Condylarthra Explained

Condylarthra is an informal group – previously considered an order – of extinct placental mammals, known primarily from the Paleocene and Eocene epochs. They are considered early, primitive ungulates. It is now largely considered to be a wastebasket taxon, having served as a dumping ground for classifying ungulates which had not been clearly established as part of either Perissodactyla or Artiodactyla, being composed thus of several unrelated lineages.[1] [2]

Taxonomic history

Condylarthra always was a problematic group. When first described by, Phenacodontidae was the type and only family therein., however, raised Condylarthra to an order and included a wide range of diverse placentals with generalized dentitions and postcranial skeletons. More recent researchers (i.e. post-WW2) have been more restrictive; either including only a limited number of taxa, or proposing that the term should be abandoned altogether. Due to their primitive characteristics condylarths have been considered ancestral to several ungulate orders, including the living Artiodactyla, Cetacea, Perissodactyla, Hyracoidea, Sirenia, and Proboscidea, as well as the extinct Desmostylia, Embrithopoda, Litopterna, Notoungulata, and Astrapotheria.[3]

delimited condylarths as those having the following characters, but lacking the specializations present in more derived orders:

Evolutionary history

The disappearance of the non-avian dinosaurs opened up an ecological niche for large mammalian herbivores. Some condylarths evolved to fill the niche, while others remained insectivorous. This may explain, in part, the tremendous evolutionary radiation of the condylarths that we can observe throughout the Paleocene, resulting in the different groups of ungulates (or "hoofed mammals") that form the dominant herbivores in most Cenozoic animal communities on land, except on the island continent of Australia.

Among recent mammals, Paenungulata (hyraxes, elephants, and sea cows), Perissodactyla (horses, rhinoceroses, and tapirs), Artiodactyla (pigs, deer, antelope, cows, camels, hippos, and their relatives), Cetacea (whales), and Tubulidentata (aardvarks) are traditionally regarded as members of the Euungulata. Besides these, several extinct animals also belong to this group, especially the endemic South American orders of ungulates, (Meridiungulata). Although many ungulates have hooves, this feature does not define the Euungulata. Indeed, some condylarths had small hooves on their feet, but the most primitive forms are clawed.

Recent molecular and DNA research has reorganised the picture of mammalian evolution. Paenungulates and tubulidentates are seen as afrotherians, and no longer seen as closely related to the laurasiatherian perissodactyls, artiodactyls, and cetaceans, implying that hooves were acquired independently (i.e. were analogous) by at least two different mammalian lineages, once in the Afrotheria and once in the Laurasiatheria. Condylarthra itself, therefore, is polyphyletic: the several condylarth groups are not closely related to each other at all. Indeed, Condylarthra is sometimes regarded as a 'wastebasket' taxon. True relationships remain in many cases unresolved.

In addition to meridiungulates and living ungulates, a condylarthran ancestry has been proposed for several other extinct groups of mammals, including Mesonychia and Dinocerata.

Taxonomy

See also

References

Notes and References

  1. Web site: Phenacodontidae, I feel like I know you . Tetrapod Zoology . Scientific American . Darren . Naish . 8 August 2013 . https://web.archive.org/web/20140310022530/http://blogs.scientificamerican.com/tetrapod-zoology/2013/08/08/phenacodontidae-i-feel-like-i-know-you/ . 10 March 2014.
  2. 10.1371/journal.pone.0109232. 25295875. Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls. PLOS ONE. 9. 10. e109232. 2014-10-08. Cooper . L. N. . Seiffert . E. R. . Clementz . M. . Madar . S. I. . Bajpai . S. . Hussain . S. T. . Thewissen . J. G. M.. 4189980. 2014PLoSO...9j9232C. free.
  3. Book: Rose, Kenneth D.. The beginning of the Age of Mammals. 2006. Johns Hopkins University Press. Baltimore. 9780801892219. Archaic Ungulates.
  4. Smith, De Bast. "Reassessment of the Small ‘Arctocyonid’ Prolatidens waudruae from the Early Paleocene of Belgium, and Its Phylogenetic Relationships with Ungulate-Like Mammals". Journal of Vertebrate Paleontology. Retrieved August 2013
  5. Ravel . Anthony . Orliac . Maeva . 2014 . The inner ear morphology of the 'condylarthran' Hyopsodus lepidus . Historical Biology . 27 . 8. 8 . 10.1080/08912963.2014.915823 . 84391276 .
  6. Cooper . L. N. . Seiffert . E. R. . Clementz . M. . Madar . S. I. . Bajpai . S. . Hussain . S. T. . Thewissen . J. G. M. . 2014 . Anthracobunids from the Middle Eocene of India and Pakistan Are Stem Perissodactyls . PLOS ONE . 9 . 10. e109232 . 10.1371/journal.pone.0109232 . 25295875 . 4189980. 2014PLoSO...9j9232C . free .
  7. Halliday . T.J.D. . Upchurch . P. . Goswami . A. . Resolving the relationships of Paleocene placental mammals . Biological Reviews . 2017 . 92 . 1 . 521–550 . 10.1111/brv.12242. 28075073 . 6849585 .
  8. J. David. Archibald. Yue. Zhang. Tony. Harper. Richard L.. Cifelli. May 6, 2011. Protungulatum, confirmed Cretaceous occurrence of an otherwise Paleocene eutherian (placental?) mammal. Journal of Mammalian Evolution. 10.1007/s10914-011-9162-1. April 28, 2013. 18. 3. 153–161. 16724836. https://web.archive.org/web/20160303221519/http://www.bio.sdsu.edu/faculty/archibald.html/ArchibaldEtAl.11JMEonline.pdf. March 3, 2016. dead.
  9. James David Archibald · Alexander Olegovich Averianov, Phylogenetic analysis, taxonomic revision, and dental ontogeny of the Cretaceous Zhelestidae (Mammalia: Eutheria), Article · Feb 2012 · Zoological Journal of the Linnean Society

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