Cephalonega stepanovi
Temporal range: Ediacaran, around
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: †Proarticulata
Class: †Cephalozoa
Genus: †Cephalonega
Ivantsov et al., 2019
Species:
†C. stepanovi
Binomial name
†Cephalonega stepanovi
(Fedonkin, 1976[1])
Synonyms

Onega stepanovi Fedonkin, 1976

Cephalonega stepanovi is a fossil organism from Ediacaran deposits of the Arkhangelsk Region, Russia. It was described by Mikhail A. Fedonkin in 1976[1]

Name

Its original genus name Onega comes from the Onega Peninsula of the White Sea, where the first fossils were found. The species name was given to honour V.A. Stepanov, who discovered the Ediacaran fossil site on the Letniy Bereg ("Summer Coast") in 1972, on the Onega Peninsula, the first Proterozoic site found in the Arkhangelsk Oblast.[2] The original generic name is previously occupied by the hemipteran genus Onega Distant (1908). Ivantsov et al. (2019) coined a replacement generic name Cephalonega.[3][4]

Morphology

The small fossils, which range up to 7 millimetres (0.28 in) long, have oval outlines and low bodies with an articulated central zone built of isomers encircled by an undivided zone. The surface of the undivided region of Cephalonega is covered with small tubercles.[5]

Cephalonega was originally described by Mikhail Fedonkin as a problematic organism, being grouped together with Vendia, Praecambridium and Vendomia as possible stem-group arthropods due to a vague similarity with primitive Cambrian trilobites and arthropods.[1]

In 1985 Mikhail Fedonkin erected Phylum Proarticulata,[6] in which he placed: Cephalonega, Dickinsonia, Palaeoplatoda, Vendia, Vendomia, Praecambridium and Pseudovendia sp., although he did not exclude the possibility that Cephalonega may still be related to various lower Cambrian arthropods, such as Skania.[6][7]

Andrey Yu. Ivantsov has proposed that Cephalonega should be placed in the phylum Proarticulata, as the segments in recently discovered, exceptionally well-preserved fossils display the glide, or "staggered", symmetry characteristic of the majority of proarticulatans.[5]

According to a 2019 study, all Cephalonega researchers agree that it is proarticulatan and put it in the class Cephalozoa that also includes e.g. Yorgia, Andiva and Spriggina.[3]

Fossil record

Imprints of Cephalonega stepanovi have been found in the Verkhovka and Zimnie Gory Formations[8][9] of the Ediacaran (Vendian) rocks of the Arkhangelsk Region, Russia.[5]

All the fossil specimens are negative imprints on the bases of fine-grained sandstone beds with the "elephant skin" and tubercle texture diagnostic of microbial mats.[10] The same bedding planes contain various other Ediacaran species: Cyclomedusa, Ediacaria, Palaeopascichnids, Eoporpita, Yorgia, Andiva, Archaeaspinus, Vendia, Dickinsonia, Anfesta, Albumares, Tribrachidium, Kimberella, Parvancorina, Charniodiscus and others.

See also

References

  1. 1 2 3 B. M. Keller & M. A. Fedonkin (1976). Новые находки окаменелостей в валдайской серии докембрия по р. Сюзьме [New Records of Fossils in the Valdaian Group of the Precambrian on the Syuz'ma River] (PDF). Izv. Akad. Nauk SSSR, Ser. Geol. (in Russian). 3: 38–44. Archived from the original (PDF) on 2007-09-27.
  2. ↑ Keller, B.M.; Menner, V.V.; Stepanov, V.A. & Chumakov, N.M. (1974). "Новые находки Metazoa в вендомии Руссой платформы" [New Finds of Metazoa in the Vendomii of the Russian Platform] (PDF). Izvestiya Akademii Nauk SSR. Seriya Geologicheskaya (in Russian). 12: 130–134. Archived from the original (PDF) on 7 February 2007.
  3. 1 2 Ivantsov, A.Y.; Fedonkin, M.A.; Nagovitsyn, A.L.; Zakrevskaya, M.A. (2019). "Cephalonega, a new generic name, and the system of Vendian Proarticulata". Paleontological Journal. 53 (5): 447–454. doi:10.1134/S0031030119050046. S2CID 203853224.
  4. ↑ Ivantsov, Andrey; Nagovitsyn, Aleksey; Zakrevskaya, Maria (2019). "Traces of locomotion of Ediacaran macroorganisms". Geosciences. 9 (9). Article 395. Bibcode:2019Geosc...9..395I. doi:10.3390/geosciences9090395.
  5. 1 2 3 Ivantsov, A. Yu. (April 2007). "Small Vendian transversely Articulated fossils". Paleontological Journal. 41 (2): 113–122. doi:10.1134/S0031030107020013. S2CID 86636748.
  6. 1 2 M. A. Fedonkin (1985). "Systematic Description of Vendian Metazoa". Vendian System: Historical–Geological and Paleontological Foundation, Vol. 1: Paleontology. Moscow: Nauka, pp. 70–106.
  7. ↑ Stefan Hengtson; Mikhail A. Fedonkin; Jere H. Lipps. (1992). "The Major Biotas of Proterozoic to Early Cambrian Multicellular Organisms". In: Edited by J. William Schopf; Cornelis Klein. Proterozoic Biosphere. Cambridge University Press, pp. 433–435.
  8. ↑ D. V. Grazhdankin (2003). "The Structure and Sedimentation Conditions in the Vendian assemblage in the Southeastern White Sea" (PDF). Stratigraphy and Geological Correlation. 11 (4): 313–331. Archived from the original (PDF) on 2007-08-04. Retrieved 2008-11-04.
  9. ↑ D. V. Grazhdankin (2004). "Patterns of distribution in the Ediacaran biotas: facies versus biogeography and evolution" (PDF). Paleobiology. 30 (2): 203–221. doi:10.1666/0094-8373(2004)030<0203:PODITE>2.0.CO;2. S2CID 129376371. Archived from the original (PDF) on 2007-02-26. Retrieved 2008-11-04.
  10. ↑ Gehling, J. G. (1999). "Microbial mats in terminal Proterozoic siliciclastics: Ediacaran death masks". PALAIOS. 14 (1): 40–57. Bibcode:1999Palai..14...40G. doi:10.2307/3515360. JSTOR 3515360.
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