Lecture 22- Reptiles Flashcards
What is special about reptiles?
First really successful colonisers of earth’s terrestrial environments
What are scales for in reptiles?
scales: prevent water loss (not permeable)
What is the egg of reptiles like?
- amniotic egg: embryo in fluid-filled sac (+ shell), thus more resistant to drying compared with amphibians
- must have internal fertilisation
- gives you resistance to drying out
What are the water conservation characteristics of reptiles?
• Excrete urea (thick paste) reduces water loss (not urine)
• Faeces very dry (water conservation)
• Ectotherms: constrains activity, but also means energy requirements relatively low (most reptiles can go for considerable periods without feeding)
=Characters make reptiles well suited to exploiting terrestrial and in particular arid environments
What are the four orders of reptiles?
- Order Crocodilia: crocodiles & alligators
- Order Chelonia: turtles & tortoises
- Order Squamata: snakes & lizards
- Order Rhyncocephalia: tuatara (NZ only)
Are reptiles monophyletic?
-no
• Squamata: lizards + snakes
• crocodiles are closest to birds and dinosaurs (Archosauria)
• turtles branched early from the stem leading to archosaurs and lepidosaurs
What is the ancestor of all reptiles and birds?
-Sauropsida: ancestor of all reptiles and birds
How is Australia a land of reptiles?
-825 described species in Australia (North America 280 spp.) - Desert and tropical “hotspots”
How many crocodile species are there in Australia?
1 Family, 1 Genus, 2 Species
How many turtle species are there in Australia?
4 Families, 12 Genera, 22 Species
How many squamate species are there in Australia?
13 Families, 129 Genera, 801 Species
-snakes and lizards
What are the characteristics of crocodiles?
- Heavily armored body, long jaws, streamlined body, powerful tail
- Aquatic predators
- Ancient – 240 million years old
- Tropical distribution
What are the two species of crocodiles in Australia?
- Crocodylus porosus saltwater crocodile “saltie”=(max 7m) are extremely dangerous
- Crocodylus johnstoni freshwater crocodile (endemic to Australia) “freshie”= feed on fish
What is maternal care like in crocodiles?
• All lay eggs, advanced maternal care, sit with the eggs, carry young to the water
What Families of Turtles are there in Australia? (freshwater)
- 4 families in Australia, have marine and freshwater
- Chelidae: side-necked turtles (Gondwanan), fresh water species, more spread
- Carettochelydidae- pitted-shelled (pig nosed) turtle – freshwater sp., limited radiation
What Families of Turtles are there in Australia? (saltwater)
- Family Cheloniidae- marine turtles, everywhere in the sea
2. Family Dermachelydae- marine, also everywhere in the sea, the Leatherback turtle
How many families of lizards are there in Australia?
- 7 families
- most with legs but some without
What are the characteristics of Dragons (family of reptiles)?
- Australia: 15 genera, 50 species (320 worldwide)
- Australian group largely endemic
- Typically: strong legs, fast moving, sun-loving lizards
- All oviparous – eggs in burrows
- Visual displays during courtship including head bobbing, arm waving
What are the characteristics of Geckos (family of lizards)?
Australian geckos recently divided into 3 families:
Geckkonidae, Diplodactylidae & Carphodactylidae
• 25 genera, 114 species (800 worldwide) • Most diverse in arid & tropical areas, none in TAS • All Australian geckos are nocturnal • All oviparous: 1 - 2 eggs/clutch • Some parthenogenic • Highly vocal • Tail autotomy
What is special about geckos?
-have “sticky feet”
What are the characteristics of Pygopodidae? (family of lizards)
• 7 genera 42 species in Australia Thick-tailed gecko Knob-tailed Gecko Knob-tailed gecko • Endemic to Australia and PNG, none in TAS • Closest relatives to geckos (some older Australian gecko groups now classified with pygopodids) • Tail autotomy • 1 – 2 eggs/clutch • Vocal • No forelimbs • Hind-limbs: reduced to small flaps
How do you recognise if it is a legless lizard or a snake?
1: Legless lizards have hind “leg” flaps
2. Legless lizards have external ear
3: Legless lizards: have a fleshy tongue
4. Snakes: have a slender forked tongue
What are the characteristics of Scinidae? (family of lizards)
- Skinks, blue-tongues and stumpy-tailed lizards • 41 genera 389 species (> 1000 worldwide) • Most diverse lizard family worldwide • Largest group in Australia – occur everywhere • Highly variable in morphology, ecology etc.
- Both oviparity (eggs) and viviparity (live young) • Some have reduced limbs
What are the characteristics of Varanidae- monitors/goannas? (family of lizards)
• 1 genus (Varanus) 29 species (approx 38 worldwide, includes
Komodo dragon)
• Widespread worldwide, but Australia stronghold for family
• All oviparous – up to 35 eggs/clutch
• Perhaps the closest relatives to snakes (both have forked tongue)
How many families of snakes are there in Australia?
- 6
- no legs
What are the characteristics of Typhlopidae – blind snakes?
- 1 genus 44 species (approx. 150 worldwide)
- Light sensitive eye spots
- Insectivorous
- Rarely seen – small, nocturnal & burrowing
- Oviparous? • Little known family
What are the characteristics of Boidae - pythons?
• 5 genera 15 species (25 worldwide)
• Most diverse in north
• Large, muscular snakes (up to 7 m)
• Mostly nocturnal, heat-sensitive pits for detection of vertebrate prey
• Kill prey by asphyxiation (constriction) • Oviparous
-can eat large prey: Olive
python Liasis olivaceus and common wallaroo (~35 kg)
What are the characteristics of Acrochordidae – file snakes?
• 1 genus, 2 spp. • Wholly aquatic:
- 1 marine, northern Aust.
- 1 freshwater, tropical lagoons northern Aust.
• Fish-eaters (rough skin) • Viviparous • Quite recent arrivals
What are the characteristics of Colubridae?
- 6 genera 12 species (> 1600 worldwide)
- Only northern and eastern coastal Australia, mostly arboreal and semi-aquatic
- Very recent arrival in Australia – only one endemic species
- Display both oviparity and viviparity
What are the characteristics of Elapidae venomous land snakes & now includes the sea snakes?
- 39 genera 138 species • Front-fanged • Radiated into all Australian habitats
- Includes all the venomous terrestrial species + many non-dangerous species
- Australia has 10 most venomous snakes in the world
- Both oviparity and viviparity
What is the Bandy-Bandy?
-(Elapidae)
Specialise in feeding on blind snakes
-the black and white banded snakes
What are the characteristics of sea snakes?
-(both groups of sea snakes classified with Australian elapids)
SF: Laticaudidae (sea kraits) • 1 genus, 2 species
• Come ashore to lay eggs
SF:Hydrophiinae (sea snakes) • viviparous • 12 genera, 31 species • Wholly aquatic - live young
What type of reproduction do reptiles have?
- oviparity or viviparity
What is oviparity?
- Ancestral condition was oviparity
- Many modern species remain egg-layers
- Most lay eggs in burrow, some goannas lay in termite mounds
- Pythons: incubate eggs
What is viviparity?
• Some snakes and lizards have evolved viviparity
Young being born live
• Viviparity has evolved independently > 100 times in reptiles worldwide
• Most common in southern, colder areas
• Suggests evolution due to thermal constraints on embryogenesis
How is sex determined in reptiles?
- in some groups
is temperature-dependent (TSD) In marine + pitted-shelled turtles: below 30C= all males, 30-32=males and female, above 32= all females
-Family Chelidae: genetic sex determination
What is the sex determination in freshwater crocodiles?
- below 30C all females
- 30-32 some males
- above 32 all females
Summary?
- Wide diversity of reptiles in Australia – highly successful gp.
- Crocodiles: 1 family
- Turtles: 4 families
- Lizards: 7 families -Snakes: 6 families
- Not a monophyletic group
- Both oviparity and viviparity TSD occurs in turtles and crocodiles
