Fossil Friday #5 - Sharovipteryx

The Mesozoic era is best known for being the time that the dinosaurs dominated the earth. It began 252 million years ago after the Permian extinction had killed 95% of all life on earth. The early Triassic era was therefore a time on earth that allowed many groups of animals to diversify and experiment, as there were niches to be filled that were not previously available. The most famous example of this is the beginning of the Dinosauria clade, which would become one of the most successful groups of animals to ever walk the earth.

Away from Archosaurs, other reptile groups were also rapidly evolving, trying and ultimately failing to be the most successful group of animals on earth during the Mesozoic. One great example of this is one of the first known vertebrates to evolve wing membranes, the Sharovipteryx mirabilis. Only one known specimen has been found of this curious reptile, however, this highlights just how much we can find out given how limited the fossil record can be. The 225 million-year-old specimen comes from the Late Triassic Maydgen Formation of Kyrgyzstan, one of the richest fossil beds in central Asia, and was named in 1971 by Soviet palaeontologist, Aleksander Sharov. Its genus was first given the name Podopteryx, however, this already belonged to a genus of damselfly. It wasn't until 1981 that it was renamed Sharovipteryx, meaning Sharov's wing, paying homage to the scientist who originally discovered it (Cowen, 1981).

 

    S. mirabilis fossil, the only known one to date.           S. mirabilis reconstruction.

It is always difficult to classify an extinct animal given limited resources. Sharovipteryx has been classified under Protosauria, a group of Archosauromorpha. This means they are thought to be phylogenetically related to other curiously looking Triassic reptiles such as Ozimek volans (Dzik and Sulej, 2016) and the tree-dwelling Drepanosaurus unguicaudatus (Renesto et al, 2009).

What makes Sharovipteryx unique when compared to other winged vertebrates from this time, is that its wing membranes were located on its legs. This is an example of a unique evolutionary trait, something which is seen most often after a recent extinction event. This would have allowed the animal to glide between trees, meaning it probably lived in forested areas, but may not have been able to achieve powered flight (Dyke et al, 2006; Gans et al, 1987). This proved to ultimately be an unsuccessful model, as the three vertebrate groups to achieve powered flight; pterosaurs, birds, and bats, all have their wing membranes attached to their forelimbs and have been able to diversify and spread across the world with this design.

I have heard unsuccessful and unconventional groups of animals, like Sharovipteryx be dubbed "One of nature's mistakes". I believe that this couldn't be more wrong. Evolution doesn't have a plan or an end goal, species adapt to try and fill a niche to overcome their competitors. Naturally, this will lead to some species being out-competed by others that are more suited to a certain environment at a specific time. This doesn't make them a mistake, they are just as much an important part of the earth's incredibly diverse history of life as any other species. Imagine how boring palaeontology would be if we didn't have these wonderful animals like Sharovipteryx, as we are unlikely to ever see anything like it ever again.

References

Cowen, R. (1981). "Homonyms of Podopteryx". Journal of Paleontology. 55 (2): 483.

Dyke G.J., Nudds, R.L. and Rayner, J.M. (2006) “Flight of Sharovipteryx mirabilis: The world's first delta-winged glider,” Journal of Evolutionary Biology, 19(4), pp. 1040–1043.

Dzik, J. and Sulej, T. (2016). An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages" Acta Palaeontologica Polonica. 61 (4): 805–823.

Gans, C., Darevski, I. and Tatarinov, L.P. (1987) “Sharovipteryx, a reptilian glider?,” Paleobiology, 13(4), pp. 415–426. 

Renesto, S.C., Spielmann, J.A. and Lucas, S.G. (2009) “The oldest record of drepanosaurids (Reptilia, Diapsida) from the late triassic (Adamanian Placerias Quarry, Arizona, USA) and the stratigraphic range of the Drepanosauridae,” Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 252(3), pp. 315–325.