Extinct Gymnosperms Research Articles

Possible long-proboscid insect pollinators from the Early Permian of Russia

Insect pollination is one of the hallmarks of flowering plants.1 Bees, moths, flies, and some other pollinators evolved elongate siphonate mouthparts for sucking concealed nectar and occasionally other liquids.2 However, it is clear from the fossil record that insects with similar adaptations appeared long before the mid-Cretaceous radiation of angiosperms. These insects most probably used their proboscis to reach pollination drops and other sugary fluids that were hidden in the cones of extinct gymnosperms, pollinating them in the process.3-6 The vast majority of these gymnosperm-associated long-proboscid insects have been reported from the Middle Jurassic to the Early Cretaceous, i.e., the time interval that immediately predated the advent of flowering plants.7 By contrast, the Paleozoic stage of the co-evolution between long-proboscid insect pollinators and plants has remained poorly understood. Here, we report a putative pollination mutualism involving long-proboscid holometabolous insects (Panorpida: Protomeropidae) from the Early Permian of Russia (ca. 283-273 Ma). Their elongate mouthparts have very similar morphology to those of some present-day nectarivorous Coleoptera and Hymenoptera and probably served to imbibe micropylar secretions from the semi-closed ovulate organs of the gymnosperms of a peltaspermalean affinity that have been found in the same locality. This is the earliest record of insects with siphonate-like mouthparts, which could indicate that the complex interactions between pollinators and gymnosperms predate the first flowering plants by over 100 Ma.

Comparing structure and biomechanics of extant Carica papaya and Ochroma pyramidale stems allows re-evaluating the functional morphology of the fossil ‘seed fern’ Lyginopteris oldhamia

This study aims at assessing the mechanical importance of the conspicuous sclerenchymatous ‘Dictyoxylon’ cortex of the extinct gymnosperm Lyginopteris oldhamia by comparing the latter to the extant angiosperms Carica papaya and Ochroma pyramidale, both possessing a cortex composed of mechanically relevant wedges of phloem fibres. Our studies show that the anatomical structure of the cortex in L. oldhamia is very similar to C. papaya and O. pyramidale and that comparable variations occur in the cortex of L. oldhamia as found in C. papaya and O. pyramidale when reorienting oblique stems or branches. This similarity in (adaptable) anatomical structures leads to the conclusion that the cortex of L. oldhamia was also able to readjust the orientation of stem and branches as a reaction to mechanical stress, shown for C. papaya and O. pyramidale. This finding supports the hypothesis that L. oldhamia stems might well have been self-supporting in (very) young ontogenetic stages and became semi-self-supporting or climbing in older ontogenetic stages.

Simulation of exine patterns by self-assembly

New experimental modeling of exine has been undertaken to verify general ideas on the participation of self-assembly processes in sporoderm development. Our aim was to confirm our hypothesis that a considerable part of the developmental processes is the unfolding sequence of self-assembling micelle mesophases and their aggregates in the colloidal system of the microspore periplasmic space. Strong support for this hypothesis would be experimental modeling of sporoderm-like patterns in vitro. We used surface-active substances for the preparation of colloidal mixtures: glycoproteins, lipopolysaccharides and natural sporopollenin precursors—phenolics and fatty acids. In vitro conditions, when the influence of the genome is absent, a number of patterns, mimicking separate layers of sporoderm—ectexine, endexine and supratectal ornamentations—at different development stages have been obtained and studied with TEM. Simulations, appearing as scattered and clustered spherical micelles and columns of spherical micelles mimic sporoderm development at young tetrad stages in most species. A layer of semi-fused spherical micelles, transient to cylindrical micelles, simulates the columellate primexine at the middle tetrad stage. The simulation with laminate micelles mimics endexine lamellae with central white lines. More complex simulations such as spongy, perforated and stalactite-like patterns, mimicking exine layers of some basal and advanced angiosperms and extinct gymnosperms, were also obtained. Some simulations bear spine-like and gemma-like structures on the surface, mimicking ornamentation of natural sporoderm. Our results show that a considerable part of the development of the exine takes place through self-assembly.

New long-proboscid lacewings of the mid-Cretaceous provide insights into ancient plant-pollinator interactions.

Many insects with long-proboscid mouthparts are among the pollinators of seed plants. Several cases of the long-proboscid pollination mode are known between fossil insects (e.g., true flies, scorpionflies, and lacewings) and various extinct gymnosperm lineages, beginning in the Early Permian and increasing during the Middle Jurassic to Early Cretaceous. However, details on the morphology of lacewing proboscides and the relevant pollination habit are largely lacking. Here we report on three lacewing species that belong to two new genera and a described genus from mid-Cretaceous (Albian-Cenomanian) amber of Myanmar. All these species possess relatively long proboscides, which are considered to be modified from maxillary and labial elements, probably functioning as a temporary siphon for feeding on nectar. Remarkably, these proboscides range from 0.4–1.0 mm in length and are attributed to the most diminutive ones among the contemporary long-proboscid insect pollinators. Further, they clearly differ from other long-proboscid lacewings which have a much longer siphon. The phylogenetic analysis indicates that these Burmese long-proboscid lacewings belong to the superfamily Psychopsoidea but cannot be placed into any known family. The present findings represent the first description of the mouthparts of long-proboscid lacewings preserved in amber and highlight the evolutionary diversification of the ancient plant-pollinator interactions.

Long-Proboscid Flies as Pollinators of Cretaceous Gymnosperms

The great evolutionary success of angiosperms has traditionally been explained, in part, by the partnership of these plants with insect pollinators. The main approach to understanding the origins of this pervasive relationship has been study of the pollinators of living cycads, gnetaleans, and basal angiosperms. Among the most morphologically specialized living pollinators are diverse, long-proboscid flies. Early such flies include the brachyceran family Zhangsolvidae, previously known only as compression fossils from the Early Cretaceous of China and Brazil. It belongs to the infraorder Stratiomyomorpha, a group that includes the flower-visiting families Xylomyidae and Stratiomyidae. New zhangsolvid specimens in amber from Spain (ca. 105 mega-annum [Ma]) and Myanmar (100 Ma) reveal a detailed proboscis structure adapted to nectivory. Pollen clumped on a specimen from Spain is Exesipollenites, attributed to a Mesozoic gymnosperm, most likely the Bennettitales. Late Mesozoic scorpionflies with a long proboscis have been proposed as specialized pollinators of various extinct gymnosperms, but pollen has never been observed on or in their bodies. The new discovery is a very rare co-occurrence of pollen with its insect vector and provides substantiating evidence that other long-proboscid Mesozoic insects were gymnosperm pollinators. Evidence is thus now gathering that visitors and probable pollinators of early anthophytes, or seed plants, involved some insects with highly specialized morphological adaptations, which has consequences for interpreting the reproductive modes of Mesozoic gymnosperms and the significance of insect pollination in angiosperm success.

371 3D observation of fruit-like organs of two extinct gymnosperm groups from the Late Cretaceous of Hokkaido using MXCT

371 3D observation of fruit-like organs of two extinct gymnosperm groups from the Late Cretaceous of Hokkaido using MXCT

358 3D reconstruction of a coleopteran pupa in a reproductive organ of extinct gymnosperm from the Upper Cretaceous of Hokkaido, Japan

358 3D reconstruction of a coleopteran pupa in a reproductive organ of extinct gymnosperm from the Upper Cretaceous of Hokkaido, Japan

The Pollination of Mid Mesozoic Seed Plants and the Early History of Long-proboscid Insects1,2,3

Abstract A defining event for Mesozoic plant-pollinator interactions is the angiosperm radiation, which extended the reach of pollinating insects during the Early Cretaceous in a brief interval of geologic time. Recent evidence indicates that events beginning in the Early Permian and increasing during the Middle Jurassic provided repeated opportunities for insect feeding on pollen, pollination drops, and reproductive tissues of extinct gymnosperm lineages. Pollination was an associated development. Studies on the detailed mouthpart structure of several fluid-feeding insect lineages indicate targeting of certain tubular features of gymnosperm ovulate organs that previously were considered anomalous and difficult to interpret. One mouthpart type, the long-proboscid condition, consists of elongate, tubular (siphonate) proboscises that accessed surface fluids powered by a cibarial pump, often assisted with a distal proboscis sponging organ. These proboscises were received in ovulate organs through often intri...

A probable pollination mode before angiosperms: Eurasian, long-proboscid scorpionflies.

The head and mouthpart structures of 11 species of Eurasian scorpionflies represent three extinct and closely related families during a 62-million-year interval from the late Middle Jurassic to the late Early Cretaceous. These taxa had elongate, siphonate (tubular) proboscides and fed on ovular secretions of extinct gymnosperms. Five potential ovulate host-plant taxa co-occur with these insects: a seed fern, conifer, ginkgoopsid, pentoxylalean, and gnetalean. The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms. All three scorpionfly families became extinct during the later Early Cretaceous, coincident with global gymnosperm-to-angiosperm turnover.

Morphological and molecular phylogenetic context of the angiosperms: contrasting the 'top-down' and 'bottom-up' approaches used to infer the likely characteristics of the first flowers

Recent attempts to address the long-debated 'origin' of the angiosperms depend on a phylogenetic framework derived from a matrix of taxa versus characters; most assume that empirical rigour is proportional to the size of the matrix. Sequence-based genotypic approaches increase the number of characters (nucleotides and indels) in the matrix but are confined to the highly restricted spectrum of extant species, whereas morphology-based approaches increase the number of phylogenetically informative taxa (including fossils) at the expense of accessing only a restricted spectrum of phenotypic characters. The two approaches are currently delivering strongly contrasting hypotheses of relationship. Most molecular studies indicate that all extant gymnosperms form a natural group, suggesting surprisingly early divergence of the lineage that led to angiosperms, whereas morphology-only phylogenies indicate that a succession of (mostly extinct) gymnosperms preceded a later angiosperm origin. Causes of this conflict include: (i) the vast phenotypic and genotypic lacuna, largely reflecting pre-Cenozoic extinctions, that separates early-divergent living angiosperms from their closest relatives among the living gymnosperms; (ii) profound uncertainty regarding which (a) extant and (b) extinct angiosperms are most closely related to gymnosperms; and (iii) profound uncertainty regarding which (a) extant and (b) extinct gymnosperms are most closely related to angiosperms, and thus best serve as 'outgroups' dictating the perceived evolutionary polarity of character transitions among the early-divergent angiosperms. These factors still permit a remarkable range of contrasting, yet credible, hypotheses regarding the order of acquisition of the many phenotypic characters, reproductive and vegetative, that distinguish 'classic' angiospermy from 'classic' gymnospermy. The flower remains ill-defined and its mode (or modes) of origin remains hotly disputed; some definitions and hypotheses of evolutionary relationships preclude a role for the flower in delimiting the angiosperms. We advocate maintenance of parallel, reciprocally illuminating programmes of morphological and molecular phylogeny reconstruction, respectively supported by homology testing through additional taxa (especially fossils) and evolutionary-developmental genetic studies that explore genes potentially responsible for major phenotypic transitions.

Taxonomic turnover and abundance in Cretaceous to Tertiary wood floras of Antarctica: implications for changes in forest ecology

Based on the temporal distribution, abundance, and taxonomic composition of wood floras, four phases of vegetation development are recognized through the Cretaceous to Early Tertiary of the Antarctic Peninsula: (1) Aptian to Albian communities dominated by podocarpaceous, araucarian, and minor taxodiaceous/cupressaceous conifers with rare extinct gymnosperms ( Sahnioxylon). (2) Progressive replacement of these communities in ?Cenomanian to Santonian times by angiosperms, most without modern analogues. (3) Increasing dominance of angiosperms becoming important both in terms of diversity and abundance towards the mid-Late Cretaceous. (4) Modernization of the flora during the Campanian to Maastrichtian with the extinction of earlier forms, appearance of the Nothofagaceae and diversification of associated elements. These patterns broadly follow trends seen in the leaf and palynological record but with some important differences. During the Cretaceous, conifer composition undergoes a change whereby Phyllocladoxylon-type woods increase relative to the older Podocarpoxylon forms. During the Paleocene to Eocene period, a marked extinction in wood types occurs associated with an increase in the abundance of nothofagaceous wood. Detailed examination of wood abundance and distributions from sections within Maastrichtian and Paleocene formations points to strong environmental control on taxonomic compositions. Similar differences are encountered when comparing coeval floras from different geographic regions and palaeoenvironments.

Discovery of organic connection ofChiropteris Kurr andNystroemia Halle from Early Permian of western Henan, China

Nystroemia reniformis (Kawasaki) comb. nov. is proposed based on specimens showing organic connections betweenChiropteris reniformis Kawasaki andNystroemia pectiniformis Halle from the Lower Permian of Dengfeng in Henan. Vegetative leaf has a long petiole, reniformed, cordate at the base, entire or slightly undulate at the margin; veins are fine, bifurcating repeatedly and finally becoming reticulate and forming polygonal or rhomboidal meshes. Fertile shoot arises from bract axils. The form of the bract is identical to that of a vegetative leaf. Ovuliferous organ arises from the axil of leafy organ, or in other case, both ovuliferous and leafy organs irregularly arise from the axis of the fertile shoot respectively. Numerous bicornute platyspermic seeds are arranged in two rows, obconical, with micropyle pointing upwards. It may represent a new extinct gymnosperms.

Gymnosperm woods from the Cretaceous (mid-Aptian) Cerro Negro Formation, Byers Peninsula, Livingston Island, Antarctica: the arborescent vegetation of a volcanic arc

Silicified gymnosperm trunks usually more than 30cm in diameter and several metres in length occur abundantly in the lower part of the mid-Aptian Cerro Negro Formation, which crops out on Byers Peninsula, Livingston Island, northern Antarctic Peninsula. These fossil woods are found within silicic ignimbrites, tuffs and lapilli-tuffs interpreted as the product of hot pyroclastic flows, and in silicic and andesitic conglomerates interpreted as fluvially-reworked volcanic sediments. A detailed quantitative study of the wood taxonomy has revealed the presence of three form genera, Araucarioxylon,Podocarpoxylon , and Sahnioxylon. The former two genera represent the conifer families Araucariaceae and Podocarpaceae respectively and the latter probably belongs to the extinct gymnosperm order Bennettitales. These wood genera represent the remains of the arborescent vegetation, which grew on the margins of an active pyroclastic volcanic cone near the edge of the mid-Cretaceous Antarctic Circle (palaeolatitude 62°S).

Functional groups and elemental analyses of cuticular morphotypes of Cordaites principalis (Germar) Geinitz, Carboniferous Maritimes Basin, Canada

Well-preserved cuticles were isolated from Cordaites principalis (Germar) Geinitz leaf compressions, i.e., foliage from extinct gymnosperm trees Coniferophyta: Order Cordaitales. The specimens were collected from the Sydney, Stellarton and Bay St. George subbasins of the once extensive Carboniferous Maritimes Basin of Atlantic Canada. Fourier transformation of infrared spectra (FTIR) and elemental analyses indicate that the ca. 300–306-million-year-old fossil cuticles share many of the functional groups observed in modern cuticles. The similarities of the functional groups in each of the three cuticular morphotypes studied support the inclusion into a single cordaite-leaf taxon, i.e., C. principalis (Germar), confirming previous morphological investigations. Vitrinite reflectance measurements on coal seams in close proximity to the fossil-bearing sediments reveal that the Bay St. George sample site has the lowest thermal maturity, whereas the sites in Sydney and Stellarton are more mature. IR absorption and elemental analyses of the cordaite compressions corroborate this trend, which suggests that the coalified mesophyll in the leaves follows a maturation path similar to that of vitrinite. Comparison of functional groups of the cordaite cuticles with those from certain pteridosperms previously studied from the Sydney Subbasin shows that in the cordaite cuticles highly conjugated C–O (1632 cm −1) bands dominate over carbonyl stretch that characterizes the pteridosperm cuticles. The differences demonstrate the potential of chemotaxonomy as a valuable tool to assist distinguishing between Carboniferous plant–fossil groups.

Zoidogamy in fossil gymnosperms

This year is the centenary of the surprising discovery in 1896 of zoidogamy in extant cycadophytes and Ginkgo. But by coincidence, also in the same year, the concept of prepollen was introduced. The morphology of prepollen was considered justification for the probable production of motile antherozoids in extinct gymnosperms. In this paper, the history of the prepollen concept is briefly outlined. It is emphasized that, in addition to well-known examples in pteridosperms and cordaitaleans, a prepollen condition also occurred among late Paleozoic conifers.

Cretaceous coleopteran larva fed on a female fructification of extinct gymnosperm

A fossil coleopteran larva was found in a permineralized female fructification of a new extinct gymnosperm from the Late Cretaceous of Japan. The fossil provides the firstin situ evidence that the insects used some gymnosperm fructification as foods as well as pupation sites before they started using angiosperm fruits.

ThePentoxylonplant

The various dispersed organs belonging to thePentoxylonplant viz.Pentoxylon(stem),Nipaniophyllum(leaf),Sahnia(male flower) andCarnoconites(female cone) have been studied in detail. Apart from the long shoots (type 1 shoots), the plant bore three different kinds of short shoots: the thick woody short shoots, each with a broadly conical head (type 2 shoots); the slender parenchymatous short shoots (type 3 shoots); and the slightly thicker parenchymatous short shoot (type 4 shoot) terminating in aSahniaflower. In addition to the well knownNipaniophyllum raoileaves a second species,N. hobsoniisp. nov., is recognized. InSahniathe sporangiophores were borne on a collar-like structure formed by the raised margin of the receptacle. The broadly conical head of the thick woody short shoot (type 2 shoot) might be the basis of the cone-bearing branchlets ofCarnoconitesfruits. The seeds ofCarnoconitesare spirally arranged rather than being in longitudinal rows as previously suggested.Pentoxylonwas probably a shrubby plant which grew beside water. It sent up erect branched leafy shoots which after a few seasons of growth flopped onto the ground or on other stems, making a thicket. Although the stem,Pentoxylon, resemblesMedullosaandRhexoxylonanatomically, the reproductive parts of the plant,SahniaandCarnoconites, are unlike those of any group of gymnosperms. ThePentoxylonplant is accordingly regarded as an extinct gymnosperm of unknown affinity.Nipanioxylon guptaihas previously been regarded as related toPentoxylon, but its holotype is believed to be a conifer and has nothing to do with thePentoxylonplant.

A COMPARATIVE STUDY OF THE PRIMARY VASCULAR SYSTEM OF CONIFERS. III. STELAR EVOLUTION IN GYMNOSPERMS

This paper includes a survey of the nature of the primary vascular system in a large number of extinct gymnosperms and progymnosperms. The vascular system of a majority of these plants resembles closely that of living conifers, being characterized, except in the most primitive forms which are protostelic, by a eustele consisting of axial sympodial bundles from which leaf traces diverge. The vascular supply to a leaf originates as a single trace with very few exceptions. It is proposed that the eustele in the gymnosperms has evolved directly from the protostele by gradual medullation and concurrent separation of the peripheral conducting tissue into longitudinal sympodial bundles from which traces diverge radially. A subsequent modification results in divergence of traces in a tangential plane. The closed vascular system of conifers with opposite and whorled phyllotaxis, in which the vascular supply to a leaf originates as two traces which subsequently fuse, is considered to be derived from the open sympodial system characteristic of most gymnosperms. This hypothesis of stelar evolution is at variance with that of Jeffrey which suggests that the eustele of seed plants is derived by the lengthening and overlapping of leaf gaps in a siphonostele followed by further reduction in the resultant vascular bundles. This study suggests strongly that the “leaf gap” of conifers and other extant gymnosperms is not homologous with that of siphonostelic ferns and strengthens the validity of the view that Pterop‐sida is an unnatural group. It supports the position that gymnosperms have evolved from progymnosperms rather than from ferns, and the inclusion of ferns and gymnosperms in separate subdivisions or divisions.

Experimental Investigations on Birch and Oak

1. Experimental investigations are of interest in connection with woody plants both from a general biological point of view, and also from the standpoint of plant pathology. They are also of interest because they suggest the possibility of producing ornamental woods experimentally. 2. Three types of rays, aggregate, compound, and diffuse, which persist contemporaneously in Casuarina, are characteristic of angiospermous trees. The aggregate seems to be the more primitive one, from which the diffuse and compound have been derived by different processes of evolution. 3. Wound reactions in woody forms must be considered with reference to the conservative regions, the seedling structures, and fossil record, because only those structures occurring as a consequence of injury which have parallel conditions in these parts can be regarded as true reversions. 4. Work on living and extinct Gymnosperms has established certain principles on the basis of which experimental investigations in angiospermous woods may proceed a priori. 5. All reactions following wounding are not true reversions. In general extreme hypertrophy is not favorable to reversion. 6. The details of wound reaction in the birch and oak are different. In the birch the wound cap is large, the hypertrophy being very marked. As a consequence the traumatic or reversionary features are not found in this region, but in that part of the cylinder opposite the wound. 7. Abies recalls marginal ray tracheids as a consequence of wounding. These are found in the regions remote from the wound and parallel the situation obtaining in the birch. On the other hand, the mode of appearance of traumatic resin canals is similar to that of the aggregate rays resulting from injury to northern oaks, as the reversionary resin canals occur in the immediate region of the wound cap. 8. In the oaks the wound cap is small and does not show hypertrophy to any marked extent. Correlated within this is, reversionary features appear in the wound cap proper, in contrast to the birches.

Influence of Environment on Sexual Expression in Hemp

1. Experimental investigations are of interest in connection with woody plants both from a general biological point of view, and also from the standpoint of plant pathology. They are also of interest because they suggest the possibility of producing ornamental woods experimentally. 2. Three types of rays, aggregate, compound, and diffuse, which persist contemporaneously in Casuarina, are characteristic of angiospermous trees. The aggregate seems to be the more primitive one, from which the diffuse and compound have been derived by different processes of evolution. 3. Wound reactions in woody forms must be considered with reference to the conservative regions, the seedling structures, and fossil record, because only those structures occurring as a consequence of injury which have parallel conditions in these parts can be regarded as true reversions. 4. Work on living and extinct Gymnosperms has established certain principles on the basis of which experimental investigations in angiospermous woods may proce...