Megacerops

Apr 23, 2026 - 16:08
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Megacerops

Typo fixing, replaced: mongraph → monograph

← Previous revision Revision as of 10:36, 23 April 2026
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[[File:Cambridge Natural History Mammalia Fig 137.jpg|thumb|Three ''M. coloradensis'' skulls, showing the variability of horn shape and size. By [[Henry Fairfield Osborn|Osborn]]'s classification scheme, these represent three different species.]]By the time of Osborn's monograph, at least 47 species of Chadronian brontotheres had been named, many based on poor and fragmentary fossils. There was a general consensus throughout the 20th century that the brontotheres were highly [[Lumpers and splitters#Biology|oversplit]], divided into far too many species. Taxonomic problems were compounded by confusion around the type specimens and names of several of the species. Marsh incorrectly argued in 1873 that ''Menodus'' was [[preoccupied]] by the reptile ''Menodon'' (''=[[Nothosaurus]]''). In several publications, both Leidy and Osborn sometimes confused USNM 113 (type specimen of ''Titanotherium'') with USNM 21820 (type specimen of ''Menodus''). Osborn incorrectly believed that USNM 21820 had been destroyed in the [[St. Louis Fire of 1849]] and proposed designating a brontothere skull in the [[American Museum of Natural History]], AMNH 505, as a [[neotype]] specimen.
[[File:Cambridge Natural History Mammalia Fig 137.jpg|thumb|Three ''M. coloradensis'' skulls, showing the variability of horn shape and size. By [[Henry Fairfield Osborn|Osborn]]'s classification scheme, these represent three different species.]]By the time of Osborn's monograph, at least 47 species of Chadronian brontotheres had been named, many based on poor and fragmentary fossils. There was a general consensus throughout the 20th century that the brontotheres were highly [[Lumpers and splitters#Biology|oversplit]], divided into far too many species. Taxonomic problems were compounded by confusion around the type specimens and names of several of the species. Marsh incorrectly argued in 1873 that ''Menodus'' was [[preoccupied]] by the reptile ''Menodon'' (''=[[Nothosaurus]]''). In several publications, both Leidy and Osborn sometimes confused USNM 113 (type specimen of ''Titanotherium'') with USNM 21820 (type specimen of ''Menodus''). Osborn incorrectly believed that USNM 21820 had been destroyed in the [[St. Louis Fire of 1849]] and proposed designating a brontothere skull in the [[American Museum of Natural History]], AMNH 505, as a [[neotype]] specimen.


Chadronian brontotheres are very similar in most features of the skeleton. Clear differences between specimens are for the most part seen only in the shape, orientation and size of horns, nasal bones and [[zygomatic arch]]es. Before his 1929 monograph, Osborn considered the possibility that all Chadronian brontotheres belonged to a single genus, for which he preferred the name ''Titanotherium''. In the mongraph, Osborn nevertheless recognized 37 of the up until then named species as valid. Almost every well-preserved skull was designated as a separate species. Osborn attributed the variation seen in the fossil material to both individual variation due to sex and age, and to species-level differences, but did not demonstrate how a differing feature could be determined to be due to one factor or another.
Chadronian brontotheres are very similar in most features of the skeleton. Clear differences between specimens are for the most part seen only in the shape, orientation and size of horns, nasal bones and [[zygomatic arch]]es. Before his 1929 monograph, Osborn considered the possibility that all Chadronian brontotheres belonged to a single genus, for which he preferred the name ''Titanotherium''. In the monograph, Osborn nevertheless recognized 37 of the up until then named species as valid. Almost every well-preserved skull was designated as a separate species. Osborn attributed the variation seen in the fossil material to both individual variation due to sex and age, and to species-level differences, but did not demonstrate how a differing feature could be determined to be due to one factor or another.


Osborn's conclusions faced criticism by other paleontologists. In 1941, [[William Berryman Scott]] stated that "it is hardly worthwhile even to list the species; that 37 species could not have co-existed within the relatively brief space of the Chadron, is obvious; how many did exist and what names should be given to them, are insoluable problems". Scott further stated that "the probably great effects of sex and age and fluctuating variability have not been sufficiently evaluated". Despite criticism, further revisions of brontothere material were not attempted for most of the 20th century due to the daunting size of Osborn's monograph and the sheer number of fossil specimens known, many of which were yet to be sufficiently prepared.
Osborn's conclusions faced criticism by other paleontologists. In 1941, [[William Berryman Scott]] stated that "it is hardly worthwhile even to list the species; that 37 species could not have co-existed within the relatively brief space of the Chadron, is obvious; how many did exist and what names should be given to them, are insoluable problems". Scott further stated that "the probably great effects of sex and age and fluctuating variability have not been sufficiently evaluated". Despite criticism, further revisions of brontothere material were not attempted for most of the 20th century due to the daunting size of Osborn's monograph and the sheer number of fossil specimens known, many of which were yet to be sufficiently prepared.
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