Mammalogy Exam 1 Study Guide

Overview of what you need to know: Mammalogy evolution line and characteristics of each new group, a few mammalian major characteristics and diagnostic characteristic, orders Rodentia, Lagomorpha, Probiscidea, Sirenia, and Hyracoidea and their diagnostic/2 key characteristics and distribution, Rodentia and Lagomorpha families characteristics and distribution, how hair is classified, glands, antlers vs horns, movement terms, and heat/cold avoidance and resistance methods. The exam will be 8-10 short answer questions as well as matching terms (mainly movement terms) at the end.

Mammalogy Evolution Line: 1)Tetrapods (four-legged, amphibious) —> 2)amniotes (amniotic egg that can be on dry land) —> 3)Synapsida (single temporal opening) —> 4)Pelycosaur (heterodont teeth) —> 5)Therapsida (legs under body) —> 6)Cynodonts (secondary soft palate) —> 7)Basal/Stem Mammals (single dentary bone).

Major mammalian characteristics are dentary-squamosal jaw articulation/single dentary bone, mammary glands, secondary palate, epidermis with hair, diphyodont and heterodont dentition, endothermy, separate anal and urogenital openings, occlusion of cheek teeth, digastricus muscle lowers jaw, three-bone ear from old jaw bones, skeletal simplifications (fusion and lose ribs), sensory specializations, and two occipital condyles.

Mammal diagnostic is single dentary bone/dentary-squamosal jaw articulation.

Rodentia has a cosmopolitan distribution, 5 suborders (diagnosed by position of masseter muscles relative to infraorbital foramen), and has diagnostic characteristic of a single pair of ever growing incisors. Includes families Aplodontiidae, Sciuridae, Castoridae, Geomyidae, Heteromyidae, Erethizontidae, Echimyidae, Cricetidae, Muridae (9 we know).

Aplodontiidae is mountain beavers (single species), distribution is pacific northwest, has many ancestral features and prefers riparian habitats.

Sciuridae is squirrels/chipmunks/marmots/prairie dogs, diurnal herbivores, skull arched in profile, masseter on anterior zygomatic plate, locomotion and thermoregulation varies. Distribution is cosmopolitan.

Castoridae is beavers (two species), semiaquatic, highly insulative fur, ecological engineers. Distribution is north america and Eurasia. Diagnostic characteristic is deep zygomasseteric groove for masseter.

Geomyidae is gophers, fossorial, external fur-lined cheek pouches, small pinnae, fimbration between toes. Distribution is North America.

Heteromyidae is kangaroo rats and allies, many have desert adaptations like enlarged auditory bullae, elongated hind limbs. Nocturnal, herbivorous or granivorous, foot drumming and seismic communication. Distribution is New World.

Erethizontidae is New World Porcupines, barbed quills on much of body, robust skull, eat cambium layer in winter. Distribution is New World.

Echimyidae is nutria (tribe myocastorini), resemble beavers with rat tails, large, capable swimmers, native to S Amer but introduced to N Amer too.
Cricetidae is second largest mammal family, cosmopolitan distribution, new world mice and rats.

Muridae is largest mammal family, cosmopolitan, old world mice and rats, medial masseter passes through dorsal infraorbital foramen.

Lagomorpha is nearly cosmopolitan, 2 families (only need to know 1), dramatic cycles in north. Diagnostic characteristic is single pair or upper and lower incisors and peg like 2nd incisors.

Leporidae is rabbits and hares, have skull fenestration, cursorial adaptations, hypsodont teeth, is nearly cosmopolitan.

Glands are eccrine (sweat), apocrine (chemical, mainly interspecific), sebaceous (oil that nurtures hair/hair root), and scent (modified from sebaceous or apocrine, mainly intraspecific). Glands came from scales to fur, mainly for insulation but secondary is coloration. Mammary glands likely from modified sweat gland.

Hair is classified by growth and function. Growth is angora (continuous) or definitive (set length). Functional is vibrissae (whiskers), pelage (fur) with pelage divided into guard hairs (awns, spines), bristles (manes), wool (curly), and velli (fuzz/down). Most mammals molt every year. Disruptive coloration like zebras used for warning and communication.

Nails/hooves/claws: Nails and hooves are modified claws. Are all keratin based with claws being ancestral characteristic. Hooves mainly in ungulates while nails mainly in primates.

Antlers/Horns: antlers are made up of bone, always forked, always shed, almost always in only males. Horns are bony core with keratin sheath, never forked, rarely shed, and in both male and female. Both likely for predator defense and the antlers secondary for mating. Antler classic family is cervidae while horn classic family is bovidae.

Skull/Skeleton Integument: akinetic skulls (single moving skull, not in multiple pieces), secondary palate help suckle, large braincase, foramina, three middle ear bones, atlas and axis vertebrae let head swivel, thoracic vertebrae on upper back, lumbar vertebrae on lower back, sacral vertebrae in rump, caudal vertebrae for tail, simplification of skeletal elements for metabolism and movement, greater bone ossification (bones harden together into units), determinate bone size, shoulder girdle, clavicle may be reduced or absent.

Environmental adaptations: all mammals are endothermic, when in cold tend to be fusiform (cylindrical) to lower surface area to volume ratio, can survive cold/heat using either avoidance or resistance, avoidance can use foraging zone (layer under snow), change in activity level and times, fur insulation, smaller more rounded appendages or countercurrent appendages (move cold blood next to warm blood), larger body size, food hoarding, dormancy. Can use regional heterothermia (like legs colder than body), or temporal heterothermia which includes daily torpor (estivation in heat) and then seasonal torpor mechanisms like shallow hibernation (winter lethargy 5-7C below normal) and profound hibernation (2-5C temp, same as hibernaculum/burrow, only small can do this due to size let warm/cool quickly). Torpor is achieved by lowering metabolism, lowering O2/breath rate, lowering heartrate, and lowering temperature. Arousal can be for alarm or periodic (lick finger and put in air). Can also use brown adipose tissue around neck, thermogin help heat itself like electric blanket. In heat, water conservation also needed with heat resistance. Can concentrate urine with loops of henli, behavioral thermoregulation, head used to loose heat by nose cooling countercurrent that evap in nasal passages. Adaptive hyperthermia too, like camel. All of these have been avoidance, resistance can be shivering or raising/lowering BMR.

Proboscidea are elephants, 3 species, graviportal with columnar limbs, originate in Africa but current distribution is Africa and India, incisors become tusk-like, enlarged skull and reduced neck, elongated probiscus/trunk, anterior replacement of cheek teeth (conveyer belt, one tooth at a time), largest living terrestrial mammals, digitigrade, large ears, highly social.

Hyracoidea are hyraxes, 5 species, distribution is Africa and Middle East, incisors ever growing, feet mesaxonic (weight axis on 3rd/middle toe), diastema present, rabbit-sized, deep mandible, herbivores, scansorial, diurnal, polygynous.

Sirenia are manatees/dugongs/sea cows, 4 species, diagnostic characteristic is they are the only herbivorous marine/aquatic mammal, distribution is tropical ocean/coast worldwide, ballasts help hold position in water, valvular nostrils, nearly hairless, thick dentary, large middle ears, cheek teeth like slow conveyer belt, tail horizontal fluke, slow moving, little body fat (is why in tropics), long lived.

Terms-

Monotreme - means one opening, includes platypus and echidnas. BTW lay eggs.

Therian - placental mammals.

Eutherian - true placental

Metatherian - weak placental, marsupials.

Monophyletic - arise from common ancestor.

Oviparous - egg laying.

Viviparous - live bearing.

Laurasiatheria - mainly in or from northern hemisphere.

Afrotheria - mainly from or in Africa.

Amniotic egg - can be laid out of water, on land.

Anapsid - no temporal opening, amphibians/turtles.

Diapsid - two temporal openings, reptiles/dinos/birds.

Synapsid - one temporal opening, mammals.

Fossa - groove/depression (for jaw muscles).

Diphyodont dentition - two sets of teeth like baby and adult teeth.

Diastema - evolutionary gap in tooth placement.

Edentate - lack teeth (like ant eaters).

Cosmopolitan distribution - distributed worldwide.

Convergent evolution - non-related groups evolve similar adaptations.

Parallel evolution - related but spatially separated groups evolve similar adaptations.

Fossorial - live primarily underground.

Subterranean - live entirely underground.

Scansorial - rock dwelling.

Arboreal - tree dwelling.

Semi-aquatic - amphibious, often move between land and water, adapted to both land and water, example is beavers.

Aquatic - most adept in water but do land (like seals).

Marine - entirely in water.

Diurnal - live/move in daytime.

Nocturnal - live/move in nighttime.

Crepuscular - live/move at dawn and dusk.

Pinnae - external ear.

Fimbration - stiff hairs between digits, help dig.

Glissant - gliding.

Volan - flying.

Richochetal - jump/move in zig zag.

Granivory - herbivory type where only ear grains/seeds.

Saltitorial - jump/move in straight line.

Cursorial - run locomotion.

Ambulatory - walk.

Graviportal - long columnar legs movement.

Brachiation - use forelimbs to move through environment.

Plantigrade - move on soles of feet.

Digitigrade - move on digits.

Unguligrade - move on hooves.

Geophyte - eat underground, like naked mole rats and tubers.

Lustrous - fur laying in any direction.

Dipod - two feet

Boreal region - northern cold temperate forests.

Talus slope - gravely rock.

Hypsodont - high crown teeth, take longer to break down when eating plant material.

Angora - continuously growing hair.

Definitive - hair grows to a set length.

Vibrissae - whiskers.

Pelage - fur.

Velli - fuzz/down.

Akinetic skull - single moving skull that isn’t in multiple moving pieces.

Endothermic - regulate own body temperature via metabolism.

Ectothermic - get temperature mainly using environment.

Homeothermic - same temperature year round (like humans).

Heterothermic - can live/operate at multiple temperatures (like bears).

Thermoneutral zone - zone in which animal doesn’t have to actively do anything to retail/expel heat, metabolism is at normal rate.

Fusiform - cylindrical shape, like mammals in cold environments.

Thermal inertia - large body size results in less heat loss and lower metabolic rates.

Musth - elephant period of heightened aggression and sexual activity.

Hypothermia - temp below normal body temp.

Hibernaculum - den/crack/cave an animal hibernates in.

Estivation - heat version of daily torpor.

Alarm arousal - ambient temp drops beyond animal’s ability to compensate.

Periodic arousal - arousal in the absence of external cues, like licking finger and putting it in the air.

Adaptive hyperthermia - ability to tolerate long exposure to air temperatures higher than body temperatures.