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Megacerops coloradensis

Mammalia - Perissodactyla - Brontotheriidae

Taxonomy

Megacerops coloradensis was named by Leidy (1870) [genotype; recognized by Osborn 1929, Mader 1989, Mader 1998].

It was recombined as Megaceratops coloradoensis by Cope (1873); it was recombined as Menodus coloradensis by Scott and Osborn (1887); it was recombined as Titanotherium coloradense by Osborn (1896).

Synonyms

Brontotherium gigas was named by Marsh (1873) [genotype]. It is the type species of Brontotherium.

It was recombined as Titanotherium gigas by Osborn (1896); it was recombined as Titanotherium gigas by Osborn (1896); it was considered a nomen dubium by Mader (1989) and Mader (1998); it was synonymized subjectively with Megacerops coloradensis by Mihlbachler (2008).
Brontotherium hatcheri was named by Osborn (1908) [accepted by Osborn 1929]. Its type locality is Indian Creek (Middle Titanotherium Beds), which is in a Chadronian terrestrial horizon in the Chadron Formation of South Dakota.

It was recombined as Megacerops hatcheri by Mader (1989) and Mader (1998); it was synonymized subjectively with Megacerops coloradensis by Mihlbachler (2008).
Brontotherium ingens was named by Marsh (1874). It is a 3D body fossil.

It was synonymized subjectively with Symborodon trigonoceras by Cope (1874); it was synonymized subjectively with Menodus coloradensis by Scott and Osborn (1887); it was recombined as Titanotherium ingens by Osborn (1896), Hay (1902) and Osborn (1902); it was synonymized subjectively with Menodus giganteus by Osborn (1929); it was considered a nomen dubium by Mader (1989) and Mader (1998); it was synonymized subjectively with Megacerops coloradensis by Mihlbachler (2008).
Brontotherium leidyi was named by Osborn (1902) [accepted by Osborn 1929]. Its type specimen is USNM 4249, a skull, and it is a 3D body fossil. Its type locality is Bear Creek (Lower Titanotherium Beds), which is in a Chadronian terrestrial horizon in the Chadron Formation of South Dakota.

It was considered a nomen dubium by Mader (1989) and Mader (1998); it was synonymized subjectively with Megacerops coloradensis by Mihlbachler (2008).
Menodus platyceras was named by Scott and Osborn (1887). It is a 3D body fossil.

It was recombined as Titanotherium platyceras by Osborn (1896); it was recombined as Brontotherium platyceras by Hay (1902), Osborn (1902) and Osborn (1929); it was recombined as Megacerops platyceras by Mader and Alexander (1995) and Mader (1998); it was synonymized subjectively with Megacerops coloradensis by Mihlbachler (2008).
Titanotherium ramosum was named by Osborn (1896). Its type specimen is AMNH 1447 and is a 3D body fossil.

It was recombined as Brontotherium ramosum by Hay (1902), Osborn (1902) and Osborn (1929); it was synonymized subjectively with Megacerops platyceras by Mader and Alexander (1995).

Synonymy list

Year	Name and author
1870	Megacerops coloradensis Leidy p. 2
1873	Megaceratops coloradoensis Cope p. 29
1873	Megacerops coloradensis Leidy p. 239
1873	Brontotherium ingens Marsh
1873	Brontotherium gigas Marsh p. 486
1874	Brontotherium ingens Marsh pp. 85 - 86 figs. Plates 1 and 2
1887	Menodus coloradensis Scott and Osborn p. 158
1887	Menodus platyceras Scott and Osborn p. 160
1896	Titanotherium coloradense Osborn p. 175 figs. Plate III
1896	Titanotherium gigas Osborn p. 175
1896	Titanotherium ingens Osborn p. 182
1896	Titanotherium platyceras Osborn p. 185 figs. Plate IV
1896	Titanotherium ramosum Osborn p. 194 figs. Plate IV
1902	Megacerops coloradensis Hay p. 633
1902	Brontotherium gigas Hay p. 635
1902	Brontotherium platyceras Hay p. 635
1902	Brontotherium ramosum Hay p. 635
1902	Titanotherium ingens Hay p. 636
1902	Brontotherium leidyi Osborn
1902	Brontotherium platyceras Osborn
1902	Brontotherium ramosum Osborn
1902	Titanotherium ingens Osborn
1902	Brontotherium leidyi Osborn p. 105 fig. 9
1908	Brontotherium hatcheri Osborn
1929	Brontotherium platyceras Osborn
1929	Brontotherium ramosum Osborn
1989	Megacerops hatcheri Mader
1995	Megacerops platyceras Mader and Alexander
1998	Megacerops hatcheri Mader
1998	Megacerops platyceras Mader
2004	Megacerops coloradensis Mihlbachler et al. p. 134
2008	Megacerops coloradensis Mihlbachler p. 414

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
subclass	Synapsida
—	Therapsida	()
infraorder	Cynodontia	()
—	Mammaliamorpha
—	Mammaliaformes

Rank	Name	Author
class	Mammalia
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Boreoeutheria
—	Laurasiatheria
—	Scrotifera
—	Euungulata
—	Panperissodactyla
superorder	Perissodactylamorpha
order	Perissodactyla	()
family	Brontotheriidae	()
subfamily	Brontotheriinae	Marsh 1873
tribe	Brontotheriini	Marsh 1873
subtribe	Brontotheriina	Marsh 1873
—	Brontotheriita	Marsh 1873
genus	Megacerops
species	coloradensis

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

†Megacerops coloradensis Leidy 1870

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Invalid names: Brontotherium gigas Marsh 1873 [synonym], Brontotherium hatcheri Osborn 1908 [synonym], Brontotherium ingens Marsh 1874 [synonym], Brontotherium leidyi Osborn 1902 [synonym], Brontotherium platyceras Scott and Osborn 1887 [synonym]

Diagnosis

Reference	Diagnosis
W. B. Scott and H. F. Osborn 1887 (Menodus platyceras)	The dentition is unknown. Nasal bones extremely short and obtuse, as in M. dolichoceius and M. acer. The inner contour of the uorns is concave ; they are greatly flattened antero-posteriorly with a ridge-like outer margin, and connected by a well-raised median ridge. The posterior face is nearly plane, the anterior is convex, so that the section of the horn is plano-convex from base to tip. In side view the horns completely overhang the nasals, and are slightly recurved. The long axis of the horn section is directly transverse.
H. F. Osborn 1896 (Titanotherium ramosum)	Horns placed above symphysis, greatly expanded at the summits, section plano-convex; a strong 'connecting crest,' Nasals extremely short. Zygomatic arches expanded into two wide flat plates. Incisors and canines unknown. Premolars with reduced external cingula.