Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ago during the late Carboniferous period.[1] All diapsids other than the most primitive ones in the clade Araeoscelidia are sometimes placed into the clade Neodiapsida. The diapsids are extremely diverse, and include birds and all modern reptile groups, including turtles, which were historically thought to lie outside the group.[2] Although some diapsids have lost either one hole (lizards), or both holes (snakes and turtles), or have a heavily restructured skull (modern birds), they are still 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]
Diagram of the diapsid skull with temporal openings, unlike in Anapsida
The name Diapsida means "two arches", and diapsids are traditionally classified based on their two ancestral skull openings (temporal fenestrae) posteriorly above and below the eye. This arrangement allows for the attachment of larger, stronger 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).
Classificationedit
Diapsids were originally classified as one of four subclasses of the class Reptilia, all of which were based on the number and arrangement of openings in the skull. The other three subclasses were Synapsida (one opening low on the skull, for the "mammal-like reptiles"), 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 Parareptilia as part of Diapsida, with pareiasaurs, turtles, millerettids, and procolophinoids recovered as more derived than the basal diapsid Younginia.[6] A 2020 study by David P. Ford and Roger B. J. Benson also recovered Parareptilia as deeply nested within Diapsida as the sister group to Neodiapsida, But this excludes mesosaurs, who were found to be basal among the sauropsids.[7]
Relationshipsedit
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]
^Schoch, Rainer R.; Sues, Hans-Dieter (2016). "The diapsid origin of turtles". Zoology. 119 (3): 159–161. doi:10.1016/j.zool.2016.01.004. PMID 26934902.
^Barrowclough, George F.; Cracraft, Joel; Klicka, John; Zink, Robert M. (23 November 2016). "How Many Kinds of Birds Are There and Why Does It Matter?". PLOS ONE. 11 (11): e0166307. Bibcode:2016PLoSO..1166307B. doi:10.1371/journal.pone.0166307. PMC5120813. PMID 27880775.
^Reeder, Tod W.; Townsend, Ted M.; Mulcahy, Daniel G.; Noonan, Brice P.; Wood, Perry L.; Sites, Jack W.; Wiens, John J. (2015). "Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa". PLOS ONE. 10 (3): e0118199. Bibcode:2015PLoSO..1018199R. doi:10.1371/journal.pone.0118199. PMC4372529. PMID 25803280.
^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
^Laurin, Michel; Piñeiro, Graciela H. (2017). "A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes" (PDF). Frontiers in Earth Science. 5: 88. Bibcode:2017FrEaS...5...88L. doi:10.3389/feart.2017.00088. S2CID 32426159.
^Ford DP, Benson RB (January 2020). "The phylogeny of early amniotes and the affinities of Parareptilia and Varanopidae". Nature Ecology & Evolution. 4 (1): 57–65. doi:10.1038/s41559-019-1047-3. PMID 31900445. S2CID 209673326.
^Constanze Bickelmann, Johannes Müller and Robert R. Reisz (2009). "The enigmatic diapsid Acerosodontosaurus piveteaui (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of younginiform reptiles". Canadian Journal of Earth Sciences. 49 (9): 651–661. Bibcode:2009CaJES..46..651S. doi:10.1139/E09-038.
^Robert R. Reisz, Sean P. Modesto and Diane M. Scott (2011). "A new Early Permian reptile and its significance in early diapsid evolution". Proceedings of the Royal Society B. 278 (1725): 3731–7. doi:10.1098/rspb.2011.0439. PMC3203498. PMID 21525061.
External linksedit
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.
November 28, 2023
diapsid, arches, clade, sauropsids, distinguished, from, more, primitive, eureptiles, presence, holes, known, temporal, fenestrae, each, side, their, skulls, group, first, appeared, about, three, hundred, million, years, during, late, carboniferous, period, di. Diapsids two arches are a clade of sauropsids distinguished from more primitive eureptiles by the presence of two holes known as temporal fenestrae in each side of their skulls The group first appeared about three hundred million years ago during the late Carboniferous period 1 All diapsids other than the most primitive ones in the clade Araeoscelidia are sometimes placed into the clade Neodiapsida The diapsids are extremely diverse and include birds and all modern reptile groups including turtles which were historically thought to lie outside the group 2 Although some diapsids have lost either one hole lizards or both holes snakes and turtles or have a heavily restructured skull modern birds they are still 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 Diapsid reptilesTemporal range Pennsylvanian Present 302 0 Ma PreꞒ Ꞓ O S D C P T J K Pg NSkull diagram of the araeoscelidian Petrolacosaurus kansensisNile crocodile Crocodylus niloticus Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass ReptiliaClade RomeriidaClade DiapsidaOsborn 1903Subgroups Dolerosaurus Araeoscelidia Parareptilia Neodiapsida Contents 1 Characteristics 2 Classification 2 1 Relationships 3 See also 4 References 5 External linksCharacteristics edit nbsp Diagram of the diapsid skull with temporal openings unlike in AnapsidaThe name Diapsida means two arches and diapsids are traditionally classified based on their two ancestral skull openings temporal fenestrae posteriorly above and below the eye This arrangement allows for the attachment of larger stronger 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 editDiapsids were originally classified as one of four subclasses of the class Reptilia all of which were based on the number and arrangement of openings in the skull The other three subclasses were Synapsida one opening low on the skull for the mammal like reptiles 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 Pineiro 2017 recovers Parareptilia as part of Diapsida with pareiasaurs turtles millerettids and procolophinoids recovered as more derived than the basal diapsid Younginia 6 A 2020 study by David P Ford and Roger B J Benson also recovered Parareptilia as deeply nested within Diapsida as the sister group to Neodiapsida But this excludes mesosaurs who were found to be basal among the sauropsids 7 Relationships edit 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 nbsp unnamed Eunotosaurus Hallucicrania Lanthanosuchidae nbsp Procolophonia Procolophonoidea nbsp Pareiasauromorpha nbsp Eureptilia Captorhinidae nbsp Romeriida PaleothyrisDiapsida AraeoscelidiaNeodiapsida Orovenator Lanthanolania Tangasauridae Younginidae Claudiosaurus Palaeagama Saurosternon Coelurosauravus Thalattosauria Hupehsuchia IchthyopterygiaSauria LepidosauromorphaArchosauromorphaSee also editVertebrate paleontology Synapsida Anapsida EuryapsidaReferences edit Those diverse diapsids Schoch Rainer R Sues Hans Dieter 2016 The diapsid origin of turtles Zoology 119 3 159 161 doi 10 1016 j zool 2016 01 004 PMID 26934902 Barrowclough George F Cracraft Joel Klicka John Zink Robert M 23 November 2016 How Many Kinds of Birds Are There and Why Does It Matter PLOS ONE 11 11 e0166307 Bibcode 2016PLoSO 1166307B doi 10 1371 journal pone 0166307 PMC 5120813 PMID 27880775 Reeder Tod W Townsend Ted M Mulcahy Daniel G Noonan Brice P Wood Perry L Sites Jack W Wiens John J 2015 Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa PLOS ONE 10 3 e0118199 Bibcode 2015PLoSO 1018199R doi 10 1371 journal pone 0118199 PMC 4372529 PMID 25803280 Benton M J Donoghue P C Asher R J Friedman M Near T J amp Vinther J 2015 Constraints on the timescale of animal evolutionary history Palaeontologia Electronica 18 1 1FC 1 106 palaeo electronica org content fc 1 Laurin Michel Pineiro Graciela H 2017 A Reassessment of the Taxonomic Position of Mesosaurs and a Surprising Phylogeny of Early Amniotes PDF Frontiers in Earth Science 5 88 Bibcode 2017FrEaS 5 88L doi 10 3389 feart 2017 00088 S2CID 32426159 Ford DP Benson RB January 2020 The phylogeny of early amniotes and the affinities of Parareptilia and Varanopidae Nature Ecology amp Evolution 4 1 57 65 doi 10 1038 s41559 019 1047 3 PMID 31900445 S2CID 209673326 Constanze Bickelmann Johannes Muller and Robert R Reisz 2009 The enigmatic diapsid Acerosodontosaurus piveteaui Reptilia Neodiapsida from the Upper Permian of Madagascar and the paraphyly of younginiform reptiles Canadian Journal of Earth Sciences 49 9 651 661 Bibcode 2009CaJES 46 651S doi 10 1139 E09 038 Robert R Reisz Sean P Modesto and Diane M Scott 2011 A new Early Permian reptile and its significance in early diapsid evolution Proceedings of the Royal Society B 278 1725 3731 7 doi 10 1098 rspb 2011 0439 PMC 3203498 PMID 21525061 External links edit nbsp Wikimedia Commons has media related to Diapsida nbsp Data related to Diapsid at Wikispecies Diapsida Michel Laurin and Jacques A Gauthier Tree of Life Web Project June 22 2000 Retrieved from https en wikipedia org w index php title Diapsid amp oldid 1123967067, wikipedia, wiki, book, books, library,
