EVIDENCE FROM THE FOSSIL RECORD OF AN ANTIPREDATORY EXAPTATION: CONCHIOLIN LAYERS IN CORBULID BIVALVES

Conchiolin layers, organic-rich laminae, are characteristic of the shells of corbulid bivalves. The retention of these layers, despite their high metabolic cost, throughout the evolutionary history of Corbulidae has prompted the proposal of several adaptive scenarios to explain the origin and maintenance of these layers. The most widely held hypothesis contends that conchiolin layers are an adaptation for inhibiting drilling by predatory naticid gastropods. However, others suggest that the layers are adaptations to retard shell dissolution in waters undersaturated with calcium carbonate or to increase shell strength in the face of durophagous (shell crushing) predators. In this paper, experiments using recent Corbula (Varicorbula) gibba (Olivi) and observations of corbulids' present natural habitat demonstrate the current utility of conchiolin layers for all three functions: retardation of shell dissolution in waters undersaturated in calcium carbonate, increase of mechanical shell strength, and inhibition of drilling by predatory naticid gastropods. Earlier analyses of the extensive history of naticid predator-corbulid prey interactions suggested that conchiolin layers were an adaptation, a feature that promotes fitness and was built by selection for its current role, for deterring naticid predators. Not only are naticid drillholes widespread in fossil and recent corbulid shells, but an unusually large number of incomplete drillholes terminate unsuccessfully at conchiolin layers. In addition, a phylogenetic analysis of the origin of conchiolin layers and its function to deter naticid predators is consistent with a hypothesis of adaptation for this function. However, this hypothesis is rejected by an examination of fossil Jurassic Corbulomima. These oldest corbulids contained conchiolin layers before the evolution of naticid drilling during the Early Cretaceous. Therefore, conchiolin layers appear to be an exaptation, characters evolved for other usages and later “coopted” for their current role, for defense against drilling predators. The layers may in fact be an adaptation to resist durophagous predation.     

THE REPRODUCTIVE BIOLOGY OF RASPBERRIES AND PLANT-POLLINATOR COMMUNITY STRUCTURE

Rubus idaeus and Rubus pubescens are congeners which differ with respect to their life history patterns. Rubus idaeus is locally important in the Northeast in areas subject to windthrow, fire, and man-made disturbances, while R. pubescens often forms a significant portion of the ground cover of shaded, damp, woodland areas. The life history pattern of R. idaeus is based upon the short term build up and slow decay of a large seed bank. Vegetative reproduction is more important in the eventual spread of R. pubescens. The reproductive traits of the two species reflect many of the above mentioned constraints and differences. Rubus pubescens produces relatively small quantities of nectar and flowers during a brief 1–2-wk period late in May. Synchronous flowering probably minimizes the incidence of floral predation and makes the low nectar flowers more attractive by reducing the pollinators' flight time. Rubus idaeus is an abundant species, which offers almost unlimited supplies of nectar during at least part of its extended 3–4-month flowering season. It is attractive to a wide range of pollinators and has figured prominently in the design, phenology, and reward structure of the early successional northern hardwoods plant-pollinator community.     

多足动物亚门主要类群的谱系发生与谱系年代分析——基于形态、化石和分子的综合数据

多足动物可能是最早入侵陆地环境的无脊椎动物之一。随着泛甲壳动物大类的确立,多足动物亚门的谱系发生问题已成为节肢动物研究中的焦点。基于表型性状的系统学研究中,多足动物亚门在节肢动物门中的系统分类和单系性等问题一直存在争议;化石记录的稀少又使多足动物的起源及演化历史变得迷雾重重。近年来分子系统学的进展为深入探讨多足动物谱系发生问题开辟了新的途径;分子定年的应用为探讨多足动物起源、登陆等早期演化问题提供了新的手段。谱系年代学综合了化石记录和分子定年两方面的优势,为更加精确地讨论多足动物起源、内部类群分歧时间及其地质背景奠定了基础。谱系年代分析显示,多足动物类起源于寒武纪晚期或更早;多足动物内部类群的分歧不晚于奥陶纪;而化石证据显示,多足动物的登陆事件也可能发生在这一时期,多足动物内部类群的分歧事件(及食性分化)可能与登陆过程有关。精确的多足动物亚门谱系发生关系以及谱系年代学细节还有待于进一步综合系统学、多基因和多重化石参照点的合理分析加以深入和完善,进而为早期陆地复杂生态系统的建立提供新的证据。     

早奥陶世疑源类埋藏后的形体及纹饰变化

赖以鉴定的疑源类化石仅保留下褶皱的囊壁而原生质已流失,由于成岩过程中围岩挤压或有机质壳壁干水收缩而使化石轮廓,纹饰发生变化应普遍可见,本文以作者在贵州三都地区阿化尼克期地层发现的Striatotheca principalis保存形态连续变化系列为基础,论述埋藏作用对疑源类保存形态的影响,这是利用埋藏学资料防止属种误订的一个典型示例,对疑源类属种的正确鉴定有重要的意义。     

FLORAL INITIATION AND EARLY DEVELOPMENT IN ERIGERON PHILADELPHICUS (ASTERACEAE)

The order of floral initiation and subsequent organogeny of Erigeron philadelphicus L. (Asteraceae: Astereae) was found to deviate from the acropetal pattern generally reported for the Asteraceae. Light micrographs show periclinal divisions in the first, second, and deeper subsurface layers of cells on the flanks of the inflorescence apex as the earliest evidence of floral initiation. Scanning electron microscope micrographs indicate that the disk flowers appear first and arise as small protuberances approximately one-third of the way up the previously and undifferentiated highly convex inflorescence apex. A succession of disk flowers arises acropetally in a complex anthotaxy characterized by about 21 dextrorse and 12–15 sinistrorse parastichies (although this pattern is obscured at the apex). After one to three disk flowers have been initiated in each parastichy, the first ray flower initials can be seen to initiate in sites proximal to the oldest and largest disk flowers. Additional ray flowers then initiate basipetally following the dextrorse parastichies established by the disk flowers. Overall floral initiation on the inflorescence apex proceeds acropetally for the disk flowers and basipetally for the ray flowers until the available space is filled. Floral development adheres to the same plan—proceeding bidirectionally on the inflorescence meristem with the oldest and most complete flowers of both types located on the equator established at initiation.     

EOCENE FLORAL EVIDENCE OF LAURACEAE: CORROBORATION OF THE NORTH AMERICAN MEGAFOSSIL RECORD

Numerous megafossils of Lauraceae have been reported from the early Tertiary of North America, but the subfamilial affinities are usually not well understood due to the great morphological variability found in extant taxa. The flowers of Androglandula tennessensis gen. et sp. nov. Taylor, from the Middle Eocene Claiborne Formation, are six-parted, pedicellate, bracteate, and have stamens with paired basal staminal glands. The flowers have ethereal oil cells and paracytic stomates throughout. The fossil species has affinities with the subtribe Cinnamomineae, and this supports suggestions that the Middle Eocene climate of the southeastern U.S. was subtropical. The existence of this fossil, and reports of the subtribe from the Eocene of Europe, indicate a South American-North American-European-southeast Asian paleodistribution suggesting that extinction in North America and Europe was the cause of the tribe's current disjunct distribution.     

FOSSIL EXTRAFLORAL NECTARIES,EVIDENCE FOR THE ANT-GUARD ANTIHERBIVORE DEFENSE IN AN OLIGOCENE POPULUS

Extrafloral nectaries are secretory glands, usually found on leaves, that have been shown to promote ant defense against the insect herbivores of many modem day plants. Extrafloral nectaries were found on the 35-million-year-old fossil leaves of the extinct Populus crassa from Florissant, Colorado. Extinct ant species (belonging to five still extant genera that have modem ant-guard species), and other predators and parasitoids (whose modem relatives frequent extrafloral nectaries) also lived at Florissant. The extrafloral nectaries of P. crassa (and perhaps other plants) probably operated to attract ants and/or other arthropod defenders as early as the Oligocene.     

河北阳原、蔚县几个早更新世哺乳动物化石及旧石器地点

桑干河流域,特别是阳原、蔚县盆地的河湖相沉积,不仅发育良好,出露的面积广,厚度大,而且含有丰富的哺乳动物化石。长期以来作为我国北方第四纪早更新世的一个标准地层。近年来在这一地区,在泥河湾地层的下部一些地点,又发现了一些新的哺乳动物化石,并发现了一定数量的旧石器。这有助于进一步确定泥河湾的地层时代,为解决我国北方长期以来第四纪下限问题,为寻找人类化石提供了有利的线索。     

AN EXPERIMENTAL STUDY OF THE FLORAL ECOLOGY OF DODECATHEON MEADIA

An established colony of Dodecatheon meadia on glacial drift in southeastern Wisconsin was observed for its insect pollination interrelationships. Twelve randomly distributed plants from which insects were excluded failed to produce seed, while plants exposed to insect visits set abundant seed. Female solitary bees of 2 species, viz., Augochloropsis metallica fulgida (Smith) and Lasioglossum forbesii (Robertson), and queens and workers of 7 species of Bombus were observed collecting pollen from the pendant anther cone by rapid wing vibration, while hanging inverted from the cone tip. This behavior—cinematographically recorded—was found fundamentally identical to that of females of the same species of solitary bees and of queens and workers of 5 species of Bombus on Solanum dulcamara, and of females of Lasioglossum forbesii (Robertson) and workers of 2 species of Bombus on Lycopersicum esculentum Mill. No other insects were found to pollinate these morphologically similar flowers in this manner, and crepuscular pollinators were not observed. Experimental modifications of form, function, and position of Dodecatheon flowers were offered to the pollinators, and behavioral changes of the insects were noted. Constituents of insect pollen loads were examined, and relationships of the pollinators to the flora of the region were noted. The detailed ecological study of insect pollen vector behavior as an aid in discovering biosystematic relationships of plant populations is suggested.     

松科早期球果研究的历史与现状

本文主要对早白垩世到老第三纪渐新世这段时间的松科化石球果的研究作了系统回顾和总结。松科化石球果的研究经历了一个由分散、幼稚到系统、成熟的发展过程,现在将松科化石球果分为三个属：Ｐｉｔｙｏｓｔｒｏｂｕｓ、Ｐｓｅｕｄｏａｒａｕｃａｒｉａ及Ｐｉｎｕｓ。其中Ｐｓｅｕｄｏａｒａｕｃａｒｉａ及Ｐｉｎｕｓ为两个自然属,Ｐｓｅｕｄｏａｒａｕｃａｒｉａ已经绝灭。Ｐｉｔｙｏｓｔｒｏｂｕｓ作为一个器官属,包括那些在松科中分类位置不明的球果。对松科化石球果进行细致的外部形态及内部结构的研究主要目的在于演化关系的探讨上：对于Ｐｉｎｕｓ,主要探讨这个属内各个亚属、组、亚组之间的演化关系;对于Ｐｉｔｙｏｓｔｒｏｂｕｓ和Ｐｓｅｕｄｏａｒａｕｃａｒｉａ,通过绝灭类型的分析,探索松科内各个类群（包括绝灭的）的演化关系进而完成进化树是研究的主要方向,现在这方面已有了Ｐｉｎｕｓ中心说及Ｐｓｅｕｄｏａｒａｕｃａｒｉａ分支说两个假说。     

云南永仁更新世初期哺乳动物化石

本文记述了1974年和1978年两次在云南永仁盆地湖相地层中两个化石地点发现的四种哺乳类化石,犀牛一种,象类化石三种。同时讨论了昭通剑齿象的地质时代,记述了一新种嵌齿象。永仁化石层可与毗邻的元谋盆地“元谋组”对比,时代为更新世初期。     

山东宁阳早更新世哺乳动物化石(英文)

１９９９年,作者收到王元青博士转来胡长康老师未研究的一批哺乳动物化石。这些化石由山东省博物馆工作人员采自山东宁阳县伏山的裂隙堆积物中。根据化石围岩判断这批化石可归入同一动物群。该动物群包含１２种：松鼠科１种（Ｓｃｉｕｒｏｔａｍｉａｓ　ｓｐ．）,兔科２种（Ｂｒｅｖｉｌａｇｕｓ ｂｒａｃｈｙｐｕｓ,Ｌｅｐｕｓ ｓｐ．）,食肉目５种（Ｐａｃｈｙｃｒｏｃｕｔａ ｐｅｒｒｉｅｒｉ,Ｎｙｃｔｅｒｅｕｔｅｓ　ｓｉｎｅｎｓｉｓ,Ｃａｎｉｓ ｖａｒｉａｂｉｌｉｓ, Ｈｏｍｏｔｈｅｒｉｕｍ ｓｐ．和Ｍｅｌｅｓ ｓｐ．）,牛科２种（Ｇａｚｅｌｌａ ｓｐ．, Ｏｖｉｂｏｖｉｎａｅ ｇｅｎ ｅｔｓｐ．ｉｎｄｅｔ．）,鹿科２种（Ｃｅｒｖｕｓ　ｓｐ．,Ｃｅｒｖｉｄａｅ　ｇｅｎ　ｅｔ　ｓｐ．ｉｎｄｅｔ．）。其中,Ｐａｃｈｙｃｒｏｃｕｔａ　ｐｅｒｒｉｅｒｉ个体明显小于桑氏鬣狗（Ｐａｃｈｙｃｒｏｃｕｔａ ｌｉｃｅｎｔｉ）,ｐ２后附尖较发育,ｐ４前附尖高,ｍｌ三角座窄。四川巫山原鉴定为桑氏鬣狗的标本中至少有一件下颌骨（重庆自然博物馆,ＣＶ８７７）应当归入此种。Ｍｅｌｅｓ ｓｐ．具有较周口店第１８点发现的Ｍｅｌｅｓ ｃｈｉａｉ及中更新世常见的Ｍｅｌｅｓ　ｍｅｌ?     

中国早更新世羚牛化石记述

报道了发现于地处秦岭腹地的陕西镇安黄家湾早更新世地层中的1对羚牛角化石。标本与现生羚牛的角心很相似。角心粗壮,以110°的角向后向外侧弯曲。角心顶端背腹扁平,角尖略向上弯。秦岭可能是羚牛的起源中心。     

A CONTRIBUTION TO THE EARLY TERTIARY FOSSIL RECORD OF THE SALVINIACEAE

Megaspores and massulae of Azolla, Azollopsis, and Salvinia are recorded from the Paleocene and Eocene of Montana and the Dakotas. Three new species of Azolla are described and two species of Azolla are redescribed. The columella of the floating apparatus of the megaspore apparatuses of Azolla appears to be a phylogenetic localization of the perispore around the megaspore. A new section of Azolla (section Kremastospora) is created for species whose megaspore apparatuses have many floats and whose massulae have hooked (anchor-shaped) glochidia. Salvinia preauriculata is based only on leaf remains from the Eocene of North America. Megaspores and massulae which probably are conspecific with the leaf remains are described. The megaspores and massulae of the fossil species are much smaller than those of the living species, S. auriculata, with which S. preauriculata has been compared. The similar size of the megaspores and massulae of the fossil species suggests a less specialized condition than in living species, where these two structures differ greatly in size. Azollopsis tomentosa, previously known from the late Cretaceous, has been found in the Eocene.