Ausia fenestrata

Interpretations

• G. Hahn and H. D. Pflug suggested that Ausia is a pennatulacean coral from the family Veretillidae, but there are no signs of secondary polyps on the fossil, which are nonetheless represented in Hahn and Pflug's reconstruction.
• Some researchers have assumed that these depressions are pores and interpreted Ausia as an ancestor of archeocyathans and other sponge-like organisms or true sponge. But Adolf Seilacher has argued that the "windows" are merely dimples.
• Ausia may represent ascidians (sea squirts), an invertebrate group related to the chordates. Results of a new study of a Burykhia from Russia have shown a possible affinity of these organisms to the ascidians, which are urochordates. The Russian species is more than 90 mm across, and the rows of oval depressions are separated by structures which were probably grooves in the internal wall surface of the living organism. The study's authors interpret these fossils as the internal sand casts of a vast bag-like cavity, possibly a pharynx or branchial basket. The animals represented by these two genera were thought to live in the shallow waters of an epicontinental sea, slightly more than 555-548 million years ago, and the authors feel this is probably the oldest evidence of the chordate lineage of metazoans.
• Jerzy Dzik has suggested that Ausia bears some similarity to the halkieriids, and resembles the body plan that might be expected of halkieriid ancestors under the coeloscleritophoran hypothesis.

Ausia3.jpg|Hahn and Pflug reconstruction of Ausia as a pennatulacean Ausia fenestra.jpg|Reconstructed as a tunicate

References

References

1. (December 2021). "New Ediacaran fossils from the Ukraine, some with a putative tunicate relationship". PalZ.
2. "IGCP 493 Annual Report 2003".
3. M. A. Fedonkin (1996). "Ausia as an ancestor of archeocyathans, and other sponge-like organisms". In: ''Enigmatic Organisms in Phylogeny and Evolution. Abstracts''. Moscow, Paleontological Institute, Russian Academy of Sciences, p. 90-91.
4. Mark A. S. McMenamin (1998). "The Sand Menagerie". In: ''The Garden of Ediacara: Discovering the First Complex Life''. Columbia University Press. New York. pp.11-46.
5. (2012). "A new metazoan from the Vendian of the White Sea, Russia, with possible affinities to the ascidians". Paleontological Journal.
6. Vickers-Rich P. (2007). "Chapter 4. The Nama Fauna of Southern Africa". In: Fedonkin M.A., Gehling J.G., Grey K., Narbonne G.M., Vickers-Rich P. ''The Rise of Animals: Evolution and Diversification of the Kingdom Animalia'', Johns Hopkins University Press. pp. 69-87
7. M.A. Fedonkin, P. Vickers Rich, B. Swalla, P. Trusler, M. Hall. (2008). "A Neoproterozoic chordate with possible affinity to the ascidians: New fossil evidence from the Vendian of the White Sea, Russia and its evolutionary and ecological implications". HPF-07 Rise and fall of the Ediacaran (Vendian) biota. International Geological Congress - Oslo 2008.
8. {{walcott 2009. dzik
9. Dzik, J.. (2011). "Possible Ediacaran ancestry of the halkieriids". Palaeontographica Canadiana.