Myrmecodaptria

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Myrmecodaptria
Temporal range: Late Cretaceous
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Bainguidae
Genus: Myrmecodaptria
Gao and Norell, 2000
Type species
Myrmecodaptria microphagosa
Gao and Norell, 2000

Myrmecodaptria (meaning "ant eater" in Greek) is an extinct genus of scleroglossan lizard from the Late Cretaceous Djadokhta Formation in Ukhaa Tolgod, Mongolia. The type and only species, Myrmecodaptria microphagosa (microphagosa meaning "eating little" in Greek), 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. [1]

When Myrmecodaptria was first described in 2000 it was thought to be a member of Gekkota, the group that includes living geckos and pygopodids (legless lizards). Characteristics that Myrmecodaptria shares in common with gekkotans include fused frontal bones that form a tube within the skull and the absence of a postorbital bone. However, Myrmecodaptria has many features that are not found in gekkotans, such as the presence of a small hole at the top of the skull called the parietal foramen, a thick jugal bone forming a complete postorbital bar behind the eye socket, and a complete upper temporal arch closing off a pair of holes at the top of the skull called the supratemporal fenestrae. [1] The first study to include Myrmecodaptria in a phylogenetic analysis was published in 2006, and it did not find support for Myrmecodaptria being a gekkotan. Instead, Myrmecodaptria was found to be more closely related to a group of lizards called Autarchoglossa, a large clade or evolutionary grouping that includes skinks, anguimorphs, and snakes. The supposedly gekkotan features seen in Myrmecodaptria may instead be characteristic of the earliest members of Scleroglossa, which split into gekkotans and autarchoglossans. Myrmecodaptria is part of the scleroglossan lineage leading to autarchoglossans, making it a "stem" autarchoglossan. [2] Myrmecodaptria was again included in a phylogenetic analysis authored by Jack Conrad in 2008, which placed it in an extinct group called Bainguidae. Bainguidae was positioned at the stem of Autarchoglossa in the analysis (within a larger clade called Evansauria), but this relationship had only weak support. The best known member of Banguidae, Bainguis , may instead be a closer relative of living anguids or lacertoids, in which case Bainguidae would not be a valid grouping. [3]

A large phylogenetic analysis published in 2012, which resulted a very different hypothesis for the evolutionary relationships of lizards than those of previous analyses, found Myrmecodaptria to be closely related to the genus Carusia , which is also from the Late Cretaceous of Mongolia. In Conrad's 2008 analysis, Carusia was deeply nested within Autarchoglossa as a close relative of the living genus Xenosaurus . The 2012 analysis instead found that Myrmecodaptria and Carusia were close relatives of the family Scincidae, which includes modern skinks. Both genera were placed in a family called Carusiidae. While a close relationship to scincids was only weakly supported, the grouping of Myrmecodaptria and Carusia as sister taxa was strongly supported by nine shared characteristics, including fused frontals (which, according to the analysis, evolved independently in gekkotans and Carusiidae). [4]

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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.

Phrynosomimus is an extinct genus of iguanian lizard from the Late Cretaceous of Mongolia belonging to the extinct family Priscagamidae. The type species Phrynosomimus asper was named in 1996. Fossils have been found in the Barun Goyot and Djadochta formations and include several complete skulls. Phrynosomimus has a short, triangular skull with bony spikes projecting from the back, stemming from the squamosal and parietal bones. These spikes give it a similar appearance to the modern horned lizard Phrynosoma and inspire its name, which means "Phrynosoma mimic". Like other priscagamids it has an acrodont dentition, meaning that its teeth grow from the margins of the jaws rather than their inner surfaces, as is the case for the pleurodont dentitions of most lizards.

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Eichstaettisaurus is a genus of lizards from the Late Jurassic and Early Cretaceous of Germany, Spain, and Italy. With a flattened head, forward-oriented and partially symmetrical feet, and tall claws, Eichstaettisaurus bore many adaptations to a climbing lifestyle approaching those of geckoes. The type species, E. schroederi, is among the oldest and most complete members of the Squamata, being known by one specimen originating from the Tithonian-aged Solnhofen Limestone of Germany. A second species, E. gouldi, was described from another skeleton found in the Matese Mountains of Italy. Despite being very similar to E. schroederi, it lived much later, during the Albian stage. Fossils of both species show exceptional preservation due to deposition in low-oxygen marine environments.

<i>Almas ukhaa</i> Genus of reptiles (fossil)

Almas is a genus of troodontid theropod dinosaur from the Late Cretaceous of Mongolia. It contains a single species, Almas ukhaa, named in 2017 by Pei Rui and colleagues, based on a partial articulated skeleton. The only known specimen was found in the Djadochta Formation, which is late Campanian in age.

References

  1. 1 2 Keqin, G. A. O.; Norell, M. A. (2000). "Taxonomic Composition and Systematics of Late Cretaceous Lizard Assemblages from Ukhaa Tolgod and Adjacent Localities, Mongolian Gobi Desert". Bulletin of the American Museum of Natural History. 249: 1–118. doi:10.1206/0003-0090(2000)249<0001:TCASOL>2.0.CO;2. hdl:2246/1596.
  2. Conrad, J. L.; Norell, M. A. (2006). "High-resolution X-ray computed tomography of an Early Cretaceous gekkonomorph (Squamata) from Öösh (Övörkhangai; Mongolia)". Historical Biology. 18 (4): 405. doi:10.1080/08912960600679570.
  3. Conrad, J. L. (2008). "Phylogeny and Systematics of Squamata (Reptilia) Based on Morphology" (PDF). Bulletin of the American Museum of Natural History. 310: 1–182. doi:10.1206/310.1. hdl:2246/5915.
  4. Gauthier, J. A.; Kearney, M.; Maisano, J. A.; Rieppel, O.; Behlke, A. D. B. (2012). "Assembling the Squamate Tree of Life: Perspectives from the Phenotype and the Fossil Record". Bulletin of the Peabody Museum of Natural History. 53: 3–308. doi:10.3374/014.053.0101.