''Ankylosuchus'' is an extinct

doswelliid Doswelliidae is an extinct family of carnivorous archosauriform reptiles that lived in North America and Europe during the Middle to Late Triassic period. Long represented solely by the heavily-armored reptile ''Doswellia'', the family's composit ...

archosauromorph Archosauromorpha (Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, liza ...

reptile from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

of Texas. ''Ankylosuchus'' is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''Ankylosuchus chinlegroupensis''. It was named in 2013 on the basis of a fossil specimen including fragments of four vertebrae, parts of the skull, and part of a limb bone. These remains come from the

Colorado City Formation The Colorado City Formation is a geologic formation in Texas, United States. It preserves fossils dating back to the Triassic period. Biochronological significance The Otis Chalk localities that are situated in the Colorado City Formation form ...

, which dates to the early

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...

age of the Late Triassic. ''A. chinlegroupensis'' is named after the

Chinle Group The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In Ne ...

, a

stratigraphic group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into superg ...

that many Late Triassic formations of the southwestern United States have often been placed under, although a recent revision in stratigraphic nomenclature favors it being called the

Dockum Group The Dockum is a Late Triassic (approximately late Carnian through Rhaetian, or 223–200 Ma) geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Color ...

, which would make the species name a misnomer. ''Ankylosuchus'' is similar to other doswelliids in having heavy armor consisting of thick bony plates called

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s that interlock tightly and are irregularly pitted. It differs from other doswelliids in that the pits on the osteoderms are deeper and some osteoderms are fused to those that lie laterally to them.

References

Proterochampsians Prehistoric reptile genera Late Triassic reptiles of North America {{triassic-reptile-stub