Barosaurus
Name:
Barosaurus
(heavy lizard).
Phonetic: Bar-roe-sore-us.
Named By: Othniel Charles Marsh - 1890.
Synonyms: Barosaurus affinis.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha, Sauropoda, Diplodocidae,
Diplodocinae.
Species: B. lentus (type).
Diet: Herbivore.
Size: Up to about 27.5 meters long (based upon
ROM 3670).
Known locations: USA, including the states of
Colorado, Oklahoma, South Dakota, Utah and Wyoming -
Morrison Formation.
Time period: Late Kimmeridgian of the Jurassic.
Fossil representation: Partial post cranial remains
of several individuals.
The
modern history of the sauropod
dinosaur Barosaurus
begins in 1889
with the discovery of the first Barosaurus fossils
by a Ms E. R.
Ellerman in South Dakota. Six caudal (tail) vertebrae were
subsequently recovered by the famous American palaeontologist Othniel
Charles Marsh later that year, though other remains were left at the
site until such time that they could be safely recovered and
transported. In 1898 one of Marsh’s assistants, George Weiland
recovered these remains which included limbs, ribs and more
vertebrae, and allowed for the identification of Barosaurus
as a
diplodocid sauropod. Later, fossils of Barosaurus
were the last to
ever be described by Charles Othniel Marsh before his death in 1899.
These were two metatarsals assigned to a new species, B.
affinis,
though today this species is treated as a synonym to the type
species, B. lentus.
Today
Barosaurus is known by the remains of several
individuals that have all
been recovered from the Kimmeridgian aged deposits of the famous
Morrison Formation. As already mentioned, Barosaurus
is a
diplodocid sauropod, which means that it was of the kind that were
very long with slender necks and tails that were whip-like on the end.
It should be mentioned at this point that the end of the tail of
Barosaurus is still unknown at the time of writing,
but it would be
highly unusual for a diplodocid to not have a whip-like tail.
Barosaurus can be further classified as a
diplodocine diplodocid
rather than an apatosaurine diplodosaurid. Diplodocines are classed
under the Diplodocinae and they are different to the apatosaurines
(classed under the Apatosaurinae) in that they are more gracile
(lightly built) than their heavier cousins.
The
main features that make Barosaurus unique to other
diplodocids are in
the vertebrae, and usually Barosaurus is compared
to the famous
Diplodocus
and Apatosaurus
. Both Diplodocus
and Apatosaurus
have fifteen cervical (neck) and ten dorsal (back) vertebrae.
Barosaurus is known to have had fifteen cervical
vertebrae but only
nine dorsal vertebrae. Where the tenth dorsal vertebra went to is
unknown, but it’s possible that it may have over time adapted to
become a sixteenth cervical vertebrae. The cervical vertebrae of
Barosaurus were also up to one and a half times
longer than the
cervical vertebrae of Diplodocus meaning that Barosaurus
would have
proportionately longer neck than Diplodocus. The
caudal (tail)
vertebrae of Barosaurus however were
proportionately shorter than
those of Diplodocus, meaning that the overall
length of the tail
would have been shorter in Barosaurus. The neural
spines of the
vertebrae in Barosaurus are also shorter and less
complex than those of
Diplodocus.
Much
of the post cranial skeleton of Barosaurus is
known, though there are
two glaring omissions; the feet and the head. Barosaurus
is
actually not an exception, the feet and skulls are the two most
commonly missing parts when sauropod remains are found. This is
because they are fairly small and jointed and therefore can become
easily detached from the rest of the skeleton before preservation. As
a diplodocid, Barosaurus would be expected to
have had a skull
similar to relative genera, elongated with a sloping snout, housing
peg-like teeth for stripping vegetation from branches.
Aside
from being similar to Diplodocus and Apatosaurus,
Barosaurus also
seems to have shared the same habitats as them as well. Another
sauropod named Haplocanthosaurus
may have also come into contact with
Barosaurus. In addition to these, macronarian
sauropods such as
Camarasaurus
and Brachiosaurus
would have also been present on the same
landscapes as Barosaurus. There would have course
been other
dinosaurs such as herbivores like Stegosaurus,
Camptosaurus
and
Mymoorapelta,
and predators such as Ornitholestes,
Torvosaurus,
Saurophaganax
and Allosaurus.
Barosaurus may have fallen prey to
some of these larger predators, though the smaller juveniles would
have been at more of a risk than fully grown adults.
For
a time Barosaurus was once thought to have lived in
Africa as well as
North America. This all comes down to a 1907 discovery of two
sauropod skeletons by a German palaeontologist named Eberhard Fraas,
who at the time thought that he was creating a new genus of sauropod
named Gigantosaurus.
However, the name Gigantosaurus had already
been named for a more obscure set of sauropod remains from England,
so a new genus was erected for them by Richard Sternfeld and named
Tornieria in 1911. Fossils of Tornieria africana
however were
re-assigned by another German palaeontologist named Werner Janensch to
Barosaurus. Since this however, other
palaeontologists have
questioned the reasoning of such a move. One species formerly known
as T. robustus was re-examined in 1991 and
revealed to be a
titanosaurs and added to its own new genus Janenschia.
Other material
once assigned as T. africanus was confirmed to be
different to known
North American diplodocids in 2006, which saw a subsequent
resurrection of the Tornieria genus. This also
rather obviously means
that Barosaurus remains known only from North
American deposits.
ROM
3670
One
of the most exciting discoveries, or rather rediscoveries concerning
Barosaurus happened in 2007. Palaeontologist and
curator of the
Royal Ontario Museum David Evans spotted a reference to a Barosaurus
skeleton that had been traded with the Carnegie Museum and sent to the
Royal Ontario Museum in 1962. Strangely, these fossils don’t seem
to have made it out of storage upon arriving and just disappeared from
everyone’s memory. Realising that there might be a scientifically
valuable specimen somewhere in the museum, Evans searched the storage
bays and began finding the fossils of the missing Barosaurus.
This
Barosaurus specimen is known as ROM 3670, though
those who visit
and work with it know it better as ‘Gordo’. With the rediscovery
plans were immediately put into motion to set up a new display,
though in order to get the display ready, not all of the fossil
casts could be mounted in time. In fact more bones of Barosaurus
were
still in storage several years after this mounting was completed which
means that it may be re-mounted but more completely in the future.
Unfortunately the skull is still not known, so the one that appears
upon the display is that of a Diplodocus, which
should at the very
least be a fairly close match.
ROM
3670 is valuable for two reasons. With more fossils of this
dinosaur coming out of storage, it may actually be the most complete
Barosaurus skeleton so far recovered. This
skeleton also seems to
have come from an individual which seems to have grown up to
twenty-seven and a half meters long, making it the largest individual
Barosaurus known.
Further reading
- Description of new dinosaurian reptiles - Othniel Charles
Marsh - 1890.
- The sauropod dinosaur Barosaurus Marsh:
redescription of the type
specimens in the Peabody Museum, Yale University - Richard S,
Lull - 1919.
- Sauropod dinosaurs of the Morrison Formation (Upper Jurassic),
Black Hills, South Dakota and Wyoming - John R. Foster -
1996.
- A phylogenetic analysis of Diplodocoidea (Saurischia:
Sauropoda) J. A. Whitlock - 2011.
- The neck of Barosaurus was not only longer but
also wider than those
of Diplodocus and other diplodocines. - PeerJ Preprints. 1: e67v1. -
Michael P. taylor & Mathew J. Wedel - 2013.
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