Ancestral lobopodians,which diversified and flourished in the Cambrian seas,have long drawn much attention in that not only their living counterparts,onychophorans and tardigrades,but euarthropods(Chelicerata,Myriapod...Ancestral lobopodians,which diversified and flourished in the Cambrian seas,have long drawn much attention in that not only their living counterparts,onychophorans and tardigrades,but euarthropods(Chelicerata,Myriapoda,Crustacea,and Hexapoda) may have been deeply rooted in stem-group lobopodians.Antennacanthopodia gracilis new genus and species is described展开更多
Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inh...Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.展开更多
对湖北松滋黑档口早始新世洋溪组进一步采集和研究表明,该组下部黑色泥页岩乃是世界上罕见的早始新世猴鸟鱼化石库。不仅产有世界上最古老(距今5 500万年)的灵长类代表——阿喀琉斯基猴(Archicebus achilles Ni et al.,2013)、我国南方...对湖北松滋黑档口早始新世洋溪组进一步采集和研究表明,该组下部黑色泥页岩乃是世界上罕见的早始新世猴鸟鱼化石库。不仅产有世界上最古老(距今5 500万年)的灵长类代表——阿喀琉斯基猴(Archicebus achilles Ni et al.,2013)、我国南方已知鹤形目化石最早记录——黑档口松滋鸟(Songzia heidangkouensis Hou,1990)、尖爪松滋鸟(Songzia acutunguis Wang et al.,2012)以及高丰度且保存完美的湖北江汉鱼Jianghanichthys hubeisis(Lei,1987)化石群,而且又新发现鬣蜥类(Agamid)、蝉(cicada)、蜘蛛(spider)、白蚁(termite)、古植物以及江汉鱼以外的多种鱼类化石。这是继北美绿江组(Green River Formation)、德国梅瑟尔(Messel)化石库(Fossillagersttte)之后,世界上新近发现的第三个早始新世特异埋藏群,在产出时代上较前两者早700万年。生物地层、构造古地理、沉积相和生态与埋藏学的分析研究表明,该特异埋藏群形成于早始新世初期江汉盆地西缘松滋-当阳盆缘凹陷之中。温湿的气候、充足的陆缘供给为盆缘凹陷及相邻低山-湿地中生物群的繁衍创造了条件;继之鄂西山地抬升和江汉盆地向东收敛而诱发的湖平面上升、咸化、滞流和缺氧以及(或者)盆地中部继之喷溢的基性火山熔岩而散发的有害气体和火山粉尘,可能是导致该生物群集群死亡的主要原因;伴随湖底缺氧而出现大量厌氧细菌席和藻类,在吸食生物软体的同时,为沉入湖底生物群骨架的完好保存创造了必要的封闭条件。展开更多
文摘Ancestral lobopodians,which diversified and flourished in the Cambrian seas,have long drawn much attention in that not only their living counterparts,onychophorans and tardigrades,but euarthropods(Chelicerata,Myriapoda,Crustacea,and Hexapoda) may have been deeply rooted in stem-group lobopodians.Antennacanthopodia gracilis new genus and species is described
基金supported by the Natural Science Foundation of China(Nos.41930319,41621003,and EAR-1554897)the 111 Project(No.D17013)the Natural Science Basic Research Plan of Shaanxi Province(No.2022JC-DW5-01).
文摘Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.
文摘对湖北松滋黑档口早始新世洋溪组进一步采集和研究表明,该组下部黑色泥页岩乃是世界上罕见的早始新世猴鸟鱼化石库。不仅产有世界上最古老(距今5 500万年)的灵长类代表——阿喀琉斯基猴(Archicebus achilles Ni et al.,2013)、我国南方已知鹤形目化石最早记录——黑档口松滋鸟(Songzia heidangkouensis Hou,1990)、尖爪松滋鸟(Songzia acutunguis Wang et al.,2012)以及高丰度且保存完美的湖北江汉鱼Jianghanichthys hubeisis(Lei,1987)化石群,而且又新发现鬣蜥类(Agamid)、蝉(cicada)、蜘蛛(spider)、白蚁(termite)、古植物以及江汉鱼以外的多种鱼类化石。这是继北美绿江组(Green River Formation)、德国梅瑟尔(Messel)化石库(Fossillagersttte)之后,世界上新近发现的第三个早始新世特异埋藏群,在产出时代上较前两者早700万年。生物地层、构造古地理、沉积相和生态与埋藏学的分析研究表明,该特异埋藏群形成于早始新世初期江汉盆地西缘松滋-当阳盆缘凹陷之中。温湿的气候、充足的陆缘供给为盆缘凹陷及相邻低山-湿地中生物群的繁衍创造了条件;继之鄂西山地抬升和江汉盆地向东收敛而诱发的湖平面上升、咸化、滞流和缺氧以及(或者)盆地中部继之喷溢的基性火山熔岩而散发的有害气体和火山粉尘,可能是导致该生物群集群死亡的主要原因;伴随湖底缺氧而出现大量厌氧细菌席和藻类,在吸食生物软体的同时,为沉入湖底生物群骨架的完好保存创造了必要的封闭条件。
