Allokotosauria is a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

of early archosauromorph

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

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 (d ...

to Late Triassic known from Asia, Africa,

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and Europe. Allokotosauria was first described and named when a new

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

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 File:2015 Events Collage new.png, From top left, clockwise: Civil service in remembrance of November 2015 Paris attacks; Germanwings Flight 9525 was purposely crashed into the French Alps; the rubble of residences in Kathmandu following the Apri ...

. The name Allokotosauria is derived from Greek meaning "strange reptiles" in reference to unexpected grouping of early archosauromorph with a high disparity of features typically associated with herbivory.

History

Nesbitt ''et al.'' (2015) defined the group as a stem-based taxon containing ''

Azendohsaurus madagaskarensis ''Azendohsaurus'' is an extinct genus of herbivorous archosauromorph reptile from roughly the late Middle to early Late Triassic Period of Morocco and Madagascar. The type species, ''Azendohsaurus laaroussii'', was described and named by Jean- ...

'' and ''

Trilophosaurus buettneri ''Trilophosaurus'' (Greek language, Greek for "lizard with three ridges") is a lizard-like trilophosaurid allokotosaur known from the Late Triassic of North America. It was a herbivore up to 2.5 m long. It had a short, unusually heavily built sku ...

'' and all taxa more closely related to them than to '' Tanystropheus longobardicus'', ''

Proterosuchus fergusi ''Proterosuchus'' is an extinct genus of archosauriform reptiles that lived during the Early Triassic. It contains three valid species: the type species ''P. fergusi'' and the referred species ''P. alexanderi'' and ''P. goweri''. All three sp ...

'', '' Protorosaurus speneri'' 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 che ...

by definition, as well as the potentially more

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

Pamelaria ''Pamelaria'' is an extinct genus of allokotosaurian archosauromorph reptile known from a single species, ''Pamelaria dolichotrachela'', from the Middle Triassic of India. ''Pamelaria'' has sprawling legs, a long neck, and a pointed skull with no ...

'' which is closer to them than to other early archosauromorphs. ''Pamelaria'' is the earliest known allokotosaur, dating to the Anisian of India. Azendohsauridae is currently represented by a single genus '' Azendohsaurus'' known from the Ladinian to Carnian of Africa, while trilophosaurids are mostly known from the Carnian to

Norian The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic defi ...

stages of

, England and potentially

European Russia European Russia (russian: Европейская Россия, russian: европейская часть России, label=none) is the western and most populated part of Russia. It is geographically situated in Europe, as opposed to the cou ...

, though one member of the latter group, ''

Variodens ''Variodens'' is an extinct genus of trilophosaur. Fossils have been found from the Emborough Quarries in the Mendip Hills of Somerset, England. These fossils have been uncovered from a Late Triassic fissure fill within Carboniferous-age limeston ...

inopinatus'', is known from

Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age ...

. 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, expanded and hooked quadrate bone head on the posterior side, and a prominent tubercle developed above to the glenoid

fossa Fossa may refer to: Animals * Fossa (animal), the common name of a carnivoran mammal of genus ''Cryptoprocta'' endemic to Madagascar * ''Fossa'', the Latin genus name of the Malagasy civet, a related but smaller mammal endemic to Madagascar Pla ...

of the scapula, although there are other unambiguous traits that differentiate it from other early archosauromorphs. Below is a cladogram 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) rather than lepidosaurs (such as tuataras, liza ...

as recovered by Nesbitt ''et al.'' (2015). Ezcurra (2016) also recovered a highly supported Allokotosauria with the same topology (including only ''

'', ''

'' and ''

'' 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 within Allokotosauria.

References

{{Taxonbar, from=Q25095775 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