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

Name

Its original genus name ''Onega'' comes from the Onega Peninsula of the

White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...

, where the first fossils were found. The species name was given to honour V.A. Stepanov, who discovered the

Ediacaran The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...

fossil site on the Letniy Bereg (" Summer Coast") in 1972, on the Onega Peninsula, the first

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

site found in the

Arkhangelsk Oblast Arkhangelsk Oblast ( rus, Архангельская область, p=ɐrˈxanɡʲɪlʲskəjə ˈobɫəsʲtʲ) is a federal subjects of Russia, federal subject of Russia (an oblast). It includes the Arctic Ocean, Arctic archipelagos of Franz ...

. The original generic name is previously occupied by the

hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from ...

n genus ''Onega'' Distant (1908). Ivantsov ''et al.'' (2019) coined a replacement generic name ''Cephalonega''.

Morphology

The small fossils, which range up to long, have oval outlines and low bodies with an articulated central zone built of

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the existence or possibili ...

encircled by an undivided zone. The surface of the undivided region of ''Cephalonega'' is covered with small tubercles. ''Cephalonega'' was originally described by Mikhail Fedonkin as a problematic organism, being grouped together with '' Vendia'', '' Praecambridium'' and '' Vendomia'' as possible stem-group

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s due to a vague similarity with primitive

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

s and arthropods. In 1985 Mikhail Fedonkin erected

Phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

Proarticulata,M. A. Fedonkin (1985). "Systematic Description of Vendian Metazoa". ''Vendian System: Historical–Geological and Paleontological Foundation, Vol. 1: Paleontology''. Moscow: Nauka, pp. 70–106. in which he placed: ''Cephalonega'', ''

Dickinsonia ''Dickinsonia'' is a genus of extinct organism that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It had a round, bilaterally symmetric body with multiple segments running along it. It could range f ...

'', '' 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 ''Skania'' is a Cambrian fossil arthropod. The type species, ''S. fragillis'', is known from the Burgess Shale of British Columbia, Canada. A second possible species ''"S." sundbergi'' is known from the Kaili Formation of China, but its place ...

''.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. Andrey Yu. Ivantsov has proposed that ''Cephalonega'' should be placed in the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

Proarticulata Proarticulata is a proposed phylum of extinct, near-bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately . The name comes from the Greek () = "before" and Articulata, i. ...

, as the segments in recently discovered, exceptionally well-preserved fossils display the glide, or "staggered", symmetry characteristic of the majority of proarticulatans. 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 ''Yorgia waggoneri'' is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of . It is classified within the extinct animal phylum Proart ...

'', ''

Andiva ''Andiva ivantsovi'' is a Vendian fossil, identified to be a bilaterian triploblastic animal in the Ediacaran phylum Proarticulata, known from the Winter Coast, White Sea, Russia. It was first discovered in 1977, and described as a new species ...

'' and ''

Spriggina ''Spriggina'' is a genus of early animals whose relationship to living animals is unclear. Fossils of ''Spriggina'' are known from the late Ediacaran period in what is now South Australia. ''Spriggina floundersi'' is the official fossil emblem o ...

''.

Fossil record

Imprints of ''Cephalonega stepanovi'' have been found in the Verkhovka and Zimnie Gory Formations of the Ediacaran (Vendian) rocks of the Arkhangelsk Region, Russia. 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 mat A microbial mat is a multi-layered sheet or biofilm of microbial colonies, composed of mainly bacteria and/or archaea. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few surviv ...

s. The same bedding planes contain various other Ediacaran species: '' Cyclomedusa'', '' Ediacaria'', Palaeopascichnids, '' Eoporpita'', ''

'', ''

Archaeaspinus ''Archaeaspinus fedonkini'' is an extinct proarticulatan organism from the Late Ediacaran period. Background ''Archaeaspinus'' was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001. Since the ...

'', '' Vendia'', ''

'', ''

Anfesta ''Anfesta stankovskii'' is a tri-radially symmetrical fossil animal that lived on the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa. Etymology The generic and specific names of ''Anfesta stankovskii'' honour ...

'', ''

Albumares ''Albumares brunsae'' is a tri-radially symmetrical fossil animal that lived on the late Ediacaran seafloor. It is a member of the extinct group Trilobozoa. Etymology The generic name ''Albumares'' derives from the Latin ''Mare Album'' (White S ...

'', ''

Tribrachidium ''Tribrachidium heraldicum'' is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. ''T. heraldicum'' is the best known member of the extinct group Trilobozoa. Etymolo ...

'', ''

Kimberella ''Kimberella'' is an extinct genus of marine bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity ...

'', ''

Parvancorina ''Parvancorina'' is a genus of shield-shaped bilaterally symmetrical fossil animal that lived in the late Ediacaran seafloor. It has some superficial similarities with the Cambrian trilobite-like arthropods. Etymology The generic name is deriv ...

'', '' Charniodiscus'' and others.

References

{{Taxonbar, from1=Q133329055, from2=Q133329146, from3=Q133328889, from4=Q2668806 Enigmatic Proarticulata taxa Fossil taxa described in 1976 Fossils of Russia White Sea fossils Ediacaran life Controversial taxa

Name

Morphology

Fossil record

See also

References