Biology:Orbisiana

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Orbisiana is an enigmatic extinct organism from the Ediacaran, and is made up of agglutinated spherical or hemispherical chambers. Recent studies have suggested and supported an affinity with Palaeopascichnus, and other similar organisms from the Ediacaran.

Discovery

The holotype fossil of Orbisiana was found in the Soligalich 7 core, which was collected from the Lower Member of the Gavrilov Yam Formation in Ladoga, Western Russia sometime during the 1960s, and was formally described and named in 1976.[1][2]

Description

Orbisiana is an agglutinating organism, consisting of spherical to hemispherical chambers arranged in long strings or clustered aggregates with an irregular outline. The chambers themselves are commonly found getting up to 0.2–2.6 mm (0.01–0.10 in) in diameter, and in all known specimens, the walls of the chambers are composed of a carbonaceous material, and are in-filled with sediment that is similar, or the same, as the matrix rock outside the fossils.[3][4][2] The overall body can be composed of 4 to 150 uniform chambers reaching up to 70 mm (2.8 in) in length, with some specimens showing dichotomous branching, although this is noted to be uncommon.[4][2]

Palaeoecology

Specimens of Orbisiana are commonly preserved as two to three-dimensional compressions in the rock, with the walls being either carbonaceous or pyritic in composition.[4][1] From this, with 3D scanning of three-dimensional specimens, it was found that the chambers are straight cylinders, which are open at either end. This suggested that the walls of Orbisiana are partly rigid, as well as possibly being partially embedded into the sediment, meaning that Orbisiana was an benthic organism that lived either on top of or partially buried in sediments.[4] A prior study also noted that Orbisiana likely favoured calm and well aerated shallow marine waters.[5]

A later study done in 2018 found that the chambers of Orbisiana are not open ended, and may instead be a result of the local taphonomy, although is still regarded as a benthic organism. The study suggested that the walls may have been made up of clay grains in life, which were "glued" together to form said chambers, and as such would have easily collapsed during burial.[2]

Affinities

Since it was discovered, Orbisiana has been suggested to be a number of things. When originally described in 1976, it was interpreted to be a aggregate of large cells,[1] although in 1984 two studies had been published, with one interpreting Orbisiana to be fecal pellets,[6] and the other suggesting it to be an acritarch.[7] Later, in 1992 and 1994, it was further reinterpreted as an algae.[8][9]

But, in 2014 when the Lantian forms were properly described, it was noted that their general morphology discounts any of these prior interpretations, and is instead regarded as problematica until further evidence is found,[4] although it was also noted that Orbisiana bears morphological similarities with other agglutinating organisms, such as Palaeopascichnus,[3] and was also placed into the proposed group Palaeopascichnida in the same year.[10] These probable affinities with the palaeopascichnids has been further supported after the rediscovery of the previously lost holotype specimen, although the Lantian forms[2]

Taxonomy and Distribution

Orbisiana contains three valid species which are restricted to Asia, and one now synonmyised species, which are as follows:

  • † O. simplex Sokolov, 1976 - Known from across the White Sea area in Russia,[3][11][12][10] as well as Eastern Siberia.[13]
  • † O. spumea Kolesnikov et al., 2022 - Known from the Ustʹ Pinega Formation, Russia.[14]
  • † O. intorta Kolesnikov et al., 2022 - Known from across the White Sea area in Russia.[14]
  • † O. linearis Chen, 1994 - Known from the middle Ediacaran Lantian Formation, Anhui Province, South China.[4] Later studies moved the species into Palaeopascichnus.[2]

Specimens which are unattributed to either species have also been found in the Dongpo Formation in Central China,[15], as well as probable occurrences in the Rocky Harbour Formation in Canada.[16]

See also

References

  1. ↑ 1.0 1.1 1.2 Sokolov, B. S. (1976). "Organicheskii mir Zemli na puti k fanerozoiskoi differentsiatsii". Vestnik Akademii Nauk SSR 1: 126–143. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Kolesnikov, Anton V.; Liu, Alexander G.; Danelian, Taniel; Grazhdankin, Dmitriy V. (October 2018). "A reassessment of the problematic Ediacaran genus Orbisiana Sokolov 1976". Precambrian Research 316: 197–205. doi:10.1016/j.precamres.2018.08.011. 
  3. ↑ 3.0 3.1 3.2 Jensen, Sören (2003). "The Proterozoic and Earliest Cambrian Trace Fossil Record; Patterns, Problems and Perspectives". Integrative and Comparative Biology 43 (1): 219–228. doi:10.1093/icb/43.1.219. ISSN 1540-7063. PMID 21680425. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Wan, Bin; Xiao, Shuhai; Yuan, Xunlai; Chen, Zhe; Pang, Ke; Tang, Qing; Guan, Chengguo; Maisano, Jessica A. (2014). "Orbisiana linearis from the early Ediacaran Lantian Formation of South China and its taphonomic and ecological implications". Precambrian Research 255: 266–275. doi:10.1016/j.precamres.2014.09.028. Bibcode: 2014PreR..255..266W. 
  5. ↑ Fedonkin, M. A.; Simonetta, A.; Ivantsov, A. Y. (2007). "New data on Kimberella, the Vendian mollusc-like organism (White Sea region, Russia): palaeoecological and evolutionary implications". Geological Society, London, Special Publications 286 (1): 157–179. doi:10.1144/sp286.12. Bibcode: 2007GSLSP.286..157F. 
  6. ↑ Chistyakov, B.G.; Kalmykova, N.A.; Nesov, L.A.; Suslov, G.A. (1984). "O nalichii vendskikh otlozhenij v srednem techenii r Onegi i vozmozhnom syshchestvovanii obolochnikov (Tunicata: Chordata) v dokembrii". Vestnik of the Leningrad State University 6: 11–19. 
  7. ↑ Sokolov, Boris S.; Fedonkin, Mikhail A. (1 March 1984). "The Vendian as the Terminal System of the Precambrian". Episodes 7 (1): 12–19. doi:10.18814/epiiugs/1984/v7i1/004. 
  8. ↑ Yan, Y.; Jiang, C.; Zhang, S.; Du, S.; Bi, Y.. "Research of the Sinian System in the region of western Zhejiang, northern Jiangxi, and southern Anhui provinces". Bulletin of the Nanjing Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences 12: 1–105. 
  9. ↑ Chen, M.; Lu, G.; Xiao, Z.. "Preliminary study on the algal macrofossils – Lantian Flora from the Lantian Formation of Upper Sinian in southern Anhui". Bulletin Institute of Geology, Academia Sinica 7: 252–267. 
  10. ↑ 10.0 10.1 Grazhdankin, Dmitriy (March 2014). "Patterns of Evolution of the Ediacaran Soft-Bodied Biota". Journal of Paleontology 88 (2): 269–283. doi:10.1666/13-072. 
  11. ↑ Grazhdankin, D.Z.; Maslov, A.V.; Krupenin, M.T.; Ronkin, Y.L. (2010). "Osadochnye Sistemy Sylvitskoi Serii: Verkhnii Vend Srednego Urala". Ekaterinburg: 280. 
  12. ↑ Grazhdankin, D.Z. (2012). "Upper Vendian Chronostratigraphy, Trofimuk Institute of Petroleum Geology and Geophysics". Novosibirsk: 34. 
  13. ↑ Ivantsov, A. Yu. (February 2017). "Finds of Ediacaran-type fossils in Vendian deposits of the Yudoma Group, Eastern Siberia". Doklady Earth Sciences 472 (2): 143–146. doi:10.1134/S1028334X17020131. 
  14. ↑ 14.0 14.1 Kolesnikov, Anton; Desiatkin, Vladislav (July 2022). "Taxonomy and palaeoenvironmental distribution of palaeopascichnids". Geological Magazine 159 (7): 1175–1191. doi:10.1017/S0016756822000437. 
  15. ↑ Wang, Xin; Zhang, Xingliang; Dai, Tao; Liu, Wei; Zhang, Yuan; Li, Luoyang (March 2026). "New occurrence of a postglacial Ediacaran macrofossil assemblage from North China and its evolutionary implication". Precambrian Research 434. doi:10.1016/j.precamres.2025.107992. 
  16. ↑ Liu, Alexander G.; Tindal, Benjamin H. (April 2021). "Ediacaran macrofossils prior to the ~580 Ma Gaskiers glaciation in Newfoundland, Canada". Lethaia 54 (2): 260–270. doi:10.1111/let.12401. 

Wikidata ☰ Q49000214 entry



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