Image of Elastodenta, an extinct plesiosaur (left) and a photo of a living Sphenodon (right).

 

Photo of a Gekko, a lizard (left) and a green tree snake, Dindrelaphis (right).

Image of Elastodenta from: http://www.biltek.tubitak.gov.tr/bilgipaket/jeolojik/Fanerozoik/Mezozoik/Kretase/KretaDeniz.htm

Image of Sphenodon from : http://www.zo.utexas.edu/courses/bio213/Sphenodon.jpg 

Image of Gekko and Dindrelaphis from the Systematic Biology Biodiversity Archive.

CLASS LEPIDOSAUROMORPHA

This class contains the lepidosaurs (modern lizards, snakes, and tuataras), as well as the extinct aquatic sauropterygians.  These are diapsids (some of the sauropterygians were euryapsid).  According to Benton (2005), they are a monophyletic group defined by the following characters: the supratemporal is absent, the dorsal intercentra are absent, a particular opening (the thyroid fenestra) on the pelvic girdle, and no teeth on the lateral pterygoid flanges.

SUBCLASS SAUROPTERYGIA+

This is a group of aquatic animals that were eyryapsid (They secondarily lost their lower temporal fenestra).  They do not seem to be closely related to the ichthyosaurs. According to Benton (2005), the defining synapomorphies include: a large premaxilla, the anterior teeth (of the dentary and premaxilla) angle forward, the upper temporal fenestra is larger than the orbit.

ORDER PLACODONTIA

These semi-aquatic animals seemed to have no real adaptations to a marine existence.  They had a sprawling stance with an elongate, but not deep, tail.  However, their teeth seem to have been adapted to pry shellfish (bivalves and brachiopods) and crush them.  They had elongate incisors (prying) and a battery of pavement teeth in the maxilla and palate (crushing). 

Middle to late Triassic

Placodus 

ORDER NOTHOSAUROIDEA

SUBORDER PACHYPLEUROSAURIA

These were elongate animals with obvious aquatic adaptations.  Their limb girdles were only lightly attached to the vertebral axis so that they could not have walked on land.  The head is small on a long neck.  The animals were small (0.2-1m).

Middle Triassic

Pachypleurosaurus

SUBORDER NOTHOSAURIA

The nothosaurs were larger (1-4m) and similar to the pachypleurosaurs.  They seem to have been related to the plesiosaurs. 

Middle Triassic

Nothosaurus

ORDER PLESIOSAURIA

In general, these animals were large 2-14m and fully aquatic.  All four legs were modified as paddles.

SUBORDER PLEISIOSAUROIDEA

The long-necked plesiosaurs

FAMILY PLESIOSAURIDAE

Primitive long-necked plesiosaurs. 

Plesiosaurus.

FAMILY CRYPTOCLYDIDAE

They had long necks and a long snout and a single temporal fenestra (upper; the euryapsid condition).  They had long interlocking teeth.

Late Jurassic to late Cretaceous

Aristonectes, Cryptoclydus, Kaiwhekea, Kimmerosaurus, Muraenosaurus, Pantasaurus, Tatenectes, Tricleidus, Vinialesaurus.

FAMILY CIMOLIASAURIDAE

Long necked plesiosaurid.

Late Jurassic

FAMILY POLYCOTYLIDAE

These had short necks (secondarily derived) and once were considered to be pliosaurs.  Their elongate rostrum and short postorbital area of the skull identify them with the plesiosaurids.

Late Cretaceous

Dolichorhynchops, Edgarosaurus, Polycotylus, Thililua, Trinacrfomerum.

FAMILY ELASMOSAURIDAE

Extremely long necks, some with more than 70 cervical vertebrae.  The vertebrae had platycoelous articulations.

Late Jurassic to late Cretaceous

Alzadasaurus, Callawayasaurus, Elasmosaurus, Ertmosaurus, Hydralmosaurus, Hydrotherosaurus, Libonectes, Microcleidus, Occitanosaurus, Styxosaurus, Thalassomedon, Tuarangisaurus, Woolungasaurus.

SUBORDER PLIOSAUROIDEA

The short-necked plesiosaurs with large heads (up to one-third the length of the body) and powerful jaws.

UNASSIGNED GENUS

Thalassodracon

FAMILY RHOMALEOSAURIDAE

They had large heads and relatively long necks.

Early Jurassic

Eurycleidus, Leptocleidus, Macroplata, Rhomaleosaurus, Simolestes.

FAMILY PLIOSAURIDAE

These had very short necks and huge heads (up to 3m long).

Jurassic

Archaeonectrus, Attenborosaurus, Brachauchenius, Hauffiosaurus, Kronosaurus, Liopleurodon, Megalneusaurus, Pachycostasaurus, Peloneustes, Pliosaurus, Polyptchodon, Simolestes, Stretosaurus.

SUBCLASS LEPIDOSAURIA

This clade is characterized by having, in addition to a thyroid fenestra (abroad opening in the pelvis between the ischium and the pubis), a fused astragalus and calcaneum, and metatarsal 5 that is hooked.

ORDER SPHENODONTIDA (RHYNCHOCEPHALIA)

The have skull elements that are fused and immobile (the primitive condition).  They have a complete lower temporal bar.  The teeth are fused to the jawbone.

FAMILY SPHENODONTIDAE

Tuataras.  These lizard-like animals persist as ‘living fossils’.  They were more diverse in the Triassic with forms that ranged from herbivory to insectivory

Triassic to present

Sphenodon, Planocephalosaurus+, Homeosaurus+

FAMILY PLEUROSAURIDAE+

These animals had broad grinding teeth.  They ranged from terrestrial to aquatic.  Pleurosaurs mainly were long and slender with reduced, paddle-like limbs and very long tails.

Late Jurassic to late Cretaceous

Pleurosaurus+

ORDER SQUAMATA

These have highly mobile skulls and reduced skull elements like an incomplete lower temporal bar. 

SUBORDER LACERTILIA (SAURIA)

INFRAORDER IGUANIA

Iguanas, agamids, and tree-living chameleons.  The iguanids appear to be the sister group to the rest of the lizards.  Pleurodont teeth.

Triassic or Jurassic? to present

Iguana, Huehuecuetzpalli+

FAMILY CORYTOPHANIDAE

Casquehead Lizards. Terrestrial lizards of rainforests to semi-deserts from central Mexico to northwestern South America .  They are thin with long tails, and both sexes have elaborate crests, etc. on their heads.  The synapomorphies of the family include: a y-shapedparietal roof that supports a crest, a parietal foramen in the frontal bone, a peculiar type of caudal vertebra. 

Eocene (Cretaceous?) to present

Basiliscus, Corytophanes, Laemanctus.

FAMILY CROTAPHYTIDAE

Collard Lizards and Leopard Lizards.  Deserts and semi-arid environments of southcentral US and northern Mexico .  They have large heads and long tails.  The single structural synapomorphy is extensive skull rugosity (in most).  Carnovores that can put on very high bursts of speed. 

Eocene to present.

Crotaphytus, Gambelia.

FAMILY HOPLOCERCIDAE

Clubtails and Wood Lizards.  These are lizards of the American tropics from Panama to northwestern South America to Amazonia and over to eastern Brazil .  They have pleurodont teeth and very reduced vomers.  They occur inmany types of environments from dry forests to rainforests.  Some are partly fossorial.

Eocene (Upper Cretaceous?) to the present.

Enyalioides, Hoplocercus, Morunasaurus.

FAMILY IGUANIDAE

Iguanas.  Generally dry-adapted lizards from tropical America to southern temperate America , Fiji , and the Galapagos.  They have pleurodont teeth that are bicuspate.  They also have a distinctive type of caudal vertebrae and colic septa.  Typically terrestrial or arboreal, but some may be rock-dwellers, and one (the Marine Iguana) is semi-aquatic.  As adults, they are all herbivores and all are oviparous.

Amblyrhynchus, Brachlophus, Conolophus, Ctenosaura, Cyclura, Dipsosaurus, Iguana, Sauromalus.

FAMILY OPLURIDAE

Madagascar Iguanas.

Chalarodon, Oplurus.

FAMILY PHRYNOSOMATIDAE

North American Spiny Lizards.  They are lizards of dry habitats that occur fom northern Central America through most of the lower 48 states of the US .  They have no ptergyoid teeth, and reduced clavicular flanges. 

Eocene to the present

Callisaurus, Cophosaurus, Holbrookia, Pterosaurus, Phrynosoma, Sator, Sceloporus, Uma, Urosaurus, Uta.

FAMILY POLTCHROTIDAE

Anoles.  Arboreal lizards of South America and up into southern North America , and the West Indies .  The have pleurodont teeth and a far posterior extension of the dentary and reduced angular.  The toe pads are similar to those of gekkos.  All are oviparous.

Eocene to the present?

Anisolepis, Anolis, Diplolaemus, Enyalius, Leiosaurus, Norops, Phenacosaurus, Polychrus, Pristidactylus, Urostrophus.

FAMILY TROPIDURIDAE

Neotropical Ground Lizards.  Lizards of South America , the West Indies , and the Galapagos.  They have spiny scales and pleurodont teeth.  They have a reduced angular and a posterior extension of the splenial.  They inhabit many types of habitats from rainforests to deserts.  They generally are carnivores but can eat plant material.  Most are oviparous.

Eocene to the present.

Ctenoblepharys, Leiocephalus, Liolaemus, Microlophus, Phymaturus, Plesiomicrolophus, Stenocercus, Tropidurus, Uranoscodon.

FAMILY AGAMIDAE

Agamas or Old World Iguanids.  They extend through the old world except Madagascar and much of Europe .  Most of them have keeled scales, crests, and throat flaps.  They have acrodont teeth (they share this and other characters with the chameleons).  They range from terrestrial to semi-aquatic forms.

Cretaceous to the present.

Acanthocercus, Acanthosaura, Agama, Amphibolurus, Aphaniotus, Brachysaura, Bronchocoela, Bufoniceps, Caimanops, Calotes, Ceratophora, Chelosania, Chlamydosaurus, Cophotis, Coryphophylax, Cryptagama, Ctenophorus, Dendragama, Diporiphora, Draco, Gonocephalus, Harpesaurus, Hydrosaurus, Hypsicalotes, Hypsilurus, Japalura, Laudakia, Leiolepis, Lophocalotes, Lophognathus, Lyriocephalus, Mictopholis, Moloch, Oreodeira, Oriocalotes, Otocryptis, Phoxophrys, Phrynocephalus, Physignathus, Pogona, Psammophilus, Pseudocalotes, Pseudotrapelus, Ptyctolaemus, Rankinia, Salea, Sitana, Thaumatorhynchus, Trapelus, Tympanocryptis, Uromastyx, Xenagama, Priscama+, Mimeosaurus+.

FAMILY CHAMAELEONIDAE

Chameleons.  Distinctive arboreal lizards of Africa , Madagascar , southern Spain , the Arabian Penninsula , India , and Sri Lanka .  Their toes are fused to make two opposable pads on each foot.  In addition, the have horns, crests, etc.  Their eyes are on cone-like extensions that can move independently.  Many have prehensile tails.  They, like the agamids, have acrodont teeth.  They are insectivores and are oviparous.

Miocene to the present

Bradypodion, Brookesia, Calumma, Chamaeleo, Furcifer, Rhampholeon.

INFRAORDER GEKKOTA

Gekkos.  The gekkotans are sisters to the crown groups of lizards (Amphisbaenia+Anguimorpha+Scincomorpha).

Upper Jurassic (?) Lower Cretaceous to present.

Gekko, Ardeosaurus+(?)

FAMILY GEKKONIDAE

Geckos.  Distinctive terrestrial and arboreal lizards with a global distribution.  Generally, they occur in deserts, and tropical to subtropical habitats.  Gekkos have large heads and can have fixed eyelids or moveable eyelids.  They have distinctive adhesive pads associated with their toes that make them remarkable climbers.  In general, they are insectivores and are oviparous.  They are among the few lizards that can produce vocalizations.

Subfamily Aeluroscalabotinae: Aeluroscalabotes.

Subfamily Eublepharinae: Coleonyx, Eublepharis, Goniurosaurus, Hemitheconyx, Holodactylus.

Subfamily Gekkoninae: Afroedura, Afrogecko, Agamura, Ailuronyx, Alsophylax, Aristelliger, Asaccus, Blaesodactylus, Bogertia, Briba, Bunopus, Calodactylodes, Carinatogecko, Chonrodactylus, Christinus, Cnemaspis, Coleodactylus, Colopus, Cosymbotus, Crossobamon, Cryptactites, Cyrtodactylus, Cyrtopodion, Dixionius, Dravidogecko, Ebenavia, Elasmodactylus, Euleptes, Geckolepis, Geckonia, Gehyra, Gekko, Goggia, Gonatodes, Gonydactylus, Gymnodactylus, Haemodracon, Hemidactylus, Hemiphyllodactylus, Heteronotia, Homonota, Homopholis, Lepidoblepharis, Lepidodactylus, Luperosaurus, Lygodactylus, Matoatoa, Microscalabotes, Nactus, Narudasia, Pachydactylus, Paragehyra, Paroedura, Perochirus, Phelsuma, Phyllodactylus, Phyllopezus, Pristurus, Pseudogekko, Pseudogonatodes, Ptenopus, Ptychozoon, Ptyodactylus, Quedenfeldtia, Rhoptropus, Saurodactylus, Sphaerodactylus, Stenodactylus, Tarentola, Teratolepis, Thecadactylus, Tropiocoletes, Urocotyledon, Uroplatus.

Subfamily Teratoscincinae: Teratoscincus.

Subfamily Diplodactylinae: Bavayia, Carphodactylus, Crenadactylus, Diplodactylus, Eurydactylodes, Hoplodactylus, Lucasium, Naultinus, Nephurus, Oedura, Phyllurus, Pseudothecadactylus, Rhacodactylus, Rhynchoedura, Saltuarius, Strophurus, Underwoodisaurus.

FAMILY PYGOPODIDAE

Australasian Legless Lizards. Terrestrial lizards of Australia and into Indonesia .  These animals are limbless with no forelimbs.  The hindlimbs have lost the pelvic girdle and have been reduced to a scaly flap.  They have eyes and external ear openings.  Oviparous.

Subfamily Pygopodinae: Paradelma, Pygopus, Delma.

Subfamily Lialisinae: Lialis, Pletholax, Ophiocephalus, Aprasia.

FAMILY DIBAMIDAE

Blind Lizards.  These blind legless lizards occur in Mexico and in southeastern Asia (including Indonesia , western New Guinea , and the Philippines ).  They lack legs much like the pygopodids, but only the males have vestigial hind legs.  They have no external ear openings and only vestigial eyes.  Fossorial and oviparous.

Anelytropsis, Dibamus.

INFRAORDER AMPHISBAENIA

Amphisbaenas.  These are legless, burrowing lizards that resemble annelid worms.  The front of the skull is angled downward.

Paleocene-Eocene to present

FAMILY AMPHISBAENIDAE

Worm Lizards.  Fossorial legless lizards from Africa and South America .  They look like annelids because of the annulated scutes.  The skull is heavily ossified, and the right lung is reduced in size (as opposed to the reduction of the left lung in snakes and other legless lizards).  Mostly they are oviparous, but a few are viviparous.

Amphisbaena, Ancylocranium, Anops, Aulura, Baikia, Blanus, Bronia, Cercolophia, Chirindia, Cynisca, Dalophia, Geocalamus, Leposternon, Loveridgea, Mesobaena, Monopeltis, Zygaspis.

FAMILY TROGONOPHIDAE

Short Head Worm Lizards.  Fossorial lizards of Turkey , the Middle East , northern Africa and down to Somalia .  Their bodies are triangular in crossection, and they have a short tail.  Acrodont teeth, an enlarged sternal plate, and a very flattened snout with upturned edges.  Mostly oviparous.

Agamodon, Diplometopon, Pachycalamus, Trogonophis, Listromycter+.

FAMILY RHINEURIDAE

North American Worm Lizards.  Fossorial lizards of North America .  They have a squared off anterior edge of the head, the external nares open ventrally, many maxillary teeth, the dentary process of the coronoid overlaps the dentary.

Rhineura, Dyticonastis+, Hyporhina+, Jepsibaena+, Macrorhineura+, Oligorhineura+, Oligodontosaurus+, Ototriton+, Pseudorhineura+, Spathorhynchus+.

FAMILY BIPEDIDAE

Two-Legged Worm Lizards.  Fossorial lizards of desert soil in Mexico .  These have retained forelimbs that are somewhat functional in digging.  They have developed extra phalanges.  The pectoral girdle is shifted forward.  Oviparous.

Bipes.

INFRAORDER ANGUIMORPHA

The angiuds (varanids lizards, anguids, gila monster).  These are quite diverse.  Some of the varanids (aigialosaurs, dolichosaurs, and mososaurs) became adapted to an aquatic life and some were up to 10m long.

Upper Cretaceous to present

FAMILY ANGUIDAE

Alligator Lizards, Glass Lizards, Lateral Fold Lizards.  Terrestrial to fossorial animals of the Americas , Eurasia , and the Caribbean .  Most are legless (but some have very reduced legs) and heavily armored with scales that do not overlap, but they are underlain by osteoderms.  They have a longitudinal fold that runs the length of the margin between the dorsal and ventral part of the animal.  Both oviparous and ovoviviparous species.  Carnivores.

Subfamily Anguinae: Anguis, Ophisaurus, Pseudopus.

Subfamily Diploglossinae: Celestus, Diploglossus, Ophiodes.

Subfamily Gerrhonotinae: Abronia, Barisia, Coloptychon, Elgaria, Gerrhonotus, Mesaspis.

FAMILY XENOSAURIDAE

Knob-Scaled Lizards.  These rock-dwelling lizards occur in Central America ; and Shinisaurus is a semi-aquatic taxon in China .  The temporal arches are strong and not covered on top by skull bones.  The cranial osteoderms have fused with the skull elements amking them quite rough.  The head is rectangular in crossection.  Viviparous.

Subfamily Shinisauridae: Shinisaurus.

Subfamily Xenosauridae: Xenosaurus, Exostinus+, Restes+.

FAMILY VARANIDAE

Monitor Lizards.  Lizards of the tropics of Africa , Asia , and Australia .  Monitors have small heads, long necks, and powerful limbs and tails.  They occur mostly on land and in trees, though some are associated with water.  Oviparous with elaborate ritualized courtship behaviors.  This family has a single diverse genus.

Varanus.

FAMILY AIGIALOSAURIDAE+

Mesoleptos, Aiaialosaurus, Carsosaurus, Proaigialosaurus.

FAMILY DOLICHOSAURIDAE+

Pachyrhachis, Pachyophis, Haasiophis, Eidolosaurus, Dolichosaurus, Acetosaurus, Pontosaurus, Adriosaurus.

FAMILY MOSASAURIDAE+

Unassigned Genera: Goronysaurus, Macrosaurus.

Subfamily Halisaurinae: Eonatator, Halisaurus, Phosphorosaurus.

Subfamily Russelosaurinae (Tylosaurinae & Plioplatecarpinae): Russellosaurus, Lakumasaurus, Tylosaurus, Taniwhasaurus, Hainosaurus, Angolosaurus, Igdamanosaurus, Selmasaurus, Yaguarasaurus, Ectenosaurus, Platecarpus, Plioplatycarpus, “Mosasaurus”.

Subfamily Mosasaurinae: Amphekepubis, Moanasaurus, Kourisodon, Liodon, Dallasaurus, Clidastes, Carinodens, Globidens, Dollosaurus, Plesiotylosaurus, Prognathodon, Plotosaurus, “Mosasaurus”.

Carinodens, Leiodon, Mosasaurus, Platecarpus, Plioplatycarpus, Plotosaurus, Prognathodon, Tylosaurus.

FAMILY LANTHANOTIDAE

Earless Monitor Lizards.  This semi-aquatic lizard is limited to Borneo .  It is a monitor-like lizard with short limbs and  pronounced scales with underlying osteoderms.  Oviparous and eats fish and aquatic invertebrates.

Lanthanotus.

FAMILY HELODERMATIDAE

Gila Monsters.  Lizards of arid areas from the southwestern US to Guatamala.  Gila Monsters have a heavy body and short, stubby tail.  They have no temporal arches and 8 cervical vertebrae.  They also have poison glands.  They are solitary and diurnal.  Oviparous.

Heloderma.

INFRAORDER SCINCOMORPHA

Skinks and lacertids. 

Middle Jurassic to present

Unassigned Genera:

Paramacellodus+, Polyglyphanodon+

FAMILY GYMNOPHTHALMIDAE

Spectaled Lizards; Microteiids.  Lizards of Southern Mexico to Argentina .  These elongate lizards have reduced and sometimes nearly vestigial legs.  They occur in most habitats from deserts to rainforests.  The limbless forms usually are fossorial.  Oviparous. 

Subfamily Alopoglossinae: Apoglossus, Ptychoglossus.

Subfamily Cercosaurinae: Bachia, Anadia, Cercosaura, Echinosaura, Euspondylus, Macropholidus, Neusticurus, Opipeuter, Petracola, Potamites, Pholidobolus, Placosoma, Proctoporus, Riama, Riolama, Teuchocercus.

Subfamily Ecpleopinae: Amapasaurus, Anotosaura, Colobosauroides, Ecpleopus, Leposoma.

Subfamily Gymnophthalminae: Colobodactylus, Colobosaura, Heterodactylus, Iphisa, Stenolepis, Calyptommatus, Gymnophthalmus, Macrablepharus, Nothobachia, Procellosaurinus, Psilophthalmus, Tretioscincus, Vanzosaura, Rhachisaurus.

FAMILY TEIIDAE

Tegus and Whiptails.  Lizards of South America and the Caribbean .  They are elongate lizards with a pointed snout.  The body scales are distinctive with granular scales on the back and plate-like scales on the belly.  The head is covered by large plates.  Mainly insectivores and oviparous.  They occur in most terrestrial habitats from desert to rainforest.

Ameiva, Callopistes, Cnemidophorus, Crocodilurus, Dicrodon, Dracaena, Kentropyx, Teius, Tupinambis.

FAMILY LACERTIDAE

Wall Lizards.  Diurnal lizards of Africa and Eurasia ; 3 taxa have been introduced into North America .  They have granular scales over most of the body, larger on the head, and larger, plate-like scales on the belly, similar to the teids.  They live in mainly xeric terrestrial environments.  Insectivores and oviparous.

Subfamily Gallotiinae: Gallotia, Psammodromus.

Subfamily Lacertinae: Acanthodactylus, Adolfus, Algyroides, Australolacerta, Darevskia, Eremias, Gastropholis, Holaspis, Heliobolus, Iberolacerta, Ichnotropis, Lacerta, Latastia, Meroles, Mesalina, Nucras, Omanosauria, Ophisops, Parvilacerta, Pedioplanis, Philochortus, Podarcis, Poromera, Pseuderemias, Takydromus, Teira, Timon, Tropidosaura, Zootoca.

FAMILY XANTUSIDAE

Night Lizards.  Terrestrial and fossorials lizards of the southwestern US to Panama and Cuba .  The heads and bodies are somewhat flattened; immoveable eyelids over eyes with a vertical pupil.  They have granular scales on the back and plate-like scales on the belly.  They have a longitudinal fold of skin on each side of the body.  Mainly insectivores.  They are all parthenogenetic and viviparous.

Subfamily Cricosaurinae: Cricosaura.

Subfamily Xantusiinae: Lepidophyma, Xantusia.

FAMILY SCINCIDAE

Skinks.  They are diverse and distributed globally.  Skinks are elongate with a pointed snout.  The head is covered with plates and the body is covered with smooth cycloid scales.  The belly is covered with plate-like scales.  They have a well-developed secondary palate.  Several lines are legless.  Terrestrial, fossorial, arboreal and aquatic.  They are viviparous and oviparous.  This is the most speciose family of lizards.

Ablepharus, Acontias, Acontophiops, Afroblepharus, Amphiglossus, Androngo, Anomalopus, Apterygodon, Asymblepharus, Ateuchosaurus, Barkudia, Bartleia, Bassiana, Brachymeles, Caledoniscincus, Calyptotis, Carlia, Cautula, Chabanaudia, Chalcides, Chalcidoseps, Coeranoscincus, Cophoscinopus, Corucia, Cryptoblepharus, Cryptoscincus, Ctenotus, Cyclodina, Cyclodomorphus, Dasia, Davewakeum, Egernia, Emoia, Eremiascincus, Eroticoscincus, Eugongylus, Eulamprus, Eumeces, Eumecia, Euprepes, Eurylepis, Feylinia, Fojia, Geomyersia, Geoscincus, Glaphyromorphus, Gnypetoscincus, Gongylomorphus, Gongylus, Graciliscincus, Haackgreerius, Hakaria, Hemiergis, Hemisphaeriodon, Isopachys, Janetaescincus, Lacertoides, Lamprolepis, Lampropholis, Lankascincus, Larutia, Leiolpisma, Leptoseps, Leptosiaphos, Leritsa, Lioscincus, Lipinia, Lobulia, Lygisaurus, Lygosoma, Mabuya, Macroscincus, Marmorosphax, Melanoseps, Menetia, Mesoscincus, Mochlus, Morethia, Nangura, Nannoscincus, Nessia, Niveoscincus, Notoscincus, Novoeumeces, Oligosoma, Ophiomorus, Ophioscincus, Pamelaescincus, Panaspis, Papuascincus, Paracontias, Paralipinia, Parvoscincus, Phoboscincus, Plestiodon, Prasinohaema, Proablepharus, Proscelotes, Pseudoacontias, Pseudemoia, Pygmomeles, Riopa, Ristella, Saiphos, Saproscincus, Scelotes, Scincella, Scincopus, Scincus, Scolecoseps, Sepsina, Sigaloseps, Simiscincus, Sirenoscincus, Sphenomorphus, Sphenops, Tachygyia, Tiliqua, Trachylepis, Tribolonotus, Tropidophorus, Tropidoscincus, Typhlacontias, Typhlosaurus, Vietnascincus, Voeltzkowia.

FAMILY CORDYLIDAE

Spinytail Lizards; Girdled Lizards.  Lizards of xeric habitats in South Africa north to Angola .  They have keeled or spiny scales, especially on their tails.  Osteoderms are well developed and distributed over the body (lighter ones on the belly).  The belly has smooth scales.  Insectivores and mostly viviparous. 

Chamaesaura, Cordylus, Platysaurus.

FAMILY GERRHOSAURIDAE

Plated Lizards.  Lizards of sub-Saharan Africa and Madagascar .  Scales in rows with osteoderms underneath, but no spines.  Body with lateral folds of skin.  Some have reduced limbs.  Mainly insectivores and all oviparous.

Subfamily Gerrhosaurinae:  Cordylosaurus, Gerrhosaurus, Tetradactylus.

Subfamily Zonosaurinae: Tracheloptychus, Zonosaurus.

SUBORDER SERPENTES (OPHIDIA)

The snakes are clearly part of the squamata (morphological and molecular support), but the sister group is hotly debated.  They have been placed as sisters to the Amphisbaenia (morphological; lost les as a burrower), Anguimorpha (morphological; lost legs as a swimmer), and the Iguania+Anguimorpha (molecular).  In addition to the loss of limbs, they have increased the number of vertebrae (120-500) and increased skull mobility.  Venom occurs in some groups.

Lower Cretaceous to present

TYPHLOPOIDEA

FAMILY ANOMALEPIDAE

Dawn Blind Snakes.  Fossorial snakes of southern Central America and northern South America .  The have blunt heads and tails; and vestigial eyes.  They are limbless with no vestiges of the pelvis.  They do not have large ventral scales.  They have a toothed, moveable maxilla.  The dentary bears one tooth. Oviparous.

Anomalepis, Helminthophis, Liotyphlops, Typhlophis.

FAMILY TYPHLOPIDAE

Blind Snakes.  These fossorial snakes have a global distribution (temperate and tropical continents).  Like the Dawn Blind Snakes, they have blunt heads and tails; and vestigial eyes.  They also lack the large vebntral scales.  They do have vestigial elements of the pelvic girdle.  The dentary is toothless.  Many specialize on ants or termites. Oviparous.

Acutotyphlops, Cyclotyphlops, Ramphotyphlops, Typhlops, Xenotyphlops.

FAMILY LEPTOTYPHLOPIDAE

Slender Blind Snakes.  These fossorial snakes occur in tropical and subtropical America .  Their cranial elements are not moveable, and they have teeth only on the dentary.  Oviparous.

Leptotyphlops, Rhinoleptus.

HENOPHIDIA

FAMILY ANILIIDAE

Coral Pipe Snakes and Pipe Snakes.  These fossorial animals are distributed through South America .  Also called the False Coral Snakes, they are banded with red and black.  They have vestiges of the hindlegs and pelvic girdle.  They also have reduced eyes.  They feed on other burrowing vertebrates.  Ovoviparous.

Anilius.

FAMILY ANOMOCHILIDAE

Dwarf Pipe Snakes.  They occur on the Malay peninsula and Indonesia .

Anomochilus.

FAMILY BOIDAE

Boas and Pythons.  These large snakes occur in the tropical Americas (one occurs in the rainforests of northwestern US), Madagascar , and southwestern pacific, Australia , Asia and Africa .  They occur in habitats that range from deserts to rainforest, and some may gow to be gigantic (30m long).  Some have vestigial hind legs.  They feed on warm-blooded vertebrates which they kill by constriction.  Some have heat receptors in pits on their upper and lower labia. Oviparous.

Subfamily Boinae (Boas): Acrantophis, Boa, Candoia, Corallus, Epicrates, Eunectes, Sanzinia.

Subfamily Erycinae (Sand Boas): Calabaria, Charina, Eryx, Gongylophis.

Subfamily Pythoninae (Pythons): Aspidites, Antaresia, Apodora, Bothrochilus, Leiopython, Liasis, Morelia , Python.

FAMILY BOLYERIDAE

Round Island Boas.  Snakes of the Mascarene Islands , Round Island , extinct on Mauritius .  They have a maxilla that is split into separate anterior and posterior elements.  No vestigial hind limbs.  They feed on lizards. Oviparous.

Bolyeria, Casarea.

FAMILY CYLINDROPHIIDAE

Asian Pipe Snakes.  Fossorial snakes from Sri Lanka to the Malay Peninsula and Indonesia .  They have blunt heads and short blunt tails.  All of them have black and white checkered bellies.

Cylindrophis.

FAMILY LOXOCEMIDAE

Mexican Burrowing Pythons.  Semi-fossorial snakes from southern Mexico to Costa Rica .  They are predators of terrestrial and fossorial vertebrates and are oviparous.

Loxocemus.

FAMILY TROPIDOPHIIDAE

Dwarf Boas.  Snakes of Central and South America , the Caribbean , Malayasia, and Indonesia .  They have toothless premaxillaries; dentaries with many teeth.  Left lung absent or very reduced.  Terrestrial to arboreal and viviparous.  Predators of lizards and amphibians.

Subfamily Tropodophiinae: Trachyboa, Tropidophis.

Subfamily Ungaliophiinae: Exiliboa, Ungaliophis.

Subfamily Xenophidioninae: Xenophidion.

FAMILY UROPELTIDAE

Shield-Tailed Snakes and Short-Tailed Snakes.  Fossorial snakes of southern India and Sri lanka .  No vestigial hind legs.  They have a scaly shield at the tip of the tail.

Brachyophidium, Melanophidium, Platyplectrurus, Plectrurus, Pseudotyphlops, Rhinophis, Tereturus, Uropeltis.

FAMILY XENOPELTIDAE

Sunbeam Snakes. Terrestrial snakes from India and southern China to Borneo and Sulawesi .  The scales are dark and iridescent.  They have no pelvic remnants.  The ventral scales resemble those of colubrids.

Xenopeltis.

XENOPHIDIA

FAMILY ACROCHORDIDAE

File Snakes or Wart Snakes.  Marine, brackish and freshwater snakes from Indonesia to Australia .  Stout bodies with granular scales and loose skin with bristle-tipped tubercles.  Eyes shifted dorsally and valve-like flaps over the nares and lingual opening.  Predators of fish.  Ovoviparous.

Acrochordus.

FAMILY ATRACTASPIDIDAE

Mole Vipers and Stiletto Snakes.  Fossorial snakes of Africa .  The maxilla is reduced but has a large hollow fang that can be erected laterally.  They have long venom glands.  The are predators of fossorial mammals, snakes and lizards (some eat invertebrates).  Oviparous.

Subfamily Atractaspidinae: Atractaspis.

Subfamily Aparallactinae: Amblyodipsis, Aparallactus, Brachyophis, Chilorhinophis, Hypoptophis, Micrelaps, Elapotinus, Macrelaps, Polemon, Xenocalamus.

FAMILY COLUBRIDAE

Colubrids.  Common snakes with a global distribution.  This large group likely is paraphyletic and has no recognized shared derived characters.  They do not have fangs in the front of the mouth, and most of them have teeth that are all of the same size.  Many do have fangs with venom glands in the rear of the mouth.  Their venom and mode of delivery seems to favor the capture of cold-blooded prey.  They have exploited almost every reptilian habitat.

Unassigned Taxa: Dakotaophis+, Diadophis+, Dryinoides+, Mionatrix+, Palaeomalpolon+, Paleofarancia+, Paracoluber+, Paraoxybelis+, Protropidonotus+, Pseudocemophora+, Blythia, Cercaspis, Cyclocorus, Elapoidis, Gonglyosoma, Haplocercus, Helophis, Myersophis, Oreocalamus, Poecilopholis, Rhabdops, Tetralepis, Thermophis, Trachischium, Stilosoma.

Subfamily Elapomorphinae: Apostolepis, Elapomorphus, Phalotris.

Subfamily Boodontinae?: Boaedon?, Bothrolycus, Bothrophthalmus, Buhoma?, Chamaelycus, Cryptolycus, Dendrolycus, Dipsina, Dromicodryas, Dromophis, Duberria?, Goniotrophis, Grayia, Hormonotus, Lamprophis, Lycodonomorphus, Lycophidion, Macroprotodon, Mehelya, Montaspis?, Pseudaspis, Pseudoboodon, Pythonodipsas, Scaphiophus.

Subfamily Pseudoxyrhophiinae: Alluaudina, Compsophis, Ditypophis, Dromicodryas, Exallodontophis, Geodipsas, Heteroliodon, Ithycyphus, Langaha, Leioheterodon, Liophidium, Leiopholidophis, Lycodryas, Madagascarophis, Micropisthodon, Pararhadinaea, Bygophis, Pseuxyrophis, Stenophis.

Subfamily Colubrinae: Aeluroglena, Ahaetulla, Argyrogena, Arizona, Bogertophis, Boiga, Cemophora, Chilomeniscus, Chionactis, Chironius, Chrysopelea, Coluber, Conopsis, Coronella, Crotaphopeltis, Cryptophidion, Cyclophiops, Dasypeltis, Dendrelaphis, Dendrophidion, Dinodon, Dipsadoboa, Dispholidus, Dolichophis, Dryadophis, Drymarchon, Drymobius, Drymoliber, Dryocalamus, Dryophiops, Eirenis, Elchistodon, Elaphe, Ficimia, Gastropyxis, Geagras, Gonyophis, Gonyosoma, Gyalopion, Hapsidophrys, Hemerophis, Hemorrhois, Hierophis, Lampropeltis, Leptodrymus, Leptophis, Lepturophis, Liopeltis, Lycodon, Lycognathophis, Lytorhynchus, Masticophis, Mastigodryas, Meizodon, Oligodon, Opheodrys, Oxybelis, Philothamnus, Phyllorhynchus, Pituophis, Platyceps, Prosymna, Pseudocyclophis, Pseudoficimia, Pseudestes, Ptyas, Rhamnophis, Rhinobothryum, Rhinocheilus, Rhynchocalamus, Rhynchophis, Salvadora, Scaphiodontophis, Scolecophis, Senticolis, Sibynophis, Simophis, Sonora, Spalerosophis, Spilotes, Stegonotus, Stenorhhina, Stilosoma, Symphimus, Sympholis, Tantilla, Tantillita, Telescopus, Thelotornis, Thrasops, Trimorphodon, Xenelaphis, Zaocys.

Subfamily Psammophiinae: Hemirhagerrhis, Malpolon, Mimophis, Psammophis, Psammophylax, Rhamphiophis.

Subfamily Calamariinae: Calamaria, Calamorhabdium, Collorhabdium, Etheridgeum, Macrocalamus, Pseudorhabdion, Rabdion.

Subfamily Homalopsinae: Bitia, Brachyorrhos?, Cantoria, Cerberus, Gerarda, Enhydris, Erpeton, Heurnia, Homalopsis, Fordonia, Herpeton, Myron.

Subfamily Lycodontinae: Oligodon, Rarancia, Abastor, Braedon, Lambrophis, Heterodon, Lycodon.

Subfamily Natricinae: Adelophis, Afronatrix, Amphiesma, Amphiesmoides, Anoplohydrus, Aspidura, Atretium, Balanophis, Clonophis, Hologerrhum, Hydrablabes, Hydraethiops, Iguanognathus, Macropisthodon, Natrix, Nerodia, Opisthotropis, Parahelicops, Pararhabdophis, Regina, Rhabdophis, Seminatrix, Sinonatrix, Storeria, Thamnophis, Tropidoclonion, Tropidonophis, Virginia, Amplorhinus, Limnophis, Natricteres, Psammodynastes, Xenochrophis, Paleonatrix+, Neonatrix+.

Subfamily Dasypeltinae: Elachistodon, Dasypeltis.

Subfamily Dipsadinae: Adelphicos, Amastridium, Atractus, Chersodromus, Coniophanes, Cryophis, Dipsas, Eridiphas, Geophis, Hypsiglena, Imantodes, Leptodeira, Ninia, Pliocercus, Pseudoleptodeira, Leptognathus, Haplopeltura, Amblycehatus, Rhadinaea, Sibodon, Sibynomorphus, Tretanrhhinus, Trimrtopon, Tropidodipsas, Urotheca, Calamodontophis, Carphophis, Contia, Cristantophis, Diadophis, Diaphorolepis, Echinanthera, Emmochliophis, Enuliophis, Enulius, Gomespohis, Hydromorphus, Nothopsis, Pseudotomodon, Ptychophis, Rhadinophanes, Synophis, Tachymenis, Taeniophallus, Tantalophis, Thamnodynastes, Tomodon, Xenopholis.

Subfamily Pareatinae: Asthenodipsas, Apolopeltura, Pareas, Pseudopareas.

Subfamily Xenoderminae (Xenodermatinae)?: Achalinus, Fimbrios, Oxyrhabdium, Stoliczkaia, Xenodermus, Xylophis.

Subfamily Xenodontinae: Alsophis, Antillophis, Apostolepis, Arrhyton, Boiruna, Clelia, Conophis, Darlingtonia, Ditaxodon, Drepanoides, Elapomorphus, Erythrolamprus, Farancia, Helicops, Heterodon, Hydrodynastes, Hydrops, Hypsirhynchus, Ialtris, Liophis, Lystrophis, Manolepis, Oxyrhoppus, Phalotris, Philodryas, Phimophis, Pseudablabes, Pseudoboa, Pseudoeryx, Psomophis, Rhachidelus, Saphenophis, Siphlophis, Trpidodryas, Umbrivaga, Uromacer, Waglerophis, Xenodon, Xenobelis, Paleoheterodon+.

Subfamily Pseudoxenodontinae: Plagiopholis, Pseudoxenodon.

FAMILY ELAPIDAE

Cobras, Kraits, Coral Snakes, Sea Snakes.  Poisonous snakes that are terrestrial (global distribution, except for Europe , in tropical and subtropical areas) and marine ( Indian Ocean to the southwestern Pacific and the coasts of Central and South America ).  The two subfamilies, though related to each other are quite different in the descriptions of their life history strategies.  All elapids are venomous with fangs in the front and followed by teeth behind the fang.

Subfamily Elapinae (Cobras,Kraits, Coral Snakes).  Their fangs are fixed and cannot fold down.  The venom is delivered through the hollow fang near the tip.  The premaxillaries are toothless and the dentary is toothed.  The left lung is reduced or missing.  They prey on vertebrates and may occur in almost any terrestrial habitat (fossorial to arboreal).  Reproduction also ranges from oviparous to ovoviviparous to viviparous: Aspidelaps, Boulengerina, Bungarus, Calliophis, Dendroaspis, Elapsoidea, Hemachatus, Hemibungarus, Calliophis, Micruroides, Micrurus, Naja, Ophiophagus, Paranaja, Pseudohaje, Walterinnesia.

Subfamily Hydrophiinae (Sea Snakes).  They are laterally compressed with a tail fin.  They have salt glands and very reduced ventral scales.  The nostrils are on the dorsal side of the head and can be closed with a flap.  They prey mainly on fish.  They range from oviparous to viviparous: Acalyptophis, Acanthophis, Aipysurus, Aspidomorphus, Astrotia, Austrelaps, Cacophis, Demansia, Denisonia, Disteira, Drysdalia, Echiopsis, Elapognathus, Emydocephalus, Enhydrina, Ephalophis, Furina, Hemiaspis, Hoplocephalus, Hydrelaps, Hydrophis, Kerilia, Kolpophis, Lapemis, Laticauda, Loveridgelaps, Micropechis, Notechis, Ogmodon, Oxyuranus, Parahydrophis, Parapistocalamus, Pelamis, Pseudechis, Pseudonaja, Rhinoplocephalus, Salmonelaps, Simoselaps, Suta, Thalassophina, Thalassophis, Toxicocalamus, Tropidechis, Vermicella.

FAMILY VIPERIDAE

Vipers and Pit Vipers.  Thses snakes occur on all continents in the tropics and temperate zones except Australia .  Their heads are broad and triangular as seen from above.  Most have stout bodies with short tails.  Most have keeled scales.  Their fanges, which occur on the maxilla, are hinged and hollow.  Some have heat-sensing organs in pits (pit vipers).  They are mostly nocturnal and prey mostly on mammals and birds, but take other vertebrates.They range from oviparous to ovoviparous to viviparous.

Subfamily Crotalinae (Pit Vipers): Agkistrodon, Atropoides, Bothriechis, Bothriopsis, Bothrocophias, Bothrops, Calloselasma, Cerrophidion, Crotalus, Deinagkistrodon, Zhaoermia, Gloydius, Hypnale, Lachesis, Ophryacus, Ovophis, Porthidium, Protobothrops, Sistrurus, Triceratolepidophis, Trimeresurus, Tropidolaemus.

Subfamily Viperinae (Pitless Vipers): Adenorhinos, Atheris, Bitis, Cerastes, Daboia, Echis, Eristicophis, Macrovipera, Montatheris, Proatheris, Pseudocerastes, Vipera, Causus.

Subfamily Azemiopinae: Azemiops.