Reptiles
Where are reptiles from?
Fossil evidence tells us that reptiles evolved around 310 million years ago (MYA) from a common ancestor which was shared with amphibians but the difference being that these newly evolving animals were laying their eggs which survived on land, unlike amphibians.
Around 260 MYA this lineage split into two:-
- Synapsids which leads to mammals, and
- Sauropsids (meaning lizard-face) which leads to the living reptiles we have today.
It was this along the Sauropods path that dinosaurs appear, evolving around 230 MYA.
Of our reptiles that we see today the oldest group would be turtles - whose common ancestor split from the 'land egg-laying vertebrates' around 300 MYA. Crocodiles - which first appeared around 240 MYA - evolved from the archosaurs lineage which includes dinosaurs and flying reptiles. Lizards appeared around 210 MYA and finally snakes around 135 MYA.
A surprising fact is that birds - which are warm-blooded and covered in feathers - evolved from dinosaurs around 155 MYA. The first reptile-like bird, the archaeopteryx, evolved which is the common ancestor to our modern birds. This means also that a birds closest reptile cousin today is a crocodile.
65.5 MYA a mass extinction meant we lost all the large land, air and sea based reptiles, it was the end of the dinosaurs and pterosaurs.
Today we have an estimated 8000 species (or 17,500 if you wish to include birds) of reptile living.
There are 4 orders of reptile (excluding Aves (birds)) which are:-
Chelonia (tortoises, turtles and terrapins)- Squamata (snakes & lizards)
- Crocodilia (crocodiles, alligators and gharials)
- Rhynchocephalia (tuatara)
What defines a reptile?
Reptiles are ectothermic animals - cold blooded - some lay eggs and others have live babies by giving birth to young in embryonic membranes which the young emerges from.
Reptile bodies are covered in a waterproof skin which can be scaly, plated or bony. All have a backbone (vertebrate) and breathe air.
Reptiles are found all over the world and on every continent apart from the Antarctica. As they do not use their own energy to warm their bodies - relying on the sun to warm them - most of the world's reptiles are found in the tropical and sub-tropical regions where it is warmest.
They have mastered living on land and under the soil, in water (fresh water and the sea) as well as being able to live in trees (arboreal), in deserts & rain forests.
Because the reptile's body temperature is the same as the air around them, they have to bask in the sun to warm up. However in some parts of the world, the daytime temperature can be too hot which means reptiles have to find cooler areas to hide during the day and wait until the temperature drops at night to allow them to look for food. This has led to them becoming nocturnal (active at night).
The easiest way of determining if a reptile is diurnal (active during the daytime) or nocturnal is by looking at their eyes. If a reptile has round or horizontal pupils, they tend to be diurnal, if they have vertical pupils, they tend to be nocturnal.
Did you know that...
- Longest - The reticulated python has been known to reach 33 foot or 10 metres.
- Smallest - British virgin island gecko only reaches 2cm.
- Fastest - Spiny tailed iguana can run at up to 21MPH.
- Most dangerous - The inland taipan has enough venom to kill 100 people or 250,000 mice.
To find out more about the various species of reptiles that may be covered during our lectures, click on the images.