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1.
For modern lineages of birds and mammals, few fossils have been found that predate the Cretaceous-Palaeogene (K-Pg) boundary. However, molecular studies using fossil calibrations have shown that many of these lineages existed at that time. Both birds and mammals are parasitized by obligate ectoparasitic lice (Insecta: Phthiraptera), which have shared a long coevolutionary history with their hosts. Evaluating whether many lineages of lice passed through the K-Pg boundary would provide insight into the radiation of their hosts. Using molecular dating techniques, we demonstrate that the major louse suborders began to radiate before the K-Pg boundary. These data lend support to a Cretaceous diversification of many modern bird and mammal lineages.  相似文献   

2.
This paper reviews the numerous papers published from mid 1975 to mid 1976 concerned with the origin of angiosperms, and concludes that the subject is now fairly in the hands of palaeobotanists once again. No immediate solution is yet available, but thorough search of the fossil record which has now begun will provide a solution as long as evidence which is entirely from Recent plants is kept separate and is not confused with genuine fossil record information. Preliminary information and illustrations are provided for columellate semi-tectate pollen of the Clavatipollenites-Retimonocolpites group recently found in the English Wealden of presumed Barremian age below samples with already published records. These fossils are of importance as being perhaps the earliest angiosperm pollen so far recorded; their timecorrelation is not yet settled but can almost certainly be improved through further palynological work. Albian and later fossils are not discussed.  相似文献   

3.
我国东北地区更新世野牛化石的发现已有近一个世纪历史, 尽管先后有不少零星报道, 但至今无一篇专门文献, 并且前人报道的头骨化石材料无一是完整的。本文记述了保存基本完好的2件野牛头骨和3件下颌骨; 化石来自吉林省乾安县大布苏地区, 地质时代为距今约2万年。基于其形态特征和测量数据, 本文将其归入草原野牛Bison priscus(Bojanus, 1827)。前人将东北平原晚更新世野牛归入Bison exiguus Matsumoto, 1915的做法存在诸多问题, 因为后者在模式产地、地质时代及形态特征等方面都与东北晚更新世的野牛差异甚大。我国东北平原晚更新世的野牛应归入草原野牛种, 该种是中-晚更新世广泛分布于全北区的种类, 也是猛犸象-披毛犀动物群的最主要成员之一。  相似文献   

4.
Known Proterozoic algal fossils raise compelling questions about the origin and diversification of cyanobacteria and eukaryotic algae, and their ecological influence in deep time. This Perspectives article describes particular examples of persistent evolutionary and biogeochemical issues whose resolution would be aided by additional algal fossil evidence from Proterozoic deposits, which have been the subjects of recent intensive study. New Proterozoic geosciences literature relevant to the early diversification of algae is surveyed. Previously underappreciated algal traits that might improve taxonomic attributions of fossil remains are highlighted. Processes that phycologists could use to improve detection of algal fossils are recommended. Potential geological sources of new Proterozoic fossils are suggested.  相似文献   

5.
The fossil record of Lauraceae can be traced back to the Early Cretaceous of eastern Asia based on fossil flowers. Here, we refer a number of new occurrences of leaf and fruit fossils of Lauraceae from the Middle Miocene of Zhangpu, Fujian, China, to seven species. These data provide evidence supporting the fact that a diverse subtropical, or tropical, Lauraceae-dominated evergreen forest surrounded this region 15 million years ago (Mya). The Lauraceae fossils presented in this paper provide evidence for the evolution of this group as well as new materials that enable the study of the Fujian Province Neogene flora. The fossils described in this paper fill in the gaps in studies about Lauraceae pollen in the Middle Miocene from Fotan, Fujian, China. In addition, these fossils also enrich the Middle Miocene fossil records of Lauraceae in eastern Asia, especially improving the study of the macrostructures and reproductive organs of fossil Lauraceae from southern China. The similarity between fossil and modern fruits shows that during the Middle Miocene the fruit morphological of Lauraceae have changed very little. We also identify families where the fossils we report belong to their closest relatives and can be used to reconstruct the paleoenvironment of Fujian in the Middle Miocene.  相似文献   

6.
In the South African context, computed tomography (CT) has been used applied to individually prepared fossils and small rocks containing fossils, but has not been utilized on large breccia blocks as a means of discovering fossils, and particularly fossil hominins. Previous attempts at CT imaging of rocks from other South African sites for this purpose yielded disappointing results. For this study, 109 fossil- bearing rocks from the site of Malapa, South Africa were scanned with medical CT prior to manual preparation. The resultant images were assessed for accuracy of fossil identification and characterization against the standard of manual preparation. The accurate identification of fossils, including those of early hominins, that were not visible on the surface of individual blocks, is shown to be possible. The discovery of unexpected fossils is reduced, thus lowering the potential that fossils could be damaged through accidental encounter during routine preparation, or even entirely missed. This study should significantly change the way fossil discovery, recovery and preparation is done in the South African context and has potential for application in other palaeontological situations. Medical CT imaging is shown to be reliable, readily available, cost effective and accurate in finding fossils within matrix conglomerates. Improvements in CT equipment and in CT image quality are such that medical CT is now a viable imaging modality for this palaeontological application.  相似文献   

7.
The taxonomic treatment of trace fossils needs a uniform approach, independent of the ethologic groups concerned. To this aim, trace fossils are rigorously defined with regard to biological taxa and physical sedimentary structures. Potential ichnotaxobases are evaluated, with morphology resulting as the most important criterion. For trace fossils related to bioerosion and herbivory, substrate plays a key role, as well as composition for coprolites. Size, producer, age, facies and preservation are rejected as ichnotaxobases. Separate names for undertracks and other poorly preserved material should gradually be replaced by ichnotaxa based on well-preserved specimens. Recent traces may be identified using established trace fossil taxa but new names can only be based on fossil material, even if the distinction between recent and fossil may frequently remain arbitrary. It is stressed that ichnotaxa must not be incorporated into biological taxa in systematics. Composite trace fossil structures (complex structures made by the combined activity of two or more species) have no ichnotaxonomic standing but compound traces (complex structures made by one individual tracemaker) may be named separately under certain provisions. The following emendations are proposed to the International Code of Zoological Nomenclature: The term 'work of an animal' should be deleted from the code, and ichnotaxa should be based solely on trace fossils as defined herein.  相似文献   

8.
牛亚科动物在中国第四纪古人类遗址中十分常见,但其分类和鉴定仍存在诸多问题。南方洞穴动物群经常仅有单个牙齿保存,所以南方更新世洞穴遗址中牛亚科动物化石鉴别问题更为突出。湖北郧西白龙洞古人类遗址出土的大型牛亚科动物化石,不仅有大量单个牙齿,还有残破颅骨、角心、下颌骨及头后骨骼。白龙洞的牛亚科动物角心粗短、横截面呈背腹略扁的椭圆形;额骨上的角间隆突发育且呈拱形;顶骨从颅顶退出;枕面较圆且高;角后颅骨收缩强烈使得枕骨上部变窄,颞窝明显凹进;下颌角大于90°,下颌支向后倾斜;下颌p2的结构复杂程度介于水牛Bubalus和黄牛Bos(Bos)taurus之间。依据上述特征,可将白龙洞的大型牛亚科动物化石归入大额牛Bos(Bibos)gaurus。白龙洞是我国出土大额牛化石最为丰富的古人类遗址,为区分南方洞穴出土的牛亚科动物化石提供了重要材料。  相似文献   

9.
Larry Martin's glorious life and career came to a premature end on March 9,2013 at the age of 69.He was truly a rare,well-rounded,and great paleontologist.He published about 400 scientific contributions,including over 250 peer-reviewed papers that cover such a wide range of fields as avian fossils and evolution,Quaternary paleoenvironments and community evolution,paleoclimate and evolution,fossil rodents and carnivores,fossil history of bone disease,and Plains Indians.  相似文献   

10.
It is widely acknowledged that integrating fossils into data sets of extant taxa is imperative for proper placement of fossils, resolution of relationships, and a better understanding of character evolution. The importance of this process has been further magnified because of the crucial role of fossils in dating divergence times. Outstanding issues remain, including appropriate methods to place fossils in phylogenetic trees, the importance of molecules versus morphology in these analyses, as well as the impact of potentially large amounts of missing data for fossil taxa. In this study we used the angiosperm clade Juglandaceae as a model for investigating methods of integrating fossils into a phylogenetic framework of extant taxa. The clade has a rich fossil record relative to low extant diversity, as well as a robust molecular phylogeny and morphological database for extant taxa. After combining fossil organ genera into composite and terminal taxa, our objectives were to (1) compare multiple methods for the integration of the fossils and extant taxa (including total evidence, molecular scaffolds, and molecular matrix representation with parsimony [MRP]); (2) explore the impact of missing data (incomplete taxa and characters) and the evidence for placing fossils on the topology; (3) simulate the phylogenetic effect of missing data by creating "artificial fossils"; and (4) place fossils and compare the impact of single and multiple fossil constraints in estimating the age of clades. Despite large and variable amounts of missing data, each of the methods provided reasonable placement of both fossils and simulated "artificial fossils" in the phylogeny previously inferred only from extant taxa. Our results clearly show that the amount of missing data in any given taxon is not by itself an operational guideline for excluding fossils from analysis. Three fossil taxa (Cruciptera simsonii, Paleoplatycarya wingii, and Platycarya americana) were placed within crown clades containing living taxa for which relationships previously had been suggested based on morphology, whereas Polyptera manningii, a mosaic taxon with equivocal affinities, was placed firmly as sister to two modern crown clades. The position of Paleooreomunnea stoneana was ambiguous with total evidence but conclusive with DNA scaffolds and MRP. There was less disturbance of relationships among extant taxa using a total evidence approach, and the DNA scaffold approach did not provide improved resolution or internal support for clades compared to total evidence, whereas weighted MRP retained comparable levels of support but lost crown clade resolution. Multiple internal minimum age constraints generally provided reasonable age estimates, but the use of single constraints provided by extinct genera tended to underestimate clade ages.  相似文献   

11.
湖南省西北部新发现的哺乳动物化石及其意义   总被引:9,自引:2,他引:7  
本文记述了在慈利县发现的金丝猴下颌骨化石标本。报道了吉首县螺丝旋山洞出土的可能是更新世晚期的哺乳动物化石及其地层的情况;比较详细地研究了早更新世晚期的保靖县洞泡山动物群。并描述了大熊猫的一个新亚种——武陵山亚种。进一步证实在华南存在一个从柳城巨猿洞动物群向狭义的“大熊猫-剑齿象动物群”过渡类型的动物群。以上新发现的更新世哺乳动物化石及其地层对于湖南(尤其是湘西)第四纪的研究提供了重要资料  相似文献   

12.
We describe lark (Alaudidae) fossils from the upper Pliocene of the Beregovaya (southern Transbaikalia) and Shaamar (northern Mongolia) localities. The presence of 4 extinct forms in these localities is established, including the new fossil horned lark Eremophila orkhonensis (Zelenkov et Kurochkin, 2012), comb. nov. This is the oldest member of Eremophila in the fossil record, indicating a possible Central Asian origin of the genus. Two other larks Alaudala aff. A. rufescens and Calandrella aff. C. brachydactyla also probably represent extinct forms. The paper describes in detail the osteology of larks and compares it with other passerines in its size class. The evolutionary history of Eremophila is discussed, and the environmental preferences of larks and their relationship to the late Pliocene landscapes of Central Asia are considered.  相似文献   

13.
From time to time, small, fragile, previously unknown fossil invertebrates are found in specialized habitats. Occasionally, as in the present case, a fragment of the original habitat that existed millions of years ago is also preserved. The present article describes a previously unknown microinvertebrate in Dominican amber that cannot be placed in any group of extant invertebrates. Placed in a new family, genus, and species, the fossil shares characters with both tardigrades and mites, but clearly belongs to neither group. The several hundred fossil individuals preserved in the amber shared their moist, warm habitat with pseudoscorpions, nematodes, fungi, and protozoa. The large number of fossils provided additional evidence of their biology, including their reproductive behavior, developmental stages, and food. While there is no extant group that can accommodate these fossils, and we have no knowledge of any extant descendants, this discovery shows that unique lineages of minute invertebrates were surviving in the mid‐Tertiary.  相似文献   

14.
In the past an ‘explosion’ in diversity and abundance of small shelly fossils and of trace fossils has served to mark the base of the Cambrian. However, no evidence has been presented to prove that the ‘explosions’ of the two groups were synchronous. We describe small shelly fossils and trace fossils from the same phosphatic limestone beds that indicate that the two events were separate in time. The small shelly fossils are Anabarites trisulcatus, Hyolithellus cf. H. isiticus, Microcornus? sp., Protohertzina anabarica, P. unguliformis, P. sp. A, Pseudorthotheca sp. A, Rushtonia? sp. A, four types of tuberculate plates and one type of reticulate plate. These fossils represent a restricted, ‘pre-explosion’ fauna and are assigned to the Anabarites-Circotheca-Protohertzina Assemblage Zone, an uppermost Precambrian zone in the Meishucun Stage, Yunnan Province, China. A point at the top of this zone has received strong international endorsement for future designation as the base of the Cambrian. Associated with the small shelly fossils are the trace fossils Cruziana sp. A, Cruziana? sp. B, Rusophycus sp. A, Palaeophycus rubdark and arthropod scratch marks. If found in isolation, this trace fossil assemblage would be considered as post-Precambrian because it includes large, highly organized arthropod traces that are traditionally accepted as occurring above the trace fossil ‘explosion’. We therefore conclude that the trace fossil ‘explosion’ predates the small shelly fossil ‘explosion’. If the proposed location of the base of the Cambrian in Yunnan is accepted, the small shelly fossil ‘explosion’ concept and its relationship to the boundary would not be greatly modified. The trace fossil ‘explosion’, however, would no longer indicate the base of the Cambrian and the ranges of some trace fossils would be extended into the Precambrian.  相似文献   

15.
该文记述了国际前寒武系-寒武系界线层型候选剖面所在地,湖北宜昌震旦系-寒武系界线地层中发现的小刺球藻类化石Micrhystridium regulare,regulare,讨论了它们的产出层位及其归属,并对小刺球藻类化石在时间上、空间上的分布作了简要的归纳,最后提出了小刺球藻类化石在震旦系-寒武系界线地层的划分和大区域地层对比中重要的潜在作用。  相似文献   

16.
Kinchloe Roberts et al. (2008) proposed a technique, using outline-morphometric and linear analyses to permit identification of spider compression fossils to family level. This work focussed on fossil spiders from the Florissant Formation, Colorado, but the aim was to investigate a technique that would be broadly applicable to any compression fossil deposit. Essentially, what they were trying to accomplish was a shortcut for use in identifying fossil spiders to family. While their claims are promising, the methodology they used was not without its limitations and the aim of our paper is to discuss these and add further insights in order to put the application of this technique into a more appropriate context than that originally claimed.  相似文献   

17.
18.
为探讨现生太行山猕猴与猕猴化石骨指数的差异,对太行山猕猴与广西崇左早更新世猕猴化石的肢间指数(Intermembral index,IM)、臂指数(Brachial index,BI)、股指数(Crural index,CI)和股骨粗壮指数(Robusticity index,RI)等指数进行比较。结果表明,猕猴化石IM值(96)高于太行山猕猴,BI值(94.5)和CI值(88.5)均低于太行山猕猴,推测该猕猴化石在早更新世时期可能地栖生活,适合于陆地四足行走,同时也验证了太行山猕猴主要为半树栖生活。结合对猕猴化石伴生哺乳动物习性的分析,推测广西崇左早更新世的气候温暖潮湿并有一定的水域,植被以森林和灌木为主,有局部的草地或草坡,其自然环境非常适宜高等灵长类生息繁衍。  相似文献   

19.
通过昆明海口马房村同一个采坑的化石连续采集和统计,对澄江化石库中两种埋藏相(以事件层泥岩和背景层泥岩所代表)内化石保存和组合特征进行定量研究,结果表明:(1)事件层内化石量并不随单一事件层厚度变化而变化。物种在剖面上不同层位的事件层内分布不均匀,表现为单层富集现象;而背景层内的化石含量与背景层的沉积厚度有关,背景层的沉积厚度越厚,化石数量就越多。(2)事件层与背景层内化石组合和结构存在很大差异。事件层内化石组合与背景层内化石组合相比具有更多的物种组成和更复杂的古群落结构;而背景层内化石组合面貌单调,在剖面上保持稳定。(3)事件层内化石生物体腐烂发生在埋藏之后,绝大多数化石生物是被活埋后保存下来的;而背景层内化石主要表现为外壳和弱矿化有机质生物表皮在海床表面长时间停滞而堆积形成,明显受到时间均衡作用(time-average)的影响。(4)事件层内化石在埋藏前无搬运作用,或发生近原栖息地的快速搬运,埋藏后无生物扰动。背景层内大量壳体相连的双瓣壳节肢动物化石和完整海绵体化石的存在则表明,背景层代表一个低氧、低能并具有有限生物扰动的沉积环境。  相似文献   

20.
激光扫描共聚焦显微镜在孢粉研究中的应用   总被引:1,自引:0,他引:1  
在MRC1000型激光扫描共聚焦显微镜下,观察具有自发荧光的孢子、花粉、沟鞭藻以及疑源类等不同时代的化石标本,发现现代和第四纪孢粉具有较强的自发荧光,古生代的孢子自发荧光强度最弱。后者很难聚焦成清晰的二维投影图像。在观察孢粉样品过程中,选择合适的激光波长及激光扫描强度是关键的技术问题。一般以氪、氩离子激发为效果最佳,以波长488,568,647nm最合适。  相似文献   

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