In 2002 Dave Varricchio named Piksi barbarulna, based on limb bones found in the Upper Cretaceous Two Medicine Formation on the Blackfoot Reservation in Montana. Varricchio initially thought that Piksi was a bird, but a 2012 reevaluation of the specimen by Federico Agnolin and Varricchio concluded that Piksi is actually a pterosaur. The genus name, Piksi, comes from the Blackfoot language and means “large bird.” The species name, barbarulna, is derived from Latin, and translates to “strange elbow.”
The only known specimen is made up of a distal right humerus, portions of the right ulna, and the proximal end of the right radius. In their 2012 reevaluation, Agnolin and Varricchio noted that the fragmentary specimen had several features found only in pterosaurs and not birds.
Piksi and pterosaurs have distinctive joint surfaces on their distal humeri not present in birds. They also share a broad but shallow triangular brachial depression on the distal end of the humerus. In birds, when present, the brachial depression is elliptical and sharply delimited. Finally, it bears a wide and deep olecranon fossa not delimited dorsally by a ridge. Furthermore, Agnolin and Varricchio found Piksi to be a short-tailed pterodactyloid because the distal condyles of its humerus are anteriorly directed, and the distal ulna was transversely widened.
Conversely, in 2016 Elizabeth Martin-Silverstone and colleagues doubted the pterosaurian nature of Piksi. They noted several features found in Piksi and no other pterosaur, some of which are found in theropods.
In 2018 however, Nick Longrich and colleagues found Piksi to be a basal ornithocheiroid, with a ghost lineage of approximately 75 million years. He thought it might be an example of a hitherto unknown lineage of small pterosaurs.
Piksi was found in deposits formed at the bottom of a pond or ephemeral lake in a temperate or subtropical upland forest. It lived alongside the medium-sized azhdarchoid Montanazhdarcho, and the famous dinosaurs Maiasaura, Orodromeus, and Troodon.
Because Piksi is so poorly known and it may be a member of a long-lived ghost lineage, we have reconstructed Piksi as a small ornithocheroid similar to what we imagine as the common ancestor of the ornithocheroids.
