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Mammalogy > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Mammals predate dinosuars

A

TRUE

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2
Q

Synapsids are ______ mammals

A

Stem

NOT true mammals, ANCESTRAL to mammals

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3
Q

Cretaceous mammals

A

Pangea: Single giant land mass; super continent

Continents are separating in Cretaceous, still tenuous connections between continents

Much biotic interchange between the continents in Jurassic - sets the stage for mammal diversification

Flowering plants become dominant flora over evergreens and gymnosperms

Insects radiate with flowering plants in Cretaceous = insects important food sources for mammals

Dinosaur fauna begins to decline

Mammalian faunas begin to radiate

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4
Q

Are mammals synapsids?

A

YES

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5
Q

Mammal taxonomy

A 
Kingdom Animalia
 Phylum Chordata
  Subphylum Vertebrata
   Clade Amniota
    Superclass Tetrapoda
     Clade Synapsida
      Class Mammalia
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6
Q

Mammals are:

A 
Animals
Chordates
Vertebrates
Tetrapods
Amniotes
Synapsids
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7
Q

Sauropsida is _____ to synapsida; amniotes that are not mammals (turtles, reptiles, dinosaurs, birds)

A

Synapsida

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8
Q

Synapsid skulls

A

1 post-temporal opening

Compare to Diapsids: 2 post-temporal openings

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9
Q

Pelycosaurs are prime examples of

A

Synapsids

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10
Q

Function of temporal opening

A

Allows for enlargement of muscles associated with chewing

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11
Q

Synapsid Evolution

A

Single temporal fenestra

Retained ancestral tetrapod features of eye with poor color vision (probably nocturnal)

Splayed limb posture
-NO hair yet, no scales

Glandular skin without reptile-like scales

Probably oviparous (laid eggs)
-NO evidence of vivipary in early mammals
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12
Q

Synapsid Evolution: Early Innovations

A

Narrowing of the snout

3 vertebrae fused to hip bones
-Prior, it was 1 vertebra fused to MASSIVE hip bones

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13
Q

Pelycosaurs are an offshoot of the synapsid lineage; one radiating branch of the synapsis led to the pelycosaurs

A

Dimetrodon is a pelycosaur

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14
Q

Pelycosauria

A

Pelycosaurs are NOT the direct ancestor of mammals

“Sailbacks” of the late Paleozoic, but very few actually possessed sails

Generalized amniotes

“Non-therapsid synapsids”

No evidence of increased metabolic rate

Diverse group

  • Large specialized herbivores
  • Large carnivores with enlarged canines
  • -E.g. Dimetrodon
  • -Ate fish, amphibians
  • -Up to 3m long
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15
Q

One group of carnivorous synapsids led to the

A

Therapsida

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16
Q

Therapsida Evolutionary Innovations

A

Limbs positioned under the body
-No longer splayed posture

Deep acetabulum
-Acetabulum: Head of femur is ball, acetabulum is socket it fits into; very deep socket to accomodate this posture

Enlarged temporal opening = more muscles

Enlarged canines

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17
Q

Therapsida

A

Arose from common ancestor with pelycosaurs in mid-Permian (~275Mya)

Enlarged upper canines (other teeth roughly the same size)

Upright posture begins

New arrangement of muscles associated with chewing

Model of early synapsids

Expansion of post-temporal opening

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18
Q

Upright Posture

A

Axial musculature used for locomotion in ancestral vertebrates also used in rib ventilation

Mammals use limbs primarily for running, keep their trunk more rigid; bring limbs directly below the trunk

Dorso-ventral flexion of the vertebral column for a bounding gate -> quicker and more efficient locomotion

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19
Q

Appendicular Skeleton: Reptiles

A

Sprawling posture; limbs not in line with CoG (Center of Gravity), takes lots of energy

Many bones in pectoral and pelvic girdles, lots of cartilage

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20
Q

Appendicular Skeleton: Mammals

A

Improved posture; limbs in line with CoG; more energy efficient

Reduction in number of bones in girdles; ossified; stronger

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21
Q

Mammals are THERAPSIDS and SYNAPSIDS

A

MUST be to be a monophyletic group

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22
Q

“Therapsida” includes non-mammalian therapsids and mammals (it’s a monophyletic group, or clade)

A

Modifications indicating increased metabolic rate = probably had hair

Heavy, stumpy legs

Herbivores

  • Some large, heavy, slow-moving, herding
  • Some small and rodent-like

Carnivores

  • Some large, ferocious, cat-like
  • Some small, insectivorous, fox-like

Some HETERODONTY (tooth differentiation)

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23
Q

Tooth Morphology and Replacement: Ancestrally

A

Homodont: All teeth have the same shape (cone-shaped)

  • Mostly for gripping food
  • Don’t fit together well
  • Tend to wear down quickly
  • -Teeth did NOT fit together

Polyphyodont:
-Continuously replaced as needed

Used for gripping food; example of what ancestral condition looked like (alligators, crocs)

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24
Q

Tooth Morphology and Replacement: Derived…

A

Heterodont:

  • Differentiation into 4 types of teeth
  • Incisors (I) = cutting/nipping
  • Canines (C) = piercing
  • Premolars (P) = grinding/crushing/slicing
  • Molars (M) = grinding/curshing/slicing
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25
Q

Therapsida: Theriodontia

A

Particular branch of the Therapsids that give way to the Cynodontia

Late Permian to Early Triassic (~250Mya)

Gave rise to Cynodontia (“Non-cynodont theriodonts”)

Primarily carnivores

  • Built like wolves and coyotes
  • Canine teeth long and blade-like
  • Well-developed incisors
  • Small post-canine teeth (cheek teeth)
  • Incisors used to tear flesh

Some development of a secondary palate

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26
Q

Secondary palate

A

Purpose: Allows you to breathe with mouth closed; allows for SUCKLING

ONLY present in mammals

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27
Q

Therapsida: Cynodontia

A

Non-mammalian Cynodonts

late Permian to mid-Jurassic (~200Mya)

Reduction in body size
-Range from mouse-sized to dog-sized

Large temporal opening, large dentary bone

Heterodont, polyphyodont (teeth continuously replaced)
-Can differentiate canines from incisors, etc.

2 occipital condyles but no axis/atlas

  • Occipital condyles articulare with spinal column
  • Another character of mammals but NOT a synap

Vertebral differentiation, upright posture

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28
Q

Evolutionary transitions: Temporal Opening

A

Dimetrodon had a small temporal fenestra

Advanced therapsids had a larger inferior temporal fenestra

Mammals:

  • Lose post-orbital bar
  • Inferior temproal fenestra becomes temporal fossa
  • Pronounced zygomatic arch
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29
Q

Evolutionary Transitions: Lower Jaw

A

Enlargement of the dentary bone in the lower jaw

Ancestrally 7 bones in lower jaw; Articular and Quadrate bones form the jaw joint and the lower jaw used in feeding and sound transmission

Progressive reduction and loss of most elements of lower jaw

Dentary becomes entire lower jaw, jaw joint now dentary and squamosal bones, jaw used only for feeding in mammals

Different jaw joint than what we see in modern mammals

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30
Q

Evolutionary Transitions: Jaw Muscles

A

Masseter muscles with the same attachments as mammals was a cynodont innovation

Originate on the zygomatic arch and insert on the dentary - powerful adductors

  • Muscular sling enhancing control of the movements
  • Increased bite force
  • Focused force on point of the bite, not jaw joint

VERY powerful bite force; focused force on the point of the bite

Opening of fenestra for muscle attachment and migration of bones to form inner ear

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31
Q

Ear Evolution in Mammals

A

How do we know bones we hear with came from bones reptiles eat with? Transitions shown in fossil record; you start to see larger bones holding teeth

32
Q

Evolutionary Transitions: Jaw joints and Ear Bones

A

Early Amniotes:

  • Had 7 bones in the lower jaw, including the angular and articular
  • Jaw joint = articular and quadrate (birds and reptilians still use this jaw joint)
  • Stapes was already used in sound transmission from external ear, through middle ear, to inner ear
  • -Stapes = columella of other tetrapods

Mammals use a dentary squamosal jaw joint

The jaw was remodeled during the evolution of mammals from non-mammalian synapsids

Mammals:

  • Only dentary comprises the lower jaw
  • Jaw joint = dentary and squamosal
  • 2 bones that were formerly part of the jaw joint now incorporated into the middle ear- the articular and quadrate
33
Q

Character of TRUE Mammals

A

Lower jaw joint made of single bone (Dentary)

34
Q

Mammalian characters

A

3 middle ear bones
Dentary-squamosal jaw joint
Single jaw bone (dentary)

35
Q

Evolution of ear bones

A 
Stapes = columella
Incus = Quadrate
Malleus = Articular
36
Q

Grade

A

A collection of organisms that are similar by way of physiology and anatomy; NOT a formal taxonomic or phylogenetic designation

37
Q

Synapsid Grade of Evolution

A

They have a similar morphology

38
Q

Therapsid Grade:

A

Increased size of temporal fossa

39
Q

Cynodont grade:

A

Appearance of secondary palate, heterodont teeth

40
Q

Early mammal grade

A

Dentary-squamosal jaw joing, single lower jaw bone, 3 middle ear bones

41
Q

Increasing size of temporal fenestra

A

More jaw muscles = more food intake

Becomes temporal fossa

42
Q

Lower temporal bar becomes ________-

A

Zygomatic arch

Indicates large masseter muscle = more food; bows outward to allow more muscle

43
Q

Lower jaw and jaw joint

A

Dentary takes over and postdentary bones become co-opted for use in hearing

44
Q

Teeth

A

Greater specialization of teeth from homodont pelycosaurs to heterodont mammals

Polyphyodonty to diphyodonty

45
Q

Secondary Palate

A

Allows breathing and eating at the same time

None in pelycosaurs, present in mammals

Greater respiration rate

46
Q

Loss of parietal foramen

A

Pineal eye in pelycosaurs used for controlling temp behaviorally

Lost in Cynodonts

47
Q

Limb position from splayed to upright

A

More activity

Easier to breathe and run simultaneously

Reduction in girdles

48
Q

Shape of limb girdles

A

From Large ventral components to support sprawling to reduced components

Weight passes through limbs now

49
Q

Shape of feet

A

Long toes used as holdfasts for sprawling gait, reduced toes used more as levers in upright posture

50
Q

Loss of lumbar ribs

A

Presence of diaphragm = greater respiration

Thoracic and lumbars specialized

Reduced/lost ribs on cervical vertebrae

51
Q

Long tail in pelycosaur reflects movement by

A

Axial Flexion

Shorter tail in therapsids reflects upright posture and limb propulsion is used

52
Q

Mammaliformes: Morganucodonts

A

We have no evidence that live birth was a character of these early mammals

Most were shrew-like; had complete mammalian teeth, skull, and jaw articulation

First mammals had hair and mammary glands, laid eggs

Larger brains than contemperary cynodonts

Diphyodont with precise occlusion of the molars

Upper cheek teeth fit precisely into lower cheek teeth

53
Q

Tooth Morphology and Replacement

A

Diphyodont

  • Compare with polyphyodont
  • 2 sets of teeth
  • -Deciduous (I, C, P)
  • -Permanent (I, C, P, M)
  • Often become more efficient as they wear down

Diphyodonty arose around the same time as precise occlusion

54
Q

What is a mammal?

A

The essence of mammalian life is to be found in their endothermic (warm-blooded) temperature physiology, greatly enlarged brain, dentition capable of chewing food, highly agile, energetic locomotion, and so on. The organisms that achieved this grade of overall organization are deemed to be Mammalia, and consequently those characters that they possess are the defining characters of the group.

55
Q

Mammals exhibit increased:

A

1) Intelligence
2) Information gathering ability
3) Endothermy
4) Reproductive efficiency
5) Ability to obtain and use food

56
Q

What is a Mammal? Characteristics NOT preserved in fossils

A

External covering of hair (except in certain highly specialized groups)

Nourishment of young by milk produced by mother’s mammary glands

Four chambered heart (separation of blood flow to lungs – for reoxygenation – from circulation to rest of the body)*
-Birds CONVERGENTLY evolved 4-chambered heart

Muscular diaphragm (increased oxygen consumption)

Higher metabolic rates

Better vision, hearing, olfaction – cerebrum relatively larger

Enucleate erythrocytes: SYNAPOMORHPY (strictly mammalian)

Mammals have a larger brain

57
Q

What is a mammal? Characteristics Preserved in Fossils

A

Single lower jaw bone

Dentary-squamosal jaw joint

3 middle ear bones

Diphyodonty (*exceptions)

Heterodont dentition (*exceptions)

  • Precise occlusion
  • Complex crowns

Secondary bony palate
-Allows breathing when the mouth is closed

Ribs usually limited to thoracic region

2 occipital condyles

58
Q

Mammalian Characters

A

Single lower jaw bone (i.e. dentary)

Dentary-squamosal jaw joint

3 middle ear bones (incus, malleus, stapes)

59
Q

Occipital Condyle

A

Mammals have 2 occipital condyles (synap)

Articulates with first vertebrae; having 2 condyles allows mammals to move head in almost any direction

60
Q

All mammals have hair at some point in their lives

A

TRUE

Gray whales have whiskers as babies, armadilloes have hairs

61
Q

Hair has several functions

A 
Insulation
Protection from environment
Tactile snese (vibrissae/whiskers)
Cryptic coloration/camouflage
Warning coloration
62
Q

Sea otter fur is the ______ of any mammal

A

Densest

Consists of around 100000 haris per cm^2

63
Q

Camouflage: Seasonal Change

A

Arctic hare: Pelage/fur changes for season (bronw in summer, white in winter0

64
Q

Pelage variation

A

Confusion patterns (Zebra stripes), warning colors (skunk), camouflage, communication

65
Q

Why do Zebras Have stripes?

A

Hypotheses:

  • Stripes cause little convex air circulations right next to skin which would act as a cooling mechanism
  • Stripes are how zebras recognize one another
  • Type of cryptic coloration by confusing predators
  • Striped pattern protects against fly bites

Tested fly hypothesis: Put Zebra and horse skins in room; flies only landed on horse coat; supports hypothesis that stripes prevent bug bites

Protect against SMALL predators (flies), not large predators (lions, hyenas, etc.)

66
Q

Skin Glands: Sweat Glands

A

Produce sweat to cool via evaporative heat loss

Helps keep body temp in a neutral range

Eccrine sweat glands:

  • Thin sweat (watery)
  • NOT near hair follicles

Apocrine sweat glands:

  • Thick sweat (oily)
  • Near hair follicles
67
Q

Skin glands: Sebaceous Glands

A

Associated with hair follicles and secrete an oil (sebum) that keeps hair shaft moist and waterproof

Sebaceous glands that aren’t on hairs are found on the lips, penis, labia, minora, and nipples

Produce pheromones for signaling

68
Q

Skin Glands: Scent Glands

A

Either modified sweat or sebaceous glands

Modified for a variety of functions, usually intraspecific communications (Pheromones)

  • Predator deterrent (e.g. skunks)
  • Scent marking (e.g. deer)
  • Sexual communication (e.g. rodents)

Found in many locations on the body

69
Q

Skin Glands: Mammary Glands

A

Unique to mammals (SYNAP)

Specialized epidermal glands derived from SWEAT GLANDS

Glands send ducts up an elevated nipple or teat, adipose fat forms beneath the glands

Number and location vary among species

Mammary glands are derived from sweat glands

Sweat glands and sebaceous glands are types of epidermal glands

Varies from 2 (primates) to 13 nipples/teats

Adipose forms beneath the glands

Composition o milk varies by nutritional demand

Seal milk has more fat than terrestrial carnivore milk because seals need to store fat for insulation in cold water

70
Q

Axial Nipple

A

Nipple in armpit

Found in manatees

71
Q

Cistern

A

Where milk would collect

Found in cattle, goats (animals that produce a lot of milk)

72
Q

Lactation evolved ______ ability to give birth

A

BEFORE

73
Q

Monotremes evolved _____ of other lineages

A

Independently

74
Q

Composition of Milk

A

Water: 40-90%

Salts: 1-58%

Carbohydrates: 0-9%

Lipids: 1-52%

Protein: 4-12%

75
Q

Do male mammals lactate?

A

Males of 2 species of bats have been discovered to lactate

VERY small amounts of milk

Not clear if they are feeding young

Mammalogy (11 decks)

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