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a questionable chasmosaurine ceratopsid dinosaur from the Late Cretaceous of North America.
Pronunciation: ag-uh-THAW-mas
Meaning: Great wonder
Author/s: E.D. Cope (1872)
Synonyms: None known
First Discovery: Wyoming, USA
Chart Position: 26

Agathaumas sylvestris

Discovered in 1872 by F.B. Meek and H.M. Bannister while scouring the Lance Formation (then called the Laramie) for fossil shells during Ferdinand Hayden's Geological Survey of the territories, Agathaumas sylvestris—"equal in size to the largest known terrestrial saurians and mammals" and at that time the largest land animal known to have lived in North America—came as quite a surprise.

Its name—meaning "Great Wonder of the forest"—was coined later the same year by an excited E.D. Cope on the strength of a legless rear-end that he initially compared to Hadrosaurus and Dryptosaurus, and then to Cetiosaurus. In fact, the only type of "saurian" he didn't compare it to was a ceratopsid (horn-faced dinosaur) and there's a simple enough reason for that; a horn-faced dinosaur had yet to be discovered.

Cope's soon-to-be bone wars nemesis—O.C. Marsh of Yale University—was the first to click that horn-faced dinosaurs existed as he coined Ceratops horridus for some skull fossils from the Laramie in 1888. This epiphany led to the realisation that his Ceratops montanus, found by J.B. Hatcher near Montana's Cow Creek the previous year had a horned face too and that Bison alticornis, named the year before that, wasn't actually a huge Pliocene-aged Bison after all. Marsh now had enough relatives to raise Ceratopsidae to house these three strange beasts, but not without resistance. Citing the paucity of Ceratops remains and unconvinced they were any different to those he had named Agathaumas seventeen years earlier, Cope insisted on using Agathaumidae for this family.

Bison was shunted into Ceratops later in 1889 while Ceratops horridus became the holotype of Triceratops, and based on the size and shape of Agathaumas it's probably a Triceratops too. Strictly speaking, Cope's critter should have had priority name-wise, but there are three reasons why this was never going to happen; (1) we can't be certain that Agathaumas and Triceratops are the same, (2) you can't replace the holotype of a horn-faced critter with a specimen that doesn't actually have a face, never mind a face with horns on it, and (3) the definitive 1907 monograph on horned dinosaurs was written by Marsh and his buddies from Yale. Old Cope was on a hiding to nothing from the jump, and his Agathaumas is little more than an historical curiosity.
(Great Wonder of the Forest) Etymology
Agathaumas is derived from the Greek "agan" (great, much) and "thauma" (wonder), alluding to its great size.
The species epithet, sylvestris, (Latin for "forest") was chosen because the fossil sticks and leaves in the same rocks as its bones suggested a forest environment.
The fossils of Agathaumas were found at Black Buttes, 80 km east of Green River, in the Lance Formation (then called the Laramie Formation) of Wyoming by Fielding Bradford Meek and H.M. Bannister - hunting for fossil shells as part of Ferdinand Hayden's Geological Survey of the Territories - in 1872. Its discovery between ancient coal seams confirmed a Late Cretaceous age for this formation, rather than a Tertiary age, as long thought. The holotype consists of 16 vertebrae from the tail, sacrum and back, some hip bone fragments and several ribs.
Era: Mesozoic
Epoch: Late Cretaceous
Stage: Maastrichtian
Age range: 67-66 mya
Est. max. length: 9 meters
Est. max. hip height: 3 meters
Est. max. weight: 7 tons
Diet: Herbivore
• E.D. Cope (1872) "On the existence of Dinosauria in the Transition Beds of Wyoming".
• E.D. Cope (1873) "The monster of Mammoth Buttes".
• E.D. Cope (1889) "The horned Dinosauria of the Laramie".
• J. B. Hatcher, O. C. Marsh and R. S. Lull (1907) "The Ceratopsia". United States Geological Survey Monograph 49:1-300.
• Peter Dodson (1998) "The Horned Dinosaurs: A Natural History". Princeton University Press.
• Brent H. Breithaupt (1999) "The First Discovery of Dinosaurs in the American West" in David D. Gillette (ed.) "Vertebrate Paleontology in Utah".
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To cite this page:
Atkinson, L. "AGATHAUMAS :: from DinoChecker's dinosaur archive".
›. Web access: 20th Feb 2018.