Lower Triassic conodont biostratigraphy has been well studied around the world in the past decades, but the Induan-Olenekian boundary （IOB） remains undecided. The Novispathodus waageni group has been taxonomically r...Lower Triassic conodont biostratigraphy has been well studied around the world in the past decades, but the Induan-Olenekian boundary （IOB） remains undecided. The Novispathodus waageni group has been taxonomically re-assessed based on abundant new materials from the Jianshi and Chaohu sections, South China. New study shows that Nv. waageni typically possesses： （1） an approximately equi-dimentional P1 blade element, （2） an accurate upper profile with denticle height descending in both directions, （3） a denticulated posterior edge （lower denticles posterior of the highest denticle）, and （4） a round basal cavity outline. Of the three proposed subspecies of the waageni species, both Nv. waageni waageni （Sweet, 1970） and Nv. w. eowaageni （Zhao and Orchard, 2005） are valid, and the former differs clearly from Nv. w. eowaageni in having （1） a slightly higher length/height ratio （holotype=1.30 ： 1.23）, （2） a thicker blade, sometimes with medial thickening, （3） fewer （broader） denticles per unit length, （4） generally recurved denticles, not straight and upright, （5） highest denticles closer to posterior, （6） common differentiation of a posterior cusp, and （7） more sinuous basal profile, with increased posterior upturning. A third subspecies illustrated as Nv. waageni n. subsp. A sensu Goudemand, 2014 is not conspecific with older individuals of Nv. w. eowaageni, and also cannot be as- signed to the Nv. waageni group. Abundant new materials demonstrate a clear ontogenic process for Nv. w. eowaageni, indicating that Nv. w. eowaageni occurring in the Induan-Olenekian boundary （IOB） succession is rather stable. Small, earlier individuals （i.e., those from Bed 225 in Jianshi） are referred to as Nv. w. eowaageni Morphotype A, and are thought to have likely evolved from Ns. dieneri Morphotype 3, and to be the precursor of mature elements ofNv. w. eowaageni. The first appearance datum of Nv. w. eowaageni therefore is an ideal mark defining the IOB.展开更多
Professor Zunyi Yang is a pioneer paleontologist who established the earliest Paleontological education and research in China, and has contributed his lifetime to promotion of Chinese paleontological education and res...Professor Zunyi Yang is a pioneer paleontologist who established the earliest Paleontological education and research in China, and has contributed his lifetime to promotion of Chinese paleontological education and researches as well as the studies on the Permian-Triassic （P-Tr） mass extinction and its possible causes. Yang has studied six fossil clades and trace fossils, together with his colleagues, he has established 6 new species of cephalopods, 1 new genus and 15 new species of gastropods, 8 new genera and 31 new species of bivalves, 17 new genera and 66 new species of brachiopods, 1 new genus and 4 new species of ophiuroids, 2 new genera and 7 new species of triopsids （Crustacea）, and 3 new ichnogenera and 7 new ichnospeeies of trace fossils. Yang led the 2nd IGCP working on the P-Tr mass extinction in the world. His group＇s excellent works on basic stratigraphy and paleontology enable the GSSP of P-~r boundary （PTB） to be ratified in China. Yang＇s earlier works on three-episode extinction pattern and volcanism-causing extinction hypothesis are also highlighted here to show how their first-hand data and initiative hypothesis have influenced the current and ongoing debates on the P-Tr crisis and possible causation. Yang school＇s extinction pattern is reviewed here, and their 2nd phase of extinction is marked by a dramatic loss in biodiversity, pointing to a widely accepted mass extinction. The 3rd extinction is characterized by ecological collapse of ecosystem structures and disappearance of the PTB microbialite ecosystem, while the 1st extinction （also prelude extinction） is indicated by the collapses of deep-water and reef ecosystems. Updated studies show that the volcanic ashes near the PTB originated from silicic, subduction-related igneous activity with little or no basaltic input. This subduction zone activity is related to closure of the Paleo-Tethys Ocean, and the intensity and frequency of the volcanic activity appear to increase near the P-Tr extinction interval. Hg anomalies （Hg/TOC ratios and Hg isotopes） were also detected from the P-Tr extinction interval, and they are interpreted as the results of enhanced volcanic-generated atmospheric mercury, which was injected by the violate eruption of the Siberian traps. Thus, the peak felsic volcanism is coeval with violate eruption of Siberian traps, and the coupled relationship between both types of volcanisms and biotic extinction suggests a causal relationship.展开更多
基金supported by four NSFC grants (Nos.41473006, 41572091, 41673011, 41772007)one grant from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan)
文摘Lower Triassic conodont biostratigraphy has been well studied around the world in the past decades, but the Induan-Olenekian boundary （IOB） remains undecided. The Novispathodus waageni group has been taxonomically re-assessed based on abundant new materials from the Jianshi and Chaohu sections, South China. New study shows that Nv. waageni typically possesses： （1） an approximately equi-dimentional P1 blade element, （2） an accurate upper profile with denticle height descending in both directions, （3） a denticulated posterior edge （lower denticles posterior of the highest denticle）, and （4） a round basal cavity outline. Of the three proposed subspecies of the waageni species, both Nv. waageni waageni （Sweet, 1970） and Nv. w. eowaageni （Zhao and Orchard, 2005） are valid, and the former differs clearly from Nv. w. eowaageni in having （1） a slightly higher length/height ratio （holotype=1.30 ： 1.23）, （2） a thicker blade, sometimes with medial thickening, （3） fewer （broader） denticles per unit length, （4） generally recurved denticles, not straight and upright, （5） highest denticles closer to posterior, （6） common differentiation of a posterior cusp, and （7） more sinuous basal profile, with increased posterior upturning. A third subspecies illustrated as Nv. waageni n. subsp. A sensu Goudemand, 2014 is not conspecific with older individuals of Nv. w. eowaageni, and also cannot be as- signed to the Nv. waageni group. Abundant new materials demonstrate a clear ontogenic process for Nv. w. eowaageni, indicating that Nv. w. eowaageni occurring in the Induan-Olenekian boundary （IOB） succession is rather stable. Small, earlier individuals （i.e., those from Bed 225 in Jianshi） are referred to as Nv. w. eowaageni Morphotype A, and are thought to have likely evolved from Ns. dieneri Morphotype 3, and to be the precursor of mature elements ofNv. w. eowaageni. The first appearance datum of Nv. w. eowaageni therefore is an ideal mark defining the IOB.
基金partly supported by three NSFC research grants (Nos. 41661134047, 41772007, 41730320)one Hubei Provincial Natural Science Foundation grant (No. 2017CFA019)
文摘Professor Zunyi Yang is a pioneer paleontologist who established the earliest Paleontological education and research in China, and has contributed his lifetime to promotion of Chinese paleontological education and researches as well as the studies on the Permian-Triassic （P-Tr） mass extinction and its possible causes. Yang has studied six fossil clades and trace fossils, together with his colleagues, he has established 6 new species of cephalopods, 1 new genus and 15 new species of gastropods, 8 new genera and 31 new species of bivalves, 17 new genera and 66 new species of brachiopods, 1 new genus and 4 new species of ophiuroids, 2 new genera and 7 new species of triopsids （Crustacea）, and 3 new ichnogenera and 7 new ichnospeeies of trace fossils. Yang led the 2nd IGCP working on the P-Tr mass extinction in the world. His group＇s excellent works on basic stratigraphy and paleontology enable the GSSP of P-~r boundary （PTB） to be ratified in China. Yang＇s earlier works on three-episode extinction pattern and volcanism-causing extinction hypothesis are also highlighted here to show how their first-hand data and initiative hypothesis have influenced the current and ongoing debates on the P-Tr crisis and possible causation. Yang school＇s extinction pattern is reviewed here, and their 2nd phase of extinction is marked by a dramatic loss in biodiversity, pointing to a widely accepted mass extinction. The 3rd extinction is characterized by ecological collapse of ecosystem structures and disappearance of the PTB microbialite ecosystem, while the 1st extinction （also prelude extinction） is indicated by the collapses of deep-water and reef ecosystems. Updated studies show that the volcanic ashes near the PTB originated from silicic, subduction-related igneous activity with little or no basaltic input. This subduction zone activity is related to closure of the Paleo-Tethys Ocean, and the intensity and frequency of the volcanic activity appear to increase near the P-Tr extinction interval. Hg anomalies （Hg/TOC ratios and Hg isotopes） were also detected from the P-Tr extinction interval, and they are interpreted as the results of enhanced volcanic-generated atmospheric mercury, which was injected by the violate eruption of the Siberian traps. Thus, the peak felsic volcanism is coeval with violate eruption of Siberian traps, and the coupled relationship between both types of volcanisms and biotic extinction suggests a causal relationship.
