 The first ceratopsian remains known to science were discovered during the U.S. Geological and Geographical Survey of the Territories led by the American geologist F.V. Hayden . Teeth discovered during an 1855 expedition to Montana were first assigned to hadrosaurids and included within the genus Trachodon . It was not until the early 20th century that some of these were recognized as ceratopsian teeth . During another of Hayden 's expeditions in 1872 , Fielding Bradford Meek found several giant bones protruding from a hillside in southwestern Wyoming . He alerted paleontologist Edward Drinker Cope , who led a dig to recover the partial skeleton . Cope recognized the remains as a dinosaur , but noted that even though the fossil lacked a skull , it was different from any type of dinosaur then known . He named the new species Agathaumas sylvestris , meaning " marvellous forest @-@ dweller " . Soon after , Cope named two more dinosaurs that would eventually come to be recognized as ceratopsids : Polyonax and Monoclonius . Monoclonius was notable for the number of disassociated remains found , including the first evidence of ceratopsid horns and frills . Several Monoclonius fossils were found by Cope , assisted by Charles Hazelius Sternberg , in the summer of 1876 near the Judith River in Chouteau County , Montana . Since the ceratopsians had not been recognised yet as a distinctive group , Cope was uncertain about much of the fossil material , not recognizing the nasal horn core , nor the brow horns , as part of a fossil horn . The frill bone was interpreted as a part of the breastbone . 
 The first ceratopsian <a href='uninflect' title='1'><mark>remains</mark></a> known to science <a href='uninflect' title='2'><mark>were</mark></a> discovered during the U.S. Geological and Geographical Survey of the Territories led by the American geologist F.V. Hayden . Teeth discovered during an 1855 expedition to Montana <a href='uninflect' title='3'><mark>were</mark></a> first assigned to hadrosaurids and included within the genus Trachodon . It <a href='negative_concord' title='4'><mark>was</mark></a> <a href='negative_concord' title='5'><mark>not</mark></a>until the early 20th century that some of these <a href='uninflect' title='6'><mark>were</mark></a> recognized as ceratopsian teeth . During another of Hayden <a href='null_genetive' title='7'><mark>'s</mark></a>expeditions in 1872 , Fielding Bradford Meek found several giant bones protruding from a hillside in southwestern Wyoming . He alerted paleontologist Edward Drinker Cope , <a href='null_relcl' title='8'><mark>who</mark></a>led a dig to recover the partial skeleton . Cope recognized the remains as a dinosaur , but noted that even though the fossil lacked a skull , it was different from any type of dinosaur then known . He named the new species Agathaumas sylvestris , meaning " marvellous forest @-@ dweller " . Soon after , Cope named two more dinosaurs <a href='null_relcl' title='9'><mark>that</mark></a>would eventually come to be recognized as ceratopsids : Polyonax and Monoclonius . Monoclonius was notable for the number of disassociated <a href='uninflect' title='10'><mark>remains</mark></a> found , including the first evidence of ceratopsid horns and frills . Several Monoclonius fossils <a href='uninflect' title='11'><mark>were</mark></a> found by Cope , assisted by Charles Hazelius Sternberg , in the summer of 1876 near the Judith River in Chouteau County , Montana . Since the ceratopsians <a href='been_done' title='12'><mark>had</mark></a> not been recognised yet as a distinctive group , Cope was uncertain about much of the fossil material , not recognizing the nasal horn core , nor the brow horns , as part of a fossil horn . The frill bone was interpreted as a part of the breastbone . 
The first ceratopsian remain known to science was discovered durin the U.S. Geological and Geographical Survey of da Territories led by the American geologist F.V. bj . teef discovered ddurinan 1855 expedition to Montana was first assigned to hadrosaurids and included within tdagenus Trachodon . It ain't until the early 20th century that some of these was recognized as ceratopsian teeth . During another of Haydbjpeditions in 1872 , Fielding Bradford Meek found several bigass bones protruding from a hillside in southwestern Wyoming . He alerted paleontologist Edward Drinker Cope , led a dig to recover the partial skeleton . Cope recognized the remains as a dinosaur , but noted that even tho thdaossil lacked a skull , it was diffrent from any type of dinosaur then known . He named the new species Agathaumas sylvestris , meaning " marvellous forest @-@ dweller " . Soon after , Cope named two more dinosaurs would eventually come to b recognized as ceratopsids : Polyonax and Monoclonius . Monoclonius was notable for thedamber of disassociated remain found , including the first evidence of ceratopsid horns and frills . Several Monoclonius fossils was found by Cope , assisted by Charles Hazelius Sternberg , in the damer of 1876 near the Judith River in Chouteau County , Montana . Since the ceratopsians done not been recognised yet as a distinctive group , Cope was uncertain abt much of the fossil material , not recognizing the nasal horn core , nor the brow horns , as part of a fossil horn . The frill bone was interpreted as a part of the bdastbone .