特马豆克期三叶虫Dichelepyge lata Peng的个体发育

记述了产于湘西泸溪特马豆克期锅塘组的刺尾虫类三叶虫Ｄｉｃｈｅｌｅｐｙｇｅｌａｔａ的个体发育过程。其最显著的变化有头鞍形状和比例的改变，头鞍沟、颈沟与背沟的分离．鞍前箍（ｐａｒａｆｒｏｎｔａｌｂａｎｄ）的出现与消失．胸部肋区和轴部比例宽度的改变，尾部的形状和比例的变更，尾边缘的出现和肋沟深度的增加，以及后侧刺的位置逐渐前移。组成成虫期个体的前８个体节（６个胸节和前２个尾节）极有可能在分节０期（ｍｅａｓｐｉｄＤｅｇｒｅｅ０）便已形成。从分节３期（ｍｅｒａｓｐｉｄＤｅｇｒｅｅ３）起在带后侧刺的体节与轴后区（ｐｏｓｔａｘｉａｌｆｉｅｌｄ）之间又发育出一个新的体节。过渡期尾部（ｔｒａｎｓｉｔｏｒｙｐｙｇｉｄｉｕｍ）在分节０期或分节１期发育出后侧刺．在分节４期又同时长出３对侧刺，其中最后一对侧刺与后侧刺一道形成成年期尾部的尾刺。     

寒武系杷榔组Redlichia (Peteroredlichia) chinensis（Walcott，1905）个体发育研究

贵州东部寒武纪的杷榔组发育,化石丰富,含有杷榔动物群;其中掘头虫类、莱德利基虫类三叶虫保存好,序列完整,提供了研究这些类群属种个体发育的重要材料。本文据杷榔组Redlichia (Pteroredlichia) chinensis（Walcott,1905）的300多块标本的分析数据,详细讨论和重点研究了其从幼虫期、分节期至成虫期个体发育特征,分析各个阶段的形态变化及个体发育演化趋势。丰富了R.(Pteroredlichia) chinensis个体发育的资料,对莱德利基虫属种厘定起到积极的作用,提供了属种分类对比的重要证据。     

寒武系杷榔组Redlichia(Pteroredlichia)chinensis(Walcott,1905)个体发育研究

贵州东部寒武系杷榔组发育,化石丰富,产有杷榔动物群;其中掘头虫类、莱德利基虫类三叶虫保存好,序列完整,提供了研究这些类群属种个体发育的重要材料。本文据杷榔组Redlichia(Pteroredlichia)chinensis(Walcott,1905)的300多块标本的分析数据,详细讨论和重点研究了其从幼虫期、分节期至成虫期个体发育特征,分析各个阶段的形态变化及个体发育演化趋势。丰富了R.(Pteroredlichia)chinensis个体发育的资料,对莱德利基虫属种厘定起到积极的作用,提供了属种分类对比的重要证据。     

贵州黔东世(早寒武世)杷榔组Changaspis Lee in Chien,1961的再研究

掘头虫类三叶虫张氏虫ChangaspisLee in Chien,1961是黔东、湘西广泛分布的杷榔组中常见的化石。本属化石建立7个种,具有较高的多样性。近年在贵州东部地区的杷榔组采集到此属化石的大量标本,特别是在剑河交榜村的杷榔组发现了Changaspis丰富的化石,提供了分类学再研究的重要材料。据新的化石标本的详细鉴定、个体发育观测及数理统计数据的对比、化石埋藏状态的研究,Changaspis已描述的7个种是过高估计,原属C.micropygeChien,1961,C.elongataLee in Chien,1961,C.placentaQian et Lin in Zhanget al.,1980,C.longispina(Lee,in Egorovaet al.,1963),C.nangaoensisLu et Chien in Yin and Lee,1978,C.?transversaZhou in Zhouet al.,1977和C.taihuensisZhang et Zhou,1985之间形态差异并不明显。C.micropyge,C.placenta应为C.elongata的晚出同义名,而C.longispina,C.nangaoensis,C.taihuensis和C.transversa建种时化石标本少,保存不好,应是C.elongata晚出同义名。     

贵州金沙寒武系牛蹄塘组的古盘虫类三叶虫

贵州金沙寒武系牛蹄塘组产出大量古盘虫类三叶虫化石,包括分离头盖、尾部和完整背甲。依据标本中具分类鉴定意义的构造特征的测量数据比值并线性拟合,结合形态学特征、个体发育趋势等特点分析,认为Tsunyidiscus armatus和Tsunyidiscus niutitangensis两个三叶虫种是有效的,支持以尾部肋区分节差异作为两个种种征判别标志。本项研究可为厘定贵州金沙地区三叶虫Tsunyidiscus序列提供可靠证据。     

贵州剑河八郎寒武系“清虚洞组”三叶虫DuyunaspisZhangandQianinZhouetal.,1977*

Duyunaspis Zhang and Qian in Zhou et al.,1977是黔东、湘西北杷榔组掘头虫类三叶虫的重要分子。本文描述剑河八郎"清虚洞组"的Duyunaspis,这些新材料的头鞍中部膨大且向前略有收缩,前颊类型面线,成虫具10个胸节;而杷榔组的Duyunaspis duyunensis Zhang and Qian in Zhou et al.,1977头鞍桶状,背沟较平直,后颊类型面线,成虫10个胸节,二者明显不同。本文将"清虚洞组"的Duyunaspis定为一个新种:剑河都匀盾壳虫Duyunaspis jianheensis sp.nov.。研究显示,D.jianheensis与杷榔组的D.duyunensis具有形态相似性,后者可能为其祖先种。     

幼虫密度对美国白蛾生活史参数的影响

美国白蛾Hyphantria cunea原产于北美地区,1979年首次在我国辽宁省丹东地区发现,目前已扩散至江苏省南京市等地区,并有进一步扩散的趋势。由于其寄主范围广,适应能力强,危害严重,因此给我国林业生产造成了重大损失。美国白蛾1~4龄幼虫常聚集危害,4龄后开始破网分散危害。本文旨在探明幼虫密度变化对其生活史参数的影响,为解析美国白蛾种群动态变化规律提供科学依据。于温度25℃±1℃和光周期16 L∶8 D条件下,设置5头、10头、20头、40头和80头幼虫/容器5个密度处理组,待幼虫化蛹和成虫羽化后,分别检测幼虫龄期与成活率、蛹的体型（体长和体宽）与体重及成活率、成虫体型（成虫头幅宽度、前翅长度和后足腿节长度）与寿命及繁殖力等生活史参数。结果表明,幼虫密度增加缩短了幼虫发育历期,同时降低了幼虫成活率。幼虫密度增加对蛹重、蛹长、雌蛹宽度及蛹成活率有明显的负效应,但对雄蛹宽度无显著影响。幼虫密度增加对雌虫头幅宽度、雌虫繁殖力、成虫寿命与卵直径具明显负面影响,对雄虫头幅宽度与雌虫前翅长度无显著影响,对成虫后足腿节长度、雄虫前翅长度则具正面影响。因此,本研究表明幼虫密度对美国白蛾不同阶段的生活史参数具调控作用,其中幼虫密度增加对幼虫成活率、蛹的体型与体重及成活率、雌虫繁殖力与卵直径及成虫寿命的负面影响对其种群适合度可能是不利的;然而,成虫对幼虫密度增加会采取一定的适应策略,高密度条件下羽化的成虫具较长的后足腿节与前翅长度以提高其迁移扩散半径,有助于减轻子代种内竞争压力,进而提高种群适合度。     

高温对莲草直胸跳甲两个地理种群体重和体型的影响

体型大小与昆虫在温度胁迫下的适应性有关。本文旨在研究入侵杂草空心莲子草Alternanthera philoxeroides生防天敌莲草直胸跳甲Agasicles hygrophila SelmanVogt不同地理种群对高温的形态响应机制。以恒温25℃作为对照,分别测定莲草直胸跳甲长沙种群和海南种群在模拟夏季特定12∶00-16∶00时段30℃、33℃、36℃高温条件下的幼虫体重、初羽化成虫体重、后足胫节长、鞘翅长、前胸背板宽等指标。结果表明,莲草直胸跳甲两地理种群幼虫体重均随温度升高而增加。两种群雌虫及长沙种群雄虫的体重、后足胫节长、鞘翅长、前胸背板宽度随温度上升显著下降;海南种群雄虫的后足胫节长、鞘翅长、前胸背板宽在各温度处理间无显著差异。在33℃、36℃高温条件下,长沙种群的幼虫体重、雌虫体重及雌虫的后足胫节长、鞘翅长、前胸背板宽显著高于海南种群,而长沙种群雄虫的后足胫节长、鞘翅长、前胸背板宽显著低于海南种群。试验表明,不同地理种群的莲草直胸跳甲形态大小对高温的响应存在差异。本研究结果为探究莲草直胸跳甲种间进化以及人工培育耐热种群的实践提供了一定的参考依据。     

安徽淮南寒武纪一新三叶虫属——Huaiaspis

安徽淮南八公山地区寒武纪毛庄-徐庄期地层出露良好,化石丰富。在老鹰山剖面徐庄组底部的紫色页岩内所采集大量三叶虫标本中发现的一种新的三叶虫,命名为Huaiaspishuainanensisgen.etsp.nov.,它代表了一个尚未描记的且科级分类位置待定的新属新种。该三叶虫特点突出,是头部特征极度消隐且不具眼、眼叶、眼脊的“盲三叶虫”。该三叶虫为小尾型后颊类,主要特征为:壳面光滑,背壳呈次椭圆形,头盖半圆形;头鞍呈钟形向前收缩;背沟浅,仅在侧光下可见;活动颊平滑宽大,具有宽阔的活动颊刺;胸部由14节组成;尾部中轴粗壮,无边缘沟。     

Hypermecaspis(三叶虫)的蜕壳

在中国,只在浙江江山早奥陶世印渚埠组顶部的Ａｒｅｎｉｇ期发现有Ｈｙｐｅｒｍｅｃａｓｐｉｓ ａｓｉａｔａ Ｈａｎ一个种。文中的Ｈｙｐｅｒｍｅｃａｓｐｉｓ采自江山横塘塘及竹余,和江山城北４ｋｍ公路两侧的印渚埠组顶部。仅有少数标本保存有头盖,大部分只保留有自由颊、胸与尾,极少相对移位,应为原地理葬标本,所发现的Ｈｙｐｅｒｍｅｃａｓｐｉｓ几乎全为况壳标本。面线起机能作用,面线裂开,头盖与胸部分离,头盖 表     

ONTOGENY AND HETEROCHRONY IN THE EARLY CAMBRIAN ORYCTOCEPHALID TRILOBITES CHANGASPIS, DUYUNASPIS AND BALANGIA FROM CHINA

Abstract:  Ontogenies are described for the first time for three species of Early Cambrian oryctocephalid trilobites: the oryctocephaline Changaspis elongata Lee, in Chien and the oryctocarines Duyunaspis duyunensis Chang and Chien, in Zhou et al . and Balangia balangensis Chien from the Balang Formation in eastern Ghuizhou Province, south-west China. The complete protaspid to holaspid ontogeny for Duyunaspis duyunensis and incomplete meraspid to holaspid ontogenies for Changaspis elongata and Balangia balangensis are described. The relative degree of ontogenetic variation within the lineage Duyunaspis duyunensis – Balangia balangensis is analysed and indicates that Balangia may have evolved from Duyunaspis by paedomorphosis. Decrease in thoracic segment number and concomitant increase in pygidial segment number in the later genus mirrors the pattern seen in the evolution of another oryctocephalid genus, Arthricocephalus . In both cases, selection was probably targeting an increase in cephalic convexity. This resulted in the evolution of a larger pygidium due to increased elevation of the axis above the substrate. The ontogenetic development of Changaspis provides evidence supporting the view that the Oryctocarinae may be considered as paedomorphic descendants of the Oryctocephalinae.     

Growth and variation in the Silurian proetide trilobite Aulacopleura konincki and its implications for trilobite palaeobiology

Morphometric analysis of growth in Aulacopleura konincki reveals several important features: (1) morphological variability is approximately constant throughout growth, increasing slightly in later ontogeny; (2) shape is more tightly constrained than the numbers of postcephalic segments, which can be quite variable; and (3) a major ontogenetic transition occurs at glabellar lengths of about 1.7 mm. This transition divides the ontogeny into two distinct growth phases, is smooth rather than abrupt, and is expressed as changes in growth trajectories, especially in the pygidium. The transition is not strictly correlated with the number of thoracic or pygidial segments. These results suggest a re-evaluation of the concepts of meraspid and holaspid growth stages in A. konincki , using growth trajectories rather than thoracic segment number to define the stages. Developmental flexibility in holaspid segment numbers in this phylogenetically advanced trilobite suggests that environmental factors, rather than phylogenetic constraint, may explain variations in segment production patterns within some advanced Trilobita. Morphometrics, trilobites, ontogeny, variability, segmentation, Silurian, Czech Republic.     

Ontogeny of the redlichiid trilobite Eoredlichia intermediata from the Chengjiang Lagerstätte,lower Cambrian,southwest China

A detailed investigation of the morphology and ontogeny of the redlichioid trilobite Eoredlichia intermediata (Bulletin of the Geological Society of China, 3–4, 1940, 333) from the lower Cambrian Yu'anshan Member of the Heilinpu Formation, in Kunming, Yunnan Province, southwest China, is presented. The new material comprises a relatively complete ontogenetic series ranging from the early meraspid to the holaspid period, which reveals more details on morphological variation such as the appearance of bacculae in some holaspid specimens, contraction and disappearance of fixigenal spines, and macropleural spines of the first and second thoracic segments, which are all documented for the first time and can also be used as developmental markers defining ontogenetic phases. Two distinct morphotypes, possibly an expression of intraspecific variation or sexual dimorphism, are distinguished by the morphology of pleural spines of the second thoracic segment in meraspid degree 14 and holaspides. The trunk segmentation schedule of E. intermediata is also discussed and conforms to the protarthrous developmental mode. The distinction of the thoracic region into two portions can be observed during late meraspid and early holaspid periods, which might be considered as a reference for a better understanding on the relationship of tagmosis and growth segmentation among the Cambrian redlichiid trilobites.     

Moulting,ontogeny and sexual dimorphism in the Cambrian ptychopariid trilobite Strenuaeva inflata from the northern Swedish Caledonides

Abstract: Three thousand seven hundred disarticulated remains together with several articulated specimens of the Cambrian Series 2 ptychopariid trilobite Strenuaeva inflata Ahlberg and Bergström, 1978 have been collected from the Torneträsk area, northern Sweden. The material provides significant new data on the morphology, ontogeny, moulting and enrolment of the species. Two distinct morphotypes, possibly an expression of sexual dimorphism, are recognized. The morph with a pair of bulbs in the frontal area, interpreted as brood pouches, is considered to represent females. Statistical treatment of the length/width ratio in cranidia reveals isometric growth during ontogeny for both morphotypes. The transition from the meraspid to holaspid ontogenetic period has been established through recognition of the successive development of the number of thoracic segments in articulated late meraspides. Throughout its life cycle, S. inflata went through 11 meraspid degrees and at least 17 holaspid growth stages. Inferred moult ensembles and exuviae reveal the successive opening of cephalic sutures and the function of the rostral plate during exuviation. As in other ellipsocephalid trilobites in which enrolment is known, the pygidium and two or three thoracic segments of S. inflata are concealed beneath the cephalon (spiral enrolment) during complete enrolment.     

Geographic and stratigraphic change in the morphology of Triarthrus beckii (Green) (Trilobita): a test of the Plus ça change model of evolution

The Plus ça change model predicts that deepwater trilobite species such as Triarthrus should exhibit gradual phyletic evolution. A detailed stratigraphic sequence of Triarthrus beckii specimens considered together with geographically separated samples from a single time interval provide a test of the Plus ça change model. We examined geographic patterns of variation in cranidial shape based on specimens from four approximately synchronous levels within the Upper Ordovician (lower Edenian) strata of New York, Québec, Kentucky and Pennsylvania. All geographic populations differ in mean size, except for New York and Pennsylvania. Because allometry is present in both meraspid and holaspid phases of the trilobite, size effects on shape were removed by ontogenetic standardization. Cranidial shapes were then compared among the four study sites and eight stratophenetic samples from New York, obtained by subdividing our Mohawkian Composite Standard Section into 20-m-thick intervals. Goodall's F-test of pairwise comparisons of cranidial shape between eight subintervals in New York and the other three populations are all significant. Geographic variation in cranidial size and shape in T . beckii appears to display a gradient or cline-like pattern that is related to paleogeography. Although cranidial shape is not entirely static within the New York stratophenetic series, it is in all cases different from that sampled elsewhere in the region. Thus, there is no evidence of wholesale immigration and emigration among the geographic areas. Instead, the geographic gradient of T . beckii shape variation may have remained fairly stable over ca. 3 million years during the mid-Chatfieldian to early Edenian interval. This result is indicative of stasis. Consequently, the evolutionary history of T . beckii contradicts the Plus ça change model.     

Growth and development of agnostids Pentagnostus proanabarensis Fedoseev, 1999

Juvenile development of the Middle Cambrian agnostid trilobite Pentagnostus proanabarensis Fedoseev, 1999 is studied. A sequence of eight juvenile stages is defined based on changes in morphology and measurements. Three of them belong to meraspid degree 0, another three refer to meraspid degree 1, and two represent early holaspid stages. Neither the frequency distribution of the length of cephalons and pygidia nor the length-width scatter diagrams give clear clusters of molts; the number of juvenile molts can be estimated through the analysis of the posteroaxis length distribution. Thus, the measurements and morphology of some juvenile pygidia with vestiges of the pleural and postaxial furrows allow reconstruction of the number of segments during individual growth. At the initial stage of development, the pygidial axis of P. proanabarensis probably had four segments, the pygidial axis increased up to no less than six segments in adults.     

Morphology and ontogeny of the eodiscoid trilobite Sinodiscus changyangensis from the lower Cambrian of South China

Abstract: A large number of complete specimens together with numerous disarticulated sclerites of the eodiscinid trilobite Sinodiscus changyangensis Zhang in Zhou et al., 1977 have been collected from the lower Cambrian Shuijingtuo Formation in Changyang, Hubei Province, South China. An ontogenetic series is established based on the immature and mature exoskeletons including the previously unknown protaspides and meraspides, in particular. No further substages can be differentiated in the protaspid specimens herein. Changes that took place during the meraspid period include the addition of postcephalic segments and prominent pygidial larval notches in early meraspid development which became progressively less distinct and disappeared in degree 2. Two holaspid stages are recognized based on the addition of a new pygidial segment, indicating that the start of the holaspid phase preceded the onset of the epimorphic phase and accordingly, its developmental mode is attributed to the protarthrous pattern. The trunk segmentation schedule of S. changyangensis is discussed, which is similar to other primitive eodiscoid trilobites, that is, as the boundary between the thorax and pygidium migrated posteriorly, there is no change in the number of the trunk segments. The processes of liberation of the thoracic segment and segment insertion into the pygidium are separated from one another, and the two different mechanisms, somitogenesis and tagmosis, progress independently during the ontogenetic development of the postcephalic region of these primitive eodiscinids.     

Ontogeny of Agnostida

Evidence about ontogeny of the miomerid trilobite groups Eodiscina and Agnostina is summarizied and unified in terminology. There appear to be strong similarities in the juvenile development of both suborders. They both have prolonged meraspid degree 0 and 1 stages, including two to six molts. The degree 0 stage tends to shorten from six to four molts in Eodiscina, and probably from three to two in Agnostina, while degree 1 tends to lengthen whithin Eodiscina. During degree 0 and 1 moltings, none of the segments are liberated into the thorax, and one segment is added into the transitory pygidium. The liberation of thoracic segments marks the beginning of the meraspid degrees and the holaspid period. This developmental scenario contrasts with that of the classical polymerid—in the latter case, the liberation of thoracic segments is accompanied by insertion of new segments in the transitory pygidium. In the Eodiscina, during meraspid degree 2, the polymerid scheme is present.