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ClassificationIntroductionReptiles and amphibians are not closely related. Even a superficial consideration will bear this out: Reptiles are dry and scaly; amphibians have no scales. Reptiles produce a complex, amniotic egg; amphibians produce a very simple, gelatinous egg. Reptiles looks pretty much the same as young and adults; amphibians go through metamorphosis and live a "double life". One might ask then, why are these two groups lumped together into a single field of study, herpetology? The simple--though perhaps less satisfying--answer would be, historical reasons. The word "herp" derives from the Greek words herpeton, meaning "four-legged reptile", and herpein, meaning "to crawl". As we know, the suffix "-ology" refers to the study of something. So putting it all together, we have herpetology as "the study of 4-legged crawling things". Information presented on this page has come from a variety of sources, but special mention should be made of the Tree of Life and Center for North American Herpetology websites. On the menu below, click a "+" to open a particular branch (or "-" to close it). Then click on a title to show information about that branch or species. Menu
Origin of LifeCharacteristicsAll organisms--whether we are talking about a dog, tree, mushroom, bacterium, human, bird, etc.--share common characteristics that identify them as living. An organism is made up of one or more cells, it grows and develops, it responds to stimuli in the environment, it stores and uses energy, it contains DNA, it reproduces. Throughout the Earth's 4.5 billion years of existance, colossal changes have occurred. Life, which is thought to have its origins on Earth 3.5 billion years ago, has struggled over time to meet the challenges of an ever changing environment. These trials, tribulations, and successes get imprinted into the very genetic makeup of organisms and are translated into form and function. The passing on of traits from generation to generation, coupled with mechanisms of genetic isolation and sheer time, has left us with a bewildering diversity of extant organisms. Each is an end-product of 3.5 billion years of experimentation. Major GroupsWhile the exact arrangement of these lineages is hotly debated, the major groups are Archaea ("ancient bacteria" / extremeophiles), Eubacteria ("true bacteria"), and Eukaryotes (protists, plants, fungi, animals, etc.). EukaryotesCharacteristicsEukaryotes are organisms made up of one or more advanced cells. These cells have a true nucleus, cytoskeleton, membrane-bound organelles, and discrete chromosomes. Major GroupsThe major groups include all non-bacterial organisms: Protists, Plants, Fungi, and Animals. MetazoaCharacteristicsAnimals are a diverse group of multicellular consumers. In addition, they generally follow a diploid life cycle. Major GroupsThe major groups include Porifera (sponges), Ctenophora (comb-jellies), Cnidaria (anemones, corals, jellyfish, etc.), and Bilateria (animals with bilateral symmetry). ChordataCharacteristicsChordates are identified by having, at some point in their development, a notochord, a nerve cord, and pharyngeal clefts. Some of these features may be present only in the embryo. The vast majority of extant chordates are vertebrates. Major GroupsThe major groups include Urochordata (tunicates), Cephalochordata (amphioxus), and Vertebrata (animals with a backbone). AmphibiaCharacteristicsAmphibians are characterized as having smooth, slimy skin that is semi-permeable to allow for water and gas exchange. The word amphibian derives from the Greek amphibios, which means "living a double-life". Although many modern amphibians provide exceptions, the standard life cycle is that eggs are laid in water, larva hatch and live for a portion of time in water before going through metamorphosis, and then live as air-breathing adults on land. Major GroupsThe major extant groups include Caecilians, Frogs, and Salamanders. AnuraCharacteristicsFrogs and toads are characterized by long hind limbs, protruding eyes, and absence of a tail. The larvae, called tadpoles, look and act dramatically different than adults. Major GroupsThe major North American groups include Bufonidae (true toads), Hylidae (treefrogs), Microhylidae (microhylid frogs and toads), Ranidae (true frogs), and Scaphiopodidae (North American spadefoots). BufonidaeCharacteristicsThe true toads are characterized by having dry, warty skin, parotoid glands, and they hop. GeneraThe genus found in Arkansas is Bufo (true toads). HylidaeCharacteristicsThe treefrogs, a diverse group, are generally characterized by having slim waists, long limbs, and females grow larger than males. Many are arboreal. GeneraThe genera found in Arkansas are Acris (cricket frogs), Hyla (treefrogs), and Pseudacris (chorus frogs). MicrohylidaeCharacteristicsThe microhylid frogs and toads are typically small in size with squat bodies and narrow mouths. GeneraThe genus found in Arkansas is Gastrophryne (narrowmouth toads). RanidaeCharacteristicsThe true frogs, as the name suggests have "typical" frog features: smooth skin, large hind limbs for jumping, and extensive webbing between toes. GeneraThe genus found in Arkansas is Rana (true frogs). ScaphiopodidaeCharacteristicsThe fossorial North American spadefoots are characterized by a single black spade on the underside of each hind foot. They lack parotoid glands. Pupils are vertically elliptical. GeneraThe genera found in Arkansas are Scaphiopus (southern spadefoots) and Spea (western spadefoots). CaudataCharacteristicsSalamanders and newts are generally characterized by limbs of roughly the same length and the presence of a tail. The larvae often look and act dramatically different than adults. Major GroupsThe major North American groups include Ambystomatidae (mole salamanders), Amphiumidae (amphiumas), Cryptobranchidae (hellbenders), Plethodontidae (lungless salamanders), Proteidae (mudpuppies and waterdogs), Salamandridae (newts), and Sirenidae (sirens). AmbystomatidaeCharacteristicsThe mole salmanders are generally large, stocky, with a broad head, and fossorial. Nasolabial grooves are absent. Costal grooves are present and distinct. Rarely seen exposed during most of the year, breeding migrations occur during early spring or fall rains. Larvae are quite large. GeneraThe genus found in Arkansas is Ambystoma (mole salamanders). AmphiumidaeCharacteristicsThe aquatic amphiumas are characterized as having a long, tubular, eel-like body with miniature limbs. As adults, gills are lacking, but gill slits remain. GeneraThe genus found in Arkansas is Amphiuma (amphiumas). CryptobranchidaeCharacteristicsThe aquatic hellbenders are extremely large and wrinkled. As adults, gills are lacking, but gill slits remain. GeneraThe genus found in Arkansas is Cryptobranchus (hellbenders). PlethodontidaeCharacteristicsAs the name suggests, lungless salamanders lack lungs. Respiration occurs through the skin. Otherwise, this group is quite diverse, accounting for over half of the known species of salamanders! GeneraThe genera found in Arkansas are Desmognathus (dusky salamanders), Eurycea (brook salamanders), Hemidactylium (four-toed salamander), and Plethodon (woodland salamanders). ProteidaeCharacteristicsThe aquatic waterdogs and mudpuppies are relatively large, somewhat wrinkled, and with large external gills. Adults are paedomorphic, meaning they retain many larval characteristics into adulthood. GeneraThe genus found in Arkansas is Necturus (waterdogs and mudpuppies). SalamandridaeCharacteristicsNewts are characterized by having drier skin that secretes poisons. Some members have a three-stage life cycle: aquatic larva, terrestrial eft (salamander equivalent of a teenager), and aquatic adult. GeneraThe genus found in Arkansas is Notophthalmus (eastern newts). SirenidaeCharacteristicsThe aquatic sirens are relatively long, eel-like in appearance, and with external gills. Only miniature front limbs are present. GeneraThe genus found in Arkansas is Siren (sirens). ReptiliaCharacteristicsReptiles are characterized as having rough, dry, and scaly skin. They produce an amniotic egg. The word reptile derives from the Latin repere, which means "to creep". Major GroupsThe major extant groups include Amphisbaenians, Crocodilians, Lizards, Snakes, Sphenodon (i.e. the tuataras of New Zealand), and Turtles. CheloniaCharacteristicsTurtles, tortoises, and terrapins are characterized as having a bony shell consisting of a carapace (upper shell) and plastron (lower shell). They are anapsids (lacking lateral openings in the side of the skull). Major GroupsThe major extant groups include Pleurodira (side-necked turtles) and Cryptodira (all other living turtles). ChelydridaeCharacteristicsSnapping turtles are characterized by having extremely large heads and long tails. They have powerful jaws and a hooked beak. The head and limbs cannot be fully retracted into the shell. GeneraThe genera found in Arkansas are Chelydra (snapping turtle) and Macrochelys (alligator snapping turtle). EmydidaeCharacteristicsThe diverse group of box and water turtles has no easily recognizable characteristics. (Common shared characteristics include genetic and internal morphological similarities.) GeneraThe genera found in Arkansas are Chrysemys (painted turtles), Deirochelys (chicken turtle), Graptemys (map turtles), Pseudemys (redbelly turtles and cooters), Terrapene (box turtles), and Trachemys (sliders). KinosternidaeCharacteristicsMud and musk turtles, as their names suggest, typically live in muddy waters and when disturbed can emit a pungent musk. The carapace is generally oval in shape and the plastron is reduced. GeneraThe genera found in Arkansas are Kinosternon (mud turtles) and Sternotherus (musk turtles). TrionychidaeCharacteristicsThe aquatic softshells are easily recognized as "swimming pancakes". The carapace lacks scutes and is covered in a leathery skin. GeneraThe genus found in Arkansas is Apalone (softshells). CrocodiliaCharacteristicsCrocodiles, alligators, caimans, and gharials are characterized by having thecodont dentition (teeth set in bony sockets), osteoderms (bony plates in the skin), and a four-chambered heart. They are diapsids (with upper and lower openings in the side of the skull). Their closest living relatives are birds! Major GroupsThe major extant groups include Alligatoridae (alligators and caimans), Crocodylidae (crocodiles), and Gavialidae (gharials and false gharials). AlligatoridaeCharacteristicsAlligators and caiman differ superficially from their crocodile cousins in having a wider and shorter snout, darker coloration, and lack of a protruding fourth lower tooth. GeneraThe genus found in Arkansas is Alligator (alligators). SquamataCharacteristicsSquamata, the lizards (a paraphyletic group) and snakes, are characterized by having increased skull flexibility, reduction of limb size, body elongation, and the presence of hemipenes in males and hemiclitori in females (these are paired sex organs). They are diapsids (with upper and lower openings in the side of the skull). Major GroupsThe major extant groups include Iguania (iguanas and relatives), Gekkota (geckos), Anguimorpha (monitors and relatives), Scincomorpha (skinks and relatives), Serpentes (snakes), and Amphisbaenia (worm lizards). "Lizards"CharacteristicsTraditionally recognized as the Lacertilia, lizards are known to comprise a paraphyletic group. As such, characteristics of each group vary. The "standard" lizard has four limbs, external ear openings, and movable eyelids. Major GroupsThe major North American groups include Anguidae (glass lizards and alligator lizards), Crotaphytidae (collared and leopard lizards), Gekkonidae (geckos), Helodermatidae (gila monsters), Iguanidae (iguanas), Phrynosomatidae (spiny lizards), Polychrotidae (anoles), Scincidae (skinks), and Teiidae (whiptails, racerunners and ameivas). AnguidaeCharacteristicsGlass and alligator lizards are plated in non-overlapping scales. Often a ventrolateral groove is present. While representatives may have limbs, those found in Arkansas are limbless. The presence of eyelids and external ear openings may help distinguish these lizards from snakes. GeneraThe genus found in Arkansas is Ophisaurus (glass lizards). CrotaphytidaeCharacteristicsCollared and leopard lizards are characterized by having large heads, long back limbs, and long tails. Often these live in drier, desert-like habitats. In Arkansas, Collared Lizards are inhabitants of rocky glades. GeneraThe genus found in Arkansas is Crotaphytus (collared lizards). PhrynosomatidaeCharacteristicsSpiny lizards are typically smallish and rough scaled. Teeth detention, which is pleurodont, is often cited as a major characteristic to distinguish this group from similar forms. GeneraThe genus found in Arkansas is Sceloporus (spiny lizards). PolychrotidaeCharacteristicsAnoles are characterized by the ability to change colors (browns and greens), the presence of a throat dewlap, and surface-griping folds on the toes. Representatives of this group are typically arboreal. GeneraThe genus found in Arkansas is Anolis (anoles). ScincidaeCharacteristicsSkinks are characterized by having elongated bodies with smooth, non-overlapping scales. GeneraThe genera found in Arkansas are Plestiodon (North American skinks) and Scincella (ground skinks). TeiidaeCharacteristicsWhiptails and racerunners are characterized by having granular dorsal scales and large, rectangular ventral scales. The head is covered in larger scale plates. GeneraThe genus found in Arkansas is Aspidoscelis (North American whiptails and racerunners). SerpentesCharacteristicsSnakes are characterized by a lack of external limbs (though some older forms have "spurs"), a lack of eyelids, a lack of ear structures, a lack of vocal chords, carnivorous diet, elongated body, short tail, a large number of vertebrae, flexible skull and jaw bones, reduction or absence of one of paired organs (such as the lungs, in which one is greatly reduced), backward-curving teeth, and a forked tongue and related sensing organ in the roof of their mouth. Major GroupsThe major North American groups include Boidae (boas), Colubridae (harmless egg-laying snakes), Crotalidae (pitvipers), Dipsadidae (slender rear-fanged snakes), Elapidae (coral snakes, cobras, and kraits), Hydrophiidae (sea snakes), Natricidae (harmless live-bearing snakes), and Xenodontidae (robust rear-fanged snakes) CrotalidaeCharacteristicsThe large-bodied and venomous pitvipers are characterized by having long, folding fangs and two heat-sensing pits (situated between the eyes and nostrils). GeneraThe genera found in Arkansas are Agkistrodon (copperhead and cottonmouth), Crotalus (rattlesnakes), and Sistrurus (pigmy rattlesnakes and massasaugas). ElapidaeCharacteristicsThe venomous elapids are characterized by having anteriorly located fixed fangs. Some of the most venomous and dangerous snakes known in the world belong to this group. GeneraThe genus found in Arkansas is Micrurus (eastern coral snakes). ColubridaeCharacteristicsThe colubrids comprise a diverse group that contains over half the known species of snakes. Generally, representatives of this group are harmless egg-layers with "standard" snake characteristics. Scientists have long tried to divide this unwieldy conglomeration into smaller, more scientifically-meaningful groups, but success has been debatable. GeneraThe genera found in Arkansas are Cemophora (scarlet snake), Coluber (racers), Lampropeltis (kingsnakes and milk snake), Masticophis (whipsnakes, striped racers, and coachwhips), Opheodrys (rough green snake), Pantherophis (North American rat snakes and fox snakes), Sonora (ground snakes), and Tantilla (blackhead, flathead, and crowned snakes). DipsadidaeCharacteristicsRepresentatives of this group are generally small and slender with rear fangs. Although they produce a mildly toxic saliva for subduing prey, they are harmless to humans. GeneraThe genera found in Arkansas are Carphophis (worm snakes) and Diadophis (ringneck snake). NatricidaeCharacteristicsRepresentatives of this group are characterized by being nonvenomous/fangless and ovoviviporous (a condition where eggs are produced but retained in the female). GeneraThe genera found in Arkansas are Nerodia (water and salt marsh snakes), Regina (crayfish snakes), Storeria (brown and redbelly Snakes), Thamnophis (garter and ribbon snakes), and Virginia (earth snakes). XenodontidaeCharacteristicsRepresentatives of this group are generally heavy-bodied with rear fangs. Although they produce a mildly toxic saliva for subduing prey, they are harmless to humans. GeneraThe genera found in Arkansas are Farancia (mud snake and rainbow snake), and Heterodon (hognose snakes). |
