Diapsida

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Parent taxa:

(check the following menu and phylogeny - the taxon in bold refers to the topic on this page)

SAUROPSIDA - The Reptiles

Taxonomy

Phylogeny

Subphylum: Vertebrata
Superclass: Tetrapoda
Class: REPTILIA

Subclass: Anapsida
Subclass: Diapsida

(incl. Euryapsida & Parapsida)

o Amniota   (Reptilia grade begins here)
|--o SAUROPSIDA = Reptilia when Mesosaurs are placed within Parareptiles (clade)
|  |?--Mesosauria
|  |--o Anapsida/Parareptilia
|  `--o Eureptilia
|     |--Captorhinidae
|     `--o=="Protorothyrididae" (grade)
|        `--Diapsida
`--Synapsida

Diapsida

1 Introduction and evolutionary history
2 Information
3 Characters
4 Phylogeny
5 References
6 Links
7 Credits

[edit] Introduction and evolutionary history

The Eureptilia would have been a footnote in the history of turtles and mammals but for the evolution of the diapsids. The bulk of reptiles fall into the Diapsida. The Diapsida ("two arches") are so called because they have two (di-) skull openings on either side of the head, for attachment of temporal muscles (to work the jaw). However it is now known that some reptiles lost one or even both pairs of openings, so the presence or absence of this characteristic is not a completely reliable guide.

The Diapsida are divided into two important groups, the lepidosaurs (Lepidosauromorpha) and the archosaurs (Archosauromorpha). There are also a number of different lineages of early, mostly small lizard-like insectivorous forms that lived during the late Carboniferous, Permian, and Triassic periods. These have been traditionally grouped under the "Eosuchia," but it is now known that this is an artificial taxon, a "waste basket" category for any diapsid that is neither lepidosaur nor archosaur. Nevertheless the term retains some use as a synonym for "basal diapsid." MAK991026.

(The following menu and phylogeny refers to subtopics of this page)

DIAPSIDA

Taxonomy

Phylogeny

Subphylum: Vertebrata
Class: Reptilia
Subclass: DIAPSIDA

o Eureptilia
`--o DIAPSIDA
   |--Araeoscelidia (paraphyletic?)
   `--+?--Avicephala
      `--o Neodiapsida
         |?-Coelurosauravidae
         `--+--Apsisaurus
            `--+?-Claudiosaurus
               `--o==Younginiformes (paraphyletic?)
                  `--+?-Ichthyopterygia
                     `--o Sauria
                        |--Lepidosauromorpha
                        `--Archosauromorpha

[edit] Information

Range: from the Late Carboniferous.

Phylogeny: Eureptilia:: Protorothyrididae + Diapsida: Araeoscelidans + Neodiapsida.

Author: Osborn, 1903

[edit] Characters

Characters: Upper (triradiate squamosal & triradiate post-orbital) and lower temporal fenstrae; $ suborbital fenestra consisting of a relatively large hole in the palate located between palatine, ectopterygoid, and maxilla [Other taxa may have foramen in this region, but there is usually no fenestra]; ossified sternum; $ (primitively) radius long, measuring 70 - 90% of humerus length; ridge-and-groove ankle joint between tibia and astragalus.

Note: Domed skull of Amniotes permits muscles to run vertically. Vertical muscles allow strong static pressure when jaws are closed or almost closed. Increase in muscle bulk would strain periosteal covering of bone. Fenestrae may have evolved as unossified attachment points. Later, evolved as openings which "bulging" of these jaw muscles. Note no obvious change in jaw musculature in primitive forms. ATW010731.

[edit] Phylogeny

<==Diapsida
   |  i. s.: Rhabdopelix Cope 1899
   |         Icarosaurus siefkeri
   |         Coelurosauravus
   |         Daedalosaurus
   |--Petrolacosaurus kansensis Lane 1945
   `--Neodiapsida [Sauria]
        |--+--Plesiosauroidea
        |  `--Lepidosauromorpha
        |       |  i. s.: Coartaredens Spencer & Storrs 2002
        |       |           `--*C. isaaci Spencer & Storrs 2002
        |       |         Anisodontosaurus greeri
        |       |--Palaeagama
        |       |--Younginiformes
        |       `--+--Paliguana
        |          |--Saurosternon
        |          `--+--Kuehneosaurus [Kuehneosauridae]
        |             `--Lepidosauria
        `--Archosauromorpha
             |--Archosauria
             |--Rhynchosaurus [Rhyncosauria]
             |    |--R. articeps
             |    `--R. spenceri
             `--Prolacertiformes
                  |--Macrocnemus
                  |--Longobardisaurus
                  |--Sharovipteryx Cowen 1981 [=Podopteryx Sharov 1971 (preoc.)]
                  |--Cosesaurus
                  |--Longisquama Sharov 1971
                  `--Tanystropheus [incl. Tribelesodon]
                       `--T. longobardicus [=Tribelesodon longobardicus]

* Type species of genus indicated

[edit] References

Bonde, N., & P. Christiansen. 2003. The detailed anatomy of Rhamphorhynchus: Axial pneumaticity and its implications. In Evolution and Palaeobiology of Pterosaurs (E. Buffetaut & J.-M. Mazin, eds.) Geological Society Special Publications 217: 217-232. The Geological Society: London.

Dalla Vecchia, F. M. 2003. New morphological observations on Triassic pterosaurs. In Evolution and Palaeobiology of Pterosaurs (E. Buffetaut & J.-M. Mazin, eds.) Geological Society Special Publications 217: 23-44. The Geological Society: London.

Miller, S. A., & J. P. Harley. 1996. Zoology (3rd ed.) Wm. C. Brown Publishers: Dubuque (Iowa).

Queiroz, K. de, & J. Gauthier. 1990. Phylogeny as a central principle in taxonomy: Phylogenetic definitions of taxon names. Systematic Zoology 39 (4): 307-322.

Ruta, M., M. I. Coates & D. L. J. Quicke. 2003. Early tetrapod relationships revisited. Biological Reviews 78: 251-345.

Spencer, P. S., & G. W. Storrs. 2002. A re-evaluation of small tetrapods from the Middle Triassic Otter Sandstone Formation of Devon, England. Palaeontology 45 (3): 447-467.

Unwin, D. M. 2003. On the phylogeny and evolutionary history of pterosaurs. In Evolution and Palaeobiology of Pterosaurs (E. Buffetaut & J.-M. Mazin, eds.) Geological Society Special Publications 217: 139-190. The Geological Society: London.

Wellnhofer, P. 1991. The Illustrated Encyclopedia of Pterosaurs. Salamander Books: London (reprinted 2000, in The Illustrated Encyclopedia of Dinosaurs (D. Norman & P. Wellnhofer). Salamander Books).

Wills, L. J. 1970. The Triassic succession in the central Midlands in its regional setting. Quarterly Journal of the Geological Society of London 126: 225-283.