Name: Monoclonius ‭(‬Single sprout‭)‬.
Phonetic: Mon-oh-clo-nee-us.
Named By: Edward Drinker Cope‭ ‬-‭ ‬1876.
Synonyms: Monoclonius lowei?
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Ornithichia,‭ ‬Ceratopsidae,‭ ‬Centrosaurinae.
Species: M.‭ ‬crassus‭ (‬type‭)‬,‭ ‬M.‭ ‬lowei?
Diet: Herbivore.
Size: Unknown.
Known locations: USA,‭ ‬Montana.‭ ‬Possibly Canada.
Time period: Late Cretaceous.
Fossil representation: Partial skull and cervical‭ (‬neck‭) ‬vertebrae.

       So the taxonomic history of Monoclonius goes a little something like this.‭ ‬In‭ ‬1876‭ ‬multiply dinosaur fossils were recovered from the Judith River in Montana,‭ ‬USA.‭ ‬These fossils were sent to Edward Drinker Cope‭ (‬One of the two main figures in the Bone Wars‭) ‬and from these two new dinosaur genera were named,‭ ‬Monoclonius and Diclonius.‭ ‬Cope believed that both of these dinosaurs were hadrosaurs and gave them names which meant‭ ‘‬single sprout‭’ ‬and‭ ‘‬double sprout‭’‬,‭ ‬a reference to‭ ‬the observation that Monoclonius had a single row of teeth in use at any one time,‭ ‬and Diclonius had two rows.‭
       In‭ ‬1889‭ ‬Othniel Charles Marsh‭ (‬The other main figure in the Bone Wars‭) ‬named what would become one of the most famous dinosaurs of all time,‭ ‬Triceratops.‭ ‬Cope made a point to keep up to date with Marsh’s work,‭ ‬and when he saw the work on Triceratops,‭ ‬he realised that he himself had made a mistake.‭ ‬Going over his fossils of Monoclonius,‭ ‬as well as an earlier genus named Agathaumus that he had‭ ‬also‭ ‬named,‭ ‬Cope realised that these two genera when combined with Triceratops would actually represent a whole new group of what would later become known as ceratopsian dinosaurs.

       When Cope had first named Monoclonius he was unsure how to piece it together,‭ ‬resulting in the incorrect identification of it being a hadrosaur.‭ ‬Now armed with the knowledge of Triceratops however,‭ ‬Cope re-assembled his Monoclonius fossils,‭ ‬identifying the horn core,‭ ‬neck frill,‭ ‬and cervical‭ (‬neck‭) ‬vertebrae,‭ ‬which he originally thought were dorsal‭ (‬back‭) ‬vertebrae.‭ ‬This resulted in a re-description published later in‭ ‬1889,‭ ‬which saw Monoclonius reconstructed as a ceratopsian dinosaur with a single large horn rising up from its nasal bone.‭ ‬However cope achieved this by adding additional fossil specimens to his existing Monoclonius fossils.‭ ‬This was also the start of the confusion about the meaning of the name Monoclonius with many people interpreting it as meaning‭ ‘‬single horn‭’ ‬when in fact it still meant‭ ‘‬single sprout‭’ ‬with a continued reference to the teeth.
       After this Monoclonius became what is known as a‭ ‘‬wastebasket taxon‭’‬,‭ ‬with any other slightly similar ceratopsian fossils being assigned to Monoclonius.‭ ‬Even when the fossils were clearly different,‭ ‬they would simply become a new species,‭ ‬and eventually the Monoclonius genus would attain nearly twenty species.‭ ‬Perhaps the main reason why this happened is because what we now call the centrosaurine ceratopsians commonly have single large horns,‭ ‬and short neck frills,‭ ‬just like what Monoclonius was perceived to have had.
       In‭ ‬1895‭ ‬Cope sold much of his fossil collection to the American Museum of Natural History in order to keep funding his work‭ (‬The Bone Wars had a terrible effect upon the personal finances of both Cope and Marsh‭)‬.‭ ‬After the deaths of both Cope and Marsh,‭ ‬John Bell Hatcher,‭ ‬a former worker of Marsh’s was assigned the task of completing Marsh’s unfinished monograph on ceratopsian dinosaurs,‭ ‬this time including Copes fossils.‭ ‬When Hatcher got round to the type specimen of Monoclonius,‭ ‬he concluded that it was actually based upon the fossils of several dinosaurs,‭ ‬not all of them necessarily representing the same individual.‭ ‬This was finally published in‭ ‬1907‭ ‬after hatcher himself died and the monograph was finished by Richard Swann Lull.
       This was not the beginning of serious doubts about the Monoclonius genus,‭ ‬in‭ ‬1904,‭ ‬fossils of two species were used to create a new genus called Centrosaurus,‭ ‬which is today the type genus of the Centrosaurinae.‭ ‬Other former species of Monoclonius have now been largely re-assigned into other genera including Avaceratops,‭ ‬Brachyceratops,‭ ‬Chasmosaurus,‭ ‬Eoceratops and Styracosaurus,‭ ‬while fossils that were not have often been described as too indeterminate.‭
       Palaeontologists have always been at odds over how valid Monoclonius is however.‭ ‬Lawrence Lambe considered Centrosaurus to be very distinct from Monoclonius,‭ ‬while Barnum Brown thought that all Monoclonius species named at that time were synonymous with the type species that had been based upon eroded fossils.‭ ‬In‭ ‬1933‭ ‬Richard Lull published a paper citing that Centrosaurus should be a sub genus to Monoclonius,‭ ‬while in‭ ‬1938‭ ‬Charles Mortram Sternberg claimed that Monoclonius fossils were slightly older than Centrosaurus fossils,‭ ‬and that Monoclonius was a probable ancestor to Centrosaurus.‭ ‬In‭ ‬1990‭ ‬Peter Dodson noted a clear difference in the parietal bone,‭ ‬while a‭ ‬1997‭ ‬study‭ (‬Sampson et al‭) ‬concluded that all remaining Monoclonius fossils were dubious because analysis of the bone indicated that they were either juveniles or subadults.‭ ‬A counter paper in‭ ‬1998‭ ‬by Dodson and Tumarkin was of the opinion that these‭ ‬juvenile features had been retained in adulthood,‭ ‬and noted that one of the‭ ‬M.‭ ‬lowei holotype had the longest known interparietal bones of any centrosaurine ceratopsian dinosaur.‭ ‬A‭ ‬2006‭ ‬paper by Michael Ryan however confirmed that the holotype skull of M.‭ ‬lowei was indeed a subadult,‭ ‬though one of exceptional size.
       With the history behind us,‭ ‬the state of Monoclonius at the time of writing is that it is usually treated as a dubious genus of ceratopsian dinosaur by most authors.‭ ‬This is because the remains of the type species M.‭ ‬crassus are not very diagnostic,‭ ‬which makes it difficult to establish the holotype of the species M.‭ ‬lowei with certainty,‭ ‬though it has also been considered to be synonymous with the type species.‭ ‬With the history done with,‭ ‬there really isn’t that much more to say about Monoclonius,‭ ‬though briefly going on the assumption that Monoclonius does actually represent a valid genus,‭ ‬then Monoclonius would have been a mid-sized centrosaurine ceratopsian dinosaur,‭ ‬perhaps most similar to Centrosaurus in form.
       In popular science and fiction Monoclonius was once one of the staple ceratopsian dinosaurs that would be included in works about dinosaurs,‭ ‬sometimes even rivalling Triceratops and Styracosaurus for popularity.‭ ‬The most iconic appearance of Monoclonius in recent times was in the‭ ‬1984‭ ‬classic short Prehistoric Beast,‭ ‬a go motion animation which featured an encounter between a Monoclonius and a Tyrannosaurus,‭ ‬and something that is well remembered by anyone who grew up in the‭ ‬1980s.

Further reading
-‭ ‬Descriptions of some vertebrate remains from the Fort Union Beds of Montana.‭ ‬-‭ ‬Proceedings of the Academy of Natural Sciences of Philadelphia‭ ‬28:‭ ‬248-261.‭ ‬-‭ ‬Edward Drinker Cope‭ ‬-‭ ‬1876.
-‭ ‬On Reptilian remains from the Dakota Beds of Colorado.‭ ‬-‭ ‬Paleontological Bulletin,‭ ‬26:‭ ‬193-197.‭ ‬-‭ ‬Edward Drinker Cope‭ ‬-‭ ‬1877.
-‭ ‬The horned Dinosauria of the Laramie.‭ ‬-‭ ‬American Naturalist,‭ ‬23:‭ ‬715-717.‭ ‬-‭ ‬Edward Drinker Cope‭ ‬-‭ ‬1889.
-‭ ‬New genera and species from the Belly River Series‭ (‬mid-Cretaceous‭)‬.‭ ‬-‭ ‬Geological Survey of Canada Contributions to Canadian Palaeontology‭ ‬3‭(‬2‭)‬:‭ ‬25-81.‭ ‬-‭ ‬Lawrence M.‭ ‬Lambe‭ ‬-‭ ‬1902.
-‭ ‬On the squamoso-parietal crest of the horned dinosaurs Centrosaurus apertus and Monoclonius canadensis from the Cretaceous of Alberta.‭ ‬-‭ ‬Transactions of the Royal Society of Canada,‭ ‬series‭ ‬2‭ ‬10‭(‬4‭)‬:‭ ‬1-9.‭ ‬Lawrence M.‭ ‬Lambe‭ ‬-‭ ‬1904.
-‭ ‬The Ceratopsia‭ ‬-‭ ‬Monographs of the United States Geological Survey‭ ‬49,‭ ‬198‭ ‬pages.‭ ‬-‭ ‬O.‭ ‬C.‭ ‬Marsh,‭ ‬J.‭ ‬B.‭ ‬Hatcher‭ & ‬R.‭ ‬S.‭ ‬Lull‭ ‬-‭ ‬1907.
-‭ ‬A complete skull of the horned dinosaur Monoclonius,‭ ‬from the Belly River of Alberta.‭ ‬-‭ ‬Bulletin of the American Museum of Natural History,‭ ‬33:‭ ‬549‭–‬558.‭ ‬-‭ ‬Barnum Brown‭ ‬-‭ ‬1914.
-‭ ‬On Eoceratops canadensis,‭ ‬gen.‭ ‬nov.,‭ ‬with remarks on other genera of Cretaceous horned dinosaurs.‭ ‬-‭ ‬Canada Geological Survey Museum Bulletin‭ ‬12,‭ ‬Geological Series‭ ‬24:‭ ‬1-49.‭ ‬-‭ ‬Lawrence M.‭ ‬lambe‭ ‬-‭ ‬1915.
-‭ ‬A complete skeleton of the horned dinosaur Monoclonius,‭ ‬and description of a second skeleton showing skin impressions.‭ ‬-‭ ‬Bulletin of the American Museum of Natural History,‭ ‬35:‭ ‬709‭–‬716.‭ ‬-‭ ‬Barnum Brown‭ ‬-‭ ‬1917.
-‭ ‬A revision of the Ceratopsia or horned dinosaurs.‭ ‬-‭ ‬Memoirs of the Peabody Museum of Natural History‭ ‬3‭(‬3‭)‬:‭ ‬1-175.‭ ‬-‭ ‬Richard S.‭ ‬Lull‭ ‬-‭ ‬1933.
-‭ ‬Monoclonius from southeastern Alberta compared with Centrosaurus.‭ ‬-‭ ‬Journal of Palaeontology,‭ ‬12‭(‬3‭)‬:‭ ‬284-286.‭ ‬-‭ ‬C.‭ ‬M.‭ ‬Sternberg‭ ‬-‭ ‬1938.
-‭ ‬The ceratopsian subfamily Chasmosaurinae:‭ ‬sexual dimorphism and systematics‭ ‬-‭ ‬T.‭ ‬M.‭ ‬Lehman‭ ‬-‭ ‬In.‭ ‬Dinosaur Systematics:‭ ‬Perspectives and Approaches pp211-229,‭ ‬Cambridge University Press‭ ‬-‭ ‬Kenneth Carpenter‭ & ‬Philip J.‭ ‬Currie‭ ‬-‭ ‬1990.
-‭ ‬On the status of the ceratopsids Monoclonius and Centrosaurus‭ ‬-‭ ‬P Dodson‭ ‬-‭ ‬In.‭ ‬Dinosaur Systematics:‭ ‬Perspectives and Approaches pp211-229,‭ ‬Cambridge University Press‭ ‬-‭ ‬Kenneth Carpenter‭ & ‬Philip J.‭ ‬Currie‭ ‬-‭ ‬1990.
-‭ ‬Why Monoclonius Cope Was Not Named for Its Horn:‭ ‬The Etymologies of Cope's Dinosaurs.‭ ‬-‭ ‬Journal of Vertebrate Paleontology‭ (‬Journal of Vertebrate Paleontology,‭ ‬Vol.‭ ‬12,‭ ‬No.‭ ‬3‭) ‬12‭ (‬3‭)‬:‭ ‬313‭–‬317.‭ ‬-‭ ‬B.‭ ‬S.‭ ‬Creisler‭ ‬-‭ ‬1992.
-‭ ‬Craniofacial ontogeny in centrosaurine dinosaurs‭ (‬Ornithischia:‭ ‬Ceratopsidae‭)‬:‭ ‬taxonomic and behavioral implications.‭ ‬-‭ ‬Zoological Journal of the Linnean Society,‭ ‬121:‭ ‬293‭–‬337.‭ ‬-‭ ‬S.‭ ‬D.‭ ‬Sampson,‭ ‬M.‭ ‬J.‭ ‬Ryan‭ & ‬D.‭ ‬H.‭ ‬Tanke‭ ‬-‭ ‬1997.
-‭ ‬A heterochronic analysis of enigmatic ceratopsids.‭ ‬-‭ ‬Journal of Vertebrate Paleontology,‭ ‬18‭(‬supplement‭)‬:‭ ‬83A.‭ ‬-‭ ‬A.‭ ‬R.‭ ‬Tumarkin‭ & ‬P.‭ ‬Dodson‭ ‬-‭ ‬1998.
-‭ ‬The status of the problematic taxon Monoclonius‭ (‬Ornithischia:‭ ‬Ceratopsidae‭) ‬and the recognition of adult-sized dinosaur taxa.‭ ‬-‭ ‬Geological Society of America Abstracts with Programs,‭ ‬38‭(‬4‭)‬:‭ ‬62.‭ ‬-‭ ‬Michael J.‭ ‬Ryan‭ ‬-‭ ‬2006.


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