Fertile Axes Research Articles

A fresh look on the morphology of Azaniadendron Rayner: a ligulate lycopsid from the Permian of Gondwana

The monotypic Azaniadendron fertile Rayner, a lycopsid from the Guadalupian of Gondwana, is investigated providing new data on the morphology of its leaf cushions and their variation in shape. Evidence for a ligule is presented for the first time, elucidating, at least for this genus, a dilemma about the presence of this structure in lycopsids from the Permian Glossopteris flora. New data on its fertile axes question the assumption that the taxon produced true cones. We hypothesise that the genus belong to the Isoetales. Unequivocal evidence of the taxon is so far known only from the South African Vryheid Formation and its equivalent beds.

A new polysporangiate land plant with novel fertile organs from the Lower Devonian of Guizhou, southwestern China

The diversification of early land plants during the mid-Paleozoic has been considered an important event that was essential for the evolution of terrestrial ecosystems, and the plant fossils from numerous localities around the world are the key for understanding this event. Here we report a new plant, Teyoua antrorsa gen. et sp. nov., from the lower part of the Mangshan Group at a newly found locality near Baoyang Village (Baoyang section), Duyun City, Guizhou Province, southwestern China. The plant-bearing horizon at this locality is suggested to be Early Devonian in age (probably Pragian), based on the occurrence of Adoketophyton subverticillatum and Zosterophyllum australianum, two plants also occurring in the well-known Pragian-aged Posongchong Formation of Yunnan, China. The fertile axes of Teyoua gen. nov. are dichotomously divided at least five times and each of the ultimate branches terminates in a fertile organ. The fertile organs are composed of up to seven linear sporangia that share a common base and depart three-dimensionally. This plant is assigned to the polysporangiate clade, in that the whole architecture and internal anatomy remain unknown, but its similarities to some basal euphyllophytes are notable. Nevertheless, the linear sporangia of Teyoua gen. nov., and their grouping as a unique fertile organ, add to the diversity of fertile structures in early polysporangiophytes.

Omphalophloios wagneri sp. nov., a new sub-arborescent lycopsid from the middle Moscovian (Middle Pennsylvansian) of the Illinois Basin, USA

Described is a new species of sub-arborescent lycopsid, Omphalophloios wagneri sp. nov. from roof shale of the middle Moscovian (Bolsovian/Atokan) (Middle Pennsylvanian) Lower Block Coal in the Illinois Basin, Indiana, USA. Available material represents mostly fragments of 16 to >60 mm wide fertile axes that bear densely spaced sporangia, which are flattened due to compaction into disc-like shape, 2.5–3.1 mm in diameter. The outer sporangial cell wall layer displays a gradual transition from isometric cells in the central parts of adaxial and abaxial sporangial valves, to a narrow belt of elongated cells in the equatorial area, interpreted as a dehiscence zone. Micro- and megasporangia alternate in irregular patches, a single sporangium being attached adaxially to an extended sporophyll base. Cyperites-like sporophyll distal laminae are ~25 mm long at fertile shoot apices but become progressively longer (>110 mm) down the shoots. Based on size distribution of stems, fertile shoots are estimated to bifurcate at least five times, which suggests that O. wagneri formed a relatively dense crown. The entire habit of the plant is difficult to assess from existing material; however, the tree was probably small and interpreted as colonizing low lying to slightly raised peat swamps. Omphalophloios wagneri differs from all other adpression-based species of the genus in having the smallest sporangia and several orders of fertile-axis bifurcations. In situ megaspores of the Zonalesporites brassertii type also are different from all other Omphalophloios megaspores.

Lilingostrobus chaloneri gen. et sp. nov., a Late Devonian woody lycopsid from Hunan, China

Lycopsids are a minor component of current terrestrial herbaceous floras. However, lycopsid fossil diversity shows a great diversity and disparity including heterosporous woody plants, e.g. the giant isoetaleans that populated the extensive Pennsylvanian wetlands. The earliest known isoetaleans come from late Devonian localities from China. Here, we describe Lilingostrobus chaloneri gen. et sp. nov., a new isoetalean lycopsid from the Upper Devonian (Famennian) Xikuangshan Formation of China (Hunan Province, South China), which adds to the already impressive diversity of the Devonian lycopsids from China. Lilingostrobus shows an unusual combination of characters. This new plant is pseudoherbaceous, with a possible tufted habit, and consists of narrow axes with rare isotomies. The stem includes small quantities of secondary xylem. Each fertile axis bears one terminal strobilus comprising sporophylls ending in a very long upturned lamina. Microspores and putative megaspores have been found, but whether the plant has mono- or bisporangiate strobili is unknown. Importantly, our cladistic analysis identifies Lilingostrobus as a direct precursor of Isoetales, which provides new insights into the early evolution of lycopsids.

Pollen Organ Telangiopsis sp. of Late Devonian Seed Plant and Associated Vegetative Frond

Pollen organ Telangiopsis sp., associated with but not attached to vegetative fronds, has been collected from the Upper Devonian (Famennian) Wutong Formation, Dongzhi County, Anhui Province, China. Fertile axes with terminal pollen organs are dichotomous for 2–4 times and may be proximally attached by fragmentary pinnules. Pollen organs are synangiate and borne on the top of a short stalk. Synangia are radial in symmetry and each consists of 4–8 elongate microsporangia fused at base. Microsporangia have a longitudinal dehiscence line and show a tapered apex. The associated stem is spiny and bears a vegetative frond which bifurcates once at the basalmost part. Frond rachises possess one order of pinna arranged alternately. Pinnules are borne alternately, planate, highly dissected, and equally dichotomous for 2–3 times. Comparisons among Late Devonian seed plants recognize several branching patterns in the fertile fronds/axes bearing terminal pollen organs. Telangiopsis sp. reinforces that the Late Devonian pollen organs are synangiate usually with basally fused microsporangia. It is suggested that the evolutionary divergence of radial and bilateral symmetries of pollen organs may have occurred in the Famennian, when the earliest seed plants evolved planate and sometimes laminate pinnules.

Latisemenia longshania, gen. et sp. nov., a new Late Devonian seed plant from China.

The earliest known ovules in the Late Devonian (Famennian) are borne terminally on fertile branches and are typically enclosed in a cupule. Among these ovules are some that have terete integumentary lobes with little or no fusion. Here, we report a new taxon, Latisemenia longshania, from the Famennian of South China, which bears cupulate ovules that are terminal as well as opposite on the fertile axis. Each ovule has four broad integumentary lobes, which are extensively fused to each other and also to the nucellus. The cupule is uniovulate, and the five flattened cupule segments of each terminal ovule are elongate cuneate and shorter than the ovule. Associated but not attached pinnules are laminate and Sphenopteris-like, with an entire or lobate margin. Latisemenia is the earliest known plant with ovules borne on the side of the fertile axis and may foreshadow the diverse ovule arrangements found among younger seed plant lineages that emerge in the Carboniferous. Following the telome theory, Latisemenia demonstrates derived features in both ovules and cupules, and the shape and fusion of integumentary lobes suggest effective pollination and protection to the nucellus. Along with other recent discoveries from China, Latisemenia extends the palaeogeographic range of the earliest seed plants.

Periodicity of reproductive growth in lycopsids: An example from the Upper Devonian of Zhejiang Province, China

Monilistrobus Wang et Berry is a fossil lycopsid reported from the Upper Devonian Wutong Formation of Jiangsu Province, China, and includes only the type species Monilistrobus yixingensis Wang et Berry. Along a single fertile axis, Monilistrobus has cone-like structures separated by and alternated with a length of vegetative region, which is an important character here termed as periodicity of reproductive growth. The alternation of fertile and vegetative growth occurs regularly and produces repeated intercalary (non-terminal) fertile zones. New specimens, identified as Monilistrobus cf. yixingensis, from the same formation but of Zhejiang Province extend the geographic distribution of this genus. These new specimens demonstrate morphological variations within this genus, such as the lack of spiny appendages on the leaves, different measurements of leaf bases, and different shapes and positions of cone-like structures. The distribution of intercalary fertile zones, as summarized for the first time in this paper, occurs in the Drepanophycales, the Protolepidodendrales, the Isoëtales, the Lycopodiales, the Selaginellales, and Wuxia Berry, Wang et Cai and Monilistrobus of uncertain affinities. Thus, this peculiar trait might have evolved in the very early evolutionary stage of the lycopsids, as indicated in the basal group Drepanophycales. However, the presence of repeated, two or more intercalary fertile zones along a single fertile axis is demonstrated only in Monilistrobus and the extant Huperzia Bernhardi.

Polyamines in morphogenesis and development: a promising research area in seaweeds.

Polyamines in morphogenesis and development: a promising research area in seaweeds.

Psilophyton szaferi sp. nor. from the Lower Devonian of the Holy Cross Mountains. Poland

<em>Philophyton szaferi</em> sp. nov. belonging to the <em>Trimerophytina</em> was found in the Lower Devonian (Emsian) in the bore-hole Modrzewie 2A near Bostów in the Holy Cross Mountains (Gory Świętokrzyskie). The axes are sterile and fertile. their branching is dichotomous, unequally dichotomous and unequally dochotomous where the wider branch tends to form the main axis. The majority of axes branch in one plane, some in different planes; they show on their surface irregularly distributed enations in the form of rounded swellings. Some of them continue downwards as protruding ridges forming a characteristic longitudinal pattern. The apices of sterile axes are forking. Fertile axes end in clusters of fusiform. upright sporangia, arranged in pairs. The vascular strand shows protoxylem inside and metaxylem outside. Tracheids possess scalariform thickenings and what appear to be small pits between them. The systematic position of the plant and its position in the evolutionary sequence leading to megaphyllous leaves is discussed.

Reproductive Organs and In Situ Spores of Asteroxylon mackiei Kidston & Lang, the Most Complex Plant from the Lower Devonian Rhynie Chert

Asteroxylon mackiei is the largest and most complex vascular land plant from the Lower Devonian Rhynie Chert. Fertile remains were first reported nearly 40 years after the description of the sterile axes but were not described in greater detail. In this contribution, we document several fertile axes from longitudinal and transverse thin sections. Sporangia, consisting of two kidney-shaped valves, are interspersed among the nonvascularized leaflike appendages and attached to the axis with a short pedicel. The sporangia are curved and lie close to the axis. Sporangia possess a dome-shaped central structure that forms the continuation of the short stalk into the sporangial cavity. The in situ spores are identified as Retusotriletes cf. triangulatus. The sporangia were apparently abscised after sporulation. Fertile zones with leaflike appendages and sporangia alternate with sterile zones with only leaflike appendages within an axis, suggesting a periodicity of growth.

A new genus of Early Devonian plants with novel strobilar structures and vegetative appendages from the Posongchong Formation of Yunnan, China

A new plant, Dibracophyton acrovatum gen. et sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Wenshan District, southeastern Yunnan, China. The plant has creeping axes from which arise vegetative and fertile axes. The vegetative axes helically bear lateral dichotomous appendages with curved or round tips. The fertile axes possess terminal strobili with numerous fertile units arranged in irregular helices. Each fertile unit consists of a stalked long-elliptical sporangium, with dehiscence into two equal valves, and two discrete long-ovate bracts covering sporangium from above–below directions. A new genus and species is thus established based on these characters and is temporarily regarded as incertae sedis of Tracheophyta, although it perhaps closes to the barinophytes in affinity. Detailed comparisons with other plants having a similar architecture, i.e., sporangia closely associated with modified vegetative structures, are made. The discovery of D. acrovatum further enriches the composition of the Posongchong flora and demonstrates great morphological disparity of the Early Devonian vascular plants.

Re-examination of specimens attributed to Sawdonia curstipa Wang and Hao (zosterophyll) from the Middle Devonian of Xinjiang, China

Specimens previously attributed to Sawdonia curstipa were re-examined. Some of the specimens are transferred to Serrulacaulis cf. S. furcatus based on axial morphology. Other specimens, including fertile axes with one or two rows of sporangia with curved stalks and sterile axes with cone-shaped spines covering the surface, are of uncertain assignment due to poor preservation. The nomenclature problem of Sawdonia custipa is also noted.

A new species of Adoketophyton from the Lower Devonian (Pragian) Posongchong Formation of Yunnan, China

A new species of early vascular plant, Adoketophyton parvulum sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Yunnan, China. The plant is composed of main axes, lateral vegetative branches and isotomous or anisotomous fertile axes. The vegetative axes branch isotomously or pseudomonopodially in three dimensions, with some laterals ending in terminal circinately coiled tips. K-shaped branching and tubercles are preserved. Terminal strobili consist of four vertical rows of fertile units, arranged in opposite and decussate pairs. Each fertile unit comprises a fan-shaped sporophyll and a sporangium attached adaxially by a short stalk at the base of the sporophyll. The strobili and fertile units (sporophylls and associated sporangia) of this new species are much smaller than those of the type species, Adoketophyton subverticillatum, and the ratio of heights of sporangia to sporophyll laminae in the two species shows a large discrepancy. The affinity and evolution of Adoketophyton are discussed. The various leaf-like appendages in plants reported from the Early Devonian of South China are considered a phenomenon of convergent evolution.

A new microsporangiate organ from the Lower Carboniferous of the Novgorod Region, Russia

A new species of the genus Telangiopsis, T. nonnae O. Orlova et Zavialova, was described on the basis of a microsporangiate organ from the Lower Carboniferous deposits of the Novgorod Region. The morphology of branching fertile axes, synangia, and sporangia was thoroughly studied. The three-dimensional system of fertile axes branches monopodially; ultimate axes bear numerous connivent bunches of synangia, which consist of three to six basally fused elongated ovate sporangia. The morphology and ultrastructure of prepollen grains were studied, which were extracted from the rock matrix surrounding the sporangia. The two-layered exine includes a well-developed endexine and an alveolate ectexine, with one-three rows of large thin-walled alveolae. The new species was compared with other Early Carboniferous microsporangiate organs.

Famennian charcoal of Belgium

Charcoal results from an incomplete combustion of biological material in anoxic conditions and has a high potential for three-dimensional cellular preservation. Most of the Belgian Upper Devonian flora is known through compression fossils, mainly from the siliciclastic Evieux Formation; no charcoal-bearing layers had been reported to date. We have recently identified organic-rich beds from three late Famennian localities (Val-Dieu quarry, Trooz quarry and Arbre quarry). The three localities are described from the sedimentological point of view. The Arbre and Trooz quarries contain allochthonous specimens of charcoalified wood. They are identified as Callixylon in Arbre. In Trooz, the specimen belongs either to an undescribed species of Callixylon or to another taxon of woody (pro)gymnosperm. The Val-Dieu quarry, by contrast, yielded a more diverse charcoalified assemblage including leafy remains, branches and fertile axes related to ferns, sphenopsids and (pro)gymnosperms. This material experienced moderate transportation before burial. The Val-Dieu assemblage is exceptional for Late Devonian deposits as it represents a moderately disturbed litter interpreted as representing a swamp environment and its proximal margins. This assemblage is an illustration that the fossil charcoal record can provide a unique opportunity to study in fine detail the evolutionary history and past diversity of life.

Cordaitalean Seed Plants from the Early Permian of North China. III. Reconstruction of the Shanxioxylon taiyuanense Plant

The third of three whole‐plant cordaitaleans we reconstructed from a single Early Permian locality in northern China is Shanxioxylon taiyuanense. The name is based on the stem S. taiyuanense B. Tian & S.‐J. Wang emend. S.‐J. Wang & J. Hilton, which has a large septate pith and endarch cauline bundles that generate mesarch leaf traces that dichotomize at the pith margin. The comparatively small, elongate leaves with few veins and thickened margins are assigned to Cordaites taiyuanensis S.‐J. Wang & B. Tian emend. S.‐J. Wang and J. Hilton, which is here nomenclaturally typified after a previous invalid publication. Fertile axes are diamond shaped in transverse section, bearing in a tetrastichous arrangement numerous bracts and secondary shoots that consist of basal leaflike sterile scales and apically concentrated fertile scales. Male cones of Cordaitanthus ximinensis S.‐J. Wang & B. Tian consist of 20–30 sterile scales and an unknown number of fertile scales that produce pollen assignable to Florinites. Fe...

Hamatophyton from the Late Devonian of Anhui Province, South China and Evolution of Sphenophyllales

Abstract:Well‐preserved specimens of Hamatophyton verticillatum collected from the Upper Devonian (Famennian) Wutong Formation of Chaohu district, Anhui Province, South China, display more complete fertile axes in three orders and multiple divisions. Comparisons indicate that Hamatophyton possibly does not have palmate planate sterile leaves but hook‐like linear ones with rare divisions. We propose seven definitive characters of Sphenophyllales: (1) completely whorled lateral organs; (2) sterile leaves; (3) strobili; (4) “sporangiophores” or stalks with reflexed tips bearing sporangia; (5) three‐ or four‐ribbed primary xylem; (6) exarch maturation of primary xylem; and (7) secondary xylem. The Sphenophyllales probably originated from the Iridopteridales based on similarities in whorled lateral organs, ribbed primary xylem and peripheral protoxylem strands. In transition from Iridopteridales to Sphenophyllales, morphological changes involve partially whorled to completely whorled lateral organs, sterile ultimate appendages to leaves, and fertile ultimate appendages to “sporangiophores”/stalks with bracts; anatomical modifications include configuration and maturation of primary xylem, and presence of secondary xylem.

Ceramium periconicum sp. nov. (Ceramiaceae, Rhodophyta): a new subtidal species from Baja California Sur, Mexico

Abstract Ceramium periconicum sp. nov. is described from Baja California Sur, Mexico based on the developmental morphology of vegetative and reproductive plants. The new species is characterized by 4–5 periaxial cells, three cortical initials per periaxial cell (a third of which are produced by vertical division and situated between adjacent periaxial cells), absence of basipetal cortical filaments, and by projecting tetrahedral tetrasporangia in seriate series in an abaxial row. Thalli are less than 3 mm tall and occur in dense tufts. C. periconicum differs from most incompletely corticated Ceramium species in that each periaxial cell divides to produce three cortical initials. Within the genus, three cortical initials per periaxial cell have been reported in C. codii and C. reptans. C. periconicum differs from these species in that two cortical initials are directed acropetally and the third is directed laterally, having been cut off vertically from the periaxial cell and maturing without further divisions between the two adjacent periaxial cells. C. periconicum is also distinguishable from other Ceramium species, such as C. australe, C. clarionense, C. macilentum, C. shepherdii, C. caudatum, C. mazatlanense, and C. personatum by the absence of basipetal cortical filaments and by the sequential production of tetrasporangia from the abaxial sides of fertile axes.

Two Species of Zosterophyllum from South China and Dating of the Xujiachong Formation with a Biostratigraphic Method

Abstract: Zosterophyllum longa sp. nov. is reported from the Lower Devonian Pingyipu Formation, Jiangyou District, northern Sichuan of China. This new plant has vertically elongate sporangia differing from all known species of Zosterophyllum, demonstrating morphological variations in Zosterophyllophytina. New materials of Zosterophyllum yunnanicum from the Lower Devonian Xujiachong Formation, Qujing District, eastern Yunnan of China show that fertile axes of this species are anisotomous or pseudomonopodial or K‐shaped in branching. Sometimes fertile lateral axes are very short and bear an axillary axis at the dividing point. Distinct thickening occurs along the whole margin of a sporangium, with sporangial lobes undeveloped. The evolution of Zosterophyllum is tentatively discussed. A biostratigraphic method of Gerrienne and Streel is introduced and applied to dating of the Lower Devonian Xujiachong Formation, which is considered as of the late Pragian‐early Emsian.

The Primary Body of Rellimia thomsonii: Integrated Perspective Based on Organically Connected Specimens

The Blenheim‐Gilboa locality in New York contains Rellimia thomsonii specimens preserved as both compressions and permineralizations that offer an unusually complete perspective on the reproductive structures, primary body, and secondary anatomy of this Middle Devonian plant. Here we describe the vegetative appendages, axis and branch size relationships, and trace departure as well as primary anatomy, including phloem sieve cells of interconnected axis orders of vegetative and fertile specimens. At least five orders are present, and each axis order is approximately half the diameter of the parent axis. Three‐ribbed protosteles are evident in all axes. Protoxylem in transverse section is a continuous three‐ribbed sheet one or two tracheids wide, enveloped by several cell layers of metaxylem in turn surrounded by primary phloem. Sieve cells have vertically arranged sieve areas. Trace departure to axes is similar in vegetative and fertile axes. Traces are apparent proximally as radial elongations of the tip of the parent primary xylem rib. In distal sections, the rib tip is tangentially elongated; ultimately, the trace becomes three‐ribbed. Traces to vegetative appendages and fertile organs divide dichotomously. The new features described here allow us to expand and complement previous work and to discuss our whole‐plant concept of Rellimia.