{{Short description|Dubious extinct genus of dinosaurs}} {{Use dmy dates|date=May 2026}} {{speciesbox | name = ''Trachodon'' | image = Trachodon mirabilis.jpg | image_caption = Illustration of some of Leidy's original ''Trachodon'' teeth, including the holotype (1-6) | fossil_range = Late Cretaceous, {{fossilrange|77}} | genus = Trachodon | parent_authority = Leidy, 1856 | species = mirabilis | authority = Leidy, 1856 }}
'''''Trachodon''''' (meaning "rough tooth") is a dubious genus of hadrosaurid dinosaur from the Upper Cretaceous of what is now Montana in the western United States. The only species is ''T. mirabilis'', though many others have been assigned to the genus. ''T. mirabilis'' was described by Joseph Leidy in 1856 based on a set of teeth; however, this was later shown to be a mixture of hadrosaurid and ceratopsian teeth. These fossils were unearthed in 1856 by Ferdinand Vandeveer Hayden during an expedition to the Missouri River in Montana, USA, in rock from the Judith River Formation. This formation dates to the Campanian stage of the Late Cretaceous, which lasted from 79 to 75.3 million years ago. One of the teeth, an incomplete hadrosaurid tooth, was later chosen as the holotype.
''Trachodon'' was the first hadrosaurid to be named. Several specimens, including complete skeletons of what is now considered ''Edmontosaurus annectens'', were mistakenly assigned to the genus or ''T. mirabilis''. Additionally, many species erected for ''Trachodon'', such as ''T. marginatus'', are now in their own genus or are ''nomen dubia'', like ''T. selwyni''. The taxon coexisted with other ornithischians, including hadrosaurids like ''Corythosaurus,'' ceratopsians like ''Lokiceratops'' and ''Medusaceratops'', and pachycephalosaurids like ''Hanssuesia.'' Carnivorous theropod dinosaurs have been unearthed as well, such as the tyrannosaurid ''Daspletosaurus'' and the troodontid ''Troodon''. Several other dubious dinosaur genera were named from the formation as well, such as ''Deinodon, Palaeoscincus,'' and possibly ''Troodon.'' During the Campanian, the Judith River Formation was a vast floodplain on along the western coast of the Western Interior Seaway and blanked by ferns, conifers, cycads, and angiosperms.
==History and classification== ===Discovery and early nomenclature=== [[File:Joseph_Leidy_by_Gilbert_Studios_c1870.jpg|thumb|left|Joseph Leidy, who named ''Trachodon''|347x347px]] In 1856, Joseph Leidy received fragmentary remains from the Judith River Formation, collected by Ferdinand Vandeveer Hayden. From these bones, he provided the first names for North American dinosaurs: ''Deinodon'', ''Palaeoscincus'', ''Trachodon'', and ''Troodon'' (then spelled ''Troödon''). The type species of ''Trachodon'' is ''T. mirabilis''. The generic name is derived from Greek τραχυς, ''trakhys'', "rough", and όδον, ''odon'', "tooth", referring to the granulate inner surface of one of the teeth. The specific name means "marvelous" in Latin. ''Trachodon'' was based on several unassociated teeth, of which the tooth ANSP 9260 has been taken as the holotype. Leidy believed the teeth to belong to a relative of ''Iguanodon'', and ''Trachodon'' would come to be recognized as the first known hadrosaur. However, only two of the teeth (including ANSP 9260), possessing a single root, are truly hadrosaurian. Others, with double roots, infact belonged to ceratopsians.<ref name="JL56">Leidy, J. (1856). "[https://www.biodiversitylibrary.org/item/18246#page/92/mode/1up Notice of remains of extinct reptiles and fishes, discovered by F. V. Hayden in the Bad Lands of the Judith River, Nebraska Territories.]" ''Proceedings of the Academy of Natural Science Philadelphia'', '''8'''(25 March): 72–73.</ref><ref name="BC07">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}}</ref><ref name=LW42>Lull, R.S., and Wright, N.E. (1942). Hadrosaurian Dinosaurs of North America. ''Geological Society of America Special Paper 40'':1–242.</ref>
Later in the same year, Leidy would name the genus and species ''Thespesius occidentalis'' based on hadrosaurid tail vertebrae and a {{dinogloss|phalanx}} from the Lance Formation of South Dakota, and in 1859 he named ''Hadrosaurus foulkii'' based on a partial skeleton from the Woodbury Formation of New Jersey.<ref name=BC07/><ref name=LW42/> By 1860, however, he began to question the relationship between these remains. He published on these concerns in 1865, speculating that ''Trachodon'' and ''Thespesius'' may represent the same animal, with the distinct tail vertebrae of ''Hadrosaurus'' maintaining its distinctiveness.<ref name=BC07/><ref>Leidy, J. (1865). Memoirs of the extinct reptiles of the Cretaceous formations of the United States. Smithsonian Contributions to Knowledge14: 1–135.</ref>
Leidy's further statements, which were often contradictory, would go on to confuse later palaeontologists. By a short 1868 publication he had come to regret the name ''Trachodon'', feeling that ''Hadrosaurus'' (meaning "bulky lizard") was a more appropriate name. Furthermore, he had by now become aware the single and double rooted teeth of ''Trachodon'' belonged to different animals, suggesting that ''Trachodon'' could come to refer to the double rooted (ceratopsian) teeth, with ''Hadrosaurus'' referring to the single rooted (hadrosaur) ones and inheritingt he anem ''Hadrosaurus mirabilis''. Whether he intended this to be a formal taxonomic action was, however, unclear. In 1870 he made another short publication, noting tooth characteristics that may indicate ''Hadrosaurus mirabilis'' (the single rooted "''Trachodon''" teeth) was a distinct genus from ''Hadrosaurus foulkii''; seemingly, he did not believe ''Trachodon'' an appropriate name for the former. As in 1860, he wondered if ''Thespesius'' represented the same animal as the original ''Trachodon'' teeth. However, he noted that differing vertebral characteristics demonstrated ''Thespesius'' was distinct from both ''Hadrosaurus'' and ''Trachodon'', in spite of the latter not being associated with any vertebrae.<ref name=BC07/><ref name=JL68>Leidy, J. (1868). Remarks on a jaw fragment of ''Megalosaurus''. ''Proceedings of the Academy of Natural Science Philadelphia'' 20:197–200.</ref><ref>Leidy, J. (1870). Remarks on fossil vertebrates. Proceedings of the Academy of Natural Science Philadelphia 22: 66–68.</ref> [[File:Strange_Creatures_of_the_Past_-_The_Spoonbill_Dinosaur.png|thumb|Restoration of "''Hadrosaurus mirabilis''" by Charles R. Knight, based on Cope's 1882 skeleton, published in an 1897 article]] In the wake of Leidy's work, Edward Drinker Cope published much of the following work on early hadrosaurs.<ref name=BC07/> In an 1869 paper he assigned all of Leidy's species to the genus ''Hadrosaurus'', including ''H. mirabilis'', and named the family Hadrosauridae to include ''Hadrosaurus'', its later synonym ''Ornithotarsus'', and ''Hypsibema''.<ref name=BC07/><ref>Cope, E.D. (1869c). Synopsis of the extinct Batrachia, Reptilia, and Aves of North America. Transactions of the American Philosophical Society 14: 1–252</ref> In 1876 he named the genus ''Diclonius'', with three species, each based also on teeth.<ref name=BC07/><ref name="cope1876">{{cite journal|last=Cope|first=E.D.|author-link=Edward Drinker Cope|year=1876|title=Descriptions of some vertebrate remains from the Fort Union Beds of Montana|journal=Proceedings of the Academy of Natural Sciences of Philadelphia|volume=28|pages=248–261}}</ref> The following year, he split Leidy's original sample of ''Trachodon'' teeth between the species ''Trachodon mirabilis'', ''Diclonius perangulatus'', and ''Dysganus haydenianus''.<ref name=BC07/><ref>Cope, E.D. (1877). Report on the geology of the region of the Judith River, Montana, and on vertebrate fossils obtained on or near the Missouri River. U.S. Geological and Geographical Survey of the Territories Bulletin 3: 572–573.</ref> In 1882 fossil collectors R. S. Hill and J. L. Wortman, working for Cope, collected the first complete skeleton of a hadrosaur. Cope would produce a preliminary publication on the specimen in 1883, and assigned it to the species ''mirabilis''. However, viewing Leidy as having abandoned the genus ''Trachodon'', Cope used his own genus name ''Diclonius'', producing the binomial ''Diclonius mirabilis'' for the species.<ref name=BC07/><ref name=LW42/><ref name="cope1883">{{cite journal|last=Cope|first=E.D.|author-link=Edward Drinker Cope|year=1883|title=On the characters of the skull in the Hadrosauridae|journal=Proceedings of the Academy of Natural Sciences of Philadelphia|volume=35|pages=97–107}}</ref> Why Cope believed the skeleton belonged to the same species as Leidy's original hadrosaur teeth, and why he allied it to ''Diclonius'' instead of creating a new genus, was not entirely clear and subject to speculations of later authors.<ref name=BC07/> In 1888, Richard Lydekker named the species ''Trachodon cantabridgiensis'' based on a tooth from the Cambridge Greensand of England, recognizing it alongside ''T. mirabilis'' in a distinct ''Trachodon'' of which ''Hadrosaurus'' was a synonym. Consequently, he established the name Trachodontidae as a replacement for Hadrosauridae.<ref name="RL88">Lydekker, R. (1888). Note on a new Wealden iguanodont and other dinosaurs. ''Quarterly Journal of the Geological Society of London'' 44:46–61.</ref><ref>Lambe, L. (1918). On the genus Trachodon of Leidy. Ottawa Naturalist 31:135–139.</ref>
===Wide acceptance of ''Trachodon''=== [[File:AMNH Trachodon 1916.jpg|left|thumb|Skeletons displayed as ''Trachodon mirabilis'' at the American Museum of Natural History in 1916]] Around the turn of the century, the nomenclature of hadrosaurs including the species ''mirabilis'' would remain inconsistent.<ref name=BC07/> A 1897 article by journalist William Ballou would use the name ''Hadrosaurus mirabilis'', possibly influenced by curator of the American Museum of Natural History (AMNH), Henry Fairfield Osborn.<ref name=BC07/><ref>Ballou, W. H. 1897. Strange creatures of the past: Gigantic saurians of the reptilian age. Century Magazine (November): 15–23.</ref> Promotion and correspondence by the AMNH would variously use the names ''Hadrosaurus'', ''Diclonius'', and ''Claosaurus'' to contain the species and refer to Cope's skeleton and others being excavated in the American West.<ref name=BC07/> Othniel Charles Marsh, Cope's rival, had endorsed ''Trachodon'' as the senior synonym of ''Hadrosaurus'' and also ''Diclonius''.<ref name=BC07/><ref name="marsh1896">{{cite book |last=Marsh |first=Othniel Charles |author-link=Othniel Charles Marsh |year=1896 |chapter=The dinosaurs of North America |publisher=U.S. Geological Survey |location=Washington, D.C. |title=Sixteenth Annual report of the United States Geological Survey to the Secretary of the Interior, 1894–1895: Part 1 |url=https://www.biodiversitylibrary.org/item/123252#page/168/mode/1up|page=Explanation of Plate XIII}}</ref> This position was shared by Oliver Perry Hay in a 1902 paper.<ref name=BC07/> Both, however, recognized several other hadrosaur genera distinct from ''Trachodon''.<ref name=BC07/><ref name="hay1902">{{cite journal|last=Hay|first=O.P.|author-link=Oliver Perry Hay|year=1902|title= Bibliography and catalogue of the fossil Vertebrata of North America|journal=United States Geological Survey Bulletin|volume=179|pages=1–868}}</ref>
In 1902, John Bell Hatcher would publish a review all members of Trachodontidae (which he used over the term Hadrosauridae), concluding that of ten established genera, only ''Trachodon'' and Marsh's ''Claosaurus'' were valid. All others (''Thespesius'', ''Hadrosaurus'', ''Ornithotarsus'', ''Cionodon'', ''Polyonax'', ''Diclonius'', ''Pteropelyx'', and ''Claorhynchus'') were considered to be synonyms of ''Trachodon''. How many species were synonymous within the lumped ''Trachodon'' was a matter he, however, considered uncertain.<ref name=BC07/><ref name=JBH02>Hatcher, J.B. (1902). The genus and species of the Trachodontidae (Hadrosauridae, Claosauridae) Marsh. ''Annals of the Carnegie Museum'' 14(1):377–386.</ref> Some of these, such as ''Claorhynchus'' and ''Polyonax'', would later turn out to represent ceratopsians.<ref name=BC07/> Part of Hatcher's reasoning for lumping these taxa was that he saw the Judith horizon of ''Trachodon'' and the Lancian horizon of ''Thespesius'' as being deposited at the same time, whereas ''Claosaurus'' was from earlier strata.<ref name=JBH02/> Special attention was given to ''Claosaurus annectens'', a second species of ''Claosaurus'' named by Marsh in 1892 based on a nearly complete skeleton from Lancian rocks in Wyoming.<ref name=BC07/><ref name=JBH02/> Due to its differing geologic age, he considered it unlikely it belonged to the genus ''Claosaurus'', and he saw no anatomical grounds for recognizing it as a distinct genus from ''Trachodon''. Thus, he reassigned it as ''Trachodon annectens'', a second species only slightly different from ''T. mirabilis''.<ref name=JBH02/>
Canadian palaeontologist Lawrence Lambe named three new species of ''Trachodon'' from the Belly River Group in 1902. He considered ''Pteropelyx'' a subgenus of ''Trachodon'', and referred each new species to ''Trachodon'' (''Pteropelyx''). ''T. selwyni'', named after Alfred Selwyn was based on a jawbone and distinguished on teeth characteristics, and Lambe supposed an isolated jawbone and femur also belonged to the species. ''T. marginatus'' was based on a partial skeleton, with the left forelimb being best represented.<ref name=BC07/><ref name=LW42/><ref name=lambe1902>{{cite journal|last=Lambe|first=L.M.|author-link=Lawrence Lambe|year=1902|title=New genera and species from the Belly River Series (Mid-Cretaceous)|journal=Geological Survey of Canada. Contributions to Canadian Palaeontology. Part II. On Vertebrata of the Mid-Cretaceous of the North West Territory|volume=3|issue=2|pages=25–81}}</ref> Lambe would later give it the distinct genus ''Stephanosaurus''.<ref name=BC07/><ref name=LW42/><ref name=LL14>{{cite journal |last=Lambe |first=Lawrence M. |year=1914 |title=On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of ''Stephanosaurus marginatus'' from the same horizon |journal=Ottawa Naturalist |volume=28 |pages=13–20 }}</ref> ''T. altidens'', for which Lambe provisionally suggested the distinct genus ''Didanodon'', was based on a jawbone.<ref name=BC07/><ref name=LW42/> Each would eventually go on to be considered dubious.<ref name=BC07/><ref name=LW42/><ref name=lambe1902/> [[File:Pasta_-_mummified_trachodon_-_AmMusNatHist.jpg|thumb|"''Trachodon'' mummy" discoered in 1908]] The American Museum of Natural History had acquired Cope's fossil collection in 1899, including his "''Diclonius mirabilis''" skeleton, giving it the specimen number AMNH 5730.<ref name=BC07/> In 1904, Oscar Hunter had found another hadrosaur skeleton; the museum purchased it in 1906 and Barnum Brown excavated it. Most of the bones missing in Cope's specimens were preserved (though both were missing the end of the tail), and it was noted for its articulated spinal column.<ref name=HFO09a>{{cite journal |last=Osborn |first=Henry Fairfield |author-link=Henry Fairfield Osborn |year=1909 |title=The Upper Cretaceous iguanodont dinosaurs |journal=Nature |volume=81 |issue=2075 |pages=160–162 |doi=10.1038/081160a0|bibcode=1909Natur..81..160H |doi-access=free }}</ref> The two specimens were mounted in the museum's Hall of Fossil Reptiles in 1908 under the name ''Trachodon mirabilis''.<ref name=BC07/><ref name=HFO09a/> The Cope specimen was mounted in a four legged posture as if feeding, intended to make its well preserved skull open for examination. The second skeleton was posed in an erect posture on two legs, watching for danger, in order to hide its more imperfect skull from view. The base below modeled a shoreline, representing the preservational environment of the specimens and presumed aquatic habits suspected by Brown.<ref name=HFO09a/> Shortly after the completion of the display, Charles Hazelius Sternberg and his sons discovered a mummified hadrosaur specimen (AMNH 5060), covered in skin impressions (some had also been preserved with Cope's specimen, but mostly destroyed in excavation). It too was interpreted as a specimen of ''Trachodon'', though Osborn considered it a ''T. annectens''.<ref name=BC07/><ref name=HFO09a/><ref name="osborn1911">{{cite journal |last = Osborn |first = Henry Fairfield | title=A dinosaur mummy |year=1911 |journal=The American Museum Journal |volume=11 |location = New York, NY |pages=7–11 |url=https://www.biodiversitylibrary.org/item/44617#page/23/mode/1up}}</ref>
===Decline of usage and abandonment=== [[File:Saurolophus_skeleton.jpg|thumb|left|The discovery of new hadrosaur genera such as ''Saurolophus'' caused a shift away from the usage of ''Trachodon'']] Brown's excavations in the American west and Alberta, Canada would continue to uncover "trachodont" (hadrosaur) skeletons, and in 1910 and 1912 respectively he established the new genera ''Kritosaurus'' and ''Saurolophus'' for two such skeletons.<ref name=BC07/><ref name=BB10>{{cite journal |last=Brown |first=Barnum |author-link=Barnum Brown |year=1910 |title=The Cretaceous Ojo Alamo beds of New Mexico with description of the new dinosaur genus ''Kritosaurus'' |journal=Bulletin of the American Museum of Natural History |volume=28 |issue=24 |pages=267–274 |hdl=2246/1398 }}</ref><ref name=BB12>{{cite journal |last=Brown |first=Barnum |author-link=Barnum Brown |year=1912 |title=A crested dinosaur from the Edmonton Cretaceous |journal=Bulletin of the American Museum of Natural History |volume=31 |issue=14 |pages=131–136 |hdl=2246/1401 }}</ref> This represented the first major break from Hatcher's paradigm of ''Trachodon'' dominating hadrosaur taxonomy.<ref name=BC07/> By 1914 Brown recognized seven genera in Trachodontidae, and so he established the subfamilies Trachodontinae for crestless taxa such as ''Trachodon'' and Saurolophinae for those bearing prominent headcrests, such as ''Saurolophus'' and ''Corythosaurus''. Amongst the former he recognized the genus ''Hadrosaurus'' as distinct from ''Trachodon''.<ref name=BB14>{{cite journal|last=Brown|first=B.|year=1914|title=''Corythosaurus casuarius'', a New Crested Dinosaur from the Belly River Cretaceous, with Provisional Classification of the Family Trachodontidae|journal=American Museum of Natural History Bulletin|volume=33|url=http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/1734/v2/dspace/ingest/pdfSource/bul/B033a35.pdf?sequence=1|pages=559–565}}</ref> In light of the proliferation of taxa, in 1915 Charles W. Gilmore returned to Hatcher's conclusions, regretting that ''Trachodon'' had come to be so widely used without taxonomic caution. He noted the insufficient nature of Leidy's original teeth for identification at the species level (something even Hatcher was aware of). Furthermore, he noted distinction between the number of teeth in Judith and Lancian hadrosaurs. Consequently, he considered the longstanding conclusion that Cope's specimen and others belonged to ''Trachodon mirabilis'', and instead he placed them in a revived ''Thespesius occidentalis''. As for ''Trachodon'', he suggested it would be appropriate to use it as the name for one of the species from older strata (as an age difference between the Judith and Lance had now been appreciated).<ref name=BC07/><ref name=CWG15>Gilmore, C.W. (1915). On the genus ''Trachodon''. ''Science'' 41:658–660.</ref> [[File:Dinosaurs_in_the_American_Museum_of_Natural_History,_20231005_160159.jpg|thumb|The original "''Trachodon''" mounts still stand today, now recognized as ''Edmontosaurus annectens'' specimens]] Lambe would publish a study in 1918, also cautioning against the extensive usage of ''Trachodon''. If it was to be used, he argued it must stand based on the identification of the original single-rooted tooth. He noted that the tooth seemed distinct in anatomy from that known in any hadrosaur. Thus, he considered it possible it represented a distinct species from any other then known. However, he also noted it was possible the tooth did not represent ordinary dental anatomy, and would thus be entirely useless for taxonomic purposes, with ''Trachodon'' consequently abandoned from use. He also noted that several of the other genera and species Hatcher synonymized with ''Trachodon'' were, themselves, based on insufficient material and required extensive revision. The complete skeletons referred to ''T. mirabilis'' were suggested to be retained in the genus ''Diclonius'', oweing to their historical association with the name.<ref name=Lambe2018>Lambe, L. (1918). On the genus Trachodon of Leidy. Ottawa Naturalist 31:135–139</ref> William Parks supported the disuse of ''Trachodon'' in 1920, noting that Lambe's argument against ''Trachodon'' was made with good reason.<ref name=WAP20>{{cite journal |last=Parks |first=William A. |author-link=William Parks (paleontologist) |year=1920 |title=The osteology of the trachodont dinosaur ''Kritosaurus incurvimanus'' |journal=University of Toronto Studies, Geology Series |volume=11 |pages=1–76}}</ref>
Lambe also noted the seniority of Hadrosauridae over Trachodontidae, which had been the dominant term for hadrosaurs since Hatcher's paper. Likewise, he deprecated Trachodontinae in favor of Hadrosaurinae for the flat-crested forms.<ref name=Lambe2018/> In a 1936 paper Charles Mortram Sternberg (son of Charles Hazelius) attempted to identify whether ''Trachodon'' represented a flat-crested (hadrosaurine) or crested (by then, lambeosaurine) hadrosaur as a basis for any future use of the genus. He concluded it represented a lambeosaur, though preferred to retain the term Lambeosaurinae over bringing back the term Trachodontinae.<ref name=CMS36>Sternberg, C.M. (1936). The systematic position of ''Trachodon''. ''Journal of Paleontology'' 10(7):652–655.</ref>
In 1942, Richard Swann Lull and Nelda Wright published a monograph titled ''Hadrosaurian Dinosaurs of North America'', based on an unrealized monograph on Ornithopoda planned by Cope. As with prior authors, they disassociated the original ''Trachodon'' teeth from later skeletons. Like prior authors, they noticed the distinct rough texture of the tooth. However, they made the novel observation of similar but much fainter rough texturing on teeth belonging to ''Hadrosaurus''. In the wake of this observation, it became clear that the tooth of ''Trachodon'' was a freshly deposited tooth, and its rough texture was not a trait identifying it taxonomically but instead due to the tooth not having been worn down by use in chewing. Without this distinguishing trait, it was considered impossible to determine which of several hadrosaurs from the same time period ''Trachodon'' belonged to.<ref name=LW42/> Following this, the name fell into scientific disuse as a dubious name.<ref name=dodson2009>{{cite journal | url=https://paleontological.s3.amazonaws.com/PDF/american-paleontologist/AP-V17-N2.pdf | title=Dinosaurs in America – Joseph Leidy & the Academy of Natural Sciences | author=Dodson, P. | journal=American Paleontologist | year=2009 | volume=19 | issue=2 | pages=31–35}}</ref><ref name=WPCJ88>Coombs, Jr., W.P. (1988). The status of the dinosaurian genus ''Diclonius'' and the taxonomic utility of hadrosaurian teeth. ''Journal of Paleontology'' 62:812–818.</ref><ref name=HWF04>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}}</ref> In the realm of pop culture, however, the name would persist in contexts like books well into future decades.<ref name=dodson2009/> Regarding Cope's skeleton and the other material later referred to ''Trachodon'', Lull and Wright named the genus ''Anatosaurus'' to contain ''T. annectens'', and established the species ''Anatosaurus copei'' for Cope's skeleton and the 1904 specimen. Both species, eventually, be subsumed into the single species ''Edmontosaurus annectens''.<ref name=BC07/><ref name=dodson2009/><ref name=NCDE11>{{cite journal | last1 = Campione | first1 = N.E. | last2 = Evans | first2 = D.C. | year = 2011 | title = Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America | journal = PLOS ONE | volume = 6 | issue = 9| article-number = e25186 | doi = 10.1371/journal.pone.0025186 | pmid = 21969872 | pmc=3182183| bibcode = 2011PLoSO...625186C | doi-access = free }}</ref>
==Species==
thumb|right|''T. selwyni'' teethNumerous species have been referred to this genus.
Type species: ''T. mirabilis'' Leidy, 1856<ref name="JL56" />
Other species: *''T.'' (''Pteropelyx'') ''altidens'' was described by Lambe in 1902 on the basis of a left maxilla with teeth that was found in the Upper Cretaceous-aged strata of the Dinosaur Park Formation in Alberta, Canada.<ref name="lambe1902" /> It has a long and convoluted history, being assigned to ''Prochenosaurus,''<ref name="LW42" /> ''Lambeosaurus,'' and its own genus, ''Didanodon''.<ref name="osborn1902">{{cite journal|last=Osborn|first=H.F.|author-link=Henry Fairfield Osborn|year=1902|title=Distinctive characters of the Mid-Cretaceous fauna|journal=Geological Survey of Canada. Contributions to Canadian Palaeontology. Part II. On Vertebrata of the Mid-Cretaceous of the North West Territory|volume=3|issue=2|pages=5–21}}</ref> However, recent studies consider it either a ''nomen dubium'' and indeterminate hadrosaurid or as a synonym of ''Lambeosaurus lambei''.<ref name="horner2004">{{cite book|last1=Horner|first1=J.R.|author-link1=Jack Horner (paleontologist)|last2=Weishampel|first2=D.B.|author-link2=David B. Weishampel|last3=Forster|first3=C.A.|year=2004|chapter=Hadrosauridae|editor-last=Weishampel|editor-first=D.B.|editor2-last=Dodson|editor2-first=P.|editor3-last=Osmólska|editor3-first=H|title=The Dinosauria|edition=2nd|publisher=University of California Press|pages=438–463|isbn=978-0-520-24209-8}}</ref><ref name="lund2006">{{cite journal|last1=Lund|first1=E.K.|last2=Gates|first2=T.A.|year=2006|title=A historical and biogeographical examination of hadrosaurian dinosaurs|journal=New Mexico Museum of Natural History and Science Bulletin|volume=35|pages=263–276}}</ref> *''T. amurense'' was described by Russian paleontologist Anatoly Riabinin in 1925, from a partial skeleton that was unearthed in Upper Cretaceous rocks of the Amur River banks of Heilongjiang in Manchuria Province, northern China.<ref name="ANR25">Riabinin, A.N. (1925). A mounted skeleton of the gigantic reptile ''Trachodon amurense'', nov. sp. ''Izvest. Geol. Kom.'' 44(1):1–12. [Russian]</ref> It was later amended to ''T. amurensis'' and now is the type species of ''Mandschurosaurus''.<ref name="ANR30">Riabinin, A.N. (1930). ''Mandschurosaurus amurensis'', nov. gen., nov. sp., a hadrosaurian dinoasur from the Upper Cretaceous of Amur River. ''Mémoir II, Société Paléontologique de Russie.'' [Russian]</ref> However, some authors state it is a ''nomen dubium''.<ref name="Surman79">{{cite journal|author=Brett-Surman M. K.|year=1979|title=Phylogeny and palaeobiogeography of hadrosaurian dinosaurs|journal=Nature|volume=277|pages=560–562|doi=10.1038/277560a0|issue=5697|bibcode=1979Natur.277..560B|s2cid=4332144}}</ref><ref>Borinder, Niclas & Poropat, Stephen & Campione, Nicolás & Wigren, Tomas & Kear, Benjamin. (2021). Postcranial osteology of the basally branching hadrosauroid dinosaur ''Tanius sinensis'' from the Upper Cretaceous Wangshi Group of Shandong, China. ''Journal of Verterbrate Paleontology''. [https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1914642 10.1080/02724634.2021.1914642.] </ref> *''T. cantabrigiensis'' was named by British paleontologist Richard Lydekker in 1888 based on a dentary tooth that was collected from the strata of the Cambridge Greensand, which dates to the Lower Cretaceous, in Cambridgeshire, England.<ref name="RL88" /> It is now regarded as a dubious basal hadrosaurid.<ref name="WH90">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}}</ref><ref name="HWF04" /> *''T. longiceps'' was named by Marsh in 1897 on the bases of a large right dentary bearing teeth from the late Maastrichtian-aged Upper Cretaceous Lance Formation of Wyoming, USA.<ref name="OCM97">Marsh, O.C. (1897). Vertebrate fossils of the Denver Basin. ''U.S. Geological Survey, Monthly'' 27:473–527.</ref> It is now believed to be a synonym of ''Edmontosaurus annectens''.<ref name="WH90" /> *''T. marginatus'' was described by Lambe in 1902 based on a disassociated postcranial skeleton that had been found in rocks of the Belly River Group in Alberta, Canada.<ref name="LL02">Lambe, L.M. (1902). On Vertebrata of the mid-Cretaceous of the Northwest Territory. 2. New genera and species from the Belly River Series (mid-Cretaceous). ''Contributions to Canadian Paleontology'' 3:25–81.</ref> It has since been classified as its own genus, ''Stephanosaurus,<ref name="LL14" />'' a species of ''Kritosaurus,<ref name="CWG24">{{cite journal |last=Gilmore |first=Charles W. |author-link=Charles Whitney Gilmore |year=1924 |title=On the genus ''Stephanosaurus'', with a description of the type specimen of ''Lambeosaurus lambei'', Parks |journal=Canada Department of Mines Geological Survey Bulletin (Geological Series) |volume=38 |issue=43 |pages=29–48}}</ref>'' or an indeterminate hadrosaurid.<ref name="WH90" /><ref name="HWF04" /> *''T. selwyni'' was named by Lambe in 1902 on the basis of a dentary with teeth that was discovered in the Upper Cretaceous-aged strata of the Dinosaur Park Formation in Alberta, Canada.<ref name="LL02" /> It is now believed to be a ''nomen dubium'', too fragmentary to classify beyond Hadrosauridae.<ref name="WH90" /><ref name="HWF04" /> Reassigned species
* ''T. imperfectus'', <small>Kuhn, 1964 (Young, 1944)</small> = ''Sanpasaurus imperfectus'' <small>Young, 1944</small> * ''T. agilis'', <small>Kuhn, 1936 (Marsh, 1890)</small> = ''Claosaurus agilis'' <small>Marsh, 1890</small> * ''T. annectens'', <small>Hay, 1902 (Marsh, 1892)</small> = ''Edmontosaurus annectens'' (<small>Marsh, 1892)</small><ref>{{Cite journal |last=Lucas |first=Frederic A. |date=1903 |title=The dinosaur Trachodon annectens |url=http://hdl.handle.net/10088/23220 |journal=Smithsonian Miscellaneous Collections |language=en |volume=45 |issue=27 |pages=317-20}}</ref> * ''T. imperfectus'', <small>(Kuhn, 1964) Young 1944</small> = ''Sanpasaurus imperfectus'' <small>Young 1944</small>
== Description == ''Trachodon mirabilis'' is known definitively from a single, isolated tooth (ANSP 9260), likely from the mandible (lower jaw).<ref name="LW42" /> ANSP 9260 was described briefly in Leidy's 1856 description. The tooth is overall hexahedronal in shape, though is slightly bent, and measures {{Convert|1.4|in|mm}} in length and {{Convert|0.5|in|mm}} in maximum diameter. The exposed surface is smooth with a pronounce median ridge running the length of the tooth, while the lateral margins of the tooth have subacute lateral (side) ridges. In contrast, the tooth's interior features rough, irregular granulations. As for the base, it is broken but preserves its hollow structure.<ref name="JL56" /> Its features lack any abrasion or wear, which, along with its rough internal surface, suggest it was a recently sprouted virgin (unused) tooth. This roughness is the origin of the genus name, however it likely is not indicative of any genus or species but instead is a result of it a being newly formed tooth.<ref name="LW42" /> [[File:Life reconstruction of Lambeosaurus lambei.png|thumb|274x274px|A life restoration of ''Lambeosaurus'', a possible relative of ''Trachodon'']] As a hadrosaur, ''Trachodon'' would have had a large, long skull terminating in a beak with an extensive keratin sheath, a significant battery of teeth, and roughly triangular shaped head.<ref name="cope1883" /> It was a large hadrosaurid, with highly developed jaws full of grinding teeth, a long tail stiffened by ossified tendons that prevented it from drooping, and more elongate limbs suggesting they were semi-quadrupedal (could move on both two legs and all fours), as also shown by footprints of related animals. The hands had four fingers, lacking the thumb, and while the second, third, and fourth fingers were bunched together, the little finger was free and could have been used to manipulate objects. Each foot had only the three central toes.<ref name="HWF04" />
If it was a lambeosaurine, ''Trachodon'' likely bore a large, thin crest made up of the premaxilla and nasal bones that could have been used for display,<ref>{{Cite journal |last=Evans |first=David C. |date=2006 |title=Nasal cavity homologies and cranial crest function in lambeosaurine dinosaurs |url=https://www.cambridge.org/core/journals/paleobiology/article/abs/nasal-cavity-homologies-and-cranial-crest-function-in-lambeosaurine-dinosaurs/8B5BE1ECD7839F6188A1A6C38CA12B83 |journal=Paleobiology |language=en |volume=32 |issue=1 |pages=109–125 |doi=10.1666/0094-8373(2006)032[0109:NCHACC]2.0.CO;2 |issn=0094-8373}}</ref> sound amplification,<ref>{{Cite journal |last=Weishampel |first=David B. |date=1981 |title=Acoustic analyses of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia) |url=https://www.cambridge.org/core/journals/paleobiology/article/abs/acoustic-analyses-of-potential-vocalization-in-lambeosaurine-dinosaurs-reptilia-ornithischia/EAE69C97E11D8A3FDCCF980C7D39DC01 |journal=Paleobiology |language=en |volume=7 |issue=2 |pages=252–261 |doi=10.1017/S0094837300004036 |issn=0094-8373}}</ref> and/or species recognition.<ref>{{Cite journal |last=Evans |first=David C. |last2=Ridgely |first2=Ryan |last3=Witmer |first3=Lawrence M. |date=2009 |title=Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria: Ornithischia): A Sensorineural Perspective on Cranial Crest Function |url=https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.20984 |journal=The Anatomical Record |language=en |volume=292 |issue=9 |pages=1315–1337 |doi=10.1002/ar.20984 |issn=1932-8486}}</ref> Skin impressions are known from several lambeosaurines, including ''Parasaurolophus, Lambeosaurus,'' and ''Corythosaurus'', which indicate that they were covered in small scales with an arrangement of feature scales (larger scales within a matrix of smaller scales) as well.<ref>{{Cite journal |last=Evans |first=David |last2=Reisz |first2=Robert |date=2007 |title=Anatomy and Relationships of Lambeosaurus magnicristatus, a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta. |url=https://www.tandfonline.com/doi/abs/10.1671/0272-4634%282007%2927%5B373%3AAAROLM%5D2.0.CO%3B2 |journal=Journal of Vertebrate Paleontology |volume=27 |issue=2 |pages=373-393}}</ref> Most depictions of ''Trachodon'' are based on specimens now assigned to ''Edmontosaurus'', a genus of saurolophine rather than lambeosaurine. ''Edmontosaurus''' skull is long and low, lacks a bony crest, and bears a soft-tissue crest,<ref name="sereno2026">{{cite journal |last1=Sereno |first1=Paul C. |last2=Saitta |first2=Evan T. |last3=Vidal |first3=Daniel |last4=Myhrvold |first4=Nathan |last5=Real |first5=María Ciudad |last6=Baumgart |first6=Stephanie L. |last7=Bop |first7=Lauren L. |last8=Keillor |first8=Tyler M. |last9=Eriksen |first9=Marcus |last10=Derstler |first10=Kraig |year=2026 |title=Duck-billed dinosaur fleshy midline and hooves reveal terrestrial clay-template 'mummification' |journal=Science |volume=391 |issue=6780 |article-number=eadw3536 |doi=10.1126/science.adw3536}}</ref><ref>{{Cite web |last=Dunham |first=Will |date=23 October 2025 |title=Wyoming dinosaur 'mummies' reveal a surprise: hoofed feet |url=https://www.reuters.com/science/wyoming-dinosaur-mummies-reveal-surprise-hoofed-feet-2025-10-23/ |url-status=live |access-date=27 October 2025 |website=Reuters}}</ref><ref>{{Cite news |last=Tamisiea |first=Jack |date=23 October 2025 |title=Two New Dinosaur Fossils Emerge From the 'Mummy Zone' |url=https://www.nytimes.com/2025/10/23/science/dinosaur-mummies-wyoming.html |access-date=27 October 2025 |work=The New York Times |language=en}}</ref> unlike those of lambeosaurines.<ref>{{Cite journal |last=Dodson |first=Peter |date=1975 |title=Taxonomic Implications of Relative Growth in Lambeosaurine Hadrosaurs |url=https://www.jstor.org/stable/2412696 |journal=Systematic Zoology |volume=24 |issue=1 |pages=37–54 |doi=10.2307/2412696 |issn=0039-7989}}</ref><ref name="BB14" />
==Paleoecology== [[File:Judith River Formation (Montana) geology and stratigraphy.jpg|thumb|274x274px|Map and stratigraphy of the Judith River Formation, where ''Trachodon'' is known]] ''Trachodon'' lived in a vast floodplain along the western shore of the interior seaway. Large rivers watered the land, occasionally flooding and blanketing the region with new sediment. When water was plentiful, the region could support a great deal of plant and animal life, but periodic droughts also struck the region, resulting in mass mortality as preserved in the many bonebed deposits found in Judith River sediments, including a ''Daspletosaurus,'' a genus of large tyrannosaurid theropod, bonebed.<ref name="rogers1990">{{cite journal |last=Rogers |first=Raymond R. |year=1990 |title=Taphonomy of three dinosaur bonebeds in the Upper Cretaceous Two Medicine Formation of northwestern Montana: evidence for drought-induced mortality |journal=PALAIOS |volume=5 |issue=5 |pages=394–413 |bibcode=1990Palai...5..394R |doi=10.2307/3514834 |jstor=3514834}}</ref> Similar conditions exist today in East Africa.<ref name="falconlang2003">{{cite journal |last=Falcon-Lang |first=Howard J. |year=2003 |title=Growth interruptions in silicified conifer woods from the Upper Cretaceous Two Medicine Formation, Montana, USA: implications for palaeoclimate and dinosaur palaeoecology |url=http://doc.rero.ch/record/14531/files/PAL_E1733.pdf |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=199 |issue=3–4 |pages=299–314 |bibcode=2003PPP...199..299F |doi=10.1016/S0031-0182(03)00539-X}}</ref> Volcanic eruptions from the west periodically blanketed the region with ash, also resulting in large-scale mortality, while simultaneously enriching the soil for future plant growth. It is these ash beds that allow precise radiometric dating as well. Fluctuating sea levels also resulted in a variety of other environments at different times and places within the Judith River Group, including offshore and nearshore marine habitats, coastal wetlands, deltas, and lagoons, in addition to the inland floodplains.<ref name="eberth1997">{{cite book |last=Eberth |first=David A. |url=https://archive.org/details/encyclopediadino00curr_075 |title=Encyclopedia of Dinosaurs |publisher=Academic Press |year=1997 |isbn=978-0-12-226810-6 |editor=Currie, Philip J. |editor-link=Phil Currie |location=San Diego |pages=[https://archive.org/details/encyclopediadino00curr_075/page/n229 199]–204 |chapter=Judith River Wedge |editor2=Padian, Kevin |url-access=limited}}</ref>
The excellent vertebrate fossil record of Judith River rocks resulted from a combination of abundant animal life, periodic natural disasters, and the deposition of large amounts of sediment. Many types of freshwater and estuarine fish are represented, including sharks, rays, sturgeons, gars, and others. The Judith River Formation preserves the remains of many aquatic amphibians and reptiles, including frogs, salamanders, turtles, ''Champsosaurus'' and crocodilians. Terrestrial lizards, including whiptails, parasaniwids, and knob-scaled lizards have also been discovered.<ref name="eberth19972">{{cite book |last=Eberth |first=David A. |url=https://archive.org/details/encyclopediadino00curr_075 |title=Encyclopedia of Dinosaurs |publisher=Academic Press |year=1997 |isbn=978-0-12-226810-6 |editor=Currie, Philip J. |editor-link=Phil Currie |location=San Diego |pages=[https://archive.org/details/encyclopediadino00curr_075/page/n229 199]–204 |chapter=Judith River Wedge |editor2=Padian, Kevin |url-access=limited}}</ref>
As for dinosaurs, a menagerie are known. Theropods are represented by tyrannosaurids like ''Daspletosaurus'' and ''Gorgosaurus'',<ref name=":0">{{Cite journal |last=Carr |first=Thomas D. |date=2018 |title=Significant geographic range extension for the sympatric tyrannosaurids ''Albertosaurus libratus'' and ''Daspletosaurus torosus'' from the Judith River Formation (Late Campanian) of northern Montana |url=https://vertpaleo.org/wp-content/uploads/2021/03/SVP-2018-program-book-V4-FINAL-with-covers-9-24-18.pdf |journal=Journal of Vertebrate Paleontology |volume=38 |issue=Supplement 1 |page=102}}</ref> dromaeosaurs like ''Saurornitholestes'' and ''Dromaeosaurus'',<ref>{{Cite journal |last=Brinkman |first=Donald B. |date=1 May 1990 |title=Paleooecology of the Judith River Formation (Campanian) of Dinosaur Provincial Park, Alberta, Canada: Evidence from vertebrate microfossil localities |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=78 |issue=1 |pages=37–54 |doi=10.1016/0031-0182(90)90203-J |bibcode=1990PPP....78...37B |issn=0031-0182}}</ref><ref>{{Citation |last1=Currie |first1=Philip J. |title=Theropod teeth from the Judith River Formation of southern Alberta, Canada |date=1990 |work=Dinosaur Systematics: Approaches and Perspectives |pages=107–126 |editor-last=Carpenter |editor-first=Kenneth |url=https://www.cambridge.org/core/books/dinosaur-systematics/theropod-teeth-from-the-judith-river-formation-of-southern-alberta-canada/10FA3AAB72A3FD948D3573DACD905622 |access-date=14 April 2026 |place=Cambridge |publisher=Cambridge University Press |isbn=978-0-521-43810-0 |last2=Rigby |first2=J. Keith |last3=Sloan |first3=Robert E. |editor2-last=Currie |editor2-first=Philip J.}}</ref> the possibly valid troodontid ''Troodon'',<ref>{{Cite journal |last1=Varricchio |first1=David J. |last2=Hogan |first2=Jason D. |last3=Gardner |first3=Jacob D. |date=2025 |title=Troodontid specimens from the Cretaceous Two Medicine Formation of Montana (USA) and the validity of Troodon formosus |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/troodontid-specimens-from-the-cretaceous-two-medicine-formation-of-montana-usa-and-the-validity-of-troodon-formosus/3E58F1FDA3FE53DE569E0D0B20E79F22 |journal=Journal of Paleontology |language=en |volume=99 |issue=1 |pages=219–240 |doi=10.1017/jpa.2024.67 |bibcode=2025JPal...99..219V |issn=0022-3360}}</ref>, an indeterminate, ''Deinocheirus''-like ornithomimosaur,<ref name="Chinzorig2025">{{Cite journal |last1=Chinzorig |first1=Tsogtbaatar |last2=Takasaki |first2=Ryuji |last3=Chiba |first3=Kentaro |last4=Fiorillo |first4=Anthony R. |last5=Kobayashi |first5=Yoshitsugu |last6=Saneyoshi |first6=Mototaka |last7=Ishigaki |first7=Shinobu |date=10 September 2025 |title=A potential deinocheirid ornithomimosaur from the Judith River Formation (Upper Cretaceous: Montana, U.S.A.) and its paleobiogeographic implications |journal=Journal of Vertebrate Paleontology |language=en |volume=e2536844 |issue=2 |pages=(13 pages) |article-number=e2536844 |doi=10.1080/02724634.2025.2536844 |doi-access= |bibcode=2025JVPal..4536844C }}</ref> the bird ''Hesperornis,<ref name="fox1974">Fox, R.C. (1974). "A middle Campanian, nonmarine occurrence of the Cretaceous toothed bird ''Hesperornis'' Marsh." ''Canadian Journal of Earth Sciences'', '''11''': 1335-1338.</ref>'' and the enigmatic ''Richardoestesia.<ref name=":5">{{Cite journal |last1=Fiorillo |first1=Anthony R. |last2=Currie |first2=Philip J. |date=31 March 1994 |title=Theropod teeth from the Judith River Formation (Upper Cretaceous) of south-central Montana |url=https://www.researchgate.net/publication/40662369 |journal=Journal of Vertebrate Paleontology |language=en |volume=14 |issue=1 |pages=74–80 |doi=10.1080/02724634.1994.10011539 |bibcode=1994JVPal..14...74F |issn=0272-4634}}</ref>'' Many other ornithischians have been unearthed from Judith River, such as the ankylosaurid ''Zuul'',<ref>{{Cite journal |last1=Arbour |first1=Victoria M. |last2=Evans |first2=David C. |date=2017 |title=A new ankylosaurine dinosaur from the Judith River Formation of Montana, USA, based on an exceptional skeleton with soft tissue preservation |journal=Royal Society Open Science |language=en |volume=4 |issue=5 |article-number=161086 |doi=10.1098/rsos.161086 |doi-access=free |issn=2054-5703 |pmc=5451805 |pmid=28573004 |bibcode=2017RSOS....461086A }}</ref> the hadrosaurids ''Brachylophosaurus, Corythosaurus,'' and ''Probrachylophosaurus,''<ref name=":1">{{Cite journal |last1=Takasaki |first1=Ryuji |last2=Chiba |first2=Kentaro |last3=Fiorillo |first3=Anthony R. |last4=Brink |first4=Kirstin S. |last5=Evans |first5=David C. |last6=Fanti |first6=Federico |last7=Saneyoshi |first7=Mototaka |last8=Maltese |first8=Anthony |last9=Ishigaki |first9=Shinobu |date=2023 |title=Description of the first definitive Corythosaurus (Dinosauria, Hadrosauridae) specimens from the Judith River Formation in Montana, USA and their paleobiogeographical significance |url=https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25097 |journal=The Anatomical Record |language=en |volume=306 |issue=7 |pages=1918–1938 |doi=10.1002/ar.25097 |pmid=36273398 |issn=1932-8486}}</ref> the ceratopsians ''Judiceratops,''<ref>{{Cite journal |last=Longrich |first=Nicholas R. |date=April 2013 |title=Judiceratops tigris , a New Horned Dinosaur from the Middle Campanian Judith River Formation of Montana |url=http://www.bioone.org/doi/abs/10.3374/014.054.0103 |journal=Bulletin of the Peabody Museum of Natural History |language=en |volume=54 |issue=1 |pages=51–65 |doi=10.3374/014.054.0103 |bibcode=2013BPMNH..54...51L |issn=0079-032X}}</ref> ''Lokiceratops,''<ref>{{Cite journal |last1=Loewen |first1=Mark A. |last2=Sertich |first2=Joseph J. W. |last3=Sampson |first3=Scott |last4=O'Connor |first4=Jingmai K. |last5=Carpenter |first5=Savhannah |last6=Sisson |first6=Brock |last7=Øhlenschlæger |first7=Anna |last8=Farke |first8=Andrew A. |last9=Makovicky |first9=Peter J. |last10=Longrich |first10=Nick |last11=Evans |first11=David C. |date=20 June 2024 |title=Lokiceratops rangiformis gen. et sp. nov. (Ceratopsidae: Centrosaurinae) from the Campanian Judith River Formation of Montana reveals rapid regional radiations and extreme endemism within centrosaurine dinosaurs |journal=PeerJ |language=en |volume=12 |article-number=e17224 |doi=10.7717/peerj.17224 |doi-access=free |issn=2167-8359 |pmc=11193970 |pmid=38912046}}</ref> ''Medusaceratops,'' and ''Spiclypeus'',<ref>{{Cite journal |last=Fowler |first=Denver Warwick |date=22 November 2017 |title=Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America |journal=PLOS ONE |language=en |volume=12 |issue=11 |article-number=e0188426 |doi=10.1371/journal.pone.0188426 |doi-access=free |issn=1932-6203 |pmc=5699823 |pmid=29166406 |bibcode=2017PLoSO..1288426F }}</ref> and the pachycephalosaurids ''Colepiocephale'' and ''Hanssuesia''.<ref>{{Cite journal |last=Sullivan |first=Robert M. |date=2003 |title=Revision of the Dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae) |journal=Journal of Vertebrate Paleontology |volume=23 |issue=1 |pages=181–207 |doi=10.1671/0272-4634(2003)23[181:ROTDSL]2.0.CO;2 |jstor=4524305 |issn=0272-4634}}</ref> Multiple other dubious dinosaurs that were described from Judith River by Leidy or during the Bone Wars, a scientific feud between paleontologists Edward Drinker Cope and Othniel Charles Marsh, include ''Aublysodon,<ref name="sahni1972">Sahni, A. (1972). "The vertebrate fauna of the Judith River Formation, Montana." ''Bulletin of the AMNH'', v. '''147''' article 6: 321-415.</ref> Ceratops,''<ref>{{Cite journal |last=Marsh |first=Othniel Charles |date=1 December 1888 |title=A new family of horned Dinosauria, from the Cretaceous |url=https://ajsonline.org/article/62691-a-new-family-of-horned-dinosauria-from-the-cretaceous |journal=American Journal of Science |language=en |volume=s3-36 |issue=216 |pages=477–478 |doi=10.2475/ajs.s3-36.216.477 |bibcode=1888AmJS...36..477M }}</ref> ''Deinodon,<ref name=":3">{{Cite journal |last=Leidy |first=J. |date=31 December 1856 |title=Notice of remains of extinct reptiles and fishes, discovered by Dr. FV Hayden in the Bad Lands of the Judith River, Nebraska Territory. |url=https://zenodo.org/record/1038128 |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=8 |pages=72–73 |doi=10.5281/zenodo.1038128}}</ref>'' and ''Pteropelyx''.<ref name=":1" /> As a hadrosaurid, ''Trachodon'' would have been a large, bipedal/quadrupedal herbivore.<ref name="HWF04" />
==See also== {{Portal|Dinosaurs}} * Timeline of hadrosaur research * ''Eotrachodon''
==References== {{Reflist}}
{{Ornithopoda|D.}} {{Taxonbar|from=Q1060870}}
Category:Hadrosauridae Category:Dinosaur genera Category:Campanian dinosaurs Category:Judith River Formation Category:Taxa named by Joseph Leidy Category:Fossil taxa described in 1856 Category:Dinosaurs of the United States Category:Tooth taxa Category:Nomina dubia