Brontotheriidae 998918 226074947 2008-07-16T18:42:14Z Leptictidium 358207 {{Taxobox | name = Brontotheres | fossil_range = [[Eocene]] | image = Brontotherium hatcheri.jpg | image_width = 250px | image_caption = ''Brontotherium hatcheri'' skeleton at the <br />[[National Museum of Natural History]], [[Washington, DC]] | regnum = [[Animal]]ia | phylum = [[Chordata]] | classis = [[Mammal]]ia | ordo = [[Perissodactyla]] | familia = †'''Brontotheriidae''' | familia_authority = [[Othniel Charles Marsh|Marsh]], [[1873]] | subdivision_ranks = Genera | subdivision = <center>See Text</center> }} '''Brontotheriidae''', also called '''Titanotheriidae''', is a [[family (biology)|family]] of [[extinct]] [[mammal]]s belonging to the order [[Perissodactyla]], the order that includes [[horse]]s, [[Rhinoceros|rhino]]s, and [[tapir]]s. Although '''brontotheres''' are probably most closely related to horses, superficially they looked rather like [[rhinoceros]]es, although they were not true rhinos. They lived around 56-34 million years ago, from the early to late [[Eocene]]. ==Characteristics and Evolution== Brontotheres retain four toes on their front feet and three toes on their hind feet. Their teeth are adapted to shearing (cutting) relatively nonabrasive vegetation. Their [[molars]] have a characteristic W-shaped [[ectoloph]] (outer shearing blade). The evolutionary history of this group is well known, due to an excellent fossil record in [[North America]].[http://www.keltationsart.com/Titanotherium.htm] The earliest brontotheres, such as ''[[Eotitanops]]'', were rather small, no more than a meter in height, and were hornless. Later brontotheres evolved massive body sizes, although some small species, such as ''[[Nanotitanops]]'' did persist through the Eocene. Some genera, such as ''[[Dolichorhinus]]'', [[Evolution|evolved]] highly elongate skulls. Later brontotheres were massive in size, up to 2.5 m in height, and had evolved bizarre hornlike appendages. For instance the [[North America]]n brontothere ''[[Megacerops]]'' evolved large [[sexual dimorphism|sexually dimorphic]] paired horns above their noses. The sexually dimorphic horns suggest that brontotheres were highly gregarious (social) and males may have performed some sort of head clashing behavior in competition for mates. However, unlike rhinos, the horns of brontotheres are composed of bone, the [[frontal bone]] and [[nasal bone]], and were placed side-to-side rather than front-to-back. Brontotheres probably became extinct due to an inability to adapt to drier conditions and tougher vegetation (such as [[grass]]es) that spread during the Oligocene.[http://www.keltationsart.com/Titanotherium.htm] ==Classification of Brontotheres== Two classification systems for the Brontotheriidae are presented below. The first contains 43 genera and 8 subfamilies and although it is based on a recent publication (McKenna and Bell, 1997), it summarizes research that was conducted before 1920 and is badly outdated. The second classification is based on very recent research (Mihlbachler et al., 2004a, 2004b; Mihlbachler, 2005). It indicates that many of the previous subfamily names are invalid. Also several recently discovered brontotheres are included in the newer classification. Note that although ''[[Lambdotherium]]'' and ''[[Xenicohippus]]'' were previously included in the Brontotheriidae, they are no longer considered to be members of this family. ''Lambdotherium'', though excluded, may be the closest known relative to brontotheres. ''Xenicohippus'' is now thought to be an early member of the horse family, [[Equidae]]. {| class="wikitable" |- ! width="50%"|Old Classification (summarized by [[Malcolm McKenna|McKenna]] and Bell, [[1997]]) !New classification (Mihlbachler et al., 2004a, 2004b; Mihlbachler, [[2005]]) |- | valign="top"| *'''Family Brontotheriidae''' **''[[Pakotitanops]]'' ''[[incertae sedis]]'', from [[Pakistan]] **''[[Nanotitanops]]'' ''[[incertae sedis]]'', from [[Asia]] ***Subfamily Lambdotheriinae ****''[[Lambdotherium]]'', from North America ****''[[Xenicohippus]]'', from North America ***Subfamily Palaeosyopinae ****''[[Palaeosyops]]'' (including ''Eotitanops''), from North America, 0.5 m tall ****''[[Mulkrajanops]]'', from [[Pakistan]], 1.25 m tall ***Subfamily Dolichorhininae ****''[[Metarhinus]]'', from North America, 1 m tall ****''[[Sphenocoelus]]'', from North America, 1.25 m tall ****''[[Mesatirhinus]]'', from North America, 1 m tall ***Subfamily Brontotheriinae ****''[[Duchesneodus]]'', from North America ****''[[Brontotherium]]'', from North America ****''[[Megacerops]]'', from North America, 2.5 m tall ***Subfamily Embolotheriinae ****''[[Titanodectes]]'', from Asia ****''[[Embolotherium]]'', from [[Mongolia]], 2.5 m tall ****''[[Protembolotherium]]'', from Outer Mongolia, 2 m tall ***Subfamily Brontopinae ****''[[Brachydiastematherium]]'', from [[Eastern Europe]], 2 m tall ****''[[Pachytitan]]'', from Inner Mongolia, 2 m tall ****''[[Dianotitan]]'', from China, 2 m tall ****''[[Gnathotitan]]'', from Inner Mongolia, 2.5 m tall ****''[[Microtitan]]'', from Inner Mongolia, 0.75 m tall ****''[[Epimanteoceras]]'', from Inner Mongolia, 2 m tall ****''[[Protitan]]'', from Inner Mongolia, 2 m tall ****''[[Rhinotitan]]'', from Inner Mongolia, 2.5 m tall ****''[[Metatitan]]'', from Mongolia, 1.5 m tall ****''[[Protitanotherium]]'', from North America, 2 m tall ****''[[Parabrontops]]'', from Mongolia, 2 m tall ****''[[Oreinotherium]]'', from North America ****''[[Brontops]]'', from North America ****''[[Protitanops]]'', from North America, 2 m tall ****''[[Pygmaetitan]]'', from China, 0.5 m tall ***Subfamily Telmatheriinae ****''[[Acrotitan]]'', from Inner Mongolia, 0.3 m tall ****''[[Desmatotitan]]'', from Inner Mongolia, 1.25 m tall ****''[[Arctotitan]]'', from China ****''[[Hyotitan]]'', from Inner Mongolia, 2.2 m tall ****''[[Sthenodectes]]'', from North America, 1.25 m tall ****''[[Telmatherium]]'' (including ''Metatelmatherium''), from North America and Inner Mongolia, 1.5 m tall ****''[[Sivatitanops]]'', from Asia and Europe ***Subfamily Menodontinae ****''[[Diplacodon]]'', from North America, 2 m tall ****''[[Eotitanotherium]]'', from North America ****''[[Notiotitanops]]'', from North America, 2 m tall ****''[[Menodus]]'', from Europe and North America ****''[[Ateleodon]]'', from North America | valign="top"| *'''Family Brontotheriidae''' **''[[Pakotitanops]]'' ''[[incertae sedis]]'', from [[Pakistan]] **''[[Mulkrajanops]]'' ''[[incertae sedis]]'', from [[Pakistan]], 1.25 m tall **''[[Eotitanops]]'', from North America, 0.5 m tall **''[[Palaeosyops]]'', from North America, 1 m tall **Subfamily Brontotheriinae ***''[[Bunobrontops]]'', from [[Asia]] ***''[[Mesatirhinus]]'', from North America, 1 m tall ***''[[Dolichorhinus]]'', from North America, 1.25 m tall ***''[[Sphenocoelus]]'', from North America, 1.25 m tall ***''[[Desmatotitan]]'', from Inner Mongolia, 1.25 m tall ***''[[Fossendorhinus]]'', from North America ***''[[Metarhinus]]'', from North America, 1 m tall ***''[[Microtitan]]'', from Inner Mongolia, 0.75 m tall ***''[[Sthenodectes]]'', from North America, 1.25 m tall ***''[[Telmatherium]]'', from North America, 1.25 m tall ***''[[Metatelmatherium]]'', from North America and Inner Mongolia, 1.25 m tall ***''[[Epimanteoceras]]'', from Inner Mongolia, 2 m tall ***''[[Hyotitan]]'' ''[[incertae sedis]]'', from Inner Mongolia, 2.2 m tall ***''[[Nanotitanops]]'' ''[[incertae sedis]]'', from [[Asia]] ***''[[Pygmaetitan]]'' ''[[incertae sedis]]'', from China, 0.5 m tall ***''[[Acrotitan]]'' ''[[incertae sedis]]'', from Inner Mongolia, 0.3 m tall ***''[[Arctotitan]]'' ''[[incertae sedis]]'', from China ***''[[Qufutitan]]'' ''[[incertae sedis]]'', from China ***Tribe Brontotheriini ****''[[Protitan]]'', from Inner Mongolia, 2 m tall ****''[[Protitanotherium]]'', from North America, 2 m tall ****''[[Rhinotitan]]'', from Inner Mongolia, 2.5 m tall ****''[[Diplacodon]]'' (including ''Eotitanotherium''), from North America, 2 m tall ****''[[Pachytitan]]'', from Inner Mongolia, 2 m tall ****''[[Brachydiastematherium]]'', from [[Eastern Europe]], 2 m tall ****''[[Sivatitanops]]'', from Asia and Europe ****Subtribe Embolotheriina *****''[[Gnathotitan]]'', from Inner Mongolia, 2.5 m tall *****''[[Aktautitan]]'', from Kazakhstan, 2.5 m tall *****''[[Metatitan]]'', from Mongolia, 1.5 m tall *****''[[Nasamplus]]'', from Inner Mongolia *****''[[Protembolotherium]]'', from Outer Mongolia, 2 m tall *****''[[Embolotherium]]'' (including ''Titanodectes''), from [[Mongolia]], 2.5 m tall ****Subtribe Brontotheriina *****''[[Parabrontops]]'', from Mongolia, 2 m tall *****''[[Protitanops]]'', from North America, 2 m tall *****''[[Notiotitanops]]'', from North America, 2 m tall *****''[[Dianotitan]]'', from China, 2 m tall *****''[[Duchesneodus]]'', from North America *****''[[Megacerops]]'' (including ''Menodus'', ''Brontotherium'', ''Brontops'', ''Menops'', ''Ateleodon'', and ''Oreinotherium''), from North America, 2.5 m tall |} ==External links== *[http://www.fmnh.helsinki.fi/users/haaramo/metazoa/deuterostoma/chordata/synapsida/eutheria/Perissodactyla/Brontotheroidea.htm Brontotheroidea] at Mikko's Phylogeny Archive ==References== *McKenna, M. C, and S. K. Bell. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. *Mihlbachler, M.C. 2004. Phylogenetic Systematics of the Brontotheriidae (Mammalia, Perissodactyla). Ph.D. Dissertation, Columbia University. 757 pp. *Mihlbachler, M.C. , S.G. Lucas, and R.J, Emry. 2004a. The holotype specimen of Menodus giganteus, and the “insoluble” problem of Chadronian brontothere taxonomy. In S.G. Lucas, K. Zeigler, and P. E. Kondrashov (eds.), Paleogene Mammals. Bulletin of the New Mexico Museum of Natural History 26: 129-136. *Mihlbachler, M.C., S.G. Lucas, R.J. Emry, and B. Bayshashov. 2004b. A new brontothere (Brontotheriidae, Perissodactla, Mammalia) from the Eocene of the Ily Basin of Kazakhstan and a phylogeny of Asian "horned" brontotheres. American Museum Novitates 3439: 1-43. [[Category:Brontotheres| ]] [[Category:Eocene extinctions]] [[ca:Brontotèrid]] [[es:Brontotheriidae]] [[hu:Brontotheriidae]] [[nl:Brontotheriidae]] [[pt:Brontotheriidae]] [[zh:雷獸]]