The Iguanidae is a family of lizards composed of the iguanas, chuckwallas, and their prehistoric relatives, including the widespread green iguana.
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.
Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed to form the sister group to the remainder of the Squamata, which comprise nearly 11,000 named species, roughly 2000 of which are iguanians. However, molecular information has placed Iguania well within the Squamata as sister taxa to the Anguimorpha and closely related to snakes. The order has been under debate and revisions after being classified by Charles Lewis Camp in 1923 due to difficulties finding adequate synapomorphic morphological characteristics. Most iguanians are arboreal but there are several terrestrial groups. They usually have primitive fleshy, non-prehensile tongues, although the tongue is highly modified in chameleons. Today they are scattered occurring in Madagascar, the Fiji and Friendly Islands and Western Hemisphere.
The Djadochta Formation is a highly fossiliferous geological formation situated in Central Asia, Gobi Desert, dating from the Late Cretaceous period, about 75 million to 71 million years ago. The type locality is the Bayn Dzak locality, famously known as the Flaming Cliffs. Reptile and mammal remains are among the fossils recovered from the formation.
Minotaurasaurus is a monospecific genus of ankylosaurid dinosaur that lived in Mongolia during the Late Cretaceous in what is now the Djadochta Formation. The type and only species, Minotaurasaurus ramachandrani, is known from two skulls, a cervical vertebra and a cervical half ring. It was named and described in 2009 by Clifford Miles and Clark Miles. The first fossils of Minotaurasaurus were illegally exported out of Mongolia.It has been suggested to be a synonym of Tarchia but more recent publications consider it as a distinct genus.
Dorsetisaurus is a genus of extinct lizard, known from the Late Jurassic of North America, and the Late Jurassic-earliest Cretaceous of Europe. The genus was first reported from the Early Cretaceous (Berriasian) Lulworth Formation of the Purbeck Group of Durlston Bay, in Dorset. It has also been reported from the Late Jurassic aged Alcobaça Formation of Portugal, the Aptian-Albian Dzunbain Formation of Mongolia, and the Morrison Formation of Western North America present in stratigraphic zones 2, 4, and 5. It is considered the oldest widely accepted member of Anguimorpha. based on the presence of 11 shared synapomorphies.
Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.
Aiolosaurus is an extinct genus of monitor lizard from the Late Cretaceous of Mongolia. The type and only species, Aiolosaurus oriens, was named in 2000 from Ukhaa Tolgod, a rich fossil site in the Campanian-age Djadochta Formation.
Gekkonomorpha is a clade of lizards that includes geckos and their closest relatives. Although it was first named in 1900, Gekkonomorpha was not widely used as a formal taxon until it was given a phylogenetic definition in the 1990s. Under this definition, Gekkonomorpha is a stem-based taxon containing the node-based taxon Gekkota, the group that includes the last common ancestor of all living geckos and its descendants. The extent of Gekkonomorpha beyond gekkotans differs between studies. For example, Lee (1998) defined Gekkonomorpha in such a way that it included not only Gekkota but the legless amphisbaenian and dibamid lizards as well. The phylogenetic analysis of Conrad (2008), which did not support a close relationship between geckos and legless lizards, used Gekkonomorpha in a much more restrictive sense so that it included only Gekkota and a few extinct lizards more closely related to Gekkota than to any other living group of lizards. Some of the most recent phylogenetic analyses suggest that the extinct lizards Gobekko and Parviraptor may be stem gekkotans, although other analyses find that Gobekko may instead be within Gekkota and Parviraptor outside Gekkonomorpha.
Myrmecodaptria is an extinct genus of scleroglossan lizard from the Late Cretaceous Djadokhta Formation in Ukhaa Tolgod, Mongolia. The type and only species, Myrmecodaptria microphagosa, was named in 2000 by paleontologists Gao Keqin and Mark Norell. Myrmecodaptria is known from a single holotype skull and lower jaws. It is distinguished from all other lizards by its extremely elongated skull. The eyes are placed close to the snout, which is short and rounded. The top of the skull is covered in bony knobs called osteoderms. The parietal bone at the back of the skull is elongated and about as long as the frontal bones, which are the usually the longest bones along the top of the skull in lizards. The squamosal bone at the back of the skull reaches forward to connect with the jugal bone behind the eye, forming a thin arch between the temporal fenestrae. Myrmecodaptria also has fewer and more widely spaced teeth in its jaws than do most other lizards.
Chamaeleontiformes is a hypothesized clade of iguanian lizards defined as all taxa sharing a more recent common ancestor with Chamaeleo chamaeleon than with Hoplocercus spinosus, Polychrus marmoratus, or Iguana iguana. It was named by paleontologist Jack Conrad in 2008 to describe a clade recovered in his phylogenetic analysis that included the extinct genus Isodontosaurus, the extinct family Priscagamidae, and the living clade Acrodonta, which includes agamids and chameleons. It is a stem-based taxon and one of two major clades within Iguania, the other being Pleurodonta. Below is a cladogram from Daza et al. (2012) showing this phylogeny:
Carusioidea is a clade of lizards that includes the family Xenosauridae from Central America and the extinct genus Carusia from the Late Cretaceous of Mongolia. It was named in 1998 after a sister-group relationship was found between Carusia and Xenosauridae. Phylogenetic analysis indicates that Carusioidea is the most basal clade within Anguimorpha. Features that help define Carusioidea include closely spaced orbits or eye sockets separated by fused frontal bones, a connection between the jugal and squamosal bones below the supratemporal arch, and a covering of bony osteoderms over the skull roof. Below is a cladogram showing the phylogenetic relationships of carusioids from Gao and Norell (1998):
Priscagamidae is an extinct family of iguanian lizards known from the Late Cretaceous of Mongolia and China and the Eocene of India, spanning a range from 83.6 to 48.6 million years ago. Probably the earliest priscagamids on indeterminate genera were found in Aptian-Albian sediments in "Hobur", Mongolia. It includes the genera Heterodontagama, Mimeosaurus, Phrynosomimus, Priscagama, and possibly Pleurodontagama. The first fossils of priscagamids were found in the Djadochta and Khermeen Tsav formations of Mongolia. More recently they have been found in the Cambay Formation in India, leading to the naming of Heterodontagama in 2013. Priscagamidae was originally described as a subfamily of Agamidae called Priscagaminae in 1984, but it was reclassified as a distinct family in 1989. Most phylogenetic analyses still find a close relationship between Priscagamidae and Agamidae, although a 2015 study found it to be basal to all other iguanian clades, warranting its removal from Iguania and placement in a larger clade called Iguanomorpha.
Saichangurvel is an extinct genus of iguanian lizards from the Late Cretaceous of Mongolia. It is a member of a clade called Gobiguania, an exclusively Late Cretaceous group of iguanian lizards that was likely endemic to the Gobi Desert. The type species, Saichangurvel davidsoni, was named by paleontologists Jack Conrad and Mark Norell of the American Museum of Natural History in 2007. It is known from a single nearly complete and fully articulated skeleton called IGM 3/858, which was found eroding from a block of sandstone during a thunderstorm at a fossil locality called Ukhaa Tolgod. IGM 3/858 comes from the Djadochta Formation, which is between 75 and 71 million years in age. Just as it is today, the Gobi was a desert during the Cretaceous. IGM 3/858 may have died in a collapsing sand dune, the rapid burial preserving its skeleton in pristine condition.
Priscagama is an extinct genus of iguanian lizard from the Late Cretaceous of Mongolia and China. It belongs to an extinct family of iguanians called Priscagamidae. Several incomplete skulls have been found in the Barun Goyot and Djadochta formations, and were originally referred to the genus Mimeosaurus; the type species Priscagama gobiensis was named in 1984 when it was recognized that these skulls belonged to a distinct species. Priscagama differs from most other priscagamids in having a more elongate, lightly built skull. It is very similar in appearance to another priscagamid called Pleurodontagama, as the two can only be distinguished by the shape of their teeth.
Anchaurosaurus is an extinct genus of iguanian lizard from the Late Cretaceous of Inner Mongolia, China. It belongs to an extinct clade of iguanians called Gobiguania that was endemic to the Gobi Desert during the Late Cretaceous. The type species, Anchaurosaurus gilmorei, was named in 1995 on the basis of a well-preserved skull and incomplete skeleton from the Djadochta Formation. Compared to other iguanians, Anchaurosaurus has a relatively elongated skull, large eye sockets, and higher tooth crowns. Phylogenetic analysis indicates that among gobiguanians, Anchaurosaurus is most closely related to Zapsosaurus from Mongolia. Below is a cladogram from Daza et al. (2012) showing the phylogenetic relationships of Anchaurosaurus:
Xihaina is an extinct genus of iguanian lizard from the Late Cretaceous of Inner Mongolia, China. The type species Xihaina aquilonia was named in 1995 from the Djadochta Formation and is known from a partial skeleton that preserves parts of the skull, most of the vertebral column, the pelvis, and the right hind limb. The incomplete nature of this specimen makes the classification of Xihaina difficult; it has never been incorporated into a phylogenetic analysis, but it shares similarities with a group of Late Cretaceous Mongolian lizards called Gobiguania, particularly the gobiguanian genera Anchaurosaurus and Polrussia. The fact that many skeletal elements are missing yet the rest of the skeleton is articulated suggests the individual may have been partially eaten by a predator or scavenger and then rapidly buried soon after.
Polrussia is an extinct genus of iguanian lizards dating to the Late Cretaceous epoch, found in what is now Mongolia. It belongs to a group of extinct iguanians called Gobiguania that was endemic to the Gobi Desert during the Late Cretaceous. The type species Polrussia mongoliensis was named in 1991 on the basis of a skull found in the Barun Goyot Formation. The genus name refers to the Polish and Russian paleontologists who worked together to find and describe the material. Polrussia has a short skull, slightly pointed and flattened snout, and large eye sockets. The teeth each have one cusp, as opposed to the multiple cusps seen in some other gobiguanians. The skull is only 1.2 centimetres (0.47 in) long, making Polrussia one of the smallest gobiguanians.
Igua is an extinct genus of iguanian lizards belonging to a group called Gobiguania that was endemic to the Gobi Desert during the Late Cretaceous. The type species Igua minuta was named in 1991 on the basis of a skull from the Barun Goyot Formation in Mongolia. The skull itself is very small, only 14 millimetres (0.55 in) long, and may have belonged to a juvenile given that it possesses a large fontanelle and that many of the bones are unfused. The snout-vent length of the individual is estimated to have been 55 to 65 millimetres. Igua differs from related gobiguanians like Polrussia in having a more rounded skull. It is similar in appearance to the living genera Liolaemus and Tropidurus. The teeth are tricuspid and pleurodont, meaning they are attached to inner surfaces of the jaws.
Magnuviator is a genus of extinct iguanomorph lizard from the Late Cretaceous of Montana, US. It contains one species, M. ovimonsensis, described in 2017 by DeMar et al. from two specimens that were discovered in the Egg Mountain nesting site. Magnuviator is closest related to the Asian Saichangurvel and Temujinia, which form the group Temujiniidae. Unlike other members of the Iguanomorpha, however, Magnuviator bears a distinct articulating notch on its tibia for the ankle bones, which has traditionally been considered a characteristic of non-iguanomorph lizards. The morphology of its teeth suggests that its diet would have mainly consisted of wasps, like the modern phyrnosomatid iguanians Callisaurus and Urosaurus, although it also shows some adaptations to herbivory.
