Condylarthra is an informal group – previously considered an
order – of extinct
placental mammals, known primarily from the
Paleocene and
Eocene epochs.[1] 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.[2][3][4]
Taxonomic history
Condylarthra always was a problematic group. When first described by
Cope 1881,
Phenacodontidae was the type and only family therein.
Cope 1885, 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.[5] 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.[6]
Prothero, Manning & Fischer 1988 delimited condylarths as those having the following characters, but lacking the specializations present in more derived orders:[5]
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.
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,[8][9] 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.[4] 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[10] and
Dinocerata.[11]
Janis, C.M. (1993). "Tertiary Mammal Evolution in the Context of Changing Climates, Vegetation, and Tectonic Events". Annual Review of Ecology and Systematics. 24: 467–500.
doi:
10.1146/annurev.es.24.110193.002343.
Madsen, O.; Scally, M.; Douady, C.J.; Kao, D.; DeBry, R.W.; Adkins, R.; Amrine, H.M.; Stanhope, M.J.; de Jong, W.W.; Springer, M.S. (2001). "Parallel adaptive radiations in two major clades of placental mammals". Nature. 409 (6820): 610–614.
Bibcode:
2001Natur.409..610M.
doi:
10.1038/35054544.
PMID11214318.
S2CID4398233.
McKenna, M.C.; Bell, S.K. (1997). Classification of Mammals Above the Species Level. Columbia University Press.
ISBN978-0-231-11012-9.
Murphy, W.J.; Eizirik, E.; O'Brien, S.J.; Madsen, O.; Scally, M.; Douady, C.J.; Teeling, E.C.; Ryder, O.A.; Stanhope, M.J.; de Jong, W.W.; Springer, M.S. (2001). "Resolution of the early placental mammal radiation using Bayesian phylogenetics". Science. 294 (5550): 2348–2351.
Bibcode:
2001Sci...294.2348M.
doi:
10.1126/science.1067179.
PMID11743200.
S2CID34367609.
Novacek, M.J. (1986). "The skull of leptictid insectivorans and the higher-level classification of eutherian mammals". Bulletin of the American Museum of Natural History. 183 (1): 1–111.
hdl:
2246/1628.
Prothero, D.R.; Manning, E.M.; Fischer, M. (1988).
"The phylogeny of the ungulates"(PDF). In Benton, M. J. (ed.). The phylogeny and classification of the tetrapods. 2: mammals. Systematics Association Special Volume 35B. Oxford: Clarendon Press. pp. 201–234.
ISBN9780198577126. Retrieved May 1, 2013.
Thewissen, J.G.M. (1990). Evolution of Paleocene and Eocene Phenacodontidae (Mammalia, Condylarthra). Papers on Paleontology. Vol. 29. Museum of Paleontology, The University of Michigan.
hdl:
2027.42/48629.
OCLC742731818.
Van Valen, L.M. (1966). "Deltatheridia, a new order of mammals". Bulletin of the American Museum of Natural History. 132 (1): 1–126.
hdl:
2246/1126.
Van Valen, L.M. (1988). "Paleocene dinosaurs or Cretaceous ungulates in South America?". Evolutionary Monographs. 10: 1–79.
External links
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