苔藓动物的起源与系统发生研究进展—形态学和分子生物学的证据

苔藓动物是后生动物中的一个重要类群。然而,和其它主要后生动物类群相比,长期以来对它的系统学研究却相对滞后。其起源,系统发生地位以及与其它后生物门类之间、其内部各高级分类群间的谱系发生关系一直存在争议。一般认为它是介于原口动物和后口动物之间的过渡类群。但是,近年来的分子系统学研究已经证实了它的原口归属。古生物学资料表明,虽然苔藓动物的大多数类群在奥陶纪已经分化出来,但它在寒武纪却缺乏任何化石记录。另外,苔藓动物起源的时间和方式、其内部各类群间的系统发生关系特别是现生类群和化石类群之间的关系等诸多问题的解决,还有待于大量的形态学和不同的分子数据的进一步积累,并结合其地层分布等各种相关资料进行综合研究。     

谱系年代研究进展

谱系年代学是结合化石记录和分子钟方法计算"生命树"(Tree of Life)上各分歧点时间的一个新兴交叉学术领域.由于化石记录的不完整性,各类生物的起源年代和支系分化时间的确定可借助于部分化石记录和通过计算现生生物类群之间的遗传距离转换得出的相对分歧时间相结合的办法进行讨论.化石记录可代表部分生物类群起源时间的保守估计值,而分子钟方法可为那些不易保存为化石的生物类群与其姊妹群的分化时间提供依据.如果使用得当的话,两者可进行相互验证.在分子谱系年代分析中,正确使用化石校准方案是获得准确分歧时间的关键,这需要:1)正确确定化石物种在谱系树上的位置;2)正确解释化石记录所代表的时间含义(最小值、确定值、最大值及其标准差).分子钟估算分歧时间的技术在不断改进,目前常用的分子分歧时间估算法(宽松分子钟法,如贝叶斯法、补偿性似然法等)包容分子演化速率在谱系间和随时间的变化.随着谱系年代研究的不断深入,长期困扰人们的化石记录时间与分子钟计算结果悬殊的问题正在逐渐趋于和谐并得到正确诠释.文中还讨论了有关动物起源与早期分化时间以及早期陆生节肢动物的谱系年代学研究进展.我们强调,化石记录和分子钟分析可以优势互补,两者的整合无疑将提高生物演化历史时间格架的准确度和精度,以利更好地将生命演化事件置于地球系统科学及地球环境演化史之中.     

海绵特异性微生物的分子钟初测及其意义

海绵动物是最原始的后生动物,营底栖、滤食性生活,它们体内共生有丰富的微生物菌落,包括仅在海绵动物体内存在的特异性微生物。为了探讨海绵特异微生物是否与宿主存在协同演化关系,我们基于16SrRNA基因序列利用宽松分子钟方法估测了各个门类中海绵特异微生物的分歧时间,并与海绵动物的化石记录及分子谱系年代学结果相比较。结果表明:多数微生物门类中海绵特异微生物的分支分化发生在新元古代(800—1000Ma),与海绵动物的分子化石记录和当前分子钟估算结果之间存在一定程度的一致性,说明微生物与宿主海绵动物之间存在一定的协同演化关系。少数门类中海绵特异微生物分化时间过早于(如蓝细菌,2200Ma)或者过晚于(如古细菌,148Ma;Alphaproteobacteria,480Ma)新元古代,这可能是由于系统采样等因素所致,有待于进一步的分析与研究。     

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。     

寒武纪腕足动物起源:假说、问题与展望

腕足动物与软体动物和环节动物等十多个动物门类一起构成后生动物(metazoa)中分异度最大的谱系分支——冠轮动物(Lophotrochozoa)。在冠轮动物分支概念提出20周年之际,分子系统学和基因组系统学的大量研究基本证实了腕足动物、帚虫动物和外肛动物组成的触手冠动物(Lophophorata)为单系起源(monophyly),分类上属于原口动物亚界(Protostomia),从而彻底否定了上百年传统动物学教科书上腕足动物属于后口动物亚界(Deuterostomia)或原口动物亚界与后口动物亚界之间的过渡类群的传统观点。腕足动物作为寒武纪演化动物群的重要组成部分和寒武纪大爆发期间的主要动物门类代表,因其形态发育和壳体矿化等多项特点以及海量的化石记录,历经数十余年单系、多系和并系起源的争论之后,其单系起源得到了分子生物学、基因组系统学和形态学(包括化石和现生类群)研究越来越多的强力支持。长期以来,寒武纪腕足动物门曾存在帚虫状祖先起源假说、蛤氏虫(Halkieria)起源假说和托莫特壳起源假说。目前,蛤氏虫起源假说遭到了不同国际学者的质疑和否定。澄江化石库(寒武系第三阶)最新发现的化石新种——精美玉玕囊形贝(Yuganotheca elegans),因具有砂质胶结的椎管状身体,具有封闭的腕足动物状的纤毛环取食器官,具有腕足动物状的边缘刚毛、脉管循环系统、U形的消化系统和蠕虫状的肉茎附着结构等,被誉为腕足动物的"始祖鸟化石",成为联系帚虫动物门、腕足动物门和椎管状托莫特壳的化石类群。然而,因该化石缺乏成对的矿化(磷酸钙或碳酸钙)壳体,对现今广泛使用的腕足动物高级分类方案提出了新的思考和挑战。     

被子植物起源研究中几种观点的思考

对被子植物起源研究中的几种观点进行了讨论。(1)由于被子植物存在着一组共同的性状,它们不可能是从不同祖先起源的,而是有着共同的祖先。被子植物是一个单源起源的类群。现存被子植物分类系统是依据包括形态学(广义)、分子系统学、古植物学和植物地理学等的综合性状建立的,只能表示出现存类群的亲缘关系并且追溯到它们最近的祖先。人们现在还不可能建立一个包括全部已绝灭的类群和现代生存类群的谱系发生系统。因此,现存被子植物分类系统只能看作是“亲缘”系统。(2)分析了用于推测被子植物起源时间的分子、化石和地理分布证据。我们认为,要确定被子植物起源时间,植物化石是一类重要证据,但化石只能说是植物本身可保存部分和当时当地所提供的化石条件的综合反映,它们不可能就是植物类群或种的起源时间。人们还必须考虑到化石本身的演化历史。应用分子钟也是一种手段,但误差比较大。如果我们除了利用上述两种资料之外,根据植物类群的现代分布格局及其形成,把植物的演化同地球的历史和板块运动联系起来,以推断它们起源的时间,这无疑会增加其可信度。通过对56个种子植物不同演化水平的重要科属地理分布的研究结果,我们曾提出被子植物的起源时间可能要追溯到早侏罗世,甚至晚三叠世。(3)分析了基于分子证据所提出的被子植物基部类群——ANITA成员(包括无油樟科Amborellaceae、睡莲科Nymphaeaceae、八角目Illiciales、早落瓣科Trimeniaceae、木兰藤科Austrobaileyaceae)的性质,讨论了ANITA成员在现代几个被子植物分类系统中的系统位置的不同观点,评价了它们的形态学(广义)性状。指出ANITA的成员由于包含大量的祖征,是属于原始的类群。但由于它们的共有衍征很少,如花粉球形,说明它们在被子植物演化早期就分道扬镳了,沿着不同的传代线分化。因此ANITA是一个源于不同传代线的复合群。     

分子钟假说的基本原理及在古生物等学科中的应用

研究各个生物类群的起源时间是生物学、古生物学、地质学的重要研究范畴,然而由于化石记录的不完整性,仅仅通过化石无法准确地提供生物各门类的起源时间,更无法真实地反映各门类直接的演化关系,长期以来科学家们都希望能够找到新的突破口。分子钟假说可以在缺乏化石证据的条件下通过分子数据和统计学方法推算各类群间的分歧时间。文中将对分子钟假说的发展历程、基本原理、研究方法及存在的主要问题进行介绍,并就近期利用分子钟的若干研究示例进行分析,以期能对整个分子钟有个更为全面的论述。     

里白科植物的系统发育和分歧时间估计——基于叶绿体三个基因序列的证据

里白科(Gleicheniaceae)是古老的真蕨类植物,最早的化石记录可追溯到石炭纪。现存类群的属级分类和系统演化关系一直存在很大的分歧,为了进一步探讨该类群的起源演化,文中运用最大简约法和贝叶斯演绎方法对18种代表现存里白科植物全部6属(包括新测的12种)的叶绿体3个编码基因序列(atpB,rbcL和rps4)进行分析,探讨其主要分类群(属级)的系统演化关系。结果显示,里白科植物为一个单系群,由3个分支构成:里白属(Diplopterygium Nakai)和Gleichenia japonica构成一个分支;芒萁属(Dicranopteris Bernh.)和Gleichenella pec-tinata构成另一个分支;假芒萁属(Sticherus C.Presl)与单种属Stromatopteris Mettenius及Gleichenia dicarpa构成第三个分支。用宽松分子钟方法推测里白科主要类群的起源时间为:现代里白科植物起源于早白垩世(111—140Ma),其主要分支类群随后发生多样性分化,里白属和芒萁属的快速辐射演化均发生在古近纪(40—64Ma,36—50Ma)。起源时间的估算结果暗示化石种三叠里白Diplopterygium triassica不应归入现代里白属,其归属需要重新考虑。     

奥陶纪苔藓动物的多样性演变——兼论苔藓动物的起源

苔藓动物是一类多为海生、滤食性的群体生物。奥陶纪是苔藓动物发生、演化辐射和灭绝的重要时期,也是苔虫礁形成的最早时期。已知最老的化石苔藓动物发现于中国特马豆克晚期。构成苔藓动物基本分类框架的狭唇纲(包括变口目、隐口目、泡孔目和管孔目)和宽唇纲(包括窗孔目和栉口目)也都是在奥陶纪时期逐步形成的,其中,变口目出现于特马豆克期Tr2时间段,在弗洛期和大坪期,多样性较低,但从达瑞威尔期开始,经桑比期至凯迪期,多样性不断增高,并出现辐射。隐口目(特别是"双叶类隐口目苔虫")也经历了与变口目相类似的发展过程,但它首次出现的时间要相对略迟于变口目。这两个目在整个奥陶纪苔藓动物群中一直占据主导地位。泡孔目、管孔目和窗孔目,先后首次出现在弗洛期Fl2时间段、大坪期Dp1和Dp2时间段,但它们在整个奥陶纪期间一直处于低多样性态势。至于栉口目,它首次出现的时间可能更迟,在凯迪期Ka4时间段,犹如昙花一现。苔藓动物的演化在接近奥陶纪末时呈两幕式灭绝,一次发生在凯迪期Ka2时间段(可能相当于塔凯和安斯蒂的"拉夫塞伊灭绝"),另一次发生在赫南特期Hi2时间段(可能相当于塔凯和安斯蒂的"赫南特灭绝")。分子生物学和形态学证据表明,苔藓动物属原口动物,而不是以前长期认为的后口动物,或介于原口动物和后口动物之间的过渡类型;而且,苔藓动物与腕足动物、帚形动物之间没有直接的亲缘关系。苔藓动物可能起源于一种叫原内肛动物的生物,它们的目一级分类单元之间的系统发育关系目前尚未形成共识,本文绘制的谱系图还有待于化石记录的不断补充和分子生物学研究的逐步介入以使其日趋完善。     

介形类系统分类与起源演化的形态、分子和化石证据

介形类(Ostracoda)因其丰富的化石记录和广布的海陆现生代表类群,而被认为是进化生物学中研究生物多样性产生机制和演变历程的颇具潜力的重要模式生物。介形类在甲壳亚门中的谱系发生位置、起源及其内部各类群间的系统关系还存在诸多争议。基于其体制构造的形态学特征,介形类被归入甲壳亚门下的颚足纲(Maxillopoda),但来自18S rDNA序列数据分析却显示Maxillopoda不是单系群。基于化石记录和壳体形态特征,高肌虫(Bradoriida)长期以来被认为是介形类的一个祖先类群,但保存有软躯体的早寒武世化石的研究表明,Bradoriida不是介形类甚至可能也不属于甲壳类。不同的研究者所强调的壳体和肢体形态特征各异,导致介形类最大的现生类群速足目(Podocopida)的四个超科之间的关系也存在诸多推测。壳体和肢体特征在系统演化意义上的不兼容,需要分子生物学等证据的介入。分子、形态和化石证据的积累及各种信息整合是系统演化研究的必然趋势。     

18S rRNA suggests that Entoprocta are protostomes,unrelated to Ectoprocta

The Ento- and Ectoprocta are sometimes placed together in the Bryozoa, which have variously been regarded as proto- or deuterostomes. However, Entoprocta have also been allied to the pseudocoelomates, while Ectoprocta are often united with the Brachiopoda and Phoronida in the (super)phylum Lophophorata. Hence, the phylogenetic relationships of these taxa are still much debated. We determined complete 18S rRNA sequences of two entoprocts, an ectoproct, an inarticulate brachiopod, a phoronid, two annelids, and a platyhelminth. Phylogenetic analyses of these data show that (1) entoprocts and lophophorates have spiralian, protostomous affinities, (2) Ento- and Ectoprocta are not sister taxa, (3) phoronids and brachiopods form a monophyletic clade, and (4) neither Ectoprocta or Annelida appear to be monophyletic. Both deuterostomous and pseudocoelomate features may have arisen at least two times in evolutionary history. These results advocate a Spiralia-Radialia-based classification rather than one based on the Protostomia-Deuterostomia concept. Correspondence to: J.R. Garey     

Complete mitochondrial genome of Membranipora grandicella (Bryozoa: Cheilostomatida) determined with next-generation sequencing: The first representative of the suborder Malacostegina

Next-generation sequencing (NGS) has proven a valuable platform for fast and easy obtaining of large numbers of sequences at relatively low cost. In this study we use shot-gun sequencing method on Illumina HiSeq 2000, to obtain enough sequences for the assembly of the bryozoan Membranipora grandicella (Bryozoa: Cheilostomatida) mitochondrial genome, which is the first representative of the suborder Malacostegina. The complete mitochondrial genome is 15,861 bp in length, which is relatively larger than other studied bryozoans. The mitochondrial genome contains 13 protein-coding genes, 2 ribosomal RNAs and 20 transfer RNAs. To investigate the phylogenetic position and the inner relationships of the phylum Bryozoa, phylogenetic trees were constructed with amino acid sequences of 11 PCGs from 30 metazoans. Two superclades of protostomes, namely Lophotrochozoa and Ecdysozoa, are recovered as monophyletic with strong support in both ML and Bayesian analyses. Somewhat to surprise, Bryozoa appears as the sister group of Chaetognatha with moderate or high support. The relationship among five bryozoans is Tubulipora flabellaris + (M. grandicella + (Flustrellidra hispida + (Bugula neritina + Watersipora subtorquata))), which supports for the view that Cheilostomatida is not a natural, monophyletic clade. NGS proved to be a quick and easy method for sequencing a complete mitochondrial genome.     

Multigene analysis of lophophorate and chaetognath phylogenetic relationships

Maximum likelihood and Bayesian inference analyses of seven concatenated fragments of nuclear-encoded housekeeping genes indicate that Lophotrochozoa is monophyletic, i.e., the lophophorate groups Bryozoa, Brachiopoda and Phoronida are more closely related to molluscs and annelids than to Deuterostomia or Ecdysozoa. Lophophorates themselves, however, form a polyphyletic assemblage. The hypotheses that they are monophyletic and more closely allied to Deuterostomia than to Protostomia can be ruled out with both the approximately unbiased test and the expected likelihood weights test. The existence of Phoronozoa, a putative clade including Brachiopoda and Phoronida, has also been rejected. According to our analyses, phoronids instead share a more recent common ancestor with bryozoans than with brachiopods. Platyhelminthes is the sister group of Lophotrochozoa. Together these two constitute Spiralia. Although Chaetognatha appears as the sister group of Priapulida within Ecdysozoa in our analyses, alternative hypothesis concerning chaetognath relationships could not be rejected.     

Wall structure and evolution in cyclostomate Bryozoa

The Stenolaemata comprise both basically single-walled forms (Cyclostomata) and doublewalled forms (Trepostomata, Cystoporata and Cryptostomata) from their first appearance in the geological record. At the end of the Palaeozoic the main groups of apparently double-walled stenolaemates died out, and only the single-walled cyclostomates survived. During the Mesozoic, evolution within the Stenolaemata was apparently repeated by the further development of double-walled forms such as cerioporids, lichenoporids and cancelloids, from single-walled ancestors. These double-walled groups are all remarkable homeomorphs of the major Palaeozoic groups of Bryozoa. A monophyletic origin of the post-Palaeozoic Cyclostomata from Palaeozoic single-walled forms is thus suggested.     

Phylogenetic relationships within the Mysidae (Crustacea, Peracarida, Mysida) based on nuclear 18S ribosomal RNA sequences

Species of the order Mysida (Crustacea, Peracarida) are shrimp-like animals that occur in vast numbers in coastal regions of the world. The order Mysida comprises 1,053 species and 165 genera. The present study covers 25 species of the well-defined Mysidae, the most speciose family within the order Mysida. 18S rRNA sequence analysis confirms that the subfamily Siriellinae is monophyletic. On the other hand the subfamily Gastrosaccinae is paraphyletic and the subfamily Mysinae, represented in this study by the tribes Mysini and Leptomysini, consistently resolves into three independent clades, and hence is clearly not monophyletic. The tribe Mysini is not monophyletic either, and forms two clades of which one appears to be closely related to the Leptomysini. Our results are concordant with a number of morphological differences urging a taxonomic revision of the Mysidae.     

Phylogeny of the Metazoa Based on Morphological and 18S Ribosomal DNA Evidence

Cladistic analysis of traditional (i.e. morphological, developmental, ultrastructural) and molecular (18S rDNA) data sets (276+501 informative characters) provides a hypothesis about relationships of all meta-zoan higher taxa. Monophyly of Metazoa, Epith-eliozoa (= -03non-Porifera), Triploblastica, Mesozoa, Eutriploblastica (=Rhabditophora+Catenulida+“higher triploblasts”=Neotriploblastica, including Xeno- turbellida and Gnathostomulida), Rhabditophora, Syndermata (=“Rotifera”+Acanthocephala), Neotrichozoa (=Gastrotricha+Gnathostomulida), Nematozoa (=Nematoda+Nematomorpha), Panarthropoda (=Onychophora+Tardigrada+ Arthropoda), Cephalorhyncha, Deuterostomia, Ambulacralia (=Hemichordata+Echinodermata), Chordata, Phoronozoa (=Phoronida+“Brachiopoda”), Bryozoa, Trochozoa (=Eutrochozoa+Entoprocta+ Cycliophora), Eutrochozoa, and Chaetifera (=Annelida+ Pogonophora+Echiura) is strongly supported. Cnidaria (including Myxozoa), Ecdysozoa (=Cepha- lorhyncha + Nematozoa + Chaetognatha + Panarthropoda), Eucoelomata (=Bryozoa+Phoronozoa+Deuterostomia+Trochozoa, possibly including also Xenoturbellida), and Deuterostomia+Phoronozoa probably are monophyletic. Most traditional “phyla” are monophyletic, except for Porifera, Cnidaria (excluding Myxozoa), Platyhelminthes, Brachiopoda, and Rotifera. Three “hot” regions of the tree remain quite unresolved: basal Epitheliozoa, basal Triploblastica, and basal Neotriploblastica. A new phylogenetic classification of the Metazoa including 35 formally recognized phyla (Silicispongea, Calcispongea, Placozoa, Cnidaria, Ctenophora, Acoela, Nemertodermatida, Orthonecta, Rhombozoa, Rhabditophora, Catenulida, Syndermata, Gnathostomulida, Gastrotricha, Cephalorhyncha, Chaetognatha, Nematoda, Nematomorpha, Onychophora, Tardigrada, Arthropoda, Echinodermata, Hemichordata, Chordata, Phoronozoa, Bryozoa s. str., Xenoturbellida, Entoprocta, Cycliophora, Nemertea, Mollusca, Sipuncula, Echiura, Pogonophora, and Annelida) and few i ncertae sedis g roups (e.g. Myzostomida and Lobatocerebromorpha) is proposed.     

A molecular reassessment of the Leptomyxid amoebae

Leptomyxid amoebae encompass a diverse assemblage of amoeboid protists that have been implicated as encephalitis-causing agents. This characteristic is attributed to recent studies identifying new members of the Leptomyxidae, in particular, Balamuthia mandrillaris, that cause the disease. Their morphologies range from limax to plasmodial, as well as reticulated and polyaxial. Although systematic studies have identified B. mandrillaris as a new member of the Leptomyxidae, its precise placement within the leptomyxids is uncertain. To further assess the taxonomic placement of Balamuthia among the leptomyxid amoebae and to determine whether the members of the Leptomyxida form a monophyletic assemblage, we have sequenced 16S-like rRNA genes from representatives of three leptomyxid families. Our phylogenetic analyses revealed that current members of the order Leptomyxida do not constitute a monophyletic assemblage. Our analyses clearly show that Gephyramoeba, as well as Balamuthia do not belong in the order Leptomyxida. We highlight where molecular data give differing insights than taxonomic schemes based on traditional characters.     

凤蝶亚科(凤蝶科,鳞翅目)16S rRNA基因的分子系统发生分析

对15种凤蝶亚科蝶类线粒体16S rRNA基因部分序列进行了测定,并结合GenBank中其它相关类群的序列,采用邻接法(NJ)、最大简约法(MP)、最大似然法(ML)和贝叶斯法构建凤蝶亚科的分子系统树,探讨该亚科各类群间的系统发生关系.结果表明,燕凤蝶族构成凤蝶亚科蝶类系统树基部的一个独立分支;燕凤蝶族和裳凤蝶族为单系发生,且裳凤蝶族聚在凤蝶族内部;喙凤蝶族的单系性尚不能确定.综合分子系统学、形态学及寄主植物等相关证据,推测斑凤蝶类为凤蝶族中早期分化的一支;较之裳凤蝶类,斑凤蝶类可能更早从二者最近的共同祖先中分化出来.     

Lophotrochozoan phylogeny assessed with LSU and SSU data: evidence of lophophorate polyphyly

Of the three major bilaterian clades, Lophotrochozoa has the greatest diversity and disparity of body forms and is the least understood in terms of phylogenetic history. Within this clade, small nuclear ribosomal subunit (SSU or 18S) studies have failed to provide resolution and other molecular markers have insufficient taxon sampling. To examine relationships within Lophotrochozoa, we collected and complied complete SSU data and nearly complete (>90%) large nuclear ribosomal subunit (LSU or 28S) data totaling approximately 5kb per taxon, for 36 lophotrochozoans. Results of LSU and combined SSU+LSU likelihood analyses provide topologies more consistent with morphological data than analyses of SSU data alone. Namely, most phyla recognized on morphological grounds are recovered as monophyletic entities when the LSU data is considered (contra SSU data alone). These new data show with significant support that "Lophophorata" (traditionally recognized to include Brachiopoda, Phoronida, and Bryozoa) is not a monophyletic entity. Further, the data suggest that Platyzoa is real and may be derived within lophotrochozans rather than a basal or sister taxon. The recently discovered Cycliophora are allied to entoprocts, consistent with their initial placement based on morphology. Additional evidence for Syndermata (i.e., Rotifera+Acanthocephala) is also found. Although relationships among groups with trochophore-like larvae could not be resolved and nodal support values are generally low, the addition of LSU data is a considerable advance in our understanding of lophotrochozoan phylogeny from the molecular perspective.     

Les Bryozoaires du Crétacé inférieur provençal. Biostratigraphie et paléoécologie

Lower Cretaceous Bryozoa are still badly known. Their geographical and stratigraphical distribution is remained very narrow. Thus, no one Barremian Fauna was discovered still this day, if we except some very rare encrusting Bryozoa. Study of the Bryozoa from Provence allowed us to make connexion between the Neocomian and Aptian Fauna. Moreover, owing to the stratigraphical, paleoecological and sedimentological studies of the Bryozoans beds made elsewhere by J.-P. Masse, advance to the Lower Cretaceous Bryozoa Paleoecology was attempted.