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Diapsida
Temporal range: Permian–Present possible Late Carboniferous records
Reconstructed skull of Youngina (a basal member of Neodiapsida)
Nile crocodile (Crocodylus niloticus)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Romeriida
Clade: Diapsida
Osborn, 1903
Subgroups

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 earliest traditionally identified diapsids, the araeoscelidians, 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 often 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] All modern reptiles and birds are placed within the neodiapsid subclade Sauria. 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]

Characteristics

[edit]
Diagram of the diapsid skull with temporal openings, unlike in anapsids

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).

Basal non-saurian neodiapsids were ancestrally lizard-like, but basal non-saurian neodiapsids include aquatic/amphibious taxa (Claudiosaurus and some tangasaurids)[5] the gliding lizard-like Weigeltisauridae,[6] as well as the Triassic chameleon-like drepanosaurs.[7]

Classification

[edit]

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".[8]

The clade Neodiapsida was given a phylogenetic definition by Laurin in 1991. He defined it as the branch-based clade containing all animals more closely related to "Younginiformes" (later, more specifically, emended to Youngina capensis) than to Petrolacosaurus (representing Araeoscelidia).[9] The earliest known neodiapsids like Orovenator are known from the Early Permian, around 290 million years ago.[10]

All genetic studies have supported the hypothesis that turtles are cladistically diapsid reptiles despite being morphologically anapsid, most placing them as more closely related to living archosaurs (including crocodiles and birds) than to lepidosaurs (lizards, snakes, etc).[11][12][13][14]

Modern reptiles and birds are placed within the neodiapsid subclade Sauria, defined as the last common ancestor of Lepidosauria (which includes lizards, snakes and the tuatara), and Archosauria (which includes crocodilians and dinosaurs, including birds, among others).[15]

A cladistic analysis by Laurin and Piñeiro (2017) recovers Parareptilia as part of Diapsida, with pareiasaurs, turtles, millerettids, and procolophonoids recovered as more derived than the basal diapsid Younginia.[16] 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. They united this relationship between Parareptilia and Neodiapsida in the new clade Neoreptilia, defining it as the last common ancestor and all descendants of Procolophon trigoniceps and Youngina capensis.[17] However, this excludes mesosaurs, who were found to be basal among the sauropsids.[17] Other recent studies have found the more traditional arrangement of parareptiles being outside of Diapsida.[15]

The position of the highly derived Mesozoic marine reptile groups Thalattosauria, Ichthyosauromorpha and Sauropterygia within Neodiapsida is uncertain, and they may lie within Sauria.[15][18]

In the 2022 and 2023 studies, Araeoscelidia was found to have no close relationship with Neodiapsida and was not even part of Sauropsida.[15][19]

Relationships

[edit]

Below are cladograms showing the relations of the major groups of diapsids.

Cladogram after Bickelmann et al., 2009[20] and Reisz et al., 2011:[21]

The cladogram of Lee (2013) below used a combination of genetic (molecular) and fossil (morphological) data.[22]

Diapsida

This second cladogram is based on the 2017 study by Pritchard and Nesbitt.[23]

Neodiapsida

The following cladogram was found by Simões et al. (2022): [15]

Neoreptilia

The following cladogram was found by Jenkins et al. (2025).[24] Traditional parareptiles are highlighted in orange:

Diapsida

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Diapsid

View on Grokipedia
from Grokipedia
Diapsids (Diapsida) are a major of sauropsid amniotes characterized by the presence of two temporal fenestrae—openings in the behind the eye sockets—allowing for stronger muscles and lighter compared to more basal reptiles. This defining trait, bridged by bony arches, distinguishes diapsids from synapsids (mammal relatives) and anapsids (a mostly extinct group with no temporal fenestrae), though some diapsids like have secondarily reduced or closed these openings. Originating in the Late period around 310–300 million years ago, diapsids represent one of the most successful radiations, encompassing nearly all modern reptiles and birds, as well as numerous extinct lineages that dominated ecosystems. The clade diversified rapidly in the Permian and periods, evolving adaptations for diverse terrestrial, aquatic, and aerial lifestyles, including elongated limbs for speed in early forms like the basal diapsid Petrolacosaurus kansensis. Key characteristics beyond the skull include a suborbital (an opening under the eye), a ridged-grooved joint between the and astragalus for improved locomotion, and often elongated, slender bodies suited for agile movement. Diapsids achieved ecological dominance in the era, with subgroups like ichthyosaurs and plesiosaurs conquering marine environments, pterosaurs taking to the skies, and dinosaurs becoming the largest terrestrial animals ever known. Phylogenetically, Diapsida is divided into major subgroups: Lepidosauromorpha, which includes lepidosaurs (tuataras, lizards, and snakes) with scaly skin and flexible skulls; and Archosauromorpha, encompassing archosaurs (crocodilians, dinosaurs, and birds) and turtles as a specialized sister group to archosaurs, supported by molecular and fossil evidence. Extinct "euryapsid" reptiles, such as ichthyosaurs, were once considered separate but are now recognized as diapsids that independently evolved a single upper temporal fenestra. Today, diapsids comprise over 20,000 living species, far outnumbering mammals in diversity, and continue to illustrate evolutionary innovations like endothermy in birds and venom in some squamates.

Anatomy and Morphology

Skull Features

The diapsid skull is defined by the presence of two pairs of located behind each , consisting of an upper temporal fenestra (supratemporal fenestra) and a lower temporal fenestra (infratemporal fenestra), which distinguish diapsids from other groups like anapsids and synapsids. These openings provide expanded attachment sites for the adductor muscles, enabling greater muscle mass and improved compared to skulls with fewer or no fenestrae. The evolved in early diapsids from anapsid-like ancestral skulls through the separation of dermal bones, resulting in a lighter yet structurally robust cranium that accommodated expanding musculature. The upper is framed anteriorly by the postorbital bone and posteriorly by the squamosal bone, while the lower is bounded anteriorly by the postorbital and jugal bones and posteriorly by the squamosal and quadratojugal bones. In basal diapsids such as , these fenestrae are prominent, with the postorbital forming the anterior margin of the upper opening and the jugal contributing to the lower margin, reflecting the primitive configuration. Across diapsid subgroups, the fenestrae exhibit significant variations, including fusion, reduction, or modification, often linked to specialized lifestyles. In , the e are secondarily closed or reduced to an anapsid-like condition through bone overgrowth, despite their diapsid ancestry. In birds, the skull is highly modified, with the lower temporal fenestra often lost or incorporated into a single enlarged opening, and the upper altered to support a kinetic cranium adapted for lightweight flight. These fenestrae play a crucial role in feeding mechanics by allowing the jaw adductor muscles to bulge outward during contraction, thereby enhancing bite force and gape without compromising skull integrity. In early diapsids like , a basal form from the Late , the fenestrae facilitated stronger jaw closure for capturing prey, with the openings constituting a substantial portion of the postorbital skull region alongside orbits that occupy approximately 38% of total skull length.

Postcranial Skeleton

The postcranial skeleton of diapsids exhibits an elongated trunk supported by a vertebral column typically comprising 20–30 presacral vertebrae, differentiated into cervical, dorsal, and sacral regions, followed by an extended caudal series that varies in length across taxa. In basal forms such as Teyujagua paradoxa, the column includes nine , at least six dorsal vertebrae (with possibly more obscured in the matrix), and two sacral vertebrae, providing flexibility for while accommodating body elongation. This regional differentiation allows for specialized functions, with enabling neck mobility, dorsal vertebrae supporting the trunk, and sacral vertebrae anchoring the pelvic girdle. Limb structure in basal diapsids features pentadactyl extremities with a phalangeal formula of 2-3-4-5-3 in the manus, reflecting the ancestral condition adapted for sprawling or semi-erect postures. The and are robust, with the sprawling posture characteristic of early diapsids positioning limbs laterally to the body, facilitating low-speed terrestrial movement, as seen in Permian neodiapsids like Saurosternon bainii. In more derived forms, such as archosauromorphs, a transition toward semi-erect postures occurs, enhancing stride efficiency without fully erect limb alignment. The pectoral girdle consists of a robust scapula- complex that articulates with the to support weight and movement, while the pelvic girdle features distinct ilium, , and pubis bones forming a sturdy for attachment. These structures provide ventral bracing and weight distribution essential for terrestrial support, with the serving as a key anchor for musculature in basal diapsids. In aquatic and taxa, girdle robustness varies to accommodate specialized locomotion. Specific adaptations in the postcranial skeleton highlight diapsid diversification; kuehneosaurids, such as Kuehneosuchus, feature elongated mid-dorsal that extend laterally to support a skin membrane, forming cambered "wings" for controlled descent at angles of 13–16° and speeds up to 9 m/s. Ontogenetic changes in diapsid skeletons reveal increased rigidity with maturity, as evidenced by growth series; juvenile specimens of Eusaurosphargis dalsassoi exhibit incomplete of neurocentral sutures, transverse processes, and carpal/tarsal elements, conferring greater flexibility compared to adults with fused osteoderms and robust endoskeletal connections. This pattern, observed in diapsids, likely facilitated early mobility before skeletal consolidation in later stages.

Evolutionary History

Origins and Fossil Record

Diapsids first appeared during the Late Carboniferous period, approximately 310 to 300 million years ago, with the oldest potential fossils representing stem-sauropsids emerging in Late Pennsylvanian deposits of North America and Europe. These early forms mark the transition from amphibian-like ancestors to fully terrestrial reptiles, characterized by adaptations such as amniotic eggs and scaly skin, though definitive diapsid skull features like paired temporal fenestrae appear slightly later. Key fossil localities include the Mazon Creek Lagerstätte in Illinois, which preserves early tetrapod taxa in ironstone concretions dating to around 309 million years ago, providing insight into the initial diversification of sauropsids in a swampy, deltaic environment. In contrast, the Permian red beds of Texas, particularly formations like the Clear Fork Group dated to about 290 million years ago, yield basal neodiapsids that exhibit more advanced diapsid traits and highlight the group's expansion into arid terrestrial habitats. Among the diagnostic early fossils, lyelli from the Joggins Formation in stands out as a potential stem-sauropsid precursor, with its small, lizard-like skeleton (about 20 cm long) recovered from tree stump hollows and dated to roughly 312 million years ago, suggesting an insectivorous lifestyle in forested ecosystems. The Petrolacosaurus kansensis, from the Upper Pennsylvanian Elmo Formation in (approximately 302 million years ago), represents the earliest unambiguous diapsid, featuring a slender body up to 40 cm long and a with distinct upper and lower temporal fenestrae that facilitated musculature attachment. These fenestrae, briefly, underscore the anatomical innovation distinguishing diapsids from earlier anapsid-like reptiles. Stratigraphically, diapsids show increasing abundance from the Late Permian through the , with hundreds of described taxa documenting their radiation amid shifting global climates and the aftermath of extinctions; notable gaps occur in the record, attributed to taphonomic biases favoring marine over continental preservation. Recent discoveries, such as a diverse diapsid tooth assemblage from the Driefontein locality in (2023), reveal rapid post-extinction recovery with at least 81 diapsid specimens indicating varied feeding strategies among archosauromorphs and lepidosauromorphs. A 2025 study using on late stem reptiles further clarifies the stepwise assembly of crown reptile , positioning groups like Millerettidae as close relatives to Neodiapsida and refining the early diapsid phylogeny. Isotopic dating, including U-Pb analyses of volcanic tuffs interlayered with sediments, has confirmed these origins by precisely constraining the age of Formation deposits to 314.5 ± 0.7 million years ago, solidifying the Late as the cradle of diapsid evolution.

Key Transitional Forms

One of the earliest known basal diapsids is Araeoscelis, a lizard-like from the Early Permian of , dating to approximately 280 million years ago, characterized by a slender body and primitive diapsid skull features including two temporal fenestrae that distinguish it from more basal s. This exemplifies the initial diversification of diapsids, bridging parareptilian ancestors to more derived forms through its lightweight postcranial skeleton adapted for terrestrial locomotion. Araeoscelis is closely followed in the fossil record by Youngina, an early neodiapsid from the Late Permian of , which displays archosauromorph traits such as a narrowed supratemporal and robust quadrate bones, indicating a transitional position toward the line within diapsids. These features in Youngina highlight the of neodiapsid cranial architecture, where primitive diapsid fenestration coexists with specializations foreshadowing archosauromorph jaw mechanics. Aquatic adaptations among early diapsids are illustrated by Claudiosaurus from the Late Permian of , with its elongated body, flattened tail, and webbed feet bridging basal diapsids to more specialized marine reptiles like sauropterygians. As a neodiapsid, Claudiosaurus retained terrestrial traits such as functional limbs while evolving hydrodynamic modifications, underscoring the repeated invasions of aquatic niches by early diapsids. Gliding adaptations appear in the Late Permian Weigeltisaurus, a small weigeltisaurid from with elongated neural spines and supporting a for aerial , marking an early experiment in powered locomotion among diapsids. This structure, akin to modern , allowed Weigeltisaurus to traverse arboreal environments, transitioning diapsids toward volant capabilities seen in later pterosaurs. In the , Icarosaurus from extended this gliding trend, featuring hyper-elongated ribs that formed a wing-like membrane for controlled descent, representing a post-extinction persistence of patagial flight precursors in lepidosauromorph diapsids. These taxa collectively illustrate the diversification of locomotor strategies in diapsids during the Permian-Triassic boundary. The origins of turtles within diapsids are exemplified by Eunotosaurus from the Middle Permian of , which had reduced limbs and broadened ribs forming precursors to the , positioning it as a stem-turtle with transitional shell elements. This hypothesis was robustly supported by 2015 phylogenetic analyses integrating cranial and postcranial data, confirming Eunotosaurus as a critical link between basal diapsids and the . Diapsid survival through the Permian-Triassic mass extinction, which eliminated over 90% of tetrapod species, was facilitated by small, terrestrial forms like Prolacerta, an Early Triassic archosauromorph from South Africa and Antarctica with a lightweight build and insectivorous dentition suited to recovering ecosystems. These generalized, small-bodied diapsids repopulated niches post-extinction, enabling the radiation of major clades in the Triassic.

Phylogenetic Classification

Position Within Sauropsida

is defined as the monophyletic consisting of the last common ancestor of mesosaurs, turtles (Testudines), and diapsids, along with all of its descendants, encompassing all amniotes more closely related to extant reptiles and birds than to mammals. This originated during the early period, approximately 320 million years ago (Ma), shortly after the initial radiation of amniotes from amphibian-like ancestors. Sauropsids form the to Synapsida (the mammalian lineage) within Amniota, sharing key ancestral traits such as the amniotic egg, which enabled terrestrial reproduction independent of aquatic environments. Within , Diapsida represents a major derived subclade that arose from early sauropsid reptiles exhibiting anapsid-like conditions, such as those seen in basal forms like Captorhinus. Diapsids are primarily distinguished by the ancestral presence of two temporal e in the —the lower infratemporal and upper supratemporal openings—that facilitated muscle attachment and cranial lightness, contrasting with the single fenestra in synapsids or the absence in traditional anapsids. Over evolutionary time, this diapsid configuration underwent modifications, including fenestral loss or fusion in various lineages, but it remains the defining synapomorphy for the group. Recent phylogenetic analyses have further clarified diapsids' position by nesting traditionally anapsid-like parareptiles (e.g., millerettids, pareiasaurs, and procolophonids) within Diapsida, often as part of a clade termed Neoreptilia that includes these forms as sisters to crown-group diapsids (Neodiapsida). This integration challenges earlier views of parareptiles as a separate sauropsid branch and suggests that the diapsid condition evolved once from ancestors, with subsequent reductions in fenestration occurring independently. Molecular clock analyses, calibrated with constraints, estimate the initial sauropsid-synapsid divergence at around 317 Ma during the late , providing a temporal framework for diapsid origins shortly thereafter, near 310 Ma. These estimates align with evidence of early sauropsid trackways dating to approximately 359–354 Ma, indicating that the broader sauropsid preceded the consolidation of diapsid traits.

Major Clades and Relationships

The internal phylogeny of Diapsida is characterized by a core division within the subclade Neodiapsida, which splits into two major lineages: Lepidosauromorpha, encompassing , snakes, and , and , including crocodilians, dinosaurs, and birds. This bifurcation represents the foundational structure of modern reptile diversity, with Neodiapsida excluding more basal diapsid groups like . The inclusion of turtles (Testudines) as diapsids has been robustly confirmed by genomic studies from to 2015, which place them within as the to core archosaurs. These molecular analyses resolved long-standing morphological ambiguities, demonstrating that turtles derive from a diapsid despite secondary reductions in temporal fenestration. Fossil evidence supports this, with africanus from the Middle Permian identified as a stem-testudinate, exhibiting early shell-like features and positioning turtles deep within the diapsid tree.00678-3) Phylogenetic debates persist regarding the placement of certain early groups. For instance, the position of remains contentious, with a 2022 analysis by Simões et al. proposing them as stem-s outside crown Diapsida, challenging their traditional role as basal diapsids. Similarly, 2020 proposals, including those by Ford and Benson, suggest that —traditionally considered a separate —nests within Diapsida, implying multiple independent losses of temporal arches and a more nested evolutionary history for these "parareptiles." These revisions highlight ongoing uncertainties in basal diapsid relationships, driven by incomplete fossils and conflicting morphological datasets. Recent cladistic analyses provide a consensus tree for diapsid relationships, as synthesized by Jenkins et al. in 2025, which depicts crown-group reptiles emerging in the late with Millerettidae as the sister taxon to Neodiapsida. This tree emphasizes stepwise assembly of diapsid traits and strong support (bootstrap values >70%) for the major splits between Lepidosauromorpha and , as well as the inclusion of Testudines. However, uncertainty lingers for marine groups, such as ichthyosaurs, whose exact position on the diapsid stem remains unresolved despite their classification within Diapsida.

Diversity of Diapsid Groups

Lepidosauromorpha

Lepidosauromorpha represents a major clade within Diapsida, defined as all diapsid reptiles more closely related to and than to archosaurs, encompassing both extant and extinct lineages. The crown group, , includes the order —comprising lizards, snakes, and amphisbaenians with over 11,000 described species—and the order , represented today only by the (Sphenodon punctatus). This clade's diversity stems from adaptive radiations that have allowed it to exploit a wide array of terrestrial, arboreal, and subterranean environments, making lepidosauromorphs the most speciose group of non-avian reptiles. Key morphological traits distinguish Lepidosauromorpha, particularly in the and . The exhibits high kineticism through joints like streptostyly, enabling independent movement of the to facilitate prey capture and swallowing, a feature enhanced in squamates for their varied diets. Males of squamate possess hemipenes, paired, eversible reproductive structures that aid in . The body is covered in overlapping keratinous scales that provide protection and facilitate locomotion, with many undergoing periodic to renew the . dominates reproduction, though has evolved independently in several squamate lineages for environmental . The evolutionary origins of Lepidosauromorpha trace back to the Middle Permian, approximately 259 million years ago, with stem forms appearing amid the recovery from earlier extinctions. The crown group emerged and diversified during the , around 240–227 million years ago, coinciding with the breakup of and new ecological opportunities. Post- radiation accelerated in the and , marked by innovations such as limblessness in snakes, which likely evolved around 100 million years ago to enhance burrowing and foraging efficiency. Today, with nearly 12,000 extant , lepidosauromorphs fulfill critical ecological roles, from insectivory by amphisbaenians to arboreal predation by geckos and chameleons. Extinct diversity highlights the clade's early experimentation with form and function. Gliding adaptations appear in kuehneosaurids, such as Icarosaurus siefkeri from the (~228 million years ago), which featured elongated forming wing-like patagia for aerial locomotion among trees. Marine incursions are exemplified by thalattosaurs, reptiles (~252–201 million years ago) with elongated snouts and paddle-like limbs, whose phylogenetic placement within Diapsida remains debated, often as basal diapsids or early saurians, due to mosaic traits blending aquatic and terrestrial features. Recent 2024 analyses continue to refine their positions as early diapsid offshoots. These forms underscore the clade's adaptability before the dominance of modern squamates.

Archosauromorpha

represents a diverse and dominant of diapsid reptiles, encompassing all taxa more closely related to archosaurs than to lepidosaurs, with origins tracing back to the middle to late Permian period. This group includes stem archosauromorphs such as the proterosuchids, early Triassic carnivores known from and that exhibit primitive archosaur-like features in their skulls and limbs. Core members comprise crocodylomorphs, dinosaurs (including birds as avian dinosaurs), pterosaurs, and (Testudines), reflecting a broad radiation into terrestrial, aerial, and aquatic niches. Key diagnostic traits of , particularly in more derived forms, include modifications supporting an erect posture, such as improved hip and limb articulations that enhanced locomotor efficiency and endurance compared to the sprawling gait of earlier reptiles. In derived archosauromorphs, such as archosauriforms, a prominent cranial feature is the , an opening in the skull anterior to the eye socket that lightens the head and accommodates jaw musculature; this is a synapomorphy of and evident in fossils from the Late Permian onward. Additionally, lineages like birds and crocodilians possess a four-chambered heart, enabling complete separation of oxygenated and deoxygenated blood for more efficient circulation, a trait linked to their high metabolic demands. The evolutionary history of is marked by a significant radiation in the , following the end-Permian mass extinction that eliminated over 90% of terrestrial species and opened ecological opportunities. This diversification accelerated through the Era, with archosauromorphs achieving dominance on land, in the air, and in marine environments; dinosaurs alone account for over 1,000 described genera, spanning herbivores, carnivores, and omnivores of varying sizes from small theropods to massive sauropods. By the , advanced archosauromorphs had displaced earlier diapsid competitors, establishing a legacy of adaptive success that persisted until the end-Cretaceous extinction. Among extinct diversity, pterosaurs exemplify aerial innovation, with powered flight evolving around 228 million years ago in the , supported by elongated finger bones forming wing membranes and lightweight skeletons. Marine adaptations are represented by sauropterygians, a group of flipper-limbed reptiles that thrived in oceans but whose precise position within Diapsida remains debated, often as basal saurians or stem-archosauromorphs, with some analyses placing them near ichthyosaurs and thalattosaurs outside the core archosauromorph clades. Recent 2025 analyses continue to refine their positions with new fossils from the . In the modern biota, persists through two primary lineages: birds, with approximately 11,131 recognized species (as of June 2025) exhibiting extraordinary diversity in flight, song, and across every , and crocodilians, which serve as living fossils with body plans and cranial morphology largely conserved since the , reflecting a specialized ambush-predator niche that has endured mass extinctions.

References

  1. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/diapsid
  2. https://pmc.ncbi.nlm.nih.gov/articles/PMC3203498/
  3. https://ucmp.berkeley.edu/diapsids/
  4. https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2019.00013/full
  5. https://www.researchgate.net/publication/292321033_The_Origin_of_Temporal_Fenestrae
  6. https://onlinelibrary.wiley.com/doi/10.1111/brv.12751
  7. https://pdfs.semanticscholar.org/16a3/b24894481e84ece4284e8cec18eb3fb43fe2.pdf
  8. https://pmc.ncbi.nlm.nih.gov/articles/PMC10651123/
  9. https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.25371
  10. https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.25391
  11. https://www.stuartsumida.com/BIOL680/680Lecture6.pdf
  12. https://sjpp.springeropen.com/articles/10.1186/s13358-025-00351-y
  13. https://www.sciencedirect.com/topics/immunology-and-microbiology/diapsid
  14. https://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2007.00723.x
  15. https://pmc.ncbi.nlm.nih.gov/articles/PMC2100248/
  16. https://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2008.00783.x
  17. https://www.nature.com/articles/s41598-017-04514-x
  18. https://palaeo-electronica.org/2010_3/217/intro.htm
  19. https://pure-oai.bham.ac.uk/ws/portalfiles/portal/85507346/1.full.pdf
  20. https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24468
  21. https://www.science.org/doi/10.1126/science.196.4294.1091
  22. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0285111
  23. https://peercommunityjournal.org/articles/10.24072/pcjournal.620/
  24. https://www.lyellcollection.org/doi/10.1144/sp512-2021-5
  25. https://www.jstor.org/stable/4522965
  26. https://pmc.ncbi.nlm.nih.gov/articles/PMC4860341/
  27. https://onlinelibrary.wiley.com/doi/10.1002/spp2.1521
  28. https://ucmp.berkeley.edu/taxa/verts/archosaurs/basal_diapsids.php
  29. https://www.researchgate.net/publication/334968308_Permian_Aquatic_Reptiles
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC8141288/
  31. https://onlinelibrary.wiley.com/doi/10.1111/joa.70058
  32. https://onlinelibrary.wiley.com/doi/abs/10.1002/jez.b.22609
  33. https://www.nature.com/articles/s41598-018-36499-6
  34. https://onlinelibrary.wiley.com/doi/10.1111/pala.12130
  35. https://iucn-tftsg.org/wp-content/uploads/file/Articles/Laurin_and_Reisz_1995.pdf
  36. https://www.nature.com/articles/s41586-025-08884-5
  37. https://taxondiversity.fieldofscience.com/2011/06/neodiapsida.html
  38. https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1781143
  39. https://phys.org/news/2015-09-scientists-key-clues-turtle-evolution.html
  40. https://www.researchgate.net/publication/376223516_Halgaitosaurus_gregarius_a_New_Upper_Carboniferous_Araeoscelidian_Reptilia_Diapsida_from_the_Halgaito_Formation_Bears_Ears_National_Monument_Utah_USA
  41. https://paleo.peercommunityin.org/articles/rec?id=396
  42. https://www.researchgate.net/publication/225358273_The_Origin_Early_History_and_Diversification_of_Lepidosauromorph_Reptiles
  43. https://onlinelibrary.wiley.com/doi/10.1111/geb.13812
  44. https://www.nature.com/articles/s41586-025-09496-9
  45. https://pmc.ncbi.nlm.nih.gov/articles/PMC2688846/
  46. https://www.sciencedirect.com/topics/immunology-and-microbiology/lepidosaur
  47. https://royalsocietypublishing.org/doi/10.1098/rspb.2021.1084
  48. https://www.wienslab.com/Publications_files/Evolution_of_Limblessness.pdf
  49. https://www.palaeontologia.pan.pl/PP65/PP65_145-178.pdf
  50. https://sjpp.springeropen.com/articles/10.1186/s13358-024-00333-6
  51. https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-016-0761-6
  52. https://onlinelibrary.wiley.com/doi/10.1111/pala.12454
  53. https://ucmp.berkeley.edu/taxa/verts/archosaurs/archosauria.php
  54. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/archosaur
  55. https://royalsocietypublishing.org/doi/10.1098/rspb.2018.0361
  56. https://royalsocietypublishing.org/doi/10.1098/rstb.2015.0219
  57. https://www.reuters.com/science/scientists-clarify-origins-pterosaurs-dinosaur-eras-flying-reptiles-2020-12-09/
  58. https://elifesciences.org/articles/83163
  59. https://www.nature.com/articles/s42003-025-08911-1
  60. https://ebird.org/news/avilist-a-unified-global-checklist-of-the-worlds-birds-is-now-available
  61. https://pmc.ncbi.nlm.nih.gov/articles/PMC8277476/
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