New perspectives on the Mesozoic seed fern order Corystospermales based on attached organs from the Triassic of Antarctica

A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.     

中国狸藻属校订

本文对中国狸藻属分类群进行全面修订, 记载17种和1亚种, 其中8种为中国分布新记录, 1亚种为新等级。     

The corystosperm pollen organ Pteruchus from the Triassic of antarctica

The permineralized corystosperm pollen organ Pteruchus is described from the early Middle Triassic of Antarctica. Pteruchus fremouwensis consists of an axis bearing numerous, helically arranged microsporophylls, each of which terminates in a distal flattened head. The axis is 1–2 mm in diameter and eustelic. Spherical to elliptical secretory cavities are present in the ground tissue of the axis, microsporophyll, and pollen sac wall. The basal stalk of the microsporophyll is vascularized by a C-shaped strand that gives rise to a midvein and numerous lateral veins in the distal head. At least 38 pollen sacs are borne on the abaxial surface of the microsporophyll head. These are arranged in pairs on either side of lateral veins. Each pollen sac is sessile, elongated, and uniloculate. The pollen sac wall is several cell layers thick early in ontogeny, but reduced to a single layer in thickness when mature. Dehiscence is longitudinal along the inner surface. Pollen is monosulcate and bisaccate, and of the Alisporites-type. The Triassic specimens are the first structurally preserved pollen organs of the Pteruchus-type and can be related to the associated corystosperm stem and leaf genera based on the presence of unique secretory cavities. The morphology of Pteruchus and the relationship of this pollen organ with other Mesozoic and Paleozoic pollen organs is discussed.     

Axial nature of the cupule-bearing organ in Caytoniales

Caytoniales are an important group of seed plants, and the nature of their female reproductive organ may influence interpretations of the seed plant phylogeny and the origin of angiosperms. Although not convincingly demonstrated by clear evidence, cupules on previously described specimens were interpreted as being distichously arranged, implying that the cupule-bearing organ in Caytoniales was a pinnate megasporophyll. Here a female reproductive organ of Paracaytonia hongtaoi gen. et sp. nov. (Caytoniales) is reported from Liaoning, China. The well preserved specimen clearly shows a spiral arrangement of cupules along the reproductive axis, suggesting that the cupule-bearing organ in Caytoniales is not a megasporophyll but a branch. This new information on the axial nature of the cupule-bearing organ in Caytoniales has significant implications on the placement of Caytoniales in the seed plant phylogeny and interpretation of the relationship between Caytoniales and angiosperms.     

Morphological architecture of Actinocephalus (Koern.) Sano (Eriocaulaceae-Poales)

Actinocephalus exhibits perhaps more diversity in habit than any other genus of Eriocaulaceae. This variation is largely a result of differences in the arrangement of the paraclades. Based on the analysis of stem architecture of all 25 species of Actinocephalus, the following patterns were established: (1) leaf rosette, with no elongated axis, instead the axillary paraclades originating directly from the short aerial stem, (2) rosette axis continuing into an elongated axis with spirally arranged paraclades, (3) an elongated axis originating from a rhizome, with ramified paraclades, and (4) an elongated axis originating from a short aerial stem, with paraclades arranged in a subwhorl. The elongated axis exhibits indeterminate growth only in pattern 4. Patterns 3 and 4 are found exclusively in Actinocephalus; pattern 1 occurs in many other genera of Eriocaulaceae, while pattern 2 is also found in Syngonanthus and Paepalanthus. Anatomically, each stem structure (i.e., paraclade, elongated axis, short aerial stem, rhizome) is thickened in a distinctive way and this can be used to distinguish them. Specifically, elongated axes and paraclades lack thickening, thickening of short aerial stems results from the primary thickening meristem and/or the secondary thickening meristem. Thickening of rhizomes results from the activity of the primary thickening meristem.     

Behavioural adaptations of the fiddler crabs Uca vocans borealis (crane) and Uca lactea lactea (De Haan) for coexistence on an intertidal shore

The distribution and coexistence of the fiddler crabs U. vocans borealis and U. lactea lactea was investigated in the upper shore of a sandy beach with respect to particle size, water content and total organic carbon content of the sediments. A clear segregation of habitats between the two species was apparent. U. lactea lactea were only found in sediments with significantly lower total organic carbon content. U. lactea lactea had a higher ratio for the size of third maxilliped to body size than U. vocans borealis. There was no statistical difference in the median sediment particle size of the habitats where both species were found on the study shore. U. lactea lactea was larger on shores where U. vocans borealis were absent. Smaller U. vocans borealis individuals occupied sediments with higher water content and finer particles. Smaller individuals of U. vocans borealis also possessed fewer spoon-tipped setae on second maxilliped than their larger conspecifics, which were found mostly on coarser sediments. U. lactea lactea spent significantly more time on the surface than in the burrow during low tide when compared with U. vocans borealis. Both Uca species exhibited similar desiccation resistance. U. lactea lactea tends to keep its frontal region in close contact with sediments to maintain moisture when being exposed to air.     

Nucleotide sequence and organization of full length human U4 RNA pseudogenes

Two loci encoding human U4 RNA, designated U4/7 and U4/14, have been isolated and sequenced. Both are pseudogenes in that their sequences do not match any identified human U4 RNA species perfectly. The U4/7 locus harbours a full-length pseudogene of 144 bp with eight base substitutions in the structural region. This pseudogene might be derived from a hitherto unidentified human U4 RNA gene. The second locus, U4/14, has a complex structure; the structural sequence of a U4 gene has apparently been integrated into an Alu sequence.     

Two new species of the pinnate microsporophyll Pramelreuthia from the upper Triassic of the southwestern United States

Two new species of the enigmatic gymnosperm microsporophyll Pramelreuthia, found in the Upper Triassic Chinle Formation at five localities in the southwestern United States, provide significant new evidence on key morphological characters of the genus and extend its known geographical range. These new fossils also demonstrate that the genus was polytypic and reveal the plant megafossil sources for several common and geographically widespread dispersed Upper Triassic microfossil taxa. The genus Pramelreuthia, which until this study was known only from a single specimen from the Upper Triassic of Austria, is a planar pinnate structure consisting of a slender naked axis bearing stalked synangia in opposite to subopposite pairs. Synangia of all three species of Pramelreuthia are oval to subrectangular in lateral view and are composed of two adpressed flattened valves each of which contains up to 20 or more elongate, subcylindrical, tapered sporangia that bear nonstriate bisaccate pollen. Pramelreuthia yazzi sp. nov. is slightly smaller than the type species P. haberfelneri, and its synangia contain pollen generally similar in morphology and size to several species of the dispersed pollen taxon Pityosporites, including P. chinleana, P. oldhamensis, and P. devolvens. Pramelreuthia dubielii sp. nov. is much larger than the other two species; its synangia contain pollen similar to the dispersed pollen species Protodiploxypinus americus.     

Allelopathic effects of Ulva lactuca on selected species of harmful bloom-forming microalgae in laboratory cultures

Allelopathic effects of the green macroalgae Ulva lactuca on the growth of three species of red tide microalgae, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema costatum were tested in laboratory co-cultures precluding the nutrient and light limitation and the effect of high pH. The growth of all three species of microalgae was significantly (p < 0.01) inhibited by fresh U. lactuca. In nutrient replete semicontinuous co-cultures with U. lactuca, H. akashiwo was completely dead in 12 days, and the growth of A. tamarense and S. costatum was reduced by 48 and 46%, respectively by U. lactuca within 12 days. The U. lactuca culture filtrate exhibited a significant (p < 0.05) inhibitory effect on the microalgae in the first 1 or 2 days, but growth resumed in the following days, and S. costatum growth was slightly (p > 0.05) promoted from day 3. The results suggested that the allelopathic compounds are quickly degradable and a long-term inhibition might need the continuous addition of compounds originated from macroalgae. Dried U. lactuca also exhibited inhibitory effects on the microalgae, and the normalized mean growth rates of microalgae decreased with the biomass of dried U. lactuca. The dependent relationships were y = −2.1208x² + 1.0159x + 0.9752 for H. akashiwo, y = 0.7133x² − 3.5813x + 1.1665 for A. tamarense, and y = −0.2114x² − 1.063x + 1.0873 for S. costatum, respectively. The potential feasibility of utilization of dried U. lactuca against red tide microalgae was 2.0 g dry wt L⁻¹. The present study shows that U. lactuca exhibits negative allelopathic effects on harmful bloom-forming microalgae.     

Pourtalesiid sea urchins (Echinodermata: Echinoidea) of the northern Mid-Atlantic Ridge

Five species of deep-sea pourtalesiid echinoids were collected by the RV G.O. Sars MAR-ECO expedition to the northern part of the Mid-Atlantic Ridge: Solenocystis imitans new genus, new species, Echinosigra phiale (Thomson, 1872), Echinosigra (Echinogutta) fabrefacta Mironov, 1974, and two unidentified species of Pourtalesia. Three types of plastron plating are distinguished within the family Pourtalesiidae; in Solenocystis new genus the plating is similar to that in Spatagocystis, a genus known only from the deep-sea Antarctic. Each of three groups with distinctive plastron plating shows a continuous morphological gradation from a less elongated test without subanal rostrum to an extraordinarily elongated test with large rostrum and wide subanal fasciole; the ratio width/length of test varies from 0.86 to 0.12. Some morphological characters of the pourtalesiids are regarded as adaptations to burrowing and appear to be correlated with test elongation. The family is represented in the northern Atlantic only by 'advanced' genera (Echinosigra, Pourtalesia and Solenocystis) with very elongated tests.     

A new zosterophyll from the Lower Devonian of Wales

A new monotypic genus is described from impression and compression fossils preserved in the Senni Beds of the Lower Old Red Sandstone of S Wales. The new species has scattered reniform lateral sporangia suggesting zosterophyll affinity, but supporting anatomical evidence is lacking. The axes of the plant are characterized by occasional large surface protuberances, sometimes extended into lateral projections of variable length and morphology. Taphonomic factors account for some of the observed features of the fossils, and their unusual orientation in the sediment suggests that Tarella may have grown on exposed point bars.     

Interspecific interactions between the gall-fly Urophora affinis Frfld. (Diptera: Tephritidae) and the weevil Larinus minutus Gyll. (Coleoptera: Curculionidae), two biological control agents released against spotted knapweed, Centaurea stobe L. ssp. micranthos

Interspecific competition has been suggested as an explanation for the failure of some insects as biological control agents for weeds. Enclosure and exclusion cages were used, in southern British Columbia, Canada to evaluate the importance of interspecific competition between a seedhead weevil, Larinus minutus, and a gall-inducing fly, Urophora affinis, two biocontrol agents released against spotted knapweed in North America. At the seedhead scale, U. affinis, which is an inferior biological control agent based on knapweed seed mortality, was the superior competitor. Larinus minutus attack rates were significantly lower in the presence of U. affinis compared to release treatments where L. minutus was attacking alone. Reduced L. minutus attack rates were apparent in seed heads expected to contain both species, assuming insect distributions were random, but instead only contained U. affinis. L. minutus did not significantly affect U. affinis density. Although overall attack rates on knapweed seedheads were higher when both species were together at a site, the consequence of the antagonistic interaction is that overall seed destruction was not as high as it could have been if the weevil were attacking on its own. These results support minimizing the number of biocontrol agents released that use similar resources on the target weed, to avoid negative interactions between control agents and potential reductions in biocontrol efficacy resulting from competitive exclusion.     

Distinguishing angiophytes from the earliest angiosperms: A Lower Cretaceous (Valanginian-Hauterivian) fruit-like reproductive structure

A remarkably diverse Lower Cretaceous (Valanginian-Hauterivian) flora at Apple Bay, Vancouver Island, preserves seed plants at an important time of floristic evolutionary transition, about the same time as the earliest flowering plant megafossils. The fossils are permineralized in carbonate concretions and include tetrahedral seeds within cupule- or carpel-like structures. These enclosing structures, composed of elongate sclerenchyma cells with spiral thickenings that grade externally to a few layers of parenchyma, are vascularized by one collateral vascular bundle and lack trichomes. They apparently broke open to release the tightly enclosed seeds by valves. Seeds are similar to those of the Triassic seed fern Petriellaea, but are about 100 million years younger and differ in size, vascularization, integumentary anatomy, seed attachment, and number of seeds/cupule. These new seeds are described as Doylea tetrahedrasperma gen. et sp. nov., tentatively assigned to Corystospermales. Inverted cupules are reminiscent of an outer angiosperm integument rather than a carpel. Like fruits, cupules opened to release seeds at maturity, thereby foretelling several aspects of angiospermy. They show that nearly total ovule enclosure, a level of organization approaching angiospermy, was achieved by advanced seed ferns during the Mesozoic.     

Liverwort fossils from the Late Triassic of Baiyin City,Gansu Province,and their geological significance

Although liverworts are widely distributed around the world with a large number of extant species, reliable fossil records are relatively rare. Here, we report a new species, Ricciopsis baojishanensis Han and Yan, n. sp. (Ricciaceae) and an unnamed species, Hepaticites sp. from the Late Triassic Nanying’er Formation in Baojishan Basin, Baiyin City, Gansu Province, Northwest China. The generic designation is based on detailed comparison of the gross morphology with related fossil and extant species. The new species is characterized by its rosette-forming thallus, dichotomous branching, ribbon-like segments and entire margins. The current fossils represent the first record of liverwort from the Late Triassic in Baojishan Basin, Gansu Province. Based on the different fossil records of the Ricciaceae, we suggest that these taxa were widely distributed during Late Triassic to Oligocene worldwide, mainly in warm temperate and tropical environments, similar with their current distribution. The discovery of the present fossils indicates that the climate of Baojishan Basin in Late Triassic is warmer and more humid than that of today.     

枸杞岛海藻场6种大型海藻光合荧光特性比较

海藻光合荧光特性研究对分析藻类光合作用和固碳能力具有重要的作用.利用水下调制荧光仪(DIVING-PAM)测定了枸杞岛后头湾夏季常见6种大型海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜的量子产量、快速光曲线(RLC)相关参数.结果显示: 6种常见海藻孔石莼、斯氏刚毛藻、舌状蜈蚣藻、鼠尾藻、多管藻和羊栖菜最大量子产量(F_v/F_m)分别为0.702、0.704、0.457、0.618、0.421、0.567,各物种的开放PSⅡ反应中心原初光能捕获效率(F_v′/F_m′)的大小依次是斯氏刚毛藻>孔石莼>鼠尾藻>羊栖菜>舌状蜈蚣藻>多管藻,且孔石莼、斯氏刚毛藻、羊栖菜的F_v′/F_m′与其他5种大型海藻的差异均达到显著水平;在快速光响应曲线中,羊栖菜、鼠尾藻和孔石莼的最大相对电子传递速率与初始斜率α较高,证明其具有较强的光合能力和捕光能力;舌状蜈蚣藻较高的RLC初始斜率α和较低的I_k表明其有较强的耐弱光能力.3种门类大型海藻之间光合特性有较为显著的差异,其中褐藻门的羊栖菜、鼠尾藻与绿藻门的孔石莼拥有极高的光合活性和抗强光能力,研究结果可为藻场保护工作和大型海藻固碳能力评估提供理论依据.     

The effects of capture spiral composition and orb-web orientation on prey interception

Cribellar prey capture threads found in primitive, horizontal orb-webs reflect more light, including ultraviolet wavelengths, than viscous threads found in more derived, vertical orb-webs. Low web visibility and vertical orientation are each thought to increase prey interception and may represent key innovations that contributed to the greater diversity of modern, araneoid orb-weaving spiders. This study compares prey interception rates of cribellate orb-webs constructed by Uloborus glomosus (Uloboridae) with viscous orb-webs constructed by Leucauge venusta (Tetragnathidae) and Micrathena gracilis (Araneidae). We placed sectors of cribellar and viscous threads side by side in frames that were oriented either horizontally or vertically. The webs of both U. glomosus and L. venusta intercepted more prey when vertically oriented. In each orientation L. venusta webs intercepted more insects than did U. glomosus. Although this is consistent with the greater visibility of cribellar threads, the more closely spaced capture spirals of L. venusta may have contributed to this difference. Micrathena gracilis webs intercepted more prey than did U. glomosus webs, although web orientation did not affect the performance of this araneoid species. The stickier and more closely spaced capture spirals of M. gracilis may have enhanced the interception rates of this species and accounted for the greater number of smaller dipterans retained in its webs. The tendency for these slow, weak flight insects to be blown into both horizontal and vertical webs may account for similar interception rates of horizontal and vertical M. gracilis webs. These observations support the enhanced prey interception of vertically oriented orb-webs, but offer only qualified support for the contributions of lower visibility viscous capture threads.     

Chlorophycean algae from the Triassic of Australia

Among living green algae assigned to the order Chlorococcales and order Zygnematales certain species develop resistant outer organic walls and/or cysts during their life cycles; as such they have the potential to become fossils. Based on morphology, comparison between living algae and microfossil remains are made with varying degrees of confidence, and a possible evolutionary pathway for certain chlorococcalean coenobial families is suggested. Twelve genera are reviewed from earliest to latest Triassic palynological assemblages from northwestern Australia; and the following taxa are described as new: Plaesiodictyon mosellanum ssp. symmetricum ssp. nov.; Plaesiodictyon mosellanum ssp. variabile ssp. nov.; Plaesiodictyon decussatus sp. nov.; Plaesiodictyon decussatus ssp. decussatus ssp. nov.; Plaesiodictyon decussatus ssp. tetracornuta ssp. nov.; Tetraporina protrusa sp. nov.; Crucigeniella? torques sp. nov.; and Paleoraphidia akestra gen. et sp. nov. (type). Their suggested natural affinities are useful in palaeoenvironmental interpretations of mostly freshwater or low-salinity habitats.     

Metric and morphological study of the upper cervical spine from the Sima de los Huesos site (Sierra de Atapuerca, Burgos, Spain)

In this article, the upper cervical spine remains recovered from the Sima de los Huesos (SH) middle Pleistocene site in the Sierra de Atapuerca (Burgos, Spain) are described and analyzed. To date, this site has yielded more than 5000 human fossils belonging to a minimum of 28 individuals of the species Homo heidelbergensis. At least eleven individuals are represented by the upper cervical (C1 and C2) specimens: six adults and five subadults, one of which could represent an adolescent individual. The most complete adult vertebrae (three atlases and three axes) are described, measured, and compared with other fossil hominins and modern humans. These six specimens are associated with one another and represent three individuals. In addition, one of these sets of cervical vertebrae is associated with Cranium 5 (Individual XXI) from the site. The metric analysis demonstrates that the Sima de los Huesos atlases and axes are metrically more similar to Neandertals than to our modern human comparative sample. The SH atlases share with Neandertals a sagittally elongated canal. The most remarkable feature of the SH (and Neandertal) axes is that they are craniocaudally low and mediolaterally wide compared to our modern male sample. Morphologically, the SH sample shares with Neandertals a higher frequency of caudally projected anterior atlas arch, which could reflect greater development of the longus colli muscle. In other features, such as the frequency of weakly developed tubercles for the attachment of the transverse ligament of the atlas, the Sima de los Huesos fossils show intermediate frequencies between our modern comparative samples and the Neandertals, which could represent the primitive condition. Our results are consistent with the previous phylogenetic interpretation of H. heidelbergensis as an exclusively European species, ancestral only to H. neanderthalensis.