Squamata is the largest order of reptiles, comprising lizards and snakes. With over 12162 Species, it is also the second-largest order of extant (living) vertebrates, after the perciform fish. Squamates are distinguished by their skins, which bear horny scales or shields, and must periodically engage in molting. They also possess movable quadrate bones, making possible movement of the upper jaw relative to the neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamates are the most variably sized living reptiles, ranging from the 16 mm (0.63 in) dwarf gecko to the 6.5 m (21 ft) reticulated python. The now-extinct mosasaurs reached lengths over 14 m (46 ft).
Dibamidae or blind skinks is a family of lizards characterized by their elongated cylindrical body and an apparent lack of limbs. Female dibamids are entirely limbless and the males retain small flap-like hind limbs, which they use to grip their partner during mating. They have a rigidly fused skull, lack pterygoid teeth and external ears. Their eyes are greatly reduced, and covered with a scale.
The Varanidae are a family of lizards in the superfamily Varanoidea and order Anguimorpha. The family, a group of carnivorous and frugivorous lizards, includes the living genus Varanus and a number of extinct genera more closely related to Varanus than to the earless monitor lizard (Lanthanotus). Varanus includes the Komodo dragon, crocodile monitor, savannah monitor, the goannas of Australia and Southeast Asia, and various other species with a similarly distinctive appearance. Their closest living relatives are the earless monitor lizard and Chinese crocodile lizard. The oldest members of the family are known from the Late Cretaceous of Mongolia.
Ophidia is a group of squamate reptiles including modern snakes and reptiles more closely related to snakes than to other living groups of lizards.
Several groups of tetrapods have undergone secondary aquatic adaptation, an evolutionary transition from being purely terrestrial to living at least part of the time in water. These animals are called "secondarily aquatic" because although their ancestors lived on land for hundreds of millions of years, they all originally descended from aquatic animals. These ancestral tetrapods had never left the water, and were thus primarily aquatic, like modern fishes. Secondary aquatic adaptations tend to develop in early speciation as the animal ventures into water in order to find available food. As successive generations spend more time in the water, natural selection causes the acquisition of more adaptations. Animals of later generations may spend most their life in the water, coming ashore for mating. Finally, fully adapted animals may take to mating and birthing in water or ice.
Mosasaurus is the type genus of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The genus was one of the first Mesozoic marine reptiles known to science—the first fossils of Mosasaurus were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 18th century, and were initially thought to be crocodiles or whales. One skull discovered around 1780 was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any known living animal. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. Cuvier did not designate a scientific name for the animal; this was done by William Daniel Conybeare in 1822 when he named it Mosasaurus in reference to its origin in fossil deposits near the Meuse River. The exact affinities of Mosasaurus as a squamate remain controversial, and scientists continue to debate whether its closest living relatives are monitor lizards or snakes.
Toxicofera is a proposed clade of scaled reptiles (squamates) that includes the Serpentes (snakes), Anguimorpha and Iguania. Toxicofera contains about 4,600 species, of extant Squamata. It encompasses all venomous reptile species, as well as numerous related non-venomous species. There is little morphological evidence to support this grouping; however, it has been recovered by all molecular analyses as of 2012.
The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except for South America.
Pythonomorpha was originally proposed by paleontologist Edward Drinker Cope (1869) as a reptilian order comprising mosasaurs, which he believed to be close relatives of Ophidia (snakes). The etymology of the term Pythonomorpha comes from the Greek Python and morphe ("form"), and refers to the generally serpentine body plan of members of the group. Cope wrote, "In the mosasauroids, we almost realize the fictions of snake-like dragons and sea-serpents, in which men have been ever prone to indulge. On account of the ophidian part of their affinities, I have called this order Pythonomorpha." Cope incorporated two families, the Clidastidae and the Mosasauridae.
Aigialosauridae is a family of Late Cretaceous semiaquatic pythonomorph lizards closely related to the mosasaurs. Regarded by some paleontologists as a distinct monophyletic group and by others as an adaptive grade within the basal mosasauroids, recent molecular and morphological data suggests that they are the oldest known members of the lineage leading to the mosasaurs.
The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to Varanus and Anguis than Scincus. These lizards, along with iguanians and snakes, constitute the proposed "venom clade" Toxicofera of all venomous reptiles.
Taniwhasaurus is an extinct genus of mosasaurs that lived during the Campanian stage of the Late Cretaceous. It is a member of the subfamily Tylosaurinae, a lineage of mosasaurs characterized by a long toothless conical rostrum. Two valid species are attached to the genus, T. oweni and T. antarcticus, known respectively from the fossil record of present-day New Zealand and Antarctica. Two other species have been nominally classified within the genus, T. 'capensis' and T. 'mikasaensis', recorded in present-day South Africa and Japan, but their attribution remains problematic due to the fragmentary state of their fossils. The generic name literally means "taniwha lizard", referring to a supernatural aquatic creature from Māori mythology.
Sineoamphisbaena is an extinct genus of squamate of uncertain phylogenetic placement. Its fossils have been found in Late Cretaceous deposits in Inner Mongolia, China. It contains a single species, Sineoamphisbaenia hexatabularis.
Mosasauroidea is a superfamily of extinct marine lizards that existed during the Late Cretaceous. Basal members of this group consist of small semiaquatic forms with terrestrial limbs ("plesiopedal"), while laters members include larger fully aquatic paddle-limbed ("hydropedal") forms commonly known as mosasaurs. These were traditionally grouped within their own separate families, the Aigialosauridae and Mosasauridae respectively. However, phylogenetic studies have since found plesiopedal mosasauroids to be a non-monophyletic group, with some taxa nestled within the mosasaurids.
Platynota is a polyphyletic group of anguimorph lizards and thus belongs to the order Squamata of the class Reptilia. Since it was named in 1839, it has included several groups, including monitor lizards, snakes, mosasaurs, and helodermatids. Its taxonomic use still varies, as it is sometimes considered equivalent to the group Varanoidea and other times viewed as a distinct group. It is phylogenetically defined as a clade containing Varanidae. It also includes many extinct species.
Aigialosaurus is an extinct genus of Late Cretaceous marine or semiaquatic lizard classified as part of the family Aigialosauridae within the Mosasauroidea. Exclusively found in deposits of Cenomanian age near Hvar, Croatia, the genus contains one valid species, A. dalmaticus. According to recent molecular and morphological data, Aigialosaurus is the oldest known member of the lineage leading to large Cretaceous marine reptiles called mosasaurs, a group most closely related to snakes among living squamates. It was a relatively small reptile with a complete specimen measuring 65 cm (2.13 ft) long.
Monstersauria is a clade of anguimorph lizards, defined as all taxa more closely related to Heloderma than Varanus. It includes Heloderma, as well as several extinct genera, such as Estesia, Primaderma and Gobiderma, but this group was found to be polyphyletic in the most recent and complete squamate phylogenetic analysis by Reeder et al. (2015).
Reptiles arose about 320 million years ago during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds that are descended from early traditionally-defined reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.
Dolichosauridae is a family of Cretaceous aquatic lizards. They are widely considered to be the earliest and most primitive members of Mosasauria, though some researchers have recovered them as more closely related to snakes.
Ophidiomorpha is a proposed clade composed of snakes and a number of extinct squamate groups. The clade was defined by Placi and Caldwell in 2007 as a node-based clade containing the most recent common ancestor of dolichosaurs, adriosaurs, Aphanizocnemus, and fossil and extant Ophidia and all of its descendants.
