16: Amniotes (Reptiles) Flashcards
When do we see reptiles form?
Carboniferous Period, 350 million years ago
What are the three major branches?
Synapsida
Anapsida
Diapsida
When did the dinosaurs go extinct?
End Cretaceous
When did turtles appear?
Mesozoic
When was the earliest reptile fossil from?
315mya
What was the earliest reptile fossil?
Tracks showing 5 fingers and scales
Can see position of legs, how they moved
Hyolonomus Iyelli
Examples of anapsids
Stem reptiles
Turtles
Tortoises
Examples of euryapsids
Ichthyosaurs
Plesiosaurs
Examples of diapsids
Crocodiles Snakes Lizards Pterosaurs Dinosaurs Birds
Examples of synapsids
Mammal-like reptiles
Mammals
What are Ichthyosaurs?
Thrived in the Mesozoic
Sea reptiles
Evolved from unknown land reptiles
Viviparous
Function of the shell
External protection
Interaction with environment
Permeable
Function of the chorion
Allows nutrients to pass between
Protection
Function of the allantois
Sac that facilitates respiration
Stores waste
As yolk sac empties, allantois fills
Fuses with chorion
Function of the amnion
Covers embryo when it forms
Fills with amniotic fluid, which protects embryo
Function of yolk sac
Nutrients for growth
Difference between fish/amphibian eggs and reptile
In fish/amphibians there is only one membrane
Called the embryonic (Vitelline) membrane
How many EXTRA skull holes do diapsids have?
2 on each side (4 in total)
How many EXTRA skull holes do anapsids have?
0, just eye holes
How many EXTRA skull holes do synapsids have?
1 on each side
What are the skull holes called?
Fenestrae (single is fenestra)
Early reptile anatomy
Larger humerus than sarcopterygians and primitive amphibians
5 digits
Longer radius and ulna
Can support own body weight
Advantages of being a reptile
Free of water
Access to different food
Avoid predators in water
Egg safety
Exaptations that reptiles needed to have before move to land
No metamorphosis- only grow
Lay eggs on land
Internal fertilisation
Early amphibian vs reptile movement
Larger hip and shoulder girdles
Larger hind and forelimbs
Stronger vertebral column
Less bendy movement
Reptile characteristics
Keratinised scales Two sets of paired limbs, usually with 5 toes Lungs Ectothermic Internal fertilisation Amniotic eggs, no aquatic larval stage
Differences between reptiles and amphibians
Reptiles have tough, dry, scaly skin- so don’t dessicate
Copulatory organ
Efficient jaws for biting, gripping
Complex nervous system
Examples of fossil anapsids
Scutosaurus- ancestors of turtles
Proganochelys
Proganochelys features
Late Triassic
200mya
Had a carapcace (shell) of 90cm
Features of turtles
Enclosed within carapace Long, flexible neck Small brain Oviparous Carnivorous
What did the turtle shell evolve from?
The ribs
How do turtles breathe without ribs?
Expiration: contraction of transversus, aided by pectoralis
Inspiration: contraction of obliquus and serratus, creating negative pressure
What turtle can breathe out of its bum?
Elseya albagula
Example of a fossil diapsid
Petrolacosaurus
First Diapsid
From around 300mya
Small sharp teeth
What is a Tuatara?
A lizard thing
Shares features with Mesozoic animals
Diapsid skull, 2 openings
One of the slowest rates of morphological evolution in vertebrates
What are Squamata?
Lizard worms, lizards and snakes
Extremely diverse
Diapsids
Lizard characteristics
Movable eyelids Keen vision Normally not great hearing Semi-solid urine if live in hot and arid climates Ectothermic Eg. leopard gecko Sticky feet
Worm lizard characteristics
Walk backwards just as well as forwards No back limbs at all, some have forelimbs No visible eyes/ears- hidden under skin Eg. Black and white worm lizard Grow by increasing length, not diameter
How do worm lizards move?
Dig by compressing soil against the roof with their head
As size increases, work required to compress soil increases exponentially
Snake feature
Lack pectoral and pelvic girdles
Ribs along length of body to increase rigidity
Highly kinetic skull increases feeding options- mobile bones
Cornea is protected by a membrane
No external ears
What is the Jacobsen organ in snakes?
A richly innervated chemosensory epithelium on the roof of the mouth
Forked tongue places particles on the organ
Transmitted to brain
‘Tastes’ molecules in air
What are pits?
The most sensitive heat detection system known
Used for strike accuracy
Crocodile features
Largest living reptile Fresh or sea water Have salt glands Closest living relative to birds 64-68 teeth
Where do dinosaurs sit?
In between crocodiles and birds
