Just reviewing some old posts, I noticed an autapomorphy in my tracings of the elbow of Megalancosaurus. What I thought was a suture that shortened the ulna relative to the radius was in reality a break (also noted by S. Renesto who sent me some other closeups to support his observation, see below) and the two bones were actually similar in length, as in sister taxa. Here I correct that error and recover a more crescent-shaped sesamoid, more like the giant sesamoid in Drepanosaurus, plus lots of little broken bones that would have represented the ulnar crest.
Other specimens of this genus also demonstrate a sesamoid present at the elbow of Megalancosaurus.
These are further data supporting the hypothesis that the odd bone at the elbow of Drepanosaurus was a sesamoid, not the ulna, as Renesto (1994) proposed, nor the coracoid, as Pinna (1980) proposed.
Note, I have not seen the specimens close up, but have relied on photographs using DGS, digital graphic segregation. That’s not an excuse. That’s further support for the method.
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.
Calzavara M, Muscio G and Wild R 1980. Megalancosaurus preonensis n. gen. n. sp., a new reptile from the Norian of Friuli. Gortania 2: 59-64.
Feduccia A and Wild R 1993. Birdlike characters in the Triassic archosaur Megalancosaurus. Natur Wissenschaften 80:564–566.
Geist NR and Feduccia A 2000. Gravity-defying Behaviors: Identifying Models for Protoaves. American Zoologist 4):664-675. online pdf
Pinna G 1980. Drepanosaurus unguicaudatus, nuovo genere e nuova specie di Lepidosauro del trias alpino. atti Soc. It. Sc.Nat. 121:181-192.
Pinna G 1986. On Drepanosaurus unguicaudatus, an upper Triassic lepidosaurian from the Italian Alps. Journal of Paleontology 50(5):1127-1132.
Renesto S 1994. Megalancosaurus, a possibly arboreal archosauromorph (Reptilia) from the Upper Triassic of Northern Italy. Journal of Vertebrate Paleontology 14(1):38-52.
Renesto S 1994. The shoulder girdle and anterior limb of Drepanosaurus unguicaudatus(Reptilia, Neodiapsida) from the upper Triassic (Norian of Northern Italy. Zoological Journal of the Linnean Society 111(3):247-264
Renesto S 2000. Bird-like head on a chameleon body: new specimens of the enigmatic diapsid reptile Megalancosaurus from the Late Triassic of Northern Italy. Rivista Italiana di Paleontologia e Stratigrafia 106: 157–179.