squamates

amniotes

devonian era
- fish are hte main animal
- tetrapods start to enter the scene
carboniferous era
- amniotes appear
permian era
- right before dinosaurs
- because it was dry it was good for the amniote tetrapods
- permian extinction
  - worst extinction event
  - groups that survived
    - lissamphibia
    - group that later became dinosaurs
    - group that later became mammals
things amniotes have in common
- internal fertilization and penis
- claws or nails
- no more aquatic larvae
- no more lateralis system
- amniotic egg
what is an amniotic egg
- breathes air
- extra embryonic membrane
- amnion allantois and chorion
  - amnion is a fluid filled water sac
  - allantois is a where nitrogenous waste goes
  - chorion surrounds everything and is the basis for the placenta
major groups
- anapsida (turtles)
- synapsida (mammals)
- diapsida (reptiles)
breakdown
- amniotes
  - snapsida
  - sauropsida
    - lepidosauromorpha
      - tuatara
      - squamates
    - archosauromophs
      - turtles
      - archosauria

lepidosauria

tuatara
- living fossil
- weird teeth and skull because skull is made up serrated teeth like protrusions, with two rows on the upper jaw
- weird diet of baby birds and insects
- only amniote without a penis
- nocturnal/crepuscular
  - active at dawn and dusk
  - has a vertical pupil to see better in dark
  - vocal
  - pineal eye
    - pineal eye is a light sensitive organ that secretes melatonin
    - special because it is directly exposed to outside world through hole in the skull that is covered with eye tissue
- super slow everything
  - lives in cool conditions that supports slow movement
  - low metabolism
  - low reproductive cycle
  - lives for over 100 years
- temperature dependent sex determination
- still evolving
squamates

squamates

types of squamtes
- geckos
  - these guys are nocturnal slow moving lizards that live everywhere, have delicate skin, and no eyelids (lick eyeballs)
  - they have special feet made up of tiny treads, made up of setae made up of spatulae which works through van der waals interactions
- skinks
  - these guys are mainly insectevours and are mainly found in the desert, they make up majority of viviparous, and parental caring lizards
- teiidae
  - these guys are super fast, active foragers
- amphisbaenians
  - these guys are mostly legless, underground and tropical lizards
  - two types
    - blunt heads which are foragers near the surface and have a variety of prey
    - wedge snouts which are better diggers and have more limited prey
- toxicofera
  - mosasaurs
    - gigantic extinct lizards that look like an aquatic dinosaur
  - serpents
  - anguimorpha
    - varanidae
      - these guys are primarily old world active predators that go after large prey, they use their vomeronasal organ to track prey and have a throat pump to better aerate their lungs
    - anguidae
      - consists of glass lizards and alligator lizards
      - glass lizards
        look like snakes but not because of eye lids and ears
        can lose tail at drop of a hat (break like glass)
    - helodermatidae
      - gila monsters and heloderms
      - neurotoxic saliva
      - colorful
  - iguanidae
    - chameleonidae
      - these guys are old world arboreal lizards with prehensile tails and eyes that can move separately
      - they are laterally compressed which is good because they can keep center of gravity over a branch
      - they can color change both to match background and to communicate however they typically have to stick to one color if trying to match background
      - they also have a projectile tongue which makes them able to do things lot of other lizards cannot
    - iguanidae
      - these guys are new world herbivores that break down cellulose through digestive fermentation
      - babies eat feces from mom to inoculate their digestive system and immune system (example of parental care)
    - phrynosomatidae
      - these guys squirt blood from their eyes and typically have horns
    - polychrotidae
      - these guys can also change colors but only to match mood and temperature they also have a dewlap
defense
- stripes versus blotches
  - ambush predators will have blotches to help them blend in with surroundings
  - active predators will have stripes because they do not need to blend in with surroundings, and the stripes will confuse predators
- aposematic color and venom
  - warning coloration
  - however venom is used primarily to feed rather than to defend
- squirting blood in phyrnosomatidae
- mimicry
- attack
  - a few will be aggressive but it is more for show to scare off predators
- autotomy
  - some lizards will come back later to eat their tail to regain lost energy
- running on water
  - small lizards are able to use rectangular toe fringes to literally run on water by walking on surface tension without breaking it
- flying
  - some can use toe pads to extend their fall
feeding
- herbivores versus carnivores
  - herbivores will be larger lizards
  - carnivores will be smaller lizards
    - exception is monitor lizards
- sit and wait ambush predators
  - ambush predators have cryptic coloration, are anaerobic and small hearted because they don't need lots of energy
  - they will only eat very large things infrequently because it is a) too risky to break coloration b)waste of energy to go after small things
- foragers
  - foragers have stripes, are aerobic and big hearted because they need lots of energy to run around all the time
  - they eat smaller prey because since they are already running around it is not a waste of energy or present more risk to predators
- thermal inertia
  - bigger lizards have more thermal inertia which means they can maintain temperature for longer allowing them to hunt in cooler areas
  - smaller lizards cannot maintain temperature for longer so they must do all their work in the sun
reproduction
- courtship techniques
  - visual
    - head bobbing
    - push ups
    - dewlap
  - geckos are the only vocal ones
  - use of pheremones
- hemipenes
  - double penis where one penis is connected to each testicle, and after one is used the other can be used for another female
- ovipary
  - main way lizards have babies
  - sometimes there will be temperature dependent sex determination
  - very little parental care
- vivipary
  - spectrum
  - vivipary is favored by natural selection
  - biased towards skinks
  - vivipary is accomplished through the chorioallantoic placenta
  - benefits
    - in cool climates developmental speed can be increased
    - eggs are protected from predators and elements
  - cons
    - females have a harder time protecting themselves while pregnant
    - only one clutch can occur per season
- parental care
  - egg guarding
  - incubating eggs
  - mainly shown by skinks
- parthogenesis (asexual)
  - clonal
    - all females are made, and females are used to imitate ovulation through courtship
    - sex roles are determined by hormonal cycle
    - this is found mainly in hybrids
  - nonclonal
    - found in lizards that have a WZ ZZ system
    - meiosis is followed by duplication where first a female donates one chromosome and the chromosome is duplicated (WW or ZZ) and only ZZ survive so only males are made
- temperature dependent sex determination
  - common in reptiles
  - pivotal temperature is the range that produces equal amounts of males and females
  - some lizards can assess reproductive ratio and will try to fix it by controlling how warm the eggs are