Dinosauria taxonomy

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DINOSAUROMORPHA
Taxonomy Phylogeny - note that many of these early forms are scrappy and their relationships poorly known
o Ornithodira
|--Pterosauria
`--o DINOSAUROMORPHA
   |--Lagerpeton
   `--o Dinosauriformes
      |--Lagosuchus (Lagosuchidae)
      `--+?-Pseudolagosuchus (Lewisuchidae)
         `--+?-Teyuwasu
            |?-Silesaurus
            `--+?-Herrerasauria (or Saurischia/Theropoda)
               `--+?-Agnostiphitys
                  `--o Dinosauria
                     |--Ornithischia
                     `--Saurischia


Contents

The Historical development of Dinosaur Classification

This section is from Wikipedia

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 stucture. 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 modelling using cladistics came into its own in the 1990s, paleontologists became among the first zoologists to almost whole-heartedly adopt the system. The progressive mapping of the clade Dinosauria, with the help of new discoveries that have shed light on previously uncertain relationships between taxa, started to stablize in the mid-2000s and will culminate in the expected release of the PhyloCode. While cladistics is the dominant system among paleontology professionals, the Linnean system is still used by a few researchers, especially in works intended for popular distribution.

The next two sections are from Kheper

The Linnean/Evolutionary Systemic Classification

Pre-cladistic Classification

The Standard or Traditional Classification of Dinosaurs uses the Linnean and evolutionary systematic approach. This is confined now to older books. There are two orders, the Saurischia and the Ornithischia, distinguished on pelvis structure (one being, as the name indicates, more lizard- or crocodile-like, the other more bird-like). This basically goes as follows:

Order Saurischia
Suborder Theropoda
Infraorder Coelurosauria (small lightly built carnivores and omnivores)
Infraorder Carnosauria (large carnivores, allosaurs, tyrannosaurs, etc)
Suborder Sauropodamorpha
Infraorder Prosauropoda (early two-legged plant-eaters)
Infraorder Sauropoda (giant plant-eaters, brontosaurus etc)
Order Ornithischia
Suborder Ornithopoda (two legged herbivores)
Suborder Stegosauria (plated dinosaurs)
Suborder Ankylosauria (armoured dinosaurs)
Suborder Ceratopsia (horned dinosaurs)

When various new types of dinosaurs were discovered - dromaeosaurs, segnosaurs, heterodontosaurs, etc - these were usually slotted in extra subdivisions; the dromaeosaurs for example were included with the coelurosaurs, and the heterodontosaurs with the ornithopods. More recent books incorporate cladistic categories - e.g. Cerapoda, Maniraptora, Marginocephalia - but this introduces so many extra levels that the Linnean system breaks down.. Moreover, even the most recent dino books still retain the Saurischia-Ornithischia dichotomy (Herrerasaurs for example are usually included under the Saurischia).

Gregory Paul's Classification

A more controversial classification of the Dinosauria is presented by Gregory S. Paul in his Predatory Dinosaurs of the World (1988), to my mind still the best book on dinosaurs ever written (albeit looking rather dated and with some rather dubious metabolic assumptions). GSP suggests the following arrangement (based in part on Robert T. Bakker):

Subclass or Infraclass Dinosauria
Superorder Paleodinosauria (proto-dinosaurs)
Superorder Herreravia (primitive bird-like forms)
Superorder Theropoda (meat-eaters, and protobirds)
Superorder Phytodinosauria (plant-eaters - Sauropodamorphs and Ornithischia)

These inflated taxonomic rankings appear to be an attempt to reconcile the Linnean and Cladistic systems; generally such attempts don't work.

The Cladistic Classification

The dominant paradigm in biological systematics now is Cladism, and so most dino sites on the Web tend to be cladistically based. Cladism can get quite abstract and confusing, mainly because it is so abstract. Consider the cladistic definition of the Dinosauria.

Dinosauria = all descendants of the most recent common ancestor of Triceratops and Neornithes (modern birds).

Triceratops is mentioned because it is a creature as far away on the dinosaur family tree from birds as can be, yet it it's skeleton is well-known so it can be compared and contrasted with other species. Neornithes or modern birds are mentioned beuse they are the most specialised descendents of the dinosaurs, and indeed the only living dinosaurian descendents.

From the above equation the various dinosaurian subtaxa can be deduced: e.g.

Saurischia = Neornithes and all taxa closer to it than to Triceratops
Theropoda = Neornithes and all taxa closer to it than to Sauropodomorpha.
etc...

From these basic clades, further subclades can be derived, and more subclades in rurn from them. There are no orders, suborders, etc. Families and subfamilies are retained only as a conventient way of linking two genera, and so used in a different manner to in the Linnean scheme. Attempts to reconcile the two systems are fraught with difficulties.

The whole thing can be quite abstract, although there is also a certain mathematical logic in it; it's like set theory. Instead of Linnean categories such as "Dinosaura", (or "Mammalia" "Reptilia" or any other taxonomic grouping above species level), there is only a nested series of monophyletic clades, one within the other, like layers of an onion, all based on a MRCA (Most Recent Common Ancestor).

The rest of this page is from Wikipedia

Modified Benton classification

The following schema is based on the third edition of Vertebrate Paleontology (Benton, 2004), a respected college textbook. While it is structured so as to reflect evolutionary relationships (similar to a cladogram or evolutionary tree), 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 the 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.

In accordance with Wikipedia:WikiProject Tree of Life, Benton's taxonomy is used in all vertebrate taxoboxes and modified in the following ways:

  • Limited number of ranks. Ranks beginning with Micro-, or non-standard animal ranks such as Division and Cohort, etc. are listed as (Unranked) for the sake of simplification. Only Super-, Sub-, and Infra- ranks are preserved.
  • Oviraptorosaurs are non-avian. Benton's latest taxonomy includes Oviraptorosauria within Class Aves, which is a minority view that is not yet well-supported (though all maniraptorans are avian under the traditional apomorphy-based definition of the group).
  • The number and content of family-level taxa may vary based on the latest cladistic research.

Benton's latest taxonomy can be found here: http://palaeo.gly.bris.ac.uk/benton/vertclass.html. Below is the modified version used on Wikipedia:

Order Saurischia

†Order Ornithischia

Weishampel/Dodson/Osmólska classification

The following is based on the second edition of the The Dinosauria (Eds. Weishampel, Dodson & Osmólska, 2004), 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 more recent common ancestor with the "greater" taxon.

Saurischia

(Tyrannosaurus/Allosaurus > Triceratops/Stegosaurus)

Ornithischia

(Iguanodon/Triceratops > Cetiosaurus/Tyrannosaurus)

  •  ? Lesothosaurus diagnosticus
  •  ? Heterodontosauridae
  • Genasauria (Ankylosaurus + Triceratops)
    • Thyreophora (Ankylosaurus > Triceratops)
      • Scelidosauridae
      • Eurypoda (Ankylosaurus + Stegosaurus)
        • Stegosauria (Stegosaurus > Ankylosaurus)
          • Huayangosauridae (Huayangosaurus > Stegosaurus)
          • Stegosauridae (Stegosaurus > Huayangosaurus)
            • Dacentrurus armatus
            • Stegosaurinae (Stegosaurus > Dacentrurus)
        • Ankylosauria (Ankylosaurus > Stegosaurus)
          • Ankylosauridae (Ankylosaurus > Panoplosaurus)
            • Gastonia burgei
            • Shamosaurus scutatus
            • Ankylosaurinae (Ankylosaurus > Shamosaurus)
          • Nodosauridae (Panoplosaurus > Ankylosaurus)
    • Cerapoda (Triceratops > Ankylosaurus)
      • Ornithopoda (Edmontosaurus > Triceratops)
        •  ? Lesothosaurus diagnosticus
        •  ? Heterodontosauridae
        • Euornithopoda
          • Hypsilophodon foxii
          • Thescelosaurus neglectus
          • Iguanodontia (Edmontosaurus > Thescelosaurus)
            • Tenontosaurus tilletti
            • Rhabdodontidae
            • Dryomorpha
              • Dryosauridae
              • Ankylopollexia
                • Camptosauridae
                • Styracosterna
                  • Lurdusaurus arenatus
                  • Iguanodontoidea (=Hadrosauriformes)
      • Marginocephalia
        • Pachycephalosauria (Pachycephalosaurus wyomingensis > Triceratops horridus)
          • Goyocephala (Goyocephale + Pachycephalosaurus)
            • Homalocephaloidea (Homalocephale + Pachycephalosaurus)
              • Homalocephalidae
              • Pachycephalosauridae
        • Ceratopsia (Triceratops > Pachycephalosaurus)
          • Psittacosauridae
          • Neoceratopsia
            • Coronosauria
              • Protoceratopsidae
              • Bagaceratopidae
              • Ceratopsoidea
                • Leptoceratopsidae
                • Ceratopsomorpha

References

  • Owen, Richard. 1842. "Report on British Fossil Reptiles." Part II. Report of the British Association for the Advancement of Science, Plymouth, England.
  • Weishampel, David B., Peter Dodson, and Halszka Osmólska (Eds.). 2004. The Dinosauria, Second Edition. University of California Press, 861 pp. ISBN 0-520-24209-2.

Credits

Page contains material from Kheper MAK981211 ; Wikipedia 2004-2006; this page MAK061024

This page incorporates material from Wikipedia which is available under the terms of the GNU Free Documentation License. Wikipedia url for material on this page:
http://en.wikipedia.org/wiki/Dinosaur_classification
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