Amphicoelias
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Amphicoelias was a genus of sauropod dinosaur, which may have included the largest dinosaur ever discovered (A. fragillimus). If it truly existed, A. fragillimus would be the longest vertebrate by a considerable margin, and it would have a mass that rivals the heaviest animal known, the blue whale. However, because the only fossil evidence for its existence was lost shortly after being discovered in the 1870s, evidence survives only in drawings, and doubt has been expressed about their veracity.
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[edit] Discovery
The paleontologist Edward Drinker Cope discovered a partial vertebra (the neural arch) of a new species at the Morrison Formation, near the town of Morrison, Colorado. It was in poor condition, but astonishingly large, measuring 2.4 m (7.8 ft.) in height. A. fragillimus is estimated to have lived 140 to 150 million years ago, which places it in the late Jurassic period, specifically the Kimmeridgian to Tithonian ages.
The neural arch was packaged and sent by train to a Museum in New York, but unfortunately it never arrived; apparently it crumbled to dust while en route. The only evidence remaining of its existence is the description and a line drawing in a scientific journal.
[edit] The Bone Wars
The validity of the find is complicated by its discovery in the midst of the Bone Wars, an infamous period in the history of paleontology, when the two pre-eminent paleontologists of the time, Othniel Charles Marsh and Edward Drinker Cope, were competing to see who could find the most, and most sensational, new species. This competition was marred by bribery, accusations of theft, spying, politics, and virulent personal attacks.
Marsh was winning the bone war. He discovered a total of 86 new species during their decades-long rivalry, due in part to his discovery of the Como Bluff site, near Medicine Bow, Wyoming, one of the richest sources of fossils ever uncovered. Cope only discovered 56; many of the fossils he unearthed were of species that had already been named, or were of uncertain origin, so he was not credited with their discovery. As a result, Marsh's name is attached to many of the most famous dinosaurs, such as Triceratops, Allosaurus, Diplodocus, and Stegosaurus, while even Cope's most famous discoveries, such as Dimetrodon (not actually a dinosaur), Camarasaurus, Coelophysis, and Monoclonius are more obscure. So while there is no evidence of falsification, the circumstances surrounding Amphicoelias do raise some doubt about the authenticity of the find.
[edit] The crumbling giant
The dorsal vertebra of A. fragillimus measured 2.4 m (7.8 ft) long. Comparing it with known species of diplodocid (a family of extremely long and slender sauropods), various estimates of the animal's length and mass include:
- A length of 56–62 m (185–200 ft.), and a weight of 125–170 t (140–185 tons)
- A length of 50 m (165 ft.), and a weight of 120–150 t (130–165 tons).
- A length of 45 m (150 ft.), and a weight of 100–150 t (110–165 tons).
- A length of 45–60 m (150–195 ft.).
- A length of 37-60 m (125-200 feet), and a weight of 50-150 tons
By comparison the blue whale, which is the longest living creature, only reaches 30–33 m (100–110 ft.) in length, and the longest dinosaur for which solid evidence exists, Seismosaurus, is estimated to be only about 46 m (150 ft.) long.
While A. fragillimus was relatively thin, its enormous size still makes it very massive. The heaviest blue whale on record weighed about 177 t (195 tons), which is just slightly larger than the upper range of estimates for Amphicoelias. For the sake of comparison, the heaviest dinosaur that we have good evidence for, the Argentinosaurus, only weighed 80–100 t (90–100 tons), although if the size estimates can be validated, it would still be lighter than Bruhathkayosaurus, which is estimated to weight 175–220 t (190–240 tons) (based on a poor description of a partial fossil).
[edit] Classification
Edward Drinker Cope described his find in an 1878 issue of the American Naturalist, and named it A. fragillimus. He classified it as a diplodocid, specifically a new species in the genus Amphicoelias.
The genus Amphicoelias is poorly known. The first named species in the genus, Amphicoelias altus (holotype specimen AMHD 5764), was discovered by Cope the year before, in 1877. But while it is only represented by a partial skeleton, there are enough diagnostic characteristics to provisionally define the genus. A. altus is known from slightly better remains, but is smaller than A. fragillimus. McIntosh (1998, Modern Geology 23:481-506) stated in 1998 that there is no reason to suspect the two are different species. "A. fragillimus" is probably just a very large individual of A. altus.
[edit] Etymology
Amphicoelias fragillimus is derived from the Greek amphi ("on both sides"), koilos ("hollow, concave"), -ias ("in character"), and fragillimus ("very fragile"). Cope used it to refer to the thinness of the bone, but the name turned out to be very appropriate.
[edit] References
- Cope, Edward Drinker (1878). A new species of Amphicoelias. American Naturalist XII: 563–563. (See external links, below.)
- McIntosh, J. S. (1998). New information about the Cope Collection of sauropods from Garden Park, Colorado. Modern Geology 23: 481–506.
[edit] External links
- A drawing of A. fragillimus.
- Dino Data's date sheet on Amphicoelias fragillimus.
- Discussion on the Dinosaur Mailing List:
- The Dinosauricon's cladogram (see also cladistics).
- A new species of Amphicoelias (scanned copy of Cope's original article).
