Reptiles
Reptiles form a group of cold-blooded vertebrates. It holds the following orders:
- Squamata (snakes, lizards and worm-lizards)
- Chelonii (turtles, tortoises and terrapins)
- Crocodilia (crocodiles, gavials, caimans and alligators)
- Rhynchocephalia (tuatara)
Reptiles are air-breathing; nearly all reptiles live on land. Their skin is covered in scales. They are tetrapods (having or having descended from vertebrates with four limbs). Snakes lost their limbs and move using their ventral scales or ribs. Also the Slow Worm doesn't have limbs.
Reptiles inhabit every continent with the exception of Antarctica and the open sea. Sea snakes and Sea iguanas feed in the sea, but never go far offshore and reproduce on land. Sea turtles do go very far offshore, but for reproduction they go on land.
Most reptiles are carnivorous. The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth. This is achieved, either through ovoviviparity (egg retention), or viviparity (offspring born without use of calcified eggs). The degree of viviparity varies: some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, while still others lack any yolk and provide all nutrients via a placenta.
Some species incubate their eggs (like pythons), but usually they are incubated by the sun. Most reptiles lay amniotic eggs covered with leathery or calcareous shells. There are no larval stages of development.
Asexual reproduction has been identified in squamates in six families of lizards and one snake. In some species of squamates, a population of females are able to produce a unisexual diploid clone of the mother. This asexual reproduction called parthenogenesis occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids.
The reptiles occurring in the British Isles:
Snakes:
- Grass Snake, Natrix natrix
- Smooth Snake, Coronella austriaca
- Adder, Vipera berus
- Aesculapian Snake, Zamenis longissimus
Lizards:
- Common Wall Lizard, Podarcis muralis
- Sand Lizard, Lacerta agilis
- Western Green Lizard, Lacerta bilineata
- Viviparous Lizard, Zootoca vivipara
- Slow Worm, Anguis fragilis
Terrapins:
- Red-eared Terrapin, Trachemys scripta subsp. elegans
Turtles:
- Leatherback Sea Turtle, Dermochelys coriacea
- Loggerhead Sea Turtle, Caretta caretta
- Green Sea Turtle, Chelonia mydas
- Hawksbill Sea Turtle, Eretmochelys imbricata
- Kemp's Ridley Sea Turtle, Lepidochelys kempi