Sharovipteryx dorsal plumes

Figure 1. Sharovipteryx in situ. Click to enlarge. Here both plate and counter plate are shown along with a tracing based on both.

Figure 1. Sharovipteryx in situ. Click to enlarge. Here both plate and counter plate are shown along with a tracing based on both. Note the large area missing from the plate. The specimen is virtually complete and articulated. Some beetles dot the matrix. Look closely and you’ll see where the hands are. The uropatagia (they are separate) and other soft tissue membranes are easy to see.

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.

Dorsal plumes
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.

Figure 2. The basal fenestrasaur precursors of pterosaurs, including Cosesaurus, Sharovipteryx, Kyrgyzsaurus, Longisquama and a basal pterosaur.

Figure 2. The basal fenestrasaur precursors of pterosaurs, including Cosesaurus, Sharovipteryx, Kyrgyzsaurus, Longisquama and a basal pterosaur. Click to enlarge. All basal fenestrasaurs had a lepidosaurian dorsal frill, sometimes enlarged to plumes, derived from the frill in Huehuecuetzpalli and other basal lepidosaurs.

The Prepubis
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.

Figure 3. Sharovipteryx (Pp) prepubis possible location beneath the right fingers. The dorsal plumes (DP) are easier to see.

Figure 3. Click to enlarge. Sharovipteryx (Pp) prepubis possible location and shape – beneath – the right fingers and associated soft tissue. The coincidence is suspect (note the shape matches) but phylogenetic analysis provides Sharovipteryx with a prepubis of this size and shape. The dorsal plumes (DP) are easier to see. Numbers are fingers 1-4. Soft tissue covers most of the view here, blanketing other elements. The tracing shows more detail because it was traced from both plates, not just this one. Note the left ischium is likewise buried beneath the left uropatagium, revealed only like a child beneath a blanket. I’m sure no one would deny that Sharovipteryx had an ischium and fingers. The same must be said of a prepubis and dorsal plumes by phylogenetic bracketing.

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.

Pelvic opening
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.

References
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. LombNew 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.

wiki/Sharovipteryx

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