Reptiles Flashcards
Reptiles
- First group of vertebrates to successfully breed on land
- due to the development of the cleidoic (or amniotic) egg
- the embryo within the egg is surrounded by a series of extra-embryonic membranes
3 extra-embryonic membranes:
Amnion, Chorion and Allantois
Amnion
surrounds the embryo
sprawling posture
egs held out to the side of the body, which places limits on their ability to run for long periods.
Reptilian organisation
300 million years ago
Mesozoic era
225 to 65 million years ago
reptilian extinction events
The Permian-Triassic (252 Mya) and Cretaceous-Tertiary (65 mya)
The major reptilian groups are recognised by the number of openings in the skull:
the anapsids have none, the synapsids have one, the diapsids have two
give birth to live young
viviparity
lay eggs
oviparity
Pterosaurs
first vertebrates to take to the air
Key characteristics of modern reptiles
- cleidoic egg with shell
- skin covered in scales (keratin)
- legs typically in sprawling posture
- ectotherms
ectotherms
Gain heat from radiation and conduction,
loose heat by convection or evaporation
temperature in reptiles
- Reptiles need less energy than mammal of equivalent size
- Temperature can play a role in sex determination
(e. g., turtles, cooler nests produce males, warmer nests females)
Turtles
- shell fused to ribs and vertebrae
- shoulder blade inside ribcage
- notch on skull where jaw muscles attach
Turtle summary
Approx 300 species Place within the reptile tree is uncertain Shell (carapace + plastron) Shoulder blades inside the rib cage Anapsid skull (no holes) Several cases of island giants
Rhynchocephalia
fossil record
Tuatara key facts
- Sole surviving Rhynchocephalia (“living fossil”)
- Most isolated branch on vertebrate tree
- Restricted to islands of coast of New Zealand
- Long-lived (~100 years)
- Rapid rate of molecular evolution
komodo dragon
- skull relatively weak
- poorly adapted to generate high bite forces
- rely on causing deep wounds and venom
snakes
- evolved from legless lizards
- ancestral snakes possibly burrowed underground
Titanoboa
- 12-15m long
- long lived 58-60MYA
Lizard vs snake
-around 5800 lizards vs 3400 snakes
-lizards range in size from 29mm to 3m, snakes up to 8.7metres
-
Crocodile surfing
- can travel by surinf river and ocean currents
- time travel to coincide with tide turning
- large distances
crocodiles and birds
- both are archosaurs
- crocs are closest living relatives of birds
