mammals - practical 2

Class Mammalia

warm-blooded amniotes defined by hair

hair

the defining external covering of mammals; three types are vibrissae

vibrissae

whiskers; modified sensory hairs found on the face; function as tactile receptors; extend sensory perception further from the body

underhair

the soft dense inner layer of mammal hair including wool fur and velli; primary function is insulation and warmth

guard hair

the coarser outer layer of mammal hair; provides waterproofing and protection; in porcupines modified into quills

three middle ear bones

a defining synapomorphy of mammals; the articular and quadrate bones common to all vertebrates are modified in mammals to form a chain that carries sound from the eardrum; allows acute hearing

mammary glands

glands in female mammals that produce milk for nursing young; defining trait of Class Mammalia

neocortex

the outer layer of the mammalian brain responsible for higher cognitive function; a defining trait of Class Mammalia

endothermy (warm-blooded)

mammals regulate their own body temperature internally through brain and circulatory system regulation; allows activity in a wide range of environmental temperatures

heterodont dentition

mammals have different types of teeth for different functions; the four types are incisors canines premolars and molars; dental formula is frequently defining for mammal identification and remains as a permanent record after death

incisors

front cutting teeth; in rodents they are a single pair that grows continuously with harder enamel on the front and softer dentine on the back resulting in a self-sharpening chisel edge

canine teeth

long pointed teeth used to capture hold and kill prey; characteristic of Order Carnivora; prominent in Mustelidae

premolars

teeth behind the canines used for shearing and crushing food

molars

the rearmost grinding teeth used for chewing and processing food

dental formula

the standardized count of each tooth type in a mammal; frequently used for species identification; remains after the body decomposes making it a permanent record

continuously growing incisors

a defining trait of Order Rodentia; incisors grow throughout life and must be worn down through use or they can pierce the skull; a gap called a diastema separates them from the cheek teeth

diastema

the gap between the continuously growing incisors and the cheek teeth of rodents; allows the animal to suck in cheeks or lips to shield mouth and throat from inedible material while gnawing

Infraclass Metatheria (marsupials)

mammals that give birth to live but incompletely developed young who complete development in a pouch called the marsupium; do not develop a complex true placenta; represented locally by the Virginia opossum

marsupium

the pouch on the abdomen of a female marsupial in which incompletely developed young complete their development and suckle

Infraclass Eutheria (placental mammals)

mammals that develop a complex true placenta; young complete development internally; the largest mammalian infraclass

Order Soricomorpha

shrews and moles; fossorial and semi-fossorial insectivores; characterized by pointed snouts

fossorial

adapted for digging and living underground; characterized by powerful forelimbs

multidirectional fur

fur that can lie in either direction; found in shrews and moles; facilitates movement in either direction through narrow underground tunnels

echolocation

the use of high-frequency sound pulses and their echoes to locate and identify objects; used by shrews and bats for navigation and prey detection

Eimer's organ

the fleshy star-shaped nose of the star-nosed mole consisting of 22 radiating tentacles; one of the most sensitive touch organs of any mammal; used to rapidly detect prey

Order Chiroptera

bats; the only flying mammals; wings are formed by a thin skin membrane called the patagium stretched between elongated finger bones and the body; possess a keeled sternum shared with birds for flight muscle attachment

patagium

the thin skin membrane forming the wing of a bat; stretched between elongated finger bones forelimbs hindlimbs and body; also present in flying squirrels as a gliding membrane

keeled sternum in bats

a structural feature shared with birds; provides an attachment point for the powerful flight muscles needed for powered flight

white-nose syndrome

a fungal disease that has caused massive population declines in bat species including the little brown bat since 2006; spread in part by human activity such as caving

Order Carnivora

carnivorans; defined by large canine teeth and five toes on the forefeet; includes raccoons mustelids skunks foxes and others

plantigrade stance

walking with the entire sole of the foot on the ground including the heel; seen in skunks bears raccoons and humans; contrasts with digitigrade stance where only the toes contact the ground

raccoon front foot adaptation

the front foot has a thin horny sensory layer that becomes pliable and more sensitive when wet; also possesses vibrissae above the claws; a large portion of the raccoon brain is devoted to processing tactile information from the hands

anal scent glands

glands present in many Carnivora especially Mustelidae; produce strong-smelling semiochemical secretions used for territory marking and mate finding

Family Mustelidae

a family within Carnivora; characterized by long slender fusiform body shape; prominent canines; anal scent glands; acute senses; delayed implantation; solitary and preferentially nocturnal; includes weasels mink marten fisher badger and others

fusiform body shape

the long slender streamlined body shape of mustelids; built for agility speed and maneuverability in tight spaces; allows them to swim through water snow soil and thickets

delayed implantation (embryonic diapause)

a reproductive strategy in Mustelidae where fertilized eggs are not immediately implanted in the uterus; implantation is delayed by many months to optimize timing of birth relative to environmental conditions

adaptive radiation

the evolution of ecological and phenotypic diversity from a common ancestor into a wide variety of types adapted to specialized modes of life; exemplified by Family Mustelidae which originated in Eurasia and diversified after crossing the Bering land bridge

habitat partitioning in Mustelidae

different mustelid species occupy distinct habitats; American badger is fossorial; American marten and fisher are semi-arboreal; American mink is semi-aquatic; weasels are terrestrial

Order Rodentia

rodents; defined by a single pair of continuously growing incisors; most with four toes on forefeet and five on hindfeet; the largest mammalian order

cheek pouches

expandable pouches inside the cheeks of chipmunks and some other rodents; used to transport large quantities of food to storage caches in burrows

beaver habitat modification

beavers are capable of creating and modifying their own habitat by constructing dams and lodges; one of very few non-human mammals to do so

beaver tail

large broad flat leathery scaled tail; used for steering and balance in swimming; serves as an alarm mechanism by slapping the water; stores fat for warmth

muskrat tail vs beaver tail

muskrat tail is long thin and laterally flattened and used for propulsion; beaver tail is broad wide and dorsoventrally flattened and used for steering balance and alarm

valvulate ears and nostrils

ears and nostrils with valves that can be closed underwater; found in beavers and muskrats; prevents water entry during diving

regional heterothermia

a condition in semi-aquatic rodents like beavers and muskrats where the feet and tail remain cooler than the core body; reduces heat loss to cold water

quills

modified guard hairs of the porcupine; tipped with tiny backward-facing barbs that expand in response to body heat; become firmly embedded in a predator and are pulled further in by normal muscle movements; loosely attached so easily detached from the porcupine

porcupine foot adaptation

naked soles covered with small pebbly-textured fleshy knobs; increases surface area and friction; provides keen sense of touch for climbing

Order Artiodactyla

even-toed ungulates; includes moose deer and related species; members of the deer family lack upper incisors and feed by shearing vegetation across sharp lower incisors with the tongue

antler

a branched bony structure formed as an extension of the frontal bone; seasonal and shed annually; covered with vascularized skin called velvet while growing; no blood supply once velvet is shed; found in moose and deer

horn

a permanent unbranched structure formed from a frontal bone covered with keratin; never shed; found in cattle sheep and goats

velvet

the vascularized skin covering a growing antler; supplies blood and nutrients during antler development; shed once growth is complete leaving the dead bony antler

hollow hair in moose

moose hair is hollow providing insulation; also increases buoyancy when swimming to feed on aquatic plants