Questions and Answers
Which of the following characteristics are true for marsupials? (Select all that apply)
What is the infraclass that marsupials belong to?
Metatheria
Which superorder includes the orders Didelphimorphia and Paucituberculata?
What are the main characteristics of the order Didelphimorphia?
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Which family does the New World opossum belong to?
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What type of opossums does the order Paucituberculata include?
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All marsupials have a marsupium.
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Which order includes the marsupial mole?
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Match the following families with their characteristics:
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Study Notes
Infraclass Metatheria
- Represents marsupials characterized by young born incompletely developed after a brief gestation period.
- Young are nurtured on teats, often within a pouch (marsupium), displaying high altriciality.
- Possesses a simple placenta, a relatively small braincase, and in most cases, epipubic bones.
- Marsupials generally exhibit more than 44 teeth, with variations in dental structures.
- Chromosomal count is relatively low, and teeth can be classified as diprotodont (two forward-facing incisors) or polyprotodont (full set of teeth).
- Feet are adapted for specific locomotion types; syndactyl (fused toes) or didactyl (separate toes).
- Reproductive traits include a double uterus and vagina with about 50% of species having a functional pouch.
- Choriovitelline placenta is present, lacking villi, leading to the birth of small, underdeveloped young.
- Unique traits include a forked penis and significant evolution with fossils like Didelphidae from the late Cretaceous.
Biogeography & Evolution
- Fossil evidence shows earliest marsupials originated in North America, with subsequent radiation in South America and Australia.
- Extinction of many marsupials in Europe, Asia, and Africa attributed to competition with eutherians.
- Notable instances of convergent evolution include similarities with placental mammals, such as the marsupial "mole" and kangaroo-rat.
Interesting Extinct Species
- Thylacoleo, known as the marsupial "lion."
- Thylacosmilus, a marsupial saber-tooth "cat," whose structure differed from true placental cats.
- Diprotodon, an enormous rhino-sized marsupial.
- Giant marsupials exhibited notable gigantism, such as fossilized wombats weighing around 2,800 kg.
Superorder Ameridelphia
- Comprises orders Didelphimorphia and Paucituberculata.
Order Didelphimorphia
- Encompasses New World opossums, which are partially arboreal and omnivorous.
- Includes species like Didelphis virginiana and various Marmosa spp.
- Characterized as a basal marsupial family possessing a long, prehensile tail and clawless, opposable hallux.
Order Paucituberculata
- Contains rat/shrew opossums that are diprotodont and found in Western South America.
- They are insectivorous, with lower incisors adapted for hunting, and notably do not have a marsupium.
Superorder Australiadelphia
- Encompasses the orders Microbiotheria, Notoryctemorphia, Dasyuromorphia, Paramelemorphia, and Diprotodontia.
Order Microbiotheria
- Includes the Monito del Monte (Dromiciops gliroides), a polyprotodont insectivore found in South America.
- Represents a relic lineage, retaining features such as a cloaca and indicating a historical connection to Australian marsupials.
Order Notoryctemorphia
- Known for the marsupial mole, which resides in sandy areas of NW and SC Australia, adept at 'swimming' through sand.
- Features include polyprotodont dentition and unique evolutionary adaptations like reversed pouch orientation to prevent sand accumulation.
Order Dasyuromorphia
- Includes diverse carnivorous marsupials with notable families including Thylacine and Tasmanian Devil (not fully detailed in text provided).
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Description
Explore the fascinating world of marsupials through these flashcards. Learn about the infraclass Metatheria, characteristics of marsupials, and their unique reproductive traits. Perfect for anyone studying marsupial biology or classification.
