Chordate Zoology - textbook - Y. V. Tsaryk - 2013

Chapter 5. SUPERCLASS TETRAPODS (LAND VERTEBRATES) TETRAPODA, seu QUADRIPEDA.

ANAMNIOTES (ANAMNIA) AND AMNIOTES (AMNIOTA)

5.4. CLASS MAMMALS, OR BEASTS, MAMMALIA, seu THERIA

Mammals are warm-blooded (homeothermic) amniotes; the body is covered with Hair; they are viviparous, nursing their young with milk. They have a relatively large Brain; its anterior part (hemispheres) features a "new cortex"—the neopallium—composed of Gray matter, which ensures a high level of nervous activity and complex adaptive behavior. The Organs of smell, sight, and Touch are well developed. An External ear is present; the Middle ear cavity contains three auditory ossicles: the malleus, incus, and stapes. Bats, dolphins, and some other mammals use ultrasonic echolocation for orientation. The Skin contains numerous sebaceous and Sweat Glands, some of which are modified into mammary and scent glands. The Skull is synapsid, articulating with THE Vertebral Column by two condyles; heterodont Teeth are set in alveoli; the lower jaw consists solely of the dentary bone. They breathe through Lungs of alveolar Structure. The body cavity is divided by a Diaphragm into thoracic and abdominal compartments. The digestive tract is complex; sometimes a multi-chambered Stomach is formed, and the cecum is enlarged. Herbivores exhibit well-developed symbiotic Digestion. The Heart is four-chambered, with two circuits of Blood Circulation; only the left aortic arch is preserved, and red Blood Cells are anucleate. The Kidneys are metanephric. They are widely distributed, inhabiting all biotopes (soil, Water bodies, and the lower layers of the atmosphere). They are highly important components of almost all biocenoses. They are of great importance to humans: as livestock, game species, vectors of dangerous epidemic diseases of humans and domestic animals, agricultural and forestry pests, etc.