Sauroposeidon

Taxobox
name = "Sauroposeidon"
fossil_range = Early Cretaceous

---

image_width = 201px
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Sauropodomorpha
infraordo = Sauropoda
familia = Brachiosauridae
genus = "Sauroposeidon"
genus_authority = Wedel "et al", 2000
subdivision_ranks = Species
subdivision = "S. proteles" Wedel "et al.", 2000 (type)

"Sauroposeidon" (pronounced SAWR-o-po-SIE-don, meaning "earthquake-lizard god"cite journal|last=Wedel|first=Mathew J.|coauthors=Cifelli, Richard L.|year=2005|month=Summer|title="Sauroposeidon": Oklahoma's Native Giant|journal= Oklahoma Geology Notes|volume=65|issue=2|pages=40–57|doi=|url=http://sauroposeidon.net/Wedel-Cifelli_2005_native-giant.pdf|format=PDF] [According to Wedel "et al" (2005), the etymology of the name is based on Poseidon's association with earthquakes, not the sea.] ) is a genus of sauropod dinosaur known from four neck vertebrae that were found in the southwestern portion of the US state of Oklahoma. The fossils were found in rocks dating to the Early Cretaceous, a period when the sauropods of North America had diminished in both size and numbers, making it the last known giant dinosaur on the continent. While the fossils were discovered in 1994, due to their unexpected age and unusual size they were initially misclassified as pieces of petrified wood. A more detailed analysis in 1999 revealed their true nature which resulted in a minor media frenzy, and formal publication of the find the following year.cite journal|last=Wedel|first=Mathew J.|coauthors=Cifelli, Richard L.; Sanders, R. Kent|year=2000|month=|title=Osteology, paleobiology, and relationships of the sauropod dinosaur "Sauroposeidon"|journal=Acta Palaeontologica Polonica|volume=45|pages=343–3888|doi=|url=http://sauroposeidon.net/Wedel-et-al_2000b_sauroposeidon.pdf|format=PDF]

Paleoecological analysis indicates it lived on the shores of the Gulf of Mexico, in a river delta. Like other brachiosaurids, "Sauroposeidon" was a quadrupedal herbivore with longer forelimbs than hindlimbs, a similar body design to the modern giraffe. Extrapolations based on its more completely known relative "Brachiosaurus" indicate that the head of "Sauroposeidon" could reach convert|17|m|ft|abbr=on in height with its neck extended, making it the tallest known dinosaur. With an estimated length of convert|30|m|ft|abbr=on and a mass of convert|36|-|40|MT|ST|abbr=on it also ranks among the longest and heaviest.

Discovery

The vertebrae were discovered in rural Oklahoma, not far from the Texas border, in a claystone outcrop that dates the fossils to about 110 million years ago (mya). This falls within the Early Cretaceous Period, specificially between the Aptian and Albian epochs.

The four neck vertebrae were discovered in 1994 at the Antlers Formation in Atoka County, Oklahoma by Dr. Richard Cifelli and a team from the Oklahoma Museum of Natural History. Initially the fossils were believed to be simply too large to be the remains of an animal, and due to the state of preservation, believed to be tree trunks. In fact, they are the longest such bones known in dinosaurs.

Thus, the vertebrae were stored until 1999, when Dr. Cifelli gave them to a graduate student, Matt Wedel, to analyze as part of a project. Upon their realization of the find's significance, they issued a press release in October 1999, followed by official publication of their findings in the "Journal of Vertebrate Paleontology" in March 2000. The new species was dubbed "S. proteles", and the holotype is OMNH 53062.

Etymology

The generic name comes from "sauros" (Greek for "lizard"), and "Poseidon", a sea-god in Greek mythology, who is also associated with earthquakes, that facet styled as Ennosigaios or Enisokhthōn, "Earthshaker". This is a reference to the notion that a sauropod's weight was so great that the ground shook as it walked.

The specific descriptor "proteles" also comes from the Ancient Greek and means "perfect before the end", which refers to "Sauroposeidon's" status as the last and most specialized giant sauropod known in North America, during the Early Cretaceous.

ize

The press release in 1999 immediately garnered international media attention, which led to many (inaccurate) news reports of "the largest dinosaur ever!". While it is true that "Sauroposeidon" is probably the tallest known dinosaur, it is neither the longest nor the most massive. "Argentinosaurus" is a better candidate for the title "World's Largest Dinosaur", though weak fossil evidence makes an exact ranking impossible.

The "Sauroposeidon" find was composed of four articulated, mid-cervical vertebrae (numbers 5 to 8), with the cervical ribs in place. The vertebrae are extremely elongated, with the largest one having an overall length of convert|1.4|m|ft|abbr=on, making it the longest sauropod neck vertebra on record. Examination of the bones revealed that they are honeycombed with tiny air cells, and are very thin, like the bones of a chicken or an ostrich, making the neck lighter and easier to lift.cite journal|last=Wedel|first=Mathew J.|coauthors=Cifelli, Richard L.; Sanders, R. Kent|year=2000|month=March|title="Sauroposeidon proteles", a new sauropod from the Early Cretaceous of Oklahoma|journal=Journal of Vertebrate Paleontology|volume=29|issue=1|pages=109–114|doi=|url=http://sauroposeidon.net/Wedel-et-al_2000a_sauroposeidon.pdf|format=PDF] The cervical ribs were remarkably long as well, with the longest measurable rib (on vertebra 6) measuring convert|3.42|m|ft|abbr=on – about 18% longer than the longest rib reported for "Brachiosaurus", but exceeded in length by the cervical ribs of "Mamenchisaurus".

Estimates of "Sauroposeidon"'s size are based on a comparison between the four "Sauroposeidon" vertebrae and the vertebrae of the HM SII specimen of "Brachiosaurus brancai", located in the Humboldt Museum in Berlin. The HM SII is the most complete brachiosaur known, though since it is composed of pieces from different individuals its proportions may not be totally accurate. Comparisons to the other brachiosaurid relatives of "Sauroposeidon" are difficult due to limited remains.

The neck length of "Sauroposeidon" is estimated at convert|11.25|-|12|m|ft|sigfig=2|abbr=on, compared to a neck length of convert|9|m|ft|abbr=on for the HM SII "Brachiosaurus". This is based on the assumption that the rest of the neck has the same proportions as "Brachiosaurus", which is a reasonably good conjecture.

"Sauroposeidon" was probably able to raise its head convert|17|m|ft|abbr=on above the ground, which is as high as a six-story building. The long neck and the high brachiosaurid shoulders are what makes it the tallest known dinosaur. In some ways, its build is similar to the modern giraffe, with a short body and an extremely long neck. In comparison, "Brachiosaurus" could probably raise its head convert|13.5|m|ft|abbr=on into the air.

"Sauroposeidon's" shoulder height was probably convert|6|-|7|m|ft|abbr=on and its estimated length is just under convert|30|m|ft|abbr=on.

The mass of "Sauroposeidon" is estimated at convert|50|-|60|MT|ST|abbr=on. While the vertebrae of "Sauroposeidon" are 25–33% longer than "Brachiosaurus"', they are only 10–15% larger in diameter. This means that while "Sauroposeidon" probably has a larger body than "Brachiosaurus" its body is smaller in comparison to the size of its neck, so it did not weigh as much as a scaled-up "Brachiosaurus". By comparison, "Brachiosaurus" might have weighed convert|36|-|40|MT|ST|abbr=on. This estimate of the "Brachiosaurus" is an average of several different methodologies.

However, "Sauroposeidon" has a relatively gracile neck compared to "Brachiosaurus". If the rest of the body turns out to be similarly slender, the mass estimate may be too high. This could be similar to the way the relatively robust "Apatosaurus" weighs far more than the longer but much slimmer "Diplodocus". In addition, it is possible that sauropods may have had an air sac system, like those in birds, which could reduce all sauropod mass estimates by 20% or more.

Palaeoecology

"Sauroposeidon" may be the last of the giant North American sauropods. Sauropods, which include the largest terrestrial animals of all time, were a very wide ranging and successful group. They first appeared in the Early Jurassic and it wasn't long before they spread across the world. By the time of the late Jurassic, North America and Africa were dominated by the diplodocids and brachiosaurids and, by the end of the Late Cretaceous, titanosaurids were widespread (though only in the southern hemisphere). Between these periods, in the Early Cretaceous, the fossil record is sparse. Few specimens have been found in North America from that time and those specimens that do exist are often fragmentary or represent juvenile members of their species. Most of the surviving sauropods at the time were also shrinking in size to a mere convert|15|m|ft|abbr=on in length, and maybe convert|10|-|15|MT|ST|abbr=on, which makes the discovery of an extremely specialized super-giant like "Sauroposeidon" very unusual.

"Sauroposeidon" lived on the shores of the Gulf of Mexico, which ran through Oklahoma at that time, in a vast river delta, similar to the Mississippi delta today. There were probably no predators who could take down a full-grown "Sauroposeidon" but juveniles were likely prey to "Acrocanthosaurus" (a carnosaur a little smaller than a "T. rex") and to 'packs' of "Deinonychus".

A giant brachiosaurid, similar to "Sauroposeidon", was described in 2004 by Darren Naish and colleagues and is from the Early Cretaceous period of England. Known only from two neck vertebrae, it was apparently similar in some details to "Sauroposeidon" and perhaps similar in size. Its discovery highlights the similarity seen between Early Cretaceous North American and European dinosaurs.

References

External links

* A non-technical [http://www.geocities.com/CapeCanaveral/Galaxy/8152/largest.html article] on Dino Land, with links to various news reports.