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Proterotheriidae is an
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
family of litoptern
Litopterna (from "smooth heel") is an extinct order of South American native ungulates that lived from the Paleocene to the Pleistocene-Holocene around 62.5 million to 12,000 years ago (or possibly as late as 3,500 years ago), and were also pres ...
ungulates known from the Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
-Late Pleistocene
The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...
of South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. Members of the group were small-medium sized cursorial
A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often ...
herbivores
A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...
with brachydont teeth
A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
, with their toes
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plantigrade''; ...
showing progressive reduction, with later members of the group bearing weight on a single large toe similar to living horses
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 milli ...
.
Description
Two subfamilies and 18 genera of Proterotheriidae are known. All forms were small or medium-sized. Typical is a reduction of the number of toes and brachydont or mesodont teeth. The family is recorded since the late Palaeocene. Various fossils are known from many parts of the South American continent. The diversity decreased in the Miocene to Pliocene and it has been assumed for a long time that they entirely disappeared in the late Pliocene. However, fossils found in Argentina, Brazil and Uruguay show that one member of the group, ''Neolicaphrium
''Neolicaphrium'' is an extinct genus of ungulate mammal belonging to the extinct order Litopterna. This animal lived from the Late Pliocene (Chapadmalalan) to the Late Pleistocene (Lujanian) in southern South America, being the last survivor of ...
recens'' survived into the Late Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
.
Better known genera of the family include ''Diadiaphorus
''Diadiaphorus'' is an extinct genus of litoptern mammal from the Miocene of Argentina ( Ituzaingó, Pinturas, Chiquimil and Santa Cruz Formations) and Bolivia ( Nazareno Formation), South America.
Description
''Diadiaphorus'' closely rese ...
'' and ''Thoatherium
''Thoatherium'' (meaning "active swift-beast") is an extinct genus of litoptern mammals from the Early Miocene of Argentina. Fossils of the genus have been found in the Santa Cruz Formation in Argentina.
Taxonomy
* Proterotheriidae ** ''Anisolambda
''Anisolambda'' is an extinct genus of litoptern. It lived from the Late Paleocene to the Middle Eocene in what is now Argentina.
Description
This animal is mostly known from fossils of its maxilla, mandible and teeth, and it is therefore diff ...
''
** ''Anisolophus
''Anisolophus'' is an extinct genus of proterotheriid from the Early to Middle Miocene of Argentina. The genus was named by Burmeister in 1885 to accommodate the species ''Anchitherium australe'', which they had named earlier in 1879. Soria then ...
''
** ''Brachytherium
''Brachytherium'' is an extinct genus of proterotheriid mammal from the Late Miocene to Late Pliocene of Argentina. It is represented by the type and only species ''B. cuspidatum'', a taxon named in 1883 by Ameghino for a partial mandible with t ...
''
** ''Diadiaphorus
''Diadiaphorus'' is an extinct genus of litoptern mammal from the Miocene of Argentina ( Ituzaingó, Pinturas, Chiquimil and Santa Cruz Formations) and Bolivia ( Nazareno Formation), South America.
Description
''Diadiaphorus'' closely rese ...
''
** ''Diplasiotherium
''Diplasiotherium'' is an extinct genus of litoptern belonging to the family Proterotheriidae, that lived between the late Miocene and the early Pliocene (in the SALMAs Huayquerian and Montehermosan).Villafañé et al., 2006, p.161 The fossils ...
''
** ''Eoauchenia
''Eoauchenia'' is a genus of extinct proterotheriid from the Late Miocene and Early Pliocene of Argentina. The genus was named by Ameghino in 1887 for the type species ''E. primitiva'', which was originally known from the early Pliocene Monte H ...
''
** '' Eolicaphrium''
** '' Epecuenia''
** ''Epitherium
''Epitherium'' is an extinct genus of Litopterna, who belonged to the family Proterotheriidae. It lived during the Pliocene in South America. The fossils of this herbivorous ungulate were found in Argentina
Argentina, officially the Arg ...
''
** ''Guilielmofloweria
''Guilielmofloweria'' is an extinct genus of proterotheriidae, proterotheriid litopterna, litoptern that lived from the Middle to Late Eocene of what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Taxonomy
' ...
''
** '' Heteroglyphis''
** ''Lambdaconus
''Lambdaconus'' is a genus of proterotheriidae, proterotheriid from the Oligocene, Late Oligocene to Early Miocene of Argentina. The type species is ''L. suinus'', named in 1897 by Ameghino, with referred species including ''L. lacerum'', named a ...
''
** '' Lambdaconops''
** ''Mesolicaphrium
''Mesolicaphrium'' is a genus of extinct litoptern from the late middle Miocene of southern Colombia. It was named in 2020 by Andrew McGrath and colleagues, for the species previously classified as '' Prolicaphrium sanalfonensis'' from the La Vi ...
''
** ''Neobrachytherium
''Neobrachytherium'' is an extinct genus of proterotheriid mammal from the Late Miocene of Argentina and Uruguay. It is represented by multiple species, including the type ''N. intermedium'', originally named in 1891 by Moreno and Mercerat as a ...
''
** ''Neodolodus
''Neodolodus'' is a genus of extinct litoptern from the late middle Miocene of southern Colombia. It was named in 1986 by Hoffstetter and Soria, for the species ''Neodolodus colombianus'' from the Castilletes Formation and the La Victoria and ...
''
** ''Neolicaphrium
''Neolicaphrium'' is an extinct genus of ungulate mammal belonging to the extinct order Litopterna. This animal lived from the Late Pliocene (Chapadmalalan) to the Late Pleistocene (Lujanian) in southern South America, being the last survivor of ...
''
** ''Olisanophus
''Olisanophus'' is a genus of extinct litoptern from the late middle Miocene of southern Bolivia. It was named in 2020 by Andrew McGrath and colleagues, for two distinct species from the same deposits of an unnamed formation of the Honda Group. ...
''
** ''Paramacrauchenia
''Paramacrauchenia'' is an extinct genus of Proterotheriidae, proterotheriid litopterns from the Early Miocene of what is now Argentina and Chile. Its fossils have been found in the Sarmiento Formation, Sarmiento and Santa Cruz Formation, Argentin ...
''
** '' Paranisolambda''
** ''Picturotherium
''Picturotherium'' is a genus of extinct proterotheriid from the middle Miocene of Santa Cruz, Argentina. The genus is known from the type and only species ''P. migueli'', named in 2005 by Alejandro Kramarz and Mariano Bond for individual teeth ...
''
** ''Prolicaphrium
''Prolicaphrium'' is an extinct genus of proterotheriid litoptern that lived during the Early Miocene, in what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Description
This animal may have been vaguely si ...
''
** '' Promylophis''
** ''Proterotherium
''Proterotherium'' (meaning "first beast") is an extinct genus of litoptern mammal of the family Proterotheriidae that lived during the Late Miocene of Argentina
Argentina, officially the Argentine Republic, is a country in the southern ...
''
** ''Protheosodon
''Protheosodon'' is an extinct genus of proterotheriid litoptern. It lived from the Late Oligocene to the Early Miocene in what is now Argentina and Colombia.
Description
It was a medium-sized animal, smaller than the extant vicuña. The lowe ...
''
** ''Pseudobrachytherium
''Pseudobrachytherium'' is an extinct genus of proterotheriid from the Late Miocene of Uruguay. It is only known from the type species ''P. breve'', named in 2020 by Corona and colleagues for an almost complete skull found in the greenish pelite ...
''
** ''Tetramerorhinus
''Tetramerorhinus'' is an extinct genus of proterotheriid litoptern that lived during the Early and Middle Miocene in what is now Argentina and Peru.
Description
This animal resembled a small horse, with slender, elongated legs. The body was a ...
''
** ''Thoatherium
''Thoatherium'' (meaning "active swift-beast") is an extinct genus of litoptern mammals from the Early Miocene of Argentina. Fossils of the genus have been found in the Santa Cruz Formation in Argentina.Thoatheriopsis''
** '' Villarroelia''
** ''
Uruguayodon
''Uruguayodon'' is an extinct genus of proterotheriid from the middle Pleistocene of Uruguay. It is known from the type and only species ''U. alius'', named by Corona and colleagues in 2019 for dentaries and a partial postcrania from the Raigón ...
''
** ''Wainka
''Wainka'' is an extinct genus of South American mammal, belonging to the order Litopterna. It lived during the Middle Paleocene.
Description
This animal is only known for a few teeth. The upper molars were almost triangular in shape, elongated, ...
''
** ''Xesmodon
''Xesmodon'' is an extinct genus of mammal. It lived from the Middle to the Late Eocene, in what is today South America.
Taxonomy
''Xesmodon'' was named by Carlos Berg in 1899. Its type species is ''Xesmodon langi'', and a second species, ''Xes ...
''
** Megadolodinae
*** ''Bounodus
''Bounodus'' is an extinct genus of ungulates native from South America, belonging to the order Litopterna. Its remains were found in Miocene rocks from the Urumaco Formation of northern Venezuela. The genus is only known from its holotype, AMU-C ...
''
*** ''Megadolodus
''Megadolodus'' is an extinct genus of proterotheriid litopterns.
History
The first fossils of ''Megadolodus'' were uncovered from the Villavieja Formation, in the fossil locality La Venta, in what is today Colombia, in terrains dated from th ...
''
** Indaleciidae
*** '' Adiantoides''
*** '' Indalecia''
Proterotheriidae is traditionally considered to include two subfamilies, Anisolambdinae and Proterotheriinae. Anisolambdinae (also called Anisolambdidae in some studies) was proposed to unite the primitive and earlier forms ''Anisolambda
''Anisolambda'' is an extinct genus of litoptern. It lived from the Late Paleocene to the Middle Eocene in what is now Argentina.
Description
This animal is mostly known from fossils of its maxilla, mandible and teeth, and it is therefore diff ...
'', '' Eolicaphrium'', '' Paranisolambda'', ''Protheosodon
''Protheosodon'' is an extinct genus of proterotheriid litoptern. It lived from the Late Oligocene to the Early Miocene in what is now Argentina and Colombia.
Description
It was a medium-sized animal, smaller than the extant vicuña. The lowe ...
'', ''Guilielmofloweria
''Guilielmofloweria'' is an extinct genus of proterotheriidae, proterotheriid litopterna, litoptern that lived from the Middle to Late Eocene of what is now Argentina. Fossils have been found in the Sarmiento Formation of Argentina.
Taxonomy
' ...
'', '' Heteroglyphis'', '' Lambdaconops'', ''Wainka
''Wainka'' is an extinct genus of South American mammal, belonging to the order Litopterna. It lived during the Middle Paleocene.
Description
This animal is only known for a few teeth. The upper molars were almost triangular in shape, elongated, ...
'' and ''Xesmodon
''Xesmodon'' is an extinct genus of mammal. It lived from the Middle to the Late Eocene, in what is today South America.
Taxonomy
''Xesmodon'' was named by Carlos Berg in 1899. Its type species is ''Xesmodon langi'', and a second species, ''Xes ...
''. However, the phylogenetic analysis of McGrath and colleagues recovered the included genera to neither form their own clade, or to universally represent basal taxa outside the genera of Proterotheriinae per Soria, making Anisolambdinae a polyphyletic
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
group of unrelated organisms.
Proterotheriidae was redefined by McGrath and colleagues in 2019 to be all taxa closer to ''Tetramerorhinus
''Tetramerorhinus'' is an extinct genus of proterotheriid litoptern that lived during the Early and Middle Miocene in what is now Argentina and Peru.
Description
This animal resembled a small horse, with slender, elongated legs. The body was a ...
'' than ''Macrauchenia
''Macrauchenia'' ("long llama", based on the now-invalid llama genus, ''Auchenia'', from Greek "big neck") is an extinct genus of large ungulate native to South America from the Pliocene or Middle Pleistocene to the end of the Late Pleistocene. I ...
'', ''Tricoelodus
''Tricoelodus'' is an extinct genus of adianthid litopterns that lived during the Late Oligocene in what is now Argentina and Bolivia. Fossils of this genus have been found in the Sarmiento Formation of Argentina and the Salla Formation of Bol ...
'' or '' Protolipterna''. The cladogram below shows the modified results of their phylogenetic analysis, where incomplete taxa were placed based on morphology. The unrelated genera of the polyphyletic taxon Anisolambdinae or Anisolambdidae is highlighted in pink.
References
{{Taxonbar, from=Q138661 Litopterns Prehistoric mammal families Paleocene first appearances Holocene extinctions Pleistocene mammals of South America Neogene mammals of South America Paleogene mammals of South America Taxa named by Florentino Ameghino