Plenasium xiei sp. nov. from the Cretaceous of Northeast China: Additional evidence for the longevity of osmundaceous ferns

A new species of the Osmundaceae, Plenasium xiei sp. nov., is herein described from the Cretaceous of Northeast China. The specimens examined here represent the earliest unequivocal record of the extant genus Plenasium in Eurasia based on fossil rhizomes. The rhizome consists of a central stem with a mantle of petiole bases and adventitious roots. The stem contains an ectophloic‐dictyoxylic siphonostele and a two‐layered cortex. The C‐shaped leaf trace bears two protoxylem bundles at the point of separation from the stele. The pith is heterogeneous. The parenchymatous inner cortex is thinner than the sclerenchymatous outer cortex. Lobed sclerenchyma bands occur at the adaxial sides of the stem xylem strands, in the concavity of the leaf trace, and along the adaxial side of the vascular bundles of the petiole base. In distal petiole portions, the sclerenchyma band splits into several groups in the transverse view. Sclerenchyma rings are heterogeneous with an abaxial sclerenchymatous arc of thick‐walled fibers. Numerous sclerenchyma strands of thick‐walled fibers appear in the petiolar inner cortex and the stipular wing. These fossils provide unambiguous evidence for the existence of subgenus Plenasium of modern Plenasium by at least the Late Cretaceous, demonstrating the longevity of this extant subgenus. Altogether the leaf and rhizome fossil records of Plenasium indicate that this genus was widely distributed across North America and Eurasia from the Early Cretaceous to the Early Cenozoic, followed by a range restriction to Eurasia in the Late Cenozoic. Extant Plenasium species are only known from East and Southeast Asia.     

A new marsilealean fern species from the Early Cretaceous of Jordan

Leaflets of Marsileaceae are described from the Albian (Early Cretaceous) strata of Jordan. The fossils are from the Jarash Formation (Kurnub Group) and are found in fluvial sediments along with water lily leaves. The small wedge-shaped leaves have dichotomous veins that anastomose and form a marginal vein. Based on comparisons to living genera, Marsileaceaephyllum mahisensis Hu, Taylor, Brenner et Basha, n. sp., is most similar to Marsilea, in particular, with terrestrial leaflet forms; yet, it is distinct from living and fossil species by its small size and the few dichotomously branched middle veins that have a monopodial course. In addition, a single similar-veined smaller leaf with a retuse apex is thought to be a juvenile leaf of the same species. This is the first megafossil evidence of the family from Africa/Arabian Peninsula.     

蕨类植物配子体发育与生理生态研究进展

蕨类植物配子体为单倍体,结构简单,独立于孢子体生活,在研究其对环境的响应以及揭示其机理上都具有独特的优势。该研究从我国和国际两个分支出发,梳理了近年来全球范围内相关的文献资料,透视了蕨类配子体的发育和生理生态前沿科学和研究动态。在发育部分以研究进展为主要内容,国内研究以传统植物蕨类植物的配子体形态和发育的观察为主,而国外学者更关注于新技术和新方法在传统学科中的运用,如X光透射技术和流式细胞术。生理生态部分分为光合与呼吸作用、土壤逆境的响应、气候变化的响应以及对化感物质的响应4个板块。在光合作用的研究中,发现蕨类配子体会在光强的变化下产生自我保护机制,碳水化合物和脂质是配子体能量代谢中的重要指标。在土壤逆境的响应研究中,对砷有超富集作用的蜈蚣草配子体和耐高盐的铁角蕨配子体是配子体研究中较为突出的材料。荷兰地区广泛存在的耳蕨属蕨类,哥斯达黎加热带雨林的20种蕨类植物及水生蕨类槐叶萍,成为了证明配子体成活率和温度之间重要关系的实验例证。在化感作用研究中,主要通过紫茎泽兰根、茎和叶水提液对扇蕨等4种蕨类配子体的作用,证明了入侵植物对于蕨类植物配子体生长发育具有危害作用。在美国佛罗里达的一类爬树蕨也发现了同样的入侵植物现象。此外,还对几个新兴技术在配子体研究的前景进行了展望,并对已有技术进行了描述。该研究以多个角度介绍了国内外配子体的研究进展,希望有助于促进我国学者对该领域的深入研究。     

Fossil isopods associated with a fish skeleton from the Lower Cretaceous of Queensland,Australia – direct evidence of a scavenging lifestyle in Mesozoic Cymothoida

Abstract: A dense assemblage of fossil isopod crustaceans (Brunnaega tomhurleyi Wilson, sp. nov.) from the Lower Cretaceous (Albian) Toolebuc Formation of Queensland, Australia, has been found within the carcass of a large actinopterygian fish, Pachyrhizodus marathonensis (Etheridge). Preservation of fine anatomical details supports referral to the genus Brunnaega Polz, which is herein reassigned to the family Cirolanidae. Furthermore, placement of this taxon within the cirolanid subfamily Conilerinae Kensley and Schotte is significant because the group includes modern species that are well known as voracious scavengers. This isopod–fish association represents the oldest unequivocal evidence of scavenging by Mesozoic cymothoidean isopods on a large vertebrate carcass.     

Fossil evidence for a herbaceous diversification of early eudicot angiosperms during the Early Cretaceous

Eudicot flowering plants comprise roughly 70% of land plant species diversity today, but their early evolution is not well understood. Fossil evidence has been largely restricted to their distinctive tricolpate pollen grains and this has limited our understanding of the ecological strategies that characterized their primary radiation. I describe megafossils of an Early Cretaceous eudicot from the Potomac Group in Maryland and Virginia, USA that are complete enough to allow reconstruction of important life-history traits. I draw on quantitative and qualitative analysis of functional traits, phylogenetic analysis and sedimentological evidence to reconstruct the biology of this extinct species. These plants were small and locally rare but widespread, fast-growing herbs. They had complex leaves and they were colonizers of bright, wet, disturbance-prone habitats. Other early eudicot megafossils appear to be herbaceous rather than woody, suggesting that this habit was characteristic of their primary radiation. A mostly herbaceous initial diversification of eudicots could simultaneously explain the heretofore sparse megafossil record as well as their rapid diversification during the Early Cretaceous because the angiosperm capacity for fast reproduction and fast evolution is best expressed in herbs.     

Fossil angiosperm wood: its role in the reconstruction of biodiversity and palaeoenvironment

Fossil wood is subject to different taphonomic, sampling and recognition biases in the palaeobotanical record when compared with leaves and palynomorphs. Wood therefore provides a systematically independent source of information that can increase our knowledge of past biodiversity and environments. Increase in fossil wood records from Cretaceous and Tertiary sediments helps further the understanding of trends in anatomical specialization through geological time. These data can then be used to distinguish such specialization from anatomical response to environmental change. Two case studies, a Late Cretaceous early Tertian' wood flora from Antarctica and a lower Tertiary w ood flora from southern England, have been used to exemplify the importance of studying the fossil wood component of palaeofloras.     

Light as a hazard for the desiccation-resistant 'resurrection' fern Polypodium polypodioides

Abstract. Using fluorescence measurements at 77 K, the susceptibility to photoinhibition was determined for variously dehydrated leaves of the desiccation–resistant fern Polypodium polypodioides. As expected, water loss increased the potential danger of light-induced damage. However, the long-term consequences of that damage differed depending on the hydration state of the leaves during the light treatment, suggesting that different targets were affected. This became evident when the rehydrated leaves were subjected to conditions conducive to recovery from typical photoinhibition. After an exposure to high photon flux densities, full restoration of normal photochemical efficiencies occurred only when the photoinhibitory treatment had occurred while the leaves were fully hydrated, or when the dehydration had reached a stage at which only the primary charge separation and storage were operative. On the other hand, lesions caused by high light intensities in slightly dehydrated leaves which had retained some electron transport activity between the two photosystems, or in desiccated leaves incapable of any measureable photosynthetic functions, were very inefficiently or not at all repaired. One unexpected hazard of high light intensities for dehydrated leaves turned out to be further desiccation which could reach a threshold at which extensive cellular damage began to ensue. In nature, P. polypodioides avoids light–induced damage by rolling its leaves during dehydration so that only the reflectant abaxial leaf surface is exposed to ambient light, and by occupying shaded habitats.     

The ossified Meckel's cartilage and internal groove in Mesozoic mammaliaforms: implications to origin of the definitive mammalian middle ear

The ossified Meckel's cartilage is described in detail from three adult individuals of two triconodont mammals, Repenomamus and Gobiconodon , which have been discovered in the Lower Cretaceous of Liaoning, China. A possible ossified Meckel's cartilage has also been recognized in the Early Cretaceous symmetrodont Zhangheotherium from Liaoning. The rod-like ossified Meckel's cartilage in Repenomamus bridges the dentary and the ear region of the cranium. Its shape and position are similar to those of Meckel's cartilage in prenatal and in some postnatal extant mammals. The ossified Meckel's cartilage may have functioned as an attachment site for the medial pterygoid muscle. These specimens provide direct evidence for the function of the internal groove which is commonly present in the dentary of early mammals and their relatives. The evidence weakens the hypothesis of multiple origins for the definitive mammalian middle ear. It supports the assumption that a persistent or ossified Meckel's cartilage has been present in adults of the common ancestor of mammals. The new evidence of Repenomamus does not support the model in which brain expansion and negative allometry of the auditory chain are primarily responsible for the detachment of ear ossicles in mammalian ontogeny and evolution. An alternative hypothesis is proposed which does not require brain expansion as the initial factor for the detachment of ear ossicles during mammalian evolution. © 2003 The Linnean Society of London. Zoological Journal of the Linnean Society , 2003, 138 , 431–448.     

Evidence for antheridogen production and its mediation of a mating system in natural populations of fern gametophytes

Gametophytes of Asplenium pimpinellifolium Fee and Lygodium heterodoxum Kze., occurring as natural populations in Veracruz, Mexico, were studied with respect to their spacing, size, and number of antheridia and archegonia. Small gametophytes, 0.3-2.2 mm in width and growing in colonies, usually had high numbers of antheridia. Gametophytes of the same size, growing at least 1 5 cm from the nearest neighbour, had few antheridia. In the colonial gametophytes there was a strong correlation between heavily antheridiate ones and their proximity to large archegoniate gametophytes. The data are the first to suggest the presence of an antheridogen system operating in nature, with concomitant opportunities for cross-fertilization. The rôle of polyploidy in storing genetic variation and the rôle of antheridogen-mediated out-crossing in releasing variation are seen as co-adaptive phenomena in the ferns.     

Korallipteris,a new genus for Mesozoic Gleichenia-like fern fronds

A new morphogenus, Korallipteris, is proposed to accommodate fertile or sterile fern fronds possessing essentially Gleichenia-like morphology (e.g., pinnate fronds with small pecopteroid pinnules) but lacking diagnostic features that allow their classification at fern family-level. The aim is thus, to solve an old nomenclatural problem that involves the use of illegitimate genera, such as Gleichenites Goeppert and Microphyllopteris Arber. Several species of Gleichenites described from the Mesozoic of Argentina and Chile, and Microphyllopteris unisora Cantrill and Nagalingum from Antarctica are here reassigned to Korallipteris gen. nov. The proposal of Nagalingum and Cantrill to preserve Gleicheniaceaephyllum Crabtree emend. Nagalingum and Cantrill for true Gleicheniaceous ferns, diagnosed by having an arrested laminar bud, is here accepted.     

Phylogeny of Osmundaceae Inferred from rbcL Nucleotide Sequences and Comparison to the Fossil Evidences

rbcL sequences of 11 of 15 extant species of Osmundaceae which represent all three genera, Osmunda, Todea and Leptopteris. Our phylogenetic analysis concluded: 1) Osmunda subg. Osmunda and subg. Plenasium are monophyletic groups, but subg. Osmundastrum is not. The genus Osmunda is not monophyletic because Todea and Leptopteris are positioned within Osmunda. 2) Osmunda cinnamomea is the most basally positioned species in Osmundaceae, and it can be called as “a living fossil” because a fossil species (O. claytoniites) with almost the same morphology as this species was recorded from the Triassic. 3) Osmunda japonica and O. regalis are very closely related with only one nucleotide difference in the rbcL gene. 4) Greater nucleotide variation (5–7 nucleotides) was found between conspecific samples of O. cinnamomea and O. claytoniana collected from Japan and United States. Each of these two species may comprise more than two biologically differentiated species. Received 7 July 1999/ Accepted in revised form 25 August 1999     

Diversity, genetic structure and evidence of outcrossing in British populations of the rock fern Adiantum capillus-veneris using microsatellites

Microsatellites were isolated and a marker system was developed in the fern Adiantum capillus-veneris. Polymorphic markers were then used to study the genetic diversity and structure of populations within the UK and Ireland where this species grows at the northern edge of its range, requiring a specific rock habitat and limited to a few scattered populations. Three dinucleotide loci detected a high level of diversity (23 alleles and 28 multilocus genotypes) across the UK and Ireland, with nearly all variation partitioned among rather than within populations. Of 17 populations represented by multiple samples, all except four were monomorphic. Heterozygosity was detected in three populations, all within Glamorgan, Wales (UK), showing evidence of outcrossing. We make inferences on the factors determining the observed levels and patterns of genetic variation and the possible evolutionary history of the populations.     

Fossil evidence of evolutionary convergence in juvenile dental morphology and upper canine replacement in sabertooth carnivores

The convergent suite of morphological traits characterizing the mammalian sabertooth ecomorphology is well documented, including modifications of the dental and osteological portions of the masticatory apparatus from a less‐specialized carnivore condition. Equally important is how those specialized adult morphologies developed through ontogeny because previous studies have shown that growing such specialized craniodental traits may require evolutionary modification of growth patterns and tooth replacement mechanisms. Despite the understanding of convergent morphological specialization in adult sabertooth carnivores, the possibility of a convergent ontogenetic trajectory toward those adult morphologies has not been rigorously examined. The present study examines numerous previously undescribed juvenile nimravid specimens. The results provide insights about nimravid ontogeny and show, for the first time, that the nimravid sabertooth lineage included species in which the permanent upper canine erupted within a lingual concavity of the deciduous upper canine until it reached comparable crown height beyond the alveolar border. Furthermore, this investigation assesses the juvenile morphology and upper canine replacement of felid and barbourofelid sabertooth taxa. The results provide evidence of convergence in deciduous upper canine morphology of three sabertooth carnivore lineages (i.e., nimravid, felid, and barbourofelid), as well as preliminary evidence of convergence in the upper canine replacement process. It might be beneficial for studies of extreme morphological specialization to simultaneously consider convergence in adult morphologies and how morphologies change through ontogeny.     

Fossil floral and fruit evidence for the evolution of unusual developmental characters in Fagales

Flowers of many living Fagales exhibit unusual developmental characteristics. At anthesis, ovulate flowers have carpels bearing immature orthotropous ovules. After pollination, the ovules increase in size and become anatropous and the ovary enlarges. Simultaneously, the pollen tubes extend from the stigma to the ovules with several phases of growth and quiescence. Finally, after the first fertilization, the remaining ovules abort, resulting in a single‐seeded fruit. Three‐dimensionally preserved potentially fagaceous mesofossil flowers from the Campanian of Massachusetts, USA, provide evidence on the evolution of these characters. The fossils share putative synapomorphies with the Fagales (six tepals, mostly inferior, three‐carpellate ovary with each locule initially containing two pendant ovules, punctate‐rugulate, tricolporate pollen and fruit with a single seed). However, the fossil is bisexual and has nectaries, characters shared with the sister order Cucurbitales, and both lack the fagalean immature orthotropous developmental stage. The fossil shares synapomorphies of an inferior ovary and a single‐seeded indehiscent fruit with both living orders and appears to be transitional. Comparison of ontogenetic changes between the fossil and related fagalean taxa suggests independent stepwise changes in development in which some characters of the modern clades were in place at ～ 75 Myr and others evolved more recently. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 353–376.     

Equilibrium sorption isotherm for metal ions on tree fern

A new sorbent system for removing heavy metal ions, such as Zn(II), Cu(II) and Pb(II), from aqueous solutions has been investigated. This new sorbent is tree fern, an agriculture product. Variables of the system include solution temperature and sorbent particle size. The experimental results were fitted to the Langmuir, Freundlich and Redlich–Peterson isotherms to obtain the characteristic parameters of each model. Both the Langmuir and Redlich–Peterson isotherms were found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the maximum sorption capacities of metal ions onto tree fern were 7.58 mg/g for Zn(II), 10.6 mg/g for Cu(II) and 39.8 mg/g for Pb(II). It was noted that an increase in temperature resulted in a higher metal loading per unit weight of the sorbent. Decreasing the particle sizes of tree fern led in an increase in the metal uptake per unit weight of the sorbent.     

Circular arrangement of cortical microtubules around the subapical part of a tip-growing fern protonema

Summary Cortical microtubule arrays in tip-growing protonemal and rhizoid cells of the fernAdiantum gametophytes were observed by immunofluorescence microscopy. A circular arrangement of cortical microtubules was demonstrated around the subapical part of protonemal cells growing under red light conditions. However, such an arrangement was not found in growing rhizoids either by immunofluorescence microscopy or by electron microscopy. The different patterns of microtubule arrays around the apices of tip-growing protonemal and rhizoid cells suggest the possible existence of different mechanisms in regulating the cell diameter in the two types of cylindrical cell.     

A new tree fern stem,Heilongjiangcaulis keshanensis gen. et sp. nov., from the Cretaceous of the Songliao Basin,Northeast China: a representative of early Cyatheaceae

A new genus and species of Cretaceous Cyatheacean tree fern, Heilongjiangcaulis keshanensis gen. et sp. nov., is erected for several permineralized stems collected at the Keshan County in Songliao Basin, Heilongjiang Province, Northeast China. The new taxon is characterized by a dictyostelic, erect stem with dense multicellular scales and surrounded by persistent petiole bases and adventitious roots. The stem contains a central pith lacking medullary bundles, which is surrounded by a dictyostele, and the cortex externally. Each meristele of the dictyostelic ring is enclosed by a sclerenchyma sheath. The pith and cortex are parenchymatous. The proximal petiole bases present a frond trace composed of numerous meristeles, arranged in 1 abaxial and 2 adaxial arcs, with internally projecting bundles on the upper and lateral sides. The feature combination of the new genus is nearly identical to the anatomical structures of modern scaly genera of the Cyatheaceae apart from the absence of medullary bundles. It is interpreted as a primitive representative of early Cyatheaceae, that closely resembles the modern scaly genera, which suggests that in the Cretaceous, the tree ferns in this family were already in possession of most of the anatomical characteristics observed in extant taxa. The fossil records of the stems, petioles, and spores indicate that during the Jurassic and Cretaceous, the Northeastern region of Asia may have been one of the distribution centers of early Cyatheaceae.