The multiovulate cupule of a new spermatophyte, Thorezia vezerensisgen. et sp. nov., is described from the Late Devonian aged sediments from Trooz Quarry in Belgium. In gross morphology, it conforms to the Moresnetia morphotype and has a cupule that is composed of four independent quarters that each dichotomises three times. Each cupule quarter contains one single ovoid preovule with a long pedicel and an integument that has small apical teeth surrounding a rudimentary micropyle. Morphological variability in the materials examined is interpreted as being related to preovule maturity, and from this a good understanding of the ontogenetic development from preceding dispersal has been developed. Up to now, 17 spermatophyte species have been described, 11 of which come from eastern Laurussia. This diversity in eastern Laurussia contrasts strongly with the low diversity characterizing contemporaneous floras from other phytogeographical areas. We suggest here that the arid climatic conditions prevailing in eastern Laurussia favoured the development of diverse spermatophyte communities and contributed to reduced diversity and abundance of contemporaneous free-sporing plant diversity. 相似文献
A large permineralized calamitean stem, Arthropitys yunnanensis Tian et Gu from the Upper Permian of southwest China is reinvestigated and interpreted. The stem has a broad pith and well
developed and large carinal canals. Secondary xylem is thick and characterized by wide parenchymatous interfascicular zones
that remain constant in width throughout the wood. Striking features of the stem include the abundant leaf traces arranged
in two whorls in the cortex with this arrangement previously unrecognized within calamitean stems, and the presence of growth
rings in secondary xylem that suggest frequent fluctuations in environmental stress presumably due to variations in water
availability. Features of A. yunnanensis infer the stem to be in the epidogenetical phase of calamitean development, and suggest it to be the basal part of a large
trunk. Comparisons with biomechanical models for calamitean stems suggest this species had a semi-self supporting habit. 相似文献
In order to study the relative roles of receptors in the upper airways, lungs and systemic circulation in modulating the ventilatory
response of caiman (Caiman latirostris) to inhaled CO2, gas mixtures of varying concentrations of CO2 were administered to animals breathing through an intact respiratory system, via a tracheal cannula by-passing the upper
airways (before and after vagotomy), or via a cannula delivering gas to the upper airways alone. While increasing levels of
hypercarbia led to a progressive increase in tidal volume in animals with intact respiratory systems (Series I), breathing
frequency did not change until the CO2 level reached 7%, at which time it decreased. Despite this, at the higher levels of hypercarbia, the net effect was a large
and progressive increase in total ventilation. There were no associated changes in heart rate or arterial blood pressure.
On return to air, there was an immediate change in breathing pattern; breathing frequency increased above air-breathing values,
roughly to the same maximum level regardless of the level of CO2 the animal had been previously breathing, and tidal volume returned rapidly toward resting (baseline) values. Total ventilation
slowly returned to air breathing values. Administration of CO2 via different routes indicated that inhaled CO2 acted at both upper airway and pulmonary CO2-sensitive receptors to modify breathing pattern without inhibiting breathing overall. Our data suggest that in caiman, high
levels of inspired CO2 promote slow, deep breathing. This will decrease dead-space ventilation and may reduce stratification in the saccular portions
of the lung. 相似文献
The fragmentary remains of a juvenile rhabdodontid ornithopod from the Coal-bearing Complex of the Gosau Group (Lower Campanian, Grünbach syncline) at Muthmannsdorf near Wiener Neustadt, Lower Austria are revised. The material, probably belonging to a single individual, includes a right dentary (lectotype of Iguanodon suessi Bunzel, 1871, designated herein), teeth, a fragmentary parietal, fragments of scapula, ?radius, femur, tibia, two vertebrae (lost) and a manual ungual.The lectotype dentary does not provide clear autapomorphies or sufficient diagnostic features to determine its position within the Rhabdodontidae at generic level. By this “Iguanodon suessi” Bunzel, 1871 and the genus “Mochlodon” Seeley, 1881, to which it was latter referred as type species, cannot be characterized sufficiently by differential diagnosis and these are best considered nomina dubia. Based upon combined character comparisons (mainly postcranial features) the Muthmannsdorf ornithopod is referred herein to Zalmoxes Weishampel, Jianu, Csiki and Norman, 2003, a genus so far known from the late Maastrichtian of Romania. It probably but not evidently represents a yet unnamed species, most closely related to Zalmoxes shqiperorum Weishampel, Jianu, Csiki and Norman, 2003. At the present state of knowledge the Austrian material is not further diagnostic at the species level and kept in open nomenclature as Zalmoxes sp. 相似文献
Transition tasks between static and dynamic situations may challenge head stabilization and balance in older individuals. The study was designed to investigate differences between young and older women in the upper body motion during the voluntary task of gait initiation. Seven young (25 ± 2.3 years) and seven older healthy women (78 ± 3.4 years) were required to stand on a force platform and initiate walking at their self-selected preferred speed. Angles of head, neck and trunk were measured by motion analysis in the sagittal plane and a cross-correlation analysis was performed on segments pairs. Variability of head and neck angular displacements, as indicated by average standard deviation, was significantly greater in the older than in the young participants. The young women maintained dynamic stability of the upper body, as forward flexion of the trunk was consistently counteracted by coordinated head–neck extension. Differently, movement patterns employed by the older women also included a rigid motion of all upper body segments leaning forward as a single unit. These results demonstrated that older women perform the transition from standing to walking with greater variability in the patterns of upper body motion compared to young women. 相似文献
The Upper Ordovician (late Whiterockian to Mohawkian) Lourdes Formation represents a narrow (tens of kilometers), short-lived
[∼5–7 million years (my)], open-ocean (high-energy) mixed siliciclastic-carbonate ramp that onlapped allochthonous strata
along the orogen side of the local Taconic foreland basin. Platform development followed a 6–8 my hiatus during which weathering
had concentrated chemically mature siliciclastics that were admixed with initial carbonate sediments. A cross-platform facies
gradient contains paleokarst and peritidal carbonates and sandstones, shallow-ramp carbonate bioherms and skeletal shoals,
and deeper ramp calcareous shales. Transgressive systems tracts are marked by ramp-wide sheets and shoals of skeletal grainstone
and low accumulation rates, and highstand systems tracts are marked by significant admixture and interbedding of siliciclastics
with cross-ramp carbonate facies. Platform demise coincides with increased siliciclastic input, which is likely tectonically
influenced. The Lourdes platform is equivalent to epicontinental foreland ramps along eastern Laurentia, but its narrower
width precluded formation of oceanographically restricted platform-interior facies. 相似文献
The technology of modern humans is unique in the animal kingdom with respect to its complexity and capacity for innovation. Evidence of technological complexity and creativity in the archeological record is broadly coincident with and presumably related to traces of creativity in art, music, ritual, and other forms of symbolism. The pattern of modern human technology is part of a larger package of behavior (sometimes referred to as “behavioral modernity”) that emerges with the appearance of industries in Eurasia classified as Upper Paleolithic, but has deeper roots in the African Middle Stone Age. 1 - 5 . 相似文献
In the area of Piz Corvatsch (Upper Engadin, Grisons, Switzerland), the actual vegetation on active and inactive rock glacier surfaces has been mapped. The floristic composition (vascular plants and lichens) of the different rock glacier surfaces has been mapped and compared with photogrammetrical measurements of surface movements of the active rock glaciers. In general, the active rock glacier surfaces show a very low cover of vascular plants. Most of them are located at the edge and at the front of the rock glacier where fine-grained soil material occurs in small pokkets.
Lichenometry has been used as an additional method on Murtèl rock glacier and on the protalus rampart. Measurements of Rhizocarpon geographicum thalli revealed increasing sizes from the root zone of the rock glacier to its front. On the Murtèl rock glacier, Rhizocarpon geographicum thalli with a diameter >4cm occur on surfaces with ages between 5000 and 6000 years B.P.
The statistical analysis (MULVA-5) of the dense vegetation cover of the inactive and relict rock glaciers revealed four plant sociological groups, which are composed of species reflecting well consolidated sites: alpine grassland, subalpine dwarf shrubs and small patches with single small trees of Swiss stone pine (Pinus cembra) and larch (Larix decidua). 相似文献