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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
Therapsida: Theriodontia
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
26
Secondary palate
Purpose: Allows you to breathe with mouth closed; allows for SUCKLING ONLY present in mammals
27
Therapsida: Cynodontia
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
28
Evolutionary transitions: Temporal Opening
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
29
Evolutionary Transitions: Lower Jaw
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
30
Evolutionary Transitions: Jaw Muscles
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
31
Ear Evolution in Mammals
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
Evolutionary Transitions: Jaw joints and Ear Bones
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
Character of TRUE Mammals
Lower jaw joint made of single bone (Dentary)
34
Mammalian characters
3 middle ear bones Dentary-squamosal jaw joint Single jaw bone (dentary)
35
Evolution of ear bones
``` Stapes = columella Incus = Quadrate Malleus = Articular ```
36
Grade
A collection of organisms that are similar by way of physiology and anatomy; NOT a formal taxonomic or phylogenetic designation
37
Synapsid Grade of Evolution
They have a similar morphology
38
Therapsid Grade:
Increased size of temporal fossa
39
Cynodont grade:
Appearance of secondary palate, heterodont teeth
40
Early mammal grade
Dentary-squamosal jaw joing, single lower jaw bone, 3 middle ear bones
41
Increasing size of temporal fenestra
More jaw muscles = more food intake Becomes temporal fossa
42
Lower temporal bar becomes ________-
Zygomatic arch Indicates large masseter muscle = more food; bows outward to allow more muscle
43
Lower jaw and jaw joint
Dentary takes over and postdentary bones become co-opted for use in hearing
44
Teeth
Greater specialization of teeth from homodont pelycosaurs to heterodont mammals Polyphyodonty to diphyodonty
45
Secondary Palate
Allows breathing and eating at the same time None in pelycosaurs, present in mammals Greater respiration rate
46
Loss of parietal foramen
Pineal eye in pelycosaurs used for controlling temp behaviorally Lost in Cynodonts
47
Limb position from splayed to upright
More activity Easier to breathe and run simultaneously Reduction in girdles
48
Shape of limb girdles
From Large ventral components to support sprawling to reduced components Weight passes through limbs now
49
Shape of feet
Long toes used as holdfasts for sprawling gait, reduced toes used more as levers in upright posture
50
Loss of lumbar ribs
Presence of diaphragm = greater respiration Thoracic and lumbars specialized Reduced/lost ribs on cervical vertebrae
51
Long tail in pelycosaur reflects movement by
Axial Flexion Shorter tail in therapsids reflects upright posture and limb propulsion is used
52
Mammaliformes: Morganucodonts
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
Tooth Morphology and Replacement
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
What is a mammal?
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
Mammals exhibit increased:
1) Intelligence 2) Information gathering ability 3) Endothermy 4) Reproductive efficiency 5) Ability to obtain and use food
56
What is a Mammal? Characteristics NOT preserved in fossils
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
What is a mammal? Characteristics Preserved in Fossils
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
Mammalian Characters
Single lower jaw bone (i.e. dentary) Dentary-squamosal jaw joint 3 middle ear bones (incus, malleus, stapes)
59
Occipital Condyle
Mammals have 2 occipital condyles (synap) Articulates with first vertebrae; having 2 condyles allows mammals to move head in almost any direction
60
All mammals have hair at some point in their lives
TRUE Gray whales have whiskers as babies, armadilloes have hairs
61
Hair has several functions
``` Insulation Protection from environment Tactile snese (vibrissae/whiskers) Cryptic coloration/camouflage Warning coloration ```
62
Sea otter fur is the ______ of any mammal
Densest Consists of around 100000 haris per cm^2
63
Camouflage: Seasonal Change
Arctic hare: Pelage/fur changes for season (bronw in summer, white in winter0
64
Pelage variation
Confusion patterns (Zebra stripes), warning colors (skunk), camouflage, communication
65
Why do Zebras Have stripes?
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
Skin Glands: Sweat Glands
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
Skin glands: Sebaceous Glands
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
Skin Glands: Scent Glands
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
Skin Glands: Mammary Glands
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
Axial Nipple
Nipple in armpit Found in manatees
71
Cistern
Where milk would collect Found in cattle, goats (animals that produce a lot of milk)
72
Lactation evolved ______ ability to give birth
BEFORE
73
Monotremes evolved _____ of other lineages
Independently
74
Composition of Milk
Water: 40-90% Salts: 1-58% Carbohydrates: 0-9% Lipids: 1-52% Protein: 4-12%
75
Do male mammals lactate?
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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