Proterotheriidae

Proterotheriidae is an extinct family of fossil ungulates from the Cenozoic era that displays toe reduction. Despite resembling primitive, small horses, they were only distantly related to them, and instead belonged to the native South American ungulate order Litopterna.

Proterotheriidae
Skull of Thoatherium
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: †Litopterna
Superfamily: †Proterotherioidea
Family: †Proterotheriidae
Ameghino 1887
Synonyms
  • Anisolambdidae Soria, 2001
  • Anisolambdinae Cifelli, 1983
  • Indaleciinae Bond & Vucetich 1983
Interpretation of Thoatherium

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 recens survived into the Late Pleistocene.[1][2][3]

Better known genera of the family include Diadiaphorus and Thoatherium from the Miocene.[1]

Taxonomy
  • Proterotheriidae[4]
    • Epecuenia
    • Prothoatherium?
    • Anisolambda
    • Anisolophus
    • Brachytherium
    • Diadiaphorus
    • Eoauchenia
    • Epitherium
    • Lambdaconus
    • Mesolicaphrium
    • Neobrachytherium
    • Neodolodus
    • Neolicaphrium
    • Olisanophus
    • Paramacrauchenia
    • Paranisolambda
    • Picturotherium
    • Proterotherium
    • Protheosodon
    • Tetramerorhinus
    • Thoatherium
    • Thoatheriopsis
    • Villarroelia
    • Uruguayodon
    • Megadolodinae
    • Indet.
      • Deuterotherium?
      • Diplasiotherium
      • Eoproterotherium
      • Licaphrium
      • Prolicaphrium
      • Protheosodon
      • Richardolydekkeria
      • Wainka
      • Xesmodon

Proterotheriidae was redefined by McGrath and colleagues in 2019 to be all taxa closer to Tetramerorhinus than Macrauchenia, Tricoelodus or Protolipterna.[4] The cladogram below shows the modified results of their phylogenetic analysis, where incomplete taxa were placed based on morphology. The clade Anisolambdinae or Anisolambdidae is highlighted in pink, an unrelated group of proterotheriids, and the clade Indaleciinae is highlighted in green.[5]

Proterotheriidae
 
 

Megadolodus

 
 

Bounodus

 
 
 
 
 

Indalecia

 
 

Adiantoides

 
 
 
 

Paramacrauchenia

 
 
 

Anisolambda

 
 
 

Lambdaconus suinus

 
 

Lambdaconus inaequifacies

 
 
 
 

Lambdaconus lacerum

 
 
 

Paranisolambda

 
 
 

Picturotherium

 
 
 
 

Neodolodus

 
 

Protheosodon

 
 
 
 

Anisolophus floweri

 
 
 
 

Anisolophus australis

 
 
 

Anisolophus minusculus

 
 

Prolicaphrium specillatum

 
 
 
 
 
 

Olisanophus

 
 
 

Mesolicaphrium

 
 

Diplasiotherium

 
 
 
 
 

Villarroelia

 
 
 

Tetramerorhinus fleaglei

 
 
 

Tetramerorhinus prosistens

 
 
 
 

Tetramerorhinus cingulatum

 
 
 

Tetramerorhinus lucarius

 
 

Tetramerorhinus mixtum

 
 
 
 
 
 

Diadiaphorus

 
 

Thoatherium

 
 
 
 
 

Brachytherium

 
 
 

Thoatheriopsis

 
 
 

Proterotherium

 
 

Neobrachytherium ameghinoi

 
 
 
 
 
 

Eoauchenia

 
 

Neobrachytherium ullumense

 
 
 

Neobrachytherium morenoi

 
 

Neobrachytherium intermedium

 
 
 
 

Neolicaphrium

 
 
 

Epitherium

 
 

Uruguayodon

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

References
  1. Scherer, C.; Pitana, V.; Ribeiro, A. M. (2009). "Proterotheriidae and Macraucheniidae (Litopterna, Mammalia) from the Pleistocene of Rio Grande do Sul State, Brazil". Revista Brasileira de Paleontologia. 12 (3): 231–246. doi:10.4072/rbp.2009.3.06.
  2. Ubilla, M.; Perea, D.; Bond, M.; Rinderknecht, A. (2011). "The first cranial remains of the Pleistocene proterotheriid Neolicaphrium Frenguelli, 1921 (Mammalia, Litopterna): a comparative approach". Journal of Vertebrate Paleontology. 31 (1): 193–201. doi:10.1080/02724634.2011.539647.
  3. Gaudioso, P. J.; Gasparini, G. M.; Herbst, R.; Barquez, R. M. (2017). "First record of the Neolicaphrium recens Frenguelli, 1921 (Mammalia, Litopterna) in the Pleistocene of Santiago del Estero Province, Argentina". Papéis Avulsos de Zoologia. 57 (31): 23–29.
  4. McGrath, A.J.; Flynn, J.J.; Wyss, A.R. (2019). "Proterotheriids and macraucheniids (Litopterna: Mammalia) from the Pampa Castillo Fauna, Chile (early Miocene, Santacrucian SALMA) and a new phylogeny of Proterotheriidae". Journal of Systematic Palaeontology: 1–22. doi:10.1080/14772019.2019.1662500.
  5. Andrew J. McGrath; Federico Anaya; Darin A. Croft (2020). "New proterotheriids (Litopterna, Mammalia) from the middle Miocene of Quebrada Honda, Bolivia, and trends in diversity and body size of proterotheriid and macraucheniid litopterns". Ameghiniana. 57 (2): 159–188. doi:10.5710/AMGH.03.03.2020.3268.
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