Open Paleo

Edmontosaurus

Lambe, 1917 ed-MON-tuh-SOR-uhs /ɛdˌmɒntəˈsɔːrəs/

From Edmonton (city in Alberta, Canada, near the formation where it was found) + Greek sauros, 'lizard'; means 'lizard from Edmonton'

83.6–66.0 million years ago Campanian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Edmontosaurus (meaning "lizard from Edmonton"), often colloquially and historically known as Anatosaurus or Anatotitan (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian age of the Cretaceous period 73 million years ago, while those of E. annectens were found in the same geographic region from rocks dated to the end of the Maastrichtian age, 66 million years ago. Edmontosaurus was one of the last non-avian dinosaurs ever to exist, and lived alongside dinosaurs like Triceratops, Tyrannosaurus, Ankylosaurus, and Pachycephalosaurus shortly before the Cretaceous-Paleogene extinction event.

Diagnosis

  1. Large pocket-like recess developed within the postfrontal, leading from the orbit, restricting the lateral temporal fossa in its upper half-length
  2. Skull high and broad posteriorly, flat in the frontal region, laterally compressed behind a low, greatly expanded snout; posterior height greater than half-length
  3. Ectopterygoid external to the maxillary and pterygoid, connecting the two
  4. Palatine and pterygoid rising at a high angle inward
  5. Teeth with rounded apical outline in lateral aspect, keeled, smooth-bordered; 48-49 vertical rows in dentary, 51-53 in maxillary
  6. Sacrum composed of eight vertebrae; cervical and dorsal vertebrae opisthocoeolous, markedly so in cervicals

Species (2)

Edmontosaurus regalis Lambe, 1917

Type species

From Latin 'regalis' meaning 'royal' or 'regal', reflecting the large and impressive nature of the type specimen.

Holotype
CMN 2288 , Canadian Museum of Nature
Material
Skull with most vertebrae back to sixth caudal, one hind limb, one humerus, both pubic bones, one ischium, greater part of right ilium, and some ribs.
Horizon
Horsethief Member, Horseshoe Canyon Formation, Campanian–Maastrichtian, Late Cretaceous , 83.6–66.0 million years ago
Locality
opposite the mouth of Three Hills Creek, Alberta, Canada

Edmontosaurus annectens (Marsh, 1892)

First named as Claosaurus annectens

Holotype
USNM 2414 , National Museum of Natural History, Smithsonian Institution
Material
Nearly complete skull and postcranial skeleton.
Notes
Marsh (1892) gives no number; Gilmore (1917) is the earliest paper read to give the type as No. 2414, U.S.N.M.
Horizon
Lance Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
north of Lightning and east of Bull creeks, Wyoming, United States
Diagnosis
  1. Ischial shaft markedly elongate and straight.
  2. Pubis with a large, expanded prepubic process and only a small remnant of the postpubic process.
  3. Prenarial region of the skull greatly elongated, especially at large size (skull length exceeding 1 m).
  4. Caudodorsal corner of the narial vestibule only weakly excavated.
  5. Postorbital fossa weakly developed, leaving the dorsal process of the jugal straight.

Synonyms

  • Anatotitan copei junior subjective

    Represents the largest, most mature ontogenetic stage of E. annectens; its long, low skull is explained by allometric scaling with size and individual variation, accentuated by dorsoventral crushing.

  • Claosaurus annectens reassigned

    Original combination; erected by Marsh (1892) as Claosaurus annectens and subsequently referred to Edmontosaurus.

  • Diclonius mirabilis junior subjective

    Included in the synonymy of E. annectens by Campione and Evans (2011).

  • Thespesius saskatchewanensis junior subjective

    Holotype CMN 8509 represents a juvenile ontogenetic stage of E. annectens, its proportions explained by allometric growth rather than distinct taxonomic status.

Synonyms of the genus

Name Type Reason
Anatosaurus junior subjective Material is now widely recognized as indistinguishable from Edmontosaurus.
Anatotitan junior subjective Originally erected as a replacement name for Anatosaurus; subsequent work demonstrated the material is referable to Edmontosaurus.
Ugrunaaluk junior subjective Now interpreted as juvenile material of Edmontosaurus; the exact species remains undetermined.

Notable specimens

  • AMNH mummy

    AMNH 5060 American Museum of Natural History Found 1908 by Charles Hazelius Sternberg and his sons exceptional preservation

    The "mummified" Trachodon mummy, with extensive preserved skin impressions known for most of the body. Carbonized possible gut contents were reported but never described. Found in 1908 in the Lance Formation near Lusk, Wyoming, and purchased by the museum for $2,000.

    Sereno et al. (2025)Sternberg (1909)

  • Senckenberg mummy

    SM 4036 Senckenberg Naturmuseum Found 1910 by Charles Hazelius Sternberg and his sons gut contents

    Second Sternberg mummy, with skin impressions and described plant gut contents (needles of the conifer Cunninghamites elegans, twigs, and seeds), debated as a true last meal versus washed-in debris. Also preserves rare scleral rings and substantial keratinous beak.

    Sereno et al. (2025)Kräusel (1922)Uhl (2020)

  • “Dakota”

    MRF-03, NDGS 2000 North Dakota Geological Survey Found 1999 by Tyler Lyson exceptional preservation

    A well-publicized "mummy" with preserved skin impressions apparently including remnant organic compounds from the skin. Discovered in 1999 in the Hell Creek Formation of North Dakota and announced in 2007.

    Manning et al. (2009)Drumheller et al. (2022)

  • LACM 23502

    Natural History Museum of Los Angeles County exceptional preservation

    Preserves a rhamphotheca, indicating the beak of Edmontosaurus was more hook-shaped and extensive than many scientific and public illustrations have depicted; whether it is the true rhamphotheca or a cast of the inner structure is uncertain.

    Morris (1970)

  • UCRC PV30

    University of Chicago Research Collection exceptional preservation

    Early adult "mummy" from the Lance Formation of east-central Wyoming preserving a row of interdigitating spikes over the mid and distal tail and wedge-shaped hooves capping the toes. With UCRC PV31, it gives a complete fleshy profile of a large-bodied dinosaur.

    Sereno et al. (2025)Saitta et al. (2026)

  • UCRC PV31

    University of Chicago Research Collection exceptional preservation

    Late juvenile "mummy" from the Lance Formation of east-central Wyoming preserving the fleshy midline crest over the trunk, deflected to one side while still pliable at death.

    Sereno et al. (2025)Saitta et al. (2026)

References

  1. Gilmore, C. W. (1917). Brachyceratops, a ceratopsian dinosaur from the Two Medicine Formation of Montana, with notes on associated fossil reptiles. United States Geological Survey Professional Paper 103: 1-45. United States Geological Survey.

    Gives the type of Trachodon annectens as "No. 2414, U.S.N.M.".

    gilmore1917a
  2. Lambe, L. M. (1917). A new genus and species of crestless hadrosaur from the Edmonton Formation of Alberta. The Ottawa Naturalist 31(7): 65-73. lambe1917a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  4. Sereno, P. C.; Saitta, E. T.; Vidal, D.; Myhrvold, N.; Ciudad Real, M.; Baumgart, S. L.; Bop, L. L.; Keillor, T. M.; Eriksen, M.; Derstler, K. (2025). Duck-billed dinosaur fleshy midline and hooves reveal terrestrial clay-template "mummification". Science 391(6780): eadw3536. doi:10.1126/science.adw3536

    Describes the UCRC mummies; source of the midline spike row and hooves.

    sereno2025a
  5. Sternberg, C. H. (1909). Expedition to the Laramie Beds of Converse County, Wyoming. Transactions of the Kansas Academy of Science 22: 113-116. doi:10.2307/3624729 sternberg1909a
  6. Kräusel, R. (1922). Die Nahrung von Trachodon [The food of Trachodon]. Paläontologische Zeitschrift 4: 80. doi:10.1007/BF03041547

    Title translates as "The diet of Trachodon"; in German.

    kräusel1922a
  7. Uhl, D. (2020). A reappraisal of the 'stomach' contents of the Edmontosaurus annectens mummy at the Senckenberg Naturmuseum in Frankfurt/Main (Germany). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 171(1): 71-85. doi:10.1127/zdgg/2020/0224 uhl2020a
  8. Manning, P. L.; Morris, P. M.; McMahon, A.; Jones, E.; Gize, A.; Macquaker, J. H. S.; Wolff, G.; Thompson, A.; Marshall, J.; Taylor, K. G.; Lyson, T.; Gaskell, S.; Reamtong, O.; Sellers, W. I.; van Dongen, B. E.; Buckley, M.; Wogelius, R. A. (2009). Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA). Proceedings of the Royal Society B 276(1672): 3429-3437. doi:10.1098/rspb.2009.0812 manning2009a
  9. Morris, W. J. (1970). Hadrosaurian dinosaur bills — morphology and function. Contributions in Science 193: 1-14. Natural History Museum of Los Angeles County. morris1970a
  10. Marsh, O. C. (1892). Notice of new reptiles from the Laramie Formation. American Journal of Science s3-43(257): 449-453. American Journal of Science (AJS). doi:10.2475/ajs.s3-43.257.449

    Erects the basionym Claosaurus annectens, later referred to Edmontosaurus.

    marsh1892a
  11. Campione, N. E.; Evans, D. C. (2011). Cranial growth and variation in edmontosaurs (Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore diversity in North America. PLoS ONE 6(9): e25186. Public Library of Science (PLoS). doi:10.1371/journal.pone.0025186

    Morphometric revision recognizing only two valid Edmontosaurus species and synonymizing Anatotitan copei and Thespesius saskatchewanensis into E. annectens.

    campione2011a
  12. Xing, H.; Wang, D.; Han, F.; Sullivan, C.; Ma, Q.; He, Y.; Hone, D. W. E.; Yan, R.; Du, F.; Xu, X. (2014). A New Basal Hadrosauroid Dinosaur (Dinosauria: Ornithopoda) with Transitional Features from the Late Cretaceous of Henan Province, China. PLoS ONE 9(6): e98821. Public Library of Science (PLoS). doi:10.1371/journal.pone.0098821

    Places the Edmontosaurus regalis holotype in the Horsethief Member, following the Horseshoe Canyon scheme of Eberth and Braman (2012).

    xing2014a
  13. Eberth, D. A.; Braman, D. R. (2012). A revised stratigraphy and depositional history for the Horseshoe Canyon Formation (Upper Cretaceous), southern Alberta plains. Canadian Journal of Earth Sciences 49(9): 1053-1086. Canadian Science Publishing. doi:10.1139/e2012-035 eberth2012a
  14. Saitta, E. T.; Sereno, P. C.; Vidal, D.; Ciudad Real, M.; Keillor, T. M.; Bop, L.; Baumgart, S. L.; Burdick, A.; Radermacher, V. J.; Kaye, T. G.; Dussubieux, L.; Maxey, E.; Filatov, A. S.; Chen, X. (2026). Dinosaur "mummification": Clay templating in a fluvial setting preserves three-dimensional integument renderings after carcass desiccation. Acta Palaeontologica Polonica 71(3): 535-579. Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). doi:10.4202/app.01349.2026

    Structural and chemical analysis of the UCRC mummies finding little evidence of endogenous organics; the integument is preserved as a clay template after subaerial desiccation and rapid burial.

    saitta2026a
  15. Drumheller, S. K.; Boyd, C. A.; Barnes, B. M. S.; Householder, M. L. (2022). Biostratinomic alterations of an Edmontosaurus "mummy" reveal a pathway for soft tissue preservation without invoking "exceptional conditions". PLOS ONE 17(10): e0275240. doi:10.1371/journal.pone.0275240

    Traces bite marks and decay on the Dakota mummy as a route to its soft-tissue preservation, measuring them against its segmented tail frill.

    drumheller2022a