Dinosaurs. Douglas Palmer

herrerasaurids, and the two groups of sauropodomorphs and theropods belong to the saurischian group..

       From the sauropodomorphs follow two distinct groups: prosauropods (leading to anchisaurids and plateosaurids) and sauropods..

       From sauropods follow Vulcanodon and eusauropods..

       From eusauropods follow Mamenchisaurus, cetiosaurids and neosauropods..

       From neosauropods follow two distinct groups: diplodocoids (leading to discraeosaurids and diplodocids) and macronarians..

       From macronarians follow camarasaurids, brachiosaurids, Euhelopus, saltasaurids, and titanosaurians..

      A final group of small to medium-sized meat-eating bipedal saurischians is still difficult to categorize. These include Herrerasaurus, Eoraptor and Staurikosaurus, which have been found in Late Triassic rocks, especially in South America. Although it is still not clear what their relationships are to the main groups of saurischians, these dinosaurs were certainly more like the theropods than the sauropodomorphs.

      Caption:

      A tree diagram showing theropod relationships. From right to left:

       Tetanurans, ceratosaurians and coelophysoids belong to the theropods group..

       Ceratosaurians include neoceratosaurians and Ceratosaurus..

      Following on from tetanurans:

       From tetanurans follow avetheropodans and spinosauroids (leading to spinosaurids and megalosaurids)..

       From avetheropodans follow coelurosaurians and carnosaurians (leading to carcharodontosaurids and allosaurids)..

       From coelurosaurians follow maniraptorans, compsognathids, ornithomimosaurians and tyrannosauroids..

       From maniraptorans follow the group known as eumaniraptorans, as well as oviraptorosaurians and therizinosauroids..

       From eumaniraptorans follow the group known as avialans (leading to modern birds and Archaeopteryx), as well as dromaeosaurids and troodontids..