The tallest dinosaur known, Sauroposeidon (meaning "earthquake lizard-god") is an Early Cretaceous sauropod connected to the Brachiosaurus. The only example to date is represented by four neck vertebrae.
Who's the biggest?
"It's truly astonishing. It's debatably the largest creature ever
to walk the earth."
— Richard Cifelli, discoverer of Sauroposeidon
The press release in 1999 right away garnered international media attention, which led to many (inaccurate) news reports of "the largest dinosaur ever!” While it is true that the Sauroposeidon is almost certainly the tallest known dinosaur, it is neither the best nor the most massive. The Supersaurus, the Seismosaurus, and the Argentinosaurus are better candidates for the title "World's Largest Dinosaur", though weak fossil proof makes an exact ranking impossible.
The Sauroposeidon find was calm of four articulated, mid-cervical vertebrae (numbers 5 to 8), with the cervical ribs in place. The vertebrae are very elongated, with the largest one about 1.2 meters (4 feet) long, which makes it the best on record. Examination of the bones exposed that they are honeycombed with tiny air cells, and are very thin, like the bones of a chicken or an ostrich, creation the neck lighter and easier to lift.
Estimates of size are based on a contrast between the four Sauroposeidon vertebrae and the vertebrae of the HM SII specimen of Brachiosaurus brancai, situated in the Humboldt Museum in Berlin. The HM SII is the most whole brachiosaur known, though since it is composed of pieces from dissimilar individuals its proportions may not be totally accurate. Comparisons to the other brachiosaurid cousins of the Sauroposeidon would be hard due to limited remains.
The neck length of the Sauroposeidon is predictable at 37 to 39.5 feet (11.25 to 12 meters), compared to a neck length of 30 feet (9 meters) for the HM SII Brachiosaurus. This is based on the supposition that the rest of the neck has the same proportions at the Brachiosaurus, which is a sensibly good conjecture.
The Sauroposeidon was probably able to raise its head 60 feet (18 meters) above the ground, which is as high as a six-story building. The long neck and the high brachiosaurid shoulders are what make it the tallest recognized dinosaur. In some ways, its build is similar to the contemporary giraffe, with a short body and an extremely long neck. In comparison, the brachiosaur could almost certainly raise its head 45 feet (13.5 meters) into the air, and the previous record holder, the Diplodocus, might have been able to raise its head 50 feet (15 meters).
The Sauroposeidon's shoulders were probably 22 to 24 feet (7 meters) off the ground. Its estimated length is just less than 100 feet (30 meters).
The mass of the Sauroposeidon is predictable at 50 to 60 metric tonnes (55 to 65 tons). While the vertebrate of the Sauroposeidon are 25–33% longer than the brachiosaur's, they are only 10–15% larger in diameter. This means that while the Sauroposeidon almost certainly has a larger body than the Brachiosaurus its body is lesser in comparison to the size of its neck, so it did not weigh as much as a scaled-up brachiosaur. By comparison, the brachiosaur strength has weighed 36 to 40 tonnes (40 to 44 tons). This estimate of the brachiosaur is an average of several dissimilar methodologies.
However, Sauroposeidon has a comparatively gracile neck compared to the Brachiosaurus. If the rest of the body turns out to be similarly slender, the mass approximation may be too high. This could be alike to the way the relatively chunky Apatosaurus weighs far more than the longer but much slimmer Diplodocus. In addition, it is likely that sauropods may have an air sac system, like those in birds, which could decrease all sauropod mass estimates by 20% or more.
"Sauroposeidon was an unforeseen discovery, because it was a huge, gas-guzzling barge of an animal in an age of subcompact sauropods."—Matt Wedel, Sauroposeidon team leader The Sauroposeidon may be the last of the giant North American sauropods. Sauropods, which comprise the main 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 previous to they spread across the world. By the time of the late Jurassic, North America and Africa were under enemy control by the diplodocids and brachiosaurids, and by the end of the Late Cretaceous, titanosaurids were widespread. But in the middle, in the Early Cretaceous, the fossil evidence is sparse. Most of the other sauropods at the time were dying out, and as a consequence few specimens have been found in North American from that time, and those specimens that do exist are often fragmentary or stand for juvenile members of their species. Most of the surviving sauropods at the time were also shrinking in size (to a mere 50 feet, or 15 meters, in length, and maybe 10 to 15 tons or tonnes), which makes the discovery of an very specialized super-giant like the Sauroposeidon very unusual.
The Sauroposeidon lived on the shores of the Gulf of Mexico, which ran from side to side 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 the Acrocanthosaurus (an Allosaurus a little smaller than a T. rex), and packs of Deinonychus.
The vertebrae were exposed, not far from the Texas border, in a clay stone outcrop that dates the fossils to about 110 million years ago (mya). This falls within the Early Cretaceous, specifically between the Aptian and Albian epochs.
The four neck vertebrae were exposed in 1994 at the Antlers Formation in Atoka County, Oklahoma by Dr. Richard Cifelli and a team from the Oklahoma Museum of Natural History.
While exposed in 1994, the vertebrae were stored until three years later, when Dr. Cifelli gave them to a graduate student, Matt Wedel, to examine as part of a project. After realizing the meaning of the find, a press release was made in October of 1999, followed by official publication in the Journal of Vertebrate Paleontology in March of 2000. The new species was dubbed S. proteles, and the holotype is OMNH 53062.
The genera name comes from sauros (Greek for "lizard"), and Poseidon (a sea-god in Greek mythology, who is also linked with earthquakes). The species name proteles also comes from the Greek, and means "perfect before the end" — which refers to the Sauroposeidon's rank as the last, and most specialized giant sauropod known in North America during the Early Cretaceous.