Amniotes and Lepidosaurs Flashcards
What are the key adaptations of tetrapods?
Air breathing
Limbs w/ fingers
How do amniotes differ from amphibians + fish?
They have an amniotic egg
Describe an amniotic egg
Egg encased in membranes
- protect egg from drying out + provide gas exchange
How had reproduction changed on land?
Internal fertilisation
Often assisted by an intermittent organ
- penis in most
or hemipenes in lizards + snakes
What is special about juvenile amniotes?
Loss of larval stage (no gills or fin)
= direct development
Describe tetrapod skin
Describe amniotic skin
Lack bony scales
- can shed skin
This skin is waterproof
= keeps water in
When did the 1st amniotes appear?
300+mya
Carboniferous
Amniotes stage adaptive radiation.
What did the earliest amniotes differentiate into?
Synapsid lineage
(mammal)
Sauropsid lineage
(bird-reptile)
Which lineage dominate in the late carboniferous –> permian?
Synapsids
-produced specialised herbivores + carnivores
What enabled Sauropsids to take over + diversify?
Permo-triassic extinction wipes out synapsids
Which groups make up Lepidosauria?
Tuataras
Lizards
Snakes
What are tuataras?
Nocturnal
Inhabit cool environments in NZ
(Rats wiped them out on main island)
Specialised jaws w/ teeth that fuse to jawbone
What are squamata?
Lizards + snakes
= most diverse tetrapod group
>ecologically diverse
>wide range of lifestyles
What are the features of geckos?
>Lizards >Day active >Specialised climbers - use lamellae to stock to surfaces using intermolecular attraction > Caudal autonomy - grow new tail > flying geckos - elaborate falls + webs
Australian lost limbs + evolved snake-like body
Where are iguanidae found?
1 species in Fiji
Few species in Madagascar
What is special about marine iguanas?
Bask on hot lava rocks to raise body temp before diving into Pacific to feed
Which group are chameleons in?
Acrodonts
Why are chameleons among the most specialised lizards?
Opposable digits +
prehensile tail grasps branches
Change colour to blend in
Eyes elongated to increase magnification
- can independently swivel to track prey
Shoot out tongue to catch insects
What are Amphisbaenia?
What are their features?
Worm lizards
> Specialised for burrowing
Worm-like bodies surrounded by ring of scales
Slide skin back + forth to crawl through narrow tunnels
Powerful jaws + a few large teeth
Reduced eyes + no external ears
- enlarged ear bones
Give an example of an Anguimorpha
Komodo dragon
When was there a mass extinction of lizards?
K-T boundary
How do snakes feed?
All predators
- some prey is equal to or greater than their own body weight
Multiple cranial + mandibular hinges allow them to dislocate their faces to swallow large prey
Also have no sternum so rib cage can expand to swallow large prey
How are snakes adapted to being carnivores?
Hooked teeth
Constriction - disables prey by cutting off blood supply to brain
Venom - cytotoxic + neurotoxic posions
What are the 2 hypothesis for how the snake elongate body plan evolve?
Marine origins
Fossorial (true)
Explain the marine origins hypothesis
Snakes could be related to long-bodied, marine mosasaurs
= suggests marine ancestry
Explain the fossorial hypothesis
Loss of eyelids
Simplified eye
Loss of external ears
Long skinny body
What is the oldest definitive snake?
What are its features?
Tetrapodophis
4 limbs (bridges gaps between snakes + lizards) Large no. of vertebrae for constriction Large recurved teeth Elongate trunk relative to tail = typical of burrowing lizards
How has snake feeding evolved?
Early snakes were carnivores + constrictors
Where did early snakes come from?
Gondwana
= ancient dinosaur-era continent
