A new pachyosteomorph arthrodire (Pisces: Placodermi) from the Upper Frasnian of the Central Devonian Field,Russia

A new genus and species of pachyosteomorph arthrodire, Omalosteus krutoensis gen. et sp. nov. from shallow-water marine deposits of the Evlanovo Regional Stage (Upper Frasnian, Upper Devonian) of the Central Devonian Field is described. It is tentatively referred to the family Trematosteidae Gross, 1932, which was earlier believed to be endemic to central Europe. The new genus is characterized by a rounded, dorsoventrally compressed cross section of the pectoral region and smooth head shield and postcranial membrane bones. The centrale is elongated, forming a narrow lateral lobe. The praeorbitale, postorbitale, and centrale come in contact in the center of the orbital region. The mediodorsale is wide, its carinal process projects considerably posteriorly. The anterior margin of the anterior ventrolaterale lacks articular facets for the interlaterale.     

<Emphasis Type="Italic">Oredezhosteus</Emphasis>, a new psammosteid genus (Heterostraci,Psammosteiformes) from the Lower Frasnian (Upper Devonian) of the Main Devonian Field

A new psammosteid, Oredezhosteus kuleshovi gen. et sp. nov., from the Amata Regional Stage (Lower Frasnian) of the Leningrad Region is described. In addition, Psammosteus livonicus Obruchev from beds of the same age from Latvia is included in the new genus. The major diagnostic characters distinguishing Oredezhosteus gen. nov. from Psammosteus Agassiz are the large rounded striated tubercles, which cover more than half width of the branchials, and the long base of the branchial plates.     

On Frasnian ammonoids of the New Siberian Islands

Ammonoids from the basal beds of the Nerpalakh Formation (Lower Frasnian) of Belkovsky Island (New Siberian Archipelago) are systematically studied. Taxonomically, the assemblage studied (Manticoceras insulare sp. nov., Tornoceras typum (Sandberger, 1851), and T. contractum Glenister, 1958) is similar to the Early Frasnian ammonoid assemblage of South Timan, from which its is distinguished by the absence of the genera Timanites and Komioceras. The same beds contain conodonts of the Palmatolepis transitans Zone (= MN 4 Zone of the Montagne Noire standard succession), which allow the correlation of the beds studied with the Timanites keyserlingi and Komioceras stuckenbergi ammonoid zones of South Timan. The Early Frasnian ammonoids could supposedly have entered the region of the New Siberian Archipelago from the southwest at the time of a major transgression, which facilitated the distribution of the genera Manticoceras and Tornoceras. A new species of the genus Manticoceras is described.     

Psammosteiforms (Agnatha,Heterostraci) from the Lower Frasnian of the Mikhailovskii Mine,Kursk Region,Russia

Psammosteiforms, including Tartuosteus (?) zheleznogorskensis, sp. nov. and Psammosteus cf. P. praecursor Obruchev, from the Lower Frasnian (Upper Devonian) of the Mikhailovskii Mine (Kursk Region) are described. Agnathans, placoderms, crossopterygians, and acanthodians from this locality are determined. The similarity of the Mikhailovskii Fish Assemblage to the assemblage of southern Timan suggests it be assigned to the Upper Timan Regional Stage.     

Frasnian conodonts from the eastern Russian Platform

The Frasnian conodonts of the eastern Russian Platform from the Timan in the north to the Orenburg Region in the south are characterized in detail both paleontologically and stratigraphically. This paper is a continuation of a previously published monograph (Ovnatanova and Kononova, 2001) on the Frasnian conodonts of the shallow-water strata of the central Russian Platform, where polygnathids prevail. The conodont assemblages from the shallow-water and basinal sections of the Volga-Ural province and Southern Timan are analyzed. Problems and difficulties associated with the correlation of the shallow-water and deep-water Frasnian sections of the eastern Russian Platform and their correlation with the existing zonal conodont scales are discussed. The correlation between the deep-water Mendym deposits and the shallow-water Rechitza and Voronezh strata of the Volga-Ural province with the Vetlasyan and Sirachoi deposits of the Southern Timan is substantiated. The stratotype of the Semiluki Regional Stage of the Central Devonian Field contains equivalents of the lowermost beds of the Domanik Formation (unit 1), based entirely on polygnathids. Phylogenetic reconstructions for Palmatolepis and Polygnathus are suggested based on the ontogenetic series for some species of these two genera and the presence of transitional forms between some of the species. Based on these phylogenetic reconstructions, conodont zonal scales for the shallow-water and deep-water sections of the Frasnian Stage of the Russian Platform are proposed and their correlation with the existing conodont zonal scales is also adduced. Some aspects of biofacies control are considered based on the distribution of conodonts in the sections studied. In Systematic Paleontology, 91 conodont species of the genera Ancyrodella, Mesotaxis, Palmatolepis, and Polygnathus are described, including the new species Palmatolepis menneri, P. kaledai, P. acutangularis, and Polygnathus reitlingerae. DEDICATION To the blessed memory of the outstanding geologist Vladimir Vladimirovich Menner     

Systematics and shell microstructure of the spiriferid genera Echinospirifer and Komispirifer from the Upper Devonian of southern Timan

The type species of the genera Echinospirifer Ljaschenko, 1973 Komispirifer Ljaschenko, 1973 and Mennespirifer Ljaschenko, 1973 were revised based on material from the memorial collection of A.I. Ljaschenko. Mennespirifer is recognized as a junior synonym of the genus Komispirifer; the genera Echinospirifer and Komispirifer differ in fine ornament and the structure of the shell wall.     

The placoderm <Emphasis Type="Italic">Plourdosteus livonicus</Emphasis> (Eastman) in the early Frasnian of the Central Devonian Field and the trophic structure of the Mikhailovskii Fish Assemblage

The placoderm Plourdosteus livonicus (Eastman) (Euarthrodira, Coccosteina) from the Upper Timanian Mikhailovskii Fish Assemblage of the Central Devonian Field is described. The composition and structure of the assemblage are discussed and compared with later Frasnian fish assemblages of the Central Devonian Field.     

新疆柯坪和甘肃平凉上奥陶统底部附近的牙形刺

新疆柯坪大湾沟和甘肃平凉官司庄剖面是Nemagraptusb gracilis带及上奥陶统底界的重要剖面,研究这两剖面的牙形刺具有十分重要的意义。本文描述了采自新疆柯坪大湾沟和甘肃平凉官司庄剖面上奥陶统底界附近的牙形刺共13属18种。     

Morphological diversity of the exine sculpture of some Frasnian spores from the northern Timan: Applications for taxonomy and significance for spore dispersal

Microspores and megaspores from micro-and megasporangia of a Late Frasnian plant from the northern Timan are identified as the genus Cristatisporites and Ancyrospora, respectively. The exine sculpture is studied in in situ spores, as well as in dispersed miospores of Cristatisporites, Ancyrospora, and Hystricosporites, found in the rock enclosing the plant. The use of exine appendages as a generic level character is proposed. The shape of appendage extremities and the presence of irregular holes in the exine that are considered to be probable insect feeding damage, allowing us to consider wingless insects as main dispersal agents of the spores.     

Fossil plants with spores in the sporangia from the Upper Devonian (Frasnian) deposits of northern Timan

Fossil plants from the Upper Devonian (Frasnian) of northern Timan are studied. The sporangia contain well-preserved spores, which were studied in transmitted light using a scanning electron microscope. The genus Gutzeitia S. Snigirevsky, gen. nov. is established. Macroremains and in situ spores of G. timanica (Petros.) S. Snig., comb. nov. and ?Cephalopteris mirabilis (Nath.) Nath. are described. Microspores in Dimeripteris gracilis Schmalh. are identified, and microspores and megaspores in ?Cephalopteris mirabilis are studied for the first time.     

First selenosteid placoderms from the eastern Anti‐Atlas of Morocco; osteology,phylogeny and palaeogeographical implications

Abstract: A new placoderm assemblage is reported from the Kellwasser facies of the eastern Anti‐Atlas, Morocco. This is the first record of an abundant Frasnian placoderm assemblage from Africa. The following new selenosteid taxa are described: Draconichthys elegans gen. et sp. nov., Enseosteus marocanensis sp. nov. and Walterosteus lelievrei sp. nov. In addition, material of Rhinosteus cf. parvulus is figured and described for the first time from Gondwana. The genera Enseosteus, Rhinosteus and Walterosteus are reviewed. ‘Wildungenichthys’ is regarded as a junior subjective synonym of Walterosteus. The new material and a revision of the taxa from Bad Wildungen, Germany, are the basis for a new phylogenetic analysis of the selenosteid arthrodires. The monophyly of the selenosteids is confirmed. The North American selenosteids are a sister group of Moroccan and European selenosteids, excluding Pachyosteus. The Moroccan vertebrate assemblage resembles that of Bad Wildungen. This supports the close palaeogeographical positions of Gondwana and Laurussia during the Late Devonian and indicates that biogeographical barriers for placoderms that could have separated the two assemblages were absent.     

Reconstructing atoll-like mounds from the Frasnian of Belgium

A succession of Frasnian mounds on the southern border of the Dinant Synclinorium (Belgium) was investigated for their facies architecture, sedimentary dynamics and palaeogeographic evolution. Seven mound facies were defined from the Arche (A) and Lion (L) members, each characterized by a specific range of textures and association of organisms (A2/L2: red or pink limestone with stromatactis, corals and crinoids; A3/L3: grey, pink or green limestone with stromatactis, corals and stromatoporoids; A4/L4: grey limestone with corals, peloids and dasycladaceens; A5/L5: grey microbial limestone; A6/L6: grey limestone with dendroid stromatoporoids; A7/L7: grey laminated limestone with fenestrae; and A8/L8: grey bioturbated limestone). Laterally equivalent sediments include substantial reworked material from the buildups and background sedimentation. Textures and fossils suggest that A2/L2 and A3/L3 facies developed close to storm wave base, in a subphotic environment. Facies A4/L4, occurring near fair weather wave base in the euphotic zone, includes lenses of A5/L5 with stromatolitic coatings and thrombolithes. A6/L6 corresponds to a slightly restricted environment and shows a progressive transition to fenestral limestone of A7/L7. This facies was deposited in a moderately restricted intertidal area. A8/L8 developed in a quiet lagoonal subtidal environment. The mounds started with A2/L2 or A3/L3 in which microbial lenses and algal facies A4/L4 became progressively more abundant upwards. Following 20 m of laterally undifferentiated facies, more restricted facies occur in the central part of the buildups. This geometry suggests the initiation of restricted sedimentation, sheltered by bindstone or floatstone facies. The facies interpretation shows that after construction of the lower part of the mounds during a transgression and a sea-level highstand, a lowstand forced reef growth to the margin of the buildups, initiating the development of atoll-like crowns during the subsequent transgressive stage. The persistence of restricted facies results from the balance between sea-level rise and reef growth.     

New species of Antognathus (Conodonts) from the Famennian deposits of southern Kazakhstan

A new conodont species, Antognathus vjatsheslavi sp. nov., is described from the Famennian shallow-water carbonate deposits of the Bolshoi (Greater) Karatau Range in southern Kazakhstan.     

Taphonomy of acanthodians from the Devonian Bunga Beds (late Givetian/early Frasnian) of New South Wales

Several articulated, but incomplete, acanthodians from the Bunga Beds (late Givetian/early Frasnian) of the southern coast of New South Wales are tentatively identified as ischnacanthids. Heads are missing from all three prepared specimens. They exhibit the following characters: two dorsal fin spines; long, slender scapulocoracoids; slender, relatively deeply inserted, unpaired fin spines; minute scales with a fairly smooth, flat, crown; and an increase in size of normal body scales towards the tip of the tail. The fish are preserved in black, finely laminated shales, which were probably deposited as deep water, lacustrine sediments. The rarity, burial conditions, and headless state of the Bunga Beds acanthodians indicate that they might have died in shallow water, sunk to the bottom, refloated by gas‐induced buoyancy, with the heads lost while drifting out to deeper waters, where the bodies finally sank to a scavenger‐free, anaerobic substrate.     

Progressive drowning of carbonate platform in the Moravo-Silesian Basin (Czech Republic) before the Frasnian/Famennian event: facies,compositional variations and gamma-ray spectrometry

The Moravo-Silesian Basin (MSB; eastern Czech Republic and southern Poland) hosted an extensive shallow-water carbonate platform in the Middle Devonian to Frasnian interval. The platform drowned in a stepwise fashion from the Palmatolepis hassi to the Pa. linguiformis zone. Three types of drowning successions were revealed from conodont biostratigraphy, facies, microfacies and gamma-ray spectrometry data: (A) drowning to periplatform turbidite setting; (B) drowning to (hemi)pelagic seamount setting and (C) drowning associated with the stratigraphical gap. In the lower Pa. hassi zone, rapid subsidence caused the platform to drown locally along the N–S to NW–SE trending faults (type A drowning). In the upper Pa. rhenana to the Pa. linguiformis zone, the drowning accelerated in the western part of the MSB due to locally higher subsidence rates combined with the Late Frasnian biotic crisis (type B). In the southern part of the basin, the platform emerged shortly before the Frasnian/Famennian (F/F) boundary and drowned in the Early to Late Famennian (type C). The primary cause of drowning was differential subsidence at the Laurussian passive margin. Eustatic sea-level fluctuations, if any, contributed only to a minor extent to the Late Frasnian drowning, but were effective in type C drowning during the Famennian. The drowning boundaries are associated with increased contents of K and Th, reflecting the deceleration of carbonate production. Uranium contents display isolated peaks that roughly correlate with the drowning boundaries or the stratigraphic gaps associated with the F/F boundary. The uranium contents are considered to reflect local depositional conditions and are not suitable for stratigraphic correlation. On the other hand, from the K and Th contents, we can infer Late Frasnian sea-level fluctuations with duration on the order of 1 Myr. These cyclic variations in K and Th contents proved to be useful in platform-to-basin stratigraphic correlation.     

贵州南部独山地区泥盆纪弗拉期的石燕贝类腕足动物

弗拉期是了解泥盆纪弗拉-法门灭绝事件之前古代生物多样性的一个关键阶段.贵州南部的独山地区因其所具有的完整层序及丰富的底栖牛物化石成为我国主要泥盆系参考剖面之一.独山剖面弗拉期的石燕贝类腕足动物至少包括5种类型,其中4种在本文中为首次描述和图示.Conispirifer之前只发现于欧洲及北美的弗拉期地层中,目前也首次在华南独山剖面的同期地层中发现.大多先前从贵州南部其他地区弗拉期地层中描述的多种Cyrtospirifer可归于Cyrtospirifer subextensoides新种内.鉴于前人对Emanuella的模式种E.takwanensis 的内部构造描述的矛盾状况,本文暂把研究区具有抬离壳面的纤细铰窝、固着于壳面的主突起以及其前方下面为外铰板支撑的标本归于E.takwanensis.在华南弗拉期可初步识别出三个腕足动物群组合带:Yocrarhynchus-Phlogoiderhynchus动物群以小嘴贝类-无洞贝类-双腔贝类腕足动物为特征,其时代大致从弗拉阶底部至Pa.punctata带;之后为Cyrtospirifer动物群,以Cyrtospirifer的存在为特征,又可分为早晚两部分,前者(未命名)以conispiriferid类的Conispirifer和Pyramidaspirifer、弓石燕类、无洞贝类等为特征,其时代大致为Pa.\"hassi\"带至下Pa.rhenana带;后者为Hunanotoechia动物群,以丰富的小嘴贝类-无洞贝类.弓石燕类腕足动物为特征,其时代大致为上Pa.rhenana带至Pa.1inguiformis带.     

New Upper Devonian brachiopod genus <Emphasis Type="Italic">Paraimbrexia</Emphasis> (Order Spiriferida) from the Abyshevo Horizon of the Kuznetsk Basin

A new spiriferid genus Paraimbrexia with the type species Imbrexia topkensis Besnossova, 1959 is established within the family Imbrexiidae Carter, 1992 from the Abyshevo Horizon, Famennian, Upper Devonian of the Kuznetsk Basin. Revision of the type material of I. topkensis revealed that this species strongly differs from the other species of Imbrexia Nalivkin, 1937 in details of shell exterior and interior.     

A late Devonian (Frasnian) coral-bafflestone reef at Houshan in Guilin, South China

Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian, stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids, receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China with regard to the biotic composition. The reef is composed of fasciculate colonies ofSmithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The species ofSmithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control:Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereasSmithiphyllum occidentale Sorauf, 1972 andSmithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like coral colonies baffled sediments. Algae and stromatoporoids (mainlyStachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods. The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies, reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef but a coral patch reef located near the inner margin of a carbonate platform.     

Transitional reef-to-basin facies of Lower Frasnian limestones determined by microfacies analysis (Wietrznia,Holy Cross Mts,Poland)

Wietrznia section is situated between the shallow-water carbonate platform in the Kielce region and the Łysogóry basin. The transitional facies of the Wietrznia Frasnian includes two overlapping types of deposits: (1) thin-bedded dark-coloured limestone-marl alternations similar to the basin facies and (2) coarse-grained detrital limestones. Three lithotypes of limestones were identified: laminated or graded micritic, nodular, and detrital. The petrographic study makes it possible for the recognition of six major microfacies (MF 1 to MF 6). These lithotypes were formed by redeposition in a low- to high-energy environment. Their source material was the stromatoporoid-coral Dyminy reef in the central part of the Kielce region. Storms are considered to be the main agent, which causes in erosion and transport; micritic limestones and distal tempestites occur together, whereas detrital limestones are associated with proximal tempestites. Most probably, part of the detrital beds was formed as a result of grain-flow initiated under storm conditions.     

Late Middle to Late Frasnian Atrypida, Pentamerida, and Terebratulida (Brachiopoda) from the Namur-Dinant Basin (Belgium)

In the Namur-Dinant Basin (Belgium), the last Atrypida and Pentamerida originate from the top of the Upper Palmatolepis rhenana Zone (Late Frasnian). Within this biozone, their representatives belong to the genera Costatrypa, Desquamatia (Desquamatia), Radiatrypa, Spinatrypa (Spinatrypa), Spinatrypina (Spinatrypina?), Spinatrypina (Exatrypa), Waiotrypa, Iowatrypa and Metabolipa. No representative of these orders occurs within the Palmatolepis linguiformis Zone. The disappearance of the last pentamerids, mostly confined to reefal ecosystems, is clearly related to the end of the edification of the carbonate mounds; it precedes shortly the atrypid one. This event, resulting from a transgressive episode, which induces a progressive and dramatic deterioration of the oxygenation conditions, takes place firstly in the most distal zones of the Namur-Dinant Basin (southern border of the Dinant Synclinorium; Lower P. rhenana Zone). It is only recorded within the Upper P. rhenana Zone in the Philippeville Anticlinorium, the Vesdre area, and the northern flank of the Dinant Synclinorium. It would seem that the terebratulids were absent during the Famennian in this basin, probably due to inappropriate facies. Among the 13 species described or briefly discussed (Palmatolepis hassi to Upper P. rhenana zones), Pseudoatrypa godefroidi nov. sp. and Spinatrypina (Exatrypa) marmoris nov. sp. are proposed as new.