marsupials of Patagonia

MARSUPIALS

There are not only in Australia

PHYLUM: Chordata	CLASS: Mammalia	SUBCLASS: Metatheria	ORDER: Marsupialia	ORDER: Microbiotheria
Introduction	New World Oppsosums	Mouse opossum	Opossum	Monito del monte	References
	Introduction
	Marsupials are a diverse group with a fascinating history, traces of which we see in the unusual biogeographic distribution of species. The classification of marsupials is an area of intense interest among systematists who work on mammals, and a number of arrangements have been suggested and are in use. The one used here, recognizing about 30 families and placing them in a single order, is perhaps the most widely accepted, but recent studies (based both on molecular characteristics and skeletal morphology) suggest that it may not be correct. Characteristics of marsupials include epipubic bones; a pouch in which the young are kept and nourished for an extended period; an unusual short gestation period (around 2 weeks in most species), with young born in an extremely immature state; brain relatively smaller (compared to body size) than in most placental mammals; vaginal canals separate, and a new structure, the pseudovaginal canal, present in females that have given birth; plus numerous other traits of the skull, dentition, and soft anatomy. Marsupials are found today in North America, South America, New Guinea, Australia, and adjacent islands.
	Didelphidae
	New World Opossums
	Restricted to North and South America, didelphids have radiated into a wide variety of forms. Most are omnivorous or carnivorous. Several species are arboreal; one is aquatic. Didelphids can be found in most habitats from sea level to over 3000m, from dry thornscrub and grassland to tropical forest. Extinct didelphids were even more varied in their morphology and habits; one group specialized as large carnivores, with one species actually resembling sabre-toothed cats, while another group apparently converged on kangaroo rats and other desert rodents. Didelphids have a full complement of teeth (five upper and four lower incisors on each side of the jaw, one canine, three premolars, and four molars). Opossums are small to medium in body size; all have five digits on fore- and hindfeet, with the first toe on the hindfoot partially opposable; all digits except the first toe on the hindfoot have claws (it has a nail). The tail is long, scaley, and prehensile in most species.
	Marmosa agilis
	South America mouse opossums
	This is a Nearctic, Neotropical specie that can be found from Eastern Brazil to Eastern Peru and Northern Argentina. Biology: Mass: 40 to 130 kg. The head-body length averages 110 mm while the tail length averages 137 mm. The males and females are relatively equal in size. Their tails are naked and prehensile. They have an opposable big toe on their hind feet which allows them to rapidly climb thin vines. Their opposable toes lack claws. They have very mobile membraneous ears. Because they are nocturnal, hearing is an important sens. Omnivores. They feed mainly on insects and soft fruits. Nocturnal and feed at night. The females produce two litters annually. The females first estrus occurs at 265-75 days. Gestation lasts about 20 days. The female has 13 teats. Not all of the teats are functionning. The maximum litter size is 11. The average size of a litter is 7-9. The weight of the newborns is less than 250 mg. The young are altricial when they are born. This particular species lacks a pouch. After the young are born they crawl up the mother's belly and attach themselves to a nipple. Weaning occurs at 60-70 days. The young leave the mother a few days after they have been weaned. These opossums are solitary animals. They hunt and nest alone. They live in dens or in nests that they have taken over from other species. Lives in forest habitats, particularly in the tropical deciduous forest biome.
	Didelphis virginiana
	Opossum
	This is a Nearctic specie. The opossum is found in North America, throughout all of Mexico and Central America.(in wild, but there are introduced animal in Patagonia). In the United States it is found on the West Coast and in areas east of the Rocky Mountains. Biology: Mass: 2.2 to 5.4 kg. Opossums have a heavy set body that resembles a large house cat. They have longs heads with a pointed snout. Their faces have long whiskers. All opossums have long, tapered tails with a scaly appearance. Females have a fur-lined pouch to carry their young. The color of the opossum varies by the region. Northern populations have thick underfur that is white in color and has black tips. The pale guard hairs give the opossum a gray appearance. In the southern populations, the underfur is much sparser. Both northern and southern species have white cheek hairs. They are omnivorous, including a wide variety of food in their diet. A majority of their diet is composed of insects and carrion. Opossums are also known to eat plants, including fruits and grains in season. Reproduction: The egg is fertilized in the Fallopian tubes. Birth occurs about 12.5 to 13 days after copulation. The average litter size ranges from 6.8 to 8.9. Depending on latitude, opossums have one or two litters per year. The young opossums weigh about 0.16 grams at birth. They are fixed to the nipple for the first 50 to 65 days of their lives. By 95 to 105 days, the young no longer depend on their mother. There is no maternal bond between the mother and young after they are weaned. Females are able to breed in their first season. Behavior: Opossums are nocturnal animals and have very poor social development. Females tend to live in groups, but the males fight when confined together. Groups of opossums are composed primarly of young because of the short life span of the opossums. Opossums, both male and female, are very aggressive. They use various forms of intimidation to defend themselves but usually play dead when they encounter a more powerful opponent. Opossums usually travel across the land but will swim in some cases to escape danger. For grooming, opossums use their hind feet to clean their fur and wash their faces with their fore feet. To transport her young, a mother places them on her tail. The mating season for opossums lasts from January to July. Copulation is usually initiated by the male. After copulation, the female rejects any more solicitations. Opossums are found in a variety of environments, ranging from relatively arid to mesic environments. They prefer wet areas, however, especially streams and swamps. It is hard to determine the exact home range of an opossum because of their unusual movement patterns. . They live mainly in temperate forest & rainforest
	Order Microbiotheria
	Monito del monte (Dromiciops australis)
	This order of marsupials contains one family (Microbiotheriidae) with one living species (Dromiciops australis, common name "monito del monte"). It also includes a genus of fossil species, Microbiotherium, which included six known species and lived during Oligocene and Miocene times. The order is known only from South American; currently, Dromiciops is found in the Andes of Chile and Argentina. While not diverse, microbiotheres are especially interesting because they may be more closely related to Australian marsupials (Cohort Australidelphia) than to any South American family. This tentative conclusion is based on both anatomical and molecular investigations (summarized by Aplin and Archer, 1987). Research on the relationships of microbiotheres and other marsupials is an active and fascinating field, however, and the last word on the phylogeny of these animals probably has yet to be written. These evolutionary ties between the South American Microbiotheriidae and the Australian marsupials help to illuminate the biogeographic history of the Marsupialia. The current hypothesis of Marsupial biogeography holds that Marsupials originated in North America, dispersed to South America (where they underwent a spectacular radiation), moved across Antarctica and into Australia where they enjoyed a second radiation. Consistent with this hypothesis, the Microbiotheriidae are either a relict of the line leading to the Australian marsupials, or they are a reinvasion of South America by the Australian forms. Additional fossil evidence and comparative studies may help to resolve this question. Dromiciops is a small animal with a long, moderately prehensile tail and silky, dense pelage. Its ears are short and rounded. The pouch or marsupium is well developed. Dromiciops has a peculiar skull, especially compared to that of the didelphids (with which it was once classified). The premaxillae is elongated; the nasals are expanded posteriorly; and paroccipital processes are absent. The auditory bullae are unique: large, inflated, ossified, with the anterior third of the bullar wall formed by a large process of the alisphenoid. The teeth are also unusual. The upper and lower incisors are broad and spatulate. The uppers form a semicircle or U-shaped arcade, while the lowers are splayed outward. The cusps of the cheekteeth are low and rounded compared to those of didelphids. The dental formula, however, is identical to that of the Didelphidae (5/4, 1/1, 3/3, 4/4 = 50), and like didelphids, Dromiciops is not syndactylous.
	References
	Bibliography of Marsupials
	Part of the above information was adapted from: The animal diversity web: http://www.oit.itd.umich.edu/bio108/ Aplin, K. P., and M. Archer. 1987. Recent advances in marsupial systematics with a new syncretic classification. Pp. xv-lxxii in Archer, M. (ed.), Possums and Opossums: Studies in Evolution, Vol. I. Surrey Beatty and Sons PTY Limited, Chipping Norton. lxxii 400 pp. Baker, R.H. 1983. Michigan Mammals. Michigan State University Press. United States of America. Grizmek's Encyclopedia of Mammals. 1990. V.1. McGraw-Hill Publishing Company, New York. Lee, A. L. & Cockburn, A. 1985. Evolutionary Ecology of Marsupials. Cambridge University Press, Cambridge. Marshall, L. G. 1984. Pp. 59-115 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii 686 pp. McManus, J.J. (2 May 1974) "Didelphis virginiana." Mammalian Species. The American Society of Mammalogists, 40. Nowak, R. M. 1991. Walker's Mammals of the World. V.1. The Johns Hopkins University Press, Baltimore. Stonehouse, B. & Gilmore, D. 1977. The Biology of Marsupials. University Park Press, Baltimore. Szalay, F. (1982). A new appraisal of marsupial phylogeny and classification. In: "Carnivorous marsupials" ed by M. Archer. Roy. Zool. Soc. New South Wales: Sydney, Australia. Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vii 576 pp. Tyndale-Biscoe, H. 1973. Life of Marsupials. American Elsevier Publishing Company, Inc., New York. Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii 1206 pp.

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