Lance Formation

The Lance (Creek) Formation is a division of Late Cretaceous (dating to about 69 - 66 Ma) rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas. The Lance Formation is Late Maastrichtian in age (Lancian land mammal age), and shares much fauna with the Hell Creek Formation of Montana and North Dakota, the Frenchman Formation of southwest Saskatchewan, and the lower part of the Scollard Formation of Alberta.

The Lance Formation occurs above the Baculites clinolobatus ammonite marine zone in Wyoming, the top of which has been dated to about 69 million years ago, and extends to the K-Pg boundary, 66 million years ago. However, the characteristic land vertebrate fauna of the Lancian age (which take its name from this formation) is only found in the upper strata of the Lance, roughly corresponding to the thinner equivalent formations such as the Hell Creek Formation, the base of which has been estimated at 66.8 million years old.[1]

Lance Formation
Stratigraphic range: Maastrichtian
~69–66 Ma
Lance Fm
Badlands in the Lance Formation along Cow Creek near the type locality. Niobrara County, Wyoming
UnderliesFort Union Formation
OverliesMeeteetse Formation
Thicknessup to 600 metres (1,970 ft)
PrimarySandstone, siltstone, shale
CountryUnited States
Type section
Named forLance Creek, Wyoming


The formation is described by W.G. Pierce as thick-bedded, buff-colored sandstone, and drab to green shale. It is Upper Cretaceous in age.[2]

The formation varies in thickness from about 90 m (300 ft.) in North Dakota, to almost 600 m (2,000 ft.) in parts of Wyoming.

Depositional environment

The Lance Formation was laid down by streams, on a coastal plain along the edge of the Western Interior Seaway. The climate was subtropical; there was no cold season and probably ample precipitation.


At least tens of thousands of Late Cretaceous vertebrate remains have been recovered from the Lance Formation. Fossils ranging from microscopic elements to extensive bonebeds, with nearly complete, sometimes articulated dinosaur skeletons, have been found.[3] Most other animals known from the formation are freshwater animals, and some are exclusively freshwater forms (for instance, frogs and salamanders). However, marine fossils are also found in the formation, suggesting that the sea was nearby. The bird fauna is mainly composed of orders still existing today.


UCMP 143274 (Caenagnathidae?)[4][5]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.


Birds reported from the Lance Formation
Genus Species Location Stratigraphic Position Material Notes Images


A. retusus

Reclassified as Palintropus retusus


C. major

A possible charadriiform bird


C. petra

Reclassified as Lamarqueavis minima[7]

C. rara

  • YPM 1805 (holotype), a partial coracoid[6]

A charadriiform

C. retusa

Reclassified as Palintropus retusus

C. minima

Reclassified as Lamarqueavis minima[7]


"C." maxima

  • UCMP 53973 (holotype), a partial coracoid[6]

A charadriiform bird, not necessarily closely related to Cimolopteryx.[6]


G. augustus

  • AMNH 25223, a partial humerus[8]

A possible charadriiform[8]


L. minima

  • UCMP 53976 (holotype), a partial coracoid[7]

A charadriiform.[7]

L. petra

  • AMNH 21911 (holotype), a partial coracoid[7]

A charadriiform.[7]


L. estesi

  • UCMP 53954 (holotype), a partial tarsometatarsus[8]

A possible procellariiform[8]


"L." pterygius

  • UCMP 53961 (holotype), a partial carpometacarpus[8]

A possible charadriiform.[8]


"P." vetus

  • ANSP 13361 (holotype), a partial tibiotarsus[8]
  • AMNH 25221, a partial tibiotarsus[8]

A bird similar to gruids, idiornithids and presbyornithids.[8]


P. retusus

  • YPM 513 (holotype), a partial coracoid[9]

A basal ornithuromorph belonging to Ambiortiformes.[9]


P. skutchi

  • UCMP 73103 (holotype), a quadrate[10]
  • tarsometatarsus?[10][11]

A hesperornithiform possibly also present in the Hell Creek Formation.[10]


T. clemensi

  • UCMP 53958, a partial humerus[12]

A possible presbyornithid.[12]

Unnamed presbyornithid


  • AMNH 21929, a partial scapula[8]
  • AMNH 22603, a partial scapula[8]
  • YPM 868, a partial scapula[8]
  • AMNH 22602, a partial sternum[8]

A presbyornithid[8]

Unnamed enantiornithean


  • USNM 2909, a partial metatarsal and pedal phalanges[13]

An enantiornithean, previously referred to "Ornithomimus" minutus[13]

Unnamed avian


  • UCMP 53960, two partial neck vertebrae[8]

An indeterminate avian[8]

Unnamed phalacrocoracid


  • AMNH 25272, a femur[8]

A possible phalacrocoracid.[8]

"Unnamed ornithurine A"[6]


  • UCMP 53962, a partial coracoid[6]
  • UCMP 53963, a partial coracoid[6]
  • AMNH uncatalogued, a partial coracoid[6]

Originally thought to belong to Cimolopteryx rara, but probably a new species. Also present in the Frenchman Formation.[6]

"Unnamed ornithurine C"[6]


  • YPM PU 17020, a partial coracoid[6]

Also present in the Hell Creek Formation.[6]

"Unnamed ornithurine E"[6]


  • USNM 181923, a partial coracoid[6]
  • USNM 13011, a partial coracoid[6]

Also present in the Hell Creek Formation.[6]

"Unnamed ornithurine F"[6]


  • UCMP 53957, a partial coracoid[6]
  • ACM 12359, a partial coracoid[6]

Originally thought to belong to "Cimolopteryx" maxima, but probably a new species.[6]

Other coelurosaurs

"Ornithomimus" sp. by Tom Parker
Pectinodon bakkeri tooth





Other vertebrates

Other land vertebrates include pterosaurs (e.g. cf. Azhdarcho), crocodiles, champsosaurs, lizards, snakes, turtles, frogs and salamanders.

Remains of fishes and mammals have also been found in the Lance Formation.

See also


  1. ^ Lehman, T. M., Mcdowell, F. W., & Connelly, J. N. (2006). First isotopic (U-Pb) age for the Late Cretaceous Alamosaurus vertebrate fauna of West Texas, and its significance as a link between two faunal provinces. Journal of Vertebrate Paleontology, 26(4), 922-928.
  2. ^ Pierce, W.G., 1997, Geologic map of the Cody 1 degree x 2 degrees quadrangle, northwestern Wyoming: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-2500, scale 1:250000.
  3. ^ Silver, Mark (August 2, 2014) "The Dinosaur Surveyors" The American Surveyor Frederick Maryland
  4. ^ Stidham, 1998
  5. ^ Dyke, GJ; Mayr, G. (1999). "Did parrots exist in the Cretaceous period?". Nature 399 (6734): 317–318. doi:10.1038/20583.
  6. ^ a b c d e f g h i j k l m n o p q r s t Nicholas R. Longrich (2011). "Titanoceratops ouranous, a giant horned dinosaur from the Late Campanian of New Mexico". Cretaceous Research. 32 (3): 264–276. doi:10.1016/j.cretres.2010.12.007.
  7. ^ a b c d e f Federico L. Agnolin (2010). "An avian coracoid from the Upper Cretaceous of Patagonia, Argentina". Stvdia Geologica Salmanticensia. 46 (2): 99–119.
  8. ^ a b c d e f g h i j k l m n o p q r Hope, 2002
  9. ^ a b Longrich, N. 2009. An ornithurine-dominated avifauna from the Belly River Group (Campanian, Upper Cretaceous) of Alberta, Canada. Cretaceous Research, 30(1): 161-177.
  10. ^ a b c Elzanowski, Paul and Stidham, 2001. An avian quadrate from the Late Cretaceous Lance Formation of Wyoming. Journal of Vertebrate Paleontology, 20(4): 712-719.
  11. ^ "Table 11.1," in Weishampel, et al. (2004). Page 215.
  12. ^ a b Olson, S.L. and Feduccia, A. 1980. Presbyornis and the origin of the Anseriformes (Aves: Charadriomorphae). Smithsonian Contributions to Paleobiology no. 323.
  13. ^ a b Chiappe, L. M., and Walker, C. A. (2002) Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes): In: Mesozoic Birds, above the heads of Dinosaurs, University of California Press, 240-267.
  14. ^ "Table 6.1," in Weishampel, et al. (2004). Page 139.
  15. ^ The Dinosauria 2nd Edition (David B. Weishampel, Halszka Osmólska and Peter Dodson), p. 584, Dinosaur Distribution (DAVID B. WEISHAMPEL, PAUL M. BARRETT, RODOLFO A. CORIA, JEAN LE LOEUFF, XU XING, ZHAO XIJIN, ASHOK SAHNI, ELIZABETH M. P. GOMANI, CHRISTOPHER R. NOTO)
  16. ^ Bakker, R.T. (1988). Review of the Late Cretaceous nodosauroid Dinosauria: Denversaurus schlessmani, a new armor-plated dinosaur from the Latest Cretaceous of South Dakota, the last survivor of the nodosaurians, with comments on Stegosaur-Nodosaur relationships. Hunteria 1(3):1-23.(1988).
  17. ^ The Dinosauria 2nd Edition (David B. Weishampel, Halszka Osmólska and Peter Dodson), p. 585, Dinosaur Distribution (DAVID B. WEISHAMPEL, PAUL M. BARRETT, RODOLFO A. CORIA, JEAN LE LOEUFF, XU XING, ZHAO XIJIN, ASHOK SAHNI, ELIZABETH M. P. GOMANI, CHRISTOPHER R. NOTO)
  18. ^ The Dinosauria 2nd Edition (David B. Weishampel, Halszka Osmólska and Peter Dodson), p. 585, Dinosaur Distribution (DAVID B. WEISHAMPEL, PAUL M. BARRETT, RODOLFO A. CORIA, JEAN LE LOEUFF, XU XING, ZHAO XIJIN, ASHOK SAHNI, ELIZABETH M. P. GOMANI, CHRISTOPHER R. NOTO)
  19. ^ "Table 17.1," in Weishampel, et al. (2004). Page 368.
  20. ^ a b c d "Table 23.1," in Weishampel, et al. (2004). Page 496.
  21. ^ a b Scannella, J. and Horner, J.R. (2010). "Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny." Journal of Vertebrate Paleontology, 30(4): 1157 - 1168. doi:10.1080/02724634.2010.483632
  22. ^ "Table 17.1," in Weishampel, et al. (2004). Page 368.
  23. ^ Horner J.R. and Goodwin, M.B. (2009). "Extreme cranial ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus." PLoS ONE, 4(10): e7626. Online full text
  24. ^ Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology. 29 (3): 758–770. doi:10.1671/039.029.0328.

External links

1963 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1963.


Cimolopteryx (meaning "Cretaceous wing") is a prehistoric bird genus from the late Cretaceous Period. It is currently thought to contain only a single species, Cimolopteryx rara. The only known specimen confidently attributed to C. rara was found in the Lance Formation of Wyoming, dating to the end of the Maastrichtian age, about 66 million years ago. A second dubious species, "Cimolopteryx" maxima, has been described from both the Lance Formation, and the Hell Creek Formation of Montana.


Clemensodon is a genus of extinct mammal from the Upper Cretaceous of North America. It lived during the end of the Mesozoic, also known as the "age of the dinosaurs". It was a member of the extinct order of Multituberculata within the suborder of Cimolodonta and family Eucosmodontidae. Fossil remains are restricted to teeth.

The main species of Clemensodon is Clemensodon megaloba, however, this species is also known as a part of Kimbetohia campi. Fossils have been found in the Lance Formation of Wyoming (United States). They age from the Maastrichtian division of the Upper Cretaceous. The species is based on a reassesment of a couple of Kimbetohia teeth, but not the entire species or genus. The assignment of this taxon to Eucosmodontidae is tentative.

Evidence from the size and number of serrations of certain teeth and its enamel microstructure indicates that Clemensodon is either a derived taeniolabdoid or a primitive ptilodontoid. Determination of which of these two alternatives is correct must await the recovery of teeth from other positions.


Dyslocosaurus (meaning "hard-to-place lizard") is the name given in 1992 to a genus of sauropod dinosaur from the Late Jurassic Period of Wyoming, North America.

The holotype or type specimen the genus is based on, AC 663, is part of the collection of the Amherst College Museum of Natural History. It was collected by professor Frederic Brewster Loomis. However, the only available information regarding its provenance is that given on the label: "Lance Creek", a county in east Wyoming. Loomis himself thought that it stemmed from the Lance Formation, dating from the Late Cretaceous Maastrichtian.

In 1963 the specimen was brought to the attention of John Stanton McIntosh, who in 1992, together with William Coombs and Dale Russell, decided to create a new genus and species for it. The type species is Dyslocosaurus polyonychius. The genus name is derived from Greek dys, "bad, "poor", and Latin locus, "place", a reference to the paucity of data regarding the type locality of the fossil. The specific name is derived from Greek polys, "many", and onyx, "claw". The describers interpreted the remains, consisting of some limb bones, as those of a diplodocid dinosaur. From this they concluded that it in fact dated from the Late Jurassic Period, like most diplodocids. The species would then be unique in having four, or perhaps five, claws on the foot, whereas other diplodocids have only three — hence the specific name. A species similar to Dyslocosaurus would have made the tracks of the ichnospecies Brontopodus birdi from the Early Cretaceous, that also features four claws.

In 1998 Paul Sereno and Jeffrey A. Wilson gave an alternative interpretation: the specimen would come from the Lance Formation after all but be a chimera: in this case a mix up of titanosaur limb bones and theropod phalanges.

In their taxonomic revision of Diplodocidae, Tschopp et alii in 2015 noted that a pedal phalanx included in AC 663 is apparently not from the same individual as the rest of AC 663 given differences in preservation and coloration among individual bones, raising doubts on whether Dyslocosaurus had more than three claws on the feet. Although fragmentary, Dyslocosaurus was recovered as a member of Dicraeosauridae, potentially making it the second record of a dicraeosaurid from North America (the other being Suuwassea).

Edmontosaurus annectens

Edmontosaurus annectens (meaning "connected lizard from Edmonton) is a species of flat-headed or saurolophine hadrosaurid ornithopod dinosaur (a "duck-billed dinosaur") from the very end of the Cretaceous Period, in what is now North America. Remains of E. annectens have been preserved in the Frenchman, Hell Creek, and Lance Formations. All of these formations are dated to the late Maastrichtian stage of the Late Cretaceous Period, representing the last three million years before the extinction of the dinosaurs (between 68 and 66 million years ago). Also, E. annectens is also from the Laramie Formation, and magnetostratigraphy suggests an age of 69-68 Ma for the Laramie Formation. Edmontosaurus annectens is known from numerous specimens, including at least twenty partial to complete skulls, discovered in the U.S. states of Montana, South Dakota, North Dakota, Wyoming and Colorado and the Canadian province of Saskatchewan. It was a large animal, up to approximately 12 metres (39 ft), potentially up to 15 m (49 ft) in length, with an extremely long and low skull. E. annectens exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs. It has a long taxonomic history, and specimens have at times been classified in the genera Diclonius, Trachodon, Hadrosaurus, Claosaurus, Thespesius, Anatosaurus and Anatotitan, before being grouped together in Edmontosaurus.

Lances fournies

The lance fournie (French: "equipped lance") was a medieval equivalent to the modern army squad that would have accompanied and supported a man-at-arms (a heavily armoured horseman popularly known as a "knight") in battle. These units formed companies under a captain either as mercenary bands or in the retinue of wealthy nobles and royalty. Each lance was supposed to include a mixture of troop types (the men-at-arms themselves, lighter cavalry, infantry, and even noncombatant pages) that would have guaranteed a desirable balance between the various components of the company at large; however, it is often difficult to determine the exact composition of the lance in any given company as the available sources are few and often centuries apart.

A lance was usually led and raised by a knight in the service of his liege, yet it is not uncommon in certain periods to have a less privileged man, such as a serjeants-at-arms, lead a lance. More powerful knights, also known as a knight bannerets, could field multiple lances.


Nanocuris is an extinct genus of Deltatheridiidae from Cretaceous of Canada (Saskatchewan) and United States (Wyoming - Lance Formation). Initially was classified in a proper family, Nanocuridae, in clade Eutheria, but a reanalysis of a new specimen reveal a deltharoid affinity of the genus.


Nedoceratops (meaning "insufficient horned face") is a controversial genus of ceratopsid herbivorous dinosaur from the Late Cretaceous period Lance Formation of North America. It is known only from a single skull discovered in Wyoming. Its status is the subject of ongoing debate among paleontologists: some authors consider Nedoceratops a valid, distinct taxon, while others consider it to represent an ontogenetic (growth) stage of Triceratops and thus a synonym.


Obamadon is an extinct genus of polyglyphanodontian lizards from the Late Cretaceous of North America. Fossils have been found in the Hell Creek Formation of Montana and the Lance Formation of Wyoming. Researchers describe it as being distinguished by its "tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves." The type species was named Obamadon gracilis after United States president Barack Obama, "in reference to the tall, straight teeth, and the manner in which Mr. Obama has acted as a role model of good oral hygiene for the world." According to Nicholas R. Longrich of Yale University, the creature "was probably a foot long, [and] with these tall, slender teeth it used to eat insects and plant matter."The lizard was identified as part of a search of museum collections to find snake and lizard species that had lived immediately prior to the Cretaceous–Paleogene extinction event, in which the dinosaurs (with the exception of birds) died out. Its identification was published by Longrich, Bhullar and Gauthier in a paper titled "Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary", published on December 10, 2012 in Proceedings of the National Academy of Sciences. The scientists found that lizards and snakes had been more badly hit by the mass extinction than previously thought, with 83 percent of species – including Obamadon – dying out. All present-day species of lizards are descended from members of the surviving 17 percent.


Odaxosaurus is an extinct genus of anguid lizards that existed in western North America from the Late Cretaceous to the Paleocene. Fossils of the type species Odaxosaurus piger and the species O. priscus are widespread throughout Late Cretaceous formations in the western United States and Canada. First described in 1928 from the Lance Formation in Wyoming, O. piger has since been found in the Hell Creek Formation in Wyoming and Montana, the Frenchman and Scollard formations in Alberta, and the Aguja Formation in Texas. It was one of the few species of lizards to survive the Cretaceous–Paleogene extinction event, which is estimated to have killed off 83% of all lizard species. The second species, O. priscus, was named in 1996 from the Dinosaur Park Formation in Alberta and has since been found in the Kaiparowits Formation in southern Utah. Remains of an anguid from the Kirtland Formation in New Mexico may also belong to Odaxosaurus.


Pariguana (meaning "near Iguana" in Greek) is an extinct genus of iguanid lizard from the Late Cretaceous of western North America. It is known from a single type species, Pariguana lancensis, named in 2012 on the basis of a partial lower jaw from the Lance Formation in eastern Wyoming. This jaw bone comes from a layer dated approximately 650,000 years before the Cretaceous–Paleogene extinction event. Pariguana is the oldest definitive iguanid from North America, and may represent the first stage of the iguanian evolutionary radiation from Asia into North America.


Pectinodon is a genus of dinosaurs from the Late Cretaceous period (66 mya). It currently contains a single valid species, Pectinodon bakkeri (sometimes classified as Troodon bakkeri), known only from teeth.In 1982, Kenneth Carpenter named a number of theropod teeth from the late Maastrichtian Lance Formation of Wyoming as the type species Pectinodon bakkeri. The generic name is derived from Latin pecten, "comb", and Greek ὀδών, odon, "tooth", in reference to the comb-like serrations on the rear edge of the teeth. The specific name honours Robert Thomas Bakker.The holotype, UCM 38445, consists of a 6.2 mm long adult tooth. The paratypes are three juvenile teeth.In 1985 Lev Nesov named a second species, Pectinodon asiamericanus, based on specimen CCMGE 49/12176, a tooth from the Khodzhakul Formation of Uzbekistan dating from the Cenomanian. This is today often considered a nomen dubium.While historically considered synonymous with Troodon or more specifically the species Troodon formosus, Philip Currie and colleagues (1990) noted that the P. bakkeri fossils from the Hell Creek Formation and Lance Formation might belong to different species. In 1991, George Olshevsky assigned the Lance formation fossils to the species Troodon bakkeri. In 2011, Zanno and colleagues reviewed the convoluted history of troodontid classification in Late Cretaceous North America. They followed Longrich (2008) in treating Pectinodon bakkeri as a valid genus, and noted that it is likely the numerous Late Cretaceous specimens currently assigned to Troodon formosus almost certainly represent numerous new species, but that a more thorough review of the specimens is required.In 2013 Currie and Derek Larson concluded that Pectinodon bakkeri was valid and its teeth could be found both in the Lance Formation and the coeval Hell Creek Formation. Some teeth from the older Campanian Dinosaur Park Formation could not be statistically differentiated from them, likely due to an insufficiently large sample, and were referred to a cf. Pectinodon.


Potamornis is a prehistoric bird genus that dated back to the late Maastrichtian age of the late Cretaceous period. Its scrappy remains were found in the Lance Formation at Buck Creek, USA, and additional possible remains were found in the upper Hell Creek Formation of Montana, dated to the Danian age of the Paleogene period, though these may have been reworked. A single species was named and described in 2001: Potamornis skutchi.This was almost certainly a member of the Hesperornithes, the hefty and toothed flightless diving birds of the Mesozoic seas. Its precise relationships are not all too clear; the quadrate bone is unique in some respects but apparently shares more apomorphies with the family Hesperornithidae - the "typical" Hesperornithes - in cladistic analysis. Consequently, it might be considered a fossil hesperornithid with a different feeding specialization. Though it was heavily built like many (flying and flightless) diving birds, it weighed perhaps 1.5 or 2 kg. This raises the possibility that the Hesperornithes not only included flying members (see also Enaliornis), but that their families might have evolved flightlessness independently.


Prodesmodon is an extinct genus of prehistoric salamander first described from the Lance Formation.


Prodiplocynodon is an extinct genus of basal crocodyloid crocodylian. It is the only crocodyloid known from the Cretaceous and existed during the Maastrichtian stage. The only species of Prodiplocynodon is the type species P. langi from the Lance Formation of Wyoming, known only from a single holotype skull lacking the lower jaw.The skull was collected by the American Museum Expedition of 1892 from exposures near the Cheyenne River in Niobrara County. It was described by Charles C. Mook of the American Museum of Natural History in 1941. The generic name means "before Diplocynodon" because Mook saw close similarities between the holotype skull and that of the alligatoroid Diplocynodon from the Eocene of Europe.


Socognathus is a genus of prehistoric chamopsiid polyglyphanodontian lizards containing species that lived from the Middle Campanian stage to the late Maastrichtian. Several specimens of the type species, Socognathus unicuspis, have been found in Alberta, Canada. A second species, Socognathus brachyodon is known from the late Maastrichtian Lance Formation; its fossils have been found in Wyoming, United States.


Stygimoloch ("devil from hell," from Styx, Greek mythological underworld river, and moloch, Hebrew for an evil-connoted angel, such as the Angel of Death) is a genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 66 million years ago. Its taxonomical status is in dispute, as the failure to discover adult specimens strongly implies that collected holotypes merely represent juvenile pachycephalosaurs. This hypothesis has been supported by numerous modern studies, the most recent of which agrees that Stygimoloch is synonymous with Pachycephalosaurus. The genus was discovered in the Hell Creek Formation, Ferris Formation, and Lance Formation of the Western Interior (United States), where it lived alongside such genera as Tyrannosaurus, Triceratops, and Edmontosaurus.


Thescelosaurus ( THESS-il-ə-SOR-əs; ancient Greek θέσκελος-/theskelos- meaning "godlike", "marvelous", or "wondrous" and σαυρος/sauros "lizard") was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous–Paleogene extinction event around 66 million years ago. The preservation and completeness of many of its specimens indicate that it may have preferred to live near streams.

This bipedal ornithopod is known from several partial skeletons and skulls that indicate it grew to between 2.5 and 4.0 meters (8.2 to 13.1 ft) in length on average. It had sturdy hind limbs, small wide hands, and a head with an elongate pointed snout. The form of the teeth and jaws suggest a primarily herbivorous animal. This genus of dinosaur is regarded as a specialized basal ornithopod, traditionally described as a hypsilophodont, but more recently recognized as distinct from Hypsilophodon. Several species have been suggested for this genus. Three currently are recognized as valid: the type species T. neglectus, T. garbanii and T. assiniboiensis.

The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota, United States, was interpreted as including a fossilized heart. There was much discussion over whether the remains were of a heart. Many scientists now doubt the identification of the object and the implications of such an identification.


Thespesius (meaning "wondrous one") is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.


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