Difference Between Mammals and Marsupials

Main Difference – Mammals vs Marsupials

Mammals and marsupials are two groups of animals that belong to the phylum Chordata. Mammals represent a class of the phylum Chordata while marsupials represent a mammalian infraclass. The main difference between mammals and marsupials is that mammals are characterized by the presence of mammary glands to feed the young whereas marsupials are characterized by the presence of a pouch to carry the young. Mammals give birth to fully-developed young while marsupials give birth to the undeveloped young that should be placed in a pouch for the further development.

Key Areas Covered

1. Mammals
– Definition, Facts, Characteristics
2. Marsupials
– Definition, Facts, Characteristics
3. What are the Similarities Between Mammals and Marsupials
– Outline of Common Features
4. What is the Difference Between Mammals and Marsupials
– Comparison of Key Differences

Key Terms: Hair, Marsupials, Mammals, Mammary Glands, Pouch, Teeth, Young, Warm-blooded Animals

Mammals – Definition, Facts, Characteristics

Mammals refer to the warm-blooded animals that nourish their young with milk secreted by mammary glands and have skin more or less covered by hair. Marsupials, monotremes, and placentals are the three types of mammals. Approximately, 5,500 species of mammals are found in each and every habitat on the earth such as tropical rainforests, deep sea, and deserts. Generally, mammals grow into a large body size. The size of mammals varies from one-ounce (shrews) to 200 tons (Whale). As mammals are warm-blooded animals, they maintain their body temperature independent from the external environment by the heat produced by their endothermic metabolism. One of the key features of a mammal is the presence of fur or hair growing in some parts of the body. The hair can be in different forms such as thick fur, horns, long whiskers, and defensive quills. The main function of hair is the insulation of the body against cold.

Mammals exhibit internal fertilization and the embryo carried inside the mother. Mammals give birth to mostly-developed live young. One of the most significant features of mammals is the presence of mammary glands to breastfeed the young. These glands are a type of enlarged sweat glands. A placental mammal with its young is shown in figure 1.

Figure 1: Cow and Calf

The lower jawbone of mammals is a single piece of bone directly attached to the skull. Mammals have three bones in their middle ear for the transmission of sounds to the inner ear. Vertebrates including mammals possess a diaphragm, which aids in the expansion and contraction of lungs. Like all vertebrates, mammals have a muscular heart with four chambers.

Marsupials – Definition, Facts, Characteristics

Marsupials are mammals of an order whose members are born incompletely developed and are typically carried and suckled in a pouch on the mother. They have approximately 334 species including kangaroos, possums, koalas, and bandicoots. As marsupials are a group of mammals, they give birth to the young. Marsupials have a uterus and a placenta. The placenta is more like a yolk sac. The baby is attached to the placenta only for a short period of time. Hence, the young is very small and undeveloped. It is blind at birth and lacks ears and back legs. But, it has strong and stumpy front legs. The sense of the smell in young marsupials is well-developed. Hence, the young can crawl from the mother’s birth channel into the pouch. It attaches to one of the nipples inside the mother’s pouch for many months until it grows into a young animal. A kangaroo with its joey is shown in figure 2.

Difference Between Mammals and Marsupials

Figure 2: A Kangaroo and Its Joey

Marsupials have more teeth in their mouth than other mammals. However, they develop only a single set of teeth during their lifetime.

Similarities Between Mammals and Marsupials

Both mammals and marsupials belong to the phylum Chordata.
Both mammals and marsupials are warm-blooded animals.
The body of both mammals and marsupials is covered by hair.
Both mammals and marsupials have a uterus and placenta.
Both mammals and marsupials produce milk to feed the young.
Both mammals and marsupials exhibit parental care for the young.

Definition

Mammals: Mammals refer to the warm-blooded animals that nourish their young with milk secreted by mammary glands and have skin more or less covered by hair.

Marsupials: Marsupials refer to a type of mammals characterized by the presence of a pouch in females to rear the young.

Significance

Mammals: Mammals have mammary glands that produce milk to feed the young.

Marsupials: Marsupials have a pouch to carry their young.

Birth

Mammals: Mammals give birth to well-developed, live young.

Marsupials: Marsupials give birth to very small, undeveloped, live young.

Placenta

Mammals: Mammals have a well-developed placenta.

Marsupials: The placenta of the marsupials is like a yolk sac and the baby is attached to the placenta for a short period of time.

Features of the Baby

Mammals: The babies of mammals are well developed at birth.

Marsupials: The babies of marsupials are blind at birth and have no ears and back legs.

Lactation Period

Mammals: The lactation period of mammals is several months.

Marsupials: The lactation period of marsupials is longer than other placental mammals.

Number of Teeth

Mammals: Other mammals have less number of teeth than marsupials.

Marsupials: Marsupials have a higher number of teeth than mammals.

Sets of Teeth

Mammals: Mammals develop two sets of teeth during their lifetime as milk teeth are replaced by adult teeth.

Marsupials: Marsupials develop a single set of teeth during their lifetime.

Body Temperature

Mammals: Body temperature of placentals and monotremes are 38 and 30 degrees Celsius.

Marsupials: Body temperature of marsupials is 35 degrees Celsius.

Basal Metabolic Rates (BMRs)

Mammals: Mammals have higher metabolic rates.

Marsupials: Marsupials have low basal metabolic rates 30% lower than placentals.

Examples

Mammals: Placentals include humans, cats, horses, whales etc. Monotremes include platypus and echidna.

Marsupials: Marsupials include kangaroos, possums, koalas, and bandiccots.

Conclusion

Marsupials, monotremes, and placentals are the three types of mammals. The main feature of mammals is the presence of mammary glands and hair that covers the body. Marsupials give birth to undeveloped, very small young that is further developed inside a pouch. Other mammals such as placentals give birth to well-developed young. Therefore, the main difference between mammals and marsupials is the type of development in the young.

Reference:

1. Strauss, Bob. “These Eight Traits Separate Mammals From Other Vertebrates.” ThoughtCo, Available here.
2. Marsupial Mammals, University of California Museum of Paleontology, Available here.

Image Courtesy:

1. “Cow and calf” (CC BY-SA 3.0) via Commons Wikimedia
2. “Kangaroo and joey03” By Taken byfir0002 | flagstaffotos.com.auCanon 20D + Canon 70-200mm f/2.8 L – Own work (GFDL 1.2) via Commons Wikimedia