Geckos are small, mostly carnivorous lizards that belong to the suborder Gekkota. They have a wide distribution, found on every continent except Antarctica, and have adapted to habitats ranging from deserts to jungles. They are the most species-rich group of lizards, with about 1,500 different species worldwide
But which of the following is most closely related to a gecko? To answer this question, we need to look at the classification of geckos and their evolutionary relationships with other reptiles.
Geckos are part of the order Squamata
Geckos are part of the order Squamata, which includes all lizards and snakes. Squamates are characterized by having scales, movable jaws, and paired hemipenes (male reproductive organs). Squamates are divided into three suborders: Gekkota, Iguania, and Serpentes
Gekkota is the suborder that contains all geckos and their closest relatives. Iguania is the suborder that contains iguanas, chameleons, agamids, anoles, and other lizards with acrodont teeth (teeth fused to the top of the jaw). Serpentes is the suborder that contains all snakes
Geckos are divided into six families
Within the suborder Gekkota, geckos are divided into six families: Carphodactylidae, Diplodactylidae, Eublepharidae, Gekkonidae, Phyllodactylidae, and Sphaerodactylidae. These families differ in their morphology, ecology, and behavior
Carphodactylidae is a family of geckos endemic to Australia. They have thick tails that can store fat and water. They are mostly nocturnal and arboreal (living in trees)
Diplodactylidae is a family of geckos that includes about 150 species from Australia, New Zealand, New Caledonia, and other Pacific islands. They have slender tails that can be easily detached when threatened. They are mostly nocturnal and terrestrial (living on the ground)
Eublepharidae is a family of geckos that includes about 30 species from Asia, Africa, North America, and South America. They have movable eyelids and claws on their toes. They are mostly nocturnal and terrestrial
Gekkonidae is the largest family of geckos, with about 950 species from all continents except Antarctica. They have adhesive pads on their toes that allow them to climb smooth and vertical surfaces. They are mostly nocturnal and arboreal. Some species can vocalize and change color
Phyllodactylidae is a family of geckos that includes about 120 species from Africa, Europe, Asia, North America, South America, and Oceania. They have leaf-shaped toes with adhesive pads. They are mostly nocturnal and arboreal or saxicolous (living on rocks)
Sphaerodactylidae is a family of geckos that includes about 200 species from Africa, Europe, Asia, North America, South America, and Oceania. They have round pupils and granular scales. They are mostly nocturnal and terrestrial or saxicolous. Some species are very small and can fit on a coin
Based on molecular data, geckos are more closely related to some lizards than others within the order Squamata. The closest relatives of geckos are pygopods (legless lizards) and dibamids (blind lizards), which together form the clade Pygopodomorpha within Gekkota. Pygopods and dibamids have lost their limbs independently in adaptation to burrowing lifestyles.
The next closest relatives of geckos are skinks (Scincidae), which form the sister group of Gekkota within Squamata. Skinks are a diverse group of lizards with smooth scales and cylindrical bodies. Some skinks have reduced or absent limbs as well.
The next closest relatives of geckos are anguimorphs (Anguimorpha), which include monitor lizards (Varanidae), alligator lizards (Anguidae), helodermatids (Gila monsters and beaded lizards), and xenosaurs (knob-scaled lizards). Anguimorphs are a group of lizards with well-developed limbs and forked tongues. Some anguimorphs are venomous.
The next closest relatives of geckos are iguanians (Iguania), which include iguanas, chameleons, agamids, anoles, and other lizards with acrodont teeth. Iguanians are a group of lizards with diverse adaptations, such as herbivory, color change, and frills.
The most distant relatives of geckos within Squamata are snakes (Serpentes), which have lost their limbs and eyelids completely in adaptation to various habitats. Snakes are a group of reptiles with highly flexible jaws and venomous fangs in some species.
In conclusion, geckos are part of the suborder Gekkota within the order Squamata, which includes all lizards and snakes. Geckos are divided into six families that differ in their morphology, ecology, and behavior. Geckos are more closely related to some lizards than others within Squamata, based on molecular data. The closest relatives of geckos are pygopods and dibamids, followed by skinks, anguimorphs, iguanians, and snakes.