Class Reptilia -  {Backward Link}

1b. Body is covered by "shell" of fused hardened scales; have toothless
            beaks. Turtles and Tortoises. Order Testudines.................................... 3

2a. Have legs and movable eyelids; mouth without "lips"; found mostly
            in or near water. Alligators, Crocodiles and Gavials.
            Order Crocodilia......................................................................................... 8

2b. May or may not have legs; teeth hidden by "lips"; common on land,
            sometimes in water; scales are often somewhat small.
            Lizards and Snakes. Superorder Squamata.......................................... 9

3a. Shells are smaller on underside, often bumpy on top. May be large.
            Aggressive predators; freshwater.   Snapping Turtles.
            Family Chelydridae.................................................................................... 4

3b. Shells are hard, glossy, oval, and somewhat flattened. Usually aquatic.
            Common Freshwater Turtles. Family Emydidae..................................... 5

3c. Shell has high dome; feet are blunt. Terrestrial.  Land 
            Tortoises.   Family Testudinidae.............................................................. 7

3d. Soft-Shelled Turtles........................................................ Family Trionychidae

3e. Leatherback Sea Turtles............................................ Family Dermochelidae

3f. True Sea Turtles.................................................................. Family Chelonidae

4a. Back shell and tail with pronounced bumps; may grow quite large.
            Southeastern U.S. Alligator Snapping Turtle.   Genus
            Macrochelys......................................................... Macrochelys temminki

4b. Bumps on tail and shell not as pronounced as in 4a; not as large. 
            North American Snapping Turtle.  Genus Chelydra.
                    ............................................................................. Chelydra serpentina

Note: Only a few of the many Emydidae Genera Listed here.

5a. Black and yellow; shell slightly domed; back hinged to close tightly;
            commonly terrestrial. Genus Terrapene................................................... 6

5b. Black, with small orange or yellow spots; up to 14 cm long.
            Spotted Pond Turtle. Genus Clemmys....................... Clemmys guttata

5c. Brown above, yellow with black rim markings below; skin is orange; 
            back is quite bumpy, with concentric grooves in scales. Northeastern
            U.S., Eastern Canada.   Wood Turtles. Genus Clemmys.
                    ............................................................................... Clemmys insculpta

5d. Black, with very faint yellow dots and streaks. Far western North 
            America. Western Pond Turtle.  Genus Clemmys.
                    ............................................................................ Clemmys marmorata

5e. Brownish, with faint orange markings; large orange spots along head. 
            East central U.S. Bog Turtle.   Genus Clemmys.
                    ....................................................................... Clemmys muhlenbergii

5c. Black with red rim markings, yellow underneath; yellow stripes along 
            head and neck, red markings on legs. Painted Turtles.
            Genus Chrysemys, Chrysemys picta,    
            Eastern Painted Turtle.................... Subspecies Chrysemys picta picta

5d. Greenish, sometimes very dark, yellow underneath with dark 
            markings;  red stripes along head and neck. Baskers and 
            Cooters......................................................................... Genus Pseudemys

5e. Brownish, with narrow yellow lines and shallow shell furrows. 
            Necks are quite long, with yellow and black stripes. Southeastern 
            U.S. Chicken Turtles. Genus Deirochelys........ Deirochelys reticularia

5f. Black with fine light flecks, yellow underneath with large black 
            markings and a notch at the rear; mouth with "smile" appearance. 
            Great Lakes region and nearby. Blanding's Turtle.
            Genus Emydoidea................................................ Emydoidea blandingii

5g. Black, with fine light flecks, pale yellow underneath. Europe, 
            Middle East and Northern Africa.  European Pond Turtle.
            Genus Emys................................................................... Emys orbicularis................................................................... Emys orbicularis

5h. Dark, with faint yellow pattern; shell has keel; tooth-edged rear of 
            shell.   Central U.S. Map Turtles................................... Genus Graptemys

5i. Shell scales with angular rings. Found in brackish water and tidewater
            streams, east coastal U.S. (Diamondback) Terrapins.
            Genus Malaclemys................................................. Malaclemys terrapin

5j. Shells from green to black, often with fine concentric markings; 
            heads, necks, and often legs are striped. Sliders. 
            Genus Trachemys   Red-Eared Slider.................... Trachemys scripta

6a. Colors and patterns highly contrasting. Central and southwestern 
            U.S.   Western Box Turtle............................................... Terrapene ornata

6b. Colors and patterns moderately contrasting. Eastern U.S.
            Eastern Box Turtle........................................................ Terrapene carolina

NOTE: Many Testudinidae Genera are not Included here.

7a. Gopher, Desert, and Texas Tortoises. Southern U.S. and Mexico.
                    .................................................................................. Genus Gopherus

7b. Galapagos Tortoises and Indian Island Tortoises............... Genus Testudo

8a. Several teeth protrude from mouth; snout tapers. Found in both
            fresh and salt water. True Crocodiles.................... Family Crocodylidae

8b. Few if any teeth protrude from mouth; snout is blunt. Found mostly in
            freshwater. Alligators and Caimans......................... Family Alligatoridae

8c. Very thin, often long snouts; fish eaters. Asia. Gavials.... Family Gavialidae

9a. Most have legs; have movable eyelids; usually have visible ear
            opening. Lizards. Order Sauria............................................................... 10

9b. Do not have legs; do not have movable eyelids; no ear openings.
            Snakes. Order Serpentes........................................................................ 14

10a. Body is scaly but scales may be small; limbs are well-developed;
            tail often moderately to very long.  Family Iguanidae............................ 11

10b. Head and neck somewhat long; body and tail somewhat thick;
            strong legs with heavily-clawed feet. Mostly tropical.  Often 
            moderate to large. Monitor Lizards.  Family Varanidae, 
            Genus Varanus......................................................................................... 12

10c. Large, blunt heads; small, beady eyes; short legs with clawed 
            feet;   scales do no overlap. Bites are poisonous.
            Family Helodermatidae, Genus Heloderma....................................... 13

10d. Large eyes; tails somewhat short; foot pads allow adherence
            to almost any surface. Geckos.................................. Family Gekkonidae

10e. Feet built for grasping branches; eyes mounted on independent
            swivel bases; have long tongues used for catching prey;   slow-
            moving, with ability to change color to match environment; scales 
            usually rounded, like beads.  Chameleons..... Family Chamaeleonidae

10f. Heads are blunt, somewhat cone-shaped; bodies are quite
            cylindrical; scales are smooth and shiny. Skinks......... Family Scincidae

NOTE: Not all Iguanidae Genera included.

11a. Small; limited ability to change color; foot pads cling to various 
            surfaces; often sold as "chameleons."  Anoles.................. Genus Anolis

11b. Short, toad-like bodies, with very short tail; covered with spines;
            live in dry environments. Horned Toads.................. Genus Phrynosoma

11c. Back with row of "spikes"; tails usually as long as body; usually
            green. Mexico to South America. Common Iguanas........ Genus Iguana

11d. Like 11c, but distributed through Caribbean Islands only.
            Includes Rock and Rhinoceros Iguanas............................ Genus Cyclura

11e. Like 11c., but colors include grays and browns; tails commonly
            covered with short spines. Greater Spinytail Iguanas.
                    ............................................................................... Genus Ctenosaura

11f. Dark, stout, with "spiked" back, bumpy face; dive in surf and feed
            upon plants near shore. Marine Iguanas. Galapagos Islands.
            Genus Amblyrhynchus............................... Amblyrhynchus cristatus

11g. Stout, yellowish and reddish, adapted to dry uplands, 
            Galapagos Islands..................................................... Genus Conolophus

11h. Found across various Polynesian islands, especially Fiji.
                    ........................................................................... Genus Brachylophus

11i. Light, creamy-colored with broad bands and tail rings of brown
            and gray. Southwest U.S. and Northwest Mexico.  Desert 
            Iguana. Genus Dipsosaurus............................... Dipsosaurus dorsalis

11j. Stout, brownish with banded tail. Southwest U.S. and Northwest
            Mexico. Chuckwalla.................................................... Genus Sauromalus

11k. Have pair of distinct black rings on neck. Central to western 
            U.S., northern Mexico. Collared Lizard, Ring-Necked Lizard.
                    .............................................................................. Genus Crotaphytus

11l. Somewhat slender; body distinctly spotted. Desert areas of 
            western U.S. Leopard Lizards........................................ Genus Gambelia

NOTE: Only a few of the Varanus species are included.

12a. Grayish-Brown. Southern Africa. Savannah Monitor Lizard.
                    ................................................................... Varanus exanthematicus

12b. Black with white-to-yellow markings. Africa, near water.
            Nile Monitor Lizard......................................................... Varanus niloticus

12c. Gray; quite large; terrestrial. Indonesia. 
            Komodo Dragon................................................... Varanus komodoensis

13a. Mostly pink and yellow; four to five bands on tail. Southwest U.S.
            and Northern Mexico. Gila Monsters................... Heloderma suspectum

13b. Mostly black; six to seven bands on tail. Western Mexico.
            Beaded Lizards........................................................ Heloderma horridum

14a. Back of head is rounded, and is usually thicker than the neck;
            snout is blunt; eyes usually have slitted pupils; kill prey by 
            squeezing until it suffocates. Family Boidae.......................................... 15

14b. Highly poisonous, with fangs in fixed position............................................ 19

14c. Highly poisonous, with fangs that can fold backward................................. 21

14d. Rarely poisonous; head usually close to same size as neck; large,
            plate-like scales on top of head. Family Colubridae............................ 29

14e. Small, with rounded body and tail; eyes shielded; no upper teeth.
            Burrowers. Blind Snakes.................................. Family Leptoyphlopidae

15a. Scales often fairly small; often bear live young. Mostly in Western
            Hemisphere. Boas. Subfamily Boinae.................................................. 16

15b. Scales somewhat larger; egg-layers. Mostly in Eastern Hemisphere.
            Pythons. Subfamily Pythoninae............................................................. 17

15c. Rarely exceed a meter in length. Burrowers. Eyes and nostrils toward
            top of head. Sand Boas. Includes Rosy Boas......... Subfamily Ericynae

NOTE: Only a few Boidae genera are included.

16a. Usually reddish brown. Popular pet. Up to 5 meters long.
            Boa Constrictor. Genus Constrictor................ Constrictor constrictor

16b. Yellowish green with black spots; semiaquatic. Up to 9 meters long. 
            Giant Anaconda. Genus Eunectes........................... Eunectes murinus

16c. Green with white markings; distinctly wedge-shaped head.
            Emerald Tree Boa. Genus Corallus........................... Corallus caninus

16d. Various colors from yellow to reddish. Rainbow Boa.
            Genus Epicrates......................................................... Epicrates cenchria

NOTE: Several Python genera are not included.

17a. Found in southern Asia and Africa. True Pythons. Genus Python......... 18

17b. Australia and islands to north and east. Rock Pythons......... Genus Liasis

17c. Head is compact, with reduced head shields; tail is very short; 
            scales are smooth. Found in loose soil and leaf mold.
            Burrowing Pythons........................................................... Genus Calabaria

NOTE: only a few Python species are included.

18a. Southeast Asia. Marked with network of dark lines; up to 
            nine meters.   Reticulated Python................................ Python reticulatus

18b. South Asia. Broad, dark markings edged with yellow on 
            light brown background; up to six meters. 
            Burmese / Indian Python................................................... Python molurus

18c. African Python........................................................................... Python sebae

18d. Ball or Royal Python..................................................................Python regius

19a. Terrestrial.  Family Elapidae....................................................................... 20

19b. Found in ocean. Tail is flattened, often paddle-shaped; eyes 
            are large. Sea Snakes............................................. Family Hydrophidae

NOTE: Only a few Elapidae genera are included.

20a. Brightly marked with red, yellow, and black rings............. Genus Micrurus

20b. Have hood; markings are usually whitish and black. 
            King Cobras.............................................................. Genus Ophiophagus

20c. Have hood; few marking on body, but "spectacle" markings on 
            back of hood. Common Oriental Cobras................................ Genus Naja

20d. No hood; various colors. Lower fangs are large. 
            Mambas...................................................................... Genus Dendroaspis

21a. Short, stocky bodies with short tails; usually not climbers. 
            Old World only. True Vipers. Family Viperidae..................................... 22

21b. Usually less stocky with longer tails; may climb. Have pits on sides 
            of heads for heat detection. Pit Vipers. Family Crotalidae.................. 24

22a. Very wide head; very stout body; have skin pocket above nostrils.
            Puff Adders. Genus Bitis.......................................................................... 23

22b. Dark, often black. Found across Eurasia. Common European 
            Viper, also known as Adder. Genus Vipera....................... Vipera berus

NOTE: Only a few Adder species included.

23a. Brown to gray, with crescent-shaped yellow markings on back. 
            Africa to Arabia. Common Puff Adder................................. Bitis arietans

23b. Geometrical markings of yellow, pale purple, and brown.
            Gaboon Viper........................................................................ Bitis gabonica

23c. White spots bound by yellow and black; two "horns" above nostrils.
            Rhinoceros Viper............................................................... Bitis nasicornis

24a. Heads heavy and distinctly triangular.  Genus Agkistrodon................... 25

24b. Tail ends in scales used as noise-maker. New World only. 
            Rattlesnakes................................................................................................ 26

24c. Central and South America. Fer-de-Lances............ Genus Trimeresurus

24d. Gray and brown with diamond markings on back. Tropical. Up to
            four meters. Bushmasters. Genus Lachesis.................. Lachesis muta

25a. Tan with brownish or reddish-brown "hourglass" markings.
            Copperheads........................................................ Agkistrodon contortrix

25b. Very dark with faint markings; mouth lining quite white, used as
            defensive display. Cottonmouths.................... Agkistrodon piscivorous

26a. Body short but thick; head has several very large scales. 
            Genus Sistrurus....................................................................................... 27

26b. Head has many small scales. Genus Crotalus........................................ 28

27a. Marked with light-ringed dark blotches; reddish-brown stripe
            down back; tail slender, rattle quite small.  Southeastern U.S. 
            Pygmy Rattlesnake....................................................... Sistrurus miliarius

27b. Brownish-gray with dark brown or gray spots; tail and rattle
            normal-sized. Central to Midwestern U.S.
            Massasauga Rattlesnake.......................................... Sistrurus catenatus

NOTE: Not all Rattlesnake species are included...

28a. Large, heavy-bodied, with row of large dark diamonds, brown 
            centers and light borders, down back, against brownish back-
            ground.  Head with dark, light-edged stripe running through 
            eye and striped snout.   Extreme southeastern U.S.
            Eastern Diamondback Rattlesnake...................... Crotalus adamanteus

28b. Similar to 28a., but with distinctly black-and-white ringed tail.
                Central to western U.S. Western Diamondback Rattlesnake.
                    ........................................................................................ Crotalus atrox

28c. Pinkish-gray or tan, with reddish stripe down back and series 
            of black chevrons. Head may or may not have stripe; tail is 
            black.   East central to southeastern U.S. Timber Rattlesnake.
                    .................................................................................. Crotalus horridus

28d. Pale, sandy to pinkish, with darker blotches down back; 
            horn-like scales over eyes. Moves with sideways motion.
            Southwestern U.S. Sidewinder..................................... Crotalus cerastes

29a. Small (less than 25 cm.) and slender........................................................... 30

29b. Small but not slender..................................................................................... 31

29c. Moderate to large size (25 cm. and longer)................................................ 32

30a. Body quite cylindrical; head is small and not very distinct from 
            the neck.  Worm Snakes............................................. Genus Carphophis

30b. Tail is cone-shaped with a distinctly sharp point.
            Sharp-Tailed Snakes............................................................ Genus Contia

30c. Reddish-brown; scales around mouth with at least some 
            distinct yellow. Yellow-Lipped Snakes........................... Genus Rhadinea

30d. Back is brown, with belly of white, pinkish, or red.
            Brown Snakes..................................................................... Genus Storeria

30e. Head is flat, with small eyes; belly is red or pink.
            Black-Headed Snakes........................................................ Genus Tantilla

31a. Stout-bodied, dark above, orangish below and on lower sides; 
            tail has distinct spine. Southeastern U.S. Mud Snakes. Genus Liodytes

31b. Quite small, with small head; short, pointed tail; back usually 
            light brown, with greenish yellow or pink belly. 
            Ground Snakes..................................................................... Genus Haldea

31c. Quite small, with stout, ring-marked body; broad, protruding 
            snout, pointed in profile; small eyes, round pupils. Burrowers.
            Banded Sand Snake............................................. Genus Chilomeniscus

NOTE: Only some of the approximately 300 Colubridae genera are listed.

32a. Often brightly marked; eat rodents and other snakes; resistant to
            many snake venoms. King Snakes and Milk Snakes.
                    ............................................................................ Genus Lampropeltis

32b. Back marked with three lengthwise stripes on dark background.
            Garter Snakes and Ribbon Snakes......................... Genus Thamnophis

32c. Large, long and slender, with wide head; can move very quickly.
            Whip Snakes and Racers.................................................. Genus Coluber

32d. Fairly large, with a thick body; dark, blue-black color, with wide,
            smooth scales. Indigo Snakes.................................. Genus Drymarchon

32e. Moderate size but slender; body somewhat flattened, and commonly
            marked with reddish or brown blotches.   Corn Snakes, 
            Rat Snakes, Fox Snakes..................................................... Genus Elaphe

32f. Moderate to large size; body is cylindrical, with lengthwise stripes
            of red or orange and two rows of black spots on belly; tail is
            spike-like.  Rainbow Snakes............................................. Genus Abastor

32g. Slender, with a narrow head; lower jaw fits well into upper jaw;
            scales are smooth and glistening. Glossy Snakes.......... Genus Arizona

32h. Head is red with black band behind eyes; body banded with 
            red, yellow, and black on top, belly yellow or white.
            Scarlet Snakes............................................................ Genus Cemophora

32i. Head is flattened and shovel-like; top of body banded in black,
            yellow, and sometimes red. Shovelnose Snakes...... Genus Chionactis

32j. Relatively small; head is flat, with a broad, rounded snout; usually
            has a yellow or orange band behind head; back is gray, black,
            or green; belly is yellow, orange, or red, sometimes with spots.
            Ringnecked Snakes....................................................... Genus Diadophis

32k. Large, heavy body; head not distinct from neck; short tail ends in
            horn-like spine. Horn Snakes........................................... Genus Farancia

32l. Body is thick; snout is flattened and curved upward; may flatten,
            almost cobra-like, when threatened. 
            Hog-Nosed Snakes....................................................... Genus Heterodon

32m. Back is light brown with about 50 dark brown spots; belly whitish;
            snout projects beyond mouth. Mildly poisonous.
            Night Snakes................................................................. Genus Hypsiglena

32n. Large, long and slender; head is narrow, with white spot in front
            of eyes; back is usually marked with pattern, belly usually with 
            some pink or reddish-pink. Whip Snakes and Racers.
                    .............................................................................. Genus Masticophis

32o. Head usually quite distinct from neck; scales with middle keel or
            ridge; commonly found in or near water. Water Snakes.... Genus Natrix

32p. Back and head green; belly yellow, greenish-yellow, sometimes
            white. Green Snakes.................................................... Genus Opheodrys

32q. Large, with somewhat thick bodies; back marked with spots or
            "saddles"; has large, vertical nose plate; may hiss or growl when
            threatened. Pine Snakes, Bull Snakes, Gopher Snakes
                    ................................................................................... Genus Pituophis

32r. Head is quite narrow; back with dark patches and bands of red, 
            white, or yellow; commonly speckled. Long-Nosed Snakes.
                    ............................................................................ Genus Rhinocheilus

32s. Head with blunt shield over nose; lengthwise yellow and brown 
            stripes.   Patchnose Snakes.......................................... Genus Salvadora