Chapter
#9
–
Origin and
Radiation of
Tetrapods
(pg. 196 – 218)
*required reading for the
quiz next Monday
Will cover:
2nd half of amphibians
and 1st half of reptiles
Quizzes will be returned on Wednesday
Marine Iguana
Introduction to Amniotes
Origin and Radiation of Tetrapods:
Amniotes
Liss Amphibians
(early Carboniferous period ~290 mya)
(major radiation = Permian ~250 mya)
(extant amphibians)
Majority extinct by mid-Permian
Table 9.1
?
Temnospondyl
(aquatic)
Pages 206 - 211
X
?
?
?
Anthracosaur
(Terrestrial)
Lepospondyl
Batrachomorphs (“Frog form”)
Reptilomorph (“Reptile form”)
1) Amniotic egg
Stem Tetrapod (“four limbs”)
(late Devonian period ~ 360 mya)
Introduction to Amniotes
Amniotic Egg:
Functions as a
“self-contained pond”
Surrounded by shell:
1) Calcified / Rigid (birds)
2) Leathery / flexible
(reptiles – why?)
Extraembryonic Membranes:
1) Chorion: Respiratory membrane (gas exchanges freely across shell)
2) Allantois: Waste disposal sac; respiratory membrane
3) Yolk Sac: Stockpile of nutrients (also albumin…)
4) Amnion: Surrounds fluid-filled cavity; anti-dehydration / cushioning
Introduction to Amniotes
Origin and Radiation of Tetrapods:
Amniotes
Lissamphibians
(early Carboniferous period)
(major radiation = Permian)
(extant amphibians)
Majority extinct by mid Permian
Table 9.1
?
Temnospondyl
(aquatic)
Pages 206 - 211
?
?
?
Anthracosaur
(Terrestrial)
Lepospondyl
Batrachomorphs (“Frog form”)
Reptilomorph (“Reptile form”)
1) Amniotic egg
Stem Tetrapod (“four limbs”)
(late devonian period ~360 mya)
2) Waterproof skin
3) Costal ventilation of lungs
Introduction to Amniotes
Amniotes Sub-divided by Temporal Fenestrations (aka “holes in head”):
Function: Provide room for muscles to bulge
Evolution: Initially offer strong attachment points for jaw closure muscles
• Allow for static pressure delivery (clench jaws…)
Turtles (extant)
Anapsids (0)
Mammals (extant)
Synapsid (1)
Amniotes
(early Carboniferous period ~290 mya)
(major radiation = Permian ~250 mya)
Reptiles / birds (extant)
Diapsid (2)
Introduction to Amniotes
Turtles
Origin and Radiation of Tetrapods:
Mammals
Anapsids
Synapsids
Lissamphibians
Reptiles / Birds
Diapsids
Amniotes
Majority extinct by mid Persian
Table 9.1
?
Temnospondyl
(aquatic)
Pages 206 - 211
?
?
Lepospondyl
Batrachomorphs (“Frog form”)
Anthracosaur
(Terrestrial)
Reptilomorph (“Reptile form”)
Stem Tetrapod (“four limbs”)
(late devonian period)
?
Introduction to Amniotes
Warm - Blooded
Cold - Blooded
Temperature varies dramatically in
terrestrial environment ( heat capacity)
Too hot = death
Too cold = incapacitation
Terrestrial tetrapods: Body temp. > Ambient temp. ( heat conductance)
Average
Body Temp..
(active part
of day)
Snakes
Lizards
Mammals
Birds
28 - 34
33 - 38
33 - 38
40 - 41
(C)
• Benefits of higher temperature:
1) Optimal organism performance
(Humans = 37)
Introduction to Amniotes
Effect of Temperature on Performance – Garter Snake:
Introduction to Amniotes
Warm - Blooded
Cold - Blooded
Temperature varies dramatically in
terrestrial environment ( heat capacity)
Too hot = death
Too cold = incapacitation
Terrestrial tetrapods: Body temp. > Ambient temp. ( heat conductance)
Average
Body Temp..
(active part
of day)
Snakes
Lizards
Mammals
Birds
28 - 34
33 - 38
33 - 38
40 - 41
(C)
• Benefits of higher temperature:
1) Optimal organism performance
2) Aid in digestion (accelerates digestion / increases efficiency)
3) Increase embryonic development (viviparity)
4) Reduce bacterial growth (behavioral fever)
(Humans = 37)
Introduction to Amniotes
Thermoregulation = Regulation of body temperature
All endotherms are homeotherms but
not all homeotherms are endotherms!
• Heat Source = Chemical reactions of metabolism (Endothermy)
• Homeothermy = Maintenance of a constant body temperature
• Heat Source = Environment (Ectothermy – Ancestral form of thermoregulation)
• Poikiothermy = Wide variation in body temperature (in response to environment)
Thermal Energy Exchange:
(Environment  Organism)
INPUTS
1) Solar Energy Input (visible light / infrared)
A) Direct Solar Radiation
B) Reflected Solar Radiation
2) Convection (heat transfer from air)
3) Conduction (heat transfer from surface)
4) Metabolic Heat Production (trivial…)
Introduction to Amniotes
Thermoregulation = Regulation of body temperature
All endotherms are homeotherms but
not all homeotherms are endotherms!
• Heat Source = Chemical reactions of metabolism (Endothermy)
• Homeothermy = Maintenance of a constant body temperature
• Heat Source = Environment (Ectothermy – Ancestral form of thermoregulation)
• Poikiothermy = Wide variation in body temperature (in response to environment)
Thermal Energy Exchange:
(Environment  Organism)
OUTPUTS
1) Convection (heat transfer to air)
2) Conduction (heat transfer to surface)
3) Evaporation (heat vaporizes water)
Heat of Vaporization High
By evaporating 1 g of water,
~ 500 grams of tissue cools 1° C
Introduction to Amniotes
Thermoregulatory activities occupy considerable portion of ectotherm’s time:
Behavioral Thermoregulation Techniques:
1) Alternate between sunlight and shade
• Basking: Deliberately expose body to sunlight
• spread ribs; lie perpendicular to sun
• contract ribs; lie parallel to sun = 6x decrease
• Burrows allow for escape from extreme heat
2) Change skin color
• Dark = Light (heat) absorption
• Light = Light (heat) reflection
• Results from dispersion of
melanin in melanophores
• Turtles limited to basking / burrows
• Shell limits skin color
• If temperatures too extreme:
• Too hot = estivate
• Too cold = bruminate (“hibernate”)
Heat up to 75% faster when dark
Introduction to Amniotes
Variables affecting thermoregulation:
1) Body Size:
• Small bodies = heat / cool more rapidly
• Heat instability (… but find shade easily)
• Large bodies = heat & cool more slowly
• More heat stable (… but may be hard to find shade)
2) Body Shape:
• Long skinny bodies (e.g., snakes):  surface area to volume ratio
• Lose / gain heat much faster (than lizards)
• How to deal with it:
1)  mean active body temperature (avoid thermal maximum temperature)
2) Behavioral adaptations:
• Coil body to conserve heat when cold
• Minimize expose when basking (e.g., tail / abdomen)
• Facultative (optional) Endothermy: Endothermy “used” when necessary
• Brooding python: shiver to  temperature for incubation
Introduction to Amniotes
Ectothermy is as Effective as Endothermy!
LateEarly
Summer
Spring
Summer
& Fall
Active
Active
Activeevery
31hrs
hr 2/–643days
days
Otherwise
Otherwise
Otherwise
above
in
in burrow
burrow
ground
1) Ectotherms in Deserts:
• Desert = potential loss of water > input of water via precipitation (not always hot…)
• Ectotherm benefit =  metabolic rate (alleviate scarcity of food / water)
• Ectotherm problem = Easy to overheat / freeze (difficult to “stablize”)
A) Reptiles (example = Tortoise)
• Rely on burrow retreats & hibernation to survive conditions
Annual succulent
plants
Seedlings
Grasses
Thunderstorms (= water)
Winter Rains
Low
metabolic
rate
Introduction to Amniotes
Ectothermy is as Effective as Endothermy!
1) Ectotherms in Deserts:
• Desert = potential loss of water > input of water via precipitation (not always hot…)
• Ectotherm benefit =  metabolic rate (alleviate scarcity of food / water)
• Ectotherm problem = Easy to overheat / freeze
• Amphibians (example = Spadefoot Toad)
• Permeable skin / high rates of water loss not conducive to desert organisms
• Survival = Long period of hibernation (~ 10 months / year)
Osmotic gradient
• Construct burrow ~ 60 – 90 cm deep (~ 2 – 3 ft.)
pulls H2O into frog
• Enter burrow when soil relatively moist (~ September)
High
• Emerge when seasonal rains return (~ June and July)
Low
Introduction to Amniotes
Ectothermy is as Effective as Endothermy!
2) Ectotherms Sub-Zero Conditions:
• Experience freezing conditions on seasonal (latitude) or daily (altitude) basis
• Solution: 1) Super-cooling body (synthesizing anti-freeze agents) (glycoproteins)
2) Tolerate freezing via mechanisms preventing damage to tissues
Mountain Spiny Lizard
High altitude - daily
Fluids = high osmolality
-5.5 ºC
Painted Turtle Hatchlings
High latitude - seasonal
Skin = Ice crystal barrier
-8 ºC
Wood Frog
High latitude - seasonal
Extracellular fluid freezes;
cells do not (lethal)
Glucose = cryoprotectant
-3.0 ºC
Gray Tree Frog
High latitude - seasonal
Extracellular fluid freezes;
cells do not (lethal)
Glycerol = cryoprotectant
-3.0 ºC
Reptiles
Cladogram of Tetrapods:
Amniotes
Sauropsids (“reptile-like appearance” - Greek)
Diapsids
Reptiles
Turtles (13 families; ~ 280 species) :
Evolution / Diversity:
• First appearance in fossil record = Late Triassic (~ 230 mya)
Relative lack of diversity in life histories
Order: Testudines (“testu-” = shell)
• Cosmopolitan distribution
• Not high latitudes / altitudes
North American = 5 of 13 families
• Temperate regions = greatest diversity (why?)
• SE United States (Emydidae)
• SE Asia (Bataguridae)
Reptiles
Turtles (13 families; ~ 280 species) :
Morphology:
1) Shell (Continues to grow throughout life)
Snapping
Turtle
• Carapace (= dorsal shell; fused to vertebrae); Plastron (= ventral shell; may be hinged)
• Shell morphology reflects ecology of different species:
High-domed, rigid shell
(Terrestrial – non-agile)
Reduced, flexible shell
(Terrestrial – agile)
Stream-lined shell
(Aquatic)
2) Skull
Larger muscles = powerful bite
• Anapsid; no temporal fenestrae
• Emargination may occur (= removal of skull bones from posterior margins of skull)
• Keratinized Beak (loss of teeth – works well for slicing vegetation)
• Keratin is ever-growing; replaceable; can be serrated & sharp
Reptiles
Turtles (13 families; ~ 280 species) :
Reproduction:
No parental care
• All are oviparous (nest dug in ground / on surface)
Yellow-bellied
Slider
• Temperature-Dependent Sex Determination
♀♀
%♀
♂♂
Cold
(Intermediate temp. = hatchlings of both sexes)
e.g., marine turtles
Hot
♀♀
%♀
♂♂
Cold
Primary Pattern
♂♂ lower temp.; ♀♀ at higher temp.
Hot
Alternative Pattern
♀♀ lower / higher temp.; ♂♂ at intermediate temp.
e.g., snapping turtles
What is the ecological advantage to this?
Temperature may vary between nests and within a single nest
Moisture levels may also affect sex determination & size of offspring (wetter = larger)
Reptiles
Turtles (13 families; ~ 280 species) :
1) Cryptodires (“hidden neck”; 10 of 13 families)
• Retract head by bending neck in vertical “S” shape (Specialized flexible neck vertebrae)
• Laurasian distribution early; radiated later into Southern Hemisphere
Snapping Turtles
Family: Chelydridae
Softshell Turtles
Family: Trionychidae
Mud Turtles
Family: Kinosternidae
2) Pleurodires (“side neck”; 3 of 13 families)
• Retract head by bending neck horizontally (primitive design)
• World-wide distribution early; now only found in Southern Hemisphere
Austro-American Side-necked Turtles
Family: Chelidae
Afro-American Side-necked Turtles
Family: Pelomedusidae
Turtles
Painted Turtle (Chrysemys picta):
Habitat:
• Quiet, shallow water (e.g., pond, lake, stream)
• Northern, cool temperate distribution
• Diurnally active
Reproduction:
• Mating occurs primarily in spring / early summer:
• ♂ swims backward in front of female
• Strokes cheek / chin with claws
• ♀ sinks to bottom when ready to mate
• Male hangs onto carapace with claws
• ♀ lays 5 – 8 eggs in early summer (nest = sandy bank)
• ♀ often uses same next year after year
• Water from bladder seals nest opening / moistens eggs
• No parental care
Family: Emydidae
Turtles
Painted Turtle (Chrysemys picta):
Growth / Maturation:
• Eggs hatch in ~ 60 days (early fall)
• Far north, young over-winter in natal nest
• Survive by  plasma osmolarity (“antifreeze”)
• Dig themselves out of nest (group effort)
Family: Emydidae
• Sexual Maturation ~ 2 – 5 years
• Life Span ~ 20 – 30 years
Oregon:
Threatened
(~ 2000 ind.)
Western
Pond Turtle
(Clemmys marmorata )
Turtles
Desert Tortoise (Gopherus agassizii):
Habitat:
• Severe desert (e.g., Mohave / Sonoran)
• Need water source (canyons / river washes)
• Diurnally active (except during hottest season)
• Build burrows to escape hottest / coldest weather
• Often colonial (den = 10 – 15 individuals)
Reproduction:
• Mating occurs primarily in spring / early summer:
1) ♂ expand range (wander in circles grunting)
2) May meet other ♂
• Head bob / visual & pheromonal signals
• Joust until one male loses / tires and leaves
Family: Testudinidae
Turtles
Desert Tortoise (Gopherus agassizii):
Habitat:
• Severe desert (e.g., Mohave / Sonoran)
• Need water source (canyons / river washes)
• Diurnally active (except during hottest season)
• Build burrows to escape hottest / coldest weather
• Often colonial (den = 10 – 15 individuals)
Reproduction:
• Mating occurs primarily in spring / early summer:
1) ♂ expand range (wander in circles grunting)
2) May meet ♀
• Head bob / visual & pheromonal signals
(What is the advantage in this type of advertisement?)
• Male bites head / legs / carapace & mounts
• Oviparous – Deposit 1 – 14
eggs in shallow nest
• Wet eggs with water
from urinary bladder
• No parental care
Family: Testudinidae
Turtles
Desert Tortoise (Gopherus agassizii):
Growth / Maturation:
• Eggs hatch in 70 – 120 days
• Young break out using egg tooth (lost)
• Yolk sac supplies nutrients after hatching
• Shells soft (5 years to fully develop)
Family: Testudinidae
• Sexual Maturation ~ 14 - 20 years
• Life Span ~ 60 - 100 years
Turtles
Green Turtle (Chelonia mydas):
Habitat:
• Tropical / sub-tropical - Aquatic
• Shallow lagoons / bays along coast & islands
• Particular to sandy beaches
Migration: Adults = herbivores; Young = omnivores
• Feeding grounds not ideal breeding grounds
• May migrate 1000’s of kilometers
• Major nesting sites = Caribbean & Atlantic
• ♀ return to natal beaches:
Family: Chelonidae
• Magnetic “compass”
• Chemosensory (odor plume of shore)
Reproduction:
• Mating may occur year round (tropics…)
• ♀ & ♂ migrate to nesting location to mate
• ♀’s will mate with multiple partners (store sperm)
• Courtship = nudging / biting
• internal fertilization
♂ = Every year
♀ = Every 2 – 4 years
Turtles
Green Turtle (Chelonia mydas):
Oviparity:
• ♀ lay eggs at night
• Uses hind legs to dig out nest in sand
• Must be above high tide mark
• ~ 100 eggs / nest (2 – 7 nests / female) @ different locations
• No parental care (nest covered & left)
Family: Chelonidae
Growth / Maturation:
• Eggs hatch after ~ 6 – 8 weeks
• Hatchling wait under surface until sand cools (most @ night)
• Emerge in mass (Anti-predator)
• Attracted to bright light (= moon)
• Swim into waves (tactile)
• Only 1 – 2% survive first year
• Sexual Maturation ~ 25 - 50 years
• Life Span ~ 80 - 100 years
Reptiles
Sphenodons: (1 family; 2 species)
Evolution / Diversity:
• First appearance in fossil record = Late Triassic
Diverse group during mesozoic
Order: Rhynchocephalia
(“beak head”)
• Found on ~30 islands off coast
of New Zealand
Mainland decimated – human arrival
Tuatara
“Spines on back” - Maori
Reptiles
Cladogram of Tetrapods:
Amniotes
Sauropsids (“reptile-like appearance” - Greek)
Diapsids (“two arches” - Greek)
Lepidosaurs
Squamates (‘scaly ones”)
Lepidosaurs (“scaled reptiles”):
• Primarily terrestrial tetrapods
• Scaly skin; impermeable to water
• Epidermis shed (intervals)
• Transverse cloacal slit
Reptiles
Sphenodons: (1 family; 2 species)
Morphology:
Unique Features:
No external ear opening
No copulatory organs
Order: Rhynchocephalia
Teeth fused to jaw bone
(“beak head”)
Habitat:
• Nocturnal (cool, foggy nights); lowest optimum body temp. of reptiles (~ 6 – 16 ºC)
• Will bask in sunlight during day
• Utilize burrows – may share with nesting birds; both sexes territorial
Diet:
• Feed on small birds; bird eggs; arthropods – use shearing action (2 top / 1 bottom)
Reproduction:
• Maturity ~ 15 – 20 years; lays 5 – 18 eggs once every 4 years
• Mating = autumn (~ Feb)
• Egg-laying = spring (~ Nov); 12 – 15 month incubation
• Lifespan = ~ 50 – 100 years
Believed to be longest incubation
period for reptiles
Reptiles
Cladogram of Tetrapods:
Amniotes
Sauropsids (“reptile-like appearance” - Greek)
Diapsids (“two arches” - Greek)
Lepidosaurs
Squamates (‘scaly ones”)
Age?
Reptiles
Squamate Characteristics:
1) Determinant Growth: Animals reach mature size and stop growing
• Epiphyseal plates (long bones) ossify at maturity (but see snakes…)
• Evolutionary pressure = dietary constraints (small size = ready capture of insects)
2) Modified Diapsid Skull: Loss of lower temporal arch(s) (aids cranial kinesis)
• Lizards = Loss of lower temporal arch
• Upper / lower jaw close in parallel (teeth perpendicular to prey)
• Snakes = Loss of upper & lower temporal arch
• Increased gape size; left / right sides of jaws move separately (“walk” prey in)
Lizard
Tuatara
Snake
Reptiles
Major Groups of Squamates:
Squamates
Iguania
Scleroglossa
(“hard tongue”)
Simple, fleshy,
muscular tongue
Iguanas
Chameleons
Snakes
Geckos
Skinks
Snake Evolution:
1) Fossorial Adaptation Hypothesis
• Loss of limbs = moving in vegetation / soil
2) Marine Adaptation hypothesis
• Loss of limbs = streamline form in water
Pachyrhachis problematicus
3ft long; visible rear legs (~ 1”)
• Both support loss of
acute vision…
Reptiles
Lizards: (~ 17 families; ~ 4800 species)
Evolution / Diversity:
• First appearance in fossil record = Jurassic
Systematics continually in flux…
Order: Squamata
(“Scaly ones”)
• Cosmopolitan (except Antarctica)
• Low  high altitudes
• Australia = greatest # of species
North American = 8 of 17 families
Texas has highest
United States diversity…
Reptiles
Lizards: (~ 17 families; ~ 4800 species)
Lizard Design:
• Small size (80% < 20 grams; determinate growth / insectivore)
• Larger lizards primarily herbivores (but see monitors – e.g., Komodo dragon)
• Legs – but leglessness does exist
• Believed independently derived (~ 60x in many families)
Usually retain eyelids / ear openings
Eastern
Glass Lizard
• Tail Autotomy
• Anti-predator defense; sacrifice tail for escape
• Muscles segmented; vessels constrict
• Tail can re-grow; energetically expensive
Western
Skink
Foraging Strategies:
1) Iguania = primarily sit & wait species
2) Scleroglossa = Widely foraging species
Reptiles
Foraging Strategies - Lizards:
Characteristic
Sit & Wait Strategy
Widely Foraging
Movements per hour
Few
Many
Sprint Speed
Low
High
Prey Type
Mobile / Large
Sedentary / Small
Prey Mass / Day
Low
High
Foraging Cost / Day
Low
High
Body Form
Stocky / Short tail / Wide mouth
Slim / Long tail / Narrow mouth
Color Marking
Blotchy / Cryptic
Longitudinal Stripes
Vision
Excellent
Poor
Tongue-flick Rate
Low
High
Home Range Size
Small
Large
Yes
No
Territorial
Escape Predation
Camouflage / Stop moving
Run like ‘ell
Primary Predator Type
Widely Foraging Predator
Sit & Wait Predator
Squamates
Foraging Strategies - Lizards:
1) Iguania = Primarily sit & wait species (or vegetarian…)
• Galapagos Islands: Raft over from South America?
• Short, blunt snouts; laterally compressed tails
• Feed on marine algae (dive to rocky bottom)
• Can only withstand marine temperature for ~ 20 minutes
• Salt glands remove excess salt from body
Iguanidae
(Example: Marine Iguana)
Squamates
Lizards: (~ 17 families; ~ 4800 species)
1) Iguania = Primarily sit & wait species (or vegetarian…)
• Highly specialized for arboreal lifestyle
• Zygodactylous feet; large claws
• Prehensile tail (body stabilization)
• Independently mobile eyes; prey / predator identification
• Capture prey with projectile tongue
Chamealeonidae
(Example: Chameleon)
Specialized Hyoid Apparatus
Squamates
Lizards: (~ 17 families; ~ 4800 species)
2) Scleroglossa = Widely foraging species
• Spend majority of time roaming home range (~ 2 km2)
• Uses scent to detect prey
• Ambush predators (can run down…)
• Saliva = ~ 50 strain of bacteria; single bite kills (infection)
• Larger prey – wait until infection takes over…
Varanidae
(Example: Komodo Dragon)
Pheromone!
Dominance
Feeding
Hierarchy…
Squamates
Lizards: (~ 17 families; ~ 4800 species)
2) Scleroglossa = Widely foraging species
Van der Waals Forces:
Weak attraction between molecules
• Arboreal; large, specialized toe pads
• Transverse lamellar scales (setae)
• Grip = Van der Waals forces
• Hunt visually – keyed to movement
Gekkonidae
(Example: Gecko)
Reptiles
Lizards: (~ 17 families; ~ 4800 species)
Reproduction:
• Both oviparous and viviparous (oviparous appears ancestral…)
Costs:
• Lower reproductive output (clutch size)
Temperature-dependent
sex determination present
• Female agility reduced
Benefits:
• Control temperature of embryos
Vivipary common in skinks
• Parthenogenesis: All female species; do not require fertilization of eggs (asexual…)
• Particularly widespread in Teiidae
Mating behavior still observed…
Post egglaying
 Progesterone = Male behavior
 Estrogen = Female behavior
Acting out ritual = higher fecundity
Many parthenogenetic species
result from hybridization
Desert Grassland
Whiptail Lizard
Lizards: (~ 17 families; ~ 4800 species)
Representative Iguania Families of North America:
Iguanidae
Polychrotidae
(Iguanas – SW United States)
(Example: Chuckwalla)
(Anoles – SE United States)
(Example: Anoles)
• Larger lizards
• Arboreal (simplified setae)
• Primarily herbivores
• Brightly-colored dewlaps
• Oviparous
• Extensively researched…
Lizards: (~ 17 families; ~ 4800 species)
Representative Iguania Families of Oregon:
Phrynosomatidae: (example = Desert Horned Lizard)
Habitat:
• Arid regions; sparse vegetation / loose soil
• Bury to avoid predation / estivate
• Diet: Primarily ants
Anatomy:
• Flat, short bodies / tails
Cool factoid:
Squirt blood from
eyes In defense…
• Cryptic coloration
Reproduction:
• Early summer breeding
• Oviparous
• 2 – 16 eggs; high infant mortality
Growth / Maturation:
• Hatch ~ 1 month
• Sexual Maturation ~ 2 years
• Life Span = 5 – 8 years
Spiny Lizards:
Coast to coast – United States
Lizards: (~ 17 families; ~ 4800 species)
Representative Iguania Families of Oregon:
Crotaphytidae: (example = Great Basin Collared Lizard)
Habitat:
• Arid regions; sparse vegetation / loose soil
• Extreme heat tolerance; bask at mid-day
• Diet: Insects / small lizards
Anatomy:
• Large head / bulky body / long-limbed
Collared / Leopard Lizards:
South Central United States
• Can run on hind legs when startled
Reproduction:
• Early summer breeding; ♂♂ territorial
• Oviparous
• 3 – 7 eggs in burrow
Growth / Maturation:
• Hatch ~ 2 – 3 month
• Sexual Maturation ~ 2 years
• Life Span = ~ 10 years
Will not hesitate
to bite when
captured…
Lizards: (~ 17 families; ~ 4800 species)
Representative Scleroglossa Families of North America:
Anniellidae
(Legless lizards – SW United States)
(Example: California Legless Lizard)
Gekkonidae
(Geckos – SW United States)
(Example: Banded Gecko)
Xantusiidae
(Night lizards – SW United States)
(Example: Desert Night Lizard)
• Complete limb loss
• Tail autonomy
• Fossorial; rarely on surface
• Viviparous
• Arboreal (complex setae)
• Nocturnal
• Oviparous
• Vocalize (“chirp”)
• Primarily nocturnal
• Lack eyelids
• Parthenogenetic species
• Viviparous
Fat
storage
Lizards: (~ 17 families; ~ 4800 species)
Representative Scleroglossa Families of North America:
• Stout; short, blunt tails
Helodermatidae
(Gila Monster – SW United States)
(Example: Reticulate Gila Monster)
• Only venomous lizards
• Chew to inoculate
• Widely foraging
Diet = Eggs / birds / rodents / lizards
Lizards: (~ 17 families; ~ 4800 species)
Representative Scleroglossa Families of Oregon:
Anguidae: (example = Northern Alligator Lizard)
Habitat:
• Coniferous forests; only coastal lizard species
• Tolerant to cool, damp environments
• Diet: Insects / slugs / worms
Anatomy:
• Elongated body; short legs
Alligator Lizards:
Western / Eastern United States
• Distinct lateral fold
Reproduction:
• Late spring breeding
• Oviparous; females nest guard
• 2 - 6 eggs
Growth / Maturation:
• Hatch ~ 3 months
• Sexual Maturation ~ 3 years
• Life Span = ~ 5 – 10 years
Tail autonomy
Lizards: (~ 17 families; ~ 4800 species)
Representative Iguania Families of Oregon:
Scincidae: (example = Western Skink)
Habitat:
• Dry, oak woodlands; coniferous forests
• Sunny, grassy openings
• Diet: Insects / worms (adults = cannibalistic)
Anatomy:
• Vibrant blue tail (younger individuals – tail autonomy)
• Breeding season: chin / sides = reddish orange
Reproduction:
• Late spring / Early summer breeding
• Oviparous (only NW species to guard eggs entire incubation)
• 2 - 10 eggs
Growth / Maturation:
• Hatch ~ 2 month
• Sexual Maturation ~ 3 years
• Life Span = ~ 5 – 7 years
Skinks:
Cosmopolitan – United States
Lizards: (~ 17 families; ~ 4800 species)
Representative Iguania Families of Oregon:
Teiidae: (example = Western Whiptail)
Habitat:
• Desert dweller (sagebrush = cover…)
• Prefer open ground (foraging / running)
• Diet: Insects / other lizards
Anatomy:
• Elongated body; long tail (2x body length)
• Powerful rear legs; narrow, pointed head
Reproduction:
• Early summer breeding
• Oviparous
• 2 - 4 eggs
Growth / Maturation:
• Hatch ~ 1 month
• Sexual Maturation ~ 2 years
• Life Span = ~ 7 – 9 years
Whiptail Lizards:
Cosmopolitan – United States
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Evolution / Diversity:
• First appearance in fossil record = Cretaceous
Relationship of snakes to lizards uncertain…
Order: Squamata
(“Scaly ones”)
• Cosmopolitan (except Antarctica)
• Low  high altitudes
• South America = greatest # of species
North American = 5 of 15 families
2/3 of all snake species
located in family Colubridae
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Snake Design:
• Long, slender body
• Zygophenes = interlocking supports between vertebrae
• Legless
• Boas / Pythons retain leg remnants (cloacal / pelvic spurs – used in reproduction)
• Wide, ventral scutes; “braces” to propel body forward:
Serpentine Locomotion
Rectiliinear Locomotion
(e.g., garter snake)
(e.g., Anaconda)
Concertina Undulation
Sidewinding Locomotion
(Used in tight places)
(Desert-dwelling snakes)
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Snake Design:
• Well-developed vomeronasal organ (opens roof of mouth; separate from nasal cavity)
• Forked tongue picks up chemicals
• Tongue tips enter paired pits (directionality)
• Relatively poor vision
• Eyelids fused – form transparent spectacle; lack fovea = poor image quality
• External ear canal / tympanum absent (no airborne sound detection)
• Detect ground vibrations via lower jaw
Foraging Strategies:
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Snake Design:
• Well-developed vomeronasal organ (opens roof of mouth; separate from nasal cavity)
• Forked tongue picks up chemicals
• Tongue tips enter paired pits (directionality)
• Relatively poor vision
• Eyelids fused – form transparent spectacle; lack fovea = poor image quality
• External ear canal / tympanum absent (no airborne sound detection)
• Detect ground vibrations via lower jaw
Foraging Strategies:
• Specializations to tackle large prey w/o injury:
1) Constriction
• Body coils used to immobilize / kill prey (does NOT crush prey to death!)
• After each breath of prey, coils tightly slightly to take up slack
• Hypotheses for why death occurs: 1) Suffocation
2) Heart stops ( internal pressure)
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Foraging Strategies:
1) Constriction
2) Venom (Fang = Enlarged tooth associated with some type of venom gland)
• Benefits: 1) Species able to attack larger, more dangerous prey safely
2) Speeds up digestion (prey’s tissue breaks down more rapidly)
3) Defense against larger predators (?)
• Types of Toxins:
A) Necrotic Toxins (digestive enzymes attack cell structure / organelles)
Slow Death
tissue destruction
Hemorrhaging - shock
Fast Death
Respiratory Paralysis
Heart Stoppage
B) Hemorrhagic Toxins (proteases that disrupt blood vessel walls)
• Spreads slowly via lymphatic circulation
C) Neurotoxins (Bind to ACh receptors / block ACh receptors)
• Parylysis skeletal / cardiac muscle (moves rapidly in blood)
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Foraging Strategies:
• Categories of Snakes: (based on fang structure):
Boas / Pythons
1) Aglyphous (“No Knives” = Fangless)
• Teeth small, sharp, and highly re-curved
• Snake bites  hangs on  swallows
2) Opisthoglyphous (“Rear Knives” = Rear-fanged)
• Fangs solid / grooved (tilt maxilla to erect fangs)
• Many species not venomous (puncture frogs…)
Boomslang / Brown trees snake
• Bites / holds prey until ceases struggling
3) Proteroglyphous (“First Knives” = Fixed-fanged)
• Hollow fangs in front / permanently erect & short
• Neurotoxin release
• Bites / holds prey until ceases struggling
Coral snakes / Cobras
4) Solenoglyphous (“Pipe Knives” = Retractable-fanged)
• Hollow fangs in front / folded when mouth closed
• Hemorrhagic / necrotic toxin release
• Injects venom deep; releases prey after bite
• Tracks prey via chemical cues
Pit Vipers
Reptiles
Snakes: (~ 15 families; ~ 2900 species)
Representative Snake Families of North America:
Letpotyphlopidae
Elaphidae
(Blind Snakes – SW United States)
(Example: Texas blind snake)
(Coral Snakes – SE / SW United States)
(Example: Arizona Coral Snake)
• Small, slender snakes (~ 10 cm)
• Venomous (neurotoxin)
• Vestigial eyes (covered by scales)
• Primary diet = other snakes
• Oviparous (parental care ?)
• Oviparous
Snakes: (~ 15 families; ~ 2900 species)
Representative Snake Families of Oregon:
Boidae: (example = Rubber Boa)
Habitat:
• Damp forests and meadows; loose soils
• Low head tolerance (nocturnal)
• Diet: Young, nesting mammals
Anatomy:
• Minute, smooth scales; spurs present
• Short, broad snout; short, blunt tail (“club…”)
Reproduction:
• Late spring breeding
• Up to 4 years between clutches
• Viviparous; 2 – 8 young (late summer)
• Young born pink / semi-transparent
Growth / Maturation:
• Sexual Maturation ~ ???
• Life Span = ~ 20 – 30 years
Rubber / Rosy Boas:
Western United States
Snakes: (~ 15 families; ~ 2900 species)
Representative Snake Families of Oregon:
Colubridae: (example = Sharp-tail Snake)
Habitat:
• Wooded areas with abundant surface debris
• Most active fall / winter (very secretive)
• Diet: Slugs / Plethodons
Anatomy:
• Relatively small (~ 12”)
• Sharp, spine-like scale at tip of tail (“anchor”)
• Two sub-species – long-tailed vs. short-tailed (recent)
Reproduction:
• Late spring breeding
• Oviparous; 2 – 8 eggs; communal nest sites not uncommon
Growth / Maturation:
• Hatch ~ 2 – 3 months
• Sexual Maturation ~ 2 – 3 years
• Life Span = ~ 5 – 10 years
“Harmless” snakes:
Cosmopolitan – United States
Snakes: (~ 15 families; ~ 2900 species)
Representative Snake Families of Oregon:
Viperidae: (example = Western rattlesnake)
Habitat:
• Grasslands / prairies / sagebrush (avoid deserts)
• Diet: Small mammals, birds, etc.
• Toxin = necrotic / hemorrhagic
Anatomy:
• Short, compact body (ambush hunter)
• Rattles – keratin segments; added at each shed
• Pits – heat-sensing; up to 100 yds.
Reproduction:
• Late spring breeding
• Viviparous; 5 – 20 young
Growth / Maturation:
• Sexual Maturation ~ 3 years
• Life Span = ~ 20 years
Pit Vipers:
Cosmopolitan – United States
Reptiles
Cladogram of Tetrapods:
Amniotes
Sauropsids (“reptile-like appearance” - Greek)
Diapsids (“two arches” - Greek)
Lepidosaurs
Archosaurs
Squamates
“Ruling Reptile”
Group includes dinosaurs
(Read chapter 16 (VL) to
your hearts content…)
Reptiles
Crocodilians: (3 families; 23 species)
Evolution / Diversity:
• First appearance in fossil record = Triassic
Closely mirror relatives from Mesozoic period…
Order: Crocodilia
(“Pebble-worm”)
• Tropical / sub-tropical regions
• Semi-aquatic habitats
North America = 2 of 3 families
Most advanced extant reptile:
Many features more similar to birds /
mammals than other reptiles
Reptiles
Crocodilians: (3 families; 23 species)
Characteristics of Crocodilians:
Increased cooling
via evaporation…
• Ectotherms
• Bask during day (temperate) or stay submerged (tropical)
• Bony Plates (osteoderms)
• Over-layered with non-overlapping keratinized scales
• Modified breathing for aquatic lifestyle:
• Nostrils dorsally located at tip of snout
• Secondary palate separates nasal and buccal cavities
• “High walk” vs. “Belly walk”
• High degree of tarsal flexibility; legs swivel under body
• Rapid bursts possible (~ 10 mph)
• “Lateral line” sensory system
• Dome pressure receptors (jaw) detect surface waves
• Ambush hunters (death roll – drown prey…)
• Powerful jaw closure muscles
• Swallow prey whole (most acidic stomach acid)
• Opportunistic hunters (months may pass…)
Reptiles
Crocodilians: (3 families; 23 species)
Characteristics of Crocodilians:
• Oviparous
• Temperature dependent sex determination
• Parental care evident (nest / young guarding)
• Indeterminate growth
• Current record-holder = saltwater crocodile ~ 7.1 m
• Communicate via vocalizations
• Slap head / tail, roar, grunt, hiss, purr, rumble
Major Extant Groups:
1) Alligators (e.g., American Alligator; caimens)
Narrower Head
Tooth Exposure
• Primarily New World group (North / South America)
2) Crocodiles (e.g., Salt water crocodile)
• Indo-Pacific region / Indo-Australian archipelago
3) Gharial (Single species - India)
• Narrow snout = Fish specialist