Welcome to our AMPHICOELIAS entry...
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a diplodocoid sauropod dinosaur from the Late Cretaceous of North America.
Pronunciation: AM-fi-SEEL-ee-as
Meaning: Double hollow (biconcave)
Author/s: Cope (1877)
Synonyms: None known
First Discovery: Colorado, USA
Chart Position: 38

Amphicoelias altus

Amphicoelias altus, a diplodocid around 30 meters long and 30 tons in weight, was named by paleontologist Edward Drinker Cope in December 1877 (though it wasn't published until 1878) for an incomplete skeleton consisting of two vertebrae, a pubis (hip bone), and a femur (upper leg bone) discovered in stratigraphic zone 6 of Colorado's Morrison Formation, but the real story lies with a much larger species...

Amphicoelias fragillimus

Amphicoelias fragillimus was shaping up to be the biggest dinosaur ever, and eclipsed even the Blue Whale in length when applying proportionate upscaling based on better-represented relatives to Edward Drinker Cope's sketches of a partial colossal vertebrae found by Oramel Lucas at Colorado's Garden Park in 1877. Unfortunately, despite its humungous size, it was "misplaced" along with an equally huge partial femur found a short distance away, and all attempts to locate it have been in vain.

It's not beyond the of realms of possibility that Cope, obsessed with one-upping his arch rival during their infamous machismo driven bone wars, was telling fibs. But reputations were at stake, and the fact that Othniel Charles Marsh, who often sent spies to keep tabs on Cope and his discoveries, didn't publicly question the measurements of his find speaks volumes for its validity. Given its "fragillimus" state and a lack of fossil-hardening preservatives available at the time, it may have just crumbled to dust where it lay.

In 1921 Amphicoelias fragillimus was provisionally synonomyzed with Amphicoelias altus by H.F. Osborn and C. C. Mook who noted similarities to Diplodocus. Then, in 2007, John Foster rocked paleontology to its core when he suggested that these similarities were actually identicalities and that Diplodocus should probably be synonymized too. The cross section of the thigh bone which paleontologists clung to as a means to separate Amphicoelias altus from Diplodocus is now known to occur in Diplodocus too, and if they do represent the same critter then the latter name would be sunk as the former was coined first.

The vertebra of Amphicoelias fragillimus, however, sports features not found in either Amphicoelias altus or Diplodocus. Separated at the species level by Cope, the former may actually represent a different type of sauropod entirely, but before it can be granted its own name the original remains need to be pinpointed for closer scrutiny, and the chances are slim.
Amphicoelias latus
Amphicoelias latus was found at the same site as Amphicoelias altus whose name is virtually identical. It is possible that Cope confused himself and accidentally flip-flopped the first two letters of their epithets as he scribbled their names in his notebook, but he did assign the former its own holotype (AMNH 5765); four caudal vertebrae and a right femur which, despite being extraordinary robust, has been misplaced. Nevertheless, the bits that were available to study are closer in form to those of Camarasaurus than to those of Amphicoelias, which led Osborn and Mook to assign them to Camarasaurus supremus in 1921.
"Amphicoelias brontodiplodocus"
In 2010, a monograph was made available (but not formally published) by Henry Galiano and Raimund Albersdorfer in which they referred a new species to Amphicoelias—"Amphicoelias brontodiplodocus"—based on several complete specimens found in the Dana Quarry of Big Horn Basin. Shockingly this "paper" sunk every Morrison formation diplodocid plus a few from elsewhere into Amphicoelias altus and the only other diplodocid the authors considered valid was their new and ridiculously named critter—literally "Both sides hollow thunder double beam". Unsuprisingly this theory didn't get much support from paleontologists, which in hindsight was justified. In exchange for a bagful of cash, a specimen named "Sleeping Beauty" found itself mounted in a Dubai shopping centre in 2014 with the unbelievably mundane "DubaiDino" hanging around its neck after Saudi banker Johara Al Bayedh won a naming contest sponsored by the Emaar Malls Group. And guess what? It's a confirmed species of Diplodocus longus, the only mounted specimen made up entirely of original fossilized bone, no less. It's such a shame that kids will be monkey-swinging from its ribs and carving their names into its toes while it should be in a museum undergoing serious scientific study.
Amphicoelias is derived from the Greek "amphi" (both sides), "koilos" (hollow) and "ias" (in character) in reference to the biconcave form of its vertebra.
The Species epithet - altus - means "high" or "elevated" in Latin.
The Species epithet - fragillimus - means "very fragile" in Latin.
The fossils of both A. altus and A. fragillimus were recovered from Colorado's Morrison formation in 1877. Cope originally called this "the Dakota formation".
A. altus (AMHD 5764) consists of two vertebrae, a hip bone, and a femur.
A. fragmilis (AMNH 5777) is a single colossal vertebra. Despite having a number reserved for it by the AMNH, records show that it never arrived in New York! Cope's field notes contain an entry for an "immense distal end of femur” located only tens of meters away from the vertebra, which probably belonged to the same individual.
Era: Mesozoic
Epoch: Late Jurassic
Stage: Oxfordian-Kimmeridgian
Age range: 156-151 mya
Est. max. length: 58 meters
Est. max. hip height: 9 meters
Est. max. weight: 120 tons
Diet: Herbivore
• Cope, Edward Drinker (Dec 10th, 1877) "On Amphicoelias, a genus of Saurians from the Dakota epoch of Colorado". Paleontological Bulletin no. 27. Page 2.
• Cope E.D. (Dec 21st, 1877) "On the Vertebrata of the Dakota Epoch of Colorado". Proceedings of the American Philosophical Society Vol. 17, No. 100, page 233-247.
• Cope E. D. (Feb 1st, 1878) "On the Saurians Recently Discovered in the Dakota Beds of Colorado". The American Naturalist. Printed Jan 31st, 1878. Page 82.
• Cope E. D. (August 1878) "A new species of Amphicoelias". The American Naturalist, vol. 12, page 563-565.
• H. F. Osborn and C. C. Mook (Jan. 1921) "Camarasaurus, Amphicoelias and other sauropods of Cope". Memoirs of the American Museum of Natural History, volume 3, part 3.
• Tidwell & Carpenter (2005) "Thunder-Lizards: The Sauropodomorph Dinosaurs".
• Kenneth Carpenter (2006) "Biggest of the Big: A Critical Re-Evaluation of the Mega-Sauropod Amphicoelias fragillimus Cope, 1878".
• J. Foster (2007) "Jurassic West: Dinosaurs of the Morrison Formation and their world".
• H. Galiano and R. Albersdörfer (2010) "A new basal diplodocid species, Amphicoelias brontodiplodocus from the Morrison Formation, Big Horn Basin, Wyoming, with a taxonomic reevaluation of Diplodocus, Apatosaurus, Barosaurus and other genera".
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To cite this page:
Atkinson, L. "AMPHICOELIAS :: from DinoChecker's dinosaur archive".
›. Web access: 17th Jan 2018.