Rhynie Chert Research Articles

Germination shields in Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae) from the 400 million-year-old Rhynie chert

Glomeromycotan spores from the Lower Devonian Rhynie chert provide the first evidence for germination shields in fossil fungi and demonstrate that this complex mode of germination was in place in some fungi at least 400 million years ago. Moreover, they represent the first direct marker relative to the precise systematic position of an Early Devonian endomycorrhizal fungus. In extant fungi, germination shields occur exclusively in the genus Scutellospora (Glomeromycota: Diversisporales, Gigasporaceae). These structures are regarded as a derived feature within the phylum Glomeromycota, and hence their presence in the Rhynie chert suggests that major diversification within this group of fungi occurred before the Early Devonian.

Spore assemblages from the Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Rhynie outlier, Scotland

ABSTRACTSince the late 1980s an extensive programme of trenching/borehole drilling has been undertaken in order to study the Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Rhynie outlier in the Grampian Highlands of Scotland. The boreholes have provided new information on the stratigraphical succession and geological structure of the Rhynie outlier, both of which were hitherto poorly understood due to the paucity of good surface exposure and the complex geological relationships of the deposits. One hundred and eighteen palynological samples were collected, representing much of the stratigraphical sequence of the inlier, of which 106 were productive. Productive samples yield assemblages of well preserved palynomorphs, dominated by spores and phytodebris, but also containing arthropod cuticle and rare freshwater algal remains. The spore assemblages are systematically described and two new genera and six new species proposed. They are similar throughout the sequence and the spores belong to the polygonalis–emsiensis Spore Assemblage Biozone of Richardson & McGregor (1986) and the PoW Oppel Zone (possibly Su Interval Zone) of Streel et al. (1987), indicating an early (but not earliest) Pragian–?earliest Emsian age range, that may possibly be restricted to latest Pragian–?earliest Emsian. The palynomorph assemblages contain only terrestrial forms, supporting sedimentological interpretation of the deposits as ‘Lower Old Red Sandstone’ fluviatile and lacustrine deposits, with occasional extrusive volcanics and volcaniclastic sediments intercalated. The palynomorphs are of variable thermal maturity (within and between samples), probably reflecting differential heating associated with the complex volcanic/hydrothermal system. The new palynological data provide, for the first time, a reliable biostratigraphical age for the deposits, and suggest that they accumulated relatively rapidly. Spore biostratigraphy and thermal maturity studies facilitate correlation of the tectonically complex deposits, and shed light on other aspects of the geological history of the outlier. The palynomorph assemblages also aid interpretation of the biota of the Rhynie basin, including the exceptionally preserved biotas of the Rhynie and Windyfield cherts.

Hassiella monospora gen. et sp. nov., a microfungus from the 400 million year old Rhynie chert

A new microfungus, Hassiella monospora gen. et sp. nov., consisting of coenocytic hyphae is associated with degraded plant material in the Early Devonian silicified Rhynie chert ecosystem. Some hyphae produce small bulb-like projections that subsequently develop into spherical, thick-walled and highly ornamented reproductive structures. Mature reproductive structures are characterized by a prominent, funnel-shaped appendage that is interpreted as an amphigynous antheridium. When combined, these features are suggestive of the oogonia/oosporangia in certain extant members of the Peronosporomycetes ( Oomycota).

Fossils explained 51

The Earth???s oldest terrestrial ecosystems date from the Late Silurian period, about 414 million years ago. Amongst primitive plants lived the first land-based animals; invertebrate invaders of a new world, some 30 million years before vertebrates made the very same transition. The fossil record suggests many early land animals were arthropods, belonging to subgroups such as Myriapoda (e.g. millipedes and centipedes) and Arachnida (e.g. spiders, scorpions, mites, etc.). Trigonotarbids belong to the latter. They are appar- ently primitive arachnids, superficially similar in ap- pearance to spiders, but lacking the ability to produce silk. Their presence at Ludford Lane in the Welsh Borderlands in the UK (P??\'{\i}dol\'{\i}, Late Silurian) places the group amongst the earliest terrestrial animals, and their anatomy is well known from exception- ally preserved, silicified fossils in the slightly younger Early Devonian Rhynie Chert of Scotland (Fig. 1). By the Late Carboniferous, trigonotarbids seem to have been amongst the most abundant arachnids; at least their fossils are relatively common throughout the Coal Measures deposits of Europe and North America. They have also been recorded in South America. Such success didn???t last???the group became extinct in the Permian.

A HEXAPOD FROM THE EARLY DEVONIAN WINDYFIELD CHERT, RHYNIE, SCOTLAND

Abstract: New diagnostic morphological features discovered following a re-examination and further preparation of the holotype of Leverhulmia mariae Anderson and Trewin from the Early Devonian (Pragian) Windyfield chert are described and discussed here. The discovery of anterior (thoracic?) leg appendages with attached pretarsal elements comprising a fixed median unguis, a pair of articulated lateral ungues and possible unguitractor plate has allowed us to reclassify this enigmatic fossil as Hexapoda incertae sedis. We interpret the holotype as part of an abdomen bearing at least five pairs of segmented leglets. The condition of the ungues on the anterior appendages is strongly reminiscent of Archaeognatha and Zygentoma (= Thysanura s.s.), and the segmented leglets on the abdomen show similarities with certain fossil ‘apterygotes’ known from the Carboniferous. Leverhulmia is the third hexapod species found in the cherts at Rhynie, the other forms being the collembolan Rhyniella praecursor Hirst and Maulik, and the pterygote insect Rhyniognatha hirsti Tillyard. Showing closer affinities with Archaeognatha and Zygentoma, Leverhulmia may well represent the earliest fossil apterous insect known to date.

A FOSSIL HARVESTMAN (ARACHNIDA, OPILIONES) FROM THE MISSISSIPPIAN OF EAST KIRKTON, SCOTLAND

Abstract A fossil harvestman (Arachnida, Opiliones) from the Mississippian (Visean: Brigantian) of East Kirkton, Scotland is described as Brigantibunum listoni new genus and species. At ca. 340 Ma, it represents the second oldest record of Opiliones. Although some details are lacking, this long-legged, small-bodied and rather gracile harvestman is surprisingly modern-looking and appears to show the impression of an annulate ovipositor. Its leg anatomy closely matches that of some living Eupnoi and it is tentatively referred to this clade. Like the newly discovered Rhynie chert harvestmen, it reinforces the idea that modern, crown-group Opiliones can be traced back to at least the mid-Paleozoic.

Life history biology of early land plants: deciphering the gametophyte phase.

The ca. 400-million-year-old Rhynie chert biota represents a benchmark for studies of early terrestrial ecosystems. The exquisite preservation of the organisms documents an ancient biodiversity that also includes various levels of biological interaction. Absent from the picture until recently has been detailed information about the development of the gametophyte phase and the alternation of generations of the macroplants in this ecosystem. Here, we trace the development of the gametophyte phase of Aglaophyton, an early land plant with an unusual complement of structural and morphological characters. Mature gametophytes consist of a fleshy protocorm attached to the substrate by basal rhizoids; arising from the upper surface are one to several upright gametangiophores bearing multiple gametangia. Stomata are present on the upper surface of the protocorm and gametangiophore, and endomycorrhizal fungi extend throughout the gametophyte. Gametophytes are unisexual, producing either antheridiophores or archegoniophores. There is no evidence that gametophytes later become hermaphroditic. The sexual dimorphism of the Rhynie chert gametophytes is inconsistent with theoretical ideas about the haploid phase of early land plants. The gametophyte phase of early land plants can now be considered within an ecological and evolutionary framework that, in turn, can be used to develop hypotheses about some aspects of the population dynamics and growth of these early land plants.

Nothia aphylla: The Issue of Clonal Development in Early Land Plants

The Early Devonian herbaceous plant Nothia aphylla from the Rhynie Chert (Aberdeenshire, Scotland) is a striking and informative example of a developmental strategy in early land plants. Although simple and primitive in anatomy, N. aphylla combined sexual and vegetative reproduction in order to survive and colonize moist patches near ponds and hot springs in an alluvial plain. Large colonies formed, being mainly composed of clonal individuals derived from asexual reproduction, i.e., the separation of similar units created by lateral branching. Each unit consisted of a single rhizome bearing one ventral, rhizoidal ridge and one distal, aerial, photosynthetic, and fertile branched shoot. The rhizomes allowed for an indeterminate horizontal propagation, while the erect photosynthetic shoots furnished a limited vertical occupation. Similar architecture and clonal development existed among coeval plants, such as Aglaophyton major and Horneophyton lignieri, and persisted through geologic time. Nowadays asexual reproduction is still a successful strategy in bryophytes, pteridophytes, and angiosperms.

Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1–5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

Secular change in the Precambrian silica cycle: Insights from chert petrology

Chert deposits preserve a record of secular change in the oceanic silica cycle. The evolutionary radiation of silica-secreting organisms resulted in a transition from abiological silica deposition, characteristic of the Archean and Proterozoic eons, to the predominantly biologically controlled silica deposition of the Phanerozoic. Comparative petrography of Phanerozoic and Precambrian cherts indicates that an earlier change in chert deposition occurred toward the end of the Paleoproterozoic era (ca. 1.8 Ga). In Neoproterozoic and Mesoproterozoic strata, early diagenetic chertification is largely restricted to peritidal environments. These early diagenetic cherts typically occur as nodules or discontinuous beds within carbonate deposits that have similar depositional textures. The cherts formed primarily by carbonate replacement with subsidiary direct silica precipitation. Some of the Paleoproterozoic cherts associated with iron formations, however, are distinctly different from younger cherts and appear to have formed largely by direct silica precipitation at or just below the seabed. These primary cherts lack ghosts or inclusions of carbonate precursors, have fine-scale grain fracturing (possibly from syneresis), exhibit low grain-packing densities, and are not associated with unsilicified carbonate deposits of similar depositional composition. Cherts in some Paleoproterozoic iron formations (e.g., the Gunflint Formation, northwestern Lake Superior region) are composed of silica types similar to those in Phanerozoic sinters (e.g., the Devonian Rhynie and Windyfield cherts, Scotland). Such cherts may provide evidence that basinal, and perhaps global, oceanic silica concentrations were higher during the Paleoproterozoic era than at later times.

Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1-5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

A new early devonian trigonotarbid arachnid from the Windyfield Chert, Rhynie, Scotland

Synopsis A new, exceptionally preserved, trigonotarbid (Arachnida, Trigonotarbida, Palaeocharin‐idae), Palaeocharinus tuberculatus sp. nov. is described from the early Devonian (Pragian) Windyfield chert of Rhynie, Aberdeenshire, Scotland, UK. The specimens found are almost twice the size of previous Rhynie palaeocharinids and display an autapomorphic, microtuberculate ornament over the whole body. This tuberculation and possible developing tergite and sternite divisions, which the microtubercles in places appear to define, show significant similarities with the possibly closely related Carboniferous family Anthracomartidae.

Article retracted due to printing error -- Please see issue 97:1 for the correct version of "Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism"

We describe a perithecial, pleomorphic ascomycetous fungus from 400 MaBP Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1–5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

Correlation of the Early Devonian Rhynie chert beds between three boreholes at Rhynie, Aberdeenshire

Synopsis Three sequences of the Early Devonian Rhynie Cherts Unit intersected by cored boreholes at the Rhynie SSSI (Site of Special Scientific Interest) are compared on the basis of both lithology and plant content. It is shown that over the 45–65 m distance covered by the boreholes general correlation can be made of the chert-bearing unit, and also sandstone and shale units. General thicknesses of units are similar in the three boreholes. However, there is no bed-to-bed correlation of the cherts or other lithologies, neither is there a correlation in the sequences of plants recorded. It is considered that the sequence was deposited in the distal regions of sinter deposition on a low-angle outwash apron from a hot spring, where the water table was close to the surface, and water was frequently ponded. Overbank flooding from a northward-flowing river system periodically inundated the outwash apron, depositing sand and mud and interrupting sinter deposition. On the basis of plant occurrence in the chert beds intersected in the boreholes it is estimated that on average 15% of the area was bare ground, 30% covered with plant litter, and 55% with growing plants. Similar environments are seen today on the distal marshy areas of outwash aprons from hot springs in Yellowstone National Park, USA.

Fungi from the Rhynie chert: a view from the dark side

ABSTRACTThe exquisite preservation of organisms in the Early Devonian Rhynie chert ecosystem has permitted the documentation of the morphology and life history biology of fungi belonging to several major taxonomic groups (e.g., Chytridiomycota, Ascomycota, Glomeromycota). The Rhynie chert also provides the first unequivocal evidence in the fossil record of fungal interactions that can in turn be compared with those in modern ecosystems. These interactions in the Rhynie chert involve both green algae and macroplants, with examples of saprophytism, parasitism, and mutualism, including the earliest mycorrhizal associations and lichen symbiosis known to date in the fossil record. Especially significant are several types of specific host responses to fungal infection that indicate that these plants had already evolved methods of defence similar and perhaps analogous to those of extant plants. This suggests that mechanisms underlying the establishment and sustenance of associations of fungi with land plants were well in place prior to the Early Devonian. In addition, a more complete understanding of the microbial organisms involved in this complex ecosystem can also provide calibration points for phylogenies based on molecular data analysis. The richness of the microbial community in the Rhynie chert holds tremendous potential for documenting additional fungal groups, which permits speculation about further interactions with abiotic and biotic components of the environment.

A review of the palaeoenvironments and biota of the Windyfield chert

ABSTRACTThe Windyfield chert site is located 700 m NE of the original Rhynie chert locality at Rhynie, Aberdeenshire, Scotland. Originally identified by concentrations of surface float material, a drilling and trenching programme of the area in 1997 revealed a chert ‘pod’ in situ interbedded with fluvial/lacustrine sandstones and hydrothermally altered shales. Chert morphologies identified from float blocks and trench material range from tabular beds to lenticular pods displaying massive, nodular, laminated and brecciated fabrics, and geyserite splash textures. A suite of floral and faunal associations, when combined with distinctive macro- and microscopic chert textures, has been used to interpret depositional conditions. Palaeoenvironments ranged from terrestrial laminated, brecciated and vegetated sinter sheets to low-temperature pools and marginal aquatic settings. The flora comprises six higher land plant species, nematophytes, charophytes, various fungi and probable cyanobacteria. Arthropods include branchiopod crustaceans, a euthycarcinoid, trigonotarbid arachnids, centipedes, eoarthropleurids and a possible hexapod. The biota of the Windyfield chert is closely comparable to that found in the Rhynie chert. Together, the Windyfield and Rhynie cherts contain the most diverse associated fossil arthropod fauna of terrestrial and freshwater origin from rocks of comparable age anywhere in the world.

A catalogue of the type and figured specimens of Hexapoda from the Rhynie chert (early Devonian) at The Natural History Museum, London, UK

ABSTRACTThirteen specimens of type and/or figured Hexapoda from the Rhynie chert are housed at The Natural History Museum, London, UK. They are listed along with a complete bibliography of where they have been cited and figured. Two taxa are present: Rhyniella praecursor Hirst & Maulik 1926 (Collembola); and Rhyniognatha hirsti Tillyard 1928 (Insecta)

New gametophytes from the Early Devonian Rhynie chert

ABSTRACTSeveral new gametophytes are described from the Early Devonian Rhynie chert. The new monotypic genus Remyophyton, being the gametophyte of Rhynia, is represented by a dense stand of in situ preserved gametophytes with antheridia- and archegonia-bearing axes. The gametophytes are remarkably small in comparison to those of other Rhynie chert plants. The generic diagnoses of Lyonophyton and Langiophyton are emended to include archegonia- and antheridiabearing axes. All essential stages of the reproductive cycle, i.e. sporophytes, and male and female gametophytes, can now be demonstrated for three of the six land plants from the Rhynie chert, i.e. Rhynia gwynne-vaughanii, Aglaophyton major and Horneophyton lignieri.

History of research on the geology and palaeontology of the Rhynie area, Aberdeenshire, Scotland

ABSTRACTGeological and palaeontological research in the Rhynie area, Aberdeenshire, Scotland, has progressed in several stages. Following early surveys in the nineteenth century, Dr William Mackie mapped the western margin of the basin in 1910–1913, and discovered the plant-bearing chert. Following trenching of the chert in 1913, Kidston & Lang described the plant fossils between 1917 and 1921 and Scourfield, Hirst and Maulik the arthropods in the 1920s. Following a ‘dark age’ of some 30 years, Geoffrey Lyon awakened interest in the late 1950s. Trenching in 1963–1971 provided Lyon and his co-workers with new material, and resulted in finds of new plants and reinterpretations of earlier work. The next phase was initiated by Winfried Remy's discovery of gametophytes in material given to him by Lyon. Since 1980, the Münster school has continued to make exciting discoveries. Aberdeen University involvement began in 1987 with geochemical work confirming a hot spring origin for the chert. Drill cores taken in 1988 and 1997, and further trenching have allowed structural, sedimentological and stratigraphic reappraisals, and resulted in the discovery of a new biota in the Windyfield chert. Long-term collaborative international research continues to advance interpretation of this unique Early Devonian hot spring system, and the remarkably diverse freshwater and terrestrial biota of the cherts.

A harvestman (Arachnida: Opiliones) from the Early Devonian Rhynie cherts, Aberdeenshire, Scotland

ABSTRACTA harvestman (Arachnida: Opiliones) is described from the Early Devonian (Pragian) Rhynie cherts, Aberdeenshire, Scotland. Eophalangium sheari gen. et sp. nov. is the oldest known harvestman. The material includes both males and a female preserving, respectively, a cuticle-lined penis and ovipositor within the opisthosoma. Both these structures are of essentially modern appearance. The Rhynie fossils also show tracheae which are, again, very similar to those of living harvestmen. This is the oldest unequivocal record of arachnid tracheal respiration and indicates that E. sheari was terrestrial. An annulate, setose ovipositor in the female suggests that it can be excluded from the clades Dyspnoi and Laniatores, in which the ovipositor lacks such annulations. However, the penis shows evidence of two muscles, a feature of uncertain polarity seen in modern Troguloidea (Dyspnoi). The presence of median eyes and long legs excludes Cyphophthalmi, and thus, E. sheari is tentatively referred to the suborder Eupnoi. Therefore, this remarkable material is implicitly a crown-group harvestman and is one of the oldest known crown-group chelicerates. It also suggests an extraordinary degree of morphological stasis within the eupnoid line, with the Devonian forms differing little in gross morphology – and perhaps in reproductive behaviour – from their modern counterp