Archosauromorpha
Encyclopedia
Archosauromorpha is an infraclass of diapsid
reptile
s that first appeared during the late Permian
and became more common during the Triassic
. Included in this infraclass are the groups Rhynchosaur
ia, Trilophosaur
idae, Prolacertiformes
, Archosauriformes
, and, tentatively, Choristodera
. While superficially these reptiles vary in appearance (at one time they were even included in different subclasses – the trilophosaurs were considered euryapsids, and the rhynchosaurs were considered lepidosaurs and were included in the same order as the tuatara
), they are actually united by a number of small skeletal and skull-related details that suggest they form a clade
that descended from a single common ancestor.
Of the five taxa mentioned above the first three died out at or before the end-Triassic extinction
. The choristoderans continued as a minor group until the Miocene
, and the Archosauriformes were important factors in early Triassic environments before giving rise to the even more successful Archosaur
ia.
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...
reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s that first appeared during the late Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
and became more common during the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. Included in this infraclass are the groups Rhynchosaur
Rhynchosaur
Rhynchosaurs were a group of Triassic diapsid reptiles related to the archosaurs.-Description:Rhynchosaurs were herbivores, and at times abundant , with stocky bodies and a powerful beak...
ia, Trilophosaur
Trilophosaur
Trilophosaurs were lizard-like Triassic diapsid reptiles related to the archosaurs. The best known genus is Trilophosaurus, a herbivore up to 2.5 meters long. It had a short, unusually heavily-built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting...
idae, Prolacertiformes
Prolacertiformes
Prolacertiformes were an order of archosauromorph reptiles that lived during the Permian and Triassic Periods...
, Archosauriformes
Archosauriformes
Archosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian...
, and, tentatively, Choristodera
Choristodera
Choristodera is an order of semi-aquatic diapsid reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to at least the early Miocene. Choristoderes have been found in North America, Asia, and Europe. The most common fossils are typically found from the Late Cretaceous to the...
. While superficially these reptiles vary in appearance (at one time they were even included in different subclasses – the trilophosaurs were considered euryapsids, and the rhynchosaurs were considered lepidosaurs and were included in the same order as the tuatara
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
), they are actually united by a number of small skeletal and skull-related details that suggest they form a clade
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
that descended from a single common ancestor.
Of the five taxa mentioned above the first three died out at or before the end-Triassic extinction
Triassic-Jurassic extinction event
The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, , and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas a whole class and twenty percent of all marine families...
. The choristoderans continued as a minor group until the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
, and the Archosauriformes were important factors in early Triassic environments before giving rise to the even more successful Archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
ia.
Classification
- Subclass DiapsidDiapsidDiapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...
a- Infraclass ARCHOSAUROMORPHA
- Family EuparkeriidaeEuparkeriidaeEuparkeriidae is a family of small basal archosauromorph carnivores which lived from the Early Triassic to the Middle Triassic . Their fossil remains are known so far from South Africa and Russia...
- Family ErythrosuchidaeErythrosuchidaeErythrosuchidae are a family of large basal archosauromorph carnivores that lived from the later Early Triassic to the early Middle Triassic . Their fossil remains are known so far from South Africa , the Perm region of Russia, and China...
- Family ProterochampsidaeProterochampsidaeProterochampsidae is a family of archosauriforms. Proterochampsids may have filled an ecological niche similar to modern crocodiles, and had a general crocodile-like appearance. They lived in what is now South America in the Middle and Late Triassic....
- Family ProterosuchidaeProterosuchidaeProterosuchidae is an early, possibly paraphyletic, assemblage of basal archosauriformes whose fossils are known from the Latest Permian of Russia and the Early Triassic of southern Africa, Russia, China, Australia, and Antarctica...
- ?Order ChoristoderaChoristoderaChoristodera is an order of semi-aquatic diapsid reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to at least the early Miocene. Choristoderes have been found in North America, Asia, and Europe. The most common fossils are typically found from the Late Cretaceous to the...
- Order ProlacertiformesProlacertiformesProlacertiformes were an order of archosauromorph reptiles that lived during the Permian and Triassic Periods...
- Order RhynchosaurRhynchosaurRhynchosaurs were a group of Triassic diapsid reptiles related to the archosaurs.-Description:Rhynchosaurs were herbivores, and at times abundant , with stocky bodies and a powerful beak...
ia - Order TrilophosaurTrilophosaurTrilophosaurs were lizard-like Triassic diapsid reptiles related to the archosaurs. The best known genus is Trilophosaurus, a herbivore up to 2.5 meters long. It had a short, unusually heavily-built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting...
ia - Division ArchosaurArchosaurArchosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
ia- Subdivision CrurotarsiCrurotarsiThe Crurotarsi are a group of archosauriformes, represented today by the crocodiles,...
- Family OrnithosuchidaeOrnithosuchidaeOrnithosuchidae is an extinct family of reptiles from the Triassic period that were distantly related to crocodilians. They are classified as crurotarsan archosaurs. Ornithosuchids were quadrupedal and facultatively bipedal, meaning they had the ability to walk on two legs for short periods of time...
- Order AetosaurAetosaurAetosaurs are an extinct order of heavily armoured, medium- to large-sized Late Triassic herbivorous archosaurs. They have small heads, upturned snouts, erect limbs, and a body covered by plate-like scutes. All aetosaurs belong to the family Stagonolepididae...
ia - Order PhytosaurPhytosaurPhytosaurs are an extinct group of large semi-aquatic Late Triassic archosaurs. Phytosaurs belong to the family Phytosauridae and the order Phytosauria. They were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodiles in size, appearance, and lifestyle, an example...
ia - Order RauisuchiaRauisuchiaRauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
- Superorder CrocodylomorphaCrocodylomorphaThe Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
- Order CrocodiliaCrocodiliaCrocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
- Order Crocodilia
- Family Ornithosuchidae
- Subdivision AvemetatarsaliaAvemetatarsaliaAvemetatarsalia is a clade name established by British palaeontologist Michael Benton in 1999 for all crown group archosaurs that are closer to birds than to crocodiles. It includes a similarly defined subgroup, Ornithodira...
- ScleromochlusScleromochlusScleromochlus is an extinct genus of small avemetatarsalian from the Late Triassic period. A lightly built cursorial animal, its phylogenetic position has been debated; as different analyses have found it to be either the basal-most ornithodiran, the sister-taxon to Pterosauria, or a basal member...
- Division Ornithodira
- Order PterosaurPterosaurPterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
ia - Superorder DinosaurDinosaurDinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
ia- Order OrnithischiaOrnithischiaOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
- Order SaurischiaSaurischiaSaurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
- Order Ornithischia
- Order Pterosaur
- Scleromochlus
- Subdivision Crurotarsi
- Family Euparkeriidae
- Infraclass ARCHOSAUROMORPHA
Phylogeny
External links
- Palaeos
- Paleofiles – lists taxa