Crurotarsi ("cross-ankles") is a node-based taxon created by Paul Sereno in 1991 to supplant the old term Pseudosuchia. As the basal phylogeny of this clade is not really understood, a stem-based definition is now preferred: all forms closer to Crocodiles than to Birds. As such, the Crurotarsi are the opposite branch to the Ornithodira (all forms closer to Birds than Crocodiles). In terms of the old Linnean taxonomy they correspond more or less to the Orders Thecodonta (minus the Proterosuchia) and Crocodilia Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (rhombozoans) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Typical Classes Subphylum Urochordata - Tunicatas Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Classes Synapsida Sauropsida Amphibia A tetrapod (Greek tetrapoda, four-legged) is a vertebrate animal having four feet, legs or leglike appendages. ... Orders See text. ... Groups See Text Diapsids (two arches) are a group of tetrapod animals that developed two holes (temporal fenestra) in each side of their skulls, about 300 million years ago during the late Carboniferous period. ... Groups Archosaurus Chasmatosaurus Euparkeria Crurotarsi     Aetosauria     Crocodilia (crocodiles)     Phytosauria     Rauisuchia Ornithodira     Pterosauria     Marasuchus     Dinosauria        Aves (birds) Archosaurs (Greek for ruling reptiles) are a group of diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian (Lower Triassic). ... Phytosaurs - family Phytosauridae or Parasuchidae - were a group of large (2 to 12 meters long - average size 3 to 4 meters) semi-aquatic predatory thecodonts that flourished during the Late Triassic period. ... Genera Aetosaurus Coahomasuchus Desmatosuchus Longosuchus Neoaetosauroides Paratypothorax Redondasuchus Stagonolepis Typothorax The Aetosaurs (family Stagonolepididae or Aetosauridae) are an extinct clade of heavily armoured, medium to large sized, Late Triassic herbivorous archosaurs. ... Genera Bomsgroveia Poposaurus Postosuchus Sillosuchus Shuvosaurus Teratosaurus The Poposauridae are a family of large (around 2. ... This article needs to be cleaned up to conform to a higher standard of quality. ... This cladogram shows the relationship among various insect groups. ... Paul C. Sereno (born October 11, 1967) is an American paleontologist who is the discoverer of several new dinosaur species on several continents. ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... A clade is group of organisms which share a common ancestor and which includes all decendents of that ancestor. ... In palaeontology, a stem group is a systematic grouping that is required to accommodate fossils in the classification of organisms. ... Genera Crocodylus Osteolaemus Tomistoma See full taxonomy. ... For other meanings of bird, see bird (disambiguation). ... Superorders Dinosauromorpha    Lagosuchians    Dinosauria Pterosauromorpha    Pterosauria    Scleromochlus    Sharovipteryx Ornithodira is a division of the Archosauromorpha (and perhaps Archosauria) clade. ... Linnaean taxonomy classifies living things into a hierarchy, originally starting with kingdoms. ... Thecodont (socket-toothed reptile), is a catch-all (paraphyletic) group, now considered an obsolete term, that was formerly used to describe a group of the earliest archosaurs that lived during the Permian and Triassic periods. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

The Crurotarsi are one of the two primary daughter clades of the Archosauria. The skull is often massively built, especially in contrast to ornithodires; the snout narrow and sometimes tending to be elongate, the neck is short and strong, and the limb posture ranging from typically reptilian sprawing to dinosaur or mammal-like erect (although this is achieved in a different way to dinosaurs and mammals). The body is often protected by two or more rows of armoured plates. Many forms reached large size; 3 meters or more in length. Groups Archosaurus Chasmatosaurus Euparkeria Crurotarsi     Aetosauria     Crocodilia (crocodiles)     Phytosauria     Rauisuchia Ornithodira     Pterosauria     Marasuchus     Dinosauria        Aves (birds) Archosaurs (Greek for ruling reptiles) are a group of diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian (Lower Triassic). ...

Crurotarsans seem to have appeared during the late Olenekian (early Triassic); by the Ladinian (late Middle Triassic) they dominated the terrestrial carnivore niches. Their heyday was the Late Triassic, during which time their ranks included erect-limbed rauisuchians, the crocodile-like phytosaurs, herbivorous armoured aetosaurs, the large predatory poposaurs, the small agile protocrocodilian Sphenosuchia, and a few other assorted groups. The Olenekian (also known as the Yongningzhenian) is a stage of the Early Triassic epoch. ... The Triassic is a geologic period that extends from about 245 to 202 Ma (million years ago). ... The Ladinian (also known as the Falangian) is a stage of the Middle Triassic epoch. ... The lion is a well-known, truly carnivorous member of the order Carnivora. ... Groups Family Prestosuchidae Family Rauisuchidae Family Poposauridae Rauisuchia are a poorly known assemblage of predatory and mostly large (often 4 to 6 meters) Triassic archosaurs. ... Phytosaurs - family Phytosauridae or Parasuchidae - were a group of large (2 to 12 meters long - average size 3 to 4 meters) semi-aquatic predatory thecodonts that flourished during the Late Triassic period. ... A deer and two fawns feeding on some foliage In zoology, an herbivore is an animal that is adapted to eat primarily plant matter (rather than meat). ... Genera Aetosaurus Coahomasuchus Desmatosuchus Longosuchus Neoaetosauroides Paratypothorax Redondasuchus Stagonolepis Typothorax The Aetosaurs (family Stagonolepididae or Aetosauridae) are an extinct clade of heavily armoured, medium to large sized, Late Triassic herbivorous archosaurs. ... Genera Bomsgroveia Poposaurus Postosuchus Sillosuchus Shuvosaurus Teratosaurus The Poposauridae are a family of large (around 2. ...

The end Triassic extinction, all of the large crurotarsans died out, allowing the dinosaurs to succeed them as rulers of the land. Only the little Sphenosuchia and the Protosuchia (Crocodylia) survived. The Triassic-Jurassic extinction event is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ...

As the Mesozoic proceeded, the Protosuchia gave rise to more typically crocodile like forms (the Crocodylia proper), and, while Dinosaurs were the dominant animals on land, the crocodiles flourished in rivers, swamps, and the ocean; with far greater diversity than they have today. The Mesozoic is one of three geologic eras of the Phanerozoic eon. ...

With the end Cretaceous extinction the tables were turned - the ornithodiran dinosaurs died out except for the birds while the curotarsan crocodylians continued with little change. Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ...

Today, the crocodiles, alligators, and gavials continue as the surviving representatives of this ancient and successful lineage. Genera Crocodylus Osteolaemus Tomistoma See full taxonomy. ... Genera Alligator Caiman Melanosuchus Paleosuchus Alligators and caimans are reptiles closely related to the crocodiles and forming the family Alligatoridae (sometimes regarded instead as the subfamily Alligatorinae). ... Binomial name Gavialis gangeticus (Gmelin, 1789) Taxonomy The Gharial (Gavialis gangeticus) is the only surviving member of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. ...

Taxonomy

• CRUROTARSI
  • Superorder Crocodylotarsi
    • Family Ornithosuchidae
    • Family Phytosauridae (=Parasuchia)
    • ORDER Suchia
      • Family Prestosuchidae
      • Suborder Rauisuchiformes
        • Superfamily Aetosauria
        • Superfamily Rauisuchia
          • Family Rauisuchidae
          • Family Ctenosauriscidae
            • Genus Postosuchus
          • Genus Gracilisuchus
          • Family Poposauridae
          • Genus Erpetosuchus
          • Superorder Crocodylomorpha
            • Family Sphenosuchidae
            • ORDER CROCODILIA

Phytosaurs - family Phytosauridae or Parasuchidae - were a group of large (2 to 12 meters long - average size 3 to 4 meters) semi-aquatic predatory thecodonts that flourished during the Late Triassic period. ... Genera Aetosaurus Coahomasuchus Desmatosuchus Longosuchus Neoaetosauroides Paratypothorax Redondasuchus Stagonolepis Typothorax The Aetosaurs (family Stagonolepididae or Aetosauridae) are an extinct clade of heavily armoured, medium to large sized, Late Triassic herbivorous archosaurs. ... Groups Family Prestosuchidae Family Rauisuchidae Family Poposauridae Rauisuchia are a poorly known assemblage of predatory and mostly large (often 4 to 6 meters) Triassic archosaurs. ... A Postosuchus from Walking with Dinosaurs Postosuchus was a basal archosaur (ruling lizard) which lived in what is now North America during the end of the Triassic period (220-205 million years ago). ... Gracilisuchus (meaning graceful crocodile) is the name given to a tiny (30 cm long) genus of thecodont from the Triassic. ... Genera Bomsgroveia Poposaurus Postosuchus Sillosuchus Shuvosaurus Teratosaurus The Poposauridae are a family of large (around 2. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

References

• Benton, M. J. (2004), Vertebrate Paleontology, 3rd ed. Blackwell Science Ltd
• Sereno, P. (1991), "Basal archosaurs: phylogenetic relationships and functional implications". Journal of Vertebrate Paleontology (Suppl.) 11: 1-51.

Michael Benton is a professor of vertebrate palaeontology in the Department of Earth Sciences at the University of Bristol. ...

External links

• EvoWiki
• Palaeos
• taxonomic hierarchy according to Benton 2004
• Mikko's Phylogeny