Allokotosauria is a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of early archosauromorph

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s from the

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ...

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 a ...

known from

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. Allokotosauria was first described and named when a new

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

grouping of specialized herbivorous archosauromorphs was recovered by Sterling J. Nesbitt, John J. Flynn, Adam C. Pritchard, J. Michael Parrish, Lovasoa Ranivoharimanana and André R. Wyss in

2015 2015 was designated by the United Nations as: * International Year of Light * International Year of Soil __TOC__ Events January * January 1 – Lithuania officially adopts the euro as its currency, replacing the litas, and becomes ...

. The name Allokotosauria is derived from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

meaning "strange reptiles" in reference to unexpected grouping of early archosauromorph with a high disparity of features typically associated with

herbivory A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

History

Nesbitt ''et al.'' (2015) defined the group as a

stem-based taxon Phylogenetic nomenclature is a method of nomenclature for taxon, taxa in biology that uses phylogenetics, phylogenetic definitions for taxon names as explained below. This contrasts with Biological classification, the traditional method, by which ...

containing '' Azendohsaurus madagaskarensis'' and '' Trilophosaurus buettneri'' and all taxa more closely related to them than to ''

Tanystropheus longobardicus ''Tanystropheus'' (~ 'long' + 'hinged') is an extinct genus of archosauromorph reptile which lived during the Triassic period, Triassic Period in Europe, Asia, and North America. It is recognisable by its extremely elongated neck, longer than t ...

'', '' Proterosuchus fergusi'', ''

Protorosaurus speneri ''Protorosaurus'' (from , 'earlier' and , 'lizard') is an extinct genus of reptile. Members of the genus lived during the late Permian period in what is now Germany and Great Britain. Once believed to have been an ancestor to lizards, ''Protoro ...

'' or '' Rhynchosaurus articeps''. Therefore, Allokotosauria includes the families Azendohsauridae and

Trilophosauridae Trilophosaurs are lizard-like Triassic allokotosaur reptiles related to the archosaurs. The best known genus is '' Trilophosaurus'', a herbivore up to long. It had a short, unusually heavily built skull, equipped with massive, broad flattened ...

by definition, as well as the potentially more basal '' Pamelaria'' which is closer to them than to other early archosauromorphs. ''Pamelaria'' is the earliest known allokotosaur, dating to the

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

. In 2015, azendohsauridae was represented by a single genus '' Azendohsaurus'' known from the

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

, while trilophosaurids are mostly known from the

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

stages of

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

and potentially

European Russia European Russia is the western and most populated part of the Russia, Russian Federation. It is geographically situated in Europe, as opposed to the country's sparsely populated and vastly larger eastern part, Siberia, which is situated in Asia ...

, though one member of the latter group, '' Variodens inopinatus'', is known from

Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...

. Since then, new discoveries have led to an expansion in generic diversity in azendohsaurids, including such taxa as '' Shringasaurus'' from

India, and '' Puercosuchus'' from

North America, both of which also expand the clade's biogeographical and biostratigraphic range. According to studies of '' Arctosaurus'' material from Cameron Island in Canada, the latter may have been an allokotosaurian because of the similarities with '' Azendohsaurus'' due to the presence of a posterior ridge from the centrum to the diapophyses which extends from the diapophysis all the way to the posterior ventrolateral corner of the centrum. This ridge overhangs a deep groove in the lateral surface of the centrum.

Description and phylogeny

Allokotosauria is most notably characterized by wrinkled side surface of orbital border of the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

, expanded and hooked

quadrate bone The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids ( reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms up ...

head on the posterior side, and a prominent tubercle developed above to the glenoid fossa of the

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

, although there are other unambiguous traits that differentiate it from other early archosauromorphs. Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

showing the phylogenetic relationships of Allokotosauria within

Archosauromorpha 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) than to lepidosaurs (such as tuataras, lizards, ...

as recovered by Nesbitt ''et al.'' (2015). Ezcurra (2016) also recovered a highly supported Allokotosauria with the same topology (including only '' Pamelaria'', '' Azendohsaurus madagaskarensis'' and '' Trilophosaurus buettneri'' in his analysis), but noted that ''Pamelaria'' is nearly as likely to represent a basal azendohsaurid instead. Sengupta ''et al.'' (2017) described a new azendohsaurid and recovered ''Pamelaria'' as an azendohsaurid. Pritchard and Nesbitt (2017) found support for the inclusion of

Kuehneosauridae Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America. Description and systematics They are distinguished from other diapsids by their 'wings' formed by elongated ...

within Allokotosauria. Buffa ''et al.'' (2024) recovered

Drepanosauromorpha Drepanosaurs (members of the clade Drepanosauromorpha) are a group of extinct reptiles that lived between the Carnian and Rhaetian stages of the late Triassic Period, approximately between 230 and 210 million years ago. The various species of dre ...

as allokotosaurian archosauromorphs, specifically as the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of trilophosaurids.

References

{{Taxonbar, from=Q25095775 Archosauromorpha Triassic reptiles Triassic reptiles of Africa Triassic reptiles of Asia Triassic reptiles of Europe Triassic reptiles of North America Anisian first appearances Rhaetian extinctions Taxa named by Sterling Nesbitt