Australian Reptiles (Crocs, Turtles And Lizards) Flashcards
How many reptiles do Europe, USA and Australia have respectively?
Europe = 150 US = 310 Oz = 1000
How is lizard diversity in Ozzy desert compared to rainforests of Borneo and Amazon?
Higher!
What is a reptile?
Cold-blooded
Scales
Paraphyletic group including turtles, crocodilians and squamates (lizards and snakes)
To make the group monophyletic, birds should be included, but they’re usually not.
Order: Testudines
Tortoises and turtles
Have existed since Pangaea, therefore they have global distribution.
Oz have no land tortoises, however, they are on the other side of Wallace’s line.
Ectothermic,
All lay eggs on land
Wide range of diet
Some have cloacal breathing, where they take in aerated water in their bum and extract oxygen
Order: crocodilia
Clade: Archosauria
Allied to the lineage that was dinosaurs and is now birds.
Share four-chambered heart and parental care with birds
Have been around since Pangaea 200 mya
All extant crocodilians are aquatic, terrestrial species used to exist.
Ectothermic, but retain heat well (salties)
All lay eggs on land, females build nests of decomposing vegetation that creates heat. Female guards nest.
Aquatic adaptations:
- eyes, ears and nares on top of head
- laterally compressed tail
- webbed hind feet
- incredible circulatory system (moves oxygenated blood around even under the water for a very long time)
Ozzy crocs:
Two species - Saltie (Crocodylus porosus) and Freshie ( Crocodylus johnstoni)
Order: Tuatara
Very ancient. Lives in New Zealand, only one species left. The order used to be widespread. Not a lizard Not a dinosaur Don't call them reptiles either
Order: Squamata 🦎🐍
Lizards and snakes
Over 9000 species worldwide, more than 950 are just in Australia.
All ectothermic, all have scales
Paired copulatory organ called hemipenes
Head anatomy very different from crocs, turtles and tuataras. Upper jaw not fused to the head = kinetic skull
Egg laying (most groups, warm areas) or live bearing (some groups, cold areas)
Some can reproduce asexually
Limblessness has evolved at LEAST 25 times in squamates.
Snakes are the biggest group of legless lizards.
Why is the lizard density so high in Australia?
General reasons:
- warm
- diverse habitats
- stable refugia
- complex mix of groups, both gondwanan and Asian origins
Why is the lizard density so high in the arid areas of Oz?
Three hypotheses:
1. Lizards fill ecological roles filled by other groups elsewhere (snakes and varanids are like mammal predators)
Because - Oz is harsh and unpredictable, dry, low nutrient and ectotherms can just shut down and wait, they don’t need predictability. Mammals can’t do that.
Also, the groups that might have been competing with them for the roles, like placental mammals, never got to Oz in the first place
- Uniquely ideal reptile habitat
Because - Oz has spinifex grass dominating in arid areas, which is perfect for reptile refuge and also it is termite food, and reptiles eat termites.
- Uniquely high habitat variability
Ozzy desert habitats are remarkably variable due to soil and substrate, fire and resulting vegetation.
Infraorder: Geckos
7 families in the world, 4 families in Oz
Typical traits:
- eyes covered by immovable transparent spectacle
- digits expanded with lamellae (not always)
- tail autotomy (part or whole)
- oviparous (typically 2 eggs)
Gekkonics and diplodactylids are considered normal
Carphodactylids and pycopodids are unusual and uniquely Australian
Family: Carphodactylidae
Gecko family
Endemic Australian
Leaf tail geckos and knob tail geckos and chameleon gecko (only one species, only lizard with tail that makes noise)
(Typical gecko traits: immovable transparent spectacle, 2 egg clutches, tail autotomy)
None have sticky lamellae.
Family: Pygopodidae
Limbless group of geckos only found in Australia.
Some species still have little flaps and pelvic bones from where the limbs used to be.
Tail autonomy, immovable transparent spectacle, 2 egg clutch.
They have external ear openings, which snakes don’t have. Big fleshy gecko tongue, not snake tongue.
Family: Scincidae
More than 500 species in Australia
Occur in all habitats, but greatest diversity in arid and tropic areas
Most eat insects no great diet specialist
Oviparous or viviparous
Almost all diurnal (geckos are nocturnal)
Many examples of limblessness (lerista)
Skinks have shiny, overlapping scales, where geckos have soft, bead-like scales
Movable transparent membrane over eyes.
Family: Agamidae (Dragons)
~80 species in Oz No limblessness No tail autotomy Scales rough not glossy All oviparous Complex social behaviour, visual communication (bright coloured males) Sexual dimorphism!
Stems from Asia.
Agamids and pythons are paired in distribution (Africa, Asia and Australia), while iguanids and boas are paired in distribution (Americas, Pacific Islands and Madagascar!?)
Family: Varanidae (goannas/monitors)
Australia, Africa, SE Asia
Oz has ~30 species, highest diversity in northern, arid Australia.
Most diverse in Oz, even though it is the last place they colonised (20 Mya)
No limblessness No tail autotomy Oviparous Male-male combat Amazing breeding in some spp. Female lays eggs in termite mound, termites seal it up, female comes back and digs babies out of the mound.
