Welsh Borderland Research Articles

The Radiolaria of the Herefordshire Konservat-Lagerstätte (Silurian), England

Abstract. Concretions of the Wenlock Series Herefordshire Konservat-Lagerstätte of the Welsh Borderland have yielded one of the few recorded Silurian radiolarian faunas world-wide and the only one known from the Silurian of Britain. The low diversity radiolarian fauna consists of new forms of Inaniguttidae (Inanihella sagena sp. nov. and Inanihella sp.), Haplentactiniidae (Haplentactinia armista sp. nov.) and a previously reported form of Secuicollactidae (Secuicollacta hexatinia (Won et al., 2002)). The fauna has affinities with Silurian radiolarian assemblages of the Urals, the Canadian Arctic and Alaska. Stratigraphically the Herefordshire fauna appears transitional between established Silurian radiolarian biozones.

A robust crinoid from the Llandovery (Lower Silurian) of Norbury, Shropshire: systematics, palaeoecology and taphonomy

Crinoids remain poorly known from the Llandovery of the British Isles despite disarticulated columnals being locally common. Cyclocyclicus (col.) geoffnewalli sp. nov. is based on common columnals and rarer pluricolumnals from Norbury quarry, south Shropshire (upper Llandovery, Telychian, Pentamerus Beds). It most probably represents a camerate or perhaps a cladid. The radial symplectial articulation of this species extends to the edge of the jugulum, claustra are sloping, there is no areola and the heteromorphic column, N212, has nodals with convex latera. Radice (=holdfast) ossicles are gracile, of similar morphology to columnals, but small and low. Cyclocyclicus (col.) geoffnewalli is a common component of the Pentamerus community at Norbury, where it dominated the sessile benthos with Pentamerus. Constrictions of the axial canal suggest that it contained only a limited amount of soft tissues whatever the diameter. Similar columnals are known from elsewhere in the Telychian of the Welsh Borderland, suggesting that C. (col.) geoffnewalli may have been distributed broadly in the shelly benthos of this region.

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.

Eurypterida (Chelicerata) from the Welsh Borderlands, England

Eurypterids from the Welsh Borderlands of England are redescribed from most available material. Hughmilleria banksii is here interpreted to represent a new genus. The poorly known Hughmilleria (?) acuminata (Salter, 1859a) is considered a junior synonym of H. banksii. Furthermore, Slimonia? stylops is suspected to be a junior synonym of Salteropterus abbreviatus, although they are not formally synonymized as the location of the only known specimen of S.? stylops is unknown. Morphological differences in carapace shape, eye position, walking leg, genital appendage and telson in H. banksii are noted compared to previous descriptions. A prosomal appendage earlier assigned to H. banksii is here assigned with caution to S. abbreviatus and the reported ‘segments’ in the posterior part of the telson of S. abbreviatus are shown to be cracks. The phylogenetic position of the new genus is inferred to lie between the Hughmilleria and the Slimonia/Salteropterus clades.

Single grain analysis of the Late Silurian spore Cymbosporites echinatus from the Welsh Borderland

The ultrastructure of the Late Silurian patinate spore Cymbosporites echinatus has been studied using single grain analysis, which allows individual specimens to be examined with light, scanning and transmission electron microscopy. In combination with serial sectioning this allows an extraordinarily thorough assessment of the ultrastructural variability to be made. C. echinatus has an unusual two-part spore wall; the thin inner exospore surrounds the entire spore, and the considerably thicker outer exospore, or patina, only covers the distal and equatorial walls of each trilete spore and tetrad. The patinate ultrastructure of C. echinatus is unlike any extinct or extant trilete spore yet examined, though it is most similar to early Paleozoic dyads and monads such as Dyadospora murusdensa and Laevolancis divellomedia. The occasional presence of lamellae in the inner exospore and the inner part of the distal patina suggest some variability in the timing of tetrad separation. This is not surprising given the dispersal of identical spores both singly and as tetrads.

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.

Structure and sequence of the Ingleton Group, basement to the central Pennines of northern England

SUMMARY The Ingleton Group is a sequence of steeply dipping turbiditic greywackes that crops out in two of the Craven inliers at the southern margin of the Askrigg Block, at Ingleton and in Ribblesdale. The structure has previously been interpreted as a series of concertina-like isoclinal folds, much more intense than the deformation recorded in Late Ordovician–Silurian strata of the overlying Windermere Supergroup. For this reason, the Ingleton Group was long regarded as late Precambrian in age. In 1982 the British Geological Survey (then Institute of Geological Sciences) assigned it to the early Ordovician on the basis of an acritarch assemblage recovered from a single borehole sample. This paper reports a resurvey based on the ample wayup evidence provided by turbidite bedforms. The greywackes are disposed in a large isoclinal fold pair, the previously recognized Skirwith Syncline in the Ingleton Inlier and the Horton Anticline mapped in Ribblesdale. Some 3 km of strata are exposed on the common limb, and assigned to five lithofacies. A start has been made on lithostratigraphical subdivision, three formations being recognized in the uppermost part of the succession. Isoclinal folding of the Ingleton Group predates the Acadian (Devonian) deformation of the overlying Silurian strata; the Acadian cleavage is superimposed obliquely across the isoclines and faces down on their inverted limbs. The group records a prelate Ordovician history comprising the deposition of penecontemporaneous continental volcanic arc detritus in a substantial turbidite basin, intrusion of mafic dykes, major folding and low-grade metamorphism, followed by deep erosion. Uncertainty about the depositional age of the Ingleton Group presents problems as to its affinities. Lithofacies and provenance characteristics match late Neoproterozoic Avalonian interarc basin deposits in the English Midlands and Welsh Borderland, but not the apparently contemporaneous Ordovician Skiddaw and Manx groups. Confirmation of an early Ordovician age would suggest that the deformation history of the Ingleton Group matches that of the Monian Supergroup of Anglesey. The problem is discussed in the context of Ordovician terrane assembly.

TELYCHIAN (LLANDOVERY, SILURIAN) BIVALVES FROM SPAIN

Abstract: Twenty species of bivalves (14 new) and 14 genera (six new) are described from two localities in the Silurian, upper Telychian, Oktavites spiralis Biozone of Spain: Cardavia cathleenae gen. et sp. nov., C. hafi sp. nov., C. stefani sp. nov.; Copenychia franta gen. et sp. nov., C. pristina sp. nov.; Stolidotus marco sp. nov.; Telycardia malinka gen. et sp. nov.; Silurinka vetula gen. et sp. nov.; Bolsopteria lentilka gen. et sp. nov.; Nennapteria ibericola gen. et sp. nov., N. ollicula sp. nov.; Actinopteria dakryodes sp. nov., A. isabelae sp. nov. and Dceruska hispanica sp. nov. They comprise two closely related communities, the Copenychia-Cardavia-Actinopteria Community and the Dceruska-Copenychia-Stolidotus Community, which belong to the Snoopyia Community Group. The occurrence of Dceruska Barrande, 1881, Dualina Barrande, 1881, Patrocardia Barrande, 1881, Silurinka, gen. nov., Slava Barrande, 1881 and Stolidotus Hede, 1915 in the Telychian of the Central Iberian Domain, Spain, supports palaeogeographical relationships with other Lower Silurian regions of north Gondwanan and Perunican Europe: the Carnic Alps (Austria), the Montagne Noire (France), Sardinia (Italy) and the Prague Basin (Bohemia), and also to Avalonia: the Welsh Borderland (Great Britain) and Baltica–Skåne (Sweden). These genera together with the new genera Cardavia, Copenychia (the earliest known representatives of the Silurian family Cardiolidae), Telycardia (the oldest known representative of the family Praecardiidae) and Silurinka belong to a Bohemian type of bivalve. Bolsopteria lentilka is closely related to Bolsopteria elliptica (Hind, 1910) from the Aeronian (middle Llandovery) of Scotland.

HUDDART, D. & GLASSER, N. F. 2002. Quaternary of Northern England. Geological Conservation Review Series Volume 25. xvi+745 pp. Peterborough: Joint Nature Conservation Committee; distributed by NHBS Ltd, 2–3 Wills Road, Totnes, Devon TQ9 5XN, UK. Price £70.00 (hard covers). ISBN 1 86107 490 5

Quaternary of Northern England is the latest addition to the Geological Conservation Review (GCR) Series. This series of books, 47 of which are planned, is dedicated to recording the features of interest and important conserved localities (the so-called Sites of Special Scientific Interest – SSSI) in Great Britain. The aim of this unique collection, that will eventually cover all the major geological and geomorphological topics in the British Isles, is to provide assessments of evidence from sites in a way that ‘the conservation value of the sites is clear’. This latest addition to the GCR Series is a substantial work by any standards, including 78 accounts of sites that provide the key evidence for the interpretation of the Quaternary environmental and climatic history of the region. The area covered by this volume extends from the Welsh Borderland and northern Lincolnshire in the south, north to …

Specific representation of the Silurian cephalopod genus Phragmoceras in Gotland and Britain

Species of Phragmoceras in the Silurian of Gotland and Britain are reviewed and revised. One new species P. exaggeratus is described from the Ludlow Series of the Welsh Borderland. There are comments on the broader distribution of the genus and on its mode of life.

Thelodonts and distribution of associated conodonts from the Llandovery–lowermost Lochkovian of the Welsh Borderland

Thelodont scales from the Middle Llandovery–lowermost Lochkovian of southern Britain are described with three new taxa, Loganellia? unispinata sp. nov., Nethertonodus prodigialis gen. et sp. nov. and Paralogania tarranti sp. nov. established, and Paralogania kaarmisensis Märss identified for the first time from Britain. Thelodonts are rare in the Llandovery and Wenlock series where predominantly Loganellia cf. aldridgei Turner, Loganellia scotica (Traquair) and Thelodus sp. are accompanied by coniform conodonts Panderodus Ethington, Decoriconus Cooper and Dapsilodus obliquicostatus (Branson and Mehl). The majority of the material has been recovered from the Ludlow and Přídolí series. Thelodus laevis (Pander) and Paralogania martinssoni (Gross) occur in the lower Gorstian. Paralogania kaarmisensis and Phlebolepis elegans Pander come from the Upper Gorstian–Lower Ludfordian and are associated with the zonal conodont Polygnathoides siluricus Branson and Mehl in the upper Gorstian. Thelodus parvidens Agassiz and T. trilobatus Hoppe dominate in the Upper Ludfordian in association with the rarer zonal conodonts Ozarkodina snajdri (Walliser), O. crispa (Walliser) and O. remscheidensis eosteinhornensis (Walliser). The basal Přídolí Series indicates a change to a thelodont fauna dominated by Paralogania ludlowiensis (Gross) and including Nethertonodus prodigialis. Higher in the Přídolí Series, a succession in faunas includes Katoporodus cf. timanicus (Karataju¯te‐Talimaa), Paralogania tarranti, Loganellia? unispinata and Goniporus alatus (Gross). In the highest Přídolí beds Paralogania kummerowi (Gross) and Loganellia cuneata (Gross) can be traced before the incoming of the lowermost Devonian taxon Turinia pagei (Powrie) along with Nikolivia gutta Karataju¯te‐Talimaa. Correlations with the Baltic are suggested from the Lower Ludlow, Upper Silurian, up to the Lower Lochkovian, Lower Devonian.

Silurian and Lower Devonian plant assemblages from the Anglo‐Welsh Basin: a palaeobotanical and palynological synthesis

AbstractA comprehensive survey of plant assemblages from Upper Silurian (Gorstian–Přídolí) and Lower Devonian (Lochkovian–Pragian) localities in South Wales and the Welsh Borderland is presented, together with some comments on recent improvements in dating and correlation. Spore assemblages provide a stratigraphic framework for plant evolutionary studies and, along with microvertebrates, enable correlation from continental to marine rocks, i.e. near‐shore to shelf deposits. While it is recognized that the assemblages provide the most complete and extensive record of the history of vascular plants in a restricted geographical area during the time interval, it seems likely that major evolutionary innovation occurred elsewhere. The plants themselves display a number of types of fossilization. Particularly important are the pyrite permineralizations which have helped in the elucidation of the ultrastructure of tracheids in early vascular plants. Minute, coalified, relatively uncompressed fossils (mesofossils) from the Přídolí Lochkovian of the Welsh Borderland are hypothesized to be the products of wildfire, the earliest records to date. In addition to displaying often exquisite anatomical detail, the sporangia contain spores which have been linked to those in dispersed assemblages. Such relationships are helpful in the reconstruction of local and regional vegetation, even in the absence of meso‐ and megafossils. However, because these fossils are allochthonous and preserved in fluvial sediments, the habitats of the plants remain uncertain. A new hypothesis suggests that interfluvial areas, where calcretes are interpreted as relicts of vertisols and a seasonally dry climate, provided refugia in the Lower Devonian for the cryptospore‐producing plants which dominated Ordovician and Lower Silurian land vegetation, while vascular plants colonized areas in the immediate vicinity of rivers. Variation in regional vegetation is explored via comparisons of composition of spore assemblages in southern Britain and Scotland and timing of appearances of derived taxa, integrated with limited information on the spore producers. Copyright © 2004 John Wiley & Sons, Ltd.

Bryozoa from the Much Wenlock Limestone (Silurian) Formation of the West Midlands and Welsh Borderland

Bryozoa from the Much Wenlock Limestone (Silurian) Formation of the West Midlands and Welsh Borderland

First Middle Ordovician biota from southern New Brunswick: stratigraphic and tectonic implications for the evolution of the Avalon continent

A limestone boulder in the Triassic Lepreau Formation near Saint John, New Brunswick, has yielded the first diverse marine fauna from the sub-Caradoc Ordovician of the western Avalon continent. This fauna includes the first Arenig conodonts recovered from Avalon and represents an unexposed interval in southern New Brunswick. Association of the conodonts Drepanoistodus and Baltoniodus and the trilobites Neseuretus, Nileus, and Stapeleyella emphasizes the faunal dissimilarity of Avalon and Laurentia through the late Middle Ordovician. Extension of the ranges of Neseuretus cf. Neseuretus parvifrons and Stapeleyella from Britain into New Brunswick further emphasizes that "eastern" and "western" Avalon were confluent parts of a unified, insular Avalon continent that originated in the latest Precambrian. This fauna correlates with the lower Amorphognathus (Lenodus) variabilis Zone (Kundan Stage) of Baltica and the terminal Arenig (upper Middle Ordovician; lower Darriwilian Stage) of Avalonian Britain. Available evidence suggests that an Arenig cover sequence with local shallow-water hematitic iron ore, quartz arenite, and rare limestone extended across the Avalonian marginal and inner platforms from eastern Newfoundland to the Boston, Massachusetts, region. This "western" Avalonian Arenig shows the greatest similarity with the Arenig of the Welsh Borderlands. Phosphatic fossils from the boulder have a thermal alteration index much lower than that of nearby lower Paleozoic outcrops and suggest derivation of the boulder from a weakly heated Avalonian succession brought into the Bay of Fundy region by post-Ordovician transcurrent faulting.

Diversity in conducting cells in early land plants and comparisons with extant bryophytes

Anatomical screening using scanning electron microscopy (SEM) of short lengths of smooth coalified axes (mesofossils) from a Lochkovian (Lower Devonian) locality in the Welsh Borderland, Shropshire has revealed extensive diversity in the architecture of centrally aggregated, elongate cells. At least 14 types have been discovered, each distinguished by variation in wall architecture and combination of the cells in the central strand. End walls have not been seen. These elongate cells may have smooth, uniformly thick or thin walls, walls with smooth projections either traversing or lining the lumen, or bilayered walls, the innermost perforated by pores of plasmodesmata dimensions. The latter type may be further divided on presence or absence of projections which may line the lumen, but usually cross it and are highly disorganized. Indeed, none of the cells shows the regularity associated with the secondary thickenings of tracheids, but the imperforate/pitted forms with projections superficially resemble the S-type tracheids of the Rhyniopsida in basic construction. Simply pitted types show greater similarity with the water-conducting cells (WCCs) of liverworts and Takakia. To facilitate direct comparison with bryophyte conducting elements, SEM studies were undertaken on the WCCs of a number of mosses and liverworts and on the leptoids of mosses, in conjunction with a range of degradation experiments designed to assess the fossilization potential of these cells. With the exception of polytrichaceous hydroids, the latter demonstrated the resilience of hydroids and leptoids to the chemical treatments. In addition, dehydration of the leptoids produced globular residues similar to those seen in some of the fossils. This combination of techniques raises the possibility that food-conducting cells might well be preserved in coalified fossils, and hence extends the interpretation of the functions of the elongate cells. Broadly speaking, imperforate bilayered examples may have been involved in water conduction, cells with globular residues with or without pitting involved in metabolite movement, and smooth walled examples with or without projections involved in support. The wider affinities of the plants which produced the axes remain equivocal and in the absence of sporangia it is impossible to assign them to a genus. However, this anatomical diversity in vegetative remains of extreme simplicity demonstrates far greater diversity in early land vegetation than is apparent from perusal of species lists.

Systematic position of Pollicina corniculum (Eichwald, 1860) (Mollusca, Tergomya) from the Middle Ordovician of the United Kingdom

Previously known only from the Middle Ordovician of the Baltic, Pollicina corniculum (Eichwald) is reported here from the Middle Ordovician of Wales and the Welsh Borderland. A review of the taxonomic position of Pollicina in the light of this new material combined with the recent redescription of the Russian type material suggests that it is best placed in the order Cyrtonellida of the molluscan class Tergomya.

New perspectives on Cooksonia from the Lower Devonian of the Welsh Borderland

New collections of coalified mesofossils of Cooksonia have been made from a Lochkovian (Lower Devonian) locality in Shropshire, England. They allow detailed description of sporangial anatomy in Cooksonia pertoni ssp. apiculispora with inferences for spore dispersal involving disintegration of the distal sporangial wall and maintenance of a rigid rim. Trilete spores, Aneurospora sp. and Streelispora newportensis have been recovered from the same sporangium. A new subspecies Cooksonia pertoni subsp reticulispora contains miospores with laevigate proximal surface bearing a simple triradiate apertural fold, equatorial crassitude and a coarse reticulum of muri on a slightly thickened distal wall. Spores are tentatively assigned to Synorisporites sp.. Cooksonia banksiisp. nov. is based on terminal sporangia in which the spore-containing area is enclosed within the expanded apex of the subtending axis. The cavity is lined by a smooth resilient acellular layer. Well-defined cells are apparent only in the pronounced sporangial rim. Spores are assigned to Ambitisporites avitus, a taxon of particular significance, because it is recorded in the Upper Ordovician and Lower Silurian assemblages which contain the earliest trilete monads. However, it is concluded that spores of such simple morphology may have been produced by a variety of taxa and that ultrastructural studies are necessary to confirm this possibility. These new specimens thus allow further insights into the disparity (via anatomy and in situ spores) of very simple plants and, in providing information on cell construction and arrangement, allow for functional interpretations, particularly relating to spore dispersal.

The early Silurian pentamerid brachiopodCostistricklandia canadensis(Billings, 1859) and its biostratigraphic and paleobiogeographic significance

Costistricklandiais a common, easily recognizable pentamerid brachiopod in upper Llandovery to lowest Wenlock rocks of eastern Laurentia, Avalonia and Baltica. In this paper, the poorly knownCostistricklandia canadensis(Billings) is re-described from the upper Telychian Rockway Dolomite of the Niagara Escarpment, Ontario. Compared to the relatively complete record of theStricklandia-Costistricklandiaevolution in the Welsh Borderland and the Baltic region, true representatives of theStricklandia lenslineage are sporadic in North America, including those from the Merrimack Formation of Anticosti Island, the Red Mountain Formation of Alabama, the Hopkinton Formation of Iowa, and the Nonda Formation of the northern Rocky Mountains. Although the exact mode of speciation in theStricklandia-Costistricklandiaand thePentamerus-Pentameroidestransitions remains debatable, the common association ofCostistricklandiaandPentameroidesmake them a useful concurrent biozone for correlating middle to upper Telychian rocks of North America and Europe. Paleobiogeographically, thePentameroides-CostistricklandiaFauna marks the third major pulse of pentamerid faunal migration between Laurentia and its adjacent paleo-plates during the Early Silurian, following the limited intercontinental dispersal of the early LlandoveryVirgianaFauna and the quasi-cosmopolitan dispersal of the middle LlandoveryPentamerusFauna.

Late Ordovician brachiopod communities of southeast China

The Upper Ordovician (mid-Ashgill) Xiazhen and Changwu formations in the Zhejiang-Jiangxi border region of southeastern China contain an abundant and diverse suite of brachiopods. A cluster analysis of 59 key samples from 180 collections (over 23 000 specimens) allowed delineation of eight distinct brachiopod communities, herein named the Ectenoglossa minor Community, the Eospirifer praecursor Community, the Ovalospira dichotoma Community, the Antizygospira liquanensis – Sowerbyella sinensis Community, the Kassinella shiyangensis Community, the Altaethyrella zhejiangensis Community, the Tcherskidium jiangshanensis Community and the Foliomena folium Community. These communities occur predominantly in limey, clayey, to silty mudstone facies, similar to Ziegler's Early Silurian brachiopod communities in the Welsh Borderland. On the basis of lithological, faunal, and paleogeographical evidence, the eight communities are interpreted to have distributed along an onshore–offshore gradient from BA1 to BA6 settings on the northeastern margin of the Zhe-Gan Platform. In a broad paleo-embayment and mixed carbonate–siliciclastic shelf setting, the distribution of the eight brachiopod communities appears to have been controlled primarily by water depth because a given brachiopod community can be found in different lithofacies. Substrate types, however, must have played an important role, as some of the communities show preferred lithofacies. This study shows that the ecological zonation and community organization of the Late Ordovician pre-extinction brachiopods were similar to those of Early Silurian post-extinction brachiopods, although pronounced brachiopod provincialism during the Ashgill makes it difficult to directly correlate these communities with coeval brachiopod communities reported from other paleo-plates.

Miospore assemblages from the Silurian–Devonian boundary, in borehole A1-61, Ghadamis Basin, Libya

Well preserved and diversified miospore assemblages have been recorded from a relatively continuous sequence in borehole A1-61 which spans the Silurian–Devonian boundary in the northwestern part of the Ghadamis Basin, Libya. The sequence is represented by early Devonian Lochkovian beds of the Tadrart Formation that transgress onto the Silurian Ludlow-Pridoli beds of the upper part of the ‘Alternances Argilo-gréseuses’ Formation. The present work demonstrates a succession of miospore assemblages from closely sampled layers that have been stratigraphically dated as Ludlow–middle Pridoli and early Lochkovian by chitinozoans and acritarchs. Over 80 species of cryptospores and trilete spores have been identified. Modified detailed morphological interpretations are given. The miospore assemblages are correlated with miospore zonation schemes established for the type sequences of the Welsh Borderland, and those previously described from Libya. Early occurrences of some species as Streelispora newportensis on the western Gondwana plate, are put forward by comparison with the Old Red Sandstone continent. Phytogeographic and palaeobotanic implications based on these observations are discussed.