The Litopterna, also known as the pseudo-horse, is an order of fossil mammals from the Tertiary Period that displays toe reduction. Three-toed, and even a one-toed horselike form were developed. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (flatworms, echinoderms, etc. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors) Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... A fossil Ammonite Fossils (from Latin fossus, literally having been dug up) are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors) Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... The Tertiary period was previously one of the major divisions of the geologic timescale, from the end of the Cretaceous period about 65 million years ago to the start of the Quaternary period about 1. ...

This order, known only from South America, was common and varied in early faunas and persisted, in decreasing variety, into the Pleistocene. Early forms are near the condylarths, to such an extent that the litopterns might be considered merely as surviving and diversely specialized condylarths. They seem to have originated in South America from the South American condylarths, and therefore to have the same source as the latter. However, there is a growing number of scientists who believes the Litopterna (together with other South-American ungulates) originated completely independent from the other Ungulates, thus are unrelated to the condylarths. They proposed a new clade to contain these groups: the Meridiungulata. South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... The Pleistocene Epoch is part of the geologic timescale. ... Condylarthra is an order of Paleocene mammals. ... Clade with the rank of cohort or super-order, part of the Atlantogenata, containing the South-American Ungulates: Xenungulata, Astrapotheria, Notoungulata and Litopterna. ...

The Litopterna, like the notoungulates and toxodonts, are examples of ungulate mammals that arose relatively independently in "splendid isolation" on the island continent of South America. Like Australia, South America was isolated from all other continents following the breakup of Gondwana. During this period of isolation, unique mammals evolved to fill ecological niches similar to other mammals elsewhere. The Litopterna played a role in the ecosystem similar to horses in Laurasia. The Notoungulates are an extinct order of hoofed mammals that were native in South America. ... Toxodonts represent the largest examples of Notoungulate evolution. ... [HELP! Needs re-writing. ... In ecology, a niche is a term describing the relational position of a species or population in an ecosystem. ... Laurasia was a supercontinent that broke off from the Pangaean supercontinent in the late Mesozoic era. ...

Families of Litopterns

• Order Litopterna - Litopterans (all members of the order extinct South American forms)
  • Family Protolipternidae - incertae sedis
  • Superfamily Macrauchenioidea
    • Family Macraucheniidae
    • Family Notonychopidae
    • Family Adianthidae
  • Superfamily Proterothrrioidea
    • Family Prototheriidae

poop poop poop Incertae sedis—of uncertain position (seat)—is a term used to define a taxonomic group where its broader relationships are unknown or undefined. ... This page is a candidate to be copied to Wiktionary. ...

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References

• McKenna, M. C, and S. K. Bell. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp.