Halwaxiids系统进化研究进展

Halwaxiids是一类体表覆有骨质鳞片的寒武纪后生动物,它包含了在早期后生动物进化中占据关键位置的两个化石动物类群Halkieriids和Wiwaxids.但自1995年以来包含Halkieria和Wiwaxia在内的Halwaxiids进化枝在不断被修正,而近年来,随着新化石和新证据的出现,围绕Halkieria...     

寒武纪大爆发——来自贵州的化石证据*

寒武纪展示了生物演化和生态创新最为关键的一段历史, 在此期间发生了后生动物快速的辐射性演化事件, 被称为“寒武纪大爆发”。近四十年来, 基于寒武纪特异埋藏生物群的大量研究为解密寒武纪大爆发具体过程、主要动物类群起源与生态演化作出了重要贡献。贵州素有古生物王国之称, 在寒武系地层中不仅保存了大量解剖学细节精美的化石资源, 也在多个地区产出时间连续的生物组合演化序列, 在探讨动物起源与演化、全球地层对比及群落古生态学等方面具有极其重要的科研价值。近年来, 以小壳动物群、牛蹄塘生物群、杷榔生物群、剑河生物群、凯里生物群等多个生物群在贵州的发现提供了早期后生生物的新信息, 加密了中国乃至全球早期后生生物特异埋藏化石群的演化链, 为全面揭示寒武纪生物群落面貌、早期多门类后生动物的辐射演化和海洋生物群落演替提供了独特的意义, 最终为深入解读寒武纪大爆发的过程与发生机制提供重要实证。本文简要总结了贵州地区在该领域的主要学术贡献, 结合全球研究进展, 对目前存在的问题和未来研究方向提出展望。     

陕西宁强寒武系纽芬兰统幸运阶宽川铺组中的Olivooides mirabilis化石新类型*

陕南寒武系纽芬兰统幸运阶宽川铺组中大量高精度形态结构特征的小壳化石在磷酸盐化作用下得以保存, 该地也成为了研究“寒武纪生命大爆发事件”的重要化石宝库。Olivooides (橄榄蛋属)是第一小壳化石组合带 Anabarites trisulcatus—Protohertzina anabarica中一类特征鲜明、易于识别的刺胞类动物化石。过去40多年来报道的绝大部分Olivooides (橄榄蛋属)化石被厘定归并为2个种: O. multisulcatus (多沟橄榄蛋)和O. mirabilis (奇异橄榄蛋)。该属化石的形态分异度以及生长发育模式还有待进一步研究。本文描述了陕南宁强圆宝山剖面寒武系幸运阶宽川铺组中以次生磷酸盐化方式保存的Olivooides化石。本研究发现了一种新类型的O. mirabilis化石, 它与传统类型O. mirabilis的主要区别为: 布满星状棘突的胚胎期组织部分只发育一圈横向环带、胚胎后期组织部分发育五列纵向的“V”型褶皱、口部发育两组不同形态特征和不同褶皱程度的口叶。     

新疆寒武纪早期单壳类软体动物化石分类学与生物地层学

作者系统描述了新疆阿克苏-乌什地区下寒武统玉尔吐斯组中上部单壳类软体动物化石10属10种,其中包括3个新种、3个老种和4个未定种,它们是Shabaktiella multiformis sp.nov.,Ilsanella acuta sp.nov.,Xianfengella yuertusiensis sp.nov.,Parcaconus xinjiangensis,Protostenotheca xinjiangensis,Aldanella attlebo-rensis,Obtusoconus sp.,Yochelcionella sp.,Bemella sp.和Mellopegma sp..上述10个属种基本上代表了玉尔吐斯组单壳类软体动物的面貌特征.文中介绍了本研究区10个属和属级以上分类系统在国际学术界的意见分歧后,重申了以壳的对称性和有无肌痕确定纲级界线的最佳分类原则,提出了应用壳型划分目级分类单元和口缘形状、壳顶与口缘的相对位置划分科级分类单元的可行性和有效性,但是不能接受把所有单板状软体动物化石通常被归入单板纲的做法,因为寒武纪早期一些单板状软体动物化石不一定符合单板纲的真实含义.文中还回顾了近二十年来建立的始单板纲(Eomonoplacophora)(Missarzhevsky,1989),太阳女神螺纲(Helcionelloida),背壳肌纲(Tergomya)(Peel,1991a,b)和似腹足纲(Paragastropoda)(Linsley & Kier,1984)等纲级的新概念.还有一些早期软体动物专家将许多单板状(包括帽状和螺旋状)化石归入单板纲(Runnegar et al.,1976,1985),而另有一些中青年软体动物专家继承传统理念,将它们归入了腹足纲(Parkhaev in.Alexander et al.,2001).钱逸和本格森将早期单壳类软体动物化石分成了五大形态类别,未确定科级以上分类单元名称(Qian & Bengtson,1989).总之,目前纲级分类单元界线不清,目级以下分类单元十分混乱,在没有全面清理早期单壳类软体动物百余个属和属级以上分类单元之前,是难以统一本文研究的早期单壳类软体动物10个属和属级以上分类系统.我们认为在确定属级以上分类系统及其与之密切相关的演化谱系关系时,不是利用理论前提,而是在不间断的剖面上对单壳类软体动物化石进行逐层采集并对其构造要素的详细研究,才能使得出的结论和提出的新分类系统发生错误的几率最小.文中还归纳和总结了本研究区玉尔吐斯组中上部单壳类软体动物群面貌的六大特点,其中二点最重要:1)该动物群与梅树村期微软体动物群的面貌有明显的差别,它缺失了梅树村期微软体动物群中最原始、最特征、最丰富的类群,如笠帽状的马哈螺类化石Maikhanella,Purella等和螺旋状的始旋螺类化石Archaeospira等.但是该动物群面貌却与邻区的哈萨克斯坦Atdabanian期的微软体动物和我国峡区西蒿坪动物群面貌接近,出现了许多相同或相似的属种,如Shabaktiella,Mellopegma,Aldanella,Yochelcionella等.2)该动物群共生有全球分布的相当于筇竹寺期的标准化石,如原牙形类Gapparodus,Amphigeisina,Hagionella等,有口唇并有背腹分异和复杂口盖的软舌螺类Microconus,Pachytheca等,具有肉茎孔和铰合面的有铰腕足类和像Obolus那样的原始无铰腕足类,有各种形态类型的金臂虫Dabashanella,Liangshanella等,还有可疑的三叶虫颊刺等.上述信息足以说明玉尔吐斯组中上部地层时代应属筇竹寺期而非梅树村期,从而解决了长期以来有关玉尔吐斯组时代归属的争议. 玉尔吐斯组单壳类软体动物群的研究,再次证实了寒武纪生命大爆发期间,早期单壳类软体动物与小壳动物群一起经历了三次大发展和三次大绝灭事件.这在早期单壳类软体动物化石分类学、生物地层学和早期演化史上均有较高的科学价值.     

华南寒武纪奥斯坦型化石研究进展

传统的奥斯坦型(Orsten-type)化石是指三维磷酸盐化的、以软躯体保存为主的、微型蜕皮动物化石。它们代表着早寒武世到早奥陶世浅海小型底栖生物群中的蜕皮动物,是其它类型的保存方式(如布尔吉斯页岩型)难以保存的。奥斯坦型化石在西方有近半个世纪的研究历史,但是在中国却起步较晚,直到2005年才首次报道。中国的奥斯坦型化石在四个剖面的相关层位有产出,即湘西王村剖面上寒武统排碧阶、滇北硝滩剖面下寒武统第三阶、陕南张家沟剖面和川北新立剖面的下寒武统幸运阶。报道的化石类群包括丰富的甲壳动物Phosphatocopida,最古老的真甲壳动物,最古老的环神经动物,动吻动物门第一个化石属种,等等。虽然研究历史短,中国的奥斯坦型化石在揭示甲壳动物、环神经动物及蜕皮动物的起源和早期演化方面展现了重要的价值。     

论寒武纪三叶虫Prodamesella属*

根据贵州东部万山镇之南羊尾舟至寄马冲剖面中晚寒武世花桥组和车夫组所产丰富的新材料,将Ｐｒｏｄａｍｅｓｅｌｌａ分成３个亚属：Ｐｒｏｄａｍｅｓｅｌｌａ（Ｐｒｏｄａｍｅｓｅｌｌａ）Ｃｈａｎｇ１９５７,Ｐｒｏｄａｍｅｓｅｌｌａ（Ｍｅｔａｐｒｏｄａｍｅｓｅｌｌａ）ｓｕｂｇｅｎ．ｎｏｖ．,Ｐｒｏｄａｍｅｓｅｌｌａ（Ｎｅｏｐｒｏｄａｍｅｓｅｌｌａ）ｓｕｂｇｅｎ．ｎｏｖ．;鉴于头盖和尾部的特征,将Ｐｒｏｄａｍｅｓ     

贵州中寒武世凯里生物群中的蠕形动物化石*

描述了凯里生物群中的蠕形动物Ottoia ,Maotianshania ,Palaeoscolex ,Circocosmia?及Selkirkia。这些软躯体的蠕虫化石在凯里生物群中都是首次发现。其中Ottoia也发现于布尔吉斯页岩生物群 ,Maotianshania ,Circocosmia ?则见于澄江生物群 ,而Palaeoscolex则从澄江生物群至布尔吉斯页岩生物群中都有保存 ,这是凯里生物群处于承前启后位置的又一证据。蠕动动物的发现 ,增加了凯里生物群软躯体化石内容 ,反映了凯里生物群是典型的布尔吉斯页岩生物群。     

化石数据在生物分类学中的作用

从生物分类学的研究历史来探讨化石在分类学中地位的变化,以及这种变化和思想观念更新的关系。用脊椎动物高级类群关系的变化作例子,说明化石类群在动物系统发育研究中的作用。     

跳虫系统进化的研究进展

跳虫是弹尾纲（Collembola）的俗称,在所有六足动物中化石年代最早,因此跳虫是六足动物起源及进化研究中非常重要的类群。跳虫的起源、分类地位和系统关系等问题,对于阐明六足动物甚至节肢动物各大类群的系统关系非常关键,日益成为相关学者关注和争论的焦点。本文就跳虫形态学和分子系统学方面的研究工作进行了综述。     

寒武纪化石胚胎的解剖学、亲缘关系以及发育序列

Bengtson和Yue首次确定Olivooides和Markuelia为化石胚胎,建立了Olivooides的胚胎和胚后发育序列,并且提出Olivooides的亲缘关系是刺细胞类(Bengtson and Yue,1997;Yue and Bengtson,1999).在过去的10年中,许多论述寒武纪化石胚胎的文章问世,极大地提高了人们的认识.其中,Steiner等识别出Pseudooides为化石胚胎,并且推想了Pseudooides的发育序列(Steiner et al.,2004 a,b).基于在中国湖南西部中、上寒武统发现的许多精美保存的标本,对Mat"kuelia进行了解剖学、亲缘关系和支序分析研究,限定Markuelia的亲缘关系为Scalidophora(动吻动物门、兜甲动物门和曳鳃动物门的统称)的干群.尝试性地建立了Markuelia的发育序列,特别是预孵化阶段的发育序列,即从吻刺形成的最早时期直至即将孵化的最后时期的发育序列.因为最近发现了保存完美的Olivooides预孵化阶段、孵化阶段以及未成年个体阶段(Olivooides和Punctatus之间的过渡类型)的标本,重新建立了Olivooides的胚胎和胚后发育序列.尽管Olivooides的亲缘关系仍然有争议,但多数作者支持其亲缘关系为刺细胞类.然而,迄今所描述的大多数寒武纪化石胚胎的亲缘关系,特别是谜一般的化石胚胎-Pseudooides的亲缘关系仍然不得而知.由于Markuelia孵化后的幼虫、未成年个体或成年个体的标本还未发现,其胚后发育序列则无从谈起,令人信服的原肠胚阶段的化石胚胎也未见报道.今后,可靠的原肠胚阶段的化石的发现很可能要借助于同步加速器辐射X射线层析显微技术.总之,寒武纪化石胚胎的研究还有很多悬而未决的问题.     

Oikozetetes from the early Cambrian of South Australia: implications for halkieriid affinities and functional morphology

Shells of Oikozetetes and isolated halkieriid sclerites from a section of the lower Cambrian Mernmerna Formation in the Flinders Ranges, South Australia, are tentatively considered as being derived from the same scleritome. Details of shell morphology and the possible combination of biomineralized shell and sclerites suggest that Oikozetetes , if interpreted correctly, is closely related to Halkieria . A new interpretation of Oikozetetes shell morphology, in addition to the first report of paired muscle scars on the interior surface, sheds new light on the possible functional morphology of halkieriid shells and the means of attaching the shell to the body. The occurrence of Oikozetetes in South Australia extends its biostratigraphic range to the lower Cambrian and biogeographic range to East Gondwana.     

A comparative study of Lower Cambrian Halkieria and Middle Cambrian Wiwaxia

Two Cambrian lepidote metazoans known from different respective types of preservation have been compared in order to elucidate their biology and affinities. The widely distributed Lower Cambrian Halkieria is represented by isolated hollow sclerites, probably of originally calcareous composition. The Middle Cambrian Wiwaxia is known from the Burgess Shale as isolated sclerites (scales and spines) and as more or less complete individuals. Although Halkieria sclerites were mineralized and those of Wiwaxia were probably not, there are fundamental structural and morphological similarities between the two. Both bad an imbricating scaly and spiny armour consisting of hollow sclerites with a longitudinally fibrous structure. The sclerites did not grow, but were probably moulted during the course of ontogenetic growth. Halkieria and Wiwaxia are regarded as closely related. Both are referred to the Order Sachitida He 1980. The sclerite armour of Halkieria is reconstructed on the template provided by Wiwaxia. The interpretation of sachitid sclerites as protective armour is an alternative to the interpretation by Jell (1981, Alcheringa 5 )that sachitid sclerites were respiratory organs in an animal of probable annelid affinities. Sachitids are interpreted as sluggish, benthic deposit feeders that do not belong to any recognized phylum.     

An ab initio study of the guanidinium groups in saxitoxin

Quantum chemical (Hartree-Fock) calculations were performed on neutral and protonated saxitoxin in order to obtain optimum geometries, rotational energy barriers for the guanidinium ions and proton affinities. For comparison purposes, as model compounds, guanidinium systems in five and six membered rings were also investigated. In addition, DFT (B3LYP) calculations with the 6-31G** basis set were performed and the sodium affinities of the guanidinium groups in saxitoxin were obtained. It was concluded that the inhibition of the sodium channels by the saxitoxin is due to the interaction of the guanidinium group with carboxylate groups from the wall of the channel and not to the binding of the sodium ions. Figure Calculated structure of Compound 1, neutral saxitoxin. a Calculated structure of Compound 1a, saxitoxin protonated on the guanidine of the five-membered ring. b Calculated structure of Compound 1b, saxitoxin protonated on the guanidine of the six-membered ring     

梧桐科翅子树属的亲缘关系

翅子树属传统上均作为梧桐科山芝麻族的成员,但也有少数人将它归到Dombeyeae族中。本文根据对翅子树属的外部形态及花粉形态特征的研究,并结合其解剖、染色体和胚胎发育的资料,对翅子树属的亲缘关系进行了分析。翅子树属与山芝麻族在外部形态上比较接近,但在解剖、花粉形态和染色体基数等特征上则差异显著;与Dombeyeae族在花粉形态上一致,但在外部形态(花结构)、染色体基数和瓦形细胞等特征方面则明显不同,反映了翅子树属在这两个族之间的过渡状态,不宜作为任何一族的成员,应该作为一个独立的族存在,其在梧桐科中的位置在Dombeyeae附近。     

Amphipod crustaceans from anchihaline cave waters of the Galapagos Islands

Three species of blind Amphipoda are recorded from anchihaline cave waters in the Galapagos Islands. One of these, Galapsiellus leleuporum (Monod, 1970) was previously know from the islands; the male is described for the first time. The other two belong to families with predominantly (though not exclusively) deep-sea members: Valettietta cavernicola sp. nov. (family Lysianassidae; and Antronicippe serrata gen. et sp. nov. (family Pardaliscidae). The genus Valettietta was not previously recorded from caves; it contained two abyssal species in the Atlantic, while a third species was recorded from the Pacific in a vertical haul between 0 and 5300 m. Antronicippe is closely related to Spelaeonicippe , a genus with two species known from anchihaline caves in the Canary Islands and the West Indies.     

Amphipod crustaceans from anchihaline cave waters of the Galapagos Islands

Three species of blind Amphipoda are recorded from anchihaline cave waters in the Galapagos Islands. One of these, Galapsiellus leleuporum (Monod, 1970) was previously know from the islands; the male is described for the first time. The other two belong to families with predominantly (though not exclusively) deep-sea members: Valettietta cavernicola sp. nov. (family Lysianassidae; and Antronicippe serrata gen. et sp. nov. (family Pardaliscidae). The genus Valettietta was not previously recorded from caves; it contained two abyssal species in the Atlantic, while a third species was recorded from the Pacific in a vertical haul between 0 and 5300 m. Antronicippe is closely related to Spelaeonicippe, a genus with two species known from anchihaline caves in the Canary Islands and the West Indies.