Evolution of Macropodidae

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The Macropodidae are an extant family of marsupial with the distinction of the ability to move bipedally on the hind legs, sometimes by jumping, as well as quadrupedally. They are herbivores, but some fossil genera like Ekaltadeta are hypothesised to have been carnivores.[1] The taxonomic affiliations within the family and with other groups of marsupials is still in flux.[2] Macropodids are considered to be the most diverse group of marsupial herbivores ever to have evolved, and have been the subject of more phylogenetic studies than any other marsupial family.[3]

Earliest macropods

In Australia, there are various fossil taxa described from the

K–T extinction is the Tingamarra fauna of the Eocene, but no taxa assigned to the Macropodidae have been found in these deposits, and these Eocene species are of uncertain relationship to any Oligocene taxa.[citation needed
]

All current families are represented in these Oligocene deposits, but not all sub-families, and those that are not (

macropodoids and are ascribed to the extinct family Balbaridae in the genera Nambaroo and Balbaroo.[2]

Nambaroo occurs in fossil formations from the

Riversleigh and Alcoota fossil deposits.[7] Another family that dates back to this era is the Hypsiprymnodontidae, which includes the two subfamilies Propleopinae and Hypsiprymnodontinae.[2] Both subfamilies have genera of Oligocene age, with the genus Hypsiprymnodon extending that far.[2]

Balaridae is primitive in dental morphology and shares features seen in common with only

cul-de-sac. This it shares with no other macropodids. Another feature that it only shares with Hypsipromnodon is that the lower second premolar is not evicted by the third premolar.[8]

Pleistocene developments

Extinctions

Balbaridae, Bulungamayinae, Sthernuridae all became extinct by the Pleistocene. The reason for their extinctions are unknown but hypotheses include outdated model, climate and habitat changes. Some species of Sthenurus could have been around when humans arrived in Australia, but by this time they were already progressing towards extinction. The taxonomic affiliations within the family and with other groups of marsupials is still in flux.[2]

Current speciation

According to John H. Kaufmann, the major evolutionary trends in the family have been moving towards a larger size and grazing habits. Meanwhile, the trends toward diurnality and group living have had "more modest results".[9]

References

  1. ^ Stephen Wroe, Jenni Brammall, and Bernard N. Cooke "The Skull of Ekaltadeta ima (Marsupialia, Hypsiprymnodontidae?): An Analysis of Some Marsupial Cranial Features and a Reinvestigation of Propleopine Phylogeny, With Notes on the Inference of Carnivory in Mammals Journal of Paleontology. 72(4), 1998, pp. 738-751
  2. ^ a b c d e f g Kear. B. P., Cooke. B. N . A review of macropodoid (Marsupialia) systematics with the inclusion of a new family. Memoirs of the Association of Australasian Palaeontologists 25, 83-101. ISSN 0810-8889
  3. ISSN 0024-4082
    .
  4. doi:10.1017/S0022336000031528
  5. ^ Angela Burk, Michael Westerman, and Mark Springer "The Phylogenetic Position of the Musky Rat-Kangaroo and the Evolution of Bipedal Hopping in Kangaroos (Macropodidae: Diprotodontia)" Systematic Biology 47(3): 457 ± 474, 1998
  6. ^ Schwartz L R S and Megirian D., "A New Species of Nambaroo (Marsupialia; Macropodoidea) from the Miocene Camfield Beds of Northern Australia with Observations on the Phylogeny of the Balbarinae", Journal of Vertebrate Paleontology 24(3):668–675, September 2004
  7. ^ a b c d Flannery. T, Archer. M & Plane. P 1982 "Middle Miocene Kangaroos (Macropoidea:Marsupialia) from three localities in Northern Australia, with a description of two new subfamilies". Journal of Geology and Geophysics, 7, 287-302.
  8. ^ Archer. M. Flannery. T 1985 "Revision of the extinct giant rat kangaroo (Potoroidae:Marsupialia), with description of a new Miocene genus and species and a new Pleistocene species of Propleopus, Journal of Paleontology, Vol. 59, No 6, pp. 1331-1349.
  9. ISSN 0003-1569
    .
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