Mammals terminology

  • Class Mammilia: Have mammary glands, hair

  • Subclass Prototheria

    • Eggs-laying mamals; mammary glands lack nipples; no functional teeth as adults; skeleton (particularly the limbs with similarities to reptiles

      • Order: Monotremata- monotremes-duck-billed platypus

  • Subclass: Theria: 

    • Viviparous; mammary glands with nipples; skeleton less primiviative


      • Clade Metatheria: 

        • Young born prematurely, complete development while carried by female, usually (but not always) in a pouch (marsupium); prior to birth, a placenta is present, but it is formed by the yolk sac and chorionic membranes. 


  • Infraclass Marsupialia - marsupials; 16 families 


  • Clade Eutheria: Young born in more advanced condition; placenta formed by allantoic and chorionic membranes; the "placental mammals".


  •  21 orders; dominant everywhere except on the island continents of Australia and South America, which they did not reach until relatively recently.  


  • Basic types of Mammal Hair

    • Mammalian hair appears to be a derivation of reptilian scales, or, more specifically, of the apical "bristles" that occur on the scales of certain living reptiles and presumably on the extinct mammal-like reptiles. 


  • Guard Hair: Ih the outer hair that you see is the long, coarse(otters, beavers muskrats

  • Underfur: Its a part of guard hair but it is  the shorter, denser section

    • as a thermoregulatory device (the layer of dead air it traps minimizes heat loss), and, in aquatic species, as an insulator (again relying on the layer of air) that prevents water from coming in contact with the skin. 

  • Vibrissa:  hair that serves a sensory function. The most familiar of these are the "whiskers" on the snout, but they are not necessarily restricted to the snout. 

    • Examine the gray squirrel (Sciurus), a species in which it is important for the animal to be in sensory contact with the tree trunks it climbs.  

  • Modification of Hairs 

Protective Quills:

  • Porcupines (Erethizon):

    • Quills are modified hairs with barbed tips.

    • Barbs prevent removal and cause the quill to work deeper into flesh.

  • European hedgehogs (Order Insectivora) and spiny echidnas (monotremes) also have protective quills.

  • These adaptations evolved independently in different species (convergent evolution).

Scales in Pangolins:

  • Formed by hairs fused into broad keratinized plates.

  • Provide protection and allow rolling into a ball for defense.

Armor in Armadillos:

  • Covered with bony plates, distinct from pangolins’ keratinized plates.

  • Also roll into a ball for protection.

Rhinoceros Horns:

  • Composed of agglutinized hairs bonded with keratin.

  • Cutting the horn reveals individual hair structures in the cross-section.

  • agglutinized hairs:hair that has clumped together due to agglutination


  • The molting of Hair 

  • Pelage: refers to the coat of fur, hair, or wool covering the body of a mammal.

  • Ecological Aspects of coloration 

    • Gloggers Rule:  it states that endotherms in humid regions tend to be darker than related species living in dry, arid regions. Hence we would expect populations living in a moist, humid northern forest to be darker than those living in desert regions, matching the differences between the dark humus of the forest and the pale sand of the desert. Even in desert regions, however, mouse populations living on dark lava flows will be dark, in dramatic contrast to other species living on the sand around the lava.

    • Tecodont:   a type of tooth attachment in which the teeth are set in sockets, or alveoli, in the jawbone. This arrangement provides a strong and stable connection between the tooth and the jaw, allowing for efficient biting and chewing.

    • Diphycodont:Mammals generally have two sets of teeth during their lifetime

      • Milk

      • Permanent 

    • milk(decidious): Baby Teeth

    • Monophyodont: Permanent set/ one set of teeth 

      • Talpidae(mole) have this

    • Kinds and numbers of teeth

      • Heterodont: Refers to an organism having different types of teeth, each specialized for a specific function.

      • Incisors: the front of the jaw, flattened, nipping teeth, 

      • Canine:  the enlarged, fang like, stabbing 

      • Premolars: a series of compressed, blade-like, cutting or shearing 

      • Molars:  flattened, crushing

  • Incetivorous

    • It feeds on insects and other invertebrates (worms, etc.). Note that the front incisors are enlarged and modified for grasping the prey. Following these are a series of unicuspids (single cusp), and then some multicusped teeth. Some of the latter bear three cusps; such tritubercular teeth are similar to those found in the earliest fossil mammals. Note that the cusps are sharp--they are used in cutting up the food. The dentition of the short-tailed shrew (Blarina) is similar, but their effectiveness is enhanced by a poisonous saliva that acts to paralyze (but not kill) their prey. The red-tipped cusps are characteristic of the shrews (Soricidae). 

    • Bats 

    • moles

  • Carnivorous  A carnivorous diet is found in many members of the Order Carnivora, which includes most of the predators that are familiar (cats, dogs, weasels, etc.). Not all members of the order are strictly carnivorous, however, and the distinction shows up in the dentition.  


  • Carnassial- (Key identification for carnivorous) 

    • these are enlarged, blade-like teeth. Those of the upper jaw knife past those of the lower jaw in a shearing action. When a dog is cutting flesh off a bone, it does so near the back of the mouth, using the carnassials. 

  • Sectorial-  note that all of the cheek teeth are of the blade-like, cutting type. The last tooth in both upper and lower jaw is a molar (the only molar); note that in the lower jaw it is not different in shape than the premolars. This absence of crushing teeth suggests a highly carnivorous diet, with chunks of meat being bolted down, rather than crushed.

  • Omnivourus 

    • Bunodont 

    • Brachydont

    •  in which the molars are completely covered with hard enamel, bear low rounded cusps, and are low-crowned (=brachydont); that is, the tooth does not project very far above the jawbone.

  • Herbivourous 

    • Lophodont

      • Lophodont teeth have invaginations of enamel that are continuous with the outside of the tooth and that are arranged transversely across the tooth (see diagrams from Kardong).

    • Selenodont

      •  Selenodont teeth have inclusions of enamel (often looking like smiley faces) surrounded by dentin and arranged longitudinally along the tooth.

    • Brachy-selenodont

    • Hypso-lophodont

      • hypsodont 

  The molars are brachy-selenodont. The "brachy" refers to the fact that the teeth are still relatively low-crowned compared to the more advanced hypso-lophodont molars of a horse. The increased height of the exposed part of the tooth (= hypsodont) is an adaptation that offsets the increased wear caused by the tough (and often gritty) cellulose diet. 


  • Gnawing

    • The rodents (Order Rodentia) have a highly modified, gnawing dentition, in which many teeth have been lost. 

  • Antlers

    • Antlers are bone; they are branched, and shed each year at the end of the breeding (rutting)season.

  • Horns 

    • Horns are characteristic of the cattle family (Bovidae), which includes not only the cattle-like animals, but also goats, sheep, bison, the African antelopes, water buffalo, etc. True horns consist of a bony core covered by a sheath of keratin ("horn"); they are unbranched, and not 

  • Plantigrade

    • a type of locomotion where the entire foot, including the toes and metatarsals, touches the ground during each step.  

  • Digitigrade

    •  Find the heel close to the body of the prepared skin. Animals that walk on their toes are called digitigrade.

  • Unguligrade

    • In the ungulates (hoofed mammals) this trend has continued until the animal walks on its toenails (unguligrade). Deer

  • Cursorial

    • Cursorial (=running): The adaptations for running habits are outlined in the above section, consisting chiefly of elongation of the limbs and restriction of the movement to a forward and backward plane. The musculature for movement is concentrated close to the body, with tendons extending down the long, thin legs. 

  • Salatorial 

    • Saltatorial (jumping): The adaptations for saltation consist of elongation of the hindlimbs (often accompanied by great reduction in the size of the forelimbs) and the tail. Examine the skin of a jumping mouse (Zapus), comparing these features with those of a more typical mouse (Peromyscus) of comparable size. The long hind feet provide great leverage for leaping, and the long tail provides a counterweight (otherwise the mouse would tend to somersault through the air).

  • Arboreal

    • Arboreal: Tree climbers, such as the squirrels, rely on long curved claws for purchase. The tail is characteristically long and bushy, serving as a rudder and as a counterweight when balanced on a branch. The limbs can be extended out to the side of the body; watch a squirrel climb sometime--it does not run up the tree with its legs beneath its body, but holds them well out to the side.

  • Gliding 

    • The "flying" squirrels are actually gliders. The flap of skin along the flanks of the animal used for gliding is supported (when held out in "flight") by a cartilaginous rod extending from the wrist. The flattened tail is used as a rudder during the glide. Flying squirrels have soft pelage, which probably contributes to the quietness of the glide. 

  • Flying: Bats (Order Chiroptera) are the only mammals which truly fly. Note the patagium, or wing membrane; it is supported by greatly elongated digits, but the thumb remains small and bears a typical claw. The wing-supporting bones are pneumatic (hollow), as in birds, and their musculature is concentrated at the shoulder. (Examine the skeleton and preseved specimens to appreciate the massive chest region).

    • Patagium 

    • Uropatagium:  ("tail-membrane") that extends from the hindlimb to the tail. This not only increases the surface area that holds the bat in the air, but can also be used as a net (as can the wings) for capturing flying insects. 

  • Fossorial

    • The moles (Talpidae) are excellent examples of the specialization to a burrowing existence. The body is stocky and cylindrical, with the limb musculature molded in to the body outline. The head is pointed, and any protruding parts (eyes, ears) greatly reduced. The fur is modified such that the animal can move forward or backward without impediment. Run your finger back and forth along the short, dense pelage of a Scalopus, noting that it makes little difference--the fur lies flat in either direction. This is accomplished by having each hair taper to a point at its base; hence its junction with the skin is very flexible.