A. Uchman, Z. Lebanidze, T. Beridze, N. Kobakhidze, Koba Lobzhanidze, Sophio Khutsishvili, R. Chagelishvili, Davit Makadze, K. Koiava, N. Khundadze
{"title":"对Megagrapton Książkiewicz, 1968年的修正,重点研究了Megagrapton aequale Seilacher, 1977年,来自格鲁吉亚小高加索地区下始新世","authors":"A. Uchman, Z. Lebanidze, T. Beridze, N. Kobakhidze, Koba Lobzhanidze, Sophio Khutsishvili, R. Chagelishvili, Davit Makadze, K. Koiava, N. Khundadze","doi":"10.7306/gq.1640","DOIUrl":null,"url":null,"abstract":"Megagrapton Książkiewicz, 1968 is a characteristic deep-sea trace fossil belonging to the group of graphoglyptids and mostly preserved as a network of irregular meshes in hypichnial semirelief. So far, eleven ichnospecies have been distinguished under this ichnogenus, though commonly on weak evidence. The so-far poorly known ichnospecies Megagrapton aequale Seilacher, 1977 is described here on the basis of the numerous, newly discovered specimens from deep-sea siliciclastic deposits of the Bolevani Subsuite (lower Eocene) in the Lesser Caucasus of Georgia, together with other collections and published examples. A neotype of this ichnospecies is designated and the diagnosis emended. M. aequale occurs in lower Cambrian to upper Miocene deep-sea turbiditic deposits, mostly in the Paleogene. It is characterized by relatively small, variable meshes, which have mostly irregular sub-pentagonal, sub-hexagonal or sub-heptagonal shapes that are variable in size and are bordered by curved or straight semicircular ridges. It has been mistaken for Paleodictyon, which forms regular hexagonal nets. Paleodictyon imperfectum Seilacher, 1977 is included in M. aequale as the ichnosubspecies M. a. imperfectum, which is characterized by relatively thin bordering ridges. After critical analysis of all ichnospecies, only M. irregulare Książkiewicz, 1968, M. submontanum (Azpeitia Moros, 1933), and M. aequale are recommended for further use. These are distinguished on the basis of the prevailing morphology of the meshes, irrespective of large differences in morphometric parameters within the ichnospecies. Irredictyon chaos Vialov, 1972 is included in M. irregulare as the ichnosubspecies M. i. chaos, which is characterized by relatively thick bordering ridges. Megagrapton is interpreted as a cast of a subsurface open burrow network with a few connections to the sea floor. The burrows probably functioned as a trap for small organisms (ethological subcategory irretichnia).","PeriodicalId":12587,"journal":{"name":"Geological Quarterly","volume":" ","pages":""},"PeriodicalIF":0.9000,"publicationDate":"2022-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"Revision of the trace fossil Megagrapton Książkiewicz, 1968 with focus on Megagrapton aequale Seilacher, 1977 from the lower Eocene of the Lesser Caucasus in Georgia\",\"authors\":\"A. Uchman, Z. Lebanidze, T. Beridze, N. Kobakhidze, Koba Lobzhanidze, Sophio Khutsishvili, R. Chagelishvili, Davit Makadze, K. Koiava, N. Khundadze\",\"doi\":\"10.7306/gq.1640\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Megagrapton Książkiewicz, 1968 is a characteristic deep-sea trace fossil belonging to the group of graphoglyptids and mostly preserved as a network of irregular meshes in hypichnial semirelief. So far, eleven ichnospecies have been distinguished under this ichnogenus, though commonly on weak evidence. The so-far poorly known ichnospecies Megagrapton aequale Seilacher, 1977 is described here on the basis of the numerous, newly discovered specimens from deep-sea siliciclastic deposits of the Bolevani Subsuite (lower Eocene) in the Lesser Caucasus of Georgia, together with other collections and published examples. A neotype of this ichnospecies is designated and the diagnosis emended. M. aequale occurs in lower Cambrian to upper Miocene deep-sea turbiditic deposits, mostly in the Paleogene. It is characterized by relatively small, variable meshes, which have mostly irregular sub-pentagonal, sub-hexagonal or sub-heptagonal shapes that are variable in size and are bordered by curved or straight semicircular ridges. It has been mistaken for Paleodictyon, which forms regular hexagonal nets. Paleodictyon imperfectum Seilacher, 1977 is included in M. aequale as the ichnosubspecies M. a. imperfectum, which is characterized by relatively thin bordering ridges. After critical analysis of all ichnospecies, only M. irregulare Książkiewicz, 1968, M. submontanum (Azpeitia Moros, 1933), and M. aequale are recommended for further use. These are distinguished on the basis of the prevailing morphology of the meshes, irrespective of large differences in morphometric parameters within the ichnospecies. Irredictyon chaos Vialov, 1972 is included in M. irregulare as the ichnosubspecies M. i. chaos, which is characterized by relatively thick bordering ridges. Megagrapton is interpreted as a cast of a subsurface open burrow network with a few connections to the sea floor. 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Revision of the trace fossil Megagrapton Książkiewicz, 1968 with focus on Megagrapton aequale Seilacher, 1977 from the lower Eocene of the Lesser Caucasus in Georgia
Megagrapton Książkiewicz, 1968 is a characteristic deep-sea trace fossil belonging to the group of graphoglyptids and mostly preserved as a network of irregular meshes in hypichnial semirelief. So far, eleven ichnospecies have been distinguished under this ichnogenus, though commonly on weak evidence. The so-far poorly known ichnospecies Megagrapton aequale Seilacher, 1977 is described here on the basis of the numerous, newly discovered specimens from deep-sea siliciclastic deposits of the Bolevani Subsuite (lower Eocene) in the Lesser Caucasus of Georgia, together with other collections and published examples. A neotype of this ichnospecies is designated and the diagnosis emended. M. aequale occurs in lower Cambrian to upper Miocene deep-sea turbiditic deposits, mostly in the Paleogene. It is characterized by relatively small, variable meshes, which have mostly irregular sub-pentagonal, sub-hexagonal or sub-heptagonal shapes that are variable in size and are bordered by curved or straight semicircular ridges. It has been mistaken for Paleodictyon, which forms regular hexagonal nets. Paleodictyon imperfectum Seilacher, 1977 is included in M. aequale as the ichnosubspecies M. a. imperfectum, which is characterized by relatively thin bordering ridges. After critical analysis of all ichnospecies, only M. irregulare Książkiewicz, 1968, M. submontanum (Azpeitia Moros, 1933), and M. aequale are recommended for further use. These are distinguished on the basis of the prevailing morphology of the meshes, irrespective of large differences in morphometric parameters within the ichnospecies. Irredictyon chaos Vialov, 1972 is included in M. irregulare as the ichnosubspecies M. i. chaos, which is characterized by relatively thick bordering ridges. Megagrapton is interpreted as a cast of a subsurface open burrow network with a few connections to the sea floor. The burrows probably functioned as a trap for small organisms (ethological subcategory irretichnia).
期刊介绍:
The policy of the Geological Quarterly is to publish significant contributions of information and geological insight relevant to an international readership. The journal has been issued since 1957 at the Polish Geological Institute - National Research Institute and, at present, is the leading Earth sciences journal in Poland. All aspects of Earth and related sciences, and universal and broad regional rather than locally oriented topics are covered.
The journal is intended to be an international forum for the exchange of information and ideas, particularly on important geological topics of Central Europe.