Whales originated from aquatic artiodactyls in the Eocene epoch of India

Although the first ten million years of whale evolution are documented by a remarkable series of fossil skeletons, the link to the ancestor of cetaceans has been missing. It was known that whales are related to even-toed ungulates (artiodactyls), but until now no artiodactyls were morphologically close to early whales. Here we show that the Eocene south Asian raoellid artiodactyls are the sister group to whales. The raoellid Indohyus is similar to whales, and unlike other artiodactyls, in the structure of its ears and premolars, in the density of its limb bones and in the stable-oxygen-isotope composition of its teeth. We also show that a major dietary change occurred during the transition from artiodactyls to whales and that raoellids were aquatic waders. This indicates that aquatic life in this lineage occurred before the origin of the order Cetacea.     

Discovery of a sensory organ that coordinates lunge feeding in rorqual whales

Top ocean predators have evolved multiple solutions to the challenges of feeding in the water. At the largest scale, rorqual whales (Balaenopteridae) engulf and filter prey-laden water by lunge feeding, a strategy that is unique among vertebrates. Lunge feeding is facilitated by several morphological specializations, including bilaterally separate jaws that loosely articulate with the skull, hyper-expandable throat pleats, or ventral groove blubber, and a rigid y-shaped fibrocartilage structure branching from the chin into the ventral groove blubber. The linkages and functional coordination among these features, however, remain poorly understood. Here we report the discovery of a sensory organ embedded within the fibrous symphysis between the unfused jaws that is present in several rorqual species, at both fetal and adult stages. Vascular and nervous tissue derived from the ancestral, anterior-most tooth socket insert into this organ, which contains connective tissue and papillae suspended in a gel-like matrix. These papillae show the hallmarks of a mechanoreceptor, containing nerves and encapsulated nerve termini. Histological, anatomical and kinematic evidence indicate that this sensory organ responds to both the dynamic rotation of the jaws during mouth opening and closure, and ventral groove blubber expansion through direct mechanical linkage with the y-shaped fibrocartilage structure. Along with vibrissae on the chin, providing tactile prey sensation, this organ provides the necessary input to the brain for coordinating the initiation, modulation and end stages of engulfment, a paradigm that is consistent with unsteady hydrodynamic models and tag data from lunge-feeding rorquals. Despite the antiquity of unfused jaws in baleen whales since the late Oligocene (～23-28 million years ago), this organ represents an evolutionary novelty for rorquals, based on its absence in all other lineages of extant baleen whales. This innovation has a fundamental role in one of the most extreme feeding methods in aquatic vertebrates, which facilitated the evolution of the largest vertebrates ever.     

Selective habituation shapes acoustic predator recognition in harbour seals

Predation is a major force in shaping the behaviour of animals, so that precise identification of predators will confer substantial selective advantages on animals that serve as food to others. Because experience with a predator can be lethal, early researchers studying birds suggested that predator recognition does not require learning. However, a predator image that can be modified by learning and experience will be advantageous in situations where cues associated with the predator are highly variable or change over time. In this study, we investigated the response of harbour seals (Phoca vitulina) to the underwater calls of different populations of killer whales (Orcinus orca). We found that the seals responded strongly to the calls of mammal-eating killer whales and unfamiliar fish-eating killer whales but not to the familiar calls of the local fish-eating population. This demonstrates that wild harbour seals are capable of complex acoustic discrimination and that they modify their predator image by selectively habituating to the calls of harmless killer whales. Fear in these animals is therefore focused on local threats by learning and experience.     

多层板的隔声特性研究

应用转移矩阵的方法，就平面声波垂直入射的情况，对具有周期结构的无限大多层板的隔声特性进行了理论分析，并对结构不同的多层板的隔声特性进行了数值模拟．理论分析和数值模拟表明：与通常隔声用的单层或双层板相比，在保持面密度不变的条件下，采用多层板结构能够在某些频段使隔声性能有明显改善，尤其体现在中高频段，但低频隔声效果稍有减弱．另外，适当调节多层板的厚度和板间的距离，可以实现对不同频段的隔声效果有所侧重．采用分区域等厚度的多层板，即采用厚、薄板相结合的复合结构，可以兼顾低频隔声性能，同时提高多层板的中高频隔声效果．在隔声结构的总体面密度和板的空间分布保持不变的情况下，换用同类的不同隔声材料对隔声特性没有明显改变，但可以适当改变隔声结构的强度．在隔声结构的设计过程中，针对不同的噪声频谱，可以采用中介绍的方法来构造相应的多层板结构，达到特定的隔声要求．研究结果对轻薄隔声结构的设计具有一定指导意义．     

Neanderthal cranial ontogeny and its implications for late hominid diversity

Homo neanderthalensis has a unique combination of craniofacial features that are distinct from fossil and extant 'anatomically modern' Homo sapiens (modern humans). Morphological evidence, direct isotopic dates and fossil mitochondrial DNA from three Neanderthals indicate that the Neanderthals were a separate evolutionary lineage for at least 500,000 yr. However, it is unknown when and how Neanderthal craniofacial autapomorphies (unique, derived characters) emerged during ontogeny. Here we use computerized fossil reconstruction and geometric morphometrics to show that characteristic differences in cranial and mandibular shape between Neanderthals and modern humans arose very early during development, possibly prenatally, and were maintained throughout postnatal ontogeny. Postnatal differences in cranial ontogeny between the two taxa are characterized primarily by heterochronic modifications of a common spatial pattern of development. Evidence for early ontogenetic divergence together with evolutionary stasis of taxon-specific patterns of ontogeny is consistent with separation of Neanderthals and modern humans at the species level.     

进化速率的研究与进化理论的统一

不同进化学说之间的争论大多与进化速率问题有关。在生物组织的不同层次上的进化速率研究得出了截然不同的结论,并导致相关的进化学说之间的互不相容。恒速的、匀速的、随机的分子进化(中性说)与非匀速的、适应的表型进化相矛盾;在自然选择作用下的渐进的适应进化(综合论)难以解释古生物记录所揭示的停滞与跳跃相间的、有时是爆发式的大进化现象。这些矛盾大多源于对进化速率的度量的不同,各层次的进化速率的含义也不同,各学说之间缺乏统一语言。生命史的重大进化事件发生的时间表显示出明显的非匀速特征：绝大多数重大进化事件发生在生命史的早期(40至35亿年前)和晚期(7亿年以近)。前生命的化学进化、生命起源、细胞生命的基本结构和代谢途径、以及生物进化和地球生物圈赖以建立的基础早在生命史开始后的几亿年内就已完成或确立了;复杂的高级生命和生物多样性的产生与重要的结构的进化革新发生在生命史末端的数亿年间。本文将宏进化的这种非匀速现象解释为地球生命与地球环境协进化的结果。当前进化理论的分裂是由生命科学及相关科学的发展所引起的,进化理论也必将随着各学科领域研究的深入而走向统一,走向新的综合。     

音乐厅音质设计

音乐厅音质设计除了和其他有音质要求的建筑一样满足一些共同要求外,本文就其音质设计在体型设计、声扩散处理和演奏台设计等方面进行了探讨．体型设计将影响直达声、早期友射声和混响声在时间和空间上的分布．较宽频率范围的声扩散程度是音质优美的关键．演奏台则主要是为乐队各声部提供良好的平衡     

Ferns diversified in the shadow of angiosperms

The rise of angiosperms during the Cretaceous period is often portrayed as coincident with a dramatic drop in the diversity and abundance of many seed-free vascular plant lineages, including ferns. This has led to the widespread belief that ferns, once a principal component of terrestrial ecosystems, succumbed to the ecological predominance of angiosperms and are mostly evolutionary holdovers from the late Palaeozoic/early Mesozoic era. The first appearance of many modern fern genera in the early Tertiary fossil record implies another evolutionary scenario; that is, that the majority of living ferns resulted from a more recent diversification. But a full understanding of trends in fern diversification and evolution using only palaeobotanical evidence is hindered by the poor taxonomic resolution of the fern fossil record in the Cretaceous. Here we report divergence time estimates for ferns and angiosperms based on molecular data, with constraints from a reassessment of the fossil record. We show that polypod ferns (> 80% of living fern species) diversified in the Cretaceous, after angiosperms, suggesting perhaps an ecological opportunistic response to the diversification of angiosperms, as angiosperms came to dominate terrestrial ecosystems.     

A paleontological perspective of vertebrate origin

The Early Cambrian Haikouichthys and Haikouella have been claimed to be related to contribute in an important way to our understanding of vertebrate origin,but there have been heated debates about how exactly they are to be interpreted. New discoveries of numerous specimens of Haikouichthys not only confirm the identity of previously described structures such as the dorsal and the ventral fins, and chevron-shaped myomeres, but also reveal many new important characteristics, including sensory organs of the head (e.g. large eyes), and a prominent notochord with differentiated vertebral elements. This “first fish” appears, however, to retain primitive reproductive features of acraniates, suggesting that it is a stem-group craniates. A new order (Myllokunmingiida) and a new family (Myllokunmingiidae) are erected, and a new species, Zhongjianichthys rostratus (gen. et sp. nov.), is described herein. Over 1400 newly-discovered specimens of Haikouella provide a wealth of anatomical information on this organism. It differs from chordates in many organs and organ systems, including the skin, muscles, respiratory, circulatory and nervous systems.In contrast, its body-design resembles that of vetulicolians,and the presence of a “transitional” nervous system with both dorsal and ventral nerve cords suggests an affinity with living hemichordates. On the basis of these and other recent findings of fossil deuterostomes, a five-step hypothesis for vertebrate origin is proposed, intended to bridge the long-standing gap between protostomes and vertebrates. Four of the five steps accord with established ideas current in modern evolutionary zoology. Evidence for the first step is obtainable only from fossils, and specifically from fossils found from South China, hence the crucial importance of S. China sites for our understanding of early vertebrate origins and evolution. Accordingly, South China is suggested as the oldest-known birthplace of the whole vertebrates.     

用声学方法测量气液混相物质中的含气量

用几种频率的声波测定了气白油、气水混相物质中的声速和声透射损失。结果发现，声速比值随含气量的增加而变小，但变化幅度不大，不宜用声速比值来反映混相物质中的含气量；而声透射损失随含气量的增加而急剧增大，在气泡大小、分布一定的情况下，可以用声透射损失来反映混相物质中的含气量。     

A eudicot from the Early Cretaceous of China

The current molecular systematics of angiosperms recognizes the basal angiosperms and five major angiosperm lineages: the Chloranthaceae, the magnoliids, the monocots, Ceratophyllum and the eudicots, which consist of the basal eudicots and the core eudicots. The eudicots form the majority of the angiosperms in the world today. The flowering plants are of exceptional evolutionary interest because of their diversity of over 250,000 species and their abundance as the dominant vegetation in most terrestrial ecosystems, but little is known of their very early history. In this report we document an early presence of eudicots during the Early Cretaceous Period. Diagnostic characters of the eudicot fossil Leefructus gen. nov. include simple and deeply trilobate leaves clustered at the nodes in threes or fours, basal palinactinodromous primary venation, pinnate secondary venation, and a long axillary reproductive axis terminating in a flattened receptacle bearing five long, narrow pseudo-syncarpous carpels. These morphological characters suggest that its affinities are with the Ranunculaceae, a basal eudicot family. The fossil co-occurs with Archaefructus sinensis and Hyrcantha decussata whereas Archaefructus liaoningensis comes from more ancient sediments. Multiple radiometric dates of the Lower Cretaceous Yixian Formation place the bed yielding this fossil at 122.6-125.8 million years old. The earliest fossil records of eudicots are 127 to 125 million years old, on the basis of pollen. Thus, Leefructus gen. nov. suggests that the basal eudicots were already present and diverse by the latest Barremian and earliest Aptian.     

A Chengjiang-type fossil assemblage from the Hongjingshao Formation （Cambrian Stage 3） at Chenggong,Kunming, Yunnan

A new Chengjiang-type fossil assemblage is reported herein from the lower part of the Hongjingshao Formation at Xiazhuang village of Chenggong,Kunming,Yunnan.The fossil assemblage,named as Xiazhuang fossil assemblage,yields predominantly soft-bodied fossils,including arthropods,brachiopods,priapulids,lobopods and some problematic taxa,with arthropods being the most dominant group.Preservation and composition of the fossil assemblage are very similar to the typical Chengjiang biota,which is preserved in the middle Yu’anshan Formation in the large area of eastern Yunnan.The associated trilobites demonstrate that the soft-bodied fossil assemblage belongs to the late Qiongzhusian in age(Stage 3,Cambrian),suggesting that the Hongjingshao Formation is probably a diachronous lithostratigraphic unit ranging from the upper Qiongzhusian to the lower Canglangpuan stages in eastern Yunnan.The fossil assemblage from the Xiazhuang area fills up the missing link between the typical older Chengjiang biota and the younger Malong and Guanshan biotas,making eastern Yunnan a unique area in the world to reveal the early evolutionary history of animals and palaeocommunity dynamics during the‘‘Cambrian explosion’’.     

Remains of Homo erectus from Bouri, Middle Awash, Ethiopia

The genesis, evolution and fate of Homo erectus have been explored palaeontologically since the taxon's recognition in the late nineteenth century. Current debate is focused on whether early representatives from Kenya and Georgia should be classified as a separate ancestral species ('H. ergaster'), and whether H. erectus was an exclusively Asian species lineage that went extinct. Lack of resolution of these issues has obscured the place of H. erectus in human evolution. A hominid calvaria and postcranial remains recently recovered from the Dakanihylo Member of the Bouri Formation, Middle Awash, Ethiopia, bear directly on these issues. These approximately 1.0-million-year (Myr)-old Pleistocene sediments contain abundant early Acheulean stone tools and a diverse vertebrate fauna that indicates a predominantly savannah environment. Here we report that the 'Daka' calvaria's metric and morphological attributes centre it firmly within H. erectus. Daka's resemblance to Asian counterparts indicates that the early African and Eurasian fossil hominids represent demes of a widespread palaeospecies. Daka's anatomical intermediacy between earlier and later African fossils provides evidence of evolutionary change. Its temporal and geographic position indicates that African H. erectus was the ancestor of Homo sapiens.     

Absolute measures of the completeness of the fossil record

Measuring the completeness of the fossil record is essential to understanding evolution over long timescales, particularly when comparing evolutionary patterns among biological groups with different preservational properties. Completeness measures have been presented for various groups based on gaps in the stratigraphic ranges of fossil taxa and on hypothetical lineages implied by estimated evolutionary trees. Here we present and compare quantitative, widely applicable absolute measures of completeness at two taxonomic levels for a broader sample of higher taxa of marine animals than has previously been available. We provide an estimate of the probability of genus preservation per stratigraphic interval, and determine the proportion of living families with some fossil record. The two completeness measures use very different data and calculations. The probability of genus preservation depends almost entirely on the Palaeozoic and Mesozoic records, whereas the proportion of living families with a fossil record is influenced largely by Cenozoic data. These measurements are nonetheless highly correlated, with outliers quite explicable, and we find that completeness is rather high for many animal groups.     

Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia

Despite the status of the eye as an "organ of extreme perfection", theory suggests that complex eyes can evolve very rapidly. The fossil record has, until now, been inadequate in providing insight into the early evolution of eyes during the initial radiation of many animal groups known as the Cambrian explosion. This is surprising because Cambrian Burgess-Shale-type deposits are replete with exquisitely preserved animals, especially arthropods, that possess eyes. However, with the exception of biomineralized trilobite eyes, virtually nothing is known about the details of their optical design. Here we report exceptionally preserved fossil eyes from the Early Cambrian (～ 515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized 'bright zone'. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.     

Possible developmental mechanisms underlying the origin of the crown lineages of arthropods

The extraordinarily preserved, diverse arthropod fauna from the Lower Cambrian Maotianshan shale, central Yunnan (southwest China), represents different evolutionary stages stepping from stem lineages towards crown arthropods (also called euarthropods), which makes this fauna extremely significant for discussion of the origin and early diversification of the arthropods. Anatomical analyses of the Maotianshan shale arthropods strongly indicate that     

1.3亿年前早期鸟类化石揭示尾骨与扇状尾羽独立演化

 在恐龙向鸟类演化的过程中,尾骨变化最为显著,由于缺少过渡环节的化石,这一演化过程并不清楚。现代鸟类的尾骨缩短并愈合成犁状尾综骨,其上附有扇状尾羽而构成飞行器官的重要组成部分。学术界普遍认为犁状尾综骨和扇状尾羽是同步演化的。中国科学院古脊椎动物与古人类研究所王敏等报道了在河北白垩纪地层中发现的1.3亿年前的反鸟类化石,显示其具有与现代鸟类相似的犁状尾综骨,但却并不具有扇状尾羽。本研究组综合形态学、骨组织学和扫描电镜等方法,提出"犁状尾综骨与扇状尾羽在早期鸟类中相互独立"的假设,挑战了此前长期占主流的学术观点。相较于犁状尾综骨在今鸟型类的广泛发育,这一结构在部分反鸟类中的出现则是平行演化的结果,结合越来越多的其他化石证据,表明在鸟类演化早期,平行演化是一个非常普遍的现象,这也为依据骨骼形态讨论中生代鸟类的系统发育关系提出了挑战。     

A fossil owl monkey from La Venta, Colombia

Knowledge of the evolutionary history of living New World anthropoids is limited by a relatively poor fossil record. The discovery in 1986 of a new fossil monkey from the middle Miocene deposits of La Venta, Colombia, 12-15 million years ago (Myr BP), is the first example of a living New World monkey genus appearing in Tertiary rocks. Including anatomical evidence of the dentition and facial skull, it provides an unambiguous link between a Neogene fossil and the owl monkey, Aotus, the only modern crepuscular-nocturnal anthropoid primate. This new form brings to three the number of La Venta fossil monkeys which preserve excellent dentitions sharing extensive similarities with modern genera. All of these species are potentially ancestral to their extant relatives. The La Ventan Aotus is additional support for the idea that the modern platyrrhine radiation includes long-lived genera or generic lineages, some of which may be traceable to the early Miocene, 20 Myr BP.     

考虑声衰减时抗性消声器的传递矩阵

本文研究具有声能耗散时抗性消声器的传递矩阵。声能衰减的主要原因是(1)管壁的粘滞性与热传导,(2)管壁的漏声,(3)存在气流时管道载面突变处的声能损耗。文中导出包括声能衰减的传递矩阵并加以讨论,实验上采用直接堵塞法,测得的矩阵元素值与理论分析符合良好。     

基于分流电路调控的宽低频吸隔声机理研究

针对含分流电路的扬声器结构,本文研究了基于频率自适应概念扩宽吸隔声频带的理论机理. 针对扬声器隔声结构模型,揭示了在声波频率和分流电路电感所构成参数空间中存在的高隔声量轨迹,进而设计出控制电路使等效电感参数可以自适应追踪高隔声量轨迹,结果表明在低频区域的隔声带宽获得了显著扩展,将不同工作频率的自适应隔声结构组合可以进一步扩宽隔声频带. 针对扬声器吸声结构模型,发现在频率-电感参数空间同样存在高吸声轨迹,通过设计控制电路自适应追踪高吸声轨迹可以扩宽吸声频带,此外研究了扬声器与微穿孔板构成的复合吸声结构,数值结果表明在自适应吸声与微孔吸声机理的共同作用下吸声频带可被进一步扩宽。本研究为扩展扬声器结构吸隔声频带提供了新的思路,为下一步工程应用设计奠定了理论基础.