Archosauromorpha
Clade of reptiles more closely related to archosaurs than to lepidosaurs.
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 lepidosaurs (such as tuataras, lizards, and snakes). Archosauromorphs first appeared during the late Middle Permian or Late Permian, though they became much more common and diverse during the Triassic period.
- first_appeared
- late Middle Permian or Late Permian
- peak_diversity
- Triassic period
- modern_definition_established
- 1980s
- key_groups
- Allokotosaurs, rhynchosaurs, Archosauriformes, long-necked reptiles (e.g., Protorosaurus, tanystropheids, Prolacerta)
- surviving_members
- crocodilians and birds
Lore & Background
However, little consensus on ancient reptile relationships existed prior to the late 20th century, so the term was seldom used until many years later. The advent of cladistics helped clarify a split between the archosaur and lepidosaur lineages within the Permian.
Reader's Guide
Archosauromorpha is one of the most diverse groups of reptiles, united by several shared skeletal characteristics including laminae on the vertebrae, a posterodorsal process of the premaxilla, a lack of notochordal canals, and the loss of the entepicondylar foramen of the humerus. Its unambiguous members include rhynchosaurs (stocky herbivores), allokotosaurs (including Trilophosaurus and Azendohsauridae), Archosauriformes (including dinosaurs, pterosaurs, crocodilians, and birds), and a polyphyletic grouping of long-necked reptiles such as Protorosaurus and tanystropheids. Disputed members include Choristodera, drepanosaurs, thalattosaurs, kuehneosaurids, and pantestudines (turtles and their extinct relatives). Genetic studies have placed turtles within Archosauromorpha as part of the clade Archelosauria, though anatomical data disagrees. The group's significance lies in its survival and diversification beyond the Triassic-Jurassic extinction, with crocodilians and birds as living representatives.
Did You Know?
- Archosauromorpha means 'ruling lizard forms' in Greek.
- Archosauromorphs first appeared during the late Middle Permian or Late Permian.
- Some authors place turtles and their extinct relatives (Pantestudines) within Archosauromorpha.
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