Diapsid

Various members of the Diapsida Above: North American copper head, Star Weber Middle: American alligator, Heterodontosaurus Below: Tupuxuara, Platypterygius

The Diapsida are a large group of reptiles ( Reptilia or Sauropsida ). These are the most diverse group of reptiles of the earth's history. The Diapsiden include purely terrestrial representatives, but also aquatic and capable of flying forms. Both the adjustment to life in the water as well as the ability to fly evolved several times independently in different Diapsidengruppen.

Features

The name " Diapsida " refers to the two openings in the cheek and temporal region ( tenses ) behind the eye socket (orbit ), which are called the upper and lower temporal or pace Ralf Rochester. This configuration is diapsider skull skull called (see also skull types of amniotes ). The function of the window lies in the reduction of bone mass and, concomitantly, a reduction in weight and a certain flexibility of the skull. Due to the temporal window through lead the tendons of the jaw muscles.

The lower opening is bounded by the same skull bones that are also involved in the single window in the skull fossil synapsids: squamosal (sq ), postorbital (po) and Jugale ( j ) and originally Quadratojugale ( qj ). The top window is bordered by squamosal, postorbital and parietal ( p), fossil representatives occurs not infrequently even the postfrontal added.

The diapside skull is indeed the principal feature of the Diapsiden, but it represents a more natural state, which was several times changed independently in various groups across the Diapsidenevolution:

  • The Schuppenkriechtieren ( Squamata ), which include, for example, include the lizards, as well as in some early forms of Archosauromorpha no lower Temporalbogen is present (so-called katapside skull configuration). Presumably both the lower Temporalbogen the tuatara as well as those of crocodiles not to the original diapside skull configuration of eg Petrolacosaurus back, but is secondary re- emerged from a katapsiden of state.
  • If the turtles are among the Diapsiden, then both temporal window would again completely closed with them.
  • Even with today's birds originally diapside skull anatomy is characterized by numerous modifications of the skull in the course of adaptation to the flies and the development of the musculoskeletal system of the beak no longer recognizable.
  • Likewise, both sub-groups of squamates, each with highly specialized, skulls, no obvious temporal windows are more in amphisbaenians and snakes present.

System

Basic

The Diapsida are traditionally viewed as a subclass of the class of reptiles ( Reptilia ). However, these groups are not natural kinship groups ( monophyla ). Birds and mammals are descended from permomesozoischen terrestrial vertebrates that fit the classic definition of Reptilia, since they established shelled eggs, but were both hairless and unfeathered. However, birds and mammals themselves do not conform to this classical definition and the Reptilia therefore not traditionally added. However, since this exclusion reflects the evolution is not correct, the classical concept of Reptilia has been replaced by the newer concept of Amniota. Amniotes are land vertebrates that can propagate independently of water.

Outer systematics

The amniotes are divided into two main lines: the Sauropsida ( Reptilia ) with today's reptiles and birds and the Synapsida with today's mammals. The Diapsiden are therefore a subset of Sauropsida. Incorporating fossil taxa with a disintegrate the Sauropsida or Reptilia into two major groups: the Eureptilia and Parareptilia ( Anapsida ). The Diapsiden are then a subset of Eureptilien.

Synapsida

Parareptilia †

Captorhinidae †

Paleothyris †

Diapsida

Inside systematics

The recent Diapsiden divided into two main groups: the scales of lizards ( Lepidosauria ) with the tuatara, " lizards " and snakes and the Archosauria with the crocodiles and birds. Again, involving fossil taxa systematics bit more complicated ( see below). According to recent findings are also likely the turtles Diapsiden.

The earliest fossil record of Diapsiden come from the Upper Carboniferous of North America. It involves relatively small, lizard -like agents, which have been described under the name Petrolacosaurus and Spinoaequalis. Both are very original Diapsiden who lived before the division into Lepidosauria and Archosauria.

  • Diapsida Araeoscelidia †
  • Avicephala †
  • Thalattosauria †
  • Younginiformes †
  • Ichthyosauria †
  • Lepidosauromorpha Eolacertilia †
  • Sauropterygia †
  • Shed lizards ( Lepidosauria ) Sphenodontia: tuatara and extinct relatives
  • Squamata ( Squamata ): " Lizards ", amphisbaenians and snakes
  • Choristodera †
  • Prolacertiformes †
  • Rhynchosauria †
  • Trilophosauria †
  • Archosauria Crurotarsi Aetosauria †
  • Phytosauria †
  • Rauisuchia †
  • Crocodylomorpha: crocodiles and extinct relatives
  • Pterosaur ( Pterosauria ) †
  • Dinosaurs ( Dinosauria ) Birds ( Aves)
Henry Fairfield Osborn Youngina Permian Coelurosauravus Arizonasaurus Ornithodira Digital Object Identifier Tree of Life Web Project
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