DinoDex
Large striped duck-billed dinosaur walking on four legs in side view
Life reconstruction of Edmontosaurus, a large hadrosaurid from the Late Cretaceous of North America.Image credit: TotalDino, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing)CC BY-SA 4.0 (unmodified)Source (opens in a new tab)

Edmontosaurus annectens

Pronounced ed-MON-toh-SORE-us ah-NEK-tenz

Ornithopoda · Hadrosauridae

A large duck-billed dinosaur from the very end of the Cretaceous in western North America, a common plant-eater of the Hell Creek and Lance formations and prey of T. rex. Several "mummies" preserve its skin.

  • Skin impressions known
  • Exceptional preservation
  • Famous specimen
Compare
Period
Cretaceous· Maastrichtian
Diet
Herbivore
Length
12–15 m
Mass
5,600–15,900 kg
Location
Wyoming, Montana, South Dakota, North Dakota, Saskatchewan, United States, Canada

Quick answers

How big was Edmontosaurus annectens?
Edmontosaurus annectens was about 12–15 m long. It stood about 2.6–3.4 m tall at the hips. It weighed about 5.6–15.9 t. (Wikipedia: Edmontosaurus 2026; Paul 2016)
When did Edmontosaurus annectens live?
Edmontosaurus annectens lived during the Late Cretaceous, about 72.1–66 million years ago. (Paleobiology Database: Edmontosaurus occurrences 2026; Campione & Evans 2011)
Where have Edmontosaurus annectens fossils been found?
Fossils of Edmontosaurus annectens have been found in Lance Formation (Wyoming), Hell Creek Formation (Montana), Frenchman Formation (Saskatchewan), United States, and Canada. (Marsh 1892; Lambe 1917)
What did Edmontosaurus annectens eat?
Edmontosaurus annectens was a herbivore. (Marsh 1892; Lambe 1917)
Who named Edmontosaurus annectens, and when?
Edmontosaurus annectens was described by Othniel Charles Marsh in 1892. (Marsh 1892; Campione & Evans 2011)

On this page

ed-MON-toh-SORE-us ah-NEK-tenz

Period
Cretaceous72.1–66 Ma
Diet
Herbivore
Length
12–15 m
Mass
5.6–15.9 t
Location
United States, Canada
Classification
Ornithopoda · Hadrosauridae
Described
1892, Othniel Charles Marsh

Overview

Edmontosaurus annectens lived in western North America in the late Maastrichtian, alongside Tyrannosaurus and Triceratops. Othniel Charles Marsh named it Claosaurus annectens in 1892 from a skeleton from the Lance Formation of Wyoming (USNM 2414). The genus Edmontosaurus had been named by Lawrence Lambe in 1917 for the older species E. regalis from Alberta.

It was a big, flat-headed hadrosaur that walked on four or two legs and chewed plants with batteries of hundreds of teeth. Several naturally mummified specimens, the first found by the Sternberg family in 1908, preserve large areas of scaly skin. Campione and Evans (2011) showed that the giant "Anatotitan" was just a large E. annectens, leaving two species in the genus.

A Tyrannosaurus tooth embedded in two fused, healed tail vertebrae of a hadrosaur like Edmontosaurus shows that T. rex attacked living animals and that this one escaped (DePalma et al. 2013).

Name meaning

"Edmonton lizard", after the Edmonton Formation of Alberta where the type species was found (Lambe 1917); annectens, Latin for "connecting" (Marsh 1892).

Biology & evidence

What scientists think about how this animal lived, and how strong the evidence for each idea is.

Skin & covering

  • Edmontosaurus had scaly skin.

    Evidence level: Direct evidence

    Several mummified specimens preserve large areas of skin with small, pebbly scales.

    Evidence for / against · 1
    Evidence for

    • Skin impression · Edmontosaurus mummies

      Naturally mummified skeletons with large areas of scaly skin, including AMNH 5060 (found in 1908 by the Sternbergs) and "Dakota" (NDGS 2000).

Growth

  • The giant "Anatotitan" was a fully grown Edmontosaurus annectens.

    Evidence level: Strong evidence

    Its long, flat skull falls on the growth trajectory of E. annectens, so the differences reflect size and age, not a separate species.

    Evidence for / against · 1
    Evidence for

    • Comparative anatomy · Morphometrics of edmontosaur skulls

      Morphometric analysis of almost all complete edmontosaur skulls finds only two species; Anatotitan copei and other names fall within the growth series of E. annectens.

Behavior

  • Tyrannosaurus attacked living Edmontosaurus.

    Evidence level: Moderate evidence

    A T. rex tooth is embedded in a hadrosaur tail that healed afterwards, so the animal was alive and escaped. The vertebrae are compared with, not firmly identified as, Edmontosaurus annectens.

    Evidence for / against · 1
    Evidence for

    • Specimen · Healed hadrosaur tail with embedded T. rex tooth

      Two fused hadrosaur tail vertebrae (compared with E. annectens) from the Hell Creek Formation of South Dakota, enclosing a Tyrannosaurus tooth crown surrounded by healed bone.

The mummified Edmontosaurus annectens specimen with preserved skin impressions, as figured by Osborn (1912).Image credit: Henry Fairfield Osborn, Public domain, via Wikimedia CommonsPublic domainSource (opens in a new tab)

Size

Length
12–15 m

(49.2 ft)

Height
3 mpublished range 2.6–3.4 m

(9.8 ft)

Based on large adults

Mass
5,600–15,900 kg
Edmontosaurus annectens was about 15 m (49.2 ft) long, roughly 8.3 times the height of a 1.8 m adult human.

Timeline

Lived from about 72.1 to 66 million years ago (Ma), within the Mesozoic era (252–66 Ma).

Periods: Maastrichtian (72.1–66 Ma), Late Cretaceous (100.5–66 Ma)

Maastrichtian bounds in PBDB; Campione & Evans place E. annectens in the late Maastrichtian and E. regalis in the late Campanian.

Location

Formations

Map data: Natural Earth (public domain). Modern positions, not where the continents were then.

These are the places where fossils have been found, not the full area where the animal lived.

Ecosystem

Hell Creek Formation scene with Dakotaraptor, Edmontosaurus, Pachycephalosaurus and Tyrannosaurus.Image credit: ABelov2014, CC BY 3.0, via Wikimedia CommonsCC BY 3.0Source (opens in a new tab)

Lived in: Hell Creek

68–66 million years ago · floodplain, river system, forest, coastal plain

Warm, humid coastal lowlands and river floodplains west of the retreating Western Interior Seaway at the very end of the Cretaceous, with forests of conifers and flowering plants. The ecosystem ends at the Cretaceous-Paleogene extinction.

Same ecosystem

Tyrannosaurus rex

Cretaceous· MaastrichtianCarnivore

Same ecosystem

Triceratops horridus

Cretaceous· MaastrichtianHerbivore

Same ecosystem

Ankylosaurus magniventris

Cretaceous· MaastrichtianHerbivore

Same ecosystem

Pachycephalosaurus wyomingensis

Cretaceous· MaastrichtianHerbivore

Classification

  1. cladeDinosauria
  2. cladeOrnithischia
  3. cladeOrnithopoda
  4. familyHadrosauridae
  5. subfamilySaurolophinae
  6. genusEdmontosaurus
  7. speciesEdmontosaurus annectens

Taxonomic status: Valid

Fossil record

Mounted casts of Edmontosaurus at the Museum of Ancient Life, Utah.Image credit: Etemenanki3, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing), Museum of Ancient Life, UtahCC BY-SA 4.0 (unmodified)Source (opens in a new tab)
Specimens
Catalog numberStatusInstitutionFound
USNM 2414HolotypeNational Museum of Natural History, Smithsonian Institution (USNM)—
YPM 2182ParatypeYale Peabody Museum (YPM)—

What has been found

Holotype: USNM 2414

  • Preserved
  • Partial
  • Reconstructed
  • Unknown / not recorded

Holotype: USNM 2414

Region by region (table)
Skeleton regions of Holotype: USNM 2414
RegionState
SkullPartial · Skull roof.
MandibleUnknown / not recorded
TeethUnknown / not recorded
Cervical vertebraeUnknown / not recorded
Dorsal vertebraeUnknown / not recorded
SacrumUnknown / not recorded
Caudal vertebraeUnknown / not recorded
RibsUnknown / not recorded
GastraliaUnknown / not recorded
Scapula / shoulder girdleUnknown / not recorded
HumerusUnknown / not recorded
Forearm (radius / ulna)Unknown / not recorded
Hand (manus)Unknown / not recorded
PelvisUnknown / not recorded
FemurUnknown / not recorded
Tibia / fibulaUnknown / not recorded
Foot (pes)Unknown / not recorded

Paratype: YPM 2182

Region by region (table)
Skeleton regions of Paratype: YPM 2182
RegionState
SkullPreserved
MandibleUnknown / not recorded
TeethUnknown / not recorded
Cervical vertebraeUnknown / not recorded
Dorsal vertebraeUnknown / not recorded
SacrumUnknown / not recorded
Caudal vertebraeUnknown / not recorded
RibsUnknown / not recorded
GastraliaUnknown / not recorded
Scapula / shoulder girdleUnknown / not recorded
HumerusUnknown / not recorded
Forearm (radius / ulna)Unknown / not recorded
Hand (manus)Unknown / not recorded
PelvisUnknown / not recorded
FemurUnknown / not recorded
Tibia / fibulaUnknown / not recorded
Foot (pes)Unknown / not recorded
Multiview skeletal reconstruction of Edmontosaurus annectens, scaled as MOR 1142 'X-Rex', with a human for scale.Image credit: Gunnar Bivens, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing)CC BY-SA 4.0 (unmodified)Source (opens in a new tab)

Gallery

Historical reconstruction: Charles R. Knight's early 20th-century painting of hadrosaurs (then 'Trachodon') by a lake, with upright kangaroo-like posture now considered outdated.Image credit: Charles R. Knight, Public domain, via Wikimedia CommonsPublic domain

All specimens

Discovery

Year described
1892
Described by
Othniel Charles Marsh
Type specimen
USNM 2414

Discovery timeline

  1. 1892 · Formally described

    Marsh names Claosaurus annectens

    Marsh names a hadrosaur from the Lance Formation of Wyoming.

    People: Othniel Charles Marsh

  2. 1908 · Specimen recovered

    The Sternbergs find the first Edmontosaurus mummy

    A mummified skeleton with skin impressions (AMNH 5060) is found in the Lance Formation of Wyoming.

  3. 1917 · Formally described

    Lambe names Edmontosaurus

    The genus is named for E. regalis from the Edmonton (now Horseshoe Canyon) Formation of Alberta.

    People: Lawrence M. Lambe

  4. 2011 · Revision

    Edmontosaur species reduced to two

    Campione and Evans show that edmontosaurs include only E. regalis and E. annectens.

    People: Nicolás E. Campione

  5. 2013 · Major study

    Healed T. rex bite found in a hadrosaur tail

    DePalma and colleagues report a tooth embedded in healed vertebrae.

Sources

  1. (2026). Paleobiology Database: Edmontosaurus occurrences. The Paleobiology Database (paleobiodb.org), data service 1.2, accessed 2026-09-23. https://paleobiodb.org/data1.2/occs/list.txt?base_name=Edmontosaurus&show=coords,paleoloc,strat,loc,ref&pgm=gplates (opens in a new tab)
  2. (2026). Wikipedia: Edmontosaurus. Wikipedia (English), accessed 2026-09-23. https://en.wikipedia.org/wiki/Edmontosaurus (opens in a new tab)
  3. 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: e25186. doi:10.1371/journal.pone.0025186 (opens in a new tab)
  4. Cohen, K. M., Harper, D. A. T., Gibbard, P. L. & Car, N. (2023). International Chronostratigraphic Chart (v2023/09). International Commission on Stratigraphy. https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf (opens in a new tab)
  5. DePalma, R. A., Burnham, D. A., Martin, L. D., Rothschild, B. M. & Larson, P. L. (2013). Physical evidence of predatory behavior in Tyrannosaurus rex. Proceedings of the National Academy of Sciences 110. doi:10.1073/pnas.1216534110 (opens in a new tab)
  6. 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.
  7. Marsh, O. C. (1892). Notice of new reptiles from the Laramie Formation. American Journal of Science 43: 449-453.
  8. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.