Science, Tech, Math › Science Mammal Species Share Flipboard Email Print Kitty Terwolbeck/Flickr Science Biology Ecology Basics Cell Biology Genetics Organisms Anatomy Physiology Botany Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated April 13, 2019 Have you ever thought about what makes mammal species different from other vertebrates? If not, I'm sure that you have noticed the differences between a snake, which is a reptile, and an elephant. Being a mammal myself, I have always found this particular class of vertebrates very interesting. As you will see, mammals have certain characteristics that differentiate them from other vertebrates. Let's take a look at some of these characteristics. Mammal Characteristics To begin with, mammal species are in the Class Mammalia, within the Subphylum Vertebrata, under the Phylum Chordata, in the Kingdom Animalia. Now that you have that straight, let's look at some specific traits of mammals. One main characteristic that mammals have is a feature that usually stands on end in frightening situations. Can you guess what it is? Yes, it's hair or fur, whichever the case may be. This trait is useful in maintaining the constant body temperature that is important to all endothermic animals. Another characteristic is the ability to produce milk. This comes in handy while nourishing babies which are usually born fully developed (exceptions are the monotremes and the marsupials). Fertilization occurs within the reproductive tract of the female and most have a placenta that provides nutrients to the developing embryo. Mammalian young are usually slow to leave the nest, which allows for a longer period of time for the parents to teach skills that are necessary for survival. Respiratory and circulatory features of mammals include a diaphragm for proper lung ventilation and a heart that has four chambers to ensure that blood is circulated appropriately. Mammals can comprehend and learn things, which can be attributed to a larger brain size as compared to vertebrates of similar size. Finally, the existence of teeth that are different in size and function is a trait that is seen among mammals. All of these characteristics (hair, maintaining a constant body temperature, production of milk, internal fertilization, young born fully developed, highly developed circulatory and respiratory systems, larger brain size, and differences in the size and function of teeth) make mammal species unique among the vertebrates.