Gondwanatheria

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Gondwanatheria
Temporal range: Campanian-Miocene, 70.6–17.5Ma
Sudamerica jaw.svg
Mandible of Sudamerica
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theriiformes
Infraclass: Allotheria
Suborder: Gondwanatheria
Mones, 1987
Subgroups

Gondwanatheria is an extinct group of mammals that lived during the Upper Cretaceous through the Miocene in the Southern Hemisphere, including Antarctica. They are known only from isolated teeth and a few lower jaws, and because of this fragmentary knowledge, their placement is not clear.

Classification[edit]

The affinities of the group are not clear, but gondwanatherians were first interpreted as early xenarthrans, or "toothless" mammals similar to the modern anteater. This is somewhat ironic, given that they were originally known only from teeth. They were also treated as members of the Multituberculata. The latest thinking is apparently returning towards the xenarthran affinities, or something else entirely. However, a few specimens of Gondwanatherians are reclassified as Multituberculates.[2] Recent studies have confirmed their position as allotheres related to multituberculates.[3][4][5]

There are two known families within Gondwanatheria. The family Sudamericidae was named by Scillato-Yané and Pascual in 1984, and includes the genera Sudamerica, Gondwanatherium and Lavanify. The family Ferugliotheriidae was named by José Bonaparte in 1986, and includes one genus, Ferugliotherium.

Further fossils have come from India and Antarctica, where Gondwanatherians once lived in the lush forests of the Eocene. Some South American genera, previously considered to be metatherians, are reassigned to Gondwanatheria: the Eocene genus Groeberia and the Miocene (Colhuehuapian) genus Patagonia.[6]

Antarctica[edit]

The fact that Gondwanatherians were present in Antarctica during the Eocene, while the South American varieties became extinct, indicates that the factors that caused their extinction did not affect this continent.[7] Fossils found on Seymour Island of Gondwanatherians (Sudamericidae) show adaptations for a semi-aquatic and perhaps a burrowing way of life, similar to that of living beavers. This suggests an important paleoecological constraint related to dietary preference of this group.[7] Anyway, at the end of the Eocene the climate became unsuitable and most of the flora and fauna of Antarctica became extinct. This includes small, arboreal, fruit and insect-eating possums, 10 kg (22 lb) sloths, middle-to-large sized grazers (sparnotheriodontids and Trigonostylops), falcons and ratites.

References[edit]

  1. ^ Francisco J. Goin, Marcelo F. Tejedor, Laura Chornogubsky, Guillermo M. López, Javier N. Gelfo, Mariano Bond, Michael O. Woodburne, Yamila Gurovich, Marcelo Reguero (2012). "Persistence of a Mesozoic, non-therian mammalian lineage (Gondwanatheria) in the mid-Paleogene of Patagonia". Naturwissenschaften 99 (6): 449–463. doi:10.1007/s00114-012-0919-z. 
  2. ^ Kielan-Jaworowska & Hurum (2001). "Phylogeny and Systematics of multituberculate mammals". Paleontology 44: 389–429. 
  3. ^ Krause, David W.; Hoffmann, Simone; Wible, John R.; Kirk, E. Christopher; Schultz, Julia A.; von Koenigswald, Wighart; Groenke, Joseph R.; Rossie, James B. (2014-11-05). O'Connor, Patrick M., Seiffert, Erik R., Dumont, Elizabeth R., Holloway, Waymon L., Rogers, Raymond R., Rahantarisoa, Lydia J., Kemp, Addison D., Andriamialison, Haingoson. "First cranial remains of a gondwanatherian mammal reveal remarkable mosaicism". Nature (Nature Publishing Group, a division of Macmillan Publishers Limited). online. doi:10.1038/nature13922. ISSN 1476-4687. 
  4. ^ Drake, Nadia (November 5, 2014). "Fossil From Dinosaur Era Reveals Big Mammal With Super Senses". nationalgeographic.com. National Geographic Society. Retrieved November 5, 2014. 
  5. ^ Wilford, John Noble (November 5, 2014). "Fossil’s Unusual Size and Location Offer Clues in Evolution of Mammals". New York Times. Retrieved November 6, 2014. 
  6. ^ Nicolás R. Chimento, Federico L. Agnolin and Fernando E. Novas. "The bizarre ‘metatherians’ Groeberia and Patagonia, late surviving members of gondwanatherian mammals". Historical Biology: An International Journal of Paleobiology. in press. doi:10.1080/08912963.2014.903945. 
  7. ^ a b Reguero, M.A.; Sergio, A.M.; Santillana, S.N. (2002). "Antarctic Peninsula and South America (Patagonia) Paleogene terrestrial faunas and environments: biogeographic relationships". Palaeogeography-Palaeoclimatology-Palaeoecolog 179: 189–210. 

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