TRILOBOXYLON ASHLANDICUM GEN. AND SP. N. FROM THE UPPER DEVONIAN OF NEW YORK

A new taxon is described from the Upper Devonian, Oneonta formation in the northern Cats-kills of New York. Triloboxylon gen. n. is represented by petrifactions showing two orders of branching. The main axis bears branches spirally and the latter bear the ultimate appendages spirally. Ultimate appendages branch dichotomously twice, in one plane. Primary xylem of the main axis and branches is three-armed with mesarch protoxylem extending in a continuous band within each arm. Primary xylem of the ultimate appendage is terete and dichotomizes twice. Metaxylem elements are characterized by scalariform and circular-bordered pitting on all walls. The cortex is composed entirely of isodiametrical parenchyma cells. Triloboxylon is compared with other genera with three-lobed protosteles. Its possible affinity with the Aneurophytales is shown. The morphological nature of the “frond” of the Aneurophytales and the possibility that the group possesses the morphological equivalent of simple leaves are discussed.     

PROTEOKALON A NEW GENUS OF PROGYMNOSPERMS FROM THE DEVONIAN OF NEW YORK STATE AND ITS BEARING ON PHYLOGENETIC TRENDS IN THE GROUP

Proteokalon gen. nov. is described from the Upper Devonian Catskill deposits of New York. Two orders of branching and ultimate appendages are preserved' by petrifaction and by compression. The first order bears branches decussately and has a skewed four-armed protostele that occasionally dichotomizes. Second-order branches dichotomize rarely and most have T-shaped or three-armed protosteles. They bear ultimate appendages alternately, either in lateral pairs, or singly from the abaxial side. These appendages divide several times in one plane. Their vascular strand is terete. Maturation of the primary xylem is mesarch, and it consists of tracheids and parenchyma. Secondary xylem and phloem and a periderm are present. The outer cortex has a system of hypodermal fibers. Proteokalon is most similar to Tetraxylopteris and Triloboxylon of the Aneurophytales. A comparison of the stratigraphic occurrence of Protopteridium, Aneurophyton, Tetraxylopterism, Sphenoxylon, Triloboxylon, and Proteokalon suggests some evolutionary trends among the Aneurophytales.     

ANATOMY AND RELATIONSHIPS OF SOME DEVONIAN PROGYMNOSPERMS FROM NEW YORK

New specimens of Triloboxylon ashlandicum Matten and Banks (1966) show additional features of the anatomy and morphology of the plant. The primary xylem has strands of parenchyma associated with trace formation. Secondary xylem and phloem are described for the first time. The outer cortex, previously unknown, contains hypodermal fiber strands. The ultimate appendages are much divided and planated. Specimens of Aneurophyton hallii (Arnold, 1940) were reexamined and newly prepared. They are transferred to the genus Triloboxylon as T. hallii. Triloboxylon is transferred from Pteropsida-Incertae Sedis to the Aneurophytales. New information on the morphology and anatomy of Telraxylopteris is presented and its identity to Sphenoxylon is supported.     

THE CRETACEOUS PTERIDOSPERMS RUFLORINIA AND KTALENIA AND IMPLICATIONS ON CUPULE AND CARPEL EVOLUTION

The vegetative (Ruflorinia sierra) and fertile (Ktalenia circularis) organs of an Early Cretaceous pteridosperm collected from Santa Cruz Province in Argentina are described. The sterile leaf is at least tripinnate and bears decurrent secondary pinnae with obliquely attached, sharply pointed pinnules. The fertile member arises from the base of the vegetative rachis and bears two types of appendages, cupules and bracts. Bracts are attached to the main axis near cupules and are present in clusters of up to six. Cupules are sessile, spherical, and arranged in opposite or subopposite pairs along the axis. A small lip is present on one surface of the cupule. The number of seeds per cupule may be one or two, with each characterized by a distal nucellar beak and circular, chalazal scar. Cuticular anatomy, including the fine structure of the stomatal complex, is described for both vegetative and reproductive organs. The cupules of Ktalenia and other Mesozoic seed plants are compared, and a discussion presented regarding the possible function of the cupule.     

Reinvestigation of Nystroemia pectiniformis Halle, an enigmatic seed plant from the Upper Permian of China

Reinvestigation of Nystroemia pectiniformis Halle from the Upper Shihhotze Formation of Shanxi Province, China, has led to the identification of new and important features of this enigmatic Late Permian seed plant, permitting its typification and diagnosis. After reassembling several of the previously studied specimens to form a single articulated branching system comprising at least four orders of branching, previously unknown features of its branching pattern and morphology have been characterized. First–order axes are wide and branch to one side only, bearing second–order branches either singly or in pairs and of two kinds: one fertile and bearing characteristic ovulate branching systems and the other presumably vegetative. Ovulate second–order axes are narrow and branch to one side only, producing numerous, closely spaced lateral branches in two alternate to sub–opposite rows. Lateral branches are slender and produce numerous ovulate branching systems to one side of the axis only. Ovulate branching systems divide unequally to produce 3–15 ultimate axes of different lengths that are planated. Each ultimate axis bears a single terminal ovule with 180 degree rotational symmetry and two horn–like integumentary projections distally. The other kind of second–order axes are distinct from those bearing ovules; they are wider and longer and branches occur on both sides of the secondary axis, lacking divisions in close proximity to the first–order axis. These have only been observed incomplete although their distinct morphology indicates they are unlikely to be ovulate branches from which ovules/seeds have been shed. Additional organs of the Nystroemia plant are considered, including pollen organs previously assigned by Halle to the same species (displaying its characteristic branching style), and also leaves of Chiropteris reniformis Halle that were probably borne on the larger kind of second–order branches. Implications of Nystroemia on seed plant evolution and distribution are discussed, and it is concluded that this most likely represents a late stratigraphic occurrence of a plesiomorphic hydrasperman–type seed plant with affinities closely allied to members of the Lyginopteridales.     

TETRAXYLOPTERIS SCHMIDTII: ITS FERTILE PARTS AND ITS RELATIONSHIPS WITHIN THE ANEUROPHYTALES

The fertile branching system of Tetraxylopteris is composed of successive “nodes” bearing opposite and decussately arranged, upcurved sporangial complexes. By means of the transfer technique the morphology of the sporangial complex was revealed. It consists of a main stalk which dichotomizes twice producing four major branches. Each of the four branches is further subdivided three times, the subdivisions being arranged alternately and pinnately. The ultimate divisions bear the sporangia singly and terminally. The sporangial complexes decrease in size distally and are more tightly curved at the apex. The sporangia are oblong-oval with an acute apex. The spores are identical to the dispersed spore taxon Rhabdosporites langii, Richardson. They are spherical, trilete and pseudosaccate with a fine granular ornament on the pseudosaccus. They are 75–176 μ in diameter and show developmental stages from young tetrads to separated, fully mature spores depending on the age of the sporangium from which they were obtained. This is the first account of spores in sporangia of Tetraxylopteris. The diagnosis of the genus and species are emended to include the new information and the order Aneurophytales is redefined.     

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.     

ACTINOXYLON BANKSII GEN. ET SP. NOV.: A PROGYMNOSPERM FROM THE MIDDLE DEVONIAN OF NEW YORK

A new genus from a Middle Devonian locality near Cairo, N. Y., is described. Actinoxylon gen. nov. is based upon pyritic petrifactions. Three orders of branching are present: penultimate branch, ultimate branch, and leaf. The penultimate branch bears spirally arranged ultimate branches and leaves, the leaves apparently replacing the branches in the spiral. The ultimate branches bear opposite to subopposite and decussate leaves. The leaves are non-planated, unwebbed structures which show at least three dichotomies. Each segment of the leaf is terete as are all other axes. Internally the penultimate branch has a six-lobed actinostele with mesarch protoxylem areas, one or two per lobe. Secondary xylem is visible in the oldest parts of several specimens. The xylem has helical-reticulate, reticulate, scalariform and circular-pitted elements. The presumptive areas of phloem are occupied by cells with dark contents. The cortex is composed of a parenchymatous inner region and a sclerenchymatous outer region. The ultimate branch traces are at first three-lobed protosteles, later becoming four-lobed. Several ultimate branch traces also possess secondary xylem while within the cortex of the penultimate branch. The leaf traces are terete strands. Below each forking of a leaf segment there is a corresponding forking of the vascular strand. Actinoxylon is compared with the progymnosperms Actinopodium, Svalbardia, Archaeopteris, Siderella, and Tetraxylopteris. The anatomy of the penultimate branch of Actinoxylon is similar to that of Actinopodium, Archaeopteris macilenta, and Siderella. The ultimate branch traces of Archaeopteris and Actinoxylon are similar. The ultimate branch stele and pattern of trace formation in Actinoxylon is similar to the stelar configuration and trace formation in the r + 2 axes of Tetraxylopteris schmidtii. The unwebbed leaves are similar to those of Archaeopteris fissilis, Svalbardia, and the terminal units of the Aneurophytales.     

A FERTILE SPECIES OF TRIPHYLLOPTERIS FROM THE EARLY CARBONIFEROUS (MISSISSIPPIAN) OF SOUTHWESTERN VIRGINIA

The first occurrence of attached fertile structures to foliage assignable to the form genus Triphyllopteris Schimper is reported from the early Carboniferous Price Formation of southwestern Virginia. Sporangium-bearing branch systems consisting of a basal undivided foliar region and a distal much-divided fertile region are described as a new species T. uberis Skog and Gensel. Ovoid fusiform sporangia, 2.0 mm long and 0.5 mm wide and containing trilete spores, terminate ultimate divisions of the branch systems and collectively form masses up to 4 cm in all dimensions. T. uberis is compared to previously known sporangiate organs of Late Devonian and early Carboniferous age, many of which lack attached foliage. Similarities in the overall branching pattern of many of these non-synangiate, sporangiate organs of early Carboniferous age is noted. The possible mode of dispersal and affinities of the plant bearing T. uberis fertile foliage is discussed.     

THE CAIRO FLORA (GIVETIAN) FROM EASTERN NEW YORK. I. REIMANNIA,TERETE AXES,AND CAIROA LAMANEKII GEN. ET SP. N.

A collection of over 200 petrified Middle Devonian plants was made from a single locality near Cairo, New York. This paper represents the second of a series enumerating the plants of the flora. Reimannia aldenense with a single lateral appendage containing a terete xylem strand that divides is present. Reimannia is thought to represent young branches within the Aneurophytales. Many of the sections made for the study of the flora contain small, terete axes. Some have a very distinctive epidermis. Some dichotomize several times. Cairoa lamanekii gen. et sp. n. shows closest affinity to the Aneurophytales yet differs in that the shape of the primary xylem is not consistently repeated from one order of axis to the next. It is suggested that Cairoa and Proteokalon represent a distinctive subgroup in the Aneurophytales.     

A NEW SPECIES OF ZOSTEROPHYLLUM FROM THE EARLY DEVONIAN OF NEW BRUNSWICK

A new species of Zosterophyllum, Z. divaricatum Gensel, is described from the late Early Devonian (Emsian) of northern New Brunswick, Canada. It is a Platyzosterophyllum type, consisting of slender sometimes bifurcating axes with laterally borne sporangia oriented to one side of the axis. The species is distinctive in that axes bifurcate within fertile regions and in sporangium shape and attachment. Aspects of the morphology of axis and sporangium cuticle, tracheids, and spores are presented and considered in relation to comparable features in other Zosterophyllum species. Associated vegetative axes exhibiting H- and K-branching patterns and also cuticular features similar to the fertile specimens are described and it is suggested that they may represent parts of the same plant. Zosterophyllum divaricatum is most similar to Z. llanoveranum, Z. fertile, and Z. spectabile, and also resembles Rebuchia ovata to some extent. Z. divaricatum offers considerable information on variation within one species concerning sporangium shape, attachment, and distribution and expands the known diversity of Platyzosterophyllum types.     

A new euphyllophyte Kunia venusta gen. et sp. nov. from the Middle Devonian of Yunnan,South China

Abstract Kunia venusta gen. et sp. nov. is reported from the late Middle Devonian (Givetian) Haikou Formation near Kunming City, Yunnan Province, China. This plant has three orders of naked axes that divide pseudomonopodially. The second‐ and third‐order axes occur in a helix. Fertile appendages are distantly spaced and helically inserted to the third‐order axis; they comprise equally dichotomous branches terminated by two clusters of paired and fusiform sporangia. Sterile appendages are dichotomous and distally recurved. A comparison is made with the basal euphyllophytes including the trimerophytes, cladoxylopsids, zygopterids, stauropterids, and some relevant genera of uncertain affinity. The new plant resembles them in dichotomous appendages with terminal elongated sporangia, but differs mainly in the three orders of pseudomonopodial axes bearing helical laterals. It is thus placed in the Euphyllophytina as incertae sedis. It is suggested that an evolutionary divergence in the branching pattern and appendage morphology might have occurred in the Middle Devonian euphyllophytes, that is, maintaining three dimensions versus yielding more or less planation.     

The transition from vegetative to fertile tissue in Fucus vesiculosus

At various stages of receptacle development, segments of Fucus vesiculosus thallus subtending the fertile tips have been grown in culture. At the times of gamete maturation and gamete shedding a number of both reproductive and vegetative branches are regenerated from the wound callus. This is the only region of the Fucus thallus which has been found capable of regenerating fertile receptacles. The effects of a number of growth regulatory substances were studied. 1-naphthoxyacetic acid stimulated budding but no substance increased the proportion of fertile branches. Extracts prepared from mature receptacles did not induce the regeneration of fertile branches from vegetative thallus, but they markedly inhibited the regeneration of any branches. Subsequent estimations of the growth regulatory substances in the receptacles showed that there was a marked increase in growth inhibitors during gamete development. Growth stimulatory substances were also present but these were masked in crude extracts by the amount of inhibitors.     

ON PHENOTYPIC EXPRESSION,MORPHOGENETIC PATTERN AND SYNANGIUM EVOLUTION IN PSILOTUM

Both the typical form and the appendageless variant of Psilotum nudum produce terminal synangia at the ultimate tips of the aerial axes. One clone in particular of the typical appendaged form produced synangia entirely at the tips of the aerial branches, as in the appendageless variant, and also developed occasional lateral transitional entities on the upper aerial axis displaying appendagelike and axislike morphological qualities. A developmental comparison of synangium development at the ultimate tips of aerial branches and of unusually elongating and normal sized fertile-appendages showed that the morphogenetic pattern of synangium development was similar. Anatomical and morphological evidence showed the synangium to be derived from terminal subdivisions or bifurcations of the apical meristem of each structure studied. This supports the phyletic concept that the synangium of the Psilotaceae is basically terminal to an axis or an axis homologue, and that it probably evolved from terminal bifurcative branching. Occasional multiple sporangium lobes may be formed on a P. nudum synangium which may not be represented by vascular bundles. Two hypothetical phyletic models of synangium evolution are proposed that could be used to explain this phenomenon and which should be tested by further evidence. Typical and appendageless P. nudum were compared in their morphogenetic pattern developed at the upper axis vegetative apical meristem, and a reconciliation was made between the structuring of the apparently disparate forms, which involved the presence or absence of serial ordering in apical derivatives. It is suggested that this could serve as a model for appendage evolution in the family Psilotaceae.     

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.     

A new Carboniferous equisetale from western Gondwana

Upper Paleozoic sphenopsids from western Gondwana are little known. New finds were made from the Upper Carboniferous of the San Juan province (Argentina). The specimens include vegetative and fertile characters that allow the definition of a new genus and species: Gondwanites subtilis. They are characterized by slender branches bearing whorls of very thin, simple or divided leaves. Simple fertile organs are borne in whorls just below the verticel of leaves. The presence of dichotomized leaves and bractless fertile organs in the new taxon suggests its probable primitive condition.     

IBYKA AMPHIKOMA,GEN. ET SP. N., A NEW PROTOARTICULATE PRECURSOR FROM THE LATE MIDDLE DEVONIAN OF NEW YORK STATE

Ibyka gen. n. is described from late Middle Devonian compressions and petrifactions collected in eastern New York State. It is a robust plant of which three orders of branching and ultimate appendages (leaves) are known. The latter dichotomize up to five times, are arranged spirally on all orders of branching, are three-dimensional, and all orders are terete in cross section. Fertile appendages, homologous with the sterile, are terminated by sporangia. The protostele has five or six arms, the maturation is mesarch, and the protoxylem disintegrates leaving lacunae at the tips of the arms. Traces to appendages are terete and arise spirally from the tips of the arms. The primary xylem consists of tracheids only, the phloem of thin-walled cells and probable tanniniferous cells. The cortex consists of parenchyma and groups of sclereids. Secondary xylem is lacking. Ibyka is placed in a new order, Ibykales, close to the Hyeniales (protoarticulates) and to the Pseudosporochnales all three of which probably evolved from Trimerophytina.     

BARINOPHYTON CITRULLIFORME (BARINOPHYTALES INCERTAE SEDIS,BARINOPHYTACEAE) FROM THE UPPER DEVONIAN OF PENNSYLVANIA

Barinophyton citrulliforme is definitely proven to be a tracheophyte. The vascular cylinder of the main axis is an exarch protostele composed of tracheids having a continuous secondary wall folded into protrusions into the cell lumen. These protrusions delineate the position of annular thickenings which were deposited earlier than the continuous secondary wall. Between successive protrusions, the later-deposited secondary wall is interrupted by minute pitlike structures. It is suggested that the secondary walls of the tracheids were laid down in a two-phase depositional sequence. The fertile system of B. citrulliforme consists of a main axis bearing spirally arranged strobili. The strobilus consists of an axis that bears two alternate rows of sporangiferous appendages. The sporangiferous appendages are borne laterally along the strobilar axis and recurve abaxially around the axis. The sporangia are attached along the inside curve of the appendages, one sporangium per appendage, each containing both microspores and megaspores. This species thus exhibits sporangial heterospory which is considered to be an adaptation to an aquatic habit and the sporangia are considered to be functional analogs of the sporocarps of Marsilea. The interpretation of the strobilus is morphologically identical to Ananiev's interpretation of the strobilus of Pectinophyton bipectinatum; consequently P. bipectinatum is here transferred to Barinophyton as B. robustius comb. nov.     

Leaf evolution in early-diverging ferns: insights from a new fern-like plant from the Late Devonian of China

Background and Aims With the exception of angiosperms, the main euphyllophyte lineages (i.e. ferns sensu lato, progymnosperms and gymnosperms) had evolved laminate leaves by the Late Devonian. The evolution of laminate leaves, however, remains unclear for early-diverging ferns, largely represented by fern-like plants. This study presents a novel fern-like taxon with pinnules, which provides new insights into the early evolution of laminate leaves in early-diverging ferns.Methods Macrofossil specimens were collected from the Upper Devonian (Famennian) Wutong Formation of Anhui and Jiangsu Provinces, South China. A standard degagement technique was employed to uncover compressed plant portions within the rock matrix.Key Results A new fern-like taxon, Shougangia bella gen. et sp. nov., is described and represents an early-diverging fern with highly derived features. It has a partially creeping stem with adventitious roots only on one side, upright primary and secondary branches arranged in helices, tertiary branches borne alternately or (sub)oppositely, laminate and usually lobed leaves with divergent veins, and complex fertile organs terminating tertiary branches and possessing multiple divisions and numerous terminal sporangia.Conclusions Shougangia bella provides unequivocal fossil evidence for laminate leaves in early-diverging ferns. It suggests that fern-like plants, along with other euphyllophyte lineages, had independently evolved megaphylls by the Late Devonian, possibly in response to a significant decline in atmospheric CO₂ concentration. Among fern-like plants, planate ultimate appendages are homologous with laminate pinnules, and in the evolution of megaphylls, fertile organs tend to become complex.