Plant Mesofossils Research Articles

Picking up the pieces: New charcoalified plant mesofossils (eophytes) from a Lower Devonian Lagerstӓtte in the Welsh Borderland, UK

The discovery of land plant spores with permanent tetrad and dyad configurations in Middle Ordovician rocks indicated a pioneering phase of phytoterrestrialisation that predated trilete spore-bearing tracheophytes. Limited studies on Upper Silurian and Lower Devonian examples suggest that the producers possessed characters of both tracheophytes and bryophytes, leading to the erection of a new clade of eophytes. Here we present an unprecedented comprehensive survey of hundreds of charcoalified eophytic mesofossils from a Lower Devonian (Lochkovian) Lagerstätte in the Welsh Borderland, UK, which reveals a wide range of branching in smooth axes with occasional stomata and conducting cells interpreted as predominantly involved in nutrient transport. Similar anatomy was discovered in fossils with usually fragmentary terminal sporangia containing evidence for permanent cryptospores. This raises the possibility that these small sporophytes of narrow axial diameter exhibited matrotrophy although the nature of the autotrophic gametophytes remains elusive. The sheer numbers of these tiny mesofossils in the fine-grained rocks at the locality indicate that these small plants were an important part of vegetation in Early Devonian times – a component that disappeared as vascular plants diversified and increased in size. Whether or not the pioneering Ordovician vegetation had exactly similar characteristics requires more information of gross morphology and anatomy of fossils in the intervening years.

A New Assemblage of Plant Mesofossils (Late Turonian–Middle Santonian; Upper Cretaceous) from the Tamagawa Formation, Kuji Group, in Northeastern Japan

A preliminary description is provided of a new assemblage of small, three-dimensional and charcoalified mesofossils from the Tamagawa Formation (late Turonian–middle Santonian; Upper Cretaceous) of the Kuji Group in northeastern Japan. The new mesofossils yield excellent structural details and include well-preserved circinate shoots of ferns together with conifer leafy-shoots, seeds and probable pollen cones, and variety of angiosperm fruits and seeds, including fruits of Cornales and seeds of Nymphaeales. The new mesofossil assemblage is complementary to the previously published macrofossil flora from the Kuji Group.

Plant mesofossils from the Late Cretaceous Klikov Formation, the Czech Republic

Late Cretaceous mesofossils are described from the Zliv-Řídká Blana locality in the South Bohemian Basins, the Czech Republic. Angiosperm remains dominate the fossil assemblage both in terms of taxonomic diversity and quantitatively, with about 65 different species based on about 1,000 specimens of flowers, fruits and seeds. There are surprisingly few nonangiosperm species in the flora, with only four specimens assigned to bryophytes, ferns and conifers. There are no megaspores of Selaginellales or Salviniales, which are otherwise common in many Cretaceous mesofossil floras. Among angiosperms, flowers and fruits assigned to the Normapolles group (Fagales) and to the Ericales are particularly prominent. In systematic composition as well as general organization and size of the angiosperm reproductive organs, the Zliv-Řídká Blana mesofossil flora is comparable to other Late Cretaceous mesofossil floras collected from various regions of Laurasia. In addition to the plant remains, the fossil assemblage also includes insect eggs and coprolites.

Dispersed plant mesofossils from the Permian of Wuda, Inner Mongolia, Taiyuan Formation, China

A coal sample from the Lower Permian Taiyuan Formation (Wuda locality, Inner Mongolia, China) was macerated. It yielded two cuticle fragments and many fragments of conducting tissue. One cuticle fragment shows strongly corroded polygonal cells belonging either to a pteridosperm or a cycad. The second fragment is an abaxial cordaitalean cuticle with papillate tetragonal cells and can be compared to Cordaites neimengensis LIU et al. 1998. The conducting tissue are represented by biseriate to quadriseriate tracheid pitting that is typical for cordaitaleans.

Palaeontology of the upper Turonian paralic deposits of the Sainte-Mondane Formation, Aquitaine Basin, France

The upper Turonian lignite deposits of Sainte-Mondane, Dordogne (Aquitaine Basin, SW France), consist of clays bearing translucent, orange to red, amber micrograins. The amber exhibits different types of microbial inclusions. The clays contain several conifers including the genera Brachyphyllum, Frenelopsis and Glenrosa, and a few leaf fragments of eudicot angiosperms. Among the plant meso-fossils the occurrence of Costatheca, Spermatites and abundant, diverse megaspores, including species of Ariadnaesporites, Bacutriletes, Echitriletes, Erlansonisporites, Maexisporites, Minerisporites and Verrutriletes, is noteworthy. Pollen grains of the Normapolles group are important components of the palynomorph assemblage. The clays were deposited in a calm, estuarine or lagoonal, muddy environment. The overlying lignitic sands contain large fossil wood pieces of the conifer Agathoxylon, small solitary corals, fragmentary oysters and pectinids, echinoid spines, a few teeth of marine selachians and bony fishes, but no amber is present. These sands were deposited in a high-energy coastal marine environment.

On the Interpretation of Fossil Nuclei

Although organelle preservation in plant fossils is not novel and well-preserved plant mesofossils have contributed greatly to the understanding of plant evolution, subcellular structures are still a rarity in plant mesofossils. Although it is not easy to explore subcellular structures in plant fossils, related attempts are frequently seen. Among them, some false interpretation requires further inspection. To shed more light on this issue, here I studied Cretaceous charcoalified mesofossils from USA, using LM (light microscopy), SEM (scanning electron microscopy) and TEM (transmission electron microscopy) technologies. My conclusion shows that not all publications reflect the truthful existence of nuclei in plant fossils, and this study may provide a reference for the future research.

Analysis of alkyl lipids bound in sediment and plant mesofossils from the Cretaceous Futaba Group: Possible formation mechanism of organic matter-concentrated layer

Analysis of alkyl lipids bound in sediment and plant mesofossils from the Cretaceous Futaba Group: Possible formation mechanism of organic matter-concentrated layer

Dispersed plant mesofossils from the Middle Mississippian of eastern Germany: Bryophytes, pteridophytes and gymnosperms

Plant remains with organic-matter preservation are uncommon in the Mississippian due to the general rareness of Mississippian terrestrial deposits. Moreover, the fossils are often strongly affected by post-sedimentary processes. However, bulk-macerated samples of the upper Visean of Chemnitz-Glösa (Germany) contain several well-preserved dispersed organic remains including cuticle fragments. Even though it is difficult to assign these remains to specific taxa and they probably represent only part of the vegetation, they provide important information on Mississippian floras. The cuticles are assigned to sphenopsids and gymnosperms. In addition, several bryophyte remains were found; nine morphologically different types are recognised, which represent at least five different taxa. This is remarkable because only a few bryophytes have been recorded from the Carboniferous to date.

Palynomorphs of the Normapolles group and related plant mesofossils from the Iharkút vertebrate site, Bakony Mountains (Hungary)

Abstract Palynological and paleobotanical investigation of bonebeds and other strata of the Csehbanya Formation from the vertebrate locality at Iharkut (Bakony Mts, Hungary) reveals well-preserved Santonian palynological assemblages dominated by the Normapolles group, with a minor component consisting of other angiosperm pollen, some gymnosperm pollen, and spores. Eleven species of Normapolles-type pollen grains belonging to seven genera and fruit remains of a new taxon, Sphaeracostata barbackae gen. et sp. nov., are described. The new species is very abundant in the material, represented by ca. 1000 specimens. The genus Caryanthus Friis and an unnamed form previously reported from Haţeg by Lindfors et al. (2010) are also present. Plants producing Normapolles-type pollen grains diversified during the Late Cretaceous, with a bloom in the Santonian. The palynostratigraphy of the Upper Cretaceous terrestrial sediments in the studied region is based on Normapolles-related species. The studied assemblage is as...

183 Preliminary report on new plant mesofossils from the Klikov Formation, Cretaceous, Czech Republic

183 Preliminary report on new plant mesofossils from the Klikov Formation, Cretaceous, Czech Republic

Dispersed lycopsid cuticles from the Mississippian of Chemnitz (Saxony, Germany), and their implications for the affinity of the putative earliest conifer and for lycopsid palaeoecology

The leaf cuticles of lycopsids are generally thought to be very thin and have limited preservation potential. In addition the preservation of Mississippian cuticles is often hampered by thermal alteration. However, newly discovered, exceptionally well preserved dispersed cuticle fragments from the Mississippian of Germany show remarkable similarity to the cuticles of some fossil and extant lycopsids and are thus interpreted as lycopsid cuticles. The fragments represent two different cuticle types, which are both comparably robust and show different kinds of ornamentation. At least one cuticle type is suggested to derive from leaves. These discoveries indicate that Palaeozoic lycopsid cuticles had a greater preservation potential than previously thought. In addition, we suggest that plant mesofossils that have been described as the world's oldest conifer Swillingtonia Scott et Chaloner from the Duckmantian of England may represent lycopsid remains.

Preliminary account of plant mesofossils from the Maastrichtian Budurone microvertebrate site of the Haţeg Basin, Romania

The Maastrichtian Budurone mesofossil flora includes 19 different types of angiosperm fruits and seeds. All fruits and seeds are small, 0.6–2.6 mm long and 0.5–1.9 mm broad, with calculated fruit volume ranging between 0.08 and 3.59 mm 3 and seed volume between 0.08 and 0.79 mm 3. The fossils show great similarity with other Cretaceous angiosperm fossils regarding their dimension and organisation. However, comparison with other Late Cretaceous and Early Cenozoic floras from Europe shows that surprisingly few of the Budurone fossils can be assigned to taxa previously described from Europe, and so far only a few taxa appear to be shared with other mesofossil floras. This indicates that the Budurone flora may have been isolated from the other European floras or represents a different kind of depositional environment. Fruits are mainly indehiscent nuts and drupes, and seeds are mostly anatropous without special ornamentation indicating a mixture of biotic and unassisted dispersal. This together with the small size of the fruits and seeds indicates that the Budurone plants grew in typical Late Cretaceous open vegetation perhaps under a seasonally dry climate.

Bennettitales from the Grisethorpe Bed (Middle Jurassic) at Cayton Bay, Yorkshire, UK

Middle Jurassic fossil plants from the Grisethorpe Bed at Cayton Bay and Grisethorpe Bay, Yorkshire, UK, are preserved in a soft claystone, and plant mesofossils recovered by sieving reveal excellent details of external structure. Studies of these mesofossils complement previous work on macrofossils from the Grisethorpe Bed and allow the plant fossils in this classic flora to be studied in a similar way to those preserved in Cretaceous mesofloras. Bennettitales, a key group in discussions of how angiosperms may be related to other seed plants, are especially well represented among mesofossils from the Grisethorpe Bed. Abundant bennettitalean leaves, scale leaves, and fragments of pollen and ovulate organs provide new information on these extinct plants. In particular, a specimen of Williamsoniella coronata (presumed aborted) shows only weak differentiation between interseminal scales and ovules and provides further evidence of homology between these structures.

Phase-contrast X-ray microtomography links Cretaceous seeds with Gnetales and Bennettitales

Over the past 25 years the discovery and study of Cretaceous plant mesofossils has yielded diverse and exquisitely preserved fossil flowers that have revolutionized our knowledge of early angiosperms, but remains of other seed plants in the same mesofossil assemblages have so far received little attention. These fossils, typically only a few millimetres long, have often been charred in natural fires and preserve both three-dimensional morphology and cellular detail. Here we use phase-contrast-enhanced synchrotron-radiation X-ray tomographic microscopy to clarify the structure of small charcoalified gymnosperm seeds from the Early Cretaceous of Portugal and North America. The new information links these seeds to Gnetales (including Erdtmanithecales, a putatively closely related fossil group), and to Bennettitales--important extinct Mesozoic seed plants with cycad-like leaves and flower-like reproductive structures. The results suggest that the distinctive seed architecture of Gnetales, Erdtmanithecales and Bennettitales defines a clade containing these taxa. This has significant consequences for hypotheses of seed plant phylogeny by providing support for key elements of the controversial anthophyte hypothesis, which links angiosperms, Bennettitales and Gnetales.

Charcoal in the Early Devonian: A wildfire-derived Konservat–Lagerstätte

Anatomically preserved Earliest Devonian plant mesofossils from a stream section in the Welsh Borderland are quantitatively demonstrated to be charcoal, and are the pyrolysis products of ancient wildfires. These wildfire events preserved a diversity of plants and a level of anatomical detail that is unrivalled by other Lochkovian localities, and as a result have provided important insights into the early evolution of land plants. This diverse assemblage, which displays exceptional preservation of volatile non-mineralised tissues, is an example of instantaneous fossilization and the locality is proposed as a Konservat–Lagerstätte. It is the first record of a wildfire-derived Lagerstätte and as such, expands the diversity of recognized conservation traps.

Late Cretaceous plant mesofossils from Table Nunatak, Antarctica

Charred and structurally preserved plant remains have been recovered from Late Cretaceous strata from Table Nunatak, Antarctica. The mesofossils, up to a few mm in length, represent structures from lycopods (megaspores), ferns (circinate rachides), conifers (wood, leaves, leafy shoots, pollen cones, microsporophylls, ovulate cone scales, seeds), and angiosperms (leaves, flowers, fruits, seeds). This work focuses on the megaspores, microsporophylls, ovulate cone scales and vegetative structures. The mesofossils were extracted from unconsolidated sediments deposited in a shallow-marine environment during the late Santonian (ca. 83 Ma). The Table Nunatak assemblage is the only known Cretaceous mesofossil assemblage with charred plant parts from Antarctica, and one of only a few from the Southern Hemisphere as a whole. It represents the remains of forests that grew at palaeolatitudes of 65°S, during a time in the Cretaceous in which high latitude environments experienced warm temperate climates in a global greenhouse world.