Dinosaur classification

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Dinosauria is a clade of archosaurs within the Phylum Chordata. 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."[1] In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure.[2] 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 1950s, 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 1990s, paleontologists became among the first zoologists to almost whole-heartedly adopt the system[citation needed]. 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 stabilzing 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.

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[edit] Benton classification

The following schema is from the third edition of Vertebrate Palaeontology,[3] 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.

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.

[edit] Order Saurischia

[edit] †Order Ornithischia

[edit] Weishampel/Dodson/Osmólska classification

The following is based on the second edition of the The Dinosauria[4], a compilation of articles by experts in the field that provided the most comprehensive coverage of Dinosauria available when it was first published in 1990. The second edition updates and revises that work.

The cladogram and phylogenetic definitions below reflect the current understanding of evolutionary relationships. The taxa and symbols in parentheses after a given taxa define these relationships. The plus symbol ("+") between taxa indicates the given taxa is a node-based clade, defined as comprising all descendants of the last common ancestor of the "added" taxa. The greater-than symbol (">") indicates the given taxa is a stem-based taxon, comprising all organisms sharing a common ancestor that is not also an ancestor of the "greater" taxon.

[edit] Saurischia

(Tyrannosaurus/Allosaurus > Triceratops/Stegosaurus)

[edit] Ornithischia

(Iguanodon/Triceratops > Cetiosaurus/Tyrannosaurus)

[edit] Footnotes

  1. ^ Owens, 1842.
  2. ^ Seeley, 1888. While the paper was published in 1888, it was first delivered in 1887.
  3. ^ Benton, 2004. The classification scheme is available online
  4. ^ Weishampel, 2004

[edit] References

  • Benton, Michael J. (2004). Vertebrate Palaeontology, Third Edition. Blackwell Publishing, 472 pp. 
  • Owen, Richard (1842). "Report on British Fossil Reptiles: Part II". Report of the British Association for the Advancement of Science 11: 60–204. 
  • Seeley, Harry Govier (1888). "One the classification of the Fossil Animals commonly named Dinosauria". Proceedings of the Royal Society of London 43: 165–171. .
  • Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.) (2004). The Dinosauria, Second Edition.. University of California Press., 861 pp. 

[edit] See also

Dinosaurs Portal