New brachiopod subfamily Anechophragmiinae (Strophomenida) from the Ordovician of the Leningrad Region

A new strophomenid subfamily Anechophragmiidae is distinguished based on the peculiarities of cardinalia. The strophomenids of this subfamily lack cardinal process at all developmental stages; their socket ridges accrete and form a high plate, which closes the pedicle opening. Two genera are referred to the subfamily: Anechophragma Neuman, 1976 and Biseptata gen. nov. with new species B. briani sp. nov. from the Ordovician of the Leningrad Region. The shell structure, exterior, endoskeleton and ontogeny of A. rarum and B. briani were studied in detail due to the excellent preservation of the material. Two species are referred to Anechophragma: A. rarum Neuman, 1976 and A. alexandrae (Andreev, 1993).     

A new early cyclostome bryozoan from the Lower Ordovician (Volkhov Stage) of Russia

Goryunovia hemiseptata n.gen. n.sp. is an unusual Lower Ordovician cyclostome bryozoan, represented by a single colony from the Middle Volkhov Stage (Arenig) of the Leningrad Oblast. The encrusting uniserial colony consists of large, slender zooids, many with closely-spaced partial diaphragms (hemisepta), and has a distinctive trichotomous branching pattern. Skeletal organization is of the sagenellid grade: calcified interior walls appear to be present, and the exterior frontal walls lack pseudopores. As details of microstructure and early astogeny are unknown, it is difficult to interpret the phylogenetic relationships ofGoryunovia until further material is forthcoming. However, there is some resemblance with the enigmatic hederellids, which appear in the Upper Silurian and possibly range into the Triassic.     

Structure of the first-formed shell of the Middle Ordovician orthid-like brachiopods from the Leningrad Region

Shell structure of the first-formed shell of the Middle Ordovician orthid-like brachiopods from the Leningrad Region is described. The 190-μm-wide first-formed shell is composed of finely granular layer while 700-μm-wide first-formed shell is fibrous. Thus the order Orthida in the Early Paleozoic included brachiopods with both planktotrophic and lecithotrophic larvae in the ontogeny.     

Bryozoans as taphonomic engineers,with examples from the Upper Ordovician (Katian) of Midwestern North America

A combination of encrusting calcitic bryozoans and early seafloor dissolution of aragonitic shells recorded in the Cincinnatian Series of the upper Midwest of North America allowed the preservation of abundant moulds of mollusc fossils bioimmured beneath the attachment surfaces of the bryozoans. We here call this preservational process ‘bryoimmuration’, defined as a bryozoan‐mediated subset of bioimmuration. The bryozoans moulded very fine details of the mollusc shells, usually with more accuracy than inorganic sediment moulds. Most of the bryozoans are heterotrypid trepostomes with robust low‐Mg calcite skeletons. The molluscs are primarily bivalves, gastropods, nautiloids and monoplacophorans with their originally aragonitic shells now dissolved. Many of the encrusting bryozoans are so thin and broad that they give the illusion of calcitic mollusc shells clinging to the moulds. Some molluscs in the Cincinnatian, especially monoplacophorans and epifaunal bivalves, would be poorly known if they had not been bryoimmured. Unlike internal and external moulds in sediment, bryoimmured fossils could be transported and thus record aragonitic faunas in taphonomic assemblages (e.g. storm beds) in which they would otherwise be rare or absent. In addition, bryoimmurations of aragonitic shells often reveal the ecological succession of encrustation on the shells by exposing the earliest encrusters and borings that were later overgrown. Bryoimmuration was common during the Late Ordovician because the calcite sea at the time quickly dissolved aragonitic shells on the seafloor before final burial, and large calcitic bryozoans very commonly used molluscs as substrates. Bryoimmuration is an important taphonomic process for preserving aragonitic faunas, and it reveals critical information about sclerobiont palaeoecology. Several Cincinnatian mollusc holotypes are bryoimmured specimens. Bryozoans involved in bryoimmuration enhance the preservation of aragonitic fauna and thus act as taphonomic engineers.     

A new genus of Parablastoidea (echinodermata) from the Middle Ordovician of Ladoga glint on the Volkhov river (Ladoga region)

A new genus and species of the small echinoderm class Parablastoidea, with an unusual starshaped theca, from the Middle Ordovician of the lower reaches of the Volkhov River is described. Functional features of its food-gathering system, the origin and functional role of the ambulacral and oral crests are discussed.     

Volkhov graptolites from the lower-middle Ordovician boundary beds of the St. Petersburg region,Russia

The lower and lowermost Middle Ordovician strata of the Volkhov Stage exposed in the vicinity of St. Petersburg, Russia, yield a graptolite fauna at several stratigraphic levels, being more often confined to the mud-mound clays than to the normally stratified, Condensed carbonates. Overall taxonomic diversity of the Volkhov graptolites is relatively low and associations include no more than seven species in ail localities. TheTetragraptus, Didymograptus andXiphograptus species found are pandemic and have quite extensive stratigraphie ranges within the mid-Arenig Series. Based on the graptolite zonation, the Volkhov Stage can be correlated to thePseudophyllograptus angustifolius elongatus andDidymograptus (Expansograptus) hirundo graptolite biozones of Baltoscandia and to the upperDidymograptus simulans toDidymograptus (Expansograptus) hirundo biozones of the British graptolite succession. TheIsograptus victoriae lunatus lower zonal boundary probably falls within the graptolite-bearing interval of the lower Volkhov Stage. As the result of indirect biostratigraphic and interpretative lithological correlations, the first appearance ofUndulograptus austrodentatus at the base of the Darriwilian Stage is deemed to be close to the boundary of theMegistaspis simon andM. limbata trilobite biozones and the lowerBaltionodus norrlandicus conodont Biozone of the upper Volkhov Stage. Seven dichograptid species belonging to four genera are described, one of them,Azygograptus volkhovensis n. sp., new.      

Cryptostomid Bryozoans From The Sassito Formation,Upper Ordovician Cool‐Water Carbonates of the Argentinean Precordillera

Abstract: Two new bryozoan species are described from the Upper Ordovician Sassito Formation of the Argentinean Precordillera: Moyerella  spinata sp. nov. and Phylloporina  sassitoensis sp. nov. The bryozoans are found in cool‐water carbonates. The Silurian genus Moyerella is reported the first time in the Ordovician, showing palaeobiogeographic connections with Estonia and Siberia.     

Bryozoans of the genera Stomatopora Bronn and Stoporatoma gen. nov. (Stenolaemata) from the Middle Jurassic of Moscow City and the Moscow Region

Encrusting uniserial bryozoans are recorded from the Middle Callovian of Moscow city and the Moscow Region: Stoporatoma gerasimovi gen. et sp. nov. and three species of the genera Stomatopora Bronn; i.e., S. dichotoma (Lamouroux), S. waltoni Haime, and S. bajocensis (Orbigny). Some morphological characters and environmental conditions of these bryozoans are discussed. A new bryozoan that is characterized by a large size and distinctive circular reptozooecia is described.     

Bryozoans as substratum of fossil fistulose Foraminifera (Fam. Polymorphinidae)

In the Upper Cretaceous-Lower Tertiary sections exposed in the Curfs quarries at Berg (munic. Berg en Terblijt - also known as Geulhem, southern Netherlands) and some other localities, numerous foraminifers of the family Polymorphinidae with complete fistulose apertures have been found. These apertures, which are equipped with circular openings and auxiliary apertural chambers, branching and numerous narrow projecting tubes or stolons, have been widely reported, but their role has been the subject of controversy. The Dutch material shows the foraminifers attached with the apertural tubes to fragments of bryozoan colonies or molluscan shells, suggesting that the tubes could perhaps act as holdfast organs. Most specimens were found in calcarenites of the nearshore facies. The foraminifers cannot be treated as symbiotic organisms nor parasites but as epifauna in search of protection from mechanical destruction by waves and current action. The present case may be best explained as an adaptation of sessile foraminifers with fragile hyaline tests to live in highly disadvantageous, high-energy conditions.     

Evolution of the colonial growth habit in the ordovician bryozoans of the class stenolaemata: Feeding adaptations (Leningrad Region,Russia)

Based on the study of the growth habits and the relief of the colony surface in bryozoans of the class Stenolaemata from the Lower (Latorp horizon) and Middle (Volchov and Kunda horizons) Ordovician of the Leningrad Region, these bryozoans are shown to develop from the simple, unilaminate colonies (B_I^β) to the massive colonies with a nodular surface and smooth columnar colonies (B_II^α), which subsequently evolved into the columnar-spiral (B_II^β) and more complex erect branching and fenestrate constructions (B_II^γ), and subsequently into the branching, articulate colonies (B_III^α). The apertures of autozooecia and the character of their arrangement on the colony surface changed correlatively from the circular (B_I^β) to polygonal and roundedpolygonal, randomly arranged apertures, and subsequently to the oval apertures (B_III^α) arranged in strictly regular longitudinal or longitudinal-diagonal rows or in a quincuncial pattern. Thus, the development of growth habits in the bryozoans under consideration has a progressive character. It is expressed in the progressive increase in the complexity of growth habits of colonies and in the more regular arrangement of apertures and other structures on the colony surface. The directionality of morphological changes in the growth habits of colonies of Ordovician bryozoans was apparently closely associated with the development of more complex environmental interactions of these bryozoans, especially with water currents supplying food particles. It is suggested that the high competitive ability of bryozoans of the class Stenolaemata at early stages of its development in the basin of Baltoscandia was apparently due to the better use of food resources.     

Ultrastructure and Development of the Ooecial Walls in Some Calloporid Bryozoans (Gymnolaemata: Cheilostomata)

In the brood chambers (ovicells) of six calloporid cheilostomes studied each skeletal wall consists of four calcified layers: (1) a very thin superficial layer of planar spherulitic crystallites, (2) an upper (outer) layer with wall-perpendicular prismatic ultrastructure, (3) an intermediate lamellar layer, and (4) a lower (inner) wall-perpendicular prismatic layer. Comparative studies of both the ovicell wall ultrastructure and early ovicell formation showed a hypothetical opportunity for evolving complex (multilayered) skeletal walls by fusion of the initially separated gymnocystal and cryptocystal calcifications in Cheilostomata. In two species studied, a bilobate pattern in the final stage of the formation of the ooecial roof was encountered in specimens with the cuticle preserved. A possible explanation to this finding is discussed – the bilobate pattern is suggestive of the hypothetical origin of the brood chamber from (1) two flattened spines, or (2) reduction in spine number of an originally multispinous ovicell.     

Colony Growth Pattern in Electra pilosa (Linnaeus) and Comparable Encrusting Cheilostome Bryozoans

Colony growth pattern is described in E. pilosa, an abundant cheilostome bryozoan commonly found as an epiphyte of Laminaria. Each zooid has 4 potential budding loci—one distal, two lateral and one proximal. The ancestrula buds daughter zooids from all of these loci; the two lateral buds appear first, followed by the distal bud and, after a long delay, the proximal bud. The laterally budded zooids curve inwards as they grow to form a triad with their distally budded sibling zooid. ‘Mature’ multiserial colonies growing on flat substrata consist of a series of radially diverging sectors. Each sector has an axis, generally of 3 parallel rows of zooids, flanked by wings consisting of rows of zooids originating as lateral buds from the section axis which infills the area between the axes. Occasional colonies occur with uniserial or semiuniserial growth patterns. These resemble colonies of the obligatory uniserial species Pyripora catenularia and poorly fed colonies of the related Conopeum tenuissimum, which is normally multiserial like E. pilosa. The ‘composite multiserial’ colonies of E. pilosa differ in several respects from ‘unitary multiserial’ colonies characteristic of most sheet-like cheilostomes, including the well-known Membranipora membranacea. Composite and unitary multiserial growth patterns may have evolved independently from uniserial ancestors.     

Bucania (Gastropoda) from the Ordovician of Estonia

Seven species ofBucania Hall 1847 from the Ordovician of Estonia are presented, also taking into consideration Pleistocene drift material from Germany, and their stratigraphical and geographical distributions are revised. The Middle Ordovician speciesBucania latissima Koken 1897 andBucania salpinx Koken 1897 are tentatively assigned toMegalomphala Ulrich inUlrich &Scofield 1897, while the Lower Ordovician speciesBucania macera Koken inKoken &Perner 1925 is placed inSalpingostoma Roemer 1876. The Middle OrdovicianBucania czekanowskii (Schmidt 1858) and the Upper OrdovicianBucania radiata (d’Eichwald 1856) were earlier considered conspecific, but based on study of the type material they are here considered distinct species.Salpingostoma cornu (Koken 1897), commonly referred to this genus because of the trema, is here transferred toBucania. Two Upper Ordovician specimens ofBucania display wide and abruptly flaring apertures morphologically far removed from other species of the genus.     

Latest Ordovician graptolites from the Mandalay Region,Myanmar

The graptolite fauna of the Mandalay Region, Myanmar, is poorly known. In this paper, 13 species in the genera Avitograptus, Korenograptus, Metabolograptus, Neodiplograptus and Normalograptus are described from the uppermost Ordovician strata of the area. Two of these species, Korenograptus selectus X. Chen n. sp. and Neodiplograptus mandalayensis X. Chen n. sp., are new. On the basis of the graptolite faunas, a biostratigraphic scheme for the uppermost Ordovician (Hirnantian: Metabolograptus extraordinarius Biozone and Metabolograptus? persculptus Biozone?) strata in this area is erected.     

Agglutinated conical foraminifera from the Lower-Middle Eocene of the Trentinara Formation (southern Italy)

Five taxa of agglutinated conical foraminifera were recorded for the first time in the Trentinara Formation, and two of them are new. Barattolites trentinarensis n. gen. n. sp. shows high conical shape, an eccentric proloculus, trochospiral early chambers, two orders of radial subepidermal partitions and columnar pillars. It is recorded in the Ypresian of Panno Bianco Mt. (Calabria) and in the Ypresian-Lower Lutetian of Serra Pastorella (Basilicata). Pseudochrysalidina (?) variospira n. sp. shows a high conical test, a trochospiral juvenile growth stage, a megalosphere in apical position, and low pillars and chambers in the adult stage. It is known in the Ypresian of Serra Pastorella. Agglutinated conical foraminifera fill the late Lower to early Middle Eocene gap in their Paleogene record. Their very intermittent record is due to their extremely narrow ecological range.     

Horizon of the oldest known bryozoans (Ordovician)

Among the six species of fossil bryozoans described by Xia et al. [Xia, F.S., Zhang, S.G., Wang, Z.Z., 2007. The oldest bryozoans: new evidence from the late Tremadocian (Early Ordovician) of East Yangtze Gorges. Journal of Paleontology 81 (6), 1308–1326] from the Fenghsiang Formation of the Chenjiahe section of Yichang and the Guanzhuangping section, Liujiachang Town of Songzi, the Yangtze Gorges, Nekhorosheviella nodulifera occurs in the pristinus Conodont Subzone (lower Subzone of deltifer Conodont Zone) and the five other species are associated with the conodont Paltodus deltifer deltifer and the graptolites Acanthograptus sinensis and A. erectoramus. Based on the conodonts and graptolites, this bryofauna stratigraphically corresponds to the A. sinensis Graptolite Zone or P. deltifer Conodont Zone. The bryofauna is of Tremadocian Age (Early Ordovician) and represents the oldest bryozoans so far as known.     

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.     

Ammonite-benthic Foraminifera turnovers across the Lower-Middle Jurassic transition in the Lusitanian Basin (Portugal)

This paper describes and characterises the co-occurrence of ammonite and benthic foraminiferal assemblages across the São Gião outcrop (Central Portugal), a reference section for the Lower-Middle Jurassic boundary in the Lusitanian Basin. The upper Toarcian-lower Aalenian marls and marly-limestones in this section provide a precise and detailed ammonite-based biostratigraphic zonation, with a mixed assemblage of northwest European and Mediterranean faunal elements, associated with benthic foraminifera assemblages with northern hemisphere affinities, both correlatable with the Aalenian GSSP at the Fuentelsaz section (Iberian Cordillera, Spain). A total of 447 well-preserved ammonite specimens and 13.116 foraminifera have been studied; no evidence was detected of any taphonomic processes that could have changed the original assemblages. From a biostratigraphic point of view, the ammonite record has enabled four biostratigraphic units to be recognised (the Mactra and Aalensis subzones of the Aalensis Biozone in the upper Toarcian, and the Opalinum and Comptum subzones of the Opalinum Biozone in the lower Aalenian). With regard to the benthic foraminifera, the taxa identified have enabled the Astacolus dorbignyi Zone and 11 bioevents to be identified, most of which representing local biostratigraphic proxies. However, the increase in the relative abundance of Lenticulina exgaleata Dieni from the upper part of the Opalinum Subzone to the lower part of the Comptum Subzone has a regional value. The constant and continuous ammonite record of northwest European taxa, together with typical Mediterranean taxa – namely Grammoceratinae – throughout the section, the high relative abundance of Miliolina representatives – generally interpreted as foraminifers typical of shallow waters – and the absence of foraminiferal forms typical of cool waters, do not support the inference of cool seawater temperatures attributed to the Early Aalenian, or the global character of the “Comptum cooling event”, at least with reference to the Lusitanian Basin.     

Family Lycophoriidae (Brachiopoda) from the Ordovician of Baltoscandia

The family Lycophoriidae from the Middle Ordovician of Baltoscandia with one monotypic genus and five species is revised. New inner structures were revealed and diagnoses of the family, genera, and species were specified in the study of cross sections and microstructure of the shell. The third prismatic layer, complex dental plates, and socket ridges with short pointed lateral outgrowths were recorded. The family Lycophoriidae cannot be assigned with confidence to any known brachiopod order.