Substrate specific associations of epebionts on Middle Devonian brachiopods: Implications for paleoecology

A detailed study of over 2500 host brachiopods, from the Middle Devonian Hamilton Group of New York State, revealed distinct patterns of epibiont encrustation, that provide insight into taphonomy and paleoautecology of the host brachiopod shells and depositional environments. The concavo‐convex orthid, Tropidoleptus carinatus (Conrad), as well as strophomenid, and smooth athyrid brachiopods are among the most heavily encrusted. However, terebratulids of nearly identical size and shape are relatively clean of epibionts. This selective distribution strongly suggests that epibionts were discouraged from settling on punctate brachiopods. Brachiopods with small spines and frills were also nearly clean of epibionts, possibly because of entrapment of a mud layer, which made the outer layer of the host inhospitable for larval settling. Concavo‐convex taxa reveal high percent coverage and diversity of epibionts on the convex valve, which probably rested on the substrate during the life of brachiopod. This pattern is observed even on brachiopods that were buried with the convex valve downward. This implies complex post‐mortem histories involving multiple episodes of reorientation and colonization.     

The development of growth lines on articulate brachiopods

Three types of growth lines are recognised on articulate brachiopod shells: (1) very fine diurnal growth lines formed by calcite increments at the shell margin, (2) seasonal growth lines, formed by inward reflection (doubling back) of the mantle edge, seen as concentric steps on the shell surface and marked by re-orientation of growth vectors evidenced by secondary shell fibres, (3) disturbance lines, formed by abrupt regression of the mantle edge, also seen as concentric steps on the shell surface, but indicated by a dislocation in the shell fabric. Lamellose and spinose ornaments of the sort seen in Tegulorhynchia are essentially genetically controlled. Periodic outgrowths from the outer mantle lobe secrete frills of primary shell that project from the shell surface and form short hollow spines where they cross the radial ornament. In longitudinal section spine formation is seen to involve gradual increase in the rate of secretion of primary shell followed by retraction, and often collapse, of the mantle outgrowth, accompanied by regression. Reflection of the mantle edge usually follows spine formation.     

广西六景剖面艾菲尔—吉维特阶界线层的腕足动物化石

广西六景剖面民塘组底部艾菲尔-吉维特阶界线层的腕足类,是一个台地边缘相和盆地相之间过渡环境中的非近岸底栖型腕足动物群.该动物群以贝体小,属种分异度较高,缺乏明显的地方性分子为特征,石燕贝类占有明显的优势,具背中隔板类型的正形贝类发育,并有鸮头贝科的分子出现.Echinocoelia, Davidsonia 和 Pentamerella 是本腕足动物群的优势属群;其他重要分子有 Skenidioides, Vallomyonia, Leptathyris, Rhynchospirifer, Warrenella 和 Stringocephalus.文中描述腕足类17属19种,其中4新种: Vallomyonia sinensis sp. nov., Pentamerella nanningensis sp. nov., Davidsonia guangsiensis sp. nov., Echinocoelia guangsiensis sp. nov..     

Lower Devonian Chonetoidean Brachiopods From Bac Bo, North Viêt Nam

Recent investigations of the Lower Devonian fauna of North Viêt Nam have provided abundant invertebrates, among which chonetoidean brachiopods are especially common. Their good preservation has allowed the revision of eight of the nine species described in the literature. The North Vietnamese chonetoidean fauna is mainly characterized by the diversity of representatives of the Family Strophochonetidae (strophochonetines and parachonetines), which includes nine species. Three new genera, namely TulynetesBacbonetesCyrtochonetes, and two species, namely Bacbonetes janvieriChlupacina nariensis, are described. The occurrence of Perichonetes mirabilisChlupacina nariensis, and plicanoplitid brachiopods establishes the extension of the south-west China pelagic Nandan Facies to eastern Bac Bo. The Lower Devonian chonetoidean fauna of eastern Bac Bo is closely allied to that of south-west and central China belonging to the Yangtzé microcontinent, whilst the fauna of western Bac Bo appears to be more closely allied with that of the northern Gondwanaland margin. One new additional chonetoidean genus, Orthochonetes, is described in a note added to the systematic section.     

Taxonomical and biostratigraphical remarks on the rhynchonellide “Paurorhyncha” (Brachiopoda) in the Yidade Formation of eastern Yunnan,China

Additional specimens of rhynchonellide brachiopods from the marly limestones in the Yidade Formation at the Panxi section in eastern Yunnan have been ascribed to the species “Paurorhyncha” squamosa Wang, 1956 and “P.” depressa Wang, 1956. The two species have been used frequently as index fossils for the Frasnian (Upper Devonian), but their taxonomic assignments are problematic because their internal structures remain unknown. In this study, detailed systematical examinations on both external characters and internal structures revealed by serial sections suggest that the two species are more appropriately assigned to the genus Hadrotatorhynchus Sartenaer, 1986. Based on the stratigraphical distributions of Hadrotatorhynchus and the conodonts in the upper unit of the Yidade Formation, the Hadrotatorhynchus-bearing horizons are re-considered as the uppermost Givetian (Middle Devonian) rather than Frasnian stage, although the precise position of the Middle/Upper Devonian boundary still depends on further investigations of high-resolution biostratigraphy.     

New Devonian brachiopods from northeastern Russia

Brachiopods from the Devonian of northeastern Russia are described: Eoprokopia gen. nov., with the type species E. aequalis sp. nov. (subfamily Prokopiinae, order Orthida); Davoustia settedabanica sp. nov. and D. verkhojanica sp. nov. (family Anopliidae, order Chonetida); and Alkhovikovia gen. nov. with the type species A. libera sp. nov. and A. importuna sp. nov. and Tikhyspirifer gen. nov. with the type species T. globosus sp. nov. (subfamily Rhynchospiriferinae, order Spiriferida).     

Orthid brachiopods from the Lower and Middle Devonian of northeastern Russia

Brachiopods of the order Orthida from the Lower and Middle Devonian of northeastern Russia: Skenidium diversus Baranov (family Skenidiidae); Datnia gen. nov., with the type species D. asiatica sp. nov. (subfamily Prokopiinae); Janzhinshinia gen. nov., with the type species J. datnensis sp. nov. (subfamily Isorthinae); Cortezorthis chobotchalensis (Alekseeva) (subfamily Cortezorthinae); Elenia gen. nov., with the type species E. gerensis sp. nov. (family Dicoelosiidae); Seimtchania communis (family Seimtchaniidae); Simakovia gen. nov., with the type species S. rara sp. nov. (family Draboviidae); Schizophoria distenta sp. nov., S. grande Baranov, S. striatula (Schlotheim) (family Schizophoriinae); and Hypsomionia sinsera Baranov (family Hypsomioniidae) are described.     

Description of the early ontogenic part of the Tentaculitids, with implications for classification

Ontogenic development and classification of tentaculitids at high systematic levels are reevaluated in the light of new findings on shell structure and morphology of larval parts, and these features are here regarded as being of primary importance for taxonomy. Class Tentaculita Bouček, 1964 is subdivided into two subclasses, of which subclass Chionioconarida Farsan, 1994 is distinguished by a tubular larval process closed at the apex and covered with microrings. The process is differentiated into a prolarval, metalarval and epilarval part, of which the latter coincides with metamorphosis. Morphology of the larval parts suggests that metamorphosis proceeds in two different manners, giving rise to superorders within this subclass. Within superorder Trompetoconarida Farsan, 1994 a bilaterally symmetrical larval cone develops with an aperture oblique to the long axis of the conch; following metamorphosis the conch becomes radially symmetrical and the aperture perpendicular to the axis; secondary shell, septa and pseudopunctae develop in the adult phase, and the structure of the shell is lamellar. In contrast, within the second superorder, Lirioconarida Farsan, 1994 the epilarval tube develops into a larval bulb with no changes in symmetry and position of the aperture; secondary shell, septa and pseudopuncta are absent. The microstructure of the shell is lamellar in the larval part whereas in postlarval parts it is either sigmoidal or lamellar. The subclass Dacryoconarida Fisher, 1962 possesses a subspherical, tear- or drop-like embryonic chamber which may have a caudal process. The microstructure of the embryonic chamber is variable within this group, being lamellar in some taxa whereas in others, a single layer of shell is present. The postembryonic parts of the lamellar forms possess nacreous or sigmoidal structures.     

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.     

Provenance Of Atlantic Lingulid Brachiopods

Living lingulid brachiopods are ubiquitous in low-latitude, marine infaunas. Lingula occurs throughout the Pacific and Indian oceans with the only Atlantic species, L. parva, confined to West Africa. Glottidia is restricted to offshore America from Virginia to California and Peru, and is assumed to have descended from a Pacific Lingula during the early Tertiary. Lingulid organophosphatic shells differ structurally. That of Glottidia is characterizedby trellised rods (baculate); that of Indo-Pacific species of Lingula by spheroidal and rod-like microstructures (virgose); and that of L. parva by apatitic rods arranged as spherulites. A spherulitic fabric is unknown in fossil lingulids, but the distinction between GlottidiaLingula can be traced back to the Carboniferous, which accords with the deep molecular divergence between the two genera. The common occurrence of lingulids with baculate shells in European post-Palaeozoic sediments suggests that ancestral Glottidia entered the Atlantic by the Tethyan Current during the Late Cretaceous/early Cenozoic, and migrated into the Pacific before the formation of the Panama Isthmus. Penecontemporaneously, antecedents of L. parva possibly migrated from east Tethys along the trans-Saharan seaway.     

Discussion of the Early Devonian rhynchonellid brachiopod genus Borealirhynchia Su, 1976

The Early Devonian brachiopod genus Borealirhynchia was established by Su, 1976. Phylum Brachiopoda (Cambrian to Devonian). In: Paleontological Atlas of North China, Inner Mongolia Volume 1. Geological Publishing House Beijing, pp. 155-227 (in Chinese). It has not been previously described in detail, nor have transverse serial sections of the internal features of Borealirhynchia delerensis, the type species, been published. In this paper Borealirhynchia, along with a few species previously assigned to it, is analysed and discussed. Detailed transverse serial sections of the internal features of B.? lata Su, 1976, are provided, based on well-preserved specimens collected from the Lower Devonian strata of Dong Ujimqin Qi, northeastern Inner Mongolia. Borealirhynchia? gigantea Su, 1976 and Latonotoechia multicosta Su, 1976 are considered to be synonyms of B.? lata Su with the same external and internal characters present in all three species. Some Lower Devonian strata, in which Borealirhynchia was found and reported, from Dong Ujimqin Qi, northeastern Inner Mongolia, are fully described.     

湘中泥盆系弗拉阶顶部腕足动物种群统计及其古生态学意义*

基于大量不同生长阶段的标本,本文绘制华南湘中蒋家桥剖面C1-0和佘田桥剖面S-Y-4两个样品共10种小型腕足动物的种群结构和生存曲线,结果显示,C1-0动物群内没有一种腕足类的大小-频率分布呈典型的正常钟型分布模式,仅Thomasaria?baii,Thomasaria?liangi,Xiangia liaoi,Cyrtinaella?houi及Gypidula xui的直方图有些类似钟型分布,而Qidongia tani,Athyris supervittata及Levipugnax?liui的直方图则呈明显的右斜型***分布。各种群生存曲线表现为不同程度的下凹型,这可能与它们生活在泥质软基底的环境有关。Thomasaria?baii为浅凹型,Levipugnax?liui,Xiangia liaoi,Gypidula xui,Qidongia tani及Cyrtinaella?houi为中凹型,Athyris supervittata及Thomasaria?liangi呈深凹型;依次反映的是更高的幼年期死亡率,之后死亡率持续降低的特点,而上述大小-频率分布和生存曲线型式的差异则可能反映了不同种类对环境条件适应程度的差异,例如不同的壳形可能导致的应对软基底及取食效率的区别。对蒋家桥剖面Iowatrypapseudobodini和佘田桥剖面Hunanotoechia tieni块体采样及手捡采样两种不同方法的结果对比表明,采样方法可以不同程度地影响腕足动物种群的大小-频率分布及生存曲线。为了获得最接近真实情况的生存曲线,工作中应尽量采用两种方法相结合。     

New Lower Devonian brachiopods of the family Reticulariidae Waagen (order Spiriferida) of northeastern Russia

New Lower Devonian brachiopod taxa of the family Reticulariidae (order Spiriferida) are described from northeastern Russia: Havlicekospirifer gen. nov. with the type species H. mirabilis sp. nov. (subfamily Reticulariinae) and Pavlovispirifer gen. nov. with the type species P. pelagicus sp. nov. (subfamily Rhenothyridinae).     

桂东仁义剖面吉维特阶上部的牙形石及腕足动物*

本文报道了在桂东仁义剖面中上泥盆统巴漆组中一段八十余米厚地层中发现的牙形石3属10种(包括亚种)和腕足动物16属17种(包括属种未定类型).根据牙形石的组合分布,识别出Schmidtognathus hermanni带、Polygnathus cristatus带和Klapperina disparilis带上亚带,表...