Abstract. Salvinia pseudoformosa has been established as a Miocene species based mainly on specimens collected from the Sasakizawa River, Numata, Hokkaido, Japan. However, both Eocene and Miocene sediments are distributed within this area. In this study, we conducted geological surveys along the Sasakizawa River to identify the stratigraphic horizon bearing S. pseudoformosa and found that S. pseudoformosa occurs from the middle Eocene Itarakaomappu Formation of the Uryu Group. We also reexamined syntypes of this species and concluded that only those from the Sasakizawa River can be identified as S. pseudoformosa with certainty. Therefore, we designated a syntype from the Sasakizawa River as the lectotype. Although we could not specify the exact localities of the lectotype and remaining syntypes from the Sasakizawa River, lithological characters of the slabs containing these specimens indicate their occurrence from the Uryu Group. Salvinia pseudoformosa has been recorded from the middle Miocene in Japan and Korea, but the venation patterns of these specimens differ from those of S. pseudoformosa.
{"title":"Revision of Salvinia pseudoformosa Type Specimen Ages","authors":"M. Nishino, Y. Ito, T. Yamada","doi":"10.2517/PR200053","DOIUrl":"https://doi.org/10.2517/PR200053","url":null,"abstract":"Abstract. Salvinia pseudoformosa has been established as a Miocene species based mainly on specimens collected from the Sasakizawa River, Numata, Hokkaido, Japan. However, both Eocene and Miocene sediments are distributed within this area. In this study, we conducted geological surveys along the Sasakizawa River to identify the stratigraphic horizon bearing S. pseudoformosa and found that S. pseudoformosa occurs from the middle Eocene Itarakaomappu Formation of the Uryu Group. We also reexamined syntypes of this species and concluded that only those from the Sasakizawa River can be identified as S. pseudoformosa with certainty. Therefore, we designated a syntype from the Sasakizawa River as the lectotype. Although we could not specify the exact localities of the lectotype and remaining syntypes from the Sasakizawa River, lithological characters of the slabs containing these specimens indicate their occurrence from the Uryu Group. Salvinia pseudoformosa has been recorded from the middle Miocene in Japan and Korea, but the venation patterns of these specimens differ from those of S. pseudoformosa.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49513847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Kinoshita, Quan Wang, A. Kuroyanagi, M. Murayama, Y. Ujiié, H. Kawahata
Abstract. Ocean acidification is now progressing, primarily due to the fact that the oceans have absorbed about 50% of the anthropogenic CO2 emitted since the industrial revolution. Many marine calcifying organisms, such as foraminifers and coccoliths, are known to build their shells using carbonate ions present in the seawaters surrounding them. Carbonate saturation state has a crucial influence on foraminiferal calcification, and foraminiferal shell production is known to be sensitive to increase in ocean pCO2. Moreover, ocean warming is also progressing along with acidification. Therefore, both environmental changes could affect foraminiferal shell formation. However, the relationship between foraminiferal shell parameters (i.e., size, weight, volume, and density) and ocean pCO2 or sea surface temperature (SST), or both, remains unclear. In this study, we used fossil planktic foraminifer Globigerinoides ruber (white) in a late Quaternary sediment core (MD98-2196) from the East China Sea to investigate a relationship between the shell parameters and oceanographic properties estimated based on the proxies from the same core. The foraminiferal shells were scanned using high-resolution micro-X-ray computed tomography (MXCT) to determine shell volume and density. The results showed that the size-normalized weight and the size-normalized volume of the shell had a negative correlation with the SST and atmospheric pCO2. The negative correlation between weight/volume and atmospheric pCO2 agrees with the previous laboratory experiments and geological record during the Pliocene. However, the correlation between weight/volume and SST should be interpreted with caution because it might be an artifact due to the correlation between SST and atmospheric pCO2. On the other hand, shell density is only weakly or insignificantly correlated with SST and pCO2, suggesting that these environmental parameters do not exert any impact on shell density. Thus, future ocean acidification will negatively affect the carbonate productivity of planktic foraminifers, even if it will not affect shell density. The temperature effect on the shell formation of the planktic foraminifers might be much less than ocean acidification considering controversial results of the temperature sensitivity in previous studies.
{"title":"Response of Planktic Foraminiferal Shells to Ocean Acidification and Global Warming Assessed Using Micro-X-Ray Computed Tomography","authors":"S. Kinoshita, Quan Wang, A. Kuroyanagi, M. Murayama, Y. Ujiié, H. Kawahata","doi":"10.2517/PR200043","DOIUrl":"https://doi.org/10.2517/PR200043","url":null,"abstract":"Abstract. Ocean acidification is now progressing, primarily due to the fact that the oceans have absorbed about 50% of the anthropogenic CO2 emitted since the industrial revolution. Many marine calcifying organisms, such as foraminifers and coccoliths, are known to build their shells using carbonate ions present in the seawaters surrounding them. Carbonate saturation state has a crucial influence on foraminiferal calcification, and foraminiferal shell production is known to be sensitive to increase in ocean pCO2. Moreover, ocean warming is also progressing along with acidification. Therefore, both environmental changes could affect foraminiferal shell formation. However, the relationship between foraminiferal shell parameters (i.e., size, weight, volume, and density) and ocean pCO2 or sea surface temperature (SST), or both, remains unclear. In this study, we used fossil planktic foraminifer Globigerinoides ruber (white) in a late Quaternary sediment core (MD98-2196) from the East China Sea to investigate a relationship between the shell parameters and oceanographic properties estimated based on the proxies from the same core. The foraminiferal shells were scanned using high-resolution micro-X-ray computed tomography (MXCT) to determine shell volume and density. The results showed that the size-normalized weight and the size-normalized volume of the shell had a negative correlation with the SST and atmospheric pCO2. The negative correlation between weight/volume and atmospheric pCO2 agrees with the previous laboratory experiments and geological record during the Pliocene. However, the correlation between weight/volume and SST should be interpreted with caution because it might be an artifact due to the correlation between SST and atmospheric pCO2. On the other hand, shell density is only weakly or insignificantly correlated with SST and pCO2, suggesting that these environmental parameters do not exert any impact on shell density. Thus, future ocean acidification will negatively affect the carbonate productivity of planktic foraminifers, even if it will not affect shell density. The temperature effect on the shell formation of the planktic foraminifers might be much less than ocean acidification considering controversial results of the temperature sensitivity in previous studies.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43371070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. A taxonomic revision of the ammonoid assemblage previously reported from the Osawa Formation at Akaushi in the Motoyoshi area, i.e., Columbites parisianus, Subcolumbites perrinismithi and Eophyllites cf. dieneri, leads to the conclusion that the fauna should be attributed to Hellenites tchernyschewiensis, H. inopinatus, Neocolumbites grammi, N. insignis, Procolumbites ussuriensis and P. subquadratus. In addition, this fauna also includes Deweveria kovalenkoi. Because these ammonoids are characteristic of the N. insignis Zone of South Primorye, Russian Far East, the lowest part of the Osawa Formation clearly correlates with the upper part of the lower Spathian (upper Olenekian, Lower Triassic), and the faunal similarity suggests that the South Kitakami Belt may have been located near South Primorye on the western side of the Panthalassa.
{"title":"Revision of Early Spathian (Late Olenekian, Early Triassic) Ammonoids from the Osawa Formation at Akaushi in the Motoyoshi Area, South Kitakami Belt, Northeast Japan","authors":"Y. Shigeta","doi":"10.2517/PR210003","DOIUrl":"https://doi.org/10.2517/PR210003","url":null,"abstract":"Abstract. A taxonomic revision of the ammonoid assemblage previously reported from the Osawa Formation at Akaushi in the Motoyoshi area, i.e., Columbites parisianus, Subcolumbites perrinismithi and Eophyllites cf. dieneri, leads to the conclusion that the fauna should be attributed to Hellenites tchernyschewiensis, H. inopinatus, Neocolumbites grammi, N. insignis, Procolumbites ussuriensis and P. subquadratus. In addition, this fauna also includes Deweveria kovalenkoi. Because these ammonoids are characteristic of the N. insignis Zone of South Primorye, Russian Far East, the lowest part of the Osawa Formation clearly correlates with the upper part of the lower Spathian (upper Olenekian, Lower Triassic), and the faunal similarity suggests that the South Kitakami Belt may have been located near South Primorye on the western side of the Panthalassa.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43077296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Fusuline biostratigraphy and faunal composition of the upper part the Ichinotani Formation and lower part of the Mizuyagadani Formation in the Fukuji area, central Japan are reexamined and compared to those of previous works. The upper part of the Upper Member of the Ichinotani Formation is composed mainly of the upper Kasimovian and lower Gzhelian strata, and is characterized by the partial reappearance of Moscovian strata dominant in the lower part of the Upper Member, suggesting a more complicated geological structure of the formation than previously assumed. Fusulines apparently correlatable to the middle part of the Kasimovian have not been found in the Fukuji area. The species Carbonoschwagerina morikawai is restricted to the lower part of the Mizuyagadani Formation. Faunal composition and correlation of age-diagnostic fusuline species are reviewed paleobiogeographically between the Fukuji and other areas especially of the Akiyoshi Limestone. Described herein are two species of non-fusuline foraminifers and nine species of fusulines including Montiparus japonicus sp. nov.
{"title":"Late Carboniferous (Kasimovian and Gzhelian) Fusulines of the Ichinotani and Mizuyagadani Formations in the Fukuji Area, Hida Marginal Terrane, Central Japan","authors":"F. Kobayashi","doi":"10.2517/PR200051","DOIUrl":"https://doi.org/10.2517/PR200051","url":null,"abstract":"Abstract. Fusuline biostratigraphy and faunal composition of the upper part the Ichinotani Formation and lower part of the Mizuyagadani Formation in the Fukuji area, central Japan are reexamined and compared to those of previous works. The upper part of the Upper Member of the Ichinotani Formation is composed mainly of the upper Kasimovian and lower Gzhelian strata, and is characterized by the partial reappearance of Moscovian strata dominant in the lower part of the Upper Member, suggesting a more complicated geological structure of the formation than previously assumed. Fusulines apparently correlatable to the middle part of the Kasimovian have not been found in the Fukuji area. The species Carbonoschwagerina morikawai is restricted to the lower part of the Mizuyagadani Formation. Faunal composition and correlation of age-diagnostic fusuline species are reviewed paleobiogeographically between the Fukuji and other areas especially of the Akiyoshi Limestone. Described herein are two species of non-fusuline foraminifers and nine species of fusulines including Montiparus japonicus sp. nov.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48425086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Sashida, Tsuyoshi Ito, Panus Hong, Yuichi Fukushima, Sachiko Agematsu, S. Salyapongse, P. Putthapiban
Abstract. A bedded chert succession, intercalated with layers of coarse-grained sandstone and chert conglomerate, and a limestone block with a long axis of about 10 m are distributed in the Ban Rai area, southwestern Uthai Thani, central Thailand. The chert yielded early Carboniferous (Tournaisian to Visean) radiolarians composed of 10 species of five genera; the limestone yielded Middle Triassic (early Anisian) conodonts comprising five species (P1 element). The lower Carboniferous chert was presumably deposited on the upper continental rise of the Sibumasu Terrane in the Paleotethys Ocean, based on radiolarian faunal characteristics. The Middle Triassic limestone was probably deposited on the continental shelf of the eastern margin of the Sibumasu Terrane, judging from the inclusion of silt-sized quartz grains. Because the blocks of the lower Carboniferous chert and Middle Triassic limestone are currently located in a narrow area, these blocks are inferred to have been mixed with each other by submarine sliding after at least the Middle Triassic at the eastern margin of the Sibumasu Terrane.
{"title":"Occurrence of Early Carboniferous Radiolarians and Middle Triassic Conodonts from Ban Rai, Southwestern Uthai Thani, Central Thailand and Its Geological Significance","authors":"K. Sashida, Tsuyoshi Ito, Panus Hong, Yuichi Fukushima, Sachiko Agematsu, S. Salyapongse, P. Putthapiban","doi":"10.2517/PR200056","DOIUrl":"https://doi.org/10.2517/PR200056","url":null,"abstract":"Abstract. A bedded chert succession, intercalated with layers of coarse-grained sandstone and chert conglomerate, and a limestone block with a long axis of about 10 m are distributed in the Ban Rai area, southwestern Uthai Thani, central Thailand. The chert yielded early Carboniferous (Tournaisian to Visean) radiolarians composed of 10 species of five genera; the limestone yielded Middle Triassic (early Anisian) conodonts comprising five species (P1 element). The lower Carboniferous chert was presumably deposited on the upper continental rise of the Sibumasu Terrane in the Paleotethys Ocean, based on radiolarian faunal characteristics. The Middle Triassic limestone was probably deposited on the continental shelf of the eastern margin of the Sibumasu Terrane, judging from the inclusion of silt-sized quartz grains. Because the blocks of the lower Carboniferous chert and Middle Triassic limestone are currently located in a narrow area, these blocks are inferred to have been mixed with each other by submarine sliding after at least the Middle Triassic at the eastern margin of the Sibumasu Terrane.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46766095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The discovery of the heteromorph ammonoid Amapondella amapondense (van Hoepen) in the lower middle Campanian in the Urakawa, Biratori and Hidaka areas of Hokkaido, northern Japan, represents the first report of this taxon in the Northwest Pacific region. Because the species flourished in other regions during Santonian to early Campanian time, its final geographic occurrence in Hokkaido suggests that global environmental changes likely had a significant influence on ammonoid biogeography during early middle Campanian time.
{"title":"Discovery of the Heteromorph Ammonoid Amapondella amapondense in the Middle Campanian of Hokkaido, Japan","authors":"Y. Shigeta, Masataka Izukura","doi":"10.2517/PR210007","DOIUrl":"https://doi.org/10.2517/PR210007","url":null,"abstract":"Abstract. The discovery of the heteromorph ammonoid Amapondella amapondense (van Hoepen) in the lower middle Campanian in the Urakawa, Biratori and Hidaka areas of Hokkaido, northern Japan, represents the first report of this taxon in the Northwest Pacific region. Because the species flourished in other regions during Santonian to early Campanian time, its final geographic occurrence in Hokkaido suggests that global environmental changes likely had a significant influence on ammonoid biogeography during early middle Campanian time.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49369014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Shimada, Megumi Saito-Kato, R. Jenkins, M. Yamasaki, Yuichiro Tanaka, Y. Hikida
Abstract. Well-preserved marine diatoms are documented for the first time from authigenic carbonate rocks induced by cold methane (hydrocarbon) seepage in the Omagari Formation (latest Santonian to earliest Campanian in age, Late Cretaceous Epoch; around 83.6 Ma) of the upper part of the Yezo Group in the Teshio-Nakagawa area, northern Hokkaido (northern Japan). The diatom flora is rich in species of Hemiaulus and Triceratium, associated with a few other extinct diatom genera. An araphid genus (Sceptroneis) was also observed; this is one of the earliest fossil records of “pennate” (Bacillariophyceae) diatoms. Although valve ultrastructures have been mostly dissolved, the preservation of these diatoms is much better than that in the few previous reports of Cretaceous siliceous photosynthetic organisms from Japan and adjacent regions in the northwestern Pacific Ocean. Because of their common generic composition in the mid- to high-latitude regions in both hemispheres, diatoms are suggested to have experienced a global radiation by early Campanian time. Thus, our diatom records provide insights into the Late Cretaceous floral adaptive radiation around the northwestern Pacific margin, where the radiation history of diatoms is yet unclear. As Gladius antiquus was confirmed but Basilicostephanus species were absent from the present material, the flora from the Teshio-Nakagawa area is tentatively regarded as belonging to the G. antiquus Concurrent Range Zone, an interval extending from an undetermined Late Cretaceous Epoch to the latest Santonian Age. However, this floral correlation is inaccurate because our materials are latest Santonian to earliest Campanian in age, as dated by the molluscan (ammonoids and inoceramids) biostratigraphy. Hence, further research is required to clarify the sensitivity of different chronological proxies and the stratigraphic ranges of age-diagnostic diatoms in different geographic provinces.
{"title":"Late Cretaceous Diatoms (Bacillariophyta) from the Teshio-Nakagawa Area, Hokkaido, Northern Japan: Significance for Their Origin and Biostratigraphy","authors":"C. Shimada, Megumi Saito-Kato, R. Jenkins, M. Yamasaki, Yuichiro Tanaka, Y. Hikida","doi":"10.2517/PR200029","DOIUrl":"https://doi.org/10.2517/PR200029","url":null,"abstract":"Abstract. Well-preserved marine diatoms are documented for the first time from authigenic carbonate rocks induced by cold methane (hydrocarbon) seepage in the Omagari Formation (latest Santonian to earliest Campanian in age, Late Cretaceous Epoch; around 83.6 Ma) of the upper part of the Yezo Group in the Teshio-Nakagawa area, northern Hokkaido (northern Japan). The diatom flora is rich in species of Hemiaulus and Triceratium, associated with a few other extinct diatom genera. An araphid genus (Sceptroneis) was also observed; this is one of the earliest fossil records of “pennate” (Bacillariophyceae) diatoms. Although valve ultrastructures have been mostly dissolved, the preservation of these diatoms is much better than that in the few previous reports of Cretaceous siliceous photosynthetic organisms from Japan and adjacent regions in the northwestern Pacific Ocean. Because of their common generic composition in the mid- to high-latitude regions in both hemispheres, diatoms are suggested to have experienced a global radiation by early Campanian time. Thus, our diatom records provide insights into the Late Cretaceous floral adaptive radiation around the northwestern Pacific margin, where the radiation history of diatoms is yet unclear. As Gladius antiquus was confirmed but Basilicostephanus species were absent from the present material, the flora from the Teshio-Nakagawa area is tentatively regarded as belonging to the G. antiquus Concurrent Range Zone, an interval extending from an undetermined Late Cretaceous Epoch to the latest Santonian Age. However, this floral correlation is inaccurate because our materials are latest Santonian to earliest Campanian in age, as dated by the molluscan (ammonoids and inoceramids) biostratigraphy. Hence, further research is required to clarify the sensitivity of different chronological proxies and the stratigraphic ranges of age-diagnostic diatoms in different geographic provinces.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49311347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The holotype of Iwakiella ichiroi Hatai, Kotaka and Noda, 1972, from the Permian Kashiwadaira Member of Northeast Japan is reexamined. Although previously placed within the Tentaculitoidea or retained in the Problematica, the possession of the septum and the spherical shape of the initial chamber suggest that this specimen belongs to sphaerorthoceratid orthocerid of the Cephalopoda. The present result confirms that the Tentaculitoidea probably became extinct near the Carboniferous – Permian boundary with Hidagaienites arcuatus Niko, 2000, as the latest representative.
{"title":"Reexamination of a Permian Tentaculites-Like Fossil Iwakiella ichiroi Hatai, Kotaka and Noda, 1972, as an Orthocerid Cephalopod","authors":"S. Niko","doi":"10.2517/PR200010","DOIUrl":"https://doi.org/10.2517/PR200010","url":null,"abstract":"Abstract. The holotype of Iwakiella ichiroi Hatai, Kotaka and Noda, 1972, from the Permian Kashiwadaira Member of Northeast Japan is reexamined. Although previously placed within the Tentaculitoidea or retained in the Problematica, the possession of the septum and the spherical shape of the initial chamber suggest that this specimen belongs to sphaerorthoceratid orthocerid of the Cephalopoda. The present result confirms that the Tentaculitoidea probably became extinct near the Carboniferous – Permian boundary with Hidagaienites arcuatus Niko, 2000, as the latest representative.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48779079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Ishida, Hisanori Kohtsuka, Masao Kiyomoto, T. Fujita
Abstract. The star-shaped trace fossil Asteriacites lumbricalis is produced by ophiuroids and has two different forms. One form has four distinct arms with transverse fine and parallel striations and one indistinct arm without striations, and the producing process has been studied already. In this study, we clarified the producing process of another form with five distinct radiating arms and fine striations by aquarium observations of extant ophiuroids. The form was produced when ophiuroids were covered with a thin sand layer (11–39% of the arm length in thickness). After covered by thin sand, ophiuroids raised their five arms with one to five tips protruded vertically above the sand cover, raised and slanted the disc in the sand, and then obliquely emerged onto the sand cover. Finally, they returned to horizontal postures creeping on the sand. The trace left on the substratum was very similar in shape to the trace fossil from Hettangian (Lower Jurassic) in Blumenrod, Germany. The producing process of the repetitive multiple traces of A. lumbricalis was revealed by aquarium observations. When an ophiuroid was alternately covered with a thin sand layer and then with a thin abrasive layer as mud substratum, the ophiuroid left a vertically stacked series of traces which gradually shifted the horizontal position. This unique form of A. lumbricalis was produced by escaping of ophiuroids from successive deposition events.
{"title":"Producing Processes of the Trace Fossil Asteriacites lumbricalis Revisited: Different Ophiuroid Behaviors Produce Different Trace Forms","authors":"Y. Ishida, Hisanori Kohtsuka, Masao Kiyomoto, T. Fujita","doi":"10.2517/PR200042","DOIUrl":"https://doi.org/10.2517/PR200042","url":null,"abstract":"Abstract. The star-shaped trace fossil Asteriacites lumbricalis is produced by ophiuroids and has two different forms. One form has four distinct arms with transverse fine and parallel striations and one indistinct arm without striations, and the producing process has been studied already. In this study, we clarified the producing process of another form with five distinct radiating arms and fine striations by aquarium observations of extant ophiuroids. The form was produced when ophiuroids were covered with a thin sand layer (11–39% of the arm length in thickness). After covered by thin sand, ophiuroids raised their five arms with one to five tips protruded vertically above the sand cover, raised and slanted the disc in the sand, and then obliquely emerged onto the sand cover. Finally, they returned to horizontal postures creeping on the sand. The trace left on the substratum was very similar in shape to the trace fossil from Hettangian (Lower Jurassic) in Blumenrod, Germany. The producing process of the repetitive multiple traces of A. lumbricalis was revealed by aquarium observations. When an ophiuroid was alternately covered with a thin sand layer and then with a thin abrasive layer as mud substratum, the ophiuroid left a vertically stacked series of traces which gradually shifted the horizontal position. This unique form of A. lumbricalis was produced by escaping of ophiuroids from successive deposition events.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46944434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. New tarsals (astragalus and entocuneiform) of fossil pinnipeds from the lower Miocene (Burdigalian) Oi Formation in Mie Prefecture, Japan, belonging to early pinnipedimorphs (i.e., enaliarctines or basal odobenids) and cf. Odobenidae gen. et sp. indet. were discovered. A comparison of early pinnipedimorph astragali conclusively indicated that at least three species were represented in the western North Pacific during the early Miocene (Burdigalian). Early pinnipedimorphs clearly showed considerable diversification in the eastern North Pacific during the early Miocene, and our study demonstrates that the early pinnipedimorphs in the western North Pacific also started to diversify around the same time.
{"title":"Tarsals of Early Pinnipedimorphs (Mammalia: Carnivora) from the Lower Miocene, Japan, and Their Early Diversity in the Western North Pacific","authors":"Wataru Tonomori, H. Taru","doi":"10.2517/PR200030","DOIUrl":"https://doi.org/10.2517/PR200030","url":null,"abstract":"Abstract. New tarsals (astragalus and entocuneiform) of fossil pinnipeds from the lower Miocene (Burdigalian) Oi Formation in Mie Prefecture, Japan, belonging to early pinnipedimorphs (i.e., enaliarctines or basal odobenids) and cf. Odobenidae gen. et sp. indet. were discovered. A comparison of early pinnipedimorph astragali conclusively indicated that at least three species were represented in the western North Pacific during the early Miocene (Burdigalian). Early pinnipedimorphs clearly showed considerable diversification in the eastern North Pacific during the early Miocene, and our study demonstrates that the early pinnipedimorphs in the western North Pacific also started to diversify around the same time.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":null,"pages":null},"PeriodicalIF":0.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49455644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：