Diapsid

Source: Wikipedia, the free encyclopedia.

Diapsid reptiles
Temporal range:
Ma
Skull diagram of the
Petrolacosaurus kansensis
Nile crocodile (Crocodylus niloticus)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade:
Romeriida
Clade: Diapsida
Osborn, 1903
Subgroups

Diapsids ("two arches") are a clade of

classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds,[3] and 7,925 snakes, lizards, tuatara, turtles, and crocodiles.[4]

Characteristics

Anapsida

The name Diapsida means "two arches", and diapsids are traditionally classified based on their two ancestral skull openings (

jaw muscles, and enables the jaw to open more widely. A more obscure ancestral characteristic is a relatively long lower arm bone (the radius) compared to the upper arm bone (humerus
).

Classification

Diapsids were originally classified as one of four subclasses of the class

Anapsida (no skull opening, including turtles and their relatives), and Euryapsida (one opening high on the skull, including many prehistoric marine reptiles). With the advent of phylogenetic nomenclature, this system of classification was heavily modified. Today, the synapsids are often not considered true reptiles, while Euryapsida were found to be an unnatural assemblage of diapsids that had lost one of their skull openings. Genetic studies and the discovery of the Triassic Pappochelys
have shown that this is also the case in turtles, which are actually heavily modified diapsids. In phylogenetic systems, birds (descendants of traditional diapsid reptiles) are also considered to be members of this group.

Some modern studies of reptile relationships have preferred to use the name "diapsid" to refer to the crown group of all modern diapsid reptiles but not their extinct relatives. However, many researchers have also favored a more traditional definition that includes the prehistoric araeoscelidians. In 1991, Laurin defined Diapsida as a clade, "the most recent common ancestor of araeoscelidians, lepidosaurs, and archosaurs, and all its descendants".[5]

A cladistic analysis by Laurin and Piñeiro (2017) recovers

mesosaurs, who were found to be basal among the sauropsids.[7]

Relationships

Below is a cladogram showing the relations of the major groups of diapsids.

Cladogram after Bickelmann et al., 2009[8] and Reisz et al., 2011:[9]

 Sauropsida 
 †Parareptilia 
      

†

Millerettidae

  
    

†Eunotosaurus

 †
Hallucicrania
 
 Eureptilia 
    

†Captorhinidae

 
Romeriida
 
   

†Paleothyris

 Diapsida 

See also

References

  1. ^ "Those diverse diapsids".
  2. PMID 26934902
    .
  3. PMID 27880775
    .
  4. PMID 25803280
    .
  5. ^ Benton, M. J., Donoghue, P. C., Asher, R. J., Friedman, M., Near, T. J., & Vinther, J. (2015). "Constraints on the timescale of animal evolutionary history." Palaeontologia Electronica, 18.1.1FC; 1-106; palaeo-electronica.org/content/fc-1
  6. S2CID 32426159
    .
  7. S2CID 209673326
    .
  8. doi:10.1139/E09-038
    .
  9. PMID 21525061
    .

External links

Wikimedia Commons has media related to Diapsida.
  • Data related to Diapsid at Wikispecies
  • Diapsida. Michel Laurin and Jacques A. Gauthier. Tree of Life Web Project. June 22, 2000.
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