Cephalonega

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

Cephalonega stepanovi
Temporal range: Ediacaran, around 555 Ma
↓
Scientific classification
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

Etymology

Its original generic name Onega comes from the Onega Peninsula of the White Sea, where the first fossils were found. The specific name is given in honour of V. A. Stepanov, discoverer of the first Ediacaran fossil locality in Arkhangelsk Region, on the Letniy Bereg (Summer Coast) of the Onega Peninsula in 1972.[2] The original generic name is preoccupied 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 be placed in 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 recent study, all Cephalonega researchers agree that it is proarticulatan and put in a 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. 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). Izv. Akad. Nauk SSSR, Ser. Geol. (in Russian). 12: 130–134. Archived from the original (PDF) on 2007-02-07.
  3. A.Y. Ivantsov; M.A. Fedonkin; A.L. Nagovitsyn; M.A. Zakrevskaya (2019). "Cephalonega, a new generic name, and the system of Vendian Proarticulata". Paleontological Journal. 53 (5): 447–454. doi:10.1134/S0031030119050046.
  4. Andrey Ivantsov; Aleksey Nagovitsyn; Maria Zakrevskaya (2019). "Traces of locomotion of Ediacaran macroorganisms". Geosciences. 9 (9): Article 395. doi:10.3390/geosciences9090395.
  5. Ivantsov, A. Yu. (April 2007). "Small Vendian transversely Articulated fossils". Paleontological Journal. 41 (2): 113–122. doi:10.1134/S0031030107020013.
  6. 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. 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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