.[8]
Hindlimbs and pelvis
Vulcanodon's limbs were sturdy and column-like,
The
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.[11]
Discovery
Vulcanodon is known only from a single locality on an island in Lake Kariba, the largest artificial lake in the world, in northern Zimbabwe (formerly Rhodesia).[14] The island, located west of Bumi Hills,[5] is called "Island 126/127", after early, unpublished lake charts, but has no formal name. The first bone was found by B. A. Gibson of the town of Kariba in July 1969, and an excavation team collected the specimen in October 1969, March 1970 and May 1970. In the later half of 1970, the new find was presented at a scientific symposium in Cape Town and a brief note was published. The find was formally named and described in July 1972 by paleontologist Michael Raath.[9] The name Vulcanodon (lat. Vulcanus – Roman god of fire; gr. odon – "tooth")[15] points to the fact that the skeleton was found in sandstone, that was at the time misinterpreted to be part of the Batoka Formation but is actually part of the Forest Sandstone lays a few metres below the lava flows of the Batoka Formation, and emphasizes the peculiar knife-shaped teeth that are now known to belong to a theropod.[9] The specific name, karibaensis, refers to the place of discovery on a small island in Lake Kariba.[9] It was one of the first dinosaurs found in Zimbabwe.[16]
The skeleton (catalogue number QG24) has been found weathering out of a hill slope and was partially eroded by surface exponation and plant roots. It includes the pelvis and sacrum, most of the left hind limb and foot, a right thigh bone, and twelve anterior tail vertebrae. These remains pertain to a single individual as they were all found articulated (still connected together). Additionally, several disarticulated bones were found, including the right forearm and some
Raath (1972) noted the discovery of nine fragmentary carnivorous teeth near the pelvic region of the skeleton. He argued that the Vulcanodon carcass might have been embedded with the head and neck bended backwards above the pelvis, a posture called
Classification
Originally, Michael Raath (1972) described Vulcanodon not as a sauropod but as an
Michael Cooper (1984) erected a new
The exact relationships with other basal sauropod genera remain unclear. Ronan Allain and colleagues (2004, 2008) found that Vulcanodon is most closely related to Tazoudasaurus, a newly discovered sauropod genus from Morocco. These researchers suggested reintroducing the name Vulcanodontidae to name the clade containing Vulcanodon and Tazoudasaurus.[13][20] However, this sibling relationship between Tazoudasaurus and Vulcanodon could not be confirmed by other analyses.[21][22]
Adam Yates (2004) described a single sauropod tail vertebra from the
Vulcanodon in a cladogram after Nair et al., 2012:[24]
Paleoecology
During the later part of the Lower Jurassic, southern Africa was the scene of massive volcanism, resulting in extensive lava flows (so called flood basalts) that covered much of southern Africa and Antarctica. These basalt formations are known as the Karoo-Ferrar large igneous province. Vulcanodon comes from the "Vulcanodon beds", a fossil-bearing sediment unit within the Batoka Formation, which is composed primarily of flood basalts.[25] The skeleton was found near the top of a 30-metre-thick (98 ft) bedded layer of sand- and siltstone that is over- and underlain by flood basalts.[9]
It was long assumed that Vulcanodon lived during the lowermost (earliest) part of the Jurassic (the Hettangian stage) or at the Triassic–Jurassic boundary, approximately 200 million years ago.[10][17][19] Therefore, it was regarded as the earliest sauropod known, until the discovery of the even older Late Triassic Isanosaurus was announced in 2000.[26] Adam Yates (2004) has recently shown that Vulcanodon is actually much younger than previously thought, dating to the uppermost (latest) part of the Lower Jurassic during the Toarcian stage, approximately 175–183 million years ago.[23][27] Thus, it is contemporary to the closely related Tazoudasaurus.[20] Although the locality of Vulcanodon itself cannot be dated radiometrically because of weathering of the lavas, it would roughly be a contemporary to Karoo lavas from other localities, as the entire sequence of volcanic eruptions was finished within one million years.[23]
Vulcanodon is the only named dinosaur from the Vulcanodon beds.[25] Cooper (1984) noted that the habitat was desert-like, as indicated by aeolian (wind-blown) sands of the Forest Sandstone Formation, which underlies the "Vulcanodon beds". The sediments in which Vulcanodon was found may represent distal alluvial fan deposits which levelled off into a desert landscape, which may have contained lakes during the wet season. The individual may have roamed the shores of wadis that cut into the alluvial fan deposits, unless the carcass was transported to the locality it was found by flooding.[5]
Initially, sauropods were thought to be mainly aquatic, inhabiting lush peat swamps and being captive to the buoyancy of water to support their giant body weights.[28] In 1984, Cooper pointed out that Vulcanodon, the most primitive sauropod known at that time, lived in a desert like environment and therefore must have been terrestrial. This indicated that the large body size of sauropods, as already seen in Vulcanodon, had not evolved as an adaptation to an aquatic life style.[5]
References
- ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 172
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- ^ a b c d e f g h i j k Cooper, Michael R. (1984). "A reassessment of Vulcanodon karibaensis Raath (Dinosauria: Saurischia) and the origin of the Sauropoda". Palaeontologia Africana. 25: 203–205, 211–213, 223, 230–231.
- ^ ISBN 978-0-520-24623-2.
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- ^ a b c d e f g h i j Raath, Michael A. (1972). "Fossil vertebrate studies in Rhodesia: a new dinosaur (Reptilia, Saurischia) from near the Triassic-Jurassic boundary". Arnoldia. 5: 1–2, 4.
- ^ .
- ^ a b c Fechner, R. (2009). "Morphofunctional Evolution of the Pelvic Girdle and Hindlimb of Dinosauromorpha on the Lineage to Sauropoda" (PDF). Fakultät für Geowissenschaften der Ludwigs Maximilians Universität: 111–133.
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- ^ ISBN 978-0-520-25408-4.
- ^ Cruickshank, A. R. I. 1975. Origin of sauropod dinosaurs. South African Journal of Sciences, 71, 89-90.
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