Abstract. Linguliformean brachiopods often exhibit a clustered occurrence. Because there has been no detailed analysis of whether these clusters represent death or living assemblages, we exemplified the burial processes of the Middle Permian discinid brachiopods from the Hoso-o Formation with the systematic descriptions of Orbiculoidea verum sp. nov. and Discinidae gen. et sp. indet. There were three types of discinid occurrences: 1) articulated Orbiculoidea in a ventral-side-down orientation, 2) disarticulated valves of both species in a convex-up orientation, and 3) disarticulated ventral valves of the Orbiculoidea in a convex-down orientation. The articulated specimens occurred in laminated mudstone and must have been autochthonous, while the disarticulated specimens with a convex-up orientation were para-autochthonous, resulting from turbiditic or storm flow. The specimens with convex-down ventral valves always occurred at the base of the sandstone beds with their ventral apexes slightly penetrating the underlying mudstone. This is the argument for an autochthonous ventral valve, whereby only the dorsal valve was transported after death. The distribution of epibionts suggests that the life posture of the Orbiculoidea was a ventral-side-down orientation, with its anterior half slightly higher than the sediment-water interface, which was advantageous for the feeding flow and the clearance of sediments around the posterior margin. Although dense monospecific assemblages of Orbiculoidea occur only as disarticulated valves, the exclusive occurrence of articulated individuals in the underlying mudstone suggest that the animal inhabited the specific environments opportunistically, which has never been explored in other fossilised organisms.
摘要林古利形目腕足类动物经常出现集群。由于还没有详细分析这些集群是代表死亡还是活的组合，我们通过对Orbiculoidea verum sp.nov.和Discinidae gen.et sp.indet的系统描述，举例说明了Hoso-o组中二叠纪盘状腕足类的埋葬过程。椎间盘状突起有三种类型：1）腹侧朝下的有关节Orbiculoide，2）两个物种的瓣叶均呈凸向上的无关节，3）腹侧瓣叶呈凸向下的无关节。铰接标本出现在层状泥岩中，一定是本地的，而凸起向上的非铰接标本是准本地的，由浊积流或风暴流引起。腹瓣向下凸起的标本通常出现在砂岩层的底部，其腹尖略穿透下伏的泥岩。这就是本地腹侧瓣膜的论点，即死亡后只有背侧瓣膜被运输。表生生物的分布表明，Orbiculoide的生活姿态是腹侧向下的，其前半部分略高于沉积物-水界面，这有利于进食流和清除后缘周围的沉积物。尽管密集的单特异性Orbiculidea组合仅以无关节瓣膜的形式出现，但在下层泥岩中只出现有关节个体，这表明该动物是机会主义地生活在特定环境中，而在其他化石生物中从未探索过这一点。
{"title":"Death or Living Assemblage? The Middle Permian Discinid Brachiopods in the Kamiyasse Area, Southern Kitakami Mountains, Northeastern Japan","authors":"Masao Masunaga, Y. Shiino","doi":"10.2517/2020PR023","DOIUrl":"https://doi.org/10.2517/2020PR023","url":null,"abstract":"Abstract. Linguliformean brachiopods often exhibit a clustered occurrence. Because there has been no detailed analysis of whether these clusters represent death or living assemblages, we exemplified the burial processes of the Middle Permian discinid brachiopods from the Hoso-o Formation with the systematic descriptions of Orbiculoidea verum sp. nov. and Discinidae gen. et sp. indet. There were three types of discinid occurrences: 1) articulated Orbiculoidea in a ventral-side-down orientation, 2) disarticulated valves of both species in a convex-up orientation, and 3) disarticulated ventral valves of the Orbiculoidea in a convex-down orientation. The articulated specimens occurred in laminated mudstone and must have been autochthonous, while the disarticulated specimens with a convex-up orientation were para-autochthonous, resulting from turbiditic or storm flow. The specimens with convex-down ventral valves always occurred at the base of the sandstone beds with their ventral apexes slightly penetrating the underlying mudstone. This is the argument for an autochthonous ventral valve, whereby only the dorsal valve was transported after death. The distribution of epibionts suggests that the life posture of the Orbiculoidea was a ventral-side-down orientation, with its anterior half slightly higher than the sediment-water interface, which was advantageous for the feeding flow and the clearance of sediments around the posterior margin. Although dense monospecific assemblages of Orbiculoidea occur only as disarticulated valves, the exclusive occurrence of articulated individuals in the underlying mudstone suggest that the animal inhabited the specific environments opportunistically, which has never been explored in other fossilised organisms.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"258 - 278"},"PeriodicalIF":0.9,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43774887","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 stratigraphic distribution and modes of occurrence of Early Triassic Bellerophontoidea (Gastropoda) are studied at seven sections in South Primorye, Russian Far East, where depositional environments ranging from nonmarine, shoreface, to distal basin plain settings are recorded. Warthia zakharovi and Dicellonema abrekensis are abundant in Induan (Griesbachian and Dienerian) fine- to medium-grained, hummocky cross-stratified (HCS) sandstone beds occasionally intercalated with wavy-mudstone layers, whereas they are absent in coarser-grained cross-stratified successions. This observation suggests that bellerophontoids inhabited a lower shoreface environment above the storm wave base and possibly an inner shelf environment as well during this particular stage. Olenekian (Smithian and Spathian) bellerophontoids have not been found in the storm-induced sandstone beds, but W. zakharovi occurs in the lower Smithian sandstone beds of distal turbidites intercalated in the laminated mudstone. This mode of occurrence strongly suggests that W. zakharovi inhabited a deeper environment than lower shoreface, most probably an inner shelf environment, and after death, its shells were transported from their habitat to the basin-floor by sediment gravity flow. Bellerophontoids have not been found in middle Smithian and younger strata in South Primorye, and the timing of this disappearance is synchronous with other areas of the world. Bellerophontoids were distributed over wide-ranging areas from the equator to the high latitudes during Induan time, but they disappeared from the lower latitude areas and the shallower marine environments of middle latitude South Primorye during the early Smithian, before eventually becoming extinct during middle Smithian time. Such a step-by-step demise strongly implies that the severe global warming and related harmful events that occurred during the Smithian may have had a serious effect on bellerophontoids. The extinction of Bellerophontoidea before the beginning of the late Smithian suggests that the group may have been more sensitive to global warming and related harmful events than other organisms.
{"title":"Timing of Bellerophontoid (Gastropoda) Demise in the Early Triassic of South Primorye, Russian Far East","authors":"Y. Shigeta, Taro Kumagae, Y. Zakharov, A. Popov","doi":"10.2517/2020PR020","DOIUrl":"https://doi.org/10.2517/2020PR020","url":null,"abstract":"Abstract. The stratigraphic distribution and modes of occurrence of Early Triassic Bellerophontoidea (Gastropoda) are studied at seven sections in South Primorye, Russian Far East, where depositional environments ranging from nonmarine, shoreface, to distal basin plain settings are recorded. Warthia zakharovi and Dicellonema abrekensis are abundant in Induan (Griesbachian and Dienerian) fine- to medium-grained, hummocky cross-stratified (HCS) sandstone beds occasionally intercalated with wavy-mudstone layers, whereas they are absent in coarser-grained cross-stratified successions. This observation suggests that bellerophontoids inhabited a lower shoreface environment above the storm wave base and possibly an inner shelf environment as well during this particular stage. Olenekian (Smithian and Spathian) bellerophontoids have not been found in the storm-induced sandstone beds, but W. zakharovi occurs in the lower Smithian sandstone beds of distal turbidites intercalated in the laminated mudstone. This mode of occurrence strongly suggests that W. zakharovi inhabited a deeper environment than lower shoreface, most probably an inner shelf environment, and after death, its shells were transported from their habitat to the basin-floor by sediment gravity flow. Bellerophontoids have not been found in middle Smithian and younger strata in South Primorye, and the timing of this disappearance is synchronous with other areas of the world. Bellerophontoids were distributed over wide-ranging areas from the equator to the high latitudes during Induan time, but they disappeared from the lower latitude areas and the shallower marine environments of middle latitude South Primorye during the early Smithian, before eventually becoming extinct during middle Smithian time. Such a step-by-step demise strongly implies that the severe global warming and related harmful events that occurred during the Smithian may have had a serious effect on bellerophontoids. The extinction of Bellerophontoidea before the beginning of the late Smithian suggests that the group may have been more sensitive to global warming and related harmful events than other organisms.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"246 - 257"},"PeriodicalIF":0.9,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41910692","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}
Katsunori Iizumi, H. Ando, Kunihiro Suzuki, Yoshiki Koda
Abstract. We describe two well-preserved mandibles of Stegolophodon pseudolatidens (Mammalia, Proboscidea, Stegodontidae) discovered from the lower Miocene (ca. 16.9–16.6 Ma) in Northeast Japan. The mandible of Sl. pseudolatidens is primitive within the Stegodontidae in having a short symphysis with lower tusks, tetralophodont lower molars, and a mandibular canal with the large dorsoventral diameter in the anterior segment. It is characterized by a perpendicular mandibular ramus (forming an almost right angle between the anterior margin of the mandibular ramus and the dorsal horizontal surface of the corpus), and many scratches in mesial direction on the occlusal surface of m3, implying that Sl. pseudolatidens appears to have acquired a proal jaw movement during mastication. While the mandibular morphology of Sl. pseudolatidens is comparable to that of other species of the genus that of Stegolophodon cf. stegodontoides from the upper Miocene of Myanmar differs from that of these species in having a shorter symphysis, which is a derived condition.
{"title":"Mandibular Morphology of Stegolophodon pseudolatidens (Proboscidea, Stegodontidae) from the Lower Miocene of Japan","authors":"Katsunori Iizumi, H. Ando, Kunihiro Suzuki, Yoshiki Koda","doi":"10.2517/2020PR025","DOIUrl":"https://doi.org/10.2517/2020PR025","url":null,"abstract":"Abstract. We describe two well-preserved mandibles of Stegolophodon pseudolatidens (Mammalia, Proboscidea, Stegodontidae) discovered from the lower Miocene (ca. 16.9–16.6 Ma) in Northeast Japan. The mandible of Sl. pseudolatidens is primitive within the Stegodontidae in having a short symphysis with lower tusks, tetralophodont lower molars, and a mandibular canal with the large dorsoventral diameter in the anterior segment. It is characterized by a perpendicular mandibular ramus (forming an almost right angle between the anterior margin of the mandibular ramus and the dorsal horizontal surface of the corpus), and many scratches in mesial direction on the occlusal surface of m3, implying that Sl. pseudolatidens appears to have acquired a proal jaw movement during mastication. While the mandibular morphology of Sl. pseudolatidens is comparable to that of other species of the genus that of Stegolophodon cf. stegodontoides from the upper Miocene of Myanmar differs from that of these species in having a shorter symphysis, which is a derived condition.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"279 - 297"},"PeriodicalIF":0.9,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46678837","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. We report a single whale bone associated with many molluscan fossils from the Omma Formation, Lower Pleistocene shallow marine deposits, along the Sai-gawa River, Kanazawa City, in central Japan. Most molluscan species which are commonly found in the Omma Formation show disarticulated and/or damaged shells, indicating semi-autochthonous or allochthonous modes of occurrence. However, the assemblage contained chemosynthetic bivalves, such as lucinid, solemyid and thyasirid bivalves, which are rare in the Omma Formation. The lucinids and solemyids show a high articulation ratio, along with some predatory and scavenging gastropods, such as naticids, nassariids and borsoniids whose well-preserved shells indicate an autochthonous mode of occurrence. In addition, most of the lucinid bivalves show an umbo-upward position similar to the life position of Recent species. Recent lucinid, solemyid and most thyasirid bivalves harbor chemosymbiotic bacteria in their gills and are well known members of the chemosynthetic community. These lines of evidence indicate that the community, mainly comprising lucinid bivalves and other autochthonous molluscan species associated with the whale bone, is an ancient whale-fall community. This shallowest fossil whale-fall community differs from deep-water cases in the dominance of infaunal bivalves, such as lucinids, and in the lack of epifaunal and semi-infaunal chemosynthetic bivalves, such as bathymodiolins and vesicomyids. This community supports a previous suggestion that the difference in characteristic species of the whale-fall communities depends on the water depth.
{"title":"Pleistocene Shallow-Water Whale-Fall Community from the Omma Formation in Central Japan","authors":"A. Seki, R. Jenkins","doi":"10.2517/2020PR024","DOIUrl":"https://doi.org/10.2517/2020PR024","url":null,"abstract":"Abstract. We report a single whale bone associated with many molluscan fossils from the Omma Formation, Lower Pleistocene shallow marine deposits, along the Sai-gawa River, Kanazawa City, in central Japan. Most molluscan species which are commonly found in the Omma Formation show disarticulated and/or damaged shells, indicating semi-autochthonous or allochthonous modes of occurrence. However, the assemblage contained chemosynthetic bivalves, such as lucinid, solemyid and thyasirid bivalves, which are rare in the Omma Formation. The lucinids and solemyids show a high articulation ratio, along with some predatory and scavenging gastropods, such as naticids, nassariids and borsoniids whose well-preserved shells indicate an autochthonous mode of occurrence. In addition, most of the lucinid bivalves show an umbo-upward position similar to the life position of Recent species. Recent lucinid, solemyid and most thyasirid bivalves harbor chemosymbiotic bacteria in their gills and are well known members of the chemosynthetic community. These lines of evidence indicate that the community, mainly comprising lucinid bivalves and other autochthonous molluscan species associated with the whale bone, is an ancient whale-fall community. This shallowest fossil whale-fall community differs from deep-water cases in the dominance of infaunal bivalves, such as lucinids, and in the lack of epifaunal and semi-infaunal chemosynthetic bivalves, such as bathymodiolins and vesicomyids. This community supports a previous suggestion that the difference in characteristic species of the whale-fall communities depends on the water depth.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"191 - 200"},"PeriodicalIF":0.9,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46375293","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}
Masamichi Takahashi, P. Herendeen, Fabiany Herrera, R. Hirayama, H. Ando, Kazuhisa Sasaki, P. Crane
Abstract. A preliminary description is provided of a new assemblage of small, three-dimensional and charcoalified mesofossils from the Tamagawa Formation (late Turonian–middle Santonian; Upper Cretaceous) of the Kuji Group in northeastern Japan. The new mesofossils yield excellent structural details and include well-preserved circinate shoots of ferns together with conifer leafy-shoots, seeds and probable pollen cones, and variety of angiosperm fruits and seeds, including fruits of Cornales and seeds of Nymphaeales. The new mesofossil assemblage is complementary to the previously published macrofossil flora from the Kuji Group.
{"title":"A New Assemblage of Plant Mesofossils (Late Turonian–Middle Santonian; Upper Cretaceous) from the Tamagawa Formation, Kuji Group, in Northeastern Japan","authors":"Masamichi Takahashi, P. Herendeen, Fabiany Herrera, R. Hirayama, H. Ando, Kazuhisa Sasaki, P. Crane","doi":"10.2517/2020PR015","DOIUrl":"https://doi.org/10.2517/2020PR015","url":null,"abstract":"Abstract. A preliminary description is provided of a new assemblage of small, three-dimensional and charcoalified mesofossils from the Tamagawa Formation (late Turonian–middle Santonian; Upper Cretaceous) of the Kuji Group in northeastern Japan. The new mesofossils yield excellent structural details and include well-preserved circinate shoots of ferns together with conifer leafy-shoots, seeds and probable pollen cones, and variety of angiosperm fruits and seeds, including fruits of Cornales and seeds of Nymphaeales. The new mesofossil assemblage is complementary to the previously published macrofossil flora from the Kuji Group.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"120 - 126"},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42643834","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. Raususetarches sakurai gen. et sp. nov. is described from the late Miocene Koshikawa Formation in Kasuga, Rausu, Shiretoko Peninsula, Hokkaido, Japan based on several specimens found in the same rock, as a new genus and species. This new species belongs to the family Scorpaenidae of Scorpaenoidei in having short, triangular posterior spines of preopercle, two ridges and spines of opercle and the first pterygiophore of the anal fin inclined. This species belongs to the subfamily Setarchinae in having lateral line scales forming grooves and cycloid scales. This new species, however, differs from all other genera of the subfamily in having large triangular spines of preopercle; 14 spines and 13 soft rays of the dorsal fin; three spines and eight soft rays of the anal fin; 19 rays of the pectoral fin; hypurals 1 and 2 fused; and hypurals 3 and 4 are also fused. This is the first fossil species of the subfamily Setarchinae.
摘要Raususetarches sakurai gen. et sp. 11 .是根据在同一岩石中发现的几个标本，描述了日本北海道知子半岛饶州Kasuga的晚中新世Koshikawa组，作为一个新属和新种。这个新物种属于家庭Scorpaenidae Scorpaenoidei在短,三角后刺形质,两脊刺孔盖和第一鳍条臀鳍的倾向。本种在具有形成沟槽的侧线鳞片和摆线鳞片方面属于卷叶蛛亚科。这个新种，然而，不同于亚科的所有其他属的是具有大的前环的三角形刺;背鳍有14根刺和13条软鳍;三根刺和八根软鳍;胸鳍的19条射线;hypural 1和2融合;第三和第四支hypulals也融合在一起。这是蛛形亚科的第一个化石种。
{"title":"A New Miocene Scorpaenoid Fish, Raususetarches sakurai gen. et sp. nov. (Teleostei: Scorpaeniformes) from Rausu, Hokkaido, Japan","authors":"Yoshitaka Yabumoto, Mikhail V. Nazarkin","doi":"10.2517/2020PR013","DOIUrl":"https://doi.org/10.2517/2020PR013","url":null,"abstract":"Abstract. Raususetarches sakurai gen. et sp. nov. is described from the late Miocene Koshikawa Formation in Kasuga, Rausu, Shiretoko Peninsula, Hokkaido, Japan based on several specimens found in the same rock, as a new genus and species. This new species belongs to the family Scorpaenidae of Scorpaenoidei in having short, triangular posterior spines of preopercle, two ridges and spines of opercle and the first pterygiophore of the anal fin inclined. This species belongs to the subfamily Setarchinae in having lateral line scales forming grooves and cycloid scales. This new species, however, differs from all other genera of the subfamily in having large triangular spines of preopercle; 14 spines and 13 soft rays of the dorsal fin; three spines and eight soft rays of the anal fin; 19 rays of the pectoral fin; hypurals 1 and 2 fused; and hypurals 3 and 4 are also fused. This is the first fossil species of the subfamily Setarchinae.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"93 - 104"},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46397070","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. Biostratigraphy of conodonts is widely used for age assignment of Permian strata. In this paper, we report conodonts from the limestone of the Nabeyama Formation deposited on a pelagic seamount in Panthalassa, which is an oceanic realm where Permian conodont data are scarce compared to other oceanic realms. Samples collected from the lower part of the Nabeyama Formation yielded Mesogondolella idahoensis (Youngquist, Hawley and Miller) and Sweetognathus hanzhongensis (Wang), which indicate a late Kungurian age. Previous studies and fusulinids obtained in this study indicate that the studied samples belong to the Parafusulina yabei biozone. Therefore, the Parafusulina yabei Zone includes the uppermost Kungurian. Mesogondolella idahoensis and Sweetognathus hanzhongensis are respectively regarded as cool and warm water species. Hence, the distribution of cool and warm water conodont species may have overlapped in pelagic Panthalassa during the late Kungurian.
{"title":"Late Kungurian Conodonts of Pelagic Panthalassa from Seamount-Capping Limestone in Ogama, Kuzuu, Tochigi Prefecture, Japan","authors":"Shun Muto, Yohoko Okumura, Takeshi Mizuhara","doi":"10.2517/2020PR012","DOIUrl":"https://doi.org/10.2517/2020PR012","url":null,"abstract":"Abstract. Biostratigraphy of conodonts is widely used for age assignment of Permian strata. In this paper, we report conodonts from the limestone of the Nabeyama Formation deposited on a pelagic seamount in Panthalassa, which is an oceanic realm where Permian conodont data are scarce compared to other oceanic realms. Samples collected from the lower part of the Nabeyama Formation yielded Mesogondolella idahoensis (Youngquist, Hawley and Miller) and Sweetognathus hanzhongensis (Wang), which indicate a late Kungurian age. Previous studies and fusulinids obtained in this study indicate that the studied samples belong to the Parafusulina yabei biozone. Therefore, the Parafusulina yabei Zone includes the uppermost Kungurian. Mesogondolella idahoensis and Sweetognathus hanzhongensis are respectively regarded as cool and warm water species. Hence, the distribution of cool and warm water conodont species may have overlapped in pelagic Panthalassa during the late Kungurian.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"105 - 119"},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44285367","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. Plotopterids, commonly known as “penguin-like birds”, are wing-propelled diving birds known from the latest Eocene to middle Miocene in the eastern and western Pacific Rim. Here, we describe two new specimens of the family Plotopteridae, a right femur from the Itanoura Formation (latest Eocene to earliest Oligocene), and a distal half of a right tibiotarsus from the Kakinoura Formation (early Oligocene), both at the lower part of the Nishisonogi Group, Saikai City, Nagasaki Prefecture, Kyushu, southwestern Japan. The femur is slightly younger than or potentially as old as the earliest plotopterid known from Japan and the U.S.A. CT scanning revealed that it has a dense cortical bone, justifying its taxonomic assignment to the family Plotopteridae. It resembles the femur of Olympidytes, which was previously considered endemic to North America, in its femoral neck, well developed trochanter femoris, and straight facies articularis antitrochanterica, but is not assignable to any known genus. The tibiotarsus resembles that of Olympidytes in the presence of a well-developed trochlea catilaginis tibialis, a large embossment lateral to the pons supratendineus, and a deep incisura intercondylaris, and therefore referable to Olympidytes. The possibility of hindlimb-propelled diving in the family Plotopteidae was also discussed. These new specimens suggest the early diversity of the family in Japan was higher than previously thought.
{"title":"Early Plotopteridae Specimens (Aves) from the Itanoura and Kakinoura Formations (Latest Eocene to Early Oligocene), Saikai, Nagasaki Prefecture, Western Japan","authors":"H. Mori, K. Miyata","doi":"10.2517/2020PR018","DOIUrl":"https://doi.org/10.2517/2020PR018","url":null,"abstract":"Abstract. Plotopterids, commonly known as “penguin-like birds”, are wing-propelled diving birds known from the latest Eocene to middle Miocene in the eastern and western Pacific Rim. Here, we describe two new specimens of the family Plotopteridae, a right femur from the Itanoura Formation (latest Eocene to earliest Oligocene), and a distal half of a right tibiotarsus from the Kakinoura Formation (early Oligocene), both at the lower part of the Nishisonogi Group, Saikai City, Nagasaki Prefecture, Kyushu, southwestern Japan. The femur is slightly younger than or potentially as old as the earliest plotopterid known from Japan and the U.S.A. CT scanning revealed that it has a dense cortical bone, justifying its taxonomic assignment to the family Plotopteridae. It resembles the femur of Olympidytes, which was previously considered endemic to North America, in its femoral neck, well developed trochanter femoris, and straight facies articularis antitrochanterica, but is not assignable to any known genus. The tibiotarsus resembles that of Olympidytes in the presence of a well-developed trochlea catilaginis tibialis, a large embossment lateral to the pons supratendineus, and a deep incisura intercondylaris, and therefore referable to Olympidytes. The possibility of hindlimb-propelled diving in the family Plotopteidae was also discussed. These new specimens suggest the early diversity of the family in Japan was higher than previously thought.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"145 - 159"},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48192797","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}
A. Safari, Hossein Ghanbarloo, Saber Mahmudi Purnajjari, H. V. Moghaddam
Abstract. The Qom Formation deposits, located at 12 km southeast of Salafchegan (N: 34° 21′ 26″ and E: 50° 32′ 14″), have a thickness of 110 m. The formation includes thin, and medium-to-thick bedded limestone, as well as shale, overlying the Lower Red Formation (early Oligocene) above an erosional unconformity. Its upper boundary is covered by alluvium sediments. Biostratigraphic distributions of benthic Foraminifera were used to determine the age and paleoenvironmental conditions of the Qom Formation. Two assemblage zones were recognized. Assemblage zones 1 and 2 were indicative of a Rupelian–Chattian age. The inner shelf (restricted and semi-restricted lagoons) and middle shelf (open marine) settings were formed on an open shelf platform. Euphotic conditions were dominant during the early and late Rupelian in the studied area. During the middle Rupelian, photic conditions were variable between euphotic and mesophotic to oligophotic. During the early and middle Chattian, photic conditions varied between oligophotic, mesophotic to oligophotic, and euphotic. During the late Chattian, mesophotic-oligophotic conditions were dominant. Additionally, a high level of salinity (40–50 and > 50 psu) was present in the studied area during the early Rupelian. The level of salinity varied from normal (30–40 psu) to hypersaline (40–50 psu) during the late Rupelian. Salinity during early and late Chattian subages was normal (30–40 psu). However, hypersaline (40–50 and > 50 psu) and normal (30–40 psu) conditions were present in the middle Chattian. Eutrophic to mesotrophic-oligotrophic conditions were found in the early Rupelian age. However, mesotrophy-oligotrophy dominated during the middle and late Rupelian and Chattian ages. In addition, the paleo-water depth of the Qom Sea fluctuated from < 10 m to > 20 m. Foralgal and foramol associations are dominant in the studied area during the Rupelian-Chattian ages. The general depositional environment of the Qom Formation is associated with seagrass meadows.
{"title":"Biostratigraphy and Paleoenvironments of the Oligocene Deposits (Qom Formation) in the Neyzar Area (Southeast of Salafchegan), Iran","authors":"A. Safari, Hossein Ghanbarloo, Saber Mahmudi Purnajjari, H. V. Moghaddam","doi":"10.2517/2020PR014","DOIUrl":"https://doi.org/10.2517/2020PR014","url":null,"abstract":"Abstract. The Qom Formation deposits, located at 12 km southeast of Salafchegan (N: 34° 21′ 26″ and E: 50° 32′ 14″), have a thickness of 110 m. The formation includes thin, and medium-to-thick bedded limestone, as well as shale, overlying the Lower Red Formation (early Oligocene) above an erosional unconformity. Its upper boundary is covered by alluvium sediments. Biostratigraphic distributions of benthic Foraminifera were used to determine the age and paleoenvironmental conditions of the Qom Formation. Two assemblage zones were recognized. Assemblage zones 1 and 2 were indicative of a Rupelian–Chattian age. The inner shelf (restricted and semi-restricted lagoons) and middle shelf (open marine) settings were formed on an open shelf platform. Euphotic conditions were dominant during the early and late Rupelian in the studied area. During the middle Rupelian, photic conditions were variable between euphotic and mesophotic to oligophotic. During the early and middle Chattian, photic conditions varied between oligophotic, mesophotic to oligophotic, and euphotic. During the late Chattian, mesophotic-oligophotic conditions were dominant. Additionally, a high level of salinity (40–50 and > 50 psu) was present in the studied area during the early Rupelian. The level of salinity varied from normal (30–40 psu) to hypersaline (40–50 psu) during the late Rupelian. Salinity during early and late Chattian subages was normal (30–40 psu). However, hypersaline (40–50 and > 50 psu) and normal (30–40 psu) conditions were present in the middle Chattian. Eutrophic to mesotrophic-oligotrophic conditions were found in the early Rupelian age. However, mesotrophy-oligotrophy dominated during the middle and late Rupelian and Chattian ages. In addition, the paleo-water depth of the Qom Sea fluctuated from < 10 m to > 20 m. Foralgal and foramol associations are dominant in the studied area during the Rupelian-Chattian ages. The general depositional environment of the Qom Formation is associated with seagrass meadows.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"25 1","pages":"63 - 78"},"PeriodicalIF":0.9,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46073465","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}
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