Lecture 4- Reptiles 1 Flashcards Preview

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What reptile orders are there in Australia?

-crocodiles -turtles -squamates (lizards and snakes)


What proportion of animals in Australia are reptiles?



What is phylogenetics?

-the study of evolutionary relatedness among groups of organisms (e.g. species, populations), which is discovered through molecular sequencing data and morphological data matrices


What is the phylogeny of reptiles?

-phylogenies are hypotheses, and help us understand adaptation


What is an ancestral trait?

-trait that was in a common ancestor and is inherited from that ancestor


What is a derived trait?

-trait that evolved only with that division and is not shared with its ancestral organisms, e.g. feathers in birds


What is an outgroup?

- a (monophyletic) group of organisms that serve as a reference group for determination of the evolutionary relationship among three or more monophyletic groups of organisms,can tell where a trait arose


What does monophyletic mean?

-a group of species that consists of an ancestral species and all its descendants


Are reptiles monophyletic?

-no, as birds would have to be included


What are the characteristics of crocodiles?

-crocodiles today are recent radiation= only 30 million years or so (the lineage is however ancient) • heavily armored body, long jaws, streamlined body, long tail • aquatic predators • ancient – 240 million years old • tropical distribution • only crocodiles in Australia (no alligators, caimans or gharials)


Did crocodiles ever walk on land?

-yes, they used to be land based at some point in their development (experimented with being on land) -used to be much larger, up to 12m in length


What are the two species of crocodiles in Australia?

1. Freswhater crocodile= lives in the north, in rivers, upstream areas, has thin snout, grows to about 3 m and is not a huge threat to humans 2. Saltwater crocodile= up to 6-7 m. LIves in the estuary, threat to humans


What is the difference between tortoises and turtles?

-tortoises are usually on land and have high dome shaped shell, herbivorous -turtles, in water and flatter shells, in Australia only turtles!!!


What are the freshwater turtles in Australia?

-2 families -Family Chelidae – side-necked turtles (Gondwanan), lives in Asutralia and South America,around the coast freshwater -Family Carettochelydidae – pitted-shelled turtle, lives only in small bits of Northern Australia and PNG, Gondwanan relic,more specialised for swimming


What are the sea turtles in Australia?

-2 families of sea turtles -Family Cheloniidae (overall 8 species, in Australia there are 5), green turtle etc,the common one you sea in the sea -Leatherback turtle, globally distributed,largest of all turtles (1 species only) -4th biggest reptile, warm blooded, high diving (up to 1000m) one of the fastest swimming reptiles 37km


Why is Australia the land of lizards?

-over 650 species,more than any other country in the world


What are the four lizard linneages in Australia?

1.Geckos (Gekkonidae) (Carphodactylidae) (Diplodactylidae) (Pygopodidae - legless lizards) 2.Skinks (Scincidae) 3.Dragons (Agamidae) 4.Goannas (Varanidae)


What are the characteristics of geckos?

-nocturnal • Australia 20 genera, over 150 species • tail autotomy (drop-tails) • vocal • some have sticky feet -big eyes, tend not to have eyelids, vocal= can hear them (ttttt) -sticky feet, (use van der waals forces) -can lose their tail -quite big distribution , relatively diverse


What are the four gecko families?

1. Gekkonidae e.g. Bynoe’s Gecko, Worldwide 2.Diplodactylidae e.g. Spiny-tailed Geckos, Velvet Geckos Only in Australia 3.Carphodactylidae e.g. Knob-tails, Leaf-tails Only in Australia 4.Pygopodidae Legless lizards Only in Australia


What are the characteristics of Pygopodidae: Limbless geckos?

• Endemic to Australasia • Nearly complete limb loss (no intermediates) • Diversity of form and function - fossorial, terrestrial, semi-arboreal • Snake mimicry • Relationships?: some gecko traits (two eggs, no eyelids)


What is the phylogeny of geckos?

-the three australian groups the three on the bottom: soft shelled eggs, the legless closely related to the other two aus families


What are the characteristics of Skinks: Family Scincidae?

• most diverse lizard family in the world • Australia: 36 genera, 365 species • tail autotomy (drop-tails) • strong association with leaf litter and the top layer of the soil -60% of aus reptiles= skinks -includes the blue tongue skins


What is characteristic of the Egernia group of the skinks?

-this is where the blue tongue is -live baring reptiles -shingleback= family bonds -social structures


What is characteristic of the sand-swimming group of the skinks?

-skinks can change their body shape a lot, sand swimmers -usually lose front limbs first then hind legs -can become legless lizards and we have all the intermediate stages still alive today


What are the characteristics of Dragons: Family Agamidae?

• entered Australia about 30 MYA • Australia: 13 genera, 65 species • fast moving, sun-loving lizards • visual predators, sit-and-wait • can change colour, visual displays during courtship including head bobbing, arm waving good diversity, quite fast moving animals, like it hot= have on of the highest operating body temperatures -colour changes, communicate


What are the characteristics of Goannas: Family Varanidae?

-• ‘goanna’ a corruption of iguana, also called ‘monitors’ • entered Australia about 30 MYA • Australia: 1 genus (Varanus), 27 species • energetic predators, high metabolic rate when active -very smart -live in diverse habitats


What was the Megalania prisca – “ancient giant butcher”?

• 5.5 metres, 620 kg • disappeared about 40,000 years ago • fossils in Naracoorte Caves on SA/Vic border • also Komodo Dragon fossils in Oz • formerly land of giant lizards! -largest lizard to have ever lived


Are goannas and snakes closely related?

-some evidence suggests so: both have forked tongue, both have fangs, claws, big teeth= both have developed ritual combat= without really hurting each other -genetic evidence shows they are not closely related so it is just independently derived traits


What is the forked tongue of snakes and goannas for?

-like eyes -with one you can't tell distance with two you can so that is why it is forked


What is the phylogeny of snakes?

-snakes like highly derived lizards -are monophyletic but lizards aren't


What are the characteristics of Blindsnakes: Family Typhlopidae?

• Worldwide radiation

• Australia: 1 genus, 40+ species

• fossorial – in soil under rocks

• very small (less than 50 cm)

• feed on ants and termites (abundant resource for a specialist)

• very poorly known


What are the characteristics of Pythons: Family Pythonidae?

• Australia: 5 genera, 15 species • large, muscular snakes > 5 metres (smallest 60 cm) • vertebrate predators, esp. mammals and birds • heat-sensitive pits on lower lip, kill prey by asphyxiation • one human fatality in Australia • brood their eggs – a derived character -heat sensitive pits= that's how they detect animals


What are the characteristics of File Snakes: Family Acrochordidae?

• Australia: 1 genus, 2 species • northern Australian rivers, billabongs and estuaries • completely aquatic, fish eaters (rough skin) • very low metabolic rates, “sluggish”


What are the characteristics of Families Colubridae/Homolopsidae?

• extremely diverse group globally • Australia: 9 genera, 11 species – very recent arrivals • restricted to northern and eastern costal areas • aquatic and arboreal forms • keelback eats cane toads!


What are the characteristics of Family Elapidae?

• extremely diverse group in Australia  20 genera 80 species, recent radiation • radiated into all habitats throughout Australia • front-fanged venomous snakes • all Australian elapids prey on vertebrates -the ones you think of as dangerous australian snakes


What are the characteristics of Laticaudidae and Hydrophiidae?

-Snakes return to the ocean -• evolved from elapid snakes • paddle-shaped tail • laticaudids (sea kraits), 1 genus 2 species  visit Australian waters  partly terrestrial (eggs laid on land) • hydrophiids (sea snakes), 12 genera, 31 species  evolved from tiger snake group?  entirely aquatic (live bearers at sea)


What was the evolution of venom in reptiles?

-two tier, lot of them have modified salivary glands that are venomous glands now(The Toxicofera venom glands – a shared derived character) -then a more specialised groupwhat we think of as the venomous snakes= they even have delivery mechanisms=fangs


What is the venom for in snakes?

-mostly catching prey -not for defense as it takes a while to take effect -venom is also used in medicine: Neurotoxins=Block nerve synapses leading to heart and respiratory failure --Haemotoxins=Destroys red blood cells --Coagulants=Cause blood clots --Anticoagulants=Prevent blood clots --Cytotoxins=Destroys cells