Fossil range: Upper Cretaceous
Illustration of Thespesius from 1901.
Scientific classification












Thespesius Leidy, 1856


  • T. occidentalis Leidy, 1856 (type)

Thespesius (meaning "wondrous one") is a dubious genus of extinct hadrosaurid dinosaur based on two caudal vertebrae and a phalanx from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota (although at first thought to be from the Miocene).[1] Like Trachodon, another duckbill genus named by Joseph Leidy, it is an historically-important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists.[2]

Two other species of duckbill started out as species of Thespesius: T. saskatchewanensis,[3] now thought to be a species of Edmontosaurus;[4][5] and T. edmontoni,[6] now considered to be the same as Edmontosaurus annectens.[4][5] Both of them were included in Anatosaurus for many years.[7]


  1. ^ Leidy, J. (1856). Notice of extinct Vertebrata, discovered by Dr. F. V. Hayden during the expedition to the Sioux country under the command of Lieut. G.K. Warren. Proceedings of the Academy of Natural Science Philadelphia 8:311-312.
  2. ^ Creisler, B.S. (2007). Deciphering duckbills. in: K. Carpenter (ed.), Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Indiana University Press: Bloomington and Indianapolis, 185-210. ISBN 0-253-34817-X
  3. ^ Sternberg, C.M. (1926). A new species of Thespesius from the Lance Formation of Saskatchewan. Canada Department of Mines Geological Survey Bulletin (Geological Series) 44(46):73-84.
  4. ^ a b Weishampel, D.B., and Horner, J.R. (1990). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. University of California Press:Berkeley, 534-561. ISBN 0-520-24209-2
  5. ^ a b Horner, J.R., Weishampel, D.B., and Forster, C.A. (2004). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria (second edition). University of California Press:Berkeley, 438-463. ISBN 0-520-06727-4
  6. ^ Gilmore, C.W. (1924). A new species of hadrosaurian dinosaur from the Edmonton Formation (Cretaceous) of Alberta. Canada Department of Mines Geological Survey Bulletin (Geological Series) 38(43):13-26.
  7. ^ Lull, R.S., and Wright, N.E. (1942). Hadrosaurian Dinosaurs of North America. Geological Society of America Special Paper 40:1-242.

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