Upatoia barnardii gen. et sp. nov., an araucarian pollen cone with in situ pollen from the Late Cretaceous (Santonian) of Georgia,USA

Upatoia barnardii gen. et sp. nov., a conifer pollen cone from the Late Cretaceous (Santonian) Eutaw Formation of Upatoi Creek, Georgia, USA, is known from lignified and fusainised mesofossils that preserve its three-dimensional structure. The cone consists of numerous helically arranged microsporophylls, each composed of a thin stalk and distal lamina. Three elongate pollen sacs are attached to the base of the lamina. Pollen grains isolated from the pollen sacs are relatively large (52 – 75 μm), spheroidal to ellipsoidal in outline, lack sacci, and have a thickened equatorial exine that is often strongly folded. Pollen of Upatoia barnardii indicates a close relationship to extant Araucariaceae. Microsporophylls of U. barnardii confirm suggestions from previous studies of fossil material that some Mesozoic Araucariaceae had only three pollen sacs per microsporophyll, in contrast to extant species that often have more than ten pollen sacs per microsporophyll.     

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.     

A NEW STRUCTURALLY PRESERVED PENNSYLVANIAN CORDAITEAN POLLEN ORGAN

Permineralized specimens of the pollen organ Gothania (Hirmer) consist of a primary axis bearing pollen cones in the axils of bracts that are four ranked. The bilaterally symmetrical primary axis consists of a uniform parenchymatous pith surrounded by up to 15 endarch-mesarch axile bundles. The cortex is two-parted and consists of an inner zone of subepidermal fibers. Bract traces arise from the ends of the ellipsoid stele. Traces to the cones are derived from the open ends of the stele, and at higher levels form a centrarch-medullated vascular system. Each pollen cone is constructed of up to 25 helically arranged scales, each vascularized by a single trace that may dichotomize. Scales are elongate and broad, and histologically composed of mesophyll parenchyma and fibrous layers. Stomata are restricted to the adaxial surface between rows of fibers. Up to 10 distal scales may be fertile, each with 4 elongate pollen sacs at the tip. Large monosaccate grains of the Felixipollenites-type are densely packed in each pollen sac. The well-preserved specimens of Gothania provide an opportunity to compare this genus with pollen cones assigned to the genus Cordaianthus, and to relate isolated plant organs to the Cordaitales.     

STEWARTIOTHECA GEN. N. AND THE NATURE AND ORIGIN OF COMPLEX PERMINERALIZED MEDULLOSAN POLLEN ORGANS

Stewartiotheca gen. n. is a bell-shaped, unisynangiate pollen organ with eccentric radial symmetry and a single series of about 80 pollen sacs. Infoldings that vary in depth occur circumferentially and extend from the periphery to a point off center. This position also marks the location of a sclerenchyma column (proximally) and a sclerenchyma-lined, conical hollow (distally) that opens onto the distal face of the organ. Plates of ground parenchyma extend inward from the outer covering of the organ at locations of infoldings, while similar plates with sclerenchyma strands occur between these locations. Pre-pollen of Monoletes type was released through distal longitudinal slitlike openings of the pollen sac faces toward the sclerenchymatous ground tissue plates. Vascular bundles entering the organ undergo repeated dichotomies, and lead to numerous bundles both in the cover (one per sac for those sacs that abut directly on cover tissue) and internally (one per pair of pollen sacs that lie opposite one another across the location of an infolding). The most complex permineralized medullosan pollen organs Sullitheca, Stewartiotheca, and Dolerotheca are considered to have evolved from a similar type of cup-shaped organ with a single ring of pollen sacs, broadly open distally, and with a central hollow. Circumferential infoldings of one organ of this type were involved in the origin of both Stewartiotheca and Sullitheca, while four similar organs, each showing infoldings non-circumferentially, fused to produce the Dolerotheca type organ (exemplified by D. formosa), a compound synangium.     

DEVELOPMENTAL ANATOMY OF SECRETORY CAVITIES IN THE MICROSPOROPHYLLS OF GINKGO BILOBA L.

Two to five secretory cavities develop in the hump region of the microsporophylls of Ginkgo biloba. A developing cavity is first recognized as a spherical pocket of large, densely cytoplasmic cells (central secretory cells) in the median portion of a microsporophyll primordium. These cells degenerate and a small cavity is formed which is filled with the contents of the degenerating cells. Flattened incurved cells (parietal secretory cells) develop around the disintegrating central secretory cells and slough off into the enlarging cavity. Thus, the cavities develop by lysigeny. A mature cavity is surrounded by senescent parietal secretory cells, scanty parenchyma, and a loosely fitting epidermis. Histochemical tests indicate the presence of lipid and pectic substances in the cavities. Previous reports on the morphological interpretation and possible function role of the cavities are discussed in the light of the present investigation.     

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.     

FERTILE CONIFEROPHYTE REMAINS FROM THE LATE TRIASSIC DEEP RIVER BASIN,NORTH CAROLINA

Seed cones (Compsostrobus neotericus gen. et sp. nov.), pollen cones, and vegetative remains of coniferophytes occur in Upper Triassic rocks of the Deep River Basin (Pekin Formation) of Central North Carolina. Seed cones have spatulate ovuliferous scales, each with two ovules and subtended by an elongated bract with an attenuate tip. Cuticle of seed cones resembles that of leaves on vegetative axes. Slender leaves are borne along two sides of the axis. Pollen cones have helically arranged microsporophylls, each with two abaxial sporangia bearing pollen grains of the Alisporites type. Seed cones, pollen cones, and vegetative remains suggest a coniferophyte very modern in aspect.     

HALLETHECA RETICULATUS GEN. ET SP. N.: A SYNANGIATE PENNSYLVANIAN PTERIDOSPERM POLLEN ORGAN

A new structurally preserved synangiate pollen organ is described from the upper Pennsylvanian (Mattoon Formation) of southeastern Illinois. The specimen of Halletheca reticulatus gen. et sp. nov. measures approximately 1.5 cm long by approximately 5.0 mm in diam, and consists of five elongate sporangial tubes equidistantly arranged around a solid central column, and embedded in a thin-walled ground tissue. The vascular system consists of five terete bundles characterized by scalariform tracheids. Sporangia are thick-walled and contain pollen of the Monoletes-type. Ultrastructural studies of the pollen grain wall show it to consist of a uniform network of muri which branch and re-unite to form small lumina. A comparison of the ultrastructure of the pollen grain wall of the new fructification is made with the wall organization found in similar pollen of Dolerotheca. Relationships between the new taxon and other presumed seed fern pollen organs differing in preservation mode are discussed.     

A new genus <Emphasis Type="Italic">Navipelta</Emphasis> (Peltaspermales,Pteridospermae) from the Permian/Triassic boundary deposits of the Moscow syneclise

A new genus of peltaspermalean ovuliferous organs Navipelta gen. nov. is described from the terrestrial deposits of the Nedubrovo locality (village of Nedubrovo, Vologda Region, Russia), belonging to the base of Vetlugian Group (Upper Permian-Lower Triassic). Data on the anatomy of the peltate bilateral ovuliferous organs are obtained for the first time. Vascular strands in the peltoid depart from that of a stalk and branch up to three times distally. Transfusion tissue around the vascular strands is well developed. The new genus had a system of radially arranged resin canals, broaden into large secretory cavities.     

Pollen Organs and Seeds with Decussosporites Brenner from Lower Cretaceous Potomac Group Sediments of Eastern USA

Microsporangiate structures, Brenneria potomacensis gen. et sp. nov., containing pollen grains similar to dispersed Decussosporites are described from the Lower Cretaceous (Barremian or Early Aptian?) Potomac Group localities at Drewry's Bluff and Dutch Gap on the James River southeast of Richmond, Virginia. These fossils provide the first megafossil evidence of plants producing Decussosporites-type pollen and contribute important new information on the structure and possible systematic affinities of this unique Mesozoic gymnosperm. The microsporangiate structure is composed of an axis with helically arranged synangiate microsporangiate units, each unit consisting of two laterally fused sporangia borne on a short stalk. The pollen grains are very small, bisaccate, distinctly striate (taeniate) and TEM shows that they have partly infilled sacci (quasisaccate). These grains represent the youngest occurrence of saccate, striate pollen, which has not been recorded previously from sediments younger than the earliest Jurassic. Fossil seeds (Brennerispermum potomacensis gen. et sp. nov.) from the same localities as Brenneria contain Decussosporites pollen in the micropyle, and are believed to have been produced by the same plant species. The seeds are small and unitegmic with a distinct megaspore membrane. The occurrence of seeds adhering together in groups indicates that they were borne in aggregations. The microsporangiate structures of Brenneria show some similarity to those of the ginkgophytes (Ginkgoales and Czekanowskiales), but there are substantial differences in the structure of seeds and pollen. The Decussosporites pollen grains together with morphology of the reproductive organs support a closer relationship of the Brenneria-plant to previously described “Mesozoic pteridosperms”.     

A male cone of Pseudofrenelopsis dalatzensis with in situ pollen grains from the Lower Cretaceous of Northeast China

A Classopollis-containing male cone found in close association with Pseudofrenelopsis dalatzensis from the Lower Cretaceous Dalazi Formation of Yanji Basin, eastern Jilin, China was studied using scanning electron microscopy and described as Classostrobus dalatzensis sp. nov. The small oval cone, borne on the top of a stalk (fertile short shoot), consists of helically arranged microsporophylls, each with a rhomboid and expanded distal head. The short shoot is divided into indistinct nodes and internodes with fine longitudinal striations. Cuticles of the microsporophyll and the internode of the short shoot are generally similar to Pseudofrenelopsis dalatzensis internode cuticles, all of them having papillate outer surfaces. Stomata are similar in structure and arrangement, with papillae of subsidiary cells overhanging the stomatal pit. Epidermal cells are rectangular or isodiametrical, each with a robust papilla on the periclinal wall. Hypodermal cells are present between the stomatal files. The internal structure of the in situ Classopollis pollen grains was studied in detail. Pollen grain is small, with thin sexine, poorly developed nexine and may be immature. This is the first record of in situ pollen grains Classopollis in China of which the internal structure is known in detail.     

Fossil floral structures of a basal angiosperm with monocolpate,reticulate-acolumellate pollen from the Early Cretaceous of Portugal

Distinctive monocolpate and reticulate-acolumellate pollen grains with a coarse, loosely attached reticulum have long been known as a conspicuous element of many palynological assemblages from the Early and mid-Cretaceous. These grains are now described in situ in staminate structures and on the surface of pistillate organs from two Early Cretaceous (Barremian or Aptian) mesofloras from Portugal (Vale de Agua and Buarcos). Staminate organs include a staminate axis with spirally arranged stamens and many isolated stamens. Stamens consist of a short filament, a dithecate, tetrasporangiate anther, and a short apical extension of the connective. Anther dehiscence is extrorse by longitudinal slits and in situ pollen is monocolpate, semi-tectate with a coarse, loosely attached reticulum composed of narrow muri with a spiny ornamentation. The infratectal layer of the pollen wall is thin, granular, and lacking columellae; and the foot layer is distinct. The endexine is thin, except under the aperture where it is thick. The pistillate organs are minute consisting of a simple unilocular ovary containing a single thin-walled seed. Associated with staminate and pistillate structures are many coprolites consisting almost exclusively of pollen grains of this distinctive type. The staminate and pistillate organs are not found in organic connection, and two new genera are established to accommodate the new floral structures: Pennistemon comprising the staminate structures and Pennicarpus comprising the pistillate structures. A new genus, Pennipollis, is also established for the dispersed grains, based on the type species Peromonolites peroreticulatus Brenner, since no appropriate genus has yet been described for these acolumellate grains. Features of the pollen grains strongly indicate affinity with members of the Alismatales and characters of the mesofossils also support this assignment. This is the first record of putative monocots in the early Cretaceous based on combined pollen and floral features.     

Exine ultrastructure of in situ peltasperm pollen from the Rhaetian of Germany and its implications

Morphology and exine ultrastructure of pollen grains of Triassic peltasperms have been studied for the first time. Pollen grains of Antevsia zeilleri from the Rhaetian of Germany are of the Cycadopites-type and monosulcate; the sculpturing is the same in the apertural and non-apertural areas. The proximal exine includes a row of lacunae covered by a solid, thick tectum and underlined by a foot layer. Pillars are hanging from the tectum between the lacunae. The exine is thinning to a homogeneous layer in the apertural region. The latter is bordered by thicker alveolate areas of the exine, in places resembling a saccus-like ultrastructure. The endexine includes white-line-centred lamellae. The exine ultrastructure is compared with that of pollen of Permian peltasperms. Although pollen types ascribed to Permian peltasperms are completely different in their general morphology, a transformation can be hypothesized by ultrastructural data from Permian Vesicaspora into Triassic Cycadopites extracted from pollen sacs of Antevsia. Comparison with Cycadopites of non-peltaspermalean (Ginkgoalean, Cycadophyte) and unknown affinities has been accomplished. The exine ultrastructure is distinctive enough to differentiate among peltaspermalean, cycadalean and bennettitalean Cycadopites; some ultrastructural features are shared with pollen of modern Ginkgo biloba. More ultrastructural data are needed as well as numerous sections of pollen grains are necessary to reveal original unchanged ultrastructure.     

Modified basal elements in Dicroidium fronds (Corystospermales)

We describe a distinct type of heteromorphic basal frond element in four species of the seed-fern foliage Dicroidium, based principally on a survey of plant-fossil collections from the Triassic of Antarctica. The modified foliar elements are conspicuously enlarged, and arise at wide angles and obliquely to the frond plane. Those of D. elongatum and D. crassinerve arise more or less directly from the petiole base; they are overall wedge- to fan-shaped with variably dissected margins and fan-shaped venation. Those of D. odontopteroides and D. dubium are (sub)circular, reniform, or obcordate, also with fan-shaped venation, or divided into narrow tongue-shaped segments with alethopteroid venation. The basal elements of some species commonly occur isolated. By analogy with comparable structures among other plant groups, we conclude that the basal elements represent a distinct, early leaf-ontogenetic architectural unit in the frond bauplan of Dicroidium, which provides an important additional character for a more accurate delimitation and systematic classification. Similar structures also occur on the corystosperm reproductive organs Umkomasia and Pteruchus. It appears that the basal elements were particularly common among high-latitude Dicroidium trees that flourished in a strongly seasonal light regime. We hypothesize that the modified elements may represent the initial foliar outgrowths during spring flush, ensuring a rapid re-initiation of sap flow and metabolic activity after the extended period of winter dormancy.     

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.     

New evidence of the reproductive organs of Glossopteris based on permineralized fossils from Queensland,Australia. II: pollen-bearing organ Ediea gen. nov

Ediea homevalensis H. Nishida, Kudo, Pigg & Rigby gen. et sp. nov. is proposed for permineralized pollen-bearing structures from the Late Permian Homevale Station locality of the Bowen Basin, Queensland, Australia. The taxon represents unisexual fertile shoots bearing helically arranged leaves on a central axis. The more apical leaves are fertile microsporophylls bearing a pair of multi-branched stalks on their adaxial surfaces that each supports a cluster of terminally borne pollen sacs. Proximal to the fertile leaves there are several rows of sterile scale-like leaves. The pollen sacs (microsporangia) have thickened and dark, striate walls that are typical of the Arberiella type found in most pollen organs presumed to be of glossopterid affinity. An examination of pollen organs at several developmental stages, including those containing in situ pollen of the Protohaploxypinus type, provides the basis for a detailed analysis of these types of structures, which bear similarities to both compression/impression Eretmonia-type glossopterid microsporangiate organs and permineralized Eretmonia macloughlinii from Antarctica. These fossils demonstrate that at least some Late Permian pollen organs were simple microsporophyll-bearing shoot systems and not borne directly on Glossopteris leaves.     

TUBULAR CAVITIES IN WHITE SNAKEROOT,EUPATORIUM RUGOSUM (ASTERACEAE)

Oil-filled schizogenous cavities 0.2-3.0 mm in length, each with a uniseriate epithelium, occur in all organs of white snakeroot (Eupatorium rugosum). Some epithelial cells swell, thus shrinking or occluding the cavity lumen. Foliar cavities form in staggered files in the midrib and in association with major veins. Cavities are progressively smaller and sparser in successive vein orders; the smallest ones develop as transformed bundle sheath cells in minor veins. Cavities in stems occur in irregular vertical files near vascular bundles in both cortex and pith. Leaf and stem cavities elongate variously, depending on when and where they form; in roots and floral organs, however, cavities are always short and sparse except in bracts, where they are common. Since each cavity remains discrete, we call these internal spaces ‘tubular cavities’ rather than ‘ducts’, which have generally been vaguely defined.     

Herb pollen representation in surface moss samples from mown meadows and pastures in western Norway

Grazed and mown vegetation types in western Norway were investigated with the aim of describing their modern pollen/vegetation relationships as an aid to the interpretation of fossil pollen diagrams. Pollen surface samples and vegetation data were obtained from 186 square metre plots within 39 different sites of 10×10 m. Scatter plots that show the relationship between pollen percentages and vegetation percentages are presented forTrifolium pratense-type,Trifolium rcpens-type,Lotus, Campanula-type,Succisa, Ranunculus acris-type,Cirsium-type, Asteraceae Cichorioideae,Achillea-type,Potentilla-type, Apiaceae,Rumex sect.Acetosa, Galium-type, Cyperaceae,Calluna, Plantago lanceolata and Poaceae. Pollen representation factors relative to Poaceae (R_rel) are calculated for 54 pollen taxa. Differences in the values from different geographical areas were found in the case of some taxa, due to either different genera or species being included in the pollen taxa and/or to the different representation of high pollen producers in the different regional vegetation types. Background pollen influences the estimates for taxa such asR. sect.Acetosa, P. lanceolata, Poaceae, Cyperaceae, andCalluna, and an extended R-value (ERV) model was used to investigate the magnitude of this pollen component. Groups of roughly similar pollen representation were identified and factors to convert pollen percentages to vegetation abundances are suggested.     

A survey of ontogeny pericarp features as contribution to the infratribal characterization of Myrteae (Myrtaceae)

With the aim of correlating the pericarp structure with current phylogenies of Myrteae, this study describes the ontogeny in five species included in five out of the six South American clades of the tribe. In these taxa, the outer and inner ovarian epidermis gives rise to the exocarp and the endocarp, respectively, both with 1 layer. In the mesocarp, derived from the ovarian mesophyll, secretory cavities are arranged into a circle just below the exocarp and near the endocarp in Campomanesia adamantium; only below the exocarp in Eugenia pitanga and Myrcia multiflora; more internally in Myrciaria cuspidata, and below the exocarp and throughout the mesophyll in Myrceugenia alpigena. The promising traits for phylogenetic studies in the group include: direction of elongation of pericarp layers, regions that develop most in relation to the circle of larger vascular bundles, differentiation of spongy and sclerenchymatous tissues and position of secretory cavities.