As for the nares themselves, they were generally large and oval-shaped, positioned high and close to the midline of the skull. Lepidosauromorpha is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). This was a rear-facing branch of bone that stretched up below and behind the external nares (nostril holes) to contact the nasal bones on the upper edge of the snout. An introduction to the phylogenetic taxonomy of Archosauromorpha Traditionally, Archosauria included crocodiles, birds, dinosaurs, pterosaurs, and a large number of related taxa classed as "thecodonts." Share. [7] David Dilkes (1998) formulated a more inclusive (and currently more popular) definition of Archosauromorpha, defining it as the clade containing Protorosaurus and all other saurians that are more closely related to Protorosaurus than to Lepidosauria. [16] In all adult archosauromorphs with the exception of Aenigmastropheus, the vertebrae lack notochordal canals, holes which perforate the centra. These were the Archosauriformes, a diverse assortment of animals including the famous dinosaurs and pterosaurs. Cladistic analyses created during the 1980s by Gauthier, Michael J. Benton, and Susan E. Evans implemented Gauthier's classification scheme within large studies of reptile relations. In conjunction with this shift, the olecranon process of the ulna is poorly developed in archosauromorphs apart from Aenigmastropheus and Protorosaurus. These include 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. A landmark 1998 study by David Dilkes completely deconstructed the concept of Prolacertiformes as a traditional monophyletic group (i.e. This bone is roughly L-shaped in these taxa, with a tall dorsal process (vertical branch), a short anterior process (forward branch), and a tiny or absent posterior process (rear branch). The only living sub-group is the Lepidosauria: extant lizards, snakes and tuataras. Protorosauria/Prolacertiformes has had a complicated history, and many taxa have entered and left the group as paleontologists discover and re-evaluate reptiles of the Triassic. Die Archosauromorpha sind eine Verwandtschaftsgruppe der diapsiden Reptilien, der die Archosaurier und verschiedene ausgestorbene Reptiliengruppen angehören, die enger mit den Archosauriern als mit den Lepidosauriern verwandt sind. In contrast, Archosauromorphs possess a parasagittal gait, a reduction in their dermal girdle, a reduction and/or loss of the sternum, and a more thecodont dentition. Trilophosaurids and azendohsaurids are now united under the group Allokotosauria ("strange reptiles"). Zu den Lepidosauromorpha gehören neben den Schuppenechsen (Lepidosauria) die Vertreter aus der vollständig ausgestorbenen Gruppe Sauropterygia, die den Großteil der mesozoischen Meeresreptilien stellen, sowie einige weitere Vertreter aus dem Mesozoikum. Turtles and tortoises are closer to archosaurs than to any other living thing. [citation needed]. [6][2] The chameleon- or tamandua-like drepanosaurs are also semi-regularly placed within Archosauromorpha,[8] although some studies have considered them to be part of a much more basal lineage of reptiles. [7][3], The humerus (forearm bone) is solid in archosauromorphs, completely lacking a hole near the elbow known as the entepicondylar foramen. [10] The aquatic thalattosaurs[6] and gliding kuehneosaurids[6][10] are also irregularly considered archosauromorphs. [6], In conjunction with their long, S-shaped necks, early archosauromorphs had several adaptations of the cervical (neck) vertebrae, and usually the first few dorsal (back) vertebrae as well. In many advanced archosauromorphs, the capitullum and trochlea (elbow joints) of the humerus are poorly developed. [2], The cladogram shown below follows the most likely result found by an analysis of turtle relationships using both fossil and genetic evidence by M.S. When archosauromorphs first appeared in the fossil record in the Permian, they were represented by long-necked, lightly-built sprawling reptiles with moderately long, tapering snouts. [6] In archosauriforms, the jugal even re-encloses the lower temporal fenestra.
2020 lepidosauromorpha vs archosauromorpha