Major lizard clades
Contains traditionally three families
Iguanidae (primarily New World)
Split into many different families recently, 12 different families. And one of new families has same
name as whole group! Now the group is renamed “Pleurodonta” – teeth exposed on inside of jaw
margin. Vs chameleons and agamids (acrodonta)
Whole group is called iguanians.
It has primitive reptilian condition – very robust skull. Complete postorbital bar, upper temporal bar
Iguanians share several traits with tuatara that are believed to be primitive, even though tuatara not
believed to be primitive
Robust, nonreduced skull
Generally insectivorous, sitandwait
Terrestrial and arboreal (varied habitats), but not really burrowers
Visually oriented, territorial
Because visually oriented and territorial, not surprising that they have the most elaborately ornate
features. Very little similar things in other lizards – probably because SO visually oriented.
Western fence lizard (Sceloporus occidentalis) – found throughout much of North America, blue
bellies (because of blue belly). Very typical. Insectivorous, medium sized. Most frequently seen
lizard in N. America
Texas Horned Lizard (Phrynosoma cornutum) – flat, with big belly. They eat ants – not much
nutrition, so have to eat a lot of them. Ruptures blood vessels around eyes to repel canine
Aspects of iguanid diversity
Locomotion: most run in typical quadrapedal manner. But, some are bipedal like zebra tail.
Basilisks take it to the extreme – run on water bipedally – fringes on toes like snow shoes. Fringes
have evolved several times, primarily for sand running
Most eat insects, but many are carnivorous, eat small vertebrates. Only one, the leopard lizard, is
exclusively a carnivore, eats exclusively lizards and snakes, etc.
Iguanas are exclusively herbivorous – green iguana, desert iguana.
Adaptations: vegetation is not very nutritious, so they have to eat lots. Need a big stomach, and
need to move food through intestines slowly to have enough time to extract nutrients. So, very long
intestinal tracts. And many species have evolved obstructions in short intestine – slow down passage through gut.
Teeth for chopping vegetation – pointy tricuspid teeth.
Finally, like most herbivorous vertebrates, get help digesting cellulose through microbes. So how
does baby iguana get microbes? Baby iguanas search out iguana poop and eat it.
Anolis. Dewlaps and toepads.
Agamidae (Old World counterparts to iguanidae)
Essentially look the same as iguanidae, just the Old World counterpart
Frilled lizard – a meter and a half long. Australia
Thorny Devil or Moloch – also from Australia. Covered with spines which are incredibly sharp.
Australian counterpart of horny lizard – eats ants, squat. Convergent evolution. (but doesn’t shoot
blood out of eyes)
Draco – flying dragon. Glides long distances. Elongated ribs that normally lie by the side of body,
but lift them and can glide. Ribs extend outside of body wall. They also have little things at neck for
rudders, and a little dewlap. (They display with dewlap and stick out patterns on wings when
130 species of chameleons. 2/3s occur in Madagascar, where the genus evolved. Most of the
remainder are in Africa, but also in Southern Europe (Spain and Greece) and one species in India.
Even the ones on the ground have the typical foot structure
Tongues – can shoot out length of body to capture prey.
Renowned for ability to change colors. Anoles can change to some extent, but none match
chameleon. Still, no real good evidence that they match background. But, they do exhibit emotion:
green or bright means dominance, dark brown or black tends to