Vendiamorpha

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Vendiamorpha
Temporal range: Late Ediacaran, between 567–550  Ma
Vendia rachiata.JPG
Paravendia janae, Vendia sokolovi,
V. rachiata
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum:† Proarticulata
Class:† Vendiamorpha
Fedonkin, 1985
Families and genera

Vendiamorpha [1] is a class of extinct animals within the Ediacaran phylum Proarticulata.

Contents

The typical vendiamorph had an oval-shaped or round-shaped body divided completely into segmented isomers, that were arranged alternately in two rows with reference to the longitudinal axis of the body.

Description

Karakhtia Karakhtia nessovi.jpg
Karakhtia

The phenomenon of left-right alternating segments is called glide reflection symmetry, and is a diagnostic feature of proarticulates. Transverse elements decrease in size from one end to the other and are inclined in the same direction. [2] [3] Typically, the first few, or largest initial isomers are fused together to form a headshield-like structure, leading some researchers to have originally considered them to be ancestral or related to arthropods, [4] [5] though, overwhelming evidence of them being proarticulates have since led researchers to discard this hypothetical relationship. [1] [2]

Some vendiamorphs (e.g., Vendia and Paravendia) supposedly demonstrate a digestive-distributive system consisting of a simple axial tube and lateral appendages, with one lateral appendage corresponding to one isomer. [2] [3] The tentative vendiamorph Karakhatia is unique from the other members, as well as all proarticulates, in the fact that is has been noted to bearing 'coarse radial folds' around its outer margin, which has given it a noticeably frilly appearance, has been likened to what is seen in material of Haootia . [6] [7]

Taxonomy

Vendiamorpha currently contains the singular Family Vendiidae (Originally Vendomiidae, derived from Vedomia, which was later synonymised into Dickinsonia. [8] ):

Vendiidae

Due to the crumpled nature of most Karakhtia specimens and the aforementioned presence of coarse radial folds, the placement of it within Vendiamorpha, and Proarticulata itself, is tentative. [6]

Distribution

All members of Vendiamorpha are restricted to the Ust' Pinega Formation of Syuzma and Onega Rivers in Arkhangelsk Oblast, northwestern Russia. [9] [10] [3]

Name

The clade name Pseudovendia refers to the resemblances to a fossil imprint described as Vendia sokolovi. Originally, that fossil was interpreted as an arthropod, [11] later as a proarticulatan, [1] then conjectured as possibly a frond-like organism. [12]

Current scientific consensus now recognizes the poorly preserved holotype of Pseudovendia as a pseudofossil. [13] [14]

See also

References

  1. 1 2 3 Fedonkin, M.A. (1985). "Systematic description of Vendian metazoa". In Sokolov, B.S.; Iwanowski, A.B. (eds.). Vendian System: Historical–Geological and Paleontological Foundation. Vol. 1: Paleontology. Moscow, RU: Nauka. pp. 70–106.
  2. 1 2 3 4 Ivantsov, A.Yu (2001). "Vendia and Other Precambrian "Arthropods"". Paleontological Journal. 35 (4): 335–343.
  3. 1 2 3 4 5 Ivantsov, A.Yu (2004). "New Proarticulata from the Vendian of the Arkhangel'sk region" (PDF). Paleontological Journal. 38 (3): 247–253. Archived from the original (PDF) on 27 September 2007. Retrieved 27 September 2007.
  4. ↑ Menner, V.V. (1963). "The other problematical organic remains". Stratigraphy of the USSR: Upper Precambrian (in Russian). Moscow, RU: Gos. Nauchno-Tekh. Izd. pp. 504–507.
  5. ↑ Glaessner, M.F.; Wade, M. (1971). "Praecambridium - a primitive arthropod". Lethaia. 4 (1): 71–77. doi:10.1111/j.1502-3931.1971.tb01280.x.
  6. 1 2 3 Ivantsov, A.Yu.; Malakhovskaya, Y.E.; Serezhnikova, E.A. (2004). "Some problematic fossils from the Vendian of the south-eastern White Sea region" (PDF). Paleontological Journal. 38 (1): 1–9. Archived from the original (PDF) on 4 July 2007. Retrieved 8 March 2007.
  7. ↑ Liu, Alexander G.; Matthews, Jack J.; Menon, Latha R.; McIlroy, Duncan; Brasier, Martin D. (22 October 2014). "Haootia quadriformis n. gen., n. sp., interpreted as a muscular cnidarian impression from the Late Ediacaran period (approx. 560 Ma)". Proceedings of the Royal Society B: Biological Sciences. 281 (1793): 20141202. doi:10.1098/rspb.2014.1202. PMC   4173675 .
  8. ↑ Ivantsov, A. Yu. (April 2007). "Small Vendian transversely Articulated fossils". Paleontological Journal. 41 (2): 113–122. doi:10.1134/S0031030107020013.
  9. ↑ Ivantsov, Andrey Yu.; Malakhovskaya, Ya.E.; Serezhnikova, E.A. (January 2004). "Some problematic fossils from the Vendian of the southeastern White Sea Region". Paleontological Journal. 38 (1): 1–9 – via researchgate.net.
  10. ↑ 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 .
  11. ↑ Boynton, H.E.; Ford, T.D. (1979). "Pseudovendia charnwoodensis — A new Precambrian arthropod from Charnwood Forest, Leicestershire". Mercian Geologist. 7: 175–177.
  12. ↑ Boynton, H.E. (2010). "Charnian fossils in the outwoods" (PDF). Mercian Geologist. 17 (3): 175–177.
  13. ↑ Grazhdankin, D.V. (2007). Charnwood biota as seen from arctic Russia – Ediacarans and their environments (PDF). Leicester’s fossil celebrity: Charnia and the evolution of early life (abstract). Leicester, UK: University of Leicester. pp. 15–16. Archived from the original (PDF) on 8 March 2021. Retrieved 20 September 2013.
  14. ↑ Liu, A.G.; McIlroy, D.; Antcliffe, J.B.; Brasier, M.D. (2010). "Effaced preservation in the Ediacara biota and its implications for the early macrofossil record". Palaeontology. 54 (3): 607–630. doi: 10.1111/j.1475-4983.2010.01024.x .
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