Abstract

An anatomically preserved fossil conifer seed cone has been discovered near Ono, California, providing additional evidence for the diversification of Pinaceae during the Aptian Stage of the Early Cretaceous. The specimen was measured and photographed, and then serial anatomical thin sections were prepared by the cellulose acetate peel technique. Selected peels were mounted on microscope slides, viewed, and photographed with transmitted light microscopy. Structure of the seed cone is similar to that of living and extinct representatives of the Pinaceae in the occurrence of helically arranged and imbricating foliate bract/scale complexes consisting of a small bract that subtends an ovuliferous scale bearing two inverted winged seeds on the adaxial surface. However, details of bract/scale complex vasculature, a wing that is obviously lateral to the seed body, and distinctive histological features reveal that this cone represents a new genus of extinct Pinaceae. This new genus of fossil conifers, represented by a seed cone of unique structure, further enriches the known diversity of Early Cretaceous Pinaceae. When added to the existing record of fossil seed cones, the new genus and species, Onostrobus elongatus Rothwell et Stockey, highlights knowledge that among early-diverging lineages of Pinaceae there has been considerable Cretaceous and Paleogene evolution that is reflected by variations among subtle characters that are recognizable only from anatomically preserved specimens.

Key words

anatomy, conifer, cotyledonary embryo, Pinaceae, seed cone

Abstract

The Lanark Basin is situated along the southern Margin of the Midland Valley of Scotland. It contains a series of Silurian inliers whose transitional marine to brackish to terrestrial sequences are unconformably overlain by Lower Devonian ‘Lower Old Red Sandstone’ deposits. Dispersed spore assemblages have been reported from terrestrial deposits towards the top of the Silurian sequences and are of early Wenlock age. Those from the Hagshaw Hills inlier have been reinvestigated and updated records reported herein. The first dispersed spore assemblage recovered from the ‘Lower Old Red Sandstone’ deposits that unconformably overlie the Silurian sequences is described. It is from the Greywacke Conglomerate Formation and is interpreted as being of Early Devonian (Lochkovian) age. This is concordant with previous radiometric age dates reported from associated volcanic rocks.

Key words

Hagshaw Hills inlier, Fish Bed Formation, Greywacke Conglomerate Formation

Abstract

The scale-leaved fossil conifer Sphenolepis kurriana (Dunker) Schenk is redescribed from the Wealden floras of Germany and England. The revised study of this fossil species encompasses specimens remaining in the nineteenth century Dunker Collection in the Museum für Naturkunde, Berlin, from which a neotype is selected; figured specimens in the Museum of Geology, Georg-August-Universität, Göttingen and the Rufford Collection in the Natural History Museum, London. Dispersed samples more recently collected from debris-beds in the English Wealden show cuticular details of particularly well-preserved leaf-bases and leaves. To date, Sphenolepis kurriana (Dunker) Schenk is the only non-cheirolepidiaceous conifer species confirmed as present in both the English and German Wealden floras. In situ cones, identified as female, indicate a taxodiaceous Cupressaceae affinity for S. kurriana.

Key words

Lower Cretaceous, Wealden, scale-leaved, fossil conifer, female cones, Sphenolepis kurriana, neotype, Berlin

Abstract

The coal-bearing lower Clackmannan Group of Scotland has yielded diverse fossil floras of Serpukhovian (late Mississippian) age dominated by arborescent lycopsids, equisetopsids, ferns and lyginopteridalean pteridosperms. Similar macrofloras of the same age have been reported from coal-bearing deposits of Maine-et-Loire (NW France) and Upper Silesia (Czech Republic and Poland). These fossil floras together reflect the earliest development of the coal swamp biome in tropical Euramerica. The biome appeared on newly-exposed areas of coastal plain that formed as result of lowered sea-levels during the first major cooling phase of the Late Palaeozoic Ice Age. A new combination Artisophyton chalmersii is proposed based on Megaphyton chalmersii Goodlet.

Key words

palaeobotany, early Carboniferous, coal swamp biome, climate change

Abstract

Amber deposits are rare in Jurassic successions, occurring in small quantities, whereas Lower Cretaceous strata host many substantial and commonly fossiliferous amber deposits worldwide. Minor amounts of Early Jurassic amber have been reported from Italy, and small amounts of Late Jurassic amber are known from Lebanon, Jordan and Thailand. Other Jurassic amber deposits that require reinvestigation of their age and provenance have also been reported from Denmark and France. Few of these amber deposits contain fossils, the others lack inclusions, suggesting a ‘Jurassic amber gap’ in the fossil record. Here, we surveyed fossil plant collections held at the Swedish Museum of Natural History, Stockholm, for amber and amberproducing plants from Jurassic floras. We focused on the collection of plants from Shaanxi, China and the Middle Jurassic floras of Iran and Afghanistan from the H.-J. Schweitzer collection. Using a hand-held UV light microscope, we scanned the collections for resinous remains as ambers can show autofluorescence with UV light, but found no dispersed amber fragments or droplets. Some researchers refer to fossilized resin within plant tissues under that name to differentiate it from exuded resins preserved as amber, and we follow this convention. We identified a conifer fragment of Elatocladus sp. from China with in situ rods of resin preserved in the leaves and a unique conifer twig (Elatides sp.) from Afghanistan with tiny linear resin traces in leaves that were only visible via autofluorescence with UV light. These resinous traces likely define the former position of resin canals in the leaves, but the resin is not preserved as in situ rods. Instead, it has impregnated the coalified mesophyll, likely during fossilization, to form thin lines (chemical ‘ghosts’ of preserved resin) within the conifer leaf remains.

Key words

Afghanistan, autofluorescence, Cheirolepidiaceae, China, Cupressaceae, Elatides, Elatocladus, fluorescence, Jurassic amber gap, resin, UV light

Abstract

The spores of arbuscular mycorrhizal fungi (Glomeromycota) in the Early Devonian Rhynie ecosystem served as a habitat for a diversity of other fungi, only a few of which have been studied in detail so far. Rhizophydites shutei nov. sp. occurs in planar assemblages and tuft-like clusters comprised of thalli in various stages of development on Archaeosporites rhyniensis-like acaulospores. The presence of multiple individuals on several closely spaced hosts allows a thorough depiction of this fungus. Thalli are monocentric and characterized by an ovoid, narrowly to broadly citriform, bulb-shaped, or globose inoperculate zoosporangium 10–35(–38) μm high and 7–33 μm wide, and an endobiotic rhizoidal system reaching into the host lumen. The sporangium can be epibiotic or interbiotic (stalked), or located between the wall layers of the host spore. Mature sporangia have a pronounced apical papilla. Similarities with the modern chytrid genera Rhizophydium and Phlyctochytrium are used to suggest that the fossil belongs to the Chytridiomycota, and to place it in the genus Rhizophydites, which accommodates chytrid-like fossils that are morphologically similar or even identical to present-day Rhizophydium. This discovery contributes to our understanding of the various roles mycorrhizal fungi had in early terrestrial ecosystems.

Key words

apophysis, discharge papilla, Glomeromycota, Early Devonian, rhizoidal system, Rhizophydium, zoosporangium

Abstract

Terrestrially-derived cryptospores from Cambrian deposits in eastern Tennessee were examined using transmission electron microscopy (TEM) to determine the underlying structural basis for spore wall construction in these pre-embryophytic spore types. In addition to previously-described species from the middle Cambrian Conasauga Group, we examined new specimens extracted from the Rome Formation, which are coeval to the oldest reported cryptospores from North China. Our results reveal a substantial diversity of endogenous laminated sporoderm construction, expanding on the three basic types described previously. The underlying cellular processes involved in the production of sporopollenin wall construction were in place by the middle Cambrian, but a modern form of spore wall assembly did not evolve until the canalization of plant-like sporogenesis during the Middle Ordovician.

Key words

Rome Formation, origin of land plants, sporopollenin, charophytes, terrestrialization, paleopalynology, sporoderm, Conasauga Group, synoecosporal wall

Abstract

Bed TB33, a lacustrine unit within the late Eocene (early Priabonian) How Ledge Limestone, Headon Hill, Isle of Wight, UK, contains a rich mammalian fauna. The previously reconstructed food web included mammalian predators and prey (ground dwelling, scansorial and arboreal; insectivores, frugivores, herbivores and carnivores) and two inferred owls. Unfortunately, the extensive bulk sediment sampling and sieving used to obtain the vertebrate fauna had not yielded any plant fossils other than charophyte gyrogonites. This new work has focused on plant mesofossils and palynofacies in the uppermost horizons of the vertebrate-rich bed aiming to reconstruct the vegetation that hosted the mammals. Other than cysts of Zygnemataceae, phytoplankton are absent. The presence of the aquatic plants Azolla and Salvinia on the lake is documented by megaspores and microspore massulae. The palynomorphs are dominated by algal cysts, Azolla microspore massulae fragments and two morphologies of trilete fern spores. These data document a depositional setting in a lake with abundant free-floating Azolla or Salvinia and with a margin vegetation dominated by ferns. The data support one of our previous inferences that the arboreal mammals were brought to the site from some distance away by predators. However, the challenge to fully reconstruct the mammalian habitats remains.

Key words

Eocene, mammal, primate, plant mesofossils, resin, algal cyst, pollen, spore, seed, megaspore, microspore massulae, Azolla, Salvinia

Abstract

Anisopteris shuteana Hayes et H.L.Pearson sp. nov., a rare fertile adpression fossil, is described from the Mississippian of Teilia Quarry, Gwaenysgor, North Wales, UK. The new species is based on material from the Margaret Benson Collection and named in honour of Cedric H. Shute who curated the Palaeobotany Collections at the Natural History Museum, London. The account arises from an unpublished typescript by Benson, who considered the specimen to be a fern fructification. A. shuteana is of particular importance because only two fertile fronds of Anisopteris have previously been described. Detailed comparisons are drawn between these two species, Anisopteris fertilis (J.Walton) Hirmer, 1940 and Anisopteris lindseaeformis (Bunbury) Hirmer, 1940 and A. shuteana, which is assigned to the Lyginopteridales.

Key words

Anisopteris, adpression, fertile, Teilia, Visean, Mississippian, lower Carboniferous, frond, sporangia, Wales, Euramerica

Abstract

Tortilicaulis D.Edwards is a genus of long-standing unknown affinity in which there are two species: the holotype T. transwalliensis D.Edwards, known only from coalified compressions and T. offaeus D.Edwards, Fanning et J.B.Richardson, known from an assemblage of minute, exceptionally well preserved charcoalified fossils from a Lochkovian deposit in the Welsh Borderland. It has previously been interpreted as bryophyte-like after comparisons based on twisted cells in both stems and sporangia were made with certain extant liverwort and moss genera, there being no evidence of vascular tissues. It has previously been grouped within the horneophytes in cladistic analyses. Subsequent studies of T. offaeus confirmed the presence of stomata on their isotomously branching stems and dehiscence of the sporangium into two valves, but the absence or presence of tracheids has not been demonstrated. Despite numerous attempts to observe the internal anatomy of stems through physical splitting followed by scanning microscopy, we turned to synchrotron radiation x-ray tomography microscopy. Here we describe five Tortilicaulis specimens that were selected for scanning and demonstrate simple annular tracheids within their twisted stems. We conclude that Tortilicaulis was an early diverging tracheophyte, although whether a member of the stem or crown group awaits further detailed cladistic analyses. While architecturally similar to Psilophyton Dawson, the hypothesis that Tortilicaulis was ancestral to the trimerophytes remains unproven.

Key words

early tracheophytes, Lower Devonian, embryophytes, Tortilicaulis, tracheids, water-conducting cells, scanning electron microscopy, synchrotron radiation x-ray tomography microscopy, mesofossils

Abstract

We reinvestigated type material and subsequently collected fossil nuts of Carya costata (C.Presl ex Unger) Unger based on type material from the Oligocene of western Bohemia. These specimens are older than most occurrences of C. ventricosa (C.Presl ex Brongn.) Unger which has its type locality in the Miocene of Salzhausen, Germany. Although preserved only as molds and casts in tuffaceous volcanoclastic siltstone, micro-CT scanning indicates that the morphology of C. costata is nearly identical to that of C. ventricosa. The preservation of these nuts as 3-dimensional molds retains evidence of gnawing indicating that, as today, hickory nuts were an important food source for mammals and/or birds of the Oligocene.

Key words

Hickory nuts, Juglandaceae, micro-CT scanning, molds, casts, Alnus, Symplocos

Abstract

An enigmatic deposit at Pavone d’Alessandria provided, at the end of the 19th century, about one hundred plant macrofossils, considered to be Oligocene in age. That material is no longer available, but a few animal (an insect and a fish) and plant remains have recently been recovered from this locality. A single remnant of Aphanius crassicaudus is considered relevant, in combination with a recent assessment of the geology in the studied area, to propose a Messinian age for the deposit. The taxonomic composition of the 19th century plant assemblage, only documented by sketchy drawings, is difficult to re-interpret, but its possible relationship with Messinian plant assemblages studied in the last 30 years is discussed in the light of recent observations. A few plant taxa that can be recognized on the basis of elementary morphological traits, e.g., Fagus gussonii, support a Messinian rather than Oligocene age.

Key words

Aphanius, fault, fossil leaves, geology, Neogene, Pavone d’Alessandria, Vena del Gesso