New observations on the skeletons of the earliest bryozoans from the Fenhsiang Formation (Tremadocian,Lower Ordovician), Yichang,China

The earliest unequivocal bryozoans occurred in the Fenhsiang Formation (upper Tremadocian, Lower Ordovician) of Yichang, South China, providing important clues about the early evolution of primitive bryozoans. In this study, SEM and EDAX were used to analyze the microstructure of the walls of two bryozoan genera, Nekhorosheviella and Orbiramus, from the Fenhsiang Formation. All walls of Nekhorosheviella and endozonal walls of Orbiramus show poor preservation in thin sections, with a granular appearance reflecting extensive neomorphism, whereas exozonal walls of Orbiramus are distinctly laminated. These preservational differences may reflect skeletal chemistry, particularly the magnesium content of the calcite. Phosphatic skeletal linings were found to be distributed unevenly in the autozooecia of Nekhorosheviella, but were absent in Orbiramus.     

über Opercula bei der fossilen BryozoengattungInversaria v. Hagenow 1851 (Cheilostomata,Ob. Kreide)

The calcareous opercula ofInversaria tubiporacea (Goldfuss 1826) from the Dutch Maastrichtian Chalk-tuff are described and figured by Stereoscan photographs. The genusInversaria v.Hagenow 1851, as demonstrated byVoigt &Williams (1973), belongs to the Cheilostomata and not, as maintained hitherto, to the Cyclostomata. The discovery of true opercula in situ inInversaria also serves as important evidence for the cheilostomatous character of that genus. In comparison with the opercula of Recent Cheilostomes, these opercula, the first to be found in fossil species, are highly calcified and provided with strange outgrowths the like of which have never been observed in Recent species. On their frontal surface exists a conical process which is directed distally and is often curved. It starts from the hollow central disc of the operculum. On the reverse (internal) surface two symmetrical pairs of branching spines (sclerites) arise vertically from a horizontal cross-bar; the external pair is more prominent with antler-like apophyses, projecting like two corner pillars into the lumen of the zooecia. The median pair is lower and often found to be coalesced into a knobbed or thorny clew. The zoarium ofInversaria tubiporacea consists of a vertical central axis surrounded by regular concentric layers of subsequently formed zooecia with budded only by proliferation after the degeneration of the foregoing older ones (frontal budding) and not by simple encrustation of autonomous outer layers of new zooecia enveloping the periphery of the zoarium. The zooecial tubes are observed to continue directly through all these outer layers, but in fast consist of a series of distinct zooecia following each other by budding and subsequent degeneration. This may be demonstrated by the fact that in the same tube passing through all these layers the opercula of several different generations of polypides are represented. Therefore, it must be concluded that, in similarly constructed zoaria of cyclostomatous and trepostomatous Bryozoa, the zooecial tubes which apparently were secreted only by one polypide must have been built up by numerous successive generations of zooids, each budded every time the degeneration of a parental zooid occured.     

Regressive astogenese beiNudonychocella n.g.n.sp. und anderen bryozoen aus der tuffkreide von maastricht

Nudonychocella nuda n.g.n.sp. from the Maastrichtian chalk tuff is a cheilostome bryozoan species which shows totally opened “membranimorph” zooecia and avicularia. Its ancestrula, however, displays — likeOnychocella Jullien — semicircular opesiae and normally formed calcified frontal walls (cryptocysts), revealing its lineage from this genus which belongs to the Coilostega. This is suggested to be a matter of regressive astogeny, unknown until now in bryozoology, during which the calcareous cryptocyst, being characteristic for that genus, was totally reduced.Onychocella cyclostoma (Goldf.) andO. koninckiana (v. Hagenow) also show the tendency to reduce their calcareous frontal walls which are still widely normal during the neonastic stage of the colony. InCastanopora bipunctata (GOLDF.), however, the cribrimorph frontal shield may disappear totally. A satisfactory explanation of this phenomenon may be that the neonastic stage characterising the peripheral growing tip of the colony with its incompletely calcified frontal walls of the zooids dominated the whole colony, induced by a stop of the calcification of the cryptocyst, with the exception of the ancestrula, the result of which being a secondary membranimorph stage, characteristic for the Malacostega. The reduction of the calcification does not contradict to Dollo’s rule concerning the irreversibility of the evolution. Consequences arising for taxonomic questions and phylogenetic research are discussed.     

Septocea n. g. (Bryozoa cyclostomata), ein neues Kreide-Bryozoen-Genus von Rügen und Maastricht

Septocea septifera n.g. n.sp. (Family Semiceidae Buge) is a very strange free-walled cyclostome bryozoan species of Maastrichtian age with regard to its apertural morphogenesis. The zoarium is erect, eschariform, without heteromorphs, the aperturae lack ringlinke peristoms and are subdivided by vertical septa. The septa are recognized as extern walls of axially budded immature zooecia in the interior of the living chamber. The oval to triangular apertura is subdivided by the septa into one larger and one or two smaller openings. The evidence that axial intrazooecial budding also exists in other, not closely related taxa, proves that these structures are convergent. Their morphogenesis, systematic value and the taxonomic status of the Family Semiceidae are discussed.     

Revision of the Cambrian discoidal animals Stellostomites eumorphus and Pararotadiscus guizhouensis from South China

The discoidal fossils identified as Stellostomites eumorphus Sun & Hou, Rotadiscus grandis Sun & Hou and Rotadiscus guizhouensis Zhao & Zhu are abundant in the Cambrian Chengjiang and Kaili Lagerstätten of southwest China. Reinvestigation of all available specimens of S. eumorphus and R. guizhouensis indicates that S. eumorphus has radiating lobe structures different from those of Eldonia ludwigi Walcott and has one additional set of dorsal radiating canals, and has a distinct central cavity, two characters that are not present in E. ludwigi. R. guizhouensis differs from R. grandis in the morphology of the disc, internal radiating lobes and tentacles. This supports the validity of the genus StellostomitesSun & Hou, 1987, and substantiates the erection of a new genus, Pararotadiscus nov. gen., to receive Rotadiscus guizhouensis Zhao Zhu, 1994. Anatomical and taphonomical analyses indicate that S. eumorphus and P. guizhouensis were gregarious pelagic animals. The new anatomical information emphasize close phylogenetic relations with lophophorates (U-shaped intestine, circumoral tentacles and ectodermal, marginal accreted disc), though some features (e.g. dendritic tentacles, ventral pustules that may relate to reduced podia) do not exclude affinitics with echinoderms.     

Bryozoans of the order Melicerititida: Morphological features and position of the order in the taxonomic structure of the class Stenolaemata

Morphological features of a distinctive group of Post-Paleozoic bryozoans belonging to the order Melicerititida (Stenolaemata) are discussed. They include funnel-shaped zooecia, facettes, semicircular zooecial apertures with a straight proximal edge, calcified opercula, and various types of vicarious eleozooecia, which resemble avicularia of cheilostome bryozoans. These morphological structures are unique within the class Stenolaemata. They not only differentiate these bryozoans both morphologically and evolutionarily from Cyclostomata, in which some authors place them, but also from all the other orders of this class.     

WALL STRUCTURE AND ACANTHOPORES IN THE BRYOZOAN LEIOCLEMA ASPERUM

Leioclema asperum (Hall), a typical trepostomatous bryozoan, shows well developed acanthopores which are modified parts of orthodox zooecial walls and not separate skeletal entities. They resulted from locally accelerated forward growth of the wall, hence their distinctive cone-in-cone structure. The comparative absence of growth lines in the axial region of each acanthopore suggests that deposition of calcite in that situation was virtually continuous. There is no reason to believe that the acanthopores were originally hollow and they cannot have housed kenozooids, as is commonly supposed.     

Note on the Bryozoan Pustulopora pustulosa (Goldfuss)

Topotype material of Pustulopora pustulosa (Goldfuss), the type species of Pustulopora Blainville, is investigated and its structure described. It has a distinctive budding pattern in which autozooecia are formed from an axial bundle of zooecia. The gonozooecium is of ' Mecynoecia '- shape.     

Thamniscus King, 1849 (Fenestellida: Bryozoa): William King’s original specimens and their bearing on the genus concept

Reassessment of the suite of specimens used by William King when he erected the fenestrate bryozoan genus Thamniscus in 1849 has shown that they belong to two genera. However, King’s original generic concept only allows for some of these specimens to be included within Thamniscus. These specimens are illustrated. A recent generic treatment is consistent with King’s original generic concept.     

新疆西准噶尔晚泥盆世法门期的苔藓虫动物群及其形态特异性和古环境意义*

本文重新研究了产自新疆西准噶尔晚泥盆世法门期洪古勒楞组和铁列克提组的苔藓虫动物群, 重点关注其形态学特征和古生态学意义。该苔藓虫动物群由隐口目(Cryptostomata)、窗格苔藓虫目(Fenestrata), 变口目 (Trepostomata)和泡孔目(Cystoporata)组成。优势类群隐口目苔藓虫是具有中轴或中板的细枝状和双叶状群体。 它们的虫室具有加厚的外区体壁, 弯曲强烈的自虫室, 数量众多的大虫室(metazooecia)或隐蔽虫室(tectizooecia), 以及径向刺突和/或棘状刺突。多样化的异虫室、刺突、自虫室等结构, 以及不同生长环境中的不同生态组合是新疆西准噶尔法门期苔藓虫成功演化的基础。洪古勒楞组下段和铁列克提组下部的苔藓虫动物群可以划分为三类生态组合(即: No. 1, No. 2和No. 3), 代表前滨—近岸—远岸的沉积环境。其中, 近岸环境的枝状—双叶状—网状苔藓虫组合的属种丰度、分异度最高。     

Proetid trilobites from the middle Telychian (Llandovery,Silurian) Ningqiang Formation,Shaanxi, China

Four proetid trilobite species, Chuanqianoproetus guizhouensis Yin in Yin and Li, 1978, C. shuangheensis Wu, 1977, C. sp., and Latiproetus guizhouensis Yin in Yin and Li, 1978, are described from the Ningqiang Formation in Ningqiang County, Shaanxi, China. They are middle Telychian (Llandovery, Silurian) in age. Chuanqianoproetus and Latiproetus are both regarded as members of the subfamily Warburgellinae; the former has been considered to be a junior subjective synonym of Astroproetus, but on the basis of its morphology we argue here that they represent two independent genera. The poorly sorted bioclastic grainstones containing trilobite sclerites may indicate their deposition in turbulent conditions on an open marine platform.     

Microbial mats associated with bryozoans (Coorong Lagoon, South Australia)

Summary Bryostromatolites are laminated carbonate rocks composed of bryozoan zoarial laminae. The laminated texture is frequently caused by patterns of bryozoan self overgrowth as a regular defensive tactic against microbial fouling. In the Coorong Lagoon (South Australia), another type of bryostromatolite is present where the laminated growth of the weakly calcifying bryozoan speciesConopeum aciculata is postmortally stabilized by cyanobacterial mats at the surface, and fungal mats settling in the zooecial cavities. A tough extracellular slime network produced by benthic cyanobacteria is a trap for sediment particles, provides a method of adhesion to the bryozoan substrate, and produces a biological lamination by the vertical stratification of dead bryozoan skeletons. These slimes are also important for the preservation of cell structures and for their fossilization. Seasonal fluctuations in salinity and water level are the most important regional control factors, causing a phase displacement in the growth optima of microbial mats and bryozoans, thereby resulting in a rigid bryostromatolitic fabric.     

The Madagascan Maastrichtian bryozoans of Ferdinand Canu – Systematic revision and scanning electron microscopic study

In 1922, the first taxonomic work on Maastrichtian bryozoans from Madagascar was published in the Annales de Paléontologie by Ferdinand Canu. Canu described 25 species, 17 of which were regarded as new but the material has never been revised until now. Here we employ scanning electron microscopy (SEM) to illustrate Canu's material and revise the taxonomy. Based on this revision, 23 species, comprising eight cyclostomes and 15 cheilostomes, are recognized. A new genus, Fehiborypora, is introduced for the cribrimorph Cribilina (?) labiatula, and two new species are described: ‘Plagioecia’ antanihodiensis sp. nov. and ‘Escharoides’ charbonnieri sp. nov. Galeopsis parvipora is synonymized with Crustoporina prona Stoliczka. All bryozoan species found are encrusters on echinoids or oysters.     

Arabinose-rich polymers as an evolutionary strategy to plasticize resurrection plant cell walls against desiccation

A variety of Southern African resurrection plants were surveyed using high-throughput cell wall profiling tools. Species evaluated were the dicotyledons, Myrothamnus flabellifolia and Craterostigma plantagineum; the monocotyledons, Xerophyta viscosa, Xerophyta schlecterii, Xerophyta humilis and the resurrection grass Eragrostis nindensis, as well as a pteridophyte, the resurrection fern, Mohria caffrorum. Comparisons were made between hydrated and desiccated leaf and frond material, with respect to cell wall composition and polymer abundance, using monosaccharide composition analysis, FT-IR spectroscopy and comprehensive microarray polymer profiling in combination with multivariate data analysis. The data obtained suggest that three main functional strategies appear to have evolved to prepare plant cell walls for desiccation. Arabinan-rich pectin and arabinogalactan proteins are found in the resurrection fern M. caffrorum and the basal angiosperm M. flabellifolia where they appear to act as ‘pectic plasticizers’. Dicotyledons with pectin-rich walls, such as C. plantagineum, seem to use inducible mechanisms which consist of up-regulating wall proteins and osmoprotectants. The hemicellulose-rich walls of the grass-like Xerophyta spp. and the resurrection grass E. nindensis were found to contain highly arabinosylated xylans and arabinogalactan proteins. These data support a general mechanism of ‘plasticising’ the cell walls of resurrection plants to desiccation and implicate arabinose-rich polymers (pectin-arabinans, arabinogalactan proteins and arabinoxylans) as the major contributors in ensuring flexibility is maintained and rehydration is facilitated in these plants.     

THE CHEILOSTOMATE NATURE OF THE ALLEGED CYCLOSTOMATOUS BRYOZOAN GENUS DYSNOETOPORA

Dysnoetopora celleporoides Canu & Bassler 1926, from the Ripley Formation (Maastrichtian) of the well-known Coon Creek locality (McNairy County, Tennessee), is not a cyclostomate, but a cheilostomate, bryozoan. The cheilostomate affinity of the genus Dysnoetopora is clearly shown by the existence of big avicularia, subsemicircular apertures (suggesting an operculum), septulae with true rosette plates, and ascopores below the aperture. Interzoidal pores and pseudopores, both characteristic of the cyclostomes, are lacking.
The zooecia of the arborescent dichotomous zoarium are dimorphic. An axial bundle consisting of long prismatic zooecia is surrounded by a thick layer of irregular cumulating zooecia. The mode of budding and the confused appearance of the zooecia resembles that of the family Celleporidae, and the related Celleporariidae and Celleporinidae. The presence of ascopores, however, excludes the assignment of Dysnoetopora to any of these families, and necessitates the erection of a new family, Dysnoetocellidae. Ovicelles have not been observed. The type species, and two other species assigned to Dysnoetopora , are discussed.     

A new genus <Emphasis Type="Italic">Acupipora</Emphasis> gen. nov. from the upper carboniferous of the East European platform and problem of classification of bryozoans of the order Fenestellida

The species composition of the bryozoan genus Paucipora Termier et Termier, 1971 is revised. A new species, Paucipora akishinensis sp. nov., and a new genus, Acupipora gen. nov., with the type species Polypora subborealis Schulga-Nesterenko, 1951, are described. The problems of classification of the order Fenestellida are discussed. Criteria for the division of the order into families and subfamilies are developed. The evolution of fenestellids is shown to proceed along the path of morphological differentiation of structural elements of colonies, polymerization of autozooecia, and formation of heterozooecia. It was accompanied by morphological parallelisms. A scheme of the phylogenetic relationships between the families and subfamilies of the order is presented.     

Threshold effects of food concentration on the skeletal morphology of the bryozoan Electra pilosa (Linnaeus, 1767)

Many palaeontological studies rely heavily on characteristics of the preserved phenotype, i.e. the morphology of skeletal hard parts. Although the potential for environmental influences on the phenotype is expected, rarely is the magnitude of the effects quantifiable relative to genetic factors. The clonal/colonial body plan of Bryozoa allows for the partitioning of morphological variance into its genetic and environmental factors addressing the question of, ‘how much phenotypic variation is induced in a population by changing a single environmental factor?’ The effects of variation of food concentration on whole‐colony growth rate and on zooid size/morphology can be profound in bryozoans. Here we test experimentally food effects on the skeletal phenotype of the bryozoan Electra pilosa (Linnaeus, 1767), an encrusting sheet‐like bryozoan. A threshold effect was observed for the relationship between zooecium size and food concentration. Very low concentrations resulted in stunted colonies with small zooecia, but at low to intermediate concentrations a close relationship existed with zooecium size. Maximum zooecium size occurred at submaximal food concentration and submaximum zooecium size occurred at higher food concentrations. Previous studies that have reported no effect of food availability on zooecium size assessed food concentration effects at higher concentrations than were effective in the present study. In the absence of other factors, variation in zooecium size is minimal and unchanging at moderate to high food concentrations. Greater variation in zooecium size is expected at and below threshold food concentrations. We show that the preservable phenotype of these specimens subjected to controlled and induced environmental variation also records information with genetic significance.     

Bryozoans from the Mitikha Formation (Lower Famennian, Upper Devonian) of the Kuznetsk Basin, Russia

Bryozoans from the Mitikha Formation (Lower Famennian, Upper Devonian) in the Kuznetsk depression are described for the first time. This bryozoan assemblage comprises both the well-known species Leioclema numerosum Moroz., L. ramosum Nekh., and Nicklesopora graciosa Troiz. and new taxa: L. kusmense sp. nov. and Megacanthopora glubokaensis sp. nov. The bryozoan assemblage contains some species common with the Famennian bryozoan assemblage of Kazakhstan.     

Molecular evidence that the deadliest sea snake Enhydrina schistosa (Elapidae: Hydrophiinae) consists of two convergent species

We present a striking case of phenotypic convergence within the speciose and taxonomically unstable Hydrophis group of viviparous sea snakes. Enhydrina schistosa, the ‘beaked sea snake’, is abundant in coastal and inshore habitats throughout the Asian and Australian regions, where it is responsible for the large majority of recorded deaths and injuries from sea snake bites. Analyses of five independent mitochondrial and nuclear loci for populations spanning Australia, Indonesia and Sri Lanka indicate that this ‘species’ actually consists of two distinct lineages in Asia and Australia that are not closest relatives. As a result, Australian “E. schistosa” are elevated to species status and provisionally referred to Enhydrina zweifeli. Convergence in the characteristic ‘beaked’ morphology of these species is probably associated with the wide gape required to accommodate their spiny prey. Our findings have important implications for snake bite management in light of the medical importance of beaked sea snakes and the fact that the only sea snake anti-venom available is raised against Malaysian E. schistosa.