New Ordovician ostracodes from Himalaya and their palaeobiological and palaeogeographical implications

Silicified representatives of the ostracode orders Binodicopa, Palaeocopa and Podocopa have been recovered from the late Ordovician Pin Formation, Spiti, NW Himalaya area. Benthic binodicopes are distinctly more abundant than the palaeocope and podocope ostracodes. The binodicopes show biogeographical relations to Australia at the generic level, which supports the close palaeogeographic position of these continents. By contrast, the palaeocope and podocope taxa show close relations to Baltica and Bohemia even at the species level, which may suggest a pelagic or epipelagic mode of life since these regions are separated from each other by the broad and deep waters of Palaeotethys. New taxa are Vendona crassiplicata nov. sp., Glossomorphites himalayaensis nov. sp., Pilla pinensis nov. sp. and Pinpilla u-formis nov. gen. nov. sp.     

Pseudoplanktonic lifestyle of the Triassic crinoid Traumatocrinus from Southwest China

Colonies of Traumatocrinus (Echinodermata, Crinoidea) attached to driftwood from the lower Upper Triassic (Carnian) Xiaowa Formation of the Guanling area (Guizhou, Southwest China) document a pseudoplanktonic lifestyle for this specialized offshoot of the otherwise benthic Middle Triassic Encrinidae. After the end-Carnian decline of Traumatocrinus, its ecological niche was subsumed in Norian by genera derived from another benthic family (Holocrinidae) with convergent morphological modifications. After the Toarcian (Lower Jurassic), this niche disappeared, possibly due to the emergence of wood-boring bivalves.     

The root of the problem: palaeoecology of distinctive crinoid attachment structures from the Silurian (Wenlock) of Gotland

The holdfast (attachment structure) is the most understudied aspect of the palaeoecology of the endoskeleton of fossil crinoids. A new collection of well-preserved holdfasts from a recently reopened quarry at Hunninge, Gotland, in Homerian (upper Wenlock) strata includes several morphologies. The most common are terminal dendritic radicular holdfasts (TDRHs) that may be derived from the cladid Ennallocrinus d'Orbigny. These have a consistent morphology of five, equally spaced, long radices that spread across the sea floor. These crinoids were gregarious, and TDRHs in a group commonly show the same radice orientations. The radices have a large axial canal compared with those of modern crinoids; each included, at least, nervous tissues. Taken together, these features suggest that, apart from attachment, these distinctive TDRHs may have served a sensory function. Other holdfasts in this assemblage also show monospecific aggregations, perhaps suggesting biochemical attraction such as that shown by certain other sessile invertebrates such as barnacles.     

Changes in the lanthanum distribution following decapitation of the sporophytes of an aquatic fern,Marsilea drummondii A. Br.

Summary The active terminal bud and the quiescent lateral buds and corresponding nodes inserted at different levels on the main rhizome ofMarsilea drummondii were examined with the EM afterin vivo feeding with lanthanum nitrate. These tracer experiments demonstrate that all the buds are fed by their phloem cells. In the lateral bud axis the labelling of the sieve elements apoplast indicates that a solute transfer took place in the node between xylem and phloem via xylem transfer cells. La³⁺ deposits are completely absent from the apical dome of inhibited buds indicating that the walls of the quiescent meristematic cells are not permeated by the tracer. The removal of the terminal bud has two effects. It rapidly (in 2 hours) allows the lanthanum to penetrate the lateral bud tip walls at a stage when no fine structural changes are discernable and to bind to the outer surface of the plasmalemma as it does in the active terminal bud. This study including inhibited buds and buds released from apical dominance support the view that changes in the state of the cell surface (cell wall and plasma membrane) may be a prerequisite for the resumption growth activity.This study was supported in part by a grant from the Centre National de la Recherche Scientifique to L.Sossountzov (AI 031275).     

Unusual tabulate‐crinoid biocoenosis from the Lower Devonian of Morocco

The Early Devonian (Pragian: sulcatus to pireneae conodont zones) crinoid–coral biocoenosis from Hamar Laghdad, Morocco contains fragments of crinoid stalks of various taxa encrusted by spherical and ellipsoidal coralla of the tabulate coral Hamarilopora minima. These corals were encrusting host crinoids syn vivo, and this is evidenced by pluricolumnals exceeding 30 elements overgrown from all sides. Most known to date crinoid–epibiont associations display various types of reaction to the epibiont, such as swellings and deformations. In the case discussed here, no clear interaction is visible; therefore, this association can be classified as paroecia. It can be inferred, however, that due to a change in mechanical properties of the crinoid stalk (losing flexibility), the epizoan influence on the host was negative, while the coral was profiting from the elevated position over the seafloor and nutrient‐bearing water currents. It can be supposed that this interaction was close to parasitism. No strict species‐specific relationship between the epizoan and the host was observed.     

Biotic diachroneity during the Ordovician Radiation: evidence from South China

The Ordovician radiation was one of the most marked and sustained increases in Phanerozoic biodiversification; nevertheless it occurred against a background of minimal global climatic and environmental perturbations. Detailed investigations of the Ordovician successions on the Yangtze Platform of the South China palaeoplate indicate that: (1) the brachiopod α- and β-diversity changes are diachronous; (2) macroevolutionary patterns were different across the South China palaeoplate, with the Early Ordovician brachiopod radiation first occurring in normal marine, shallow-water environments and then moving gradually to both nearer-shore and offshore locations; (3) the main contributors to the initial Ordovician brachiopod radiation were the Orthida and Pentamerida; the typical Ordovician brachiopod fauna, dominated by the Orthida and Strophomenida, did not appear until the late Mid Ordovician (Undulograptus austrodentatus Biozone) when the Strophomenida apparently replaced the dominant position of the Pentamerida within the fauna; (4) different ecotypes (e.g., sessile benthos, mobile benthos together with pelagic and planktonic organisms) demonstrate substantially different macroevolutionary patterns. The Ordovician brachiopod radiation of South China was apparently earlier than that suggested by global trends together with the data available from other palaeoplates or terranes, which may be related to its unique palaeogeographic position (peri-Gondwanan terrane gradually moving to equatorial latitudes).     

Radial perforations in crinoid stems from the Silurian of Gotland

Radiating intracolumnal canals are a characteristic feature of large (diameter 10 mm or more) crinoid stems from the Silurian of Gotland. They are found in nodals as well as in internodals where the columnal height exceeds one millimetre. They were formed secondarily in the median and distal portions of crinoid stems with pseudocirriferous holdfasts. Intercolumnal canals are found in the distal parts of stems with true cirri regardless of the size of the stem. It is suggested that these canals played an important role in crinoid physiology. The crinoids are believed to have sustained a large proportion of their tissues through cutaneous digestion and uptake of dissolved substances from the surrounding sea water. The intra- and intercolumnal canals increased the surface of the axial canal in relation to volume. They provided a connection between the axial canal and the surrounding sea water, thus facilitating nutrient transport to the tissues.     

Functional morphology of synarthrial articulations in the crinoid stem

Synarthrial fulcral ridges are found in crinoid columnals from the mid-Ordovician to the present and in all four subclasses. Similar articulations did not become common in the cirri until the Mesozoic. Synarthrial stem articulations fall into two broad groups. Type I articulations have a fulcral ridge in the centre of the articular facet. In elliptical ossicles this ridge corresponds to either the long (IA) or short (IB) axis of the facet. Although both are functionally similar, Type IA ossicles are more common. Type II articulations have an excentric fulcral ridge, parallel to either the long (IIA) or short (IIB) axis of the articular facet. Type IIA articulations are found in crinoid stems capable of coiling. Type II articulations are particularly common in the cirri of articulates and are well adapted for attachment to hard and soft substrates. Columnals with Type I articulations often have divergent fulcra, giving the stem flexibility in all directions, but this feature is not seen in cirri or in coiled stems, where it would impair normal functions. Only the cirri of isocrinids and comatulids are muscular, so the movement of columns with fulcra must be passive.     

Disarticulation patterns in Ordovician crinoids: Implications for the evolutionary history of connective tissue in the Crinoidea

Taphonomic information is examined to evaluate the early history of connective tissues in the Crinoidea. The pattern of stalk segmentation of Middle and Late Ordovician crinoids is consistent with the two-ligament (intercolumnal and through-going ligaments) pattern present in living isocrinid crinoids and interpreted for fossil isocrinids, holocrinids, and Lower Mississippian crinoids. A single rhombiferan was also examined; its taphonomic pattern is also indicative of this style of tissue organization. Furthermore, the taphonomy of all Middle and Late Ordovician crinoids may reflect that they lacked discretely organized muscles between arm brachials, which is consistent with the hypothesis that muscles evolved as a connective tissue between plates only once within the Crinoidea, during the Early Devonian. These data indicate that the two-ligament organization of the stalk is a primitive feature among the Crinoidea and perhaps even among stalked echinoderms. Therefore, the autotomy function of this column-tissue organization among living crinoids is an exaptation. On the other hand, discretely organized muscles as connective tissue in crinoid arms is a derived trait that first appeared during the middle Paleozoic; this adaptation proved very successful for the advanced cladid crinoids.     

打顶对烟草生长、钾素吸收及其分配的影响

与不打顶相比,打顶并未增加烟株最终的干物质及K累积量,但由于消除了顶端对有机物质及K的强烈竞争,使无谓消耗于顶中的1／3的同化物及K运向其它器官,从而使叶片中累积的同化物及K由不打顶时的1／3左右提高到1／2左右,有利于同化产物及K在叶内的累积;此外打顶不了根对同化产物的竞争能力,因而要系发达、烟叶产量及其含K量显著增加,打顶后用NAA处理茎断口并不能提高烟叶产量,但烟株有烟叶内K的最终累积量增加,因此与公打顶相比可明显提高生育后期叶片K含量。     

Ordovician meteoric carbon and oxygen isotopic values: implications for the latitudinal variations of ancient stable isotopic values

Columnar and clear blocky calcite cement from a Middle Ordovician carbonate succession in east Tennessee is interpreted as meteoric in origin. Columnar and clear blocky calcite from this succession does not show extremely large ¹³C depletions reported from meteoric phases of younger rocks. Meteoric fluid δ¹⁸O values calculated from clear blocky calcite are 2 to 3‰ more negative than approximately coeval sea water; a relationship typical of modern, low-latitude, coastal meteoric water. Comparison with meteoric δ¹⁸O values from Ordovician units elsewhere suggests that the geographic distribution of these values may be broadly similar to that observed today. Therefore, we tentatively suggest that geographic distribution of meteoric δ¹⁸O values during both icehouse and greenhouse eras are similar.     

The biological affinity of Amsassia: new evidence from the Ordovician of North China

Amsassia shaanxiensis sp. nov. occurs in the Middle Ordovician part of the Jinghe Formation in Yongshou and the lower part of the Upper Ordovician Beiguoshan Formation in Longxian, Shaanxi Province, north‐central China. In addition to module increase by bipartite longitudinal fission, which is also known in other species of Amsassia, tripartite and rare quadripartite fission are recognized in A. shaanxiensis. All species previously assigned to Lichenaria from the Middle to Upper Ordovician of Shaanxi probably belong to Amsassia. Therefore, Amsassia, rather than the tabulate coral Lichenaria, should be credited as an important contributor to reef‐building in this area. Reports of Lichenaria from elsewhere in the North China Platform require confirmation in the light of the present study. Some morphological characteristics of Amsassia are comparable to those of tabulate corals, tetradiids and chaetetid sponges. Consequently, various authors have assigned Amsassia to the Lichenariida, Tetradiida (now Prismostylales; florideophycean rhodophyte algae) and Chaetetida. Other important characters, however, seem to exclude Amsassia from those taxonomic groups. The phacelocerioid organization of modules having separate walls would not be expected in sponges. The basic symmetry of individuals may have been radial, unlike the tetramerous symmetry of tetradiids. Module increase by longitudinal fission, involving infoldings of the wall, is fundamentally different from modes of increase in corals, tetradiids and chaetetids. The skeleton was probably aragonitic, whereas that of tabulates was calcitic. The affinity of Amsassia remains unresolved, but it is unlikely to have been a coral, tetradiid or sponge. Perhaps, like the tetradiids, Amsassia was an alga.     

Visceral regeneration in the crinoid Antedon mediterranea: basic mechanisms, tissues and cells involved in gut regrowth

Crinoids are able to regenerate completely many body parts, namely arms, pinnules, cirri, and also viscera, including the whole gut, lost after self-induced or traumatic mutilations. In contrast to the regenerative processes related to external appendages, those related to internal organs have been poorly investigated. In order to provide a comprehensive view of these processes, and of their main events, timing and mechanisms, the present work is exploring visceral regeneration in the feather star Antedon meditteranea. The histological and cellular aspects of visceral regeneration were monitored at predetermined times (from 24 hours to 3 weeks post evisceration) using microscopy and immunocytochemistry. The overall regeneration process can be divided into three main phases, leading in 3 weeks to the reconstruction of a complete functional gut. After a brief wound healing phase, new tissues and organs develop as a result of extensive cell migration and transdifferentiation. The cells involved in these processes are mainly coelothelial cells, which after trans-differentiating into progenitor cells form clusters of enterocytic precursors. The advanced phase is then characterized by the growth and differentiation of the gut rudiment. In general, our results confirm the striking potential for repair (wound healing) and regeneration displayed by crinoids at the organ, tissue and cellular levels.     

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。     

Island benthic assemblages: With examples from the Late Ordovician of Eastern Australia

The Benthic Assemblage (B.A.) concept, developed by A.J. Boucot two decades ago principally for continental marine margins, is extended to offshore island settings. Characteristics of modern island biotas, including ecological displacement, and the effects of r and K selection, can be identified in Late Ordovician volcanic islands of central New South Wales. Two variants of B.A.1 are represented, a quiet‐water lingulide biofacies, and a rough‐water rhynchonellide biofacies. The quiet‐water Eodinobolus biofacies occupied a B.A.1–2 position, onshore of and sheltered by a Tetradium wave‐baffle (B.A.2). The offshore shelfal high diversity strophomenide biofacies is equivalent to B.A.3. Remnants of periplatformal B.A.4–5 communities are recognised in allochthonous limestone breccias which were displaced downslope into graptolitic B.A.6 sediments. Steeper offshore gradients, typical of islands, laterally compress the B.A. profiles, and also contribute to downslope slumping. Ecological displacement in island environments results in extension of the habitat range of species into adjacent B.A.s. Reefs complicate the usual B.A. profile by introducing distinct sheltered and turbulent water environments. These characteristics may have applicability in interpretation of islands throughout the Palaeozoic record.     

A new aglaspidid arthropod from the Lower Ordovician of Wales

A new genus and species of aglaspidid arthropod, Tremaglaspis unite , is described from the well-known upper Tremadoc locality of Y Garth in North Wales, and compared with other Cambrian and Ordovician taxa. It is remarkable in having a large hypostome, a character shared with other primitive arachnomorphs.     

Cyrtocrinids (Crinoidea) and associated stalked crinoids from the Lower/Middle Oxfordian (Upper Jurassic) shelfal deposits of southern Poland

Five cyrtocrinid crinoid taxa previously unknown from the epicratonic deposits of Poland, as well as associated millericrinids and isocrinids, are described. The studied materials were derived mainly from the Lower and Middle Oxfordian, but crinoids are also from uppermost Callovian and/or lowermost Oxfordian sediments of the Polish Jura Chain (southern Poland). The crinoids, preserved as more or less complete (e.g., basal circlets) cups, include Lonchocrinus dumortieri, Phyllocrinus belbekensis, Remisovicrinus polonicus, Remisovicrinus aff. polonicus, Tetracrinus moniliformis and Sclerocrinus sp. The occurrence of Remisovicrinus polonicus in the late Middle Oxfordian of the southern Poland is confirmed. Moreover, the present study extends the geographic range of all cyrtocrinid species studied and discusses their unusual environmental adaptations.     

Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco

Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.     

Skeletal variation in the early clathrodictyid stromatoporoids of Upper Ordovician and its paleoecological and phylogenetic implications

This study reports four species belonging to two genera of clathrodictyid stromatoporoids from the Sanqushan Formation (Katian, Upper Ordovician), Changshan County, Zhejiang Province, East China: Clathrodictyon cf. mammillatum (Schmidt), C. plicatum Webby and Banks, C. cf. microundulatum Nestor and Labyrinthodictyon cascum (Webby and Morris). Of these, three species (C. cf. mammillatum, C. plicatum and L. cascum) show a wide range of skeletal variation, representing the variation from the normal skeletal phase to abnormal Ecclimadictyon-like crumpled skeletal phase, especially in the axial part of the columnar growth forms. It is uncertain whether the skeletal variation in early clathrodictyids was the result of environmental stress (such as abrupt sediment influxes that often cause growth interruptions of the stromatoporoids) or genetic inheritance. These characteristics suggest that this group had greater environmental tolerance than the earlier labechiids and increased ecological complexity during Late Ordovician by providing a stable, solid and elevated substrate for the other benthic organisms. This may imply that the labechiids and clathrodictyids are quite different groups, probably independently derived during the early evolution of stromatoporoids.     

Latest Helcionelloid Molluscs from the Lower Ordovician of Kazakhstan

The helcionelloid mollusc Chuiliella elenae gen. et sp. nov. is described from the Lower Ordovician of Kazakhstan. It represents the geologically youngest record of a group of mainly bilaterally symmetrical ancient molluscs which originated in the earliest Cambrian, flourished during the early–mid Cambrian and was thought to have become extinct during the late Cambrian. Chuiliella is a typical helcionelloid in terms of shell shape, although the comarginal ornamentation characteristic of many helcionelloids is lacking. Interpretation of the raised margin of the aperture adjacent to the earlier coiled whorl as exhalant channels favours reconstruction of helcionelloids as endogastrically coiled, i.e., with the apex posterior.