We looked at Sharovipteryx earlier here, here and here. Today we’l take an overall look at the plate and counter plate with a fresh tracing that reveals new, previously overlooked details, some of which are so buried they are best discovered by way of phylogenetic bracketing.
The sister taxa of Sharovipteryx have dorsal plumes. These taxa include Cosesaurus, Kyrgyzsaurus and famously, Longisquama (Fig. 2). Dorsal plumes have never been observed in Sharovipteryx, largely because no one has looked for them and, just as importantly, they are small and hard to see because they overlap easier-to-see soft tissue. Here the plumes are best seen in the enlargement and are labeled ‘DP.’ These online images are greatly reduced from the data I was able to work from, so they may be difficult to see at web resolution (Fig. 3). If anyone is interested in seeing higher resolution images, email me.
Sister taxa to Sharovipteryx also had a prepubis. This bone is essentially invisible in Sharovipteryx, but if it exists, as phylogenetic bracketing indicates, it is buried beneath the right hand, which is back by the pelvis where the prepubis articulates.
At this size and shape
the prepubis of Sharovipteryx is proportioned relative to the femur more similar to the same bone in Longisquama and pterosaurs. The prepubis essentially extends new bone ventral to the pelvis to anchor femoral muscles of adduction.
If you want to know the maximum size for a Sharovipteryx egg, you can estimate a minor axis diameter measurement from the pelvic opening. Then figure out the appropriate size of the hatchling (Fig. 2). Note the pelvic opening of Sharovipteryx is much deeper than that of Cosesaurus, but not as deep as in MPUM 6009, a basal pterosaur. Apparently fewer larger eggs were laid by more derived fenestrasaurs, but MPUM 6009 had the deepest pelvic opening of any pterosaur.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Sharov AG 1971. New flying reptiles from the Mesozoic of Kazakhstan and Kirghizia. – Transactions of the Paleontological Institute, Akademia Nauk, USSR, Moscow, 130: 104–113 [in Russian].
Tatarinov LP 1989. [The systematic position and way of life of the problematic Upper Triassic reptile Sharovipteryx mirabilis.] Paleo. Zh. 1989(2): 110-112. [in Russian].
Tatarinov LP 1994. Terestrial vertebrates from the Triassic of the USSR with comments on the morphology of some reptiles. In: Mazin J.-M. & Pinna G. (Eds.) Evolution, ecology and biogeography of the Triassic reptiles. Paleo. Lomb. New Ser. 2.
Unwin DM, Alifanov VR and Benton MJ 2000. Enigmatic small reptiles from the Middle-Late Triassic of Kyrgyzstan. In: Benton M.J., Shishkin M.A. & Unwin D.M. (Eds) The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge U. Press: 177-186.