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Two-Tiered Transition of the North Atlantic Surface Hydrology during the Past 1.6 Ma: Multiproxy Evidence from Planktic Foraminifera 过去1.6Ma北大西洋表层水文的两层转换:浮游生物有孔虫的多重证据
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2020PR026
M. Yamasaki, C. Shimada, M. Ikehara, R. Schiebel
Abstract. Analyses of planktic foraminiferal assemblage data, test morphology, and stable oxygen isotopes from the Integrated Ocean Drilling Program (IODP) Site U1304 in the North Atlantic reveal a stepwise regional migration of the oceanic fronts around 0.6 Ma and 0.4 Ma, i.e., during Marine Isotope Stages (MISs) 15 and 11, respectively. Both changes of planktic foraminiferal assemblages and shell carbonate isotopes indicate that the cold Arctic waters in general persisted at IODP Site U1304 from 1.6 to 0.6 Ma (MIS 15), even though the warmer waters originating from the Atlantic waters episodically bathed Site U1304 during the interglacial periods. During the time-interval from ca. 0.6 to 0.4 Ma (MISs 15–11), an alternating dominance of Artic and Atlantic waters at the Site U1304 has been suggested from isotopic evidence. In MIS 11, the dominant planktic foraminiferal species Neogloboquadrina pachyderma experienced a short-term but significant decrease in test size. The test-size change may have been caused by accelerated reproduction in more favorite feeding conditions over the long-lasting interglacial period around the Subarctic Front. This finding is supported by the presence of massive diatoms oozes in the same time-interval. The modern-type glacial/interglacial change of the surface water system established since ca. 0.4 Ma (MIS 11) followed the Mid-Brunhes Event.
摘要对北大西洋综合海洋钻探计划(IODP)U1304站点的浮游有孔虫组合数据、测试形态和稳定氧同位素的分析表明,在0.6 Ma和0.4 Ma左右,即分别在海洋同位素阶段(MISs)15和11期间,洋锋发生了逐步的区域迁移。浮游有孔虫组合和壳碳酸盐同位素的变化都表明,尽管在间冰期,来自大西洋水域的温暖水域偶尔会沐浴在U1304地点,但IODP U1304地点的寒冷北极水域总体上持续了1.6至0.6 Ma(MIS 15)。在约0.6至0.4 Ma的时间间隔内(MISs 15-11),同位素证据表明U1304地点的北极和大西洋水域交替占主导地位。在MIS 11中,优势浮游有孔虫物种厚皮新球虫的试验尺寸出现了短期但显著的下降。试验大小的变化可能是由亚北极锋周围长期间冰期在更喜欢的觅食条件下加速繁殖引起的。这一发现得到了在同一时间间隔内存在大量硅藻泥的支持。地表水系统的现代型冰川/间冰川变化始于约0.4 Ma(MIS 11),发生在中布鲁内斯事件之后。
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引用次数: 0
The Structure of the Miocene Northwestern Pacific Ichthyofauna as Revealed By Two Fossil Fish Assemblages From Sakhalin Island, Russia 俄罗斯库页岛两个鱼类化石组合揭示的中新世西北太平洋鱼类的结构
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR005
M. Nazarkin
Abstract. Two coeval assemblages of fossil fishes came from the middle–late Miocene deposits of Sakhalin Island, Russia. The fish community from the Agnevo Formation consists of 28 species belonging to 15 families of shallow-water fishes, with the predominance of cottoids, stichaeoids, and pleuronectoids. The assemblage from the Kurasi Formation contains fossils of 35 species from 27 fish families and comprises mainly mesopelagic dwellers, such as myctophids, argentiniforms, stomiiforms, and aulopiforms. These assemblages differ mainly in the number of species belonging to extinct genera. Among the 28 fish genera known from the Agnevo Formation, 14 (50%) genera are extinct. In contrast, out of 35 genera described from the Kurasi Formation only three (about 8.6%) genera are extinct. The morphological distances between the fossil and recent congeneric species are more pronounced and defined in the shallow-water community than in the deep-water assemblage. The differences in taxonomic composition between the fossil assemblages likely reflect the different influence of the climatic and geographic events in the Neogene and Quarternary on the evolutionary rates of shallow- and deep-water fish communities.
摘要来自俄罗斯库页岛中新世中晚期沉积物的两组同一时期的鱼类化石。Agnevo组鱼类群落由浅水鱼类15科28种组成,以尾形、尾形和胸膜形鱼类为主。库拉西组的组合包含27个鱼类科的35种化石,主要包括中远洋居民,如嗜菌鱼、阿根廷鱼、口形鱼和拟形鱼。这些组合的区别主要在于属于灭绝属的物种数量。在Agnevo组已知的28种鱼类中,有14种(50%)已经灭绝。相比之下,在Kurasi组描述的35个属中,只有3个(约8.6%)属已经灭绝。在浅水群落中,化石与最近的同类物种之间的形态距离比在深水群落中更为明显和明确。化石组合在分类组成上的差异可能反映了新近纪和第四纪气候和地理事件对浅水和深水鱼类群落进化速率的不同影响。
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引用次数: 0
An Additional New Species of Turbo (Marmarostoma) (Gastropoda: Turbinidae) from the Middle Miocene of the Izu Peninsula, Central Japan 日本中部伊豆半岛中新世中期Turbo (Marmarostoma)(腹足目:Turbo科)一新种
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR006
S. Tomida, Hayato Sano, T. Kase
Abstract. The turbinid gastropod Turbo (Marmarostoma) is common in the limestone bodies within the middle Miocene Sakurada and Kadono formations (Yugashima Group) on the Izu Peninsula, central Japan. The limestone bodies were originally deposited under a low-latitude, tropical climate in the northeastern Philippine Sea and then drifted northwards on the Philippine Sea Plate. This paper describes an additional species, Turbo (Marmarostoma) ishidai sp. nov., from the Ena Limestone on the south-western Izu Peninsula. This new species is characterized by its large shell size and shell form similar to the modern Australian endemic species Turbo (Marmarostoma) cepoides Smith, 1880, but differs in having thick tuberculate spiral cords on the shell surface of earlier teleoconch whorls instead of the smooth and broad spiral cords on and around the angled shoulder. The addition of this new species further highlights the presence of a biodiversity hotspot of this gastropod group in the northeastern Philippines Sea during the middle Miocene.
摘要在日本中部伊豆半岛中中新世樱田组和香野组(汤岛群)的石灰岩中,常见的是涡状腹足动物Turbo (Marmarostoma)。石灰岩体最初沉积于菲律宾海东北部低纬度的热带气候下,然后在菲律宾海板块上向北漂移。本文报道了伊豆半岛西南部埃纳石灰岩的另一种——Turbo (Marmarostoma) ishidai sp. nov.。这个新种的特点是其大的壳尺寸和壳形式类似于现代澳大利亚特有物种Turbo (Marmarostoma) cepoides Smith, 1880,但不同的是,在早期的远螺螺螺的壳表面有厚的结核状螺旋索,而不是在有角的肩膀上和周围有光滑而宽阔的螺旋索。这一新物种的加入进一步突出了中新世中期菲律宾海东北部腹足类生物多样性热点的存在。
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引用次数: 1
Nonmarine Mass Extinctions 非海洋物种大灭绝
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR004
S. Lucas
Abstract. A critical review of putative nonmarine mass extinctions associated with the so-called “Big 5 mass extinctions” of marine invertebrates (Late Ordovician, Late Devonian, end Permian, end Triassic and end Cretaceous) as well as a likely sixth mass extinction in the marine realm, the end-Guadalupian extinction, reveals little evidence of coeval marine and nonmarine mass extinctions. Little lived on land during the Ordovician other than a bryophyte-like flora that appears to have been diversifying, not going extinct, during the Late Ordovician. No case can be made for mass extinctions on land coeval with the marine extinctions of the Late Devonian-land plant diversity increased into the Carboniferous, and the tetrapod fossil record is inadequate to identify any mass extinctions. A case can be made for coeval plant/tetrapod extinctions and the end-Guadalupian marine extinctions, so this may be the first coeval marine-nonmarine mass extinction. However, problems of timing and questions about the extent of the nonmarine late/end-Guadalupian extinctions indicate that further research is needed. There were no mass extinctions of land plants, insects or tetrapods across the Permo–Triassic boundary. The Late Triassic was a time of low origination and high extinction rates on land and in the seas; there was no single end-Triassic mass extinction in either realm. The end-Cretaceous provides the strongest case for coeval land–sea mass extinctions, but there is no mass extinction of land plants, evidence of insect extinction is based on assumption-laden analyses of proxies for insect diversity and the tetrapod extinction was very selective. So, whether the nonmarine extinction at the end of the Cretaceous was a mass extinction is worth questioning. Part of the inability to identify nonmarine mass extinctions stems from taphonomic megabiases due to the relatively poor quality and uneven sampling of the nonmarine fossil record. Extinction resistance and resilience of terrestrial organisms is also a likely factor in the dearth of nonmarine mass extinctions, and this merits further investigation.
摘要对与所谓的海洋无脊椎动物“五大灭绝”(晚奥陶纪、晚泥盆纪、二叠纪末、三叠纪末和白垩纪末)以及海洋领域可能发生的第六次大规模灭绝——瓜达卢皮群岛末灭绝——相关的假定非海洋大灭绝进行了批判性审查,发现几乎没有证据表明同时代的海洋和非海洋大物种灭绝。在奥陶纪,除了苔藓植物外,几乎没有人生活在陆地上。在奥陶世晚期,苔藓植物似乎已经多样化,而不是灭绝。没有证据表明陆地上的大规模灭绝与晚泥盆纪陆地植物多样性增加到石炭纪的海洋灭绝同时发生,四足动物化石记录不足以确定任何大规模灭绝。可以为同时代的植物/四足动物灭绝和瓜达卢皮海洋灭绝提供证据,因此这可能是第一次同时代的海洋非海洋大灭绝。然而,时间问题和非海洋晚期/末期瓜达卢皮动物灭绝的程度问题表明,还需要进一步的研究。二叠纪-三叠纪边界没有发生陆地植物、昆虫或四足动物的大规模灭绝。三叠纪晚期是陆地和海洋起源率低、灭绝率高的时期;这两个领域都没有三叠纪末的大灭绝。白垩纪末期为同时代的陆地-海洋大灭绝提供了最有力的证据,但陆地植物没有大灭绝,昆虫灭绝的证据是基于对昆虫多样性指标的假设分析,四足动物的灭绝是非常有选择性的。因此,白垩纪末的非海洋灭绝是否是一次大灭绝值得质疑。无法识别非海洋大灭绝的部分原因是由于非海洋化石记录的质量相对较差和采样不均衡而导致的地震学大偏差。陆生生物对灭绝的抵抗力和复原力也是非海洋大规模灭绝减少的一个可能因素,这值得进一步研究。
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引用次数: 12
Systematic Revision and Palaeobiology of Emplastron edwardsi (Van Straelen, 1928) gen. et comb. nov. (Crustacea, Decapoda, Astacidae) Entombed within Travertine, from Sézanne, France 爱德华Emplastron edwardsi (Van Straelen, 1928)的系统修正与古生物学。11 .(甲壳纲,十足纲,虾虾科)埋在石灰华内,产自法国ssamzanne
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR007
R. O'Flynn, Denis Audo, T. Kawai
Abstract. Crayfish are rare in the fossil record and therefore it is important to investigate each occurrence in detail. The only known fossil crayfish from France, Astacus edwardsi Van Straelen, 1928, is known from a replica made by pouring plaster of Paris inside the holotype (subsequently destroyed), an external mould extracted from a travertine cavity from the Thanetian of Sézanne. An evaluation of the taxonomic name, A. edwardsi, is provided; A. edwardsi is considered valid in accordance with ICZN rulings. It possesses atypical features for all other astacid genera, thus Emplastron gen. nov. is erected. Emplastron edwardsi gen. et comb. nov. inhabited a warm climate with calm waters, abundant food sources, and an ample supply of calcium carbonate: so much so that it is surprising that it is the only recovered specimen. Despite apparent North American faunal and floral affinities in the vicinity, E. edwardsi is more closely related to European crayfishes than it is to American ones.
摘要小龙虾在化石记录中很罕见,因此详细调查每一次发生的情况很重要。唯一已知的来自法国的小龙虾化石,Astacus edwardsi Van Straelen,1928年,是从一个复制品中发现的,该复制品是在正模中倒入巴黎石膏制成的(随后被销毁),正模是从塞尚Thanetian的钙华洞穴中提取的外部模具。提供了对分类名称A.edwardsi的评估;A.根据ICZN的裁决,爱德华被视为有效。它具有其他所有无酸属的非典型特征,因此建立了Emplastron gen.nov。雇佣爱德华一代和科姆。nov.生活在温暖的气候中,有平静的水域、丰富的食物来源和充足的碳酸钙供应:如此之多,以至于它是唯一被发现的标本,这令人惊讶。尽管附近有明显的北美区系和花的亲缘关系,爱德华氏小龙虾与欧洲小龙虾的亲缘关系比与美国小龙虾的更为密切。
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引用次数: 2
The Great Ordovician Biodiversification Event (GOBE) is Not a Single Event 奥陶纪生物多样性大事件(GOBE)不是一个单一的事件
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR001
T. Servais, B. Cascales‐Miñana, D. Harper
Abstract. The Ordovician biodiversification is considered one of the most significant radiations in the marine ecosystems of the entire Phanerozoic. Originally recognized as the ‘Ordovician Radiation’, a label retained during most of the 1980s and 1990s, the term ‘Great Ordovician Biodiversification Event’ (GOBE) was coined in the late 1990s and was subsequently adopted by most of the scientific community. The Ordovician biodiversification, has always been considered as a long-term adaptive radiation, resulting in the sum of the different individual diversifications of all groups of marine organisms that occurred diachronously during the entire Ordovician. More recently, based on different palaeontological datasets, comprising data from different palaeogeographical areas, the Ordovician radiation has been interpreted to occur at different times in different places. This is most probably related to the palaeogeography of the Ordovician, when the major palaeocontinents were variously located in low latitudes to develop biodiversity ‘hotspots’ during different time intervals. In particular, some authors, using the potentially biased dataset of the Paleobiology Database (PBDB), have considered the GOBE to be an early Middle Ordovician global bio-event. Accordingly, the GOBE thus apparently corresponds to a relatively short time interval, with dramatic diversity fluctuations resulting in a profound change in marine environments at a global scale, visible by a major pulse in biodiversification of all fossil groups around the world. A critical analysis of the published biodiversity curves and of our own data confirm the traditional view; the Ordovician radiation is a complex, long-term process of multiple biodiversifications of marine organisms. Rapid increases in diversity can be identified for some fossil groups, at regional or palaeocontinental levels, in particular within limited datasets. However, a short, dramatic event that triggered major biodiversity pulses of all fossil groups at a global level at a particular time interval is an oversimplification.
摘要奥陶纪生物多样性被认为是整个显生宙海洋生态系统中最重要的辐射之一。最初被认为是“奥陶纪辐射”,这个标签在20世纪80年代和90年代的大部分时间里都保留着,“大奥陶纪生物多样化事件”(GOBE)一词是在20世纪90年代末创造的,随后被大多数科学界采用。奥陶纪生物多样性一直被认为是一种长期的适应性辐射,它导致了整个奥陶纪不同时期海洋生物群不同个体多样性的总和。最近,根据不同的古生物学数据集,包括来自不同古地理区域的数据,奥陶纪辐射被解释为在不同的时间、不同的地方发生。这很可能与奥陶纪的古地理有关,当时主要的古大陆位于不同的低纬度地区,以在不同的时间间隔内形成生物多样性的“热点”。特别是,一些作者使用古生物学数据库(PBDB)的潜在偏见数据集,认为GOBE是中奥陶世早期的全球生物事件。因此,GOBE显然对应于一个相对较短的时间间隔,多样性的剧烈波动导致全球范围内海洋环境的深刻变化,世界各地所有化石群的生物多样性都出现了重大变化。对公布的生物多样性曲线和我们自己的数据的批判性分析证实了传统观点;奥陶纪辐射是一个复杂、长期的海洋生物多样性过程。在区域或古大陆层面,特别是在有限的数据集内,可以发现一些化石群的多样性迅速增加。然而,在特定的时间间隔内,一个短暂而戏剧性的事件在全球范围内引发了所有化石群的主要生物多样性脉冲,这是一个过于简单化的说法。
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引用次数: 36
Special Issue “Renaissance for Paleozoic Evolution Studies: Radiation and Extinction”: Preface 特刊《古生代演化研究的复兴:辐射与灭绝》:前言
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-10-01 DOI: 10.2517/2021PR002
Y. Isozaki
Familiar landscapes with diverse biota first appeared on our planet through rapid biodiversification immediately after the termination of the Precambrian world, about 540 Myr ago. Since then the first 300 Myr of the Phanerozoic, i.e., the Paleozoic Era, witnessed irreversible changes in global environment in association with the expansion and diversification of eco-spaces, both on land and in the oceans. The causes and processes of this unidirectional evolutionary history during the Paleozoic have often been attributed to multiple punctuated episodes, each of which triggered global-scale environmental changes to constrain the direction of evolution. For example, the Cambrian explosion, the Great Ordovician Biodiversification Event (GOBE), and three major mass extinctions, at the end of the Ordovician, Devonian, and Permian, respectively, are attractive clichés/concepts for these unusual changes that have become extremely popular, not only among professional scientists, but also with journalists. Such elevated interest in Earth history was ignited by some iconic contributions; i.e., the Cambrian Explosion (Gould, 1989), the bolide impact story for the end-Cretaceous timing (Alvarez et al., 1980), the visualization of long-term biodiversity patterns in a clear diagram (Raup and Sepkoski, 1982), and the snowball Earth hypothesis (Kirschvink, 1992; Hoffman and Schrag, 1998). The search for possible causes/drivers of these “big events” of the Paleozoic has continued, yielding numerous scientific articles. In addition to extraterrestrial impact, several stimulating ideas such as ocean redox change and intermittent supervolcanism were proposed as possible key mechanisms during the 1990s; nonetheless, interest started to decline in this century. What remains at present is a huge pile of similar data produced by the same analytical techniques, particularly with various geochemical/isotopic proxies, and many similar discussions from almost the same viewpoints. This may reflect the current overemphasis on quantitative measures for evaluating research, such as the number of citations and journal impact factors, in the scientific community (Garfield, Special Issue “Renaissance for Paleozoic evolution studies: radiation and extinction”: Preface
大约5.4亿年前,前寒武纪世界结束后,通过快速的生物多样性,我们的星球上首次出现了具有多样生物群的熟悉景观。从那时起,显生宙的前300 Myr,即古生代,见证了全球环境的不可逆转的变化,伴随着陆地和海洋生态空间的扩张和多样化。古生代这种单向进化史的原因和过程通常被归因于多个间断的事件,每一个事件都引发了全球范围的环境变化,以限制进化的方向。例如,寒武纪大爆发、奥陶纪生物多样性大事件(GOBE)以及分别发生在奥陶纪、泥盆纪和二叠纪末的三次大灭绝,都是这些不同寻常的变化的吸引人的陈词滥调/概念,这些变化不仅在专业科学家中,而且在记者中都非常流行。一些标志性的贡献点燃了人们对地球历史的兴趣;即寒武纪大爆发(Gould,1989)、白垩纪末期的玻利维亚撞击故事(Alvarez et al.,1980)、清晰图表中长期生物多样性模式的可视化(Raup和Sepkoski,1982)以及雪球地球假说(Kirschvink,1992;Hoffman和Schrag,1998)。对古生代这些“大事件”的可能原因/驱动因素的研究仍在继续,发表了大量科学文章。除了地外撞击外,20世纪90年代还提出了海洋氧化还原变化和间歇性超级火山活动等可能的关键机制;尽管如此,在本世纪,人们的兴趣开始下降。目前剩下的是由相同的分析技术产生的大量类似数据,特别是使用各种地球化学/同位素替代物,以及从几乎相同的角度进行的许多类似讨论。这可能反映了科学界目前过于强调评估研究的定量指标,如引用次数和期刊影响因素(Garfield,特刊“古生代进化研究的复兴:辐射与灭绝”:序言
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引用次数: 0
Palynofloras from the Itsuki and Kuwajima Formations of the Tetori Group and their Correlation with Paleofloristic Provinces of Eastern Asia Tetori群Itsuki组和Kuwajima组的Palynofloras及其与东亚古植物区系的相关性
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-07-01 DOI: 10.2517/2020PR017
J. Legrand, Toshihiro Yamada, K. Terada, H. Nishida
Abstract. We collected samples from the middle part of the Tetori Group and obtained diverse spores (28 species) and gymnosperm pollen (8 species) from the Barremian Itsuki and Kuwajima formations. This is the first report of Barremian palynofloras from the Tetori-type floristic province in Japan and we compared them to coeval ones from the Ryoseki-type floristic province. These palynofloras include various cyathealean spores and cheirolepidiaceous pollen, indicating that floristic differences between the Tetori- (Inner Zone) and Ryoseki-type (Outer Zone) provinces are not so distinct during the Barremian in Japan. They also show similarities with floras of the Sindong Group of the Gyeongsang Basin, southeast Korea and Shitouhezi Formation in northeast China, thus indicating that some Ryoseki-type elements may have extended their distribution northward in the Barremian.
摘要我们从Tetori群的中部采集了样本,并从Barremian Itsuki和Kuwajima地层中获得了不同的孢子(28种)和裸子植物花粉(8种)。本文首次报道了日本哲藤型植物区系省的Barremian孢粉植物群,并将其与琉森型植物区区系省同期的孢粉植物群进行了比较。这些孢粉植物群包括各种苏铁藻孢子和cheirolepidiacic花粉,这表明在日本巴雷米安时期,Tetori-(内区)和Ryoseki型(外区)省份之间的区系差异并不那么明显。它们还与朝鲜东南部庆尚盆地辛洞组和中国东北部石头河子组的植物群相似,表明一些龙崎型元素可能在巴雷米安向北扩展了分布。
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引用次数: 1
Morphological Study of Qaidamestheria (Spinicaudata) from the Middle Jurassic in Qinghai, Northwestern China 青海中侏罗世Qaidamesheria(Spinicaudata)的形态学研究
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-07-01 DOI: 10.2517/2020PR019
Xiao Teng, Gang Li
Abstract. The Triglypta–Qaidamestheria clam shrimp assemblage, widely known from the non-marine Jurassic deposits in northern China, is important for biostratigraphic correlation of the fossil bearing strata. Qaidamestheria Wang, 1983, an essential component of the assemblage, was originally described from the upmost oil shale member of the Dameigou Formation at the northern margin of the Qaidam Basin, northwest China. Though the original description of the genus Qaidamestheria was based on SEM microscopy, the published pictures of the type specimens are unclear, and the type specimens were lost. We collected new specimens of the type species Qaidamestheria dameigouensis Wang, 1983 from the 7th unit of the Dameigou Formation in the Dameigou section, where the holotype of the species was originally collected. The examination of the specimens under SEM has revealed three critical taxonomic features for the genus: the fine reticulation (mesh diameter 7–18 µm) on the larval valve and several adjacent growth bands; the transitional (reticulated-punctate) ornamentation on the middle–ventral part of the carapace; and linearly arranged puncta appearing only on growth bands near the antero-ventral margin of the carapace, puncta never clustered.
摘要Triglypta–Qaidamestheria蛤虾组合广泛分布于中国北部的非海相侏罗系矿床中,对含化石地层的生物地层学对比具有重要意义。Qaidamesheria Wang,1983,是该组合的重要组成部分,最初描述于中国西北柴达木盆地北缘大美沟组最上部的油页岩段。尽管最初对Qaidamestheria属的描述是基于SEM显微镜,但已公布的模式标本图片尚不清楚,模式标本已丢失。我们在大梅沟剖面的大梅沟组第7单元采集了模式种Qaidamestheria dameigouensis Wang的新标本,1983年,该物种的正模是在这里采集的。扫描电镜下对标本的检查揭示了该属的三个关键分类特征:幼虫瓣膜上的细网状(网孔直径7-18µm)和几个相邻的生长带;甲中腹侧的过渡(网状点状)纹饰;线状排列的点状仅出现在甲前腹缘附近的生长带上,点状从不成簇。
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引用次数: 3
Smithian (Olenekian, Early Triassic) Conodonts from Ammonoid-Bearing Limestone Blocks at Crittenden Springs, Elko County, Nevada, USA 美国内华达州埃尔科县Crittenden Springs含氨石灰岩块中的Smithian(Olenekian,三叠纪早期)牙形刺
IF 0.9 4区 地球科学 Q3 PALEONTOLOGY Pub Date : 2021-07-01 DOI: 10.2517/2020PR022
T. Maekawa, J. Jenks
Abstract. The ammonoid-bearing limestone blocks at the classic Crittenden Springs ammonoid site belong to the lower part of the Lower Triassic Thaynes Group. These 0.5–1.2 m thick blocks, consisting mainly of bioclastic floatstone and rudstone, contain abundant macro- and micro-fossils such as ammonoids, gastropods, bivalves and scaphopod shells, as well as conodont elements, fish and echinoid remains. Ammonoid and conodont assemblages obtained from three blocks are utilized for biostratigraphical analysis. Twelve informal Smithian ammonoid biostratigraphic intervals from a previous study are condensed into four ammonoid beds, based on the range of age-diagnostic taxa, in ascending order: Meekoceras millardense-M. aff. olivieri beds, Owenites koeneni beds, Anasibirites multiformis bed, and Condensoceras youngi bed. Conodonts recovered from the three blocks consist of 30 species distributed among 15 genera, including one newly described taxon, i.e., Guangxidella minuta Maekawa and Jenks sp. nov. The blocks are divided into two conodont interval zones, i.e., the Novispathodus ex gr. waageni Interval Zone and Nv. pingdingshanensis Interval Zone, based on the first occurrences of their eponymous taxa. Additionally, four conodont range zones, i.e., the Paullella meeki Range Zone, Guangxidella bransoni Range Zone, Scythogondolella milleri Range Zone, and Borinella buurensis Range Zone are recognized, based on the ranges of these four index species. Conodonts within these interval and range zones vary in age from middle Smithian to latest Smithian. The presence of key ammonoid and conodont taxa regarding the Smithian-Spathian boundary (SSB) such as the AW (Anasibirites and Wasatchites) and GXP (Glyptophiceras, Xenoceltites and Pseudosageceras) ammonoid assemblages and the conodonts B. buurensis, Nv. pingdingshanensis and S. milleri demonstrate that the study area is an important reference site for the SSB in the eastern Panthalassa area.
摘要克里滕登斯普林斯(Crittenden Springs)菊石遗址的含菊石石灰岩块体属于下三叠统泰内斯群(Thaynes Group)的下部。这些0.5-1.2米厚的块体主要由生物碎屑浮石和乳石岩组成,包含丰富的宏观和微观化石,如菊石类、腹足类、双壳类和舟足类贝壳,以及牙形刺元素、鱼类和棘皮动物遗骸。利用从三个区块获得的菊石和牙形石组合进行生物地层学分析。根据年龄诊断分类群的范围,先前研究中的12个非正式史密斯安菊石生物地层学区间被浓缩为四个菊石层,按升序排列:Meekoceras millardense-M。aff。olivieri床、Owenites koeneni床、Anasibirites多形性床和Condenseceras youngi床。从三个区块中发现的牙形石由30种组成,分布在15个属中,其中包括一个新描述的分类单元,即Guangxidella minuta Maekawa和Jenks sp.nov。这些区块分为两个牙形石间隔带,即Novispathodus ex gr.waageni间隔带和Nv。平顶山间隔带,基于其同名分类群的首次出现。此外,根据这四个指数物种的范围,还识别出四个牙形刺山脉带,即Paullella meeki山脉带、Guangxidella bransoni山脉带、Scythogondolella milleri山脉带和Borinella buurensis山脉带。这些间隔带和范围带内的牙形石的年龄从史密阶中期到史密阶晚期不等。Smithian-Spathian边界(SSB)的主要菊石和牙形石分类群的存在,如AW(Anasibirites和Wasatchites)和GXP(Glyptofereras、Xenocerites和Pseudosageceras)菊石组合以及牙形石B.buurensis,Nv。平定山和米氏S.milleri表明,该研究区是Panthalassa东部地区SSB的重要参考点。
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引用次数: 8
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Paleontological Research
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