Presentation

1. Amniote Origins and
Nonavian Reptiles
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2. Origin and Early Evolution of Amniotes
Amphibians were first tetrapods to invade
land
- The need to return to water for
reproduction limited their distribution
Amniotes evolved an egg that broke the tie
to freshwater
- Amniotic egg contains a series of
extraembryonic membranes that,
among other features, takes the
aquatic environment with the egg 2

3. Origin and Early Evolution of Amniotes
Amniotic egg
- Amnion - provides an aquatic environment for
development
- Allantois - respiratory surface and waste
collection
- Chorion - encloses the other two membranes
- Yolk sac - nourishes the embryo
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4. Origin and Early Evolution of Amniotes
Amniotes arose in the late Paleozoic (300 mya)
- Early diversification produced three patterns of
temporal fenestra in the temporal region of the skull
- Anapsid - no fenestra. Present early in evolution of amniotes.
Only turtles today, but this is a derived condition
- Diapsid - two fenestra. Present in birds and all “reptiles” except
turtles
- Five clades
- Lepidosaurs - lizards, snakes, tuataras
- Archosaurs - dinosaurs, pterosaurs, crocodilians,
birds
- Sauropterygians - plesiosaurs now extinct
- Ichthyosaurs - aquatic reptiles now extinct
- Turtles - controversial placement
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5. Origin and Early Evolution of Amniotes
Amniotes arose in the late Paleozoic (300 mya)
- Early diversification produced three patterns of temporal
fenestra in the temporal region of the skull
- Anapsid - no fenestra. Present early in evolution of amniotes. Only
turtles today, but this is a derived condition
- Diapsid - two fenestra. Present in birds and all “reptiles” except turtles
- Synapsid - one fenestra. Present in mammals and their extinct relatives
(therapsids and pelycosaurs)
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6. 6

7. Adaptations of Amniotes
Amniotic egg - egg with four extraembryonic membranes
- Amnion, allantois, chorion, yolk sac
- Required internal fertilizations
- Evolution of copulatory organs in many amniotes
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8. Adaptations of Amniotes
Thicker and more waterproof skin
- Use as a respiratory surface diminished
- Evolution of keratinaceous structures
- Scales, hair, feathers, and claws
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9. Adaptations of Amniotes
Rib ventilation of the lungs
- Amniote lungs better developed than anamniotes
- More surface area, but better ventilation too
- Air drawn in through creation of negative pressure
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10. Adaptations of Amniotes
Stronger jaws
- Fish jaws evolved for suction and quick closure
- Cannot apply pressure to captured items
- Amniotes expanded jaw musculature to seize and hold on to prey
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11. Adaptations of Amniotes
High-pressure cardiovascular system
- Functional separation of oxygenated and deoxygenated blood
- By separating the systemic and pulmonary loops, amniotes can maintain higher blood
pressure
- Amphibians 15-40 mmHg
- Reptiles 88 mm Hg
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12. Adaptations of Amniotes
Water-conserving nitrogen excretion
- Amphibians excrete nitrogenous wastes as ammonia (some as urea)
- Because ammonia is toxic at low concentrations, it must be removed in a dilute solution
- This requires lots of water
- Amniotes living away from water evolved the means to concentration
nitrogenous wastes as urea or uric acid
- Less toxic at higher concentrations
- Requires less water to rid the body of
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13. Adaptations of Amniotes
Expanded brain and sensory organs
- Cerebrum and cerebellum are relatively
large in amniotes
- Especially so in birds and mammals
- Enlargement of the cerebrum is associated
with integration of sensory info and control
of muscles during locomotion
- Olfaction
- Sight
- Specialized chemoreception
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14. Changes to “Reptile” Classification
Traditionally defined as
- Snakes, lizards, tuataras,
crocodilians, and turtles
- Plus extinct groups such as dinosaurs,
plesiosaurs, and pterosaurs
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15. Changes to “Reptile” Classification
Morphological evidence suggest
birds and “reptiles” have more in
common
- Diapsid skull
- Ankle characteristics
- Presence of beta keratin
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16. Changes to “Reptile” Classification
As such, “reptiles” is
paraphyletic
- Its continues use, though
incorrect, is largely for
convenience
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17. Changes to “Reptile” Classification
Birds and crocodilians belong in the
clade Archosauria
- Includes the extinct dinosaurs and
pterosaurs
Lepidosaurs are the tuataras, lizards,
and snakes
Turtles were the outgroup
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18. Changes to “Reptile” Classification
The paraphyletic group
traditionally known as “reptile”
are informally known as
nonavian reptiles
- Comprised of four clades
- Testudines
- Squamata
- Sphenodonta
- Crocodilia
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19. Testudines - turtles
Appear in the fossil record 240 mya
- Morphologically similar to modern
turtles
- Except: shell reduced and teeth
present
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20. Testudines - turtles
Modern turtles lack teeth
- Have tough keratinized plates
instead
Shell composed of bone, with large
scales and in two parts
- Carapace - upper
- Plastron - lower
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21. Testudines - turtles
Shell
- Bony parts from expansion and
fusion of ribs, vertebrae, and
dermally ossifying elements
- Evolution of shell:
- Broadening of ribs
- Evolution of plastron
- Evolution of carapace
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22. Testudines - turtles
Unique respiratory processes
- Because ribs are fused to shell,
turtles cannot expand the chest to
breathe
- Abdominal and pectoral muscles used
as a diaphragm
- Movement of the limbs also ventilates
the lungs
- Mouth and cloaca may also assist
in gas exchange
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23. Testudines - turtles
Reproduction
- Internal fertilization
- Oviparous
- Eggs buried and abandoned
- Sex determination by ambient
temperature
- Cooler = more males
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24. Squamata: lizards and snakes
Most diverse of the living nonavian reptiles
- 95% of all reptile species
- Lizards appeared in the Jurassic period
- Did not diversify until the Cretaceous
- Snakes appeared in the late Jurassic
- Likely evolved from lizards
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25. Squamata: lizards and snakes
In both lizards and snakes the skull is
kinetic
- Has moveable joints
- Allows for seizure and manipulation
of prey
- Increased bite force
- In snakes, kineticism is greater and
allows for swallowing of very large
prey
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26. Lacertilia: lizards
Very diverse group
- Terrestrial, burrowings, aquatic, arboreal,
and aerial members
- Familiar lizards include:
- Geckos - small, nocturnal forms with adhesive
pads on feet
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27. Lacertilia: lizards
Very diverse group
- Terrestrial, burrowings, aquatic, arboreal,
and aerial members
- Familiar lizards include:
- Iguanids - brightly colored New World lizards
with frills and crests
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28. Lacertilia: lizards
Very diverse group
- Terrestrial, burrowings, aquatic, arboreal,
and aerial members
- Familiar lizards include:
- Skinks - elongate bodies, tight fitting scales
and reduced limbs
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29. Lacertilia: lizards
Very diverse group
- Terrestrial, burrowings, aquatic, arboreal,
and aerial members
- Familiar lizards include:
- Monitors/varanids - large active predators
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30. Lacertilia: lizards
Very diverse group
- Terrestrial, burrowings, aquatic, arboreal,
and aerial members
- Familiar lizards include:
- Chameleons - arboreal lizards of Africa and
Madagascar
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31. Lacertilia: lizards
Body form
- Most have four limbs
- Limbs may be reduced or absent
- Short bodies
- Eyelids are movable
- External ear openings
- Ectothermic
- Adapted for hot, dry conditions
- Lipids in skin minimize water loss
- Little water loss during excretion - uric acid
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32. Serpentes: snakes
Limbless today
- Early fossils had external limbs
- Pelvic girdle persists in a few snakes
- Vertebrae are shorter and wider than
those in other vertebrates
- Permits lateral undulations for movement
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33. Serpentes: snakes
Body form
- Spectacle covers and protects eye
- No movable eyelid
- Don’t blink
- Generally poor vision
- No external ears or tympanic membrane
- Capable of hearing and detecting vibrations
- Chemical sense are more useful
- Jacobson’s organs (vomeronasal) on roof of
mouth
- Tongue flicked out to gather chemicals
and draw them pst the vomeronasal
organ 33

34. Serpentes: snakes
Body form
- Boids and pit vipers have pit organs for
sensing radiant energy
- Can detect difference of 0.003℃
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35. Serpentes: snakes
Movement - much variation
- Lateral undulation - S-shaped pattern.
Results in fast movement, loops appear
to stay stationary
- Concertina movement - useful when
moving in tight channels like tree hollows
- Rectilinear movement - used when
stalking prey. Slow and deliberate.
earthworm-like
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36. Serpentes: snakes
Movement - much variation
- Lateral undulation - S-shaped pattern. Results in fast movement, loops
appear to stay stationary
- Concertina movement - useful when moving in tight channels like bark
- Rectilinear movement - used when stalking prey. Slow and deliberate.
earthworm-like
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37. Serpentes: snakes
Movement - much variation
- Lateral undulation - S-shaped pattern.
Results in fast movement, loops appear
to stay stationary
- Concertina movement - useful when
moving in tight channels like bark
- Rectilinear movement - used when
stalking prey. Slow and deliberate.
earthworm-like
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38. Serpentes: snakes
Movement - much variation
- Sidewinder motion - used in loose, sandy
soils of deserts
- Flying????
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39. Serpentes: snakes
Feeding
- Most grasp prey with mouth and swallow
it whole while it is still living
- Some snakes kill by constriction
- Generally ambush predators
- Some snakes kill by venom
- 20% of all snakes
- Venom is modified saliva
- All snakes mildly venomous
- Neurotoxin
- Hemorrhagin
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40. Serpentes: snakes
Reproduction
- Most are oviparous
- Some viviparity and ovoviviparity
- Viviparous snakes nourish young with
placentae
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41. Sphenodonta: tuataras
Two living species
- Found in New Zealand
- Once more widespread, declined at end
of Mesozoic
- Recent localized declines due to invasive
species
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42. Sphenodonta: tuataras
Two living species
- Low reproductive and growth rate
- Slow rate of morphological evolution
- Share many features with ancient diapsids
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Iguana

43. Crocodilia: crocodilians
With birds are the only survivors of the archosaurian lineage that gave rise to
dinosaurs
- Modern crocodilians are similar to crocodilians from the mesozoic
- Unchanged for 200 million years
- 25 spp.
- Divided into three groups
- Crocodiles - Worldwide
- Alligators and caimans - New World
- Gharials - India and Nepal
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44. Crocodilia: crocodilians
With birds are the only survivors of the archosaurian lineage that gave rise to
dinosaurs
- Modern crocodilians are similar to crocodilians from the mesozoic
- Unchanged for 200 million years
- Divided into three groups
- Crocodiles - Worldwide
- Alligators and caimans - New World
- Gharials - India and Nepal
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45. Crocodilia: crocodilians
With birds are the only survivors of the archosaurian lineage that gave rise to
dinosaurs
- Modern crocodilians are similar to crocodilians from the mesozoic
- Unchanged for 200 million years
- Divided into three groups
- Crocodiles - Worldwide
- Alligators and caimans - New World
- Gharials - India and Nepal
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46. Crocodilia: crocodilians
Body form
- Elongate snout with well-developed jaw musculature
- Thecodont teeth set into sockets
- Secondary palate
- Four-chambered heart
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47. Crocodilia: crocodilians
Reproduction
- Oviparous
- Eggs have temperature-dependant sex determination
- High parental care
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