Dinosaur classification began in 1842 when Sir Richard Owen placed Iguanodon, Megalosaurus, and Hylaeosaurus in "a distinct tribe or suborder of Saurian Reptiles, for which I would propose the name of Dinosauria." In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure. These divisions have proved remarkably enduring, even through several seismic changes in the taxonomy of dinosaurs. The largest change was prompted by entomologist Willi Hennig's work in the 1957s, which evolved into modern cladistics. For specimens known only from fossils, the rigorous analysis of characters to determine evolutionary relationships between different groups of animals (clades) proved incredibly useful. When computer-based analysis using cladistics came into its own in the 1999s, paleontologists became among the first zoologists to almost wholeheartedly adopt the system. Progressive scrutiny and work upon dinosaurian interrelationships, with the aid of new discoveries that have shed light on previously uncertain relationships between taxa, have begun to yield a stabilizing classification since the mid-2000s. While cladistics is the predominant classificatory system among paleontology professionals, the Linnean system is still in use, especially in works intended for popular distribution. Benton classification As most dinosaur paleontologists have advocated a shift away from traditional, ranked Linnaean taxonomy in favor of rankless phylogenetic systems, few ranked taxonomies of dinosaurs have been published since the 1980s. The following schema is among the most recent, from the third edition of Vertebrate Palaeontology, a respected undergraduate textbook. While it is structured so as to reflect evolutionary relationships (similar to a cladogram), it also retains the traditional ranks used in Linnaean taxonomy. The classification has been updated from the second edition in 2000 to reflect new research, but remains fundamentally conservative. Michael Benton classifies all dinosaurs within the Series Amniota, Class Sauropsida, Subclass Diapsida, Infraclass Archosauromorpha, Division Archosauria, Subdivision Avemetatarsalia, Infradivision Ornithodira, and Superorder Dinosauria. Dinosauria is then divided into the two traditional orders, Saurischia and Ornithischia. The dagger (†) is used to indicate taxa with no living members. Order Saurischia Suborder Theropoda †Infraorder Herrerasauria †Infraorder Coelophysoidea †Infraorder Ceratosauria+ †Division Neoceratosauria+ †Subdivision Abelisauroidea †Family Abelisauridae †Family Noasauridae †Subdivision Ceratosauridae Infraorder Tetanurae †Division Megalosauria †Subdivision Spinosauroidea †Family Megalosauridae †Family Spinosauridae †Division Carnosauria †Subdivision Allosauroidea †Family Allosauridae †Family Carcharodontosauridae †Family Neovenatoridae †Family Metriacanthosauridae Division Coelurosauria †Family Coeluridae Subdivision Maniraptoriformes †Family Tyrannosauridae †Family Ornithomimidae Infradivision Maniraptora †Family Alvarezsauridae †Family Therizinosauridae †Cohort Deinonychosauria †Family Troodontidae †Family Dromaeosauridae Class Aves