The Guole biota contains common shelly fossils and some exceptionally well-preserved softbodied fossils. Stratigraphically, it is located in the mudstones and siltstones of the Sandu Formation near Guole Town, Jingxi ...The Guole biota contains common shelly fossils and some exceptionally well-preserved softbodied fossils. Stratigraphically, it is located in the mudstones and siltstones of the Sandu Formation near Guole Town, Jingxi County, Guangxi, South China. It is the first Furongian （late Cambrian） Burgess Shale-type biota found in the world, thereby filling the gap between middle Cambrian and Lower Ordovician Burgess Shale-type Lagerstaitten. Preliminary studies suggest that the Guole biota includes approximately seven metazoan groups as well as algae. These will provide important new evolutionary and ecological information.展开更多
Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected： Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus...Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected： Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus inornatus-Monocostodus sevierensis-Semiacontiodus lavadamensis zones, in ascending order. More confident biozones are recognized in the Sesong Slate and lower Hwajeol Formation in the Makgol section, a part of the southern limb of the Baekunsan syncline, Taebaeksan Basin, Korea, especially focusing on the conodont biostratigraphic boundary of two units, and the subdivision potential of the previous ＂Proconodontus Zone＂, lowermost biozone of the Hwajeol Formation. Similarly, only a few conodont elements recovered from upper 14.5 m interval, namely the Furongian portion of the Sesong Slate, in the Makgol section did not allow erection of a biozone. Nevertheless, this part of the unit plus the basal 2.5 m interval of the Hwajeol Formation is characterized by the occurrence of Prooneotodus rotundatus（Druce and Jones）, Teridontus nakamurai（Nogami）, Phakelodus elongatus（An） and Phakelodus tenuis Müller. This interval marks the early Furongian ＂Prooneotodus rotundatus Zone＂. The rest of the measured section yielded relatively abundant conodonts, so three conodont biozones are proposed, based on the successive appearance of key species： Proconodontus tenuiserratus, Proconodontus posterocostatus, and Proconodontus muelleri zones, in ascending order, and thus allowing subdivision of the previous ＂Proconodontus Zone＂. The four conodont biozones are correlated with the relevant biozones of North and South China, and North America.展开更多
The Middle-Upper Cambrian Xixiangchi Group in the Sichuan Basin is mainly a set of dolomites of platform facies.In the past,there was no effective way to determine the bottom boundary mark of the Upper Cambrian strata...The Middle-Upper Cambrian Xixiangchi Group in the Sichuan Basin is mainly a set of dolomites of platform facies.In the past,there was no effective way to determine the bottom boundary mark of the Upper Cambrian strata,so natural gas exploration of this horizon lagged behind.In this paper,it is revealed from the C and O isotopic profile of debris that in the middle of the Xixiangchi Group,there is a positive excursion event of carbon isotopes that can be correlated all over the world,so it can be used as an important mark to identify the Furongian Series(equivalent to the Upper Cambrian strata).Then,based on the characteristics of electric curves,the Furongian Series boundary mark was determined and its classification program was worked out preliminarily.It is shown that during the deposition of the Xixiangchi Group,it is a paleo-geomorphologically gentle-slope carbonate platform which is high in the east and low in the east,and a thinemoderate dolomite layer which is thin in the west and thick in the east is deposited.This layer is vertically divided into 4 intervals.Besides,the bottom boundary mark of the Furongian Series in the Sichuan Basin and its adjacent areas can be determined by combining the SPICE(Steptoean Positive Carbon Isotope Excursion)event of carbon isotopes with the characteristics of electric curves.Finally,the carbon isotope mark of the Furongian Series bottom boundary is the SPICE event corresponding to the positive excursion which is regionally correlated,the corresponding electrical mark is the GR small peak areas in the middle of the Xixiangchi group,and the corresponding lithologic symbol is the argillaceous dolomite.The research results are conducive to the further subdivision of the Xixiangchi Group in the Sichuan Basin and its adjacent areas and promoting the study on sedimentary evolution and reservoir distribution laws so that gas exploration in this series of strata can be speeded up.展开更多
Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks migh...Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks might be critical to the formation of limestone conglomerates.According to detailed field measurement and laboratory analyses (thin section observation and XRD analysis),four types of ribbon rocks are classified,i.e.,limestone and marlstone couplet (L-M),limestone and shale couplet (L-S),thin-bedded lime mudstone (Ltb),and laminated limestone and marlstone couplet (Cl).These ribbon rocks were mostly deposited in low-energy subtidal environments (below fair-weather wave base).Ribbon rocks exhibit various subtle deformation structures such as intrastratal cracks and "boudin" structures.Differential cementation of carbonate and argillaceous layers during early diagenesis is a prerequisite condition for the deformation of ribbon rock under compaction.Ribbon rocks would be deformed into limestone conglomerates under differential compaction that might be triggered by external forces such as storm and earthquake.展开更多
The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian ...The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian Series in the Tarim Craton has not yet been established due to the scarcity of fossils and the absence of the Steptoean Positive Carbon Isotope Excursion(SPICE),which is the primary global carbon isotope excursion of the Furongian Series.In this study,the SPICE was discovered by examining the carbon isotopes of the representative drilling wells in the West Platform and East Basin.A positive carbon isotope anomaly withδ13C values ranging from 1.5‰to 1.9‰(PDB),were found in the middle of the Xiaqiulitag Formation of the three drilling wells in the West Platform,and a positive excursion withδ13C values up to 4.0‰(PDB),which is correlated with the SPICE,was found in the lower limestone of the Tuershaketag Formation in the East Basin.Based on the carbon isotopic data and chemostratigraphic correlation,the chronostratigraphic framework of the Furongian Series across different facies in the Tarim Craton is preliminarily established.The basal boundary of the Furongian Series was preliminarily defined by the occurrence of the SPICE.Aweak positive anomaly ofδ13C was observed at the base of the Penglaiba Formation of the three boreholes in the West Platform and the top of the Tuershaketag Formation of Tadong-2 well.We propose that the positive anomaly of the carbon isotope above the weak negative anomaly at the base of the Penglaiba Formation and the top of the Tuershaketag Formation can be used to define the Cambrian-Ordovician boundary in the Tarim Craton.展开更多
The International Commission on Stratigraphy and the IUGS Executive Committee have recently approved a Global Standard Stratotype-section and Point(GSSP)defining the base of the second stage of the Furongian Series,Ca...The International Commission on Stratigraphy and the IUGS Executive Committee have recently approved a Global Standard Stratotype-section and Point(GSSP)defining the base of the second stage of the Furongian Series,Cambrian System.This stage is named the Jiangshanian Stage,after Jiangshan City,western Zhejiang Province,China,where the GSSP is located.The GSSP is exposed in a natural outcrop near Duibian Village.It is defined at the base of a limestone(wackestone)layer 108.12 m above the base of the Huayansi Formation in the Duibian B section,coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis(base of the A.orientalis Zone).The GSSP is at a position of 28°48.977´N latitude and 118º36.887´E longitude.Secondary global markers at or near the base of the stage include the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata,which coincides with the FAD of the primary marker in the stratotype section,and near the end of a large positive carbon isotopic excursion(SPICE excursion).Faunal turnovers close to the base of the Jiangshanian Stage have been recognized as being at the base of the Iverian Stage in Australia,the Gonggrian Stage in Korea,and the Agnostotes orientalis–Irvingella perfecta Zone in Siberia,and near the base of the Aksayan Stage in Kazakhstan,the Sunwaptan Stage in Laurentia,and the Parabolina brevispina Zone in Baltica.展开更多
The Kyrshabakty section in the Malyi Karatau Range,southern Kazakhstan,has been approved as the Auxiliary boundary Stratotype Section and Point(ASSP)for the base of the Jiangshanian Stage of the Furongian Series(Cambr...The Kyrshabakty section in the Malyi Karatau Range,southern Kazakhstan,has been approved as the Auxiliary boundary Stratotype Section and Point(ASSP)for the base of the Jiangshanian Stage of the Furongian Series(Cambrian System).The first appearance datum(FAD)of the agnostoid trilobite Agnostotes orientalis coincides with the horizon marking the base of the Jiangshanian Stage,and the FAD of A.orientalis occurs at 259.0 m in the measured section,61.2 m above the base of Unit 8 in the Zhumabai Formation.The boundary interval in the Kyshabakty section shows a relatively monotonous succession of carbonate deposits.The section contains an abundance of Cambrian fossils including diverse trilobites,brachiopods,molluscs,bradoriids,protoconodonts and paraconodonts.展开更多
The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularl...The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularly, the trilobite biozones of the formation have been well defined. On the other hand, little has hitherto been studied on conodont microfossils for the formation. This paper reports a diverse and well-preserved protoconodonts and paraconodonts of Series 3 from the formation in the Eodungol Section, exposed along a southern mountain trail of Mt. Sambangsan, Yeongwol, Korea. Five of the 13 samples collected for conodont contain a rich protoconodont and paraconodont assemblage and numerous shelly fossils including trilobites, brachiopods, sponge spicules, hyolithids, and incertae sedis. Sample Eo 5 is extremely fossiliferous （465 elements, 96.5% of total collection）, and the most abundant species was Phakelodus elongatus （236 elements, 62% of the Eo 5 collection）. The preservation is relatively good, but some specimens are corroded and fragmentary. Some of the protoconodonts are exfoliated. Relatively larger ones were commonly preserved as phosphatized internal molds, particularly in specimens of Furnishina bigeminata, Furnishina leei n. sp., Muellerodus pomeranensis, Nogamiconus sinensis, and westergaardodids. Phakelodids were commonly preserved as clusters. Among 20 species referable to nine genera, Furnishina bigeminata, Furnishina leei n. sp., Nogamiconus sinensis, Huayuanodontus tricornis, Proscandodus obliquus, and Westergaardodina grandidens were previously undescribed species in Korea. This assemblage is named herein as the Westergaardodina matsushitai Zone, which is a new biozonal name replacing the old one, i.e., Gapparodus bisulcatus-Westergaardodina matsushitai-Westergaardodina moessebergensis Assemblage. The W. matsushitai Zone corresponds to the Lejopyge armata trilobite Zone and is well correlated with the upper Series 3 conodont biozones of the Westergaardodina matsushitai-Westergaardodina grandidens Zone of South China and the Westergaardodina matsushitai Zone of North China, respectively. The present data allow a useful correlation to China and Baltica in relation to new subdivision of the Cambrian. Furnishina leei n. sp. is newly described.展开更多
The originations of marine planktons and nektons are significantly delayed than that of benthos,as evidenced by the fossil record.The Cambrian Explosion produced a variety of high-level marine organisms,and many remar...The originations of marine planktons and nektons are significantly delayed than that of benthos,as evidenced by the fossil record.The Cambrian Explosion produced a variety of high-level marine organisms,and many remarkablebody-plans.However,a majority of these organisms are benthic or level-bottomed,and are rather dependent on the substrates of sea floors.展开更多
基金supported by the Chinese Academy of Sciences(2015FY310100)the Natural Science Foundation of China(41330101, 41221001,41290260,40602002,40872010,41521061, and 41072018)+2 种基金SZ is supported by a Ramon y Cajal grant (RYC-2012-10576)project CGL2013-48877-P from Spanish MINECO and EU-FEDERa contribution of the ANR(Agence Nationale de la Recherche) project RALI "Rise of Animal Life (Cambrian-Ordovician-organization and tempo:evidence from exceptionally preserved biota"
文摘The Guole biota contains common shelly fossils and some exceptionally well-preserved softbodied fossils. Stratigraphically, it is located in the mudstones and siltstones of the Sandu Formation near Guole Town, Jingxi County, Guangxi, South China. It is the first Furongian （late Cambrian） Burgess Shale-type biota found in the world, thereby filling the gap between middle Cambrian and Lower Ordovician Burgess Shale-type Lagerstaitten. Preliminary studies suggest that the Guole biota includes approximately seven metazoan groups as well as algae. These will provide important new evolutionary and ecological information.
基金supported by the Basic Science Research Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Education, Science and Technology (Grant No. 2012005044)
文摘Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected： Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus inornatus-Monocostodus sevierensis-Semiacontiodus lavadamensis zones, in ascending order. More confident biozones are recognized in the Sesong Slate and lower Hwajeol Formation in the Makgol section, a part of the southern limb of the Baekunsan syncline, Taebaeksan Basin, Korea, especially focusing on the conodont biostratigraphic boundary of two units, and the subdivision potential of the previous ＂Proconodontus Zone＂, lowermost biozone of the Hwajeol Formation. Similarly, only a few conodont elements recovered from upper 14.5 m interval, namely the Furongian portion of the Sesong Slate, in the Makgol section did not allow erection of a biozone. Nevertheless, this part of the unit plus the basal 2.5 m interval of the Hwajeol Formation is characterized by the occurrence of Prooneotodus rotundatus（Druce and Jones）, Teridontus nakamurai（Nogami）, Phakelodus elongatus（An） and Phakelodus tenuis Müller. This interval marks the early Furongian ＂Prooneotodus rotundatus Zone＂. The rest of the measured section yielded relatively abundant conodonts, so three conodont biozones are proposed, based on the successive appearance of key species： Proconodontus tenuiserratus, Proconodontus posterocostatus, and Proconodontus muelleri zones, in ascending order, and thus allowing subdivision of the previous ＂Proconodontus Zone＂. The four conodont biozones are correlated with the relevant biozones of North and South China, and North America.
基金Project supported by the National Major Science and Technology Project(No.2011ZX05004)PetroChina Southwest Oilfield Company Research Project“Xixiangchi stratigraphic division and sedimentary evolution rule research”(No.XNS14NH2015-002).
文摘The Middle-Upper Cambrian Xixiangchi Group in the Sichuan Basin is mainly a set of dolomites of platform facies.In the past,there was no effective way to determine the bottom boundary mark of the Upper Cambrian strata,so natural gas exploration of this horizon lagged behind.In this paper,it is revealed from the C and O isotopic profile of debris that in the middle of the Xixiangchi Group,there is a positive excursion event of carbon isotopes that can be correlated all over the world,so it can be used as an important mark to identify the Furongian Series(equivalent to the Upper Cambrian strata).Then,based on the characteristics of electric curves,the Furongian Series boundary mark was determined and its classification program was worked out preliminarily.It is shown that during the deposition of the Xixiangchi Group,it is a paleo-geomorphologically gentle-slope carbonate platform which is high in the east and low in the east,and a thinemoderate dolomite layer which is thin in the west and thick in the east is deposited.This layer is vertically divided into 4 intervals.Besides,the bottom boundary mark of the Furongian Series in the Sichuan Basin and its adjacent areas can be determined by combining the SPICE(Steptoean Positive Carbon Isotope Excursion)event of carbon isotopes with the characteristics of electric curves.Finally,the carbon isotope mark of the Furongian Series bottom boundary is the SPICE event corresponding to the positive excursion which is regionally correlated,the corresponding electrical mark is the GR small peak areas in the middle of the Xixiangchi group,and the corresponding lithologic symbol is the argillaceous dolomite.The research results are conducive to the further subdivision of the Xixiangchi Group in the Sichuan Basin and its adjacent areas and promoting the study on sedimentary evolution and reservoir distribution laws so that gas exploration in this series of strata can be speeded up.
基金supported by National Natural Science Foundation of China (Grant No.40972043)Natural Science Foundation of Shandong Province (Grant No.Y2008E02)Scientific Program of Shandong Provincial Education Department (Grant No.G08LD01)
文摘Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks might be critical to the formation of limestone conglomerates.According to detailed field measurement and laboratory analyses (thin section observation and XRD analysis),four types of ribbon rocks are classified,i.e.,limestone and marlstone couplet (L-M),limestone and shale couplet (L-S),thin-bedded lime mudstone (Ltb),and laminated limestone and marlstone couplet (Cl).These ribbon rocks were mostly deposited in low-energy subtidal environments (below fair-weather wave base).Ribbon rocks exhibit various subtle deformation structures such as intrastratal cracks and "boudin" structures.Differential cementation of carbonate and argillaceous layers during early diagenesis is a prerequisite condition for the deformation of ribbon rock under compaction.Ribbon rocks would be deformed into limestone conglomerates under differential compaction that might be triggered by external forces such as storm and earthquake.
基金supported by the National Science and Technology Major Project(Grant Nos.2016ZX05004-004&2017ZX05008-005)。
文摘The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian Series in the Tarim Craton has not yet been established due to the scarcity of fossils and the absence of the Steptoean Positive Carbon Isotope Excursion(SPICE),which is the primary global carbon isotope excursion of the Furongian Series.In this study,the SPICE was discovered by examining the carbon isotopes of the representative drilling wells in the West Platform and East Basin.A positive carbon isotope anomaly withδ13C values ranging from 1.5‰to 1.9‰(PDB),were found in the middle of the Xiaqiulitag Formation of the three drilling wells in the West Platform,and a positive excursion withδ13C values up to 4.0‰(PDB),which is correlated with the SPICE,was found in the lower limestone of the Tuershaketag Formation in the East Basin.Based on the carbon isotopic data and chemostratigraphic correlation,the chronostratigraphic framework of the Furongian Series across different facies in the Tarim Craton is preliminarily established.The basal boundary of the Furongian Series was preliminarily defined by the occurrence of the SPICE.Aweak positive anomaly ofδ13C was observed at the base of the Penglaiba Formation of the three boreholes in the West Platform and the top of the Tuershaketag Formation of Tadong-2 well.We propose that the positive anomaly of the carbon isotope above the weak negative anomaly at the base of the Penglaiba Formation and the top of the Tuershaketag Formation can be used to define the Cambrian-Ordovician boundary in the Tarim Craton.
基金supported in part by grants from the State Key Laboratory on Palaeobiology and Stratigraphy,(2009110320121101)+2 种基金the Ministry of Science and Technology of China(2006FY120300)the National Natural Science Foundation of China(41290260,41221001)the National Commission on Stratigraphy of China to Peng.
文摘The International Commission on Stratigraphy and the IUGS Executive Committee have recently approved a Global Standard Stratotype-section and Point(GSSP)defining the base of the second stage of the Furongian Series,Cambrian System.This stage is named the Jiangshanian Stage,after Jiangshan City,western Zhejiang Province,China,where the GSSP is located.The GSSP is exposed in a natural outcrop near Duibian Village.It is defined at the base of a limestone(wackestone)layer 108.12 m above the base of the Huayansi Formation in the Duibian B section,coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis(base of the A.orientalis Zone).The GSSP is at a position of 28°48.977´N latitude and 118º36.887´E longitude.Secondary global markers at or near the base of the stage include the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata,which coincides with the FAD of the primary marker in the stratotype section,and near the end of a large positive carbon isotopic excursion(SPICE excursion).Faunal turnovers close to the base of the Jiangshanian Stage have been recognized as being at the base of the Iverian Stage in Australia,the Gonggrian Stage in Korea,and the Agnostotes orientalis–Irvingella perfecta Zone in Siberia,and near the base of the Aksayan Stage in Kazakhstan,the Sunwaptan Stage in Laurentia,and the Parabolina brevispina Zone in Baltica.
文摘The Kyrshabakty section in the Malyi Karatau Range,southern Kazakhstan,has been approved as the Auxiliary boundary Stratotype Section and Point(ASSP)for the base of the Jiangshanian Stage of the Furongian Series(Cambrian System).The first appearance datum(FAD)of the agnostoid trilobite Agnostotes orientalis coincides with the horizon marking the base of the Jiangshanian Stage,and the FAD of A.orientalis occurs at 259.0 m in the measured section,61.2 m above the base of Unit 8 in the Zhumabai Formation.The boundary interval in the Kyshabakty section shows a relatively monotonous succession of carbonate deposits.The section contains an abundance of Cambrian fossils including diverse trilobites,brachiopods,molluscs,bradoriids,protoconodonts and paraconodonts.
基金supported by the National Research Foundation(NRF) of Korea (No. 110439)
文摘The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularly, the trilobite biozones of the formation have been well defined. On the other hand, little has hitherto been studied on conodont microfossils for the formation. This paper reports a diverse and well-preserved protoconodonts and paraconodonts of Series 3 from the formation in the Eodungol Section, exposed along a southern mountain trail of Mt. Sambangsan, Yeongwol, Korea. Five of the 13 samples collected for conodont contain a rich protoconodont and paraconodont assemblage and numerous shelly fossils including trilobites, brachiopods, sponge spicules, hyolithids, and incertae sedis. Sample Eo 5 is extremely fossiliferous （465 elements, 96.5% of total collection）, and the most abundant species was Phakelodus elongatus （236 elements, 62% of the Eo 5 collection）. The preservation is relatively good, but some specimens are corroded and fragmentary. Some of the protoconodonts are exfoliated. Relatively larger ones were commonly preserved as phosphatized internal molds, particularly in specimens of Furnishina bigeminata, Furnishina leei n. sp., Muellerodus pomeranensis, Nogamiconus sinensis, and westergaardodids. Phakelodids were commonly preserved as clusters. Among 20 species referable to nine genera, Furnishina bigeminata, Furnishina leei n. sp., Nogamiconus sinensis, Huayuanodontus tricornis, Proscandodus obliquus, and Westergaardodina grandidens were previously undescribed species in Korea. This assemblage is named herein as the Westergaardodina matsushitai Zone, which is a new biozonal name replacing the old one, i.e., Gapparodus bisulcatus-Westergaardodina matsushitai-Westergaardodina moessebergensis Assemblage. The W. matsushitai Zone corresponds to the Lejopyge armata trilobite Zone and is well correlated with the upper Series 3 conodont biozones of the Westergaardodina matsushitai-Westergaardodina grandidens Zone of South China and the Westergaardodina matsushitai Zone of North China, respectively. The present data allow a useful correlation to China and Baltica in relation to new subdivision of the Cambrian. Furnishina leei n. sp. is newly described.
基金supported by the Chinese Academy of Sciences(Grant Nos.XDB26000000,XDB10010100)the Ministry of Science and Technology of China(Grant Nos.2013FY111000,2017ZX05036-001-004)+1 种基金the National Natural Science Foundation of China(Grant No.41772005)IGCP project 653’The Onset of the Great Ordovician Biodiversification Event’.
文摘The originations of marine planktons and nektons are significantly delayed than that of benthos,as evidenced by the fossil record.The Cambrian Explosion produced a variety of high-level marine organisms,and many remarkablebody-plans.However,a majority of these organisms are benthic or level-bottomed,and are rather dependent on the substrates of sea floors.
