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An Introduction to Reptiles and Amphibians

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    An Introduction to Reptiles and Amphibians

    Despite not having close evolutionary ties, reptiles and amphibians are often studied together because of their similarities, under the term herpetology. Amphibians and reptiles (collectively known as herptiles, or simply herps) can be divided into two separate classes: Amphibia and Reptilia. Amphibia can be further divided into three clades: Gymnophiona (Caecilians), Caudata (Salamanders) and Anura (Frogs and Toads). The group Reptilia is also represented by three clades: Archosauria (Crocodilians and Birds), Testudines (Chelonians), and Lepidosauria (Squamates and Tuatara).






    The term "amphibian" is derived from the Greek word amphibios (a being with a double life). Living amphibians are the descendants of the first terrestrial vertebrates. There ancestors were lobe-finned fishes (Sarcopterygii) which first appeared more than 400 million years ago. The first fossils of four legged (or tetrapod) aquatic animals appeared 360 million years ago. This group of early animals are known as ichthyostegalians (demonstrated in the image above). Today, amphibians can be found inhabiting a wide variety of environments, remaining closely tied to water or moist microhabitats for reproduction. Amphibians typically start their life in fresh water and move on to dry land as adults. They are prone to drying quickly but some species have evolved spectacular adaptations which allow them to live in extreme environments, including deserts.


    The term "reptile" is derived from the Latin word repere (to creep). The ancestors of modern reptiles appeared around 320 million years ago, these animals are also the ancestors of modern birds and mammals. These ancient animals were able to reproduce on land in the absence of water and had developed an efficient skin barrier that reduced excessive water loss through dehydration. This allowed them to adapt to a more terrestrial lifestyle. There are approximately 10,000 known species of reptile which have evolved into a variety of incredibly diverse forms and inhabit a huge range of different environments, from the oceans to the deserts. Reptiles are defined as having scales or scutes, lay land-based hard-shelled eggs and possess ectothermic metabolisms (cold-blooded). This definition excludes birds, which, although are classed as archosaurs alongside crocodilians, have traditionally been treated as a separate group of vertebrates.


    Reptiles use their behaviour to regulate their core body temperature and have the ability to hibernate or aestivate in extremes of cold or heat, respectively. Herptiles are "cold-blooded" in the sense that they do not produce their own body heat. The term cold-blooded, however, is not an accurate one as they are able to warm their bodies by basking, more accurately they are ectothermic meaning they absorb heat from their surrounding environment (such as from the sun or on objects warmed by the sun like rocks). This term is an imprecise description as reptiles do produce low levels of heat through internal metabolic processes and some reptiles can produce their own body heat through shivering-thermogenesis. Reptiles may also be described as poikilotherms, meaning they have a variable body temperature which depends on the temperature of their environment. This too, however, is not completely accurate as some reptiles are able to maintain a relatively consistent body temperature within a very narrow band (+/- 2˚C). Because reptiles vary so much in their approach to thermoregulation, there is not a single precise term which can describe all their thermoregulatory abilities. Ectothermic is the most commonly used term as it is the truest description to hand.

    Amphibia and Reptilia; a brief look at current extant groups

    AMPHIBIA

    Caecilians


    Tropical amphibians that superficially resemble earthworms or snakes as they completely lack limbs. They are burrowing animals, as evidenced by their wedge-shaped heads and blunt tails, and spend much of their time underground.


    Salamanders


    Salamander - Newt - Siren

    These are small animals that superficially resemble lizards but are smooth-skinned and may live both on land and in water. Some species of salamander are completely aquatic, some burrow, many are terrestrial and many others are arboreal, living in the forest canopy. "Salamander" is the common name for the clade Caudata which includes 9 families. The term "Newt" is sometimes used to describe relatively small salamanders. The term "Siren" is used to describe aquatic salamanders which lack hind limbs.



    Anurans


    Frog - Toad

    These amphibians are unlike other vertebrates in having robust, tailless bodies with no obvious neck and well developed limbs. The hind legs are typically nearly twice the length of the body. Not all anurans hop, some walk and others are completely aquatic and use their legs to propel themselves through the water.

    Distinctions between frogs and toads are not always clear (scientifically speaking their are no distinctions) but here are some generic colloquial differences:

    Frogs:
    Hind legs are long and strong, adapted for leaping and swimming, skin is smooth and slimy and eyes bulge. - Most commonly found near water.

    Toads:
    Warty and dry skin with large bodies and stubby legs adapted for walking. - Most commonly found on land.
    Last edited by Cat001; 11-22-2017 at 03:40 PM.

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    REPTILIA


    Chelonians


    Turtle - Terrapin - Tortoise

    Like the anurans, these animals are very distinctive. The body is encased within upper and lower bony shells (carapace and plastron, respectively) known as the shell.

    Turtles:
    British: Sea-dwelling aquatic Cheleonian, only ventures on to land to lay eggs (Sea Turtles).
    American: Aquatic or semi-aquatic chelonian, may live in sea or fresh water but ventures on to land to bask (often interchangeable with terrapin). Sometimes describes land-dwelling chelonians (Box Turtle).

    Terrapins:
    British: A freshwater or brackish-water aquatic chelonian.
    American: Often used to describe brackish water aquatic chelonians.

    Tortoises:
    An exclusively land-dwelling chelonian.


    Crocodilians


    Crocodile - Alligator - Gharial

    Interestingly, crocodilians and birds are closely related, both being living examples of Archosaurs. Crocodilians are semi-aquatic, predatory reptiles with armoured skin and powerful tails and limbs. The limbs allow mobility on land although terrestrial activities are usually restricted to basking and nesting.

    Crocodiles:
    The upper jaw is not as broad as the Alligators. The 4th tooth back from the front on the lower jaw is greatly enlarged. The tip of this tooth is clearly visible.

    Alligators:
    Broad snouted ("shovel shaped"). Teeth aren't as obvious as with Crocodiles, the largest tooth fits into a socket so the tip is hidden. Alligators are divided amongst four genera (Alligator, Caiman, Melanosuchus, Palpebrosus). The American Alligator is the most well-known.

    Gharial:
    Greatly elongated snout specialised for eating fish.


    Squamata


    Lizard - Snake - Amphisbaenian

    Comprises of the lizards, snakes and amphisbaenians. They are the most diverse and species rich group of reptiles, occupying habitats ranging from tropical oceans to temperate mountaintops. Both snakes and amphisbaenians are descended from lizards.

    Lizards:
    The term lizard is applied to any squamate that isn't a snake or amphisbaenian, this group is highly diverse. There are approximately 4500 species of lizard. Unlike snakes, lizards typically have four legs (with the exception of legless lizards) and external ears. Many species of lizard can detach their tail if threatened by a predator.

    Snakes:
    Snakes are carnivorous, legless reptiles with elongated bodies and belong to the suborder: Serpentes. They can be distinguished from the legless lizards by their lack of eyelids and external ears. Snakes are capable of swallowing prey much larger than their heads due to a highly mobile jaw. The mandible is not fused at the front so the snake can move the left side and right side of the jaw independently. Snakes do not dislocate their jaws.

    Amphisbaenians:
    Most amphisbaenians are elongated with short stubby tails, scales arranged in rings around the body and are limbless (with the exception of Bipes, which has two mole-like front limbs).


    Tuatara



    These reptiles resemble most lizards but diverged early from the the squamates and are now part of a distinct lineage, order Rhynchocephalia, endemic to New Zealand. The tuatara flourished around 200 million years ago, but in modern times there are only two extant species of tuatara (Sphenodon punctatus and Sphenodon guntheri) making them 'living fossils'.

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    Reptiles as Pets


    Pet Reptiles and Amphibians are increasing in popularity due to their wide availability. Before getting such a pet you have a commitment to research first as each individual species will have its own specific requirements, if you fail to meet these requirements it may result in ill health and eventual premature death. You should also check for a veterinary surgery in your area that is able to treat reptiles and perhaps join a herpetological society such as a reptile forum as there will come a time when you will want to seek advice. It is good practice to put aside some money for emergency vet costs if needed, as you also have a duty of care and should make every effort to resolve any medical complaint that may arise. “I can’t afford it” is an often used excuse for neglect, precautions to have money on hand for such emergencies is a must.

    Many reptiles in captivity do not reach adulthood due to inadequate husbandry. Frequently new and uneducated owners make poor choices for enclosures, environmental temperature/humidity as well as food based on items that are sold in pet stores and advice from outdated text, well-meaning friends and “breeders”. Decisions are sometimes also guided by a wish for enclosures to look aesthetically pleasing without knowledge of species-specific needs or behaviours that should be considered when making choices concerning substrate, heat, light and humidity sources. It is extremely important to consider necessary enclosure size and husbandry issues such as light, temperature gradient, humidity (or lack of) adequate hiding and need for artificial full-spectrum light.

    You should also make yourself aware of the species life span and decide whether you are willing to commit yourself to the care of the animal for this length of time. Some species can live for 20 years such as Leopard Geckos, Corn Snakes and Blue Tongued Skinks, some for considerably longer with a lifespan that may rival a human’s. You should also place serious consideration into how large the animal will grow and decide if you have the space to accommodate the animal once it reaches full size. Furthermore, some species of reptile require complex and specialised care so you need to be sure that you are ready to commit yourself to provide for this care for the remainder of the animals life. Some reptiles are also carnivorous or may have expensive feeding requirements so when purchasing a pet reptile, do first consider the cost of feeding and whether you are able to feed insects or other animals to your pet as required.

    For beginners you must be aware that some species are more suitable as a first time pet reptile than others. For instance, a Tokay Gecko may look very attractive but it is not recommended to beginners because of their aggressive nature. Some species also require very specific care in which basic knowledge will not be adequate. The most popular species which are more suitable for beginners include the Leopard Gecko, Bearded Dragon, Blue Tongued Skink, Corn Snake, Ball Python, Hermann's Tortoise, Horsfield’s Tortoise, Red Eared Slider and other such tame and hardy species. Snakes are perhaps the best animals for beginners, requiring less maintenance and do not require supplementing or a complex feeding regime. Lizards are a close second but have more complex nutritional needs than the snakes (varied diet and vitamin/mineral supplementation). Turtles and Tortoises perhaps require the most maintenance out of all the reptiles considered suitable for beginners.

Please reply to this thread with any new information or opinions.

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