| Pterosauromorphs | |
|---|---|
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| Skeletal restoration ofLagerpeton chanarensis (known elements represented in white) | |
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| Skeletal restoration ofDimorphodon macronyx | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Ornithodira |
| Clade: | †Pterosauromorpha Kuhn-Schnyder & Rieber, 1986 |
| Subgroups | |
Pterosauromorpha (meaning "pterosaur-like forms") is one of the two basic divisions ofOrnithodira that includespterosaurs and alltaxa that are closer to them than todinosaurs and their close relatives (i.e.Dinosauromorpha).[2][3] In addition to pterosaurs, Pterosauromorpha also includes thebasalcladeLagerpetidae and some otherLate Triassic ornithodirans (such asScleromochlus).[4][5][6][7]
The name Pterosauromorpha was originally coined by Emil Kuhn-Schnyder and Hans Rieber (1986) for areptilian subclass distinct fromArchosauria which includes pterosaurs.[8] In 1997,Kevin Padian classified Pterosauromorpha as a clade of archosaurs and proposedphylogenetic definition for this group: "Pterosauria and all ornithodiran archosaurs closer to them than to dinosaurs".[2] Brian Andres and Kevin Padian redefined Pterosauromorpha as: "The clade consisting ofPterodactylus (originallyOrnithocephalus)antiquus (Sömmerring 1812) (Pterosauria) and all organisms or species that share a more recentcommon ancestor with it than withAlligator (originallyCrocodilus)mississippiensis (Daudin 1802) (Suchia) andCompsognathus longipes Wagner 1859 (Dinosauromorpha)".[3][9]
Lagerpetidae was traditionally considered the earliest diverging group of dinosauromorphs. This caused no other reptiles besides the true pterosaurs to be placed in Pterosauromorpha.[10][11] The only notable exception was a small reptile namedScleromochlus, whose placement within the clade itself remained controversial due the poor preservation of its otherwise completeremains. Differentphylogenetic analyses found it as a basal pterosauromorph,[4][5] a non-aphanosaurian, non-pterosaur basal avemetatarsalian, a basal dinosauromorph,[11] or a basalarchosauriform.[12] This has resulted in a large gap between the fullyaerial pterosaurs and theirterrestrial ancestors, as the earliest pterosaurs were already capable flyers.[11]
First iteration of phylogenetic analysis produced by Kammerer et al. (2020) restored lagerpetids as a basal dinosauromorphs, which corresponds to the traditional point of view. But the second iteration, in which were addedScleromochlus, found Lagerpetidae as the most basal pterosauromorphs, andScleromochlus as thesister taxon of pterosaurs.[4] In a study that usedmicro-CT scans, Ezcurra et al. (2020) have found additional similarities, including largesemicircular canals within the bones of some lagerpetids that resemble that of pterosaurs. It is assumed that large semicircular canals are related toarboreal, aerial or other agile forms of terrestrial locomotion as well as rapid movements. Theflocculus, the part of the brain that aids in transmitting information, was also large in both pterosaurs and lagerpetids, though to a lesser extent. When Ezcurra et al. (2020) includedScleromochlus in their analysis, they found it to be the most basal pterosauromorph, sister to a clade including lagerpetids and pterosaurs.[5] Baron (2021) conducted his own analysis, which confirmed the relationship between lagerpetids and pterosaurs.[6]
It has to do with the semicircular canals [in the ear], which orients you in 3D space. The shape of those canals correlates with ecology and how you move your head — basically, are you agile or not? And a lot of things that have flight have semicircular canals with a really large and characteristic [shape] because you're flying, you're in a lot more 3D space.
Kellner et al. (2022) describedMaehary, a small archosaur from the Late Triassic ofBrazil. Along with lagerpetids, it was interpreted as a basal pterosauromorph. It is noteworthy that leftmaxilla ofMaehary was previously considered to be a specimen ofFaxinalipterus that was re-classified as a lagerpetid.[7] Contrary to the initial classification, phylogenetic analyses conducted by Müller et al. (2023) and Müller (2024) recoveredMaehary as agracilisuchidpseudosuchian rather than a pterosauromorph.[14][15] In their study onScleromochlus, Foffa et al. (2023) noted that the phylogenetic position ofMaehary remains uncertain due to the fragmentary nature of its material.[16]
Nesbitt et al. (2011)[10]
| Ezcurra et al. (2020)[5]
| Kellner et al. (2022)[7]
|
An analysis by Garcia & Müller (2025) found lagerpetids asparaphyletic to pterosaurs, andFaxinalipterus not as a pterosauromorph but as asister taxon to Ornithodira, more closely related to ornithodirans than toMambachiton andAphanosauria.[17]
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