Vulcanodon
Name:
Vulcanodon
(Volcano tooth).
Phonetic: Vul-can-o-don.
Named By: Michael Raath - 1972.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha, Sauropoda, Gravisauria,
Vulcanodontidae.
Species: V. karibaensis
(type).
Diet: Herbivore.
Size: Holotype individual dimensions include
following; Fore leg - humerus 70 centimetres, radius 64.7 centimetres,
ulna 66 centimetres. Hind leg - Femur 110 centimetres, tibia 63.4
centimetres. Total length of preserved portion of the skeleton
estimated at 6.5 meters, however this figure does not include the neck
and skull. Total size uncertain until neck vertebrae are found, but
certainly longer than 6.5 meters.
Known locations: Zimbabwe, Lake Kariba, Island
126/127 - Vulcanodon Beds Formation.
Time period: Toarcian of the Jurassic (see main
text for more detail).
Fossil representation: Partial but articulated post
cranial remains, including pelvis, limbs and vertebrae.
Vulcanodon
is easily one of the more popular dinosaur genera, and one that has
had a number of ‘firsts’ attributed to it. However, our
understanding of this genus and changed considerably since it was first
described in 1972. The name Vulcanodon means
‘volcano tooth’
and is a reference to the discovery of Vulcanodon
between two
Jurassic aged lava beds (long cooled down). The word volcano is
derived from the latin vulcano, which in turn is derived from
Vulcanus, more commonly known in English as Vulcan, the ancient
Roman god of fire.
The
post cranial remains of Vulcanodon were first found
in 1969 by B.
A. Gibson on a small Island in Lake Kariba of Zimbabwe (at the
time known as Rhodesia). Lake Kariba is actually an artificial lake
and reservoir created by the construction of the Kariba Dam, and the
location where the fossils were found is simply known as Island
126/127. The remains were collected over the course of three
expeditions in October 1969, and March and May 1970. Later in
1970 brief notes about the fossils were presented to a symposium in
Cape Town, South Africa. No more public information about the
fossils appeared until their formal scientific description was
released in 1972.
When
first described by Michael Raath in 1972, Vulcanodon
was marked
down as a prosauropod
(in more modern terms, a sauropodomorph)
dinosaur on the basis of the form of the pelvis and the teeth, the
latter of which were suited to processing meat and hence indicating an
omnivorous diet. The original explanation for these teeth being found
at the pelvis was relocation from a death pose commonly seen in
dinosaur remains. This is caused by the contraction of the tendons in
the neck after death and during decomposition which causes the neck and
head to arc backwards to look like they are curving over the back.
These teeth however are now known to have been left behind by a
theropod dinosaur and not the Vulcanodon, and
were most likely left
behind when said theropod was feeding upon the body of the Vulcanodon.
The
pelvis of Vulcanodon is very much like those of
sauropodomorph
dinosaurs, though in this case it also seems to have been a
proverbial ‘red herring’. The true nature of Vulcanodon
being a
sauropod
was indicated in a 1975 paper by Arthur Cruickshank who noted
that the fifth metatarsal (one of the foot bones) is the same
length as the others,a feature seen in sauropods, not
sauropodomorphs. With this more attention was given to the other
parts of the skeleton, and with the exception of the pelvis,
everything fitted a sauropod body form. Today, Vulcanodon
is
recognised as a potentially transitional sauropod which gives us some
clues as to how sauropodomorphs evolved a larger, quadrupedal body
form to become the first sauropods, the pelvis being an archaic
feature that had remained in Vulcanodon, but
would disappear from
later sauropod forms.
With
Vulcanodon now correctly described as a sauropod,
it became
recognised as the earliest known appearance of a sauropod dinosaur.
This is because the fossil bed that the Vulcanodon
holotype was
found in was believed to date to the early Hettangian, possibly the
Triassic/Jurassic boundary. Two things have happened since this time
though which now tell us that Vulcanodon was not
the first sauropod to
appear on the face of the planet. The first is rather simply the
2000 description of Isanosaurus
from Thailand, which is a sauropod
known to have lived around the Norian/Rhaetian stages of the Triassic,
comfortably before the Hettangian stage of the Jurassic. The second
is a study conducted by Adam Yates in 2004 that covered the lava
beds that Vulcanodon was found in. These beds
cannot be accurately
dated with radiometric techniques, but the weathering upon them
indicates that they are of the same age as other lava beds in the Karoo
Basin which were laid down over a course of about one million years
during the Toarcian period of the Mid Jurassic. This study then means
that the Vulcanodon genus roughly lived about one
hundred and eighty
million years ago (give or take a few million years) instead of
about two hundred and forty-five million years ago. Given the slight
mix of sauropodomorph features such as the pelvis, and Vulcanodon
may
even be a late surviving transitional form.
When
Vulcanodon was realised to be sauropod, and at the
time thought to be
a very early one, palaeontologists considered the possibility of
creating a new group of sauropods. This finally happened in 1984
when Michael Cooper created the Vulcanodontidae. This group was
primarily centred around Vulcanodon as the type
genus, hence the name
usage, and Barapasaurus
from India, though the genera
Zizhongosaurus
and Ohmdenosaurus
have also been included within this
group by others. The first problems started with Zizhongosaurus
and
Ohmdenosaurus which are known from remains that are
so fragmentary that
not all palaeontologists are convinced about the validity of these
genera. This left Vulcanodon and Barapasaurus
together, but then
in 1995 a study by Paul Upchurch revealed that Barapasaurus
was
quite a bit more advanced than Vulcanodon, and
therefore cannot be
kept in the same group. This left Vulcanodon all
on its own, and
since you need more than one of anything to have a group, the
Vulcanodonidae fell into disuse by the majority of palaeontologists.
Then
in 2004 a new genus of sauropod called Tazoudasaurus
was named from
fossils discovered in Morocco. Also known from partial remains,
Tazoudasaurus is noted for only really differing
from Vulcanodon only
in the form of the vertebrae. This has not only led to suggestions
that Tazoudasaurus and Vulcanodon
are closely related, but it has
also seen some (but at the time of writing not all)
palaeontologists recognising the Vulcanodontidae as a valid group
again, This time with Vulcanodon and Tazoudasaurus
as the main
genera, but occasionally also seeing the inclusion of Zizhongosaurus
again, though this genus is still considered dubious by many. One
of the signature features of sauropod genera in this group is that
members must have a particularly narrow sacrum, the part of the hip
where the sacral vertebrae are sandwiched between the ilium bones.
As
a living dinosaur, Vulcanodon would have been a
very small sauropod
dinosaur, and one that would not be classifiable with the ‘true
sauropods’ that would soon become the dominant sauropod form a little
later in the Jurassic. This is not to say that Vulcanodon
was not a
sauropod, it was, just that the sauropods are broken down into
groups for easier classification amongst genera, and Vulcanodon
is
considered to be too primitive to be grouped with forms such as
Cetiosaurus
and Apatosaurus.
Although
not perfectly adapted to a quadrupedal posture, Vulcanodon
almost
certainly went about in one. The fore limbs are three quarters of the
length of the hind limbs, meaning that the back would have been
vertically level to maybe slanting slightly down towards the neck.
Vulcanodon also had a claw on the hallux (first
toe) of the foot,
another feature common to sauropodomorphs, but the second and third
toes of Vulcanodon had claws that were wider than
they were long.
At the time of writing these foot claws are only seen in Vulcanodon
and Tazoudasaurus.
Analysis
of the fossil location of Vulcanodon suggests that
in life these
sauropods lived in very arid environments, possibly feeding upon the
plants that sprang up around watering holes or perhaps feeding
excessively during wet seasons and surviving more upon fat reserves
during the dry season. This is of course presuming that the body was
not deposited to said environment by means of seasonal flood water,
but only the discovery of new Vulcanodon fossils
and analysis of their
fossil sites can find that out.
Vulcanodon
is often quoted as being six and a half meters long, but this is
actually the estimated length of the preserved portion of the skeleton
which does not include the neck or skull. How long Vulcanodon
was
specifically would depend upon the length of the neck, which until
further fossils are found, can only really be guessed at. Still, Vulcanodon
was
certainly within the predatory scope of the larger theropod dinosaurs
of the time, possibly those like Berberosaurus,
remains of which
were found nearby Tazoudasaurus further North in
Morocco. It is not
known what genus the theropod teeth found with the Vulcanodon
fossils
belonged too, but they do reveal the presence of meat eating
dinosaurs where the body of this individual Vulcanodon
came to rest.
Further reading
- Fossil vertebrate studies in Rhodesia: a new dinosaur
(Reptilia, Saurischia) from near the Triassic-Jurassic boundary
- Michael Raath - 1974.
- A reassessment of Vulcanodon karibaensis Raath
(Dinosauria:
Saurischia) and the origin of the Sauropoda - Michael R.
Cooper - 1984.
- The Evolutionary History of Sauropod Dinosaurs - Paul Upchurch
- 1995.
- First record of a sauropod dinosaur from the upper Elliot
Formation (Early Jurassic) of South Africa - Adam M. Yates,
John P. Hancox, Bruce S. Rubidge - 2004.
- Integrating ichnofossil and body fossil records to estimate
locomotor posture and spatiotemporal distribution of early sauropod
dinosaurs: a stratocladistic approach - Jefferey A. Wilson -
2005.
- Anatomy and phylogenetic relationships of Tazoudasaurus
naimi
(Dinosauria, Sauropoda) from the late Early Jurassic of Morocco
- Ronan Allain, Najat Aquesbi - 2008.
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