早寒武世马哈螺类的骨骼化特征、分类和演化意义

马哈螺类（maikhanellids)是已知最古老的单板类,以往缺乏系统研究,并在分类上争议较大,文中以滇东早寒武世梅树村阶微小骨骼化石的丰富材料为依据,详细阐述该类群的形态特征和超微结构,探讨其亲缘关系和演化趋势,研究表明,马哈螺类由6个属组成,包括Maikhanella,Ramenta,Ramentoides gen.nov.,Mediata gen.nov.,Yunnanopleure和Purella。各属之间壳形变化较大,但裸露的壳顶和普遍发育的鳞片状或条状突起表明它们在明显的亲缘关系,并显示两个演化方向,即Maikhanella Ramentoides gen.nov.Ramenta和Maikhanella Mediata gen.nov.Yunanopleura-Purella。马哈螺类分布于梅树村期早,中期,Maikhanella是最原始的马哈螺,最先出现在梅树村阶小歪头山段,也是中谊村段下磷矿层唯一的马哈螺,而在该段上磷矿层马哈螺类发生了明显的属种分异,在大少段所有的马哈螺类突然消失,马哈螺类的壳体曾被描述为：骨针状的外骨骼”,“骨片状外骼”和“包裹在中间基质中的骨针”,但当前研究表明,以Maikhanella pristinis和Ramenta cambrina为代表的马哈螺类的内壳层具有早期单板类中较常见的水平交错纤状结构,指示了马哈螺类具有致密成层的壳壁,文中新建2亚科,2属和5种,即Maikhanellinae subfamily nov.,Purellinae subfamily nov.,Maikhanella Perelegans sp.nov.,Ramenta superata sp.nov.,Ramentoides latispinus gen.et sp.nov.,Mediata kunyangensis gen.et sp.nov.,Yunnanopleura longidens sp.nov。     

Deep molluscan phylogeny: synthesis of palaeontological and neontological data

The position of the earliest-derived living molluscs, the Polyplacophora (chitons) and shell-less vermiform Aplacophora, remains highly contentious despite many morphological, developmental and molecular studies of extant organisms. These two groups are thought to represent either a basal molluscan grade or a clade (Aculifera) sister to the 'higher' molluscs (Conchifera). These incompatible hypotheses result in very different predictions about the earliest molluscs. A new cladistic analysis incorporating both Palaeozoic and extant molluscs is presented here. Our results support the monophyly of Aculifera and suggest that extant aplacophorans and polyplacophorans both derive from a disparate group of multivalved molluscs in two major clades. Reanalysis of the critical Ordovician taxon 'Helminthochiton' thraivensis shows that this animal lacks a true foot despite bearing polyplacophoran-like valves. Its position within our phylogenetic reconstruction indicates that many fossil 'polyplacophorans' in the order Palaeoloricata are likely to represent footless stem-group aplacophorans. 'H.' thraivensis and similar forms such as Acaenoplax may be morphological stepping stones between chitons and the shell-less aplacophorans. Our results imply that crown-group molluscan synapomorphies include serial repetition, the presence of a foot, a mineralized scleritome and a creeping rather than worm-like mode of life.     

Oelandiella, the earliest Cambrian helcionelloid mollusc from Siberia

The helcionelloid molluscs Oelandiella korobkovi O. sibirica Vostokova are redescribed on the basis of type material from the lowest Cambrian of northern Siberia. Oelandiella is reinstated as a recognizable genus separated from Latouchella Cobbold, of which it has been considered generally to be a junior synonym, by differences in the prominent comarginal plication. The bilaterally symmetrical shells of both of these genera are readily delimited from Oelandia Westergård, originally described from the Middle Cambrian of Sweden, which has a characteristic asymmetrical alternation of plicae.     

湖北郧西范家坪早石炭世四射珊瑚

本文描述了贵阳西北郊探矿厂对面山坡上发现的早二叠世晚期茅口组双切尾虫亚科三叶虫的1新属——棘菲利普虫属(Acanthophillipsia),计4新种:Acanthophillipsia guiyangensis, A. abrota, A. abnormis和A.granurosa,丰富了我国二叠纪三叶虫动物群的资料,对研究二叠纪三叶虫的分类、演化和古生物地理分区都具有一定的意义。     

Facies and fauna of the Pennsylvanian Buckhorn Asphalt Quarry deposit: a review and new data on an important Palaeozoic fossil <Emphasis Type="Italic">Lagerstätte</Emphasis> with aragonite preservation

The Pennsylvanian Buckhorn Asphalt Quarry contains the best-preserved Palaeozoic mollusc fauna in the world. Early impregnation of mixed siliciclastic–carbonate rocks (mudstones, pack to grainstones, shell beds, and conglomerates) with hydrocarbons prevented aragonite destruction (“Impregnation Fossil Lagerstätte”). The exceptional preservation comprises shell microstructures, microornaments and early ontogenetic shells. Most gastropods had planktotrophic larval development indicating a high primary production although the remains of phytoplankton are very rare in this and other Late Palaeozoic deposits. Deposition occurred close to a shallow-water coastal area. Mass flow processes (density currents) triggered by storms were involved in the transport mechanisms of some units. Shells of benthic molluscs yield the most diverse known Palaeozoic microboring assemblage, indicating at least partly euphotic conditions. The invertebrate fauna comprises about 160 species and is dominated by molluscs, which is unusual for a Palaeozoic deposit, suggesting that aragonite dissolution produces a major bias in the fossil record. However, most mollusc genera in the Buckhorn deposit are also known from other Pennsylvanian occurrences as recrystallised shells. This shows that preservation bias via preferential aragonite dissolution may be overestimated.     

Early Cambrian molluscs from Sierra de Córdoba (Spain)

Lower Cambrian helcionelloid molluscs are described from the Pedroche Formation in Sierra de Córdoba, southern Spain. The molluscan fauna occurs together with abundant and diverse Small Shelly Fossils (SSF) in limestone units and limestone nodules within terrigenous units. The molluscs are assigned to three new genera and six new species. Three species are previously known from North Siberia and one occurs in Australia, Altai-Sayan Fold Belt, Siberia, Central Asia, China and eastern Germany. The molluscs and other Small Shelly Fossils indicate close palaeogeographic links to Siberia and other continental blocks during the Early Cambrian.     

Molecular Evolution of Mollusc Shell Proteins: Insights from Proteomic Analysis of the Edible Mussel Mytilus

Shell matrix proteins (SMPs) that are embedded within calcified layers of mollusc shells are believed to play an essential role in controlling the biomineral synthesis and in increasing its mechanical properties. Among the wide diversity of mollusc shell textures, nacro-prismatic shells represent a tremendous opportunity for the investigation of the SMP evolution. Indeed, nacro-prismatic texture appears early in Cambrian molluscs and is still present in the shell of some bivalves, gastropods, cephalopods and very likely also, of some monoplacophorans. One key question is to know whether these shells are constructed from similar matrix protein assemblages, i.e. whether they share a common origin. Most of the molecular data published so far are restricted to two genera, the bivalve Pinctada and the gastropod Haliotis. The shell protein content of these two genera are clearly different, suggesting independent origins or considerable genetic drift from a common ancestor. In order to describe putatively conserved mollusc shell proteins, here we have investigated the SMP set of a new bivalve model belonging to another genera, the edible mussel Mytilus, using an up-to-date proteomic approach based on the interrogation of more than 70,000 EST sequences, recently available from NCBI public databases. We describe nine novel SMPs, among which three are completely novel, four are homologues of Pinctada SMPs and two are very likely homologues of Haliotis SMPs. This latter result constitutes the first report of conserved SMPs between bivalves and gastropods. More generally, our data suggest that mollusc SMP set may follow a mosaic pattern within the different mollusc models (Mytilus, Pinctada, Haliotis). We discuss the function of such proteins in calcifying matrices, the molecular evolution of SMP genes and the origin of mollusc nacro-prismatic SMPs.     

Incidence of healed fracture in the skeletons of birds, molluscs and primates

The incidences of healed fracture in the limb bones of birds and the shells of molluscs were estimated by the examination of samples of bones and shells. The results are compared to published data on fracture incidence in molluscs and in primates and other mammals. The relationship between observed incidence of healed fracture, costs of growth and use of the skeleton, and the costs associated with its failure are discussed in terms of a theory of factors of safety.     

Wildlife trade,CITES and the protection of marine molluscs in Indonesia

ABSTRACT

Indonesia is a significant trader in marine molluscs and has a comprehensive legislative framework in place to protect and use molluscs sustainably. The recent inclusion of nautilus in Appendix II of CITES and the general lack of understanding of the level of protection and regulation Indonesia's marine molluscs receive necessitates a review of current laws and agreements. The most relevant are two legally binding international agreements, CITES and the CBD, and Law No 5, and Regulations 8 and 20, dealing with protection, preservation and exploration, respectively. Over the last 30 years, 12 species of mollusc have been legally protected in Indonesia and 7 are included in CITES Appendix II. Species that are not protected can be traded, provided quotas have been set for their commercial exploitation. Seizure data suggest that the illegal trade is considerable – on average almost 10,000 shells/year are confiscated. Seizures do not lead to prosecutions. It is recommended that (a) those involved in the trade of Indonesian marine molluscs need to familiarise themselves better with current legislation and regulation, (b) monitoring of domestic and international trade in marine molluscs needs to be better coordinated and intensified and (c) prosecutions for those trading illegally in marine molluscs need to increase.     

Can the morphology of the integumentary spicules be used to distinguish genera and species of phyllidiid nudibranchs (Porostomata: Phyllidiidae)?

Thirty-eight specimens belonging to four genera and 15 species of the nudibranch family Phyllidiidae were examined to investigate whether the morphology of their integumentary calcareous spicules and/or the occurrence of the spicules within the regions of the body could be used to distinguish genera and species. The spicules were studied separately from five regions of the body of each specimen—the foot, gills, mantle, dorsal pustules (or ridges in Reticulidia) and rhinophores. The mantle itself plus its pustules were found to possess the full complement of spicules in every individual. Four types of spicules were recorded overall—smooth diactines, centro-polytylote diactines, triactines and tetractines. Different regions of the body were found to possess different spicule types: (a) only smooth diactines in the gills, (b) both smooth diactines and triactines in the foot and (c) all of smooth diactines, centro-polytylote diactines and triactines in the mantle, dorsal pustules and the rhinophores. Among the genera, three types of spicules (smooth diactine, triactine, and tetractine) are present in Phyllidia, Phyllidiopsis and Reticulidia, but the form of the spicules is not diagnostic between these genera or between the constituent species. The fourth type of spicule (centro-polytylote diactine) is present exclusively in Phyllidiella, and is diagnostic for that genus. However, we failed to find any difference in spicule form, or composition, or location in the body between the three (closely related) species of Phyllidiella we investigated. Therefore, our key conclusion is that spicule morphology is an extremely important character to tell the genus Phyllidiella apart from all the other genera of the family, but it is not taxonomically informative at the level of species.     

Isolated spicules of Demospongiae from Mt. Duello (Eocene,Lessini Mts., northern Italy): preservation,taxonomy, and depositional environment

Today, class Demospongiae is the largest of phylum Porifera but its fossil record, especially for “soft” demosponges, is rather scarce. This study documents exceptionally preserved isolated opaline spicules, unique for the Bartonian of Italy. Interpretation of morphological types of spicules by comparison with living species lead to their attribution to five orders (Astrophorida, Hadromerida, Haplosclerida, Poecilosclerida, “Lithistida”), seven families (Geodiidae, Placospongiidae, Tethyidae, Petrosiidae, Acarnidae, ?Corallistidae, Theonellidae) and five genera (Geodia, Erylus, Placospongia, Chondrilla, Petrosia, ?Zyzzya). All the described genera are first reported from the Eocene of Europe. This study expands the geographical range of these taxa and fills a chronological gap in their fossil record. The spicules are often fragmented and bear signs of corrosion. They show two types of preservation: glassy and translucent. X-ray powder diffraction analysis confirms that both types are opal-CT with probable presence of original opal-A. Despite this, using a scanning electron microscope the texture of freshly broken surfaces is different. Milky spicules show a porous structure with incipient lepispheres. This feature, together with surface corrosion and the constant presence of the zeolite heulandite/clinoptilolite, point to a certain degree of diagenetic transformation. Macro and micro facies analysis define the sedimentary environment as a rocky shore succession, deepening upward within the photic zone. The spicule-rich sandy grainstone represents the deepest facies and was deposited in a middle-outer carbonate ramp environment, in part in a fairly high energy environment close to storm wave base.     

我国西南地区早寒武世小壳化石Sinosachites

采自四川峨嵋和云南会泽的磷酸盐化的Sinosachites骨片显示出中央沟和侧沟结构,并区别出三种不同类型的骨片(palmate,cultrate and siculate)。这一发现证实,产于澳大利亚的Thambetolepis(Jell,1981)是Sinosachites的晚出同义名。基于上述结构,该产地一些原定为Sachites和Halkieria的标本亦应归入Sinosachites。在Sinosachites属中确认出两个种,即产于华南的Sinosachites flabelliformis He和产于澳大利亚的Sinosachites delicatus(Jell)。在前一种中,左右型对称骨片的存在证实该动物两侧对称。骨片的基部通常保存为磷质内核,表明它比骨片壁更容易磷酸盐化,在组织学上它与骨片壁不同。骨片的基部可能原为有机质或部分矿化。在Sinosachites中,无帽状和束状骨片可能表明在coeloscleritophorans中halkieriids是一个介于wiwaxids和siphogonuchitids之间的类群。     

Diagnostic of Biomphalaria snails and Schistosoma mansoni: DNA obtained from traces of shell organic materials

Freshwater snails belonging to the genus Biomphalaria act as intermediate hosts for the parasite trematode Schistosoma mansoni in Africa and in the neotropical region. Identification of such molluscs is carried out based on morphological characters and the presence of cercariae is verified through squeezing snails between two glass slides or by exposing them to artificial light. However, sometimes, the material collected includes molluscs with decomposed bodies or, yet, only empty shells, which precludes their identification and S. mansoni detection. Due to these difficulties, we have developed a methodology in which DNA may be extracted from traces of organic material from inside shells in order to identify molluscs through polymerase chain reaction and restriction fragment length polymorphism and to detect S. mansoni into these snails, by using low stringency polymerase chain reaction. Species-specific profiles obtained from B. glabrata, B. straminea, and B. tenagophila snails and their shells, maintained in laboratory for ten years, showed the same profiles. S. mansoni profiles showed to be present in shell specimens as far as the eighth week after being removed from aquarium.     

Shell extracts of the edible mussel and oyster induce an enhancement of the catabolic pathway of human skin fibroblasts,in vitro

Mollusc shells are composed of more than 95% calcium carbonate and less than 5% organic matrix consisting mostly of proteins, glycoproteins and polysaccharides. In this study, we investigated the effects of matrix macromolecular components extracted from the shells of two edible molluscs of economic interest, i.e., the blue mussel Mytilus edulis and the Pacific oyster Crassostrea gigas. The potential biological activities of these organic molecules were analysed on human dermal fibroblasts in primary culture. Our results demonstrate that shell extracts of the two studied molluscs modulate the metabolic activities of the cells. In addition, the extracts caused a decrease of type I collagen and a concomitant increase of active MMP-1, both at the mRNA and the protein levels. Therefore, our results suggest that shell extracts from M. edulis and C. gigas contain molecules that promote the catabolic pathway of human dermal fibroblasts. This work emphasises the potential use of these shell matrices in the context of anti-fibrotic strategies, particularly against scleroderma. More generally, it stresses the usefulness to valorise bivalve shells that are coproducts of shellfish farming activity.     

Predation on bellerophontiform molluscs in the Palaeozoic

Shell repair assumed to result from failed predation is documented in 66 specimens of Ordovician-Carboniferous bellerophontiform tergomyan and gastropod molluscs to examine the relationship between the distribution and appearance of injuries, shell morphology and the internal anatomy of the molluscs, as well as the attack strategies of the presumed predators. Furthermore, the distribution of repaired injuries from failed attacks along the apertural margin as a reflection of the nature of the margin and emarginations is investigated. Bellerophontiform molluscs are ideal for this study because of their distinctive isostrophic morphology and the possibility to directly compare broad and narrow conchs with either deep or shallow medial emarginations. The results show that taxa with a deep medial emargination in the form of a slit have significantly more medial injuries than lateral ones. Near-equal frequencies of lateral and medial injuries in specimens with a shallow emargination (slit or sinus) suggest random distribution. Shell form (narrow or broad) does not exert overall control on the distribution of injuries except, perhaps, in some broad explanate shells with an insignificant medial emargination. While this suggests that it is the type of medial emargination that governs distribution of injuries in these forms, it is not clear if this is a result of passive selection due to structural geometry or preferential targeting by predators (i.e. site-specific mode of attack). Predation strategies on bellerophontiform molluscs thus seem to be dependent on the morphological features of the shells rather than their interpretation as tergomyan or gastropod.     

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.     

Homologous shell microstructures in Cambrian hyoliths and molluscs

Hyoliths were among the earliest biomineralizing metazoans in Palaeozoic marine environments. They have been known for two centuries and widely assigned to lophotrochozoans. However, their origin and relationships with modern lophotrochozoan clades have been a longstanding palaeontological controversy. Here, we provide broad microstructural data from hyolith conchs and opercula from the lower Cambrian Xinji Formation of North China, including two hyolithid genera and four orthothecid genera as well as unidentified opercula. Results show that most hyolith conchs contain a distinct aragonitic lamellar layer that is composed of foliated aragonite, except in the orthothecid New taxon 1 that has a crossed foliated lamellar microstructure. Opercula are mostly composed of foliated aragonite and occasionally foliated calcite. These blade or lath‐like microstructural fabrics coincide well with biomineralization of Cambrian molluscs rather than lophophorates, as exemplified by the Cambrian members of the tommotiid‐brachiopod linage. Accordingly, we propose that hyoliths and molluscs might have inherited their biomineralized skeletons from a non‐mineralized or weakly mineralized common ancestor rather than as a result of convergence. Consequently, from the view of biomineralization, the homologous shell microstructures in Cambrian hyoliths and molluscs strongly strengthen the phylogenetic links between the two groups.     

The Machaeridian Lepidocoleus Sarlei Clarke, 1896, from the Rochester Shale (Silurian) of New York State

Eight new specimens and the holotype of Lepidocoleus sarlei Clarke, 1896 from Lagersta¨tten deposits within the Rochester Shale (Silurian, Wenlock) of New York are described to elucidate the morphology, function and construction of the scleritome. The material exhibits an unusual type of dorsal hinge with a pronounced antero-posterior displacement between the two sides. Two specimens have an aberrant sclerite on the right side of segment eleven. One tightly enrolled specimen may demonstrate a method of defence with the stronger protected dorsal side oriented outwards. The presence of a segmented body plan is suggested, based on requirements for a functional spiral enrolment. Distinct anterior and posterior morphologies together with the pattern of rugae provide valuable help in reconstructing disarticulated lepidocoleids.     

a new ichnogenus for etchings made by cheilostome bryozoans into calcareous substrates

Some encrusting cheilostome bryozoans etch a pattern of small pits into hard calcareous substrates, especially calcitic and aragonitic shells of molluscs. These patterns, herein described as Leptichnus ichnogen. nov., comprise pits which are sub-circular to elongate in cross section and are found in either uniserial ( L. dromeus isp. nov.) or multiserial arrangements ( L. peristroma isp. nov., the type species). Each pit corresponds to the location of a single zooid in the bryozoan colony. The oldest known Leptichnus is Late Cretaceous (Maastrichtian), the trace fossil first becomes common in the Cenozoic, and at least nine modern cheilostome genera produce incipient Leptichnus. Leptichnus can be the only evidence remaining of encrusting cheilostomes following taphonomic or diagenetic loss of their calcareous skeletons. The mechanism by which bryozoans etch into their calcareous substrates is unknown but is almost certain to be chemical and necessitates having windows in the basal walls of the zooids which permit contact with the substratum beneath. Etching may result in better adherence to the substrate, giving protection from abrasion and bioerosion.     

A reconsideration of the relationship between polyaxonid and monaxonid spicules in Demospongiae: new data from the genera Crambe and Discorhabdella (Porifera)

The relationships between different spicule lineages of Demospongiae are revised through the ontogenetic study of the main spicules of the genera Crambe and Discorhabdella. The presence of terminal orifices in the basal spines of the asterose acanthostyles of Discorhabdella, and the actines of the desmas of Crambe have been shown by examining young spicules under high magnification. Thus, the polyaxonid origin of both spicule types is hereby supported by the ontogenetic information, and their homology is also supported by their equivalent arrangement in the skeleton. The current differences in shape between both spicule types are considered the result of a divergent morphological evolution from an ancestral polyactinal corpuscle, by the atrophy/hypertrophy of a different number of actines. Arguments are also presented to support the homology of these two spicule types with the sphaeroclons of Vetulina, and other fossil genera. Moreover, the presence of axial canals inside the tubercles of the tuberose tylostyles of Discorhabdella and Crambe tuberosa indicates that the tubercles are actually atrophied actines as in the case of the hadromerid genus Terpios. According to the ontogeny, the tuberose morphology of these spicules may correspond to the retention of an ancestral characteristic in the Poecilosclerida and Hadromerida; in this case, a monophyletic origin, is suggested between both taxa. From the overall results here presented, the tetraxonid spicule, presently considered by most authors as the primitive morphotype, as well as some monaxons, could be considered as evolving from a polyaxial form.