Microbiotheria

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Microbiotheres
Temporal range: Early Palaeocene – Recent
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Marsupialia
Superorder: Australidelphia
Order: Microbiotheria
Ameghino, 1889
Family: Microbiotheriidae
Ameghino, 1887

Microbiotheria are a small order of marsupial mammals with only one living species, the Monito del Monte (Spanish for 'little mountain monkey').

It is the only New World representative of the superorder Australidelphia; all other New World marsupials are part of the Ameridelphia.

The species is nocturnal and arboreal, and lives in thickets of Chilean bamboo in the temperate rain forests of the southern Andes.[1][2] It eats mainly insects and other small invertebrates, supplemented with fruit.[2]

At one time, they were placed in the order Didelphimorphia, the opossums, but due to many morphological differences, they were placed in another order. The skull's shape is strange, with many technical differences from the opossums.

Phylogeny and biogeography[change | change source]

An artistic rendering of the Monito del Monte

It has long been suspected that South American marsupials were ancestral to those of Australia. The two continents were connected via Antarctica in the early Cainozoic era.

Australia’s earliest known marsupial is Djarthia, a primitive mouse-like animal that lived about 55 million years ago. Djarthia had been identified as the earliest known australidelphian, and this research suggested that the Monito del Monte was the last of a clade which included Djarthia.[2][3]

In 2010, analysis of retrotransposon insertion sites in the nuclear DNA of marsupials confirmed the placement of the Monito del Monte in Australidelphia. It also showed its position as the most basal of that superorder.[4]

The study also confirmed that the most basal of all marsupial orders are the other two South American lineages (Didelphimorphia and Paucituberculata, with the former probably branching first). This indicates that Australidelphia arose in South America (with the ancestors of all other living marsupials), and probably reached Australia in a single dispersal event after Microbiotheria split off (originated).[5][6][7]

References[change | change source]

  1. Diaz M. & Teta P. (2008). Dromiciops gliroides. 2008 IUCN Red List of Threatened Species. IUCN 2008. Retrieved on 28 December 2008. Database entry includes justification for why this species is listed as near threatened
  2. 2.0 2.1 2.2 "Monito del monte (Dromiciops gliroides)". EDGE of Existence programme. Zoological Society of London. 2006. http://www.edgeofexistence.org/mammals/species_info.php?id=42. Retrieved 2009-07-05.
  3. Beck et al., Robin M.D. (2008). "Australia's oldest marsupial fossils and their biogeographical implications". PLoS ONE (Public Library of Science) 3 (3): e1858. doi:10.1371/journal.pone.0001858 . PMC 2267999 . PMID 18365013 .
  4. 'Basal': term in cladistics meaning closest to the origin of the clade, or most 'primitive'.
  5. Schiewe, Jessie (2010). "Australia's marsupials originated in what is now South America, study says". LATimes.Com. Los Angeles Times. http://www.latimes.com/news/science/la-sci-marsupial-20100728,0,5549873.story. Retrieved 2010-08-01.
  6. Inman, M. (2010). "Jumping genes reveal kangaroos' origins". PLoS Biology (Public Library of Science) 8 (7): e1000437. doi:10.1371/journal.pbio.1000437 . PMC 2910652 . PMID 20668663 .
  7. Nilsson et al., M.A. (2010). "Tracking marsupial evolution using archaic genomic retroposon insertions". PLoS Biology (Public Library of Science) 8 (7): e1000436. doi:10.1371/journal.pbio.1000436 . PMC 2910653 . PMID 20668664 .