Early Devonian Research Articles

Continuous Sections of the Devonian and Carboniferous Carbonates and Timing of Collision in the Chinese South Tianshan

New stratigraphic data indicate that carbonate sedimentation in the axial part of the Chinese South Tianshan (STS) occurred continuously from the Early and Middle Devonian to the latest Carboniferous. This reflects steady subsidence in quiet tectonic regime and excludes major collisional events in the STS during this time. Pre-Carboniferous structural events, previously identified in the marginal parts of the Kazakhstan and Tarim continental massifs, did not extend to the STS basin. Continental collision in the Chinese STS occurred during the latest Carboniferous and early Permian, as in adjacent areas to the west in Kyrgyzstan.

First Record of Ostracods from the Upper Silurian Tambolar Formation, Argentine Precordillera

Fil: Salas, Maria Jose. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Early Devonian Marine and Terrestrial Palynomorphs from the Chacoparaná Basin, Uruguay

The Cordobes Formation and the basal section of the La Paloma Formation, from the borehole La Paloma a-186 and the Devonian oucrops of the Chacoparana Basin, in Uruguay, yielded diverse and well-preserved marine and terrestrial palynomorphs. The palynological assemblages show a clear predominance of marine palynomorphs, with 75 species composed mainly of acritarchs and chlorophytes with subordinated chitinozoans and scolecodonts, and 48 terrestrial palynomorphs species composed mainly of trilete spores and subordinated cryptospores, non-marine palynomorphs and phytodebris. The palynological assemblages enable the constraining of the age of the lower and middle parts of the Cordobes Formation to the late Pragian–early Emsian, while the upper part of this unit and the basal part of the La Paloma Formation can be assigned to the early Emsian. The relative palynomorph abundances throughout the studied samples support the palaeoenvironment interpretation, based on sedimentology and depositional sequences studies, that indicates the transition from transgressive deposits in a restricted platform of the Cordobes Formation to wave-dominated shelf deposits of the La Paloma Formation. The Gondwanan affinities of the Devonian of Uruguay are confirmed by the presence of marine and terrestrial palynomorph taxa restricted to this palaeocontinent. A new trilete spore species, Distaverrusporites steemansii, is described and a new informal acritarch group, the Evittia sommeri-Evittia geometrica Group, is proposed.

Spore wall ultrastructure and development in a basal euphyllophyte: Psilophyton dawsonii from the Lower Devonian of Quebec (Canada).

Euphyllophytes, a clade including living ferns, horsetails, and seed plants, have a rich fossil record going back to the Early Devonian. The euphyllophyte spore wall has a complex structure, the evolutionary origins of which are incompletely understood. Psilophyton is the best-characterized basal euphyllophyte genus; thus, data on this genus can inform current hypotheses on spore wall structure and development, which propose a bilayered spore wall organization of combined spore and sporangial origin for the ancestral euphyllophyte. We employed cellulose acetate peel sectioning of permineralized Lower Devonian (Emsian) Psilophyton dawsonii sporangia, combined with electron microscopy, to document spore wall structure and development. The Psilophyton dawsonii spore wall is bilayered. The inner spore wall is homogeneous, probably of lamellar construction. The outer spore wall, loosely attached to the inner wall, covers distal and equatorial spore areas, and has a foveolate base layer upon which stacks of sporopollenin lumps accrete centrifugally, forming the scaffolding for the final apiculate ornamentation. This is the most complete account on spore wall structure, allowing developmental interpretations, in a basal euphyllophyte. The bipartite organization of the Psilophyton dawsonii spore wall reflects development as a result of two processes: an inner layer laid down by the spore cell and an outer layer of tapetal origin. Providing direct evidence on the spore wall of a basal euphyllophyte, these data confirm previous hypotheses and mark an empirically supported starting point for discussions of the evolution of spore wall development in euphyllophytes.

Global kinematics of tectonic plates and subduction zones since the late Paleozoic Era

Detailed global plate motion models that provide a continuous description of plate boundaries through time are an effective tool for exploring processes both at and below the Earth's surface. A new generation of numerical models of mantle dynamics pre- and post-Pangea timeframes requires global kinematic descriptions with full plate reconstructions extending into the Paleozoic (410 Ma). Current plate models that cover Paleozoic times are characterised by large plate speeds and trench migration rates because they assume that lowermost mantle structures are rigid and fixed through time. When used as a surface boundary constraint in geodynamic models, these plate reconstructions do not accurately reproduce the present-day structure of the lowermost mantle. Building upon previous work, we present a global plate motion model with continuously closing plate boundaries ranging from the early Devonian at 410 Ma to present day.We analyse the model in terms of surface kinematics and predicted lower mantle structure. The magnitude of global plate speeds has been greatly reduced in our reconstruction by modifying the evolution of the synthetic Panthalassa oceanic plates, implementing a Paleozoic reference frame independent of any geodynamic assumptions, and implementing revised models for the Paleozoic evolution of North and South China and the closure of the Rheic Ocean. Paleozoic (410–250 Ma) RMS plate speeds are on average ∼8 cm/yr, which is comparable to Mesozoic–Cenozoic rates of ∼6 cm/yr on average. Paleozoic global median values of trench migration trend from higher speeds (∼2.5 cm/yr) in the late Devonian to rates closer to 0 cm/yr at the end of the Permian (∼250 Ma), and during the Mesozoic–Cenozoic (250–0 Ma) generally cluster tightly around ∼1.1 cm/yr. Plate motions are best constrained over the past 130 Myr and calculations of global trench convergence rates over this period indicate median rates range between 3.2 cm/yr and 12.4 cm/yr with a present day median rate estimated at ∼5 cm/yr. For Paleozoic times (410–251 Ma) our model results in median convergence rates largely ∼5 cm/yr. Globally, ∼90% of subduction zones modelled in our reconstruction are determined to be in a convergent regime for the period of 120–0 Ma. Over the full span of the model, from 410 Ma to 0 Ma, ∼93% of subduction zones are calculated to be convergent, and at least 85% of subduction zones are converging for 97% of modelled times. Our changes improve global plate and trench kinematics since the late Paleozoic and our reconstructions of the lowermost mantle structure challenge the proposed fixity of lower mantle structures, suggesting that the eastern margin of the African LLSVP margin has moved by as much as ∼1450 km since late Permian times (260 Ma). The model of the plate-mantle system we present suggests that during the Permian Period, South China was proximal to the eastern margin of the African LLSVP and not the western margin of the Pacific LLSVP as previous thought.

Buried deep beyond the veil of extinction: Euphyllophyte relationships at the base of the spermatophyte clade.

The deep origin and early evolution of seed plants (spermatophytes) are poorly understood. Starting in the Early Devonian, euphyllophytes diversified rapidly into several groups. Two of these groups, progymnospems and Stenokoleales, along with satellite taxa, have been involved in discussions of seed plant origins. Because these early lineages are extinct, the key to the origin and early evolution of seed plants lies in the fossil record. Decades-long paleobotanical work has produced data on the diversity and anatomy of fossil species, which now provide a foundation for exploring seed plant origins in a phylogenetic context. We address phylogenetic relationships between early seed plants, aneurophytalean progymnosperms, Stenokoleales, and several Devonian species of uncertain affinities using parsimony analyses that include 28 anatomically preserved species (the most comprehensive taxon sampling to date) and 49 morphoanatomical characters (including nine continuous characters). Our analyses recover monophyletic seed plants, Stenokoleales, and aneurophytes, with the latter placed as sister to a clade (termed the bilateral clade) that includes the former two. When added in the analysis, continuous characters based on anatomy improve phylogenetic resolution. Our results support the groups defined by traditional taxonomy, resolve Stenokoleales nested among the lignophytes, and indicate that seed plants may share a closer ancestor with Stenokoleales than with aneurophytes. Additionally, our trees suggest a Givetian minimum age for the seed plant ancestor, a late Emsian minimum age for the Stenokoleales, and early Emsian minimum ages for lignophytes, the bilateral clade, and the aneurophyte ancestor.

Geology and field relations of the Wilsons Promontory batholith, Victoria: multiple, shallow-dipping, S-type, granitic sheets

ABSTRACTThe 1200 km2, Early Devonian (395 Ma) Wilsons Promontory batholith is a post-tectonic, high-level, composite body of S-type granites exposed on Wilsons Promontory and its offshore islands. Four plutons and six members are mapped and described. The rocks commonly contain magmatic garnet and cordierite, in addition to biotite, and biotite–quartz pseudomorphs after orthopyroxene. Planar fabrics abound in the batholith, which is characterised by emplacement of shallow-dipping granitic sheets, on a variety of scales. Particle size and density separation occurred during magma flow, and produced a wide variety of structures including layering, pipes and whorls rich in mafic minerals, K-feldspar phenocryst alignments and a notable swarm of enclaves. Local filter pressing may have played a role in the production of accumulations of K-feldspar crystals and the formation of late, tourmaline-bearing leucogranites and quartz veins. Batholith zonation and the distribution of component plutons are inferred to have been formed through sequential intrusion of separate magma batches rather than in situ differentiation. Overall, the batholith appears to consist of saucer-shaped plutons, and it is tilted gently to the east.

Zircon U-Pb ages and Hf isotopes of Paleozoic metasedimentary rocks from the Habahe Group in the Qinghe area, Chinese Altai and their tectonic implications

As one of the largest accretionary orogens in Earth's history, the Central Asian Orogenic Belt has attracted much attention in the past two decades, but there are still many unresolved issues regarding its tectonic nature and evolution. This is the case with the Chinese Altai whose tectonic provenance remains controversial, especially for the Paleozoic era. As the most widely exposed meta-sedimentary rocks in the Chinese Altai, the Habahe Group was previously considered as representing a component of Precambrian micro-continent, forming at a passive continental margin. Our new U-Pb data for detrital zircons from the Habahe Group in the Qinghe region of the eastern Chinese Altai indicate that the strata were deposited from the late Silurian to early Devonian (427–405 Ma) and experienced regional metamorphism in the middle Devonian (383 ± 9 Ma), as constrained by the age of youngest detrital zircons (427 ± 13 Ma), the age 405 ± 3 Ma of the tonalite that intrudes the Habahe Group, and the metamorphic age of 383 ± 9 Ma. Additionally, the majority of zircons from the Habahe Group have positive εHf(t) values (+0.22–+15.02). These data, combined with geochemical features and maturity of the sedimentary rocks, indicate an immature provenance for the Habahe Group, with the source materials mainly derived from a juvenile crust with some old continental components. The juvenile crust was most likely formed in a subduction zone, developing in the Chinese Altai during early-middle Paleozoic time. New geochemical data presented in this study suggest that the Chinese Altai was a transitional arc during early Paleozoic time, similar to the Japan-type arc with involvements of old continental components. Therefore, it is proposed that the Chinese Altai was likely rifted from the south margin of the Siberia Craton, probably related to the break-up of the Rodinia Supercontinent, and then experienced accretion and reworking with the subduction of the Paleo-Asian Ocean during early Paleozoic time.

New information on Brindabellaspis stensioi Young, 1980, highlights morphological disparity in Early Devonian placoderms.

Acid-prepared specimens of the placoderm Brindabellaspis stensioi (Early Devonian of New South Wales, Australia) revealed placoderm endocranial anatomy in unprecedented detail. Brindabellaspis has become a key taxon in discussions of early gnathostome phylogeny, and the question of placoderm monophyly versus paraphyly. The anterior orientation of the facial nerve and related hyoid arch structures in this taxon resemble fossil osteostracans (jawless vertebrates) rather than other early gnathostomes. New specimens of Brindabellaspis now reveal the previously unknown anterior region of the skull, including an exceptionally elongate premedian bone forming a long rostrum, supported by a thin extension of the postethmo-occipital unit of the braincase. Lateral overlap surfaces indicate an unusual anterior position for the jaws. Digital rendering of a synchrotron radiation scan reveals a uniquely specialized ethmoid commissure sensory canal, doubled back and fused into a midline canal. The visceral surface of the premedian bone has a plexus of perichondral bone canals. An updated skull roof reconstruction of Brindabellaspis adds to the highly variable dermal skull patterns of the probably non-monophyletic ‘acanthothoracids'. The unusual morphology revealed by the new specimens suggests that the earliest known reef fish fauna contained a diverse range of fishes with specialized ecological roles.

Neurocranial anatomy of an enigmatic Early Devonian fish sheds light on early osteichthyan evolution.

The skull of 'Ligulalepis' from the Early Devonian of Australia (AM-F101607) has significantly expanded our knowledge of early osteichthyan anatomy, but its phylogenetic position has remained uncertain. We herein describe a second skull of 'Ligulalepis' and present micro-CT data on both specimens to reveal novel anatomical features, including cranial endocasts. Several features previously considered to link 'Ligulalepis' with actinopterygians are now considered generalized osteichthyan characters or of uncertain polarity. The presence of a lateral cranial canal is shown to be variable in its development between specimens. Other notable new features include the presence of a pineal foramen, the some detail of skull roof sutures, the shape of the nasal capsules, a placoderm-like hypophysial vein, and a chondrichthyan-like labyrinth system. New phylogenetic analyses place 'Ligulalepis' as a stem osteichthyan, specifically as the sister taxon to 'psarolepids' plus crown osteichthyans. The precise position of 'psarolepids' differs between parsimony and Bayesian analyses.

Redescription of Phymolepis cuifengshanensis (Antiarcha: Yunnanolepididae) using high-resolution computed tomography and new insights into anatomical details of the endocranium in antiarchs.

BackgroundYunnanolepidoids constitute either the most basal consecutive segments or the most primitive clade of antiarchs, a highly diversified jawed vertebrate group from the Silurian and Early Devonian periods. Although the general morphology of yunnanolepidoids is well established, their endocranial features remain largely unclear, thus hindering our further understanding of antiarch evolution, and early gnathostome evolution. Phymolepis cuifengshanensis, a yunnanolepidoid from the Early Devonian of southwestern China, is re-described in detail to reveal the information on endocranial anatomy and additional morphological data of head and trunk shields.MethodsWe scanned the material of P. cuifengshanensis using high-resolution computed tomography and generated virtual restorations to show the internal morphology of its dermal shield. The dorsal aspect of endocranium in P. cuifengshanensis was therefore inferred. The phylogenetic analysis of antiarchs was conducted based on a revised and expanded dataset that incorporates 10 new cranial characters.ResultsThe lateroventral fossa of trunk shield and Chang’s apparatus are three-dimensionally restored in P. cuifengshanensis. The canal that is positioned just anterior to the internal cavity of Chang’s apparatus probably corresponds to the rostrocaudal canal of euantiarchs. The endocranial morphology of P. cuifengshanensis corroborates a general pattern for yunnanolepidoids with additional characters distinguishing them from sinolepids and euantiarchs, such as a developed cranio-spinal process, an elongated endolymphatic duct, and a long occipital portion.DiscussionIn light of new data from Phymolepis and Yunnanolepis, we summarized the morphology on the visceral surface of head shield in antiarchs, and formulated an additional 10 characters for the phylogenetic analysis. These cranial characters exhibit a high degree of morphological disparity between major subgroups of antiarchs, and highlight the endocranial character evolution in antiarchs.

Anatomically preserved Silurian ‘nematophytes’ from the Welsh Borderland (UK)

Stratified charcoalified fragments of thalloid organisms with tripartite tissue construction have been isolated from the basal member of the Upper Silurian (upper Ludlow) Downton Castle Sandstone Formation, exposed near Ludlow, Shropshire (England) and are considered to have had fungal affinity. They are divided into two major groups. The more novel of these is characterized by a superficial cortex separated from a basal layer of interweaving hyphae by an intermediate zone of compressed indeterminate tissue and members are placed in a new taxon, Tristratothallus ludfordensis. In the second, the intermediate zone comprises hyphae arranged at right angles to the cortex (termed palisade). Some members resemble the tissue construction of Nematothallus described from the Lower Devonian (Lochkovian) of the Welsh Borderland and considered to belong to fungi, some of which were lichenized. A further type, which shows remains of polysporic asci, is thought to represent a fragment of an apothecium (a disc-shaped ascoma of an ascomycete) of a pezizomycete and is the earliest such record. Yet others are characterized by a perforate cortex with occasional protruding hyphae, tissue construction of which was also recorded in the Lower Devonian of the Welsh Borderland and considered to display fungal characteristics. Coalified ‘black patches’ are common on bedding surfaces throughout the latest Silurian and Early Devonian and frequently are associated with basal embryophytes and tracheophytes. Those reported here are the oldest known with three-dimensional organization, studied via scanning electron microscopy (SEM) and attributed to fungi, and include some ascomycetes. Similar encrustations occur in even earlier rocks and may have been important constituents of the cryptogamic ground cover, which is postulated to have preceded higher plant life on land.

Geochronology, geochemistry, and tectonic implications of upper Silurian – Lower Devonian meta-sedimentary rocks from the Jiangyu Group in eastern Jilin Province, Northeast China

In this study, we present detrital zircon U–Pb ages and Hf isotopic data and whole-rock geochemical data from meta-sedimentary rocks of the Jiangyu Group in eastern Jilin Province (Northeast China) to constrain the late Silurian – Early Devonian tectonic evolution of the southeastern Xing’an–Mongolia Orogenic Belt. Two samples of the meta-sedimentary rocks from the Jiangyu Group yielded concordant ages ranging from 2926 to 415 Ma, and the youngest zircon populations of the two samples yielded weighted mean ages of 427 ± 3 and 426 ± 3 Ma, respectively. Combined with reliable published muscovite 40Ar-39Ar ages of 408 Ma from the overlying metamorphic ophiolitic mélange, these data indicate that the protoliths of the Jiangyu Group were deposited during the late Silurian – Early Devonian Era. A comparison of the U–Pb ages and Hf isotopic data for detrital zircons from northeastern Gondwana and the Jiangyu Group indicates a probable tectonic affinity. The whole-rock geochemical data indicate that the protoliths of the meta-sedimentary rocks from the Jiangyu Group were graywackes deposited in a continental arc setting. Based on the recognition of the early to middle Paleozoic subduction–accretion events along the eastern segment of the northern margin of the North China Craton (NCC), we infer that the subduction–accretion events may have occurred in the Yanbian area followed by one or more arc–continent collisions after the Early Devonian.

Tectonic evolution of the Paleozoic Barluk continental arc, West Junggar, NW China

The Barluk arc, situated in West Junggar, is an important component of the Kazakhstan domain in the Central Asian Orogenic Belt (CAOB). However, the nature of the Barluk arc (active continental margin or oceanic island arc) is in debate. The igneous rocks in the Shiwu area, Barluk arc, have diagnostic petrologic, geochronologic and geochemical signatures that uncover the attributes of the Barluk arc. In this paper, we report detailed petrology, whole rock geochemistry and Sr–Nd isotopic, zircon U–Pb dating and Hf isotopic data of igneous rocks in the Shiwu area. Our results reveal that: (1) except for 302.2 Ma gabbro, igneous rocks from Barluk arc in the Shiwu area are dioritic and granitic, have ages ranging from 323.8 to 310.5 Ma, and they have geochemical signatures originated from typical continental arcs, including calc-alkaline series rocks, enrichment of LILE, depletion of HFSE, and higher Th/Yb and Ta/Yb values; (2) the granitic porphyry and rhyolite in Barluk arc have old TDM2 (Hf) ages, up to 1091 Ma, suggesting the existence of Precambrian crust or similar materials as their sources; and (3) The 302.2 Ma gabbro dike has high values of εNd(t) (+7.54) and εHf(t) (+12.8 to +15.5), and a young T2DM (Nd) age (455 Ma), and therefore it was possibly related to upwelling of asthenosphere mantle in a post-subduction extensional tectonic setting. Based on these parameters, we suggest that the Barluk arc is defined as a Late Paleozoic continental margin arc along the margin of the Kazakhstan Continent. Westward subduction of the Junggar Oceanic plate in the Barluk area started in Early Devonian and continued to the Late Carboniferous (310 Ma). Subsequent post-collisional tectonic processes between the Junggar Oceanic plate and Kazakhstan Continent continued to the Late Carboniferous (302 Ma).

Diachronous Paleozoic accretion of peri-Gondwanan terranes at the Laurentian margin

Abstract In the original Wilson cycle, the northern Appalachian–Caledonide orogen resulted from the collision of two continental masses separated by a single ocean. One of these corresponds to the modern concept of Laurentia, but the colliding continent to the east has been variously subdivided into many smaller terranes and domains, including Ganderia, Avalonia and Megumia. Using published stratigraphic evidence and detrital zircon provenance data from units of known depositional age, the timing of arrival of these units at the Laurentian margin between the Early Ordovician and Early Devonian can be constrained. Several of the accreted terranes do not extend over the entire length of the orogen, with the result that the lines separating them change character along strike from terrane-bounding sutures to simple accretionary faults. The Ganderia domain consists of at least four separate terranes that share a common origin on the continental margin of Gondwana, but were separated by back-arc oceanic crust as they crossed the Iapetus Ocean and collided diachronously with the Laurentian margin.

Palaeolatitudinal distribution of lithologic indicators of climate in a palaeogeographic framework

AbstractWhether the latitudinal distribution of climate-sensitive lithologies is stable through greenhouse and icehouse regimes remains unclear. Previous studies suggest that the palaeolatitudinal distribution of palaeoclimate indicators, including coals, evaporites, reefs and carbonates, has remained broadly similar since the Permian period, leading to the conclusion that atmospheric and oceanic circulation control their distribution rather than the latitudinal temperature gradient. Here we revisit a global-scale compilation of lithologic indicators of climate, including coals, evaporites and glacial deposits, back to the Devonian period. We test the sensitivity of their latitudinal distributions to the uneven distribution of continental areas through time and to global tectonic models, correct the latitudinal distributions of lithologies for sampling- and continental area-bias, and use statistical methods to fit these distributions with probability density functions and estimate their high-density latitudinal ranges with 50% and 95% confidence intervals. The results suggest that the palaeolatitudinal distributions of lithologies have changed through deep geological time, notably a pronounced poleward shift in the distribution of coals at the beginning of the Permian. The distribution of evaporites indicates a clearly bimodal distribution over the past ~400 Ma, except for Early Devonian, Early Carboniferous, the earliest Permian and Middle and Late Jurassic times. We discuss how the patterns indicated by these lithologies change through time in response to plate motion, orography, evolution and greenhouse/icehouse conditions. This study highlights that combining tectonic reconstructions with a comprehensive lithologic database and novel data analysis approaches provide insights into the nature and causes of shifting climatic zones through deep time.

The Late Silurian Age of the Reference Aralaul Granosyenites–Granite Massif (Northern Kazakhstan)

This work presents the results of U–Pb geochronological studies of alkaline granites of the Aralaul complex of Northern Kazakhstan, which allow one to substantiate their Late Silurian (420 ± 4 Ma) age. Taking into consideration the previously obtained data, we propose a new development scheme of Paleozoic granitoid magmatism in Northern Kazakhstan, which includes Late Ordovician granite–granodiorite (Zerenda and Krykkuduk), Early Silurian granite–leucogranite (Borovoe and Karabulak), Late Silurian granosyenites–granite (Aralaul), and Early Devonian (Balkashino and Orlinogorsk) complexes.

First report of a Palaeozoic fenestrate bryozoan with an articulated growth habit

The main goal of this paper is the description of the erect articulated growth habit for the first time within the Palaeozoic Order Fenestrata, and the interpretation of its occurrence within the evolutionary history of colonial morphology in fenestrates. The present paper is based on a single specimen composed of fifteen disarticulated internodes. The specimen was extracted from the outcrop as two minute slabs, one of which was embedded in a two-component epoxy resin for preparation of acetate peels and the other one preserved without subsequent preparation for observation of exterior features. A new Devonian fenestrate bryozoan genus, Arnaopora, and its type species, A. sotoi, are described from the Emsian-Eifelian Moniello Formation (Asturias, NW Spain). Zooecial characters as well as the development of articulated colonies support the definition of this new genus, which is the first reported representative with an articulated growth habit in the Order Fenestrata, almost exclusively composed of rigidly erect unilaminar forms. The occurrence of Arnaopora in the early Eifelian coincides with a peak of disparity in fenestrate bryozoan growth forms during the transition between the Early and Middle Devonian. While all previously known morphological variations of growth forms in Palaeozoic fenestrates derive from the basic reticulate habit, articulation evolved from a rigidly branching phylloporinid ancestor. Arnaopora is extremely rare within the abundant and diverse bryozoan fauna of shallow platform facies where it occurs, which is in contrast with the relatively common presence of cellariform colonies in assemblages from modern shallow environments.

Deciphering interfungal relationships in the 410 million-year-old Rhynie chert: Glomoid spores under attack

Various types of other fungi colonize glomeromycotinan (Mucoromycota) spores in the Early Devonian Rhynie chert. However, relatively few of these associations have been described and evaluated in detail. One particular type of glomoid spore located in degrading land plant axes from the Rhynie chert provides evidence of (simultaneous) interaction with three different fungi. Massive callosities occur around the intrusion filaments of a chytrid-like parasite with epibiotic sporangia, while the hyphae of a delicate mycelial fungus extend into the spore lumen without triggering a recognizable host response. Several spores show large numbers of inwardly directed projections, which are regularly distributed and consist of a short hyphal branch encased in host wall material. The projections represent the penetration sites of a distinctive, mycelial fungus that forms a mantle-like hyphal sheath around the spores. This type of fungal interaction with glomeromycotinan spores has not previously been reported, and thus expands our knowledge of the numerous interfungal relationships that existed in early continental ecosystems.

Appendages, functional morphology and possible sexual dimorphism in a new ceratiocaridid (Malacostraca, Phyllocarida) from the Early Devonian Hunsrück Slate (south‐western Germany)

AbstractWe describe a new archaeostracan phyllocarid from the famous Early Devonian Hunsrück Slate, Germany. Morphological features suggest a new ceratiocaridid species for which we propose the name Ceratiocaris harpago sp. nov. The exceptionally well‐preserved holotype specimen is the most completely known ceratiocaridid with an almost entire set of appendages including biflagellate antenniform antennules, robust uniramous antennae with hook‐like flagellum, thoracopods densely covered with setae and probably six pairs of pleopods. A nectobenthic lifestyle is considered the most probable and the clasper‐like morphology of the antennae suggests the presence of a sexual dimorphism in this taxon, with the holotype specimen being a male individual.