Faxinalipterus minima (Bonaparte 2010) has been described from bits and pieces of a sparrow-sized archosaur. The holotype consists of short robust arm bones and much longer leg bones. A displaced maxilla with a large antorbital fenestra and narrow fossa is also referred to the specimen.
Wiki writes, “The describers have assigned Faxinalipterus to the Pterosauria, based on its long hollow limbs and saddle-shaped upper joint of the relatively short and robust humerus, suitable to perform a wing stroke. They see it as perhaps the oldest pterosaur known, as it possibly predates European finds from the Norian. That the possible age difference cannot be large, they see as an indication of rapid evolution in early pterosaurs. Because the Caturrita Formation consists of terrestrial sandstones, that evolution would have had its origins in a terrestrial, not coastal, habitat. They also concluded Faxinalipterus is the most basal known pterosaur, basal features including a lack of fusion between tibia and fibula, a thin radius and a coracoid that has not fused to the scapula. However, Alexander Kellner has suggested Faxinalipterus might be not be a pterosaur but a basal member of the Pterosauromorpha instead or, if the lack of fusion between tibia and fibula is plesiomorphic, even a sister taxon of the Ornithodira.”
This is going to get some people excited, others not
The maxilla assigned to Faxinalipterus (and I don’t doubt the assignment) has a large squarish antorbital fenestra surrounded by a narrow fossa. No pterosaur has a fossa. Basal pterosaurs always have an angled maxillary ascending process. Basal pterosaurs also have a much more slender fibula. And there are several other mismatches despite the few bones representing the animal. The putative coracoid is more likely a pubis or ischium.
The best match I found (not via phylogenetic analysis) is with Scleromochlus (Fig. 1) a basal bipedal crocodylomorph. Virtually every aspect of Faxinalipterus seems to be a good match, including chronological age and overall size, other than relative limb length. Faxinalipterus is just more primitive in having shorter hind limbs and more robust front limbs. Check out the distal tibia and fibula. A close match to bipedal crocs. Nothing like pterosaurs.
Since every discovery can be discovered only once
it’s only human nature that a paleontologist finding a partial skeleton would jump on the most exciting possibility, like “the most primitive known pterosaur.” Unfortunately you also have to play by the rules and compare the new specimen to every other taxon sharing a majority of its traits (even if incomplete) and you have to go with the recovered results.
On the other hand…
Faxinalipterus does offer insight into the origin of Scleromochlus and basal crocs, and by extension, basal archosaurs. I’d like to see thefolks toying with Lagerpeton (a convergent biped close to Tropidosuchus) drop it in favor of these two croc bipeds at the base of the archosaur family trees.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Bonaparte JF, Schultz CL and Soares MB 2010. Pterosauria from the Late Triassic of southern Brazil. In S. Bandyopadhyay (ed.), New Aspects of Mesozoic Biodiversity, Lecture Notes in Earth Sciences 132:63-71.