A new species of psammosteiform heterostracan (Agnatha) from the Givetian (Middle Devonian) of the Voronezh Region

A new pycnosteid species, Schizosteus shkurlatensis sp. nov. (Agnatha, Psammosteiformes), from the Staryi Oskol beds (Givetian, Middle Devonian) of the Voronezh Region is described. This is the first species of the genus Schizosteus Obruchev from the Central Devonian Field. The similarity between species of this genus and early species of Psammolepis is discussed.     

Devonian antiarchs (Pisces,Antiarchi) from central and Southern European Russia

Antiarchi (Pisces, Placodermi) from the Devonian of central and southern European Russia (Central Devonian Field) are studied. Antiarchs belong to three families, the Asterolepididae, Remigolepididae (suborder Asterolepidoidei), and Bothriolepididae (suborder Bothriolepidoidei). The diagnoses of the order, two suborders, three families, and five genera (two of which are new) are given. Sixteen species, including one new, are described; ten taxa are determined in open nomenclature. Morphological structures of representatives of these families are considered in detail. Classifications of antiarchs and their position in the system of the lower vertebrates are discussed. Devonian vertebrate localities of central and southern European Russia that have yielded antiarchs are listed. Each locality is characterized by its ichthyoassemblage.     

Microconchid tubeworms across the upper Frasnian – lower Famennian interval in the Central Devonian Field,Russia

Abstract: Microconchid tubeworms (Tentaculita) encrusting brachiopod shells have been investigated from the upper Frasnian – lower Famennian (Upper Devonian) deposits of the Central Devonian Field, Russia. The condition of microconchids and associated encrusting taxa is reported for the first time from the early Famennian recovery interval (crepida Chron) following the Frasnian–Famennian mass extinction. Two species, one new (Palaeoconchus variabilis sp. nov.) and the second one in open nomenclature (Palaeoconchus sp.), are described. Compared to lower Famennian specimens, they seem to be preferentially grouped on the anterior parts of the brachiopod host shells, which are interpreted as the most suitable sites away from the sea‐bottom and sediment. During the late Frasnian (Late rhenana Chron), microconchids, outnumbered by cornulitids and as abundant as foraminifers, were also associated with trepostome bryozoans, tabulates, rugose corals and various problematic encrusters. During the early Famennian recovery interval encompassing the crepida Chron, microconchids greatly outnumbered all associated encrusters, including the previously dominant cornulitids, while foraminifers, tabulates and rugose corals vanished. Early Famennian microconchids, represented by the single, albeit very abundant, species Palaeoconchus variabilis sp. nov., were opportunists that rapidly colonised the environment during the ongoing transgression following the regression‐driven biotic crisis in the area of the Central Devonian Field. In comparison to their late Frasnian predecessors and even other Middle Devonian specimens, no size reduction (the so‐called Lilliput effect) of early Famennian microconchid tubes was observed. It is probable that microconchids either rapidly attained their ‘normal’ sizes or they did not suffer any dwarfism following the Frasnian–Famennian event.     

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.     

A new species of Laccognathus (Porolepiform Crossopterygii) from the Devonian of Latvia

A new species of the genus Laccognathus, L. grossi sp. nov., from the upper strata of the Gauja Formation of the Main Devonian Field (Lode locality, Latvia) is established. Morphological similarity and differences of the new species from the previously described L. panderi Gross from the lower strata of the Gauja and the Amata Formation of Latvia are discussed.     

欧洲和北非发现的一种华南中泥盆世腕足动物Intermedites Struve,1995(英文)

在北非和欧洲中西部中泥盆世地层中发现的石燕类属Intermedites被认为是从早泥盆世腕足动物属Arduspirifer演化而来,二者具有相同的地理分布。将Intermedites与来自欧洲和亚洲(华南和越南)的无窗贝型石燕类属进行详细比较,发现Intermedites应该源于华南的某种类群,如Rostrospirifer和Otospirifer,分支分析也支持这一解释。文中还对相关属进行基于系统切片的三维复原,清楚地显示了这些属在形态上的相似性与差异性。自泥盆纪埃姆斯晚期华南石燕类腕足动物向西迁移,进一步证实了早泥盆世期间华南腕足动物土著性的丧失。     

The oldest Gondwanan cephalopod mandibles (Hangenberg Black Shale,Late Devonian) and the mid‐Palaeozoic rise of jaws

It is widely accepted that the effects of global sea‐level changes at the transition from the Devonian to the Carboniferous are recorded in deposits on the shelf of northern Gondwana. These latest Devonian strata had been thought to be poor in fossils due to the Hangenberg mass extinction. In the Ma'der (eastern Anti‐Atlas), however, the Hangenberg Black Shale claystones (latest Famennian) are rich in exceptionally preserved fossils displaying the remains of non‐mineralized structures. The diversity in animal species of these strata is, however, low. Remarkably, the organic‐rich claystones have yielded abundant remains of Ammonoidea preserved with their jaws, both in situ and isolated. This is important because previously, the jaws of only one of the main Devonian ammonoid clades had been found (Frasnian Gephuroceratina). Here, we describe four types of jaws of which two could be assigned confidently to the Order Clymeniida and to the Suborder Tornoceratina. These findings imply that chitinous normal‐type jaws were likely to have already been present at the origin of the whole clade Ammonoidea, i.e. in the early Emsian (or earlier). Vertebrate jaws evolved prior to the Early Devonian origin of ammonoids. The temporal succession of evolutionary events suggests that it could have been the indirect positive selection pressure towards strong (and thus preservable) jaws since defensive structures of potential prey animals would otherwise have made them inaccessible to jawless predators in the course of the mid‐Palaeozoic marine revolution. In this respect, our findings reflect the macroecological changes that occurred in the Devonian. [Correction added on 28 July 2016 after first online publication: In the Abstract, the sentence “Vertebrate jaws probably … in the Early Devonian” was amended]     

Devonian floral assemblages and plant megafossils from the Iberian Peninsula: A review

This paper presents a review and critical analysis of the literature on Devonian floras of the Iberian Peninsula. Although the known outcrops of Devonian strata in the Iberian Peninsula are marine, in some cases, a few fragmentary remains of vascular plants are associated with faunal remains. Records include largely specimens from the Lower Devonian of Barrancos (Alentejo, Portugal) and the Upper Devonian of Sierra de Hornachos in Badajoz province, southwest Spain; the remainder consists of drifted plant fragments from scattered sites in the Iberian Peninsula ranging in age from Lochkovian to Upper Devonian-Earliest Carboniferous. The vegetation inferred for the Lower Devonian of the Iberian Peninsula is mainly based on palynological data and corresponds to herbaceous types characterised by bryophytes, rhyniophytes (Horneophyton, Cooksonia, Rhynia), trimerophytes (Psilophyton, Pertica and Hostinella), primitive lycophytes (Drepanophycus) and incertae sedis such as Nothia and Chaleuria, all flora that developed near the coast in low-lying and, at least periodically, wet areas. In the Middle Devonian, two vegetation strata can be recognised: herbaceous (Psilophyton) and semi-arboreal (Cladoxylales). Although three levels of vegetation in the Upper Devonian, have been described from outcrops worldwide, the scarce available data from the Iberian Peninsula only indicate an arborescent lycopsid vegetation and species with uncertain botanical affinity such as Sphenopteridium keilhauii Nathorst.     

Geological and geochemical aspects of a Devonian siliceous succession in northern Thailand: Implications for the opening of the Paleo-Tethys

The opening of the Paleo-Tethys are reconstructed, including the depositional setting and redox conditions, based on an analysis of radiolarian fossils and the geochemistry of a Devonian siliceous succession in the Chiang Dao area of northern Thailand. The succession is subdivided into the following five rock types (in ascending stratigraphic order): black shale (Lower Devonian), siliceous shale (Middle Devonian), tuffaceous chert and tuff (Middle/Upper Devonian), and chert (Upper Devonian). The succession was deposited in continental margin and pelagic environments between the Sibumasu Block and the Indochina-North China blocks. The concentrations of terrestrial-derived elements (Al₂O₃, TiO₂, Rb, and Zr) suggest that the succession (except for the chert) was supplied with terrigenous material and volcanic ash from the adjacent continent, deposited within a SiO₂-rich environment. Geochemical indicators of redox conditions (total organic carbon and the Th/U ratio) reveal a gradual change from anoxic to oxic oceanic conditions between the black shale and chert. Taking into account the interpreted depositional setting and redox conditions, the initial Paleo-Tethys developed as a small, closed anoxic-suboxic oceanic basin during the Early to Middle Devonian, located close to the continental margin. Black shale and siliceous shale were deposited in the basin at this time. Opening of the Paleo-Tethys started around the Middle and Upper Devonian boundary, marked by voluminous volcanic activity. The tuffaceous chert was deposited under oxic conditions, suggesting that ash and pumice within the chert were derived from a continental source. After the Late Devonian, the Paleo-Tethys developed as a deep, broad ocean in which pelagic chert was deposited.     

Investigating Devonian trees as geo‐engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology

We present the rationale for a cross‐disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca²⁺ to the oceans and, ultimately, a 90% decline in atmospheric CO₂ levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca‐phosphate dissolution mineral weathering. This suggests co‐evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long‐standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree‐sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.     

Devonian tetrapod trackways and trackmakers; a review of the fossils and footprints

The earliest tetrapods are known from the Upper Devonian. Their remains are becoming better known from increasing numbers of specimens, localities, environments and ichnofossils. Each of the eight (or possibly nine) genera now represented by skeletal fossils is reviewed in its sedimentological, faunal and stratigraphic context, with an assessment of what might be inferred about the habitus and locomotory capabilities of each. Fossil trackways and their interpretations are then re-examined in the context of the known body forms, and consideration given to the degree of fit between the skeletal fossils, the trackways and their interpretations. The currently known Devonian tetrapods are unlikely to have made any of the known tracks, unless they were produced under water. Neither the skeletal fossils nor the trackways show good evidence of terrestrial locomotion among Devonian tetrapods. When the fossil material and recent phylogenetic analyses are taken in combination, it appears that neither tetrapods nor limbs with digits are likely to have arisen before the Frasnian. This should be borne in mind in palaeoecological studies of these animals.     

Middle and Early Upper Devonian Miospore Zonations in Eastern Yunnan and the Significance of Their Stratigraphy

The Devonian marine and non marine deposits were widely distributed in East Yunnan, where rich marine faunas and floras were present. The Middle and early Upper Devonian miospores of Eastern Yunnan were also abundant and usually well- preserved. The present paper provides both analysis of qualitative and quantitative composition development of Middle and early Upper Devonian spore assemblage in Eastern Yunnan, and a palynological zonatlon containing four successive assemblage zones: 1.Zone of Calyptosporites velatus-Rhabdosporites langii (VL); 2. Zone of Archaeozonotriletes variabilis-Calyptosporites proteus (VP); 3. Zone of Geminospora lemurata-Cristatisporites triangulatus (LT); 4. Zone of Archaeoperisaccus ovalis-Lagenicula bullosum (OB). The Middle and early Upper Devonian spore assemblages of Eastern Yunnan may be compared with those in South China and West Qinling. The spore zonation possesses stratigraphical dating of the Devonian megafloras of the region, particularly those from the Middle and Upper Devonian. The proposed spore zonation is closely compared with that erected for the Middle and early Upper Devonian of Old Sandstone Continent and adjacent Region. Based on palynological data, the reconstruction of Paleogeography and Paleoecology are discussed.     

中国泥盆纪含鱼化石地层的世界对比

简要回顾泥盆纪含鱼化石地层分层的进展及现状,总结中国泥盆纪含鱼化石地层的层位,横向地比较了主要鱼化石的系统关系,再结合具体的地质历史背景,对比世界有关的地层。     

Schischcatella (Fenestrata,Bryozoa) from the Devonian of the Rhenish Massif,Germany

Abstract: The Devonian fenestrate bryozoan, Schischcatella Waschurova, 1964 , possessed colonies in the form of low, erect bifoliate fronds that grew from an encrusting sheet‐like base with autozooecia arranged in biserial, bifurcating rows. This growth habit is unique in fenestrates, which normally had unilaminate arborescent colonies. Originally, Schischcatella was described from the Lower Devonian of Tajikistan. This article describes a new species, S. heinorum sp. nov., from the Middle Devonian of the Eifel (western Rhenish Massif, Germany) with additional material from the Lower Devonian of the Kellerwald (eastern Rhenish Massif, Germany). External and internal morphologies of this bryozoan have been studied using abundant material. The growth habit of Schischcatella suggests a completely different pattern of feeding currents than that in the normal fenestrate colony. The outflow of the filtered water occurred only on edges of colonies between rami. In the absence of chimneys (areas of vertical water expelling), such a functional morphology may have restricted extension of the colony in a distal direction. The evolution of Schischcatella is apparently an example of paedomorphosis, the genus evolved from an unknown semicosciniid species by the early ontogenetic interruption of colony development and further changes in the mode of growth.     

Biogeography and evolution of bryozoans of the genus <Emphasis Type="Italic">Minussina</Emphasis> Morozova, 1961

The spatial variations of bryozoans of the Devonian genus Minussina throughout its existence are discussed. The areal distribution of Minussina is shown to be restricted mainly to the Altai-Sayan region. The variability of seven morphological characters of Minussina species is analyzed. The variations in the number of acanthozooecia and in the thickness of walls are attributed to evolutionary change; variations in the measurements of apertures and heterozooecia are explained by geographical variation. The narrow stratigraphic range of Minussina species makes it possible to use them for correlation of Devonian deposits.     

The braincase and palate of the tetrapodomorph sarcopterygian mandageria fairfaxi: morphological variability near the fish–tetrapod transition

The braincase of the Late Devonian tristichopterid sarcopterygian Mandageria fairfaxi , from Canowindra, NSW, Australia, differs radically from the conservative pattern present in other 'osteolepiforms' (stem–group tetrapodomorph fishes) and non–dipnoan sarcopterygian fishes in general. The basioccipital region is short, displaced anteriorly, and either unossified or loosely articulated to the exoccipital, leaving most or all of the notochordal tunnel open ventrally. The exoccipital complex, which is developed into a large saddle that would have rested on top of the notochord, carries large, triangular articular facets on its posterior face and appears to have formed part of a functional neck joint, a synovial articulation between the skull and vertebral column that allows the former to rotate against the latter. Such a joint is characteristic of post–Devonian tetrapods, but unknown in other sarcopterygians. We infer that the ventrally open notochordal tunnel allowed gentle flexion of the cranial notochord during (predominantly vertical) rotational movement at the occiput; this is a mechanically unique solution to the problem of creating a mobile neck. Other unusual features of Mandageria include a posteriorly located lateral commissure, and structures on the entopterygoid and lateral commissure that may have been associated with an elaborate spiracular tract.     

Notes on a fertile rhyniophytoid from the Lower Devonian of Guangxi,southwestern China

A fertile rhyniophytoid is discovered from the Lower Devonian of Guangxi, southwestern China, which is characterised by small size, dichotomous branchings and terminal sporangia. This plant is similar to the genus Aberlemnia Gonez et Gerrienne and also, is comparable to some mesofossil morphotypes of early land plants from the Early Devonian (Lochkovian) Old Red Sandstone floras. This study adds new data to the generally zosterophyll-dominated Early Devonian floras of South China and sheds some lights on the palaeophytogeography of rhyniophytoids.