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Postcranial skeletal pneumaticity (PSP), a system of skeletal air sacs, occurred in three Cretaceous clades, including pterosaurs (e.g., Pteranodon); past studies have hypothesized that the trait was homologous (originating from a shared ancestor). With this in mind, Tito Aureliano et al. examined fossils of common ancestors of the clades using microtomography, finding openings in bones-a possible indicator of PSP-but of sizes inconsistent with PSP. The team reported other findings contradicting the homology hypothesis as well, concluding that PSP likely evolved independently in each clade.

Aureliano et al. found openings in bones in fossils of common ancestors of pterosaurs and two other Cretaceous clades, but the team determined that the sizes of the openings were too varied to be indicative of PSP, thereby weakening the homology hypothesis.

Although past studies by paleontologists concluded that PSP in pterosaurs and two other Cretaceous clades was likely attributable to a common ancestor, those paleontologists lacked access to technology that led Aureliano et al. to reach a different conclusion.

Previous studies hypothesized that PSP originated in a shared ancestor of pterosaurs and two other clades, but the findings of Aureliano et al. suggest that PSP evolved independently in pterosaurs and was subsequently inherited by the other two clades.

Aureliano et al. found that pterosaurs and two other Cretaceous clades with PSP likely lacked a common ancestor with the trait, leading the team to posit a different evolutionary origin for PSP than that posited in earlier studies.