Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans ...Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst mollusks are the least sensitive. Mortalities occur where O_2 concentrations are below 2.0 mg/L, equivalent to saturation with oxygen content about 25% PAL（present atmospheric level）. Therefore, the minimal oxygen requirement for maintaining animal diversity since Cambrian is determined as 25% PAL. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. Geological and geochemical studies suggest a constant increase of the oxygen level and a contraction of anoxic oceans during Ediacaran-Cambrian transition when the world oceans experienced a rapid diversification of metazoan lineages. However, fossil first appearances of animal phyla are obviously asynchronous and episodic, showing a sequence as： basal metazoans〉lophotrochozoans〉ecdysozoans and deuterostomes. According to hitherto known data of fossil record and hypoxic sensitivity of animals, the appearance sequence of different animals is broadly consistent with their hypoxic sensitivity： animals like molluscs and annelids that are less sensitive to hypoxia appeared earlier, while animals like echinoderms and fishes that are more sensitive to hypoxia came later. Therefore, it is very likely that the appearance order of animals is corresponding to the increasing oxygen level and/or the contraction of anoxic oceans during Ediacaran-Cambrian transition.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
Sulfate reduction is an essential metabolism that maintains biogeochemical cycles in marine and terrestrial ecosystems.Sulfate reducers are exclusively prokaryotic,phylogenetically diverse,and may have evolved early i...Sulfate reduction is an essential metabolism that maintains biogeochemical cycles in marine and terrestrial ecosystems.Sulfate reducers are exclusively prokaryotic,phylogenetically diverse,and may have evolved early in Earth’s history.However,their origin is elusive and unequivocal fossils are lacking.Here we report a new microfossil,Qingjiangonema cambria,from518-million-year-old black shales that yield the Qingjiang biota.Qingjiangonema is a long filamentous form comprising hundreds of cells filled by equimorphic and equidimensional pyrite microcrystals with a light sulfur isotope composition.Multiple lines of evidence indicate Qingjiangonema was a sulfate-reducing bacterium that exhibits similar patterns of cell organization to filamentous forms within the phylum Desulfobacterota,including the sulfate-reducing Desulfonema and sulfide-oxidizing cable bacteria.Phylogenomic analyses confirm separate,independent origins of multicellularity in Desulfonema and in cable bacteria.Molecular clock analyses infer that the Desulfobacterota,which encompass a majority of sulfate-reducing taxa,diverged~2.41 billion years ago during the Paleoproterozoic Great Oxygenation Event,while cable bacteria diverged~0.56 billion years ago during or immediately after the Neoproterozoic Oxygenation Event.Taken together,we interpret Qingjiangonema as a multicellular sulfate-reducing microfossil and propose that cable bacteria evolved from a multicellular filamentous sulfate-reducing ancestor.We infer that the diversification of the Desulfobacterota and the origin of cable bacteria may have been responses to oxygenation events in Earth’s history.展开更多
基金supported by National Basic Research Program of China (No. 2013CB835002)National Natural Science Foundation of China (No. 41272036)
文摘Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst mollusks are the least sensitive. Mortalities occur where O_2 concentrations are below 2.0 mg/L, equivalent to saturation with oxygen content about 25% PAL（present atmospheric level）. Therefore, the minimal oxygen requirement for maintaining animal diversity since Cambrian is determined as 25% PAL. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. Geological and geochemical studies suggest a constant increase of the oxygen level and a contraction of anoxic oceans during Ediacaran-Cambrian transition when the world oceans experienced a rapid diversification of metazoan lineages. However, fossil first appearances of animal phyla are obviously asynchronous and episodic, showing a sequence as： basal metazoans〉lophotrochozoans〉ecdysozoans and deuterostomes. According to hitherto known data of fossil record and hypoxic sensitivity of animals, the appearance sequence of different animals is broadly consistent with their hypoxic sensitivity： animals like molluscs and annelids that are less sensitive to hypoxia appeared earlier, while animals like echinoderms and fishes that are more sensitive to hypoxia came later. Therefore, it is very likely that the appearance order of animals is corresponding to the increasing oxygen level and/or the contraction of anoxic oceans during Ediacaran-Cambrian transition.
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.
基金supported by the National Natural Science Foundation of China(41890843,41890845,41930319,42242201,and 42272354)the Overseas Expertise Introduction Project for Discipline Innovation(the 111 Project,D17013)+1 种基金the Natural Science Basic Research Program of Shaanxi(2022JC-DW5-01)the National Science Foundation of USA(EAR-1554897).
文摘Sulfate reduction is an essential metabolism that maintains biogeochemical cycles in marine and terrestrial ecosystems.Sulfate reducers are exclusively prokaryotic,phylogenetically diverse,and may have evolved early in Earth’s history.However,their origin is elusive and unequivocal fossils are lacking.Here we report a new microfossil,Qingjiangonema cambria,from518-million-year-old black shales that yield the Qingjiang biota.Qingjiangonema is a long filamentous form comprising hundreds of cells filled by equimorphic and equidimensional pyrite microcrystals with a light sulfur isotope composition.Multiple lines of evidence indicate Qingjiangonema was a sulfate-reducing bacterium that exhibits similar patterns of cell organization to filamentous forms within the phylum Desulfobacterota,including the sulfate-reducing Desulfonema and sulfide-oxidizing cable bacteria.Phylogenomic analyses confirm separate,independent origins of multicellularity in Desulfonema and in cable bacteria.Molecular clock analyses infer that the Desulfobacterota,which encompass a majority of sulfate-reducing taxa,diverged~2.41 billion years ago during the Paleoproterozoic Great Oxygenation Event,while cable bacteria diverged~0.56 billion years ago during or immediately after the Neoproterozoic Oxygenation Event.Taken together,we interpret Qingjiangonema as a multicellular sulfate-reducing microfossil and propose that cable bacteria evolved from a multicellular filamentous sulfate-reducing ancestor.We infer that the diversification of the Desulfobacterota and the origin of cable bacteria may have been responses to oxygenation events in Earth’s history.
