Red Sandstone Continent Research Articles

The last pteraspids (Vertebrata, Heterostraci): new material from the Middle Devonian of Alberta and Idaho

AbstractThis report documents the last pteraspids, (armored, jawless members of the Heterostraci), which are otherwise only known from the Early Devonian of the Old Red Sandstone Continent. Tuberculate pteraspid heterostracans are described from the Middle Devonian beds of two formations in western North America. The late Givetian Yahatinda Formation of Alberta and British Columbia consists of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments. Clavulaspis finis (Elliott et al., 2000a) new combination is redescribed from additional material from the Yahatinda Formation and reassigned to the new genus Clavulaspis because the original genus name is invalid. The Eifelian Spring Mountain beds of Idaho consist of a large channel that represents a clastic-dominated estuarine environment. It contains Scutellaspis wilsoni new genus new species, and the previously described species from the Spring Mountain beds is redescribed and reassigned to Ecphymaspis new genus, which was prompted by new material and a review of the validity of the original genus name. Phylogenetic analysis shows that these three new taxa form part of the derived clade Protaspididae.UUID: http://zoobank.org/9cf09b21-cec1-4ce4-bc2b-658d0b515e10

Stem chondrichthyan microfossils from the Lower Old Red Sandstone of the Welsh Borderland

Placoid and polyodontode scales of stem chondrichthyans have been found in the early Lochkovian “Ditton Group” of the Brown Clee Hill district, Shropshire, England and at Talgarth, south Wales. One of the forms is assigned to a new species of Altholepis Karatajūtė-Talimaa, 1997, a genus already recognised from Lochkovian shallow marine deposits in Celtiberia, Spain and the Northwest Territories, Canada as well as the type locality in Podolia, Ukraine. Altholepis salopensis sp. nov. is based on small polyodontode scales with typically three to eight high odontodes; the scale form was previously considered to belong to acanthodian “ Nostolepis ” robusta (Brotzen, 1934). The structure of other scales formerly assigned to “ Nostolepis ” robusta has led us to erect a new genus Jolepis for this scale form, which differs from Altholepis in lacking an ordered layout of odontodes . Jolepis robusta (Brotzen, 1934), originally (and possibly still) considered to be an acanthodian, is also known from the Baltic countries, Russia, and northern Germany (ex erratic limestones). Scales of acanthodian Parexus recurvus Agassiz, 1845, and/or possibly from the stem chondrichthyan Seretolepis elegans Karatajūtė-Talimaa, 1968 (scales of these two taxa are barely distinguishable), and of stem chondrichthyan Polymerolepis whitei Karatajūtė-Talimaa, 1968 are also present. Altholepis , Jolepis gen. nov., Seretolepis Karatajūtė-Talimaa, 1968 and Polymerolepis Karatajūtė-Talimaa, 1968 are found in marine deposits elsewhere; the British occurrence of these taxa adds to the debate on the sedimentological origins of the Lower Old Red Sandstone deposits in the Welsh Borderland. The geographic range of several early sharks is now known to extend around the Old Red Sandstone continent and beyond.

Middle Devonian coccosteid (Arthrodira, Placodermi) biostratigraphy of Scotland and Estonia

A coccosteid nuchal bone from the Middle Devonian Tamme Cliffs locality in Estonia is described as Dickosteus cf. threiplandi , D . threiplandi being a common species in the Middle Devonian of the Orcadian Basin, Scotland. A number of other bones from Tamme Cliffs are also placed in this genus. It is already known that the coccosteids Coccosteus cuspidatus and probably Millerosteus minor are present in both areas. A final coccosteid genus Watsonosteus has been shown previously to also be present in both areas. We can confirm that the sequence of coccosteid genera is the same in both the Orcadian Basin and Estonia and is, from the lowest horizon, Coccosteus – Dickosteus – Millerosteus – Watsonosteus . The coccosteids in Estonia are also associated with other Scottish faunal elements (including co-specific species), such as other placoderms, acanthodians and sarcopterygians. This implies a very close connection between the two areas in the Middle Devonian. Some of the acanthodian species of the Orcadian Basin are also present in Belarus and Severnaya Zemlya, suggesting that other Orcadian Basin forms, including coccosteids may be present at these localities and perhaps elsewhere on the Old Red Sandstone continent. Further investigation may allow a continent-wide correlation at species level across the whole continent.

Welsh Borderland bouillabaisse: Lower Old Red Sandstone fish microfossils and their significance

Fish remains from over 100 localities in the Upper Silurian to Lower Devonian (traditional Lower Old Red Sandstone: LORS: Přidolí–Pragian) of Wales and the Welsh Borderland Anglo-Welsh Basin, southwest Britain have been investigated. Work on microfossils of fish (‘microvertebrates’, generally <5–8mm) is reviewed, covering agnathan thelodonts, heterostracans, cephalaspids, anaspids, and gnathostomes including acanthodians, placoderms, and chondrichthyans, including the first from Pembrokeshire. Scales of the following taxa are newly identified: acanthodians Euthacanthus sp., Nostolepis musca, Parexus recurvus and Cheiracanthoides sp. cf. C. rarus; early “sharks” including Altholepis sp.; and a (?)radotinid placoderm. Species ranges in space, time and environment reveal interesting patterns, the most significant being a wide geographic distribution, which does not support a wholly freshwater provenance for the Anglo-Welsh Basin; endemic taxa are few. Using the International mid-Palaeozoic Microvertebrate zonal scheme, the presence of a Thelodus parvidens–Paralogania ludlowiensis-osteostracan Assemblage within the Ludlow Bonebed at the base of the former Downton Group (now in part in the new lithostratigraphically defined Daugleddau Group) supports a basal Přidolí age for the member. A mid-Přidolí dearth with few taxa, mainly acanthodians and cephalaspids is followed by an upper Přidolí Trimerolepis–Paralogania kummerowi–Loganellia cuneata-poracanthodid-Toombsaspis pococki Assemblage. The Silurian–Devonian boundary is equated with the appearance of Turinia pagei and associated taxa including Phialaspis symondsi at a level about 30m below the local Chapel Point Limestone. This biozone can be correlated across the Old Red Sandstone continent. All vertebrate species including newly recognised Lochkovian chondrichthyans indicate marine environments were present in the LORS.

A new Early Devonian (Emsian) arthrodire from the Northwest Territories, Canada, and its significance for paleogeographic reconstruction

An heterostiid arthrodire, Herasmius dayi sp. nov., is described from upper Lower Devonian marine deposits of the Bear Rock Formation along the Anderson River, Northwest Territories, Canada. New elements described for the genus for the first time include the suborbital, submarginal (also new for the family Heterostiidae), the lateral shoulder girdle with posterior lateral, anterior dorso-lateral, and posterior dorso-lateral plates and possible infragnathal plate. We present a new reconstruction of the cranial region of Herasmius, previously known only from supposedly freshwater – shallow marine deposits of roughly the same age in the Wood Bay Group of Spitsbergen. The late Early Devonian fishes that are common to the Arctic region of northwestern Canada and the island of Spitsbergen in the Svalbard archipelago of Norway, the porolepiform Heimenia and the arthrodire Herasmius described here, demonstrate the existence of a barrier-free paleogeographic connection between those continental blocks by the late Early Devonian. Comparison of the entire Anderson River vertebrate fauna with other boreal faunas of similar age indicates additional paleogeographic connections north of and around the Old Red Sandstone Continent to the Baltic region, central Europe, and even to the New Siberian Islands and South China, in contrast to most current published paleogeographical reconstructions.

Comparison of the vertebrate faunas of the Lower Old Red Sandstone of the Anglo-Welsh Basin with contemporary faunas in Scotland

The Lower Old Red Sandstone terranes of the Midland Valley of Scotland and the Anglo-Welsh Basin have been considered as separate realms due to the rarity of fish species common to both areas. Although in the first half of the 19th century the osteostracan Cephalaspis lyelli was thought to occur in both terranes this was shown in be incorrect in the latter part of that century. It was not until 1968 that it was demonstrated that the thelodont agnathan Turinia pagei occurred in both terranes. This species has a much wider distribution across the whole of the Old Red Sandstone continent, but its presence in both realms indicates they were connected either directly or indirectly. In 2012 it was suggested that the osteostracan Janaspis watsoni might be present in both basins and in 2013 the acanthodian Parexus recurvus was shown to definitely occur in both. Here we show that other acanthodian genera and species were present in both regions during the Lochkovian (earliest Devonian). Co-specific plants also occur in both terranes during the Lochkovian. As there is no evidence of a marine connection to the Midland Valley in the Lochkovian, the only logical conclusion is that the connection between the two terranes was fluvial.

Heterostracan vertebrates and the Great Eodevonian Biodiversification Event—an essay

The oldest vertebrates are Early Cambrian, cephalized unossified species (craniates) from China. The oldest armoured species (euvertebrates) are Ordovician in age. After Talimaa’s Gap, vertebrates have their first adaptive radiation during the Silurian when jawless species (“ostracoderms”) are dominant and their second radiation during the Devonian when jawed species (gnathostomes), and particularly placoderms (armoured fishes), are dominant. A Lochkovian peak of diversity is registered in various Lower Devonian siliciclastic series all around the Old Red Sandstone Continent and Siberia, for ostracoderms in general, and heterostracan pteraspidomorphs in particular. It occurs at different time slices in the Lochkovian, depending on the localities, and may be followed by another smaller peak in the Pragian. Both events correspond to the rise of the Devonian Nekton Revolution as defined for marine invertebrates. This appears to be the second main biodiversification event in the Palaeozoic, following the Great Ordovician Biodiversification Event or GOBE, when euvertebrates appeared. Taking into account most recent palaeobiological studies on heterostracans that suggest they were microphagous suspension feeders or feeding upon microscopic epiphytes from filamentous algae, the origin of this Great Eodevonian Biodiversification Event (GEBE) of heterostracans is questioned. Both abiotic (sea level, tectonic events, climatic changes—oceanic oxygenation and temperature, continental surface temperature) and biotic (plankton diversity, marine primary productivity, competition with vertebrates and invertebrates, including eurypterids, macroecological turnover) factors are examined. No plausible global evolutionary scenario seems to be presently available.

The Boothiaspidinae, a new agnathan subfamily (Heterostraci, Cyathaspididae) from the late Silurian and Early Devonian of the western United States and the Canadian Arctic

AbstractThree new species of the new genusPhyllonaspisare described from Early Devonian localities in the western United States.Phyllonaspis laevis,P.serratus, andP.taphensisare broad, flattened cyathaspids with lateral brims and fine dermal ornament, that show a close relationship to the cyathaspidsBoothiaspisandAlainaspisfrom the late Silurian and Early Devonian of the Canadian Arctic. These taxa are here accommodated within the new subfamily Boothiaspidinae within the family Cyathaspididae. This relationship supports previous evidence of faunal connection between these two areas and indicates dispersal around the Old Red Sandstone Continent from a center in the Canadian Arctic. Isolated oral plates allow a reconstruction of the oral cover and increase our knowledge of the range of oral structures in this family.

Lacustrine Deposits In the Karheen Formation Fortify Links Between Alaska's Alexander Terrane and the Old Red Sandstone Continent In the Late Silurian–Early Devonian

The Karheen Formation of southeastern Alaska (Alexander terrane) is an 1800-m-thick redbed molasse sequence that formed during the Late Silurian–Early Devonian in the wake of the Klakas orogeny. Previous research interpreted thin, platy limestone in the Karheen Formation as marine in origin. We describe new evidence, including a lack of marine fossils, which indicates that the rhythmically laminated limestone formed in deep, stratified lakes. Intercalated siliciclastic, lake-margin facies record cycles of lake expansion and contraction. Comparative analysis with coeval Lake Orcadie deposits in Scotland shows that the Karheen Formation is strikingly similar in age, thickness, lithology, paleontologic characteristics, and tectonic setting to the Old Red Sandstone. Together with other published geologic data from southeastern Alaska, the Karheen's lacustrine deposits strengthen paleogeographic connections between the Alexander terrane and the N. Atlantic–Caledonide region in the mid-Paleozoic.

Spore assemblages from the Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Northern Highlands of Scotland: the Berriedale Outlier

ABSTRACTAssemblages of well-preserved dispersed spores have been recovered from the ‘Lower Old Red Sandstone’ deposits of the Berriedale Outlier in the Northern Highlands of Scotland. They belong to the annulatus–sextantii Spore Assemblage Biozone (AS SAB), in the spore zonation of Richardson &amp; McGregor (1986), indicating an Early Devonian Emsian (but not earliest Emsian or latest Emsian) age. Comparison with the spore zonation of Streel et al. (1987) suggests they may be confined to the annulatus–bellatulus Oppel Zone (AB OZ), further constraining the age to early Emsian. This new biostratigraphical datum provides an age constraint for the onset of ‘Lower Old Red Sandstone’ sedimentation in the Orcadian Basin and, in particular, northwest of the Great Glen Fault System on the Northern Highlands. In the Orcadian Basin, there is a gap between ‘Lower Old Red Sandstone’ and ‘Middle Old Red Sandstone’ sedimentation, represented by either unconformity or disconformity, which appears to be variable in duration. In the Berriedale Outlier, it is estimated to represent up to 16 million years, but with an unknown thickness of ‘Lower Old Red Sandstone’ sequence removed at the unconformity. However, this basin-wide unconformity/disconformity is likely due to minor, local rather than large-scale, regional tectonism, and the evidence suggests little, if any, syn-depositional strike-slip movement along the Great Glen Fault System during Devonian ‘Old Red Sandstone’ deposition. The described spore assemblage is the most diverse AS SAB/AB OZ assemblage described from the British Isles. However, compared to contemporary spore assemblages from elsewhere on the Old Red Sandstone continent, the Scottish material is rather depauperate, with certain key taxa absent. This probably reflects subtle ecological effects, with the Scottish material representing restricted floras of the inland intermontaine basins.

Palaeoenvironments of Early Devonian fish and other aquatic fauna of the Campbellton Formation, New Brunswick, Canada

The palaeoecology and palaeoenvironments of the classic fish-bearing strata of the Campbellton Formation are here described. A well-documented fossil assemblage includes acanthodian, placoderm, chondrichthyan, and cephalaspid fishes, tracheophyte remains, eurypterids, ostracods, and molluscs. As part of the Old Red Sandstone continent, the Emsian Campbellton Formation occupied a small basin within the mountainous terrain of the Acadian Orogen, and may have connected through a narrow seaway to a closing foreland basin. The highest diversity of vertebrate fossils was found above a basal unconformity with Val d'Amour Formation volcanics, marked by fissure-fills and unstratified breccia representing a craggy, irregular palaeosurface that provided shelter for some fauna and sediment for rapid burial of skeletal remains. Overlying prodeltaic calcareous siltstones are also highly fossiliferous, and represent a low energy habitat. Occurrences of pterygotid eurypterids, cephalaspids, and chondrichthyans in deltaic sandstones, place these taxa in a habitat that may have been variably fresh or brackish. The surrounding landscape was vegetated with primitive tracheophytes, and abundant plant debris is preserved throughout the basin. The diverse assemblage of fish, arthropods, gastropods, plants and microbial growths suggests that a trophically complex ecosystem was in existence.

The biostratigraphical distribution of earliest tetrapods (Late Devonian): a revised version with comments on biodiversification

Abstract The 13 presently known genera of Late Devonian tetrapods are situated in the recently completed miospore zonation of Western Gondwana and Euramerica, in relation to the standard conodont zonation. Some of them are still unprecisely dated. The stratigraphic sequences of East Greenland, North China and East Australia are briefly reviewed to discuss the age of the tetrapods collected there and to analyse consequences in relation to the Frasnian–Famennian and Devonian–Carboniferous boundaries. Two episodes of biodiversification seem to have occurred: the first in the Frasnian and the second in the late and latest Famennian. Due to the currently known fossil evidence, the consensus scenario advocates a late Middle Devonian to early Late Devonian origin of tetrapods on the Old Red Sandstone Continent (Euramerica) at a time of warm climate and recovering atmospheric oxygen level during the building of a pre-Pangaean configuration of landmasses.

Discovery of the arthrodire genus Actinolepis (class Placodermi) in the Middle Devonian of Scotland

Synopsis A single specimen of the placoderm Actinolepis found in the Middle Devonian (Eifelian) Achanarras fish bed of Achanarras Quarry, Caithness, is the first record of the genus in the Devonian of Scotland. The articulated specimen displays an external view of the dorsal armour. Two species of Actinolepis are known from the Middle Devonian of the Baltic: Actinolepis tuberculata and Actinolepis magna. This find strengthens the faunal connection between the Baltic area and northern Scotland in Eifelian and Givetian times, which is supported by other species common to both areas, such as the arthrodire Millerosteus minor. Both areas were connected, perhaps at different times, to the same marine area. The most likely connection is to the Rheic Ocean to the south, but another possible connection lies between Laurentia and Baltica to an ocean to the north. Migration of fish into the Old Red Sandstone continent was controlled by long-term climatic cycles. When lake basins overflowed at times of high runoff, fish could migrate to internal continental basins through river systems. During dryer and hotter periods lake basins became isolated and fish evolved in non-marine waters, isolated from marine conditions, possibly explaining the minor differences in fish species from widely separated basins.

Siluro-Devonian miospore biostratigraphy of the Urubu River area, western Amazon Basin, northern Brazil

Well-preserved miospores have been observed in the Urubu River area from the western part of the Amazon Basin, northern Brazil, in rocks belonging to the uppermost Pitinga and Manacapuru Formations. A previous palynological work based on chitinozoans has dated these strata as Late Ludlow, Early Pridoli and Early Lochkovian. Although samples are relatively poor in miospores, the present study reveals the most diversified Silurian–Earliest Lochkovian palynoflora ever reported from South America, an interval where miospore information is still very rare. Sixty-four species have been identified, of which two are new ( Artemopyra urubuense and Retusotriletes amazonensis). One single specimen attributed to the genus Grandispora, identical to unpublished forms identified by one of us (P.S.) in Lochkovian sections of Saudi Arabia, has been found in a Lochkovian sample from the Urubu River. These constitute the oldest geological record of Grandispora. Among the abundant acritarchs, specimens of the genus Schizocystia have been observed for the first time in pre-Devonian rocks. Although the Late Silurian–Early Lochkovian miospore biostratigraphy is still in its infancy in South America, it seems that Amazon Basin assemblages do not show significant differences in composition in comparison to coeval palynofloras from other areas of northwestern Gondwana. This is surprising since the miospore localities under consideration are widely distributed over high to low paleolatitudes, i.e. from cool temperate to dry subtropical belts. Conversely, Siluro-Devonian Gondwanan assemblages differ considerably from the contemporary palynofloras of the Old Red Sandstone Continent and adjacent areas, thus contradicting recent phytogeographic interpretations based on megafloras.

Palaeophytogeographical and palaeoecological implications of a miospore assemblage of earliest Devonian (Lochkovian) age from Saudi Arabia

Palynological samples from two boreholes drilled in the eastern part of Saudi Arabia contain a rich assemblage of cryptospores and trilete spores. They are dated as most probably Lochkovian in age. Intriguingly, the cryptospores are very similar to those from a coeval continental palynomorph assemblage from the Old Red Sandstone Continent, whereas the trilete spores show a strong affinity with miospore assemblages from Western Gondwana. It is suggested that cryptospore-producing plants inhabited confined, damp biotopes and had a wide range of climatic tolerance. On the other hand, trilete spore-producing plants inhabited a wider variety of biotopes but were more sensitive to climatic variations. The high degree of similarity between Old Red Sandstone and Saudi Arabian cryptospore assemblages favours palaeogeographic reconstructions where there is close proximity between Western Gondwana and Euramerica and/or a land connection between these palaeoplates. Climatic differences between the Old Red Sandstone Continent and the northern part of Western Gondwana can be invoked to explain the variations in the trilete spore assemblages.

Recognizing the Kačák Event in the Devonian terrestrial environment and its implications for understanding land–sea interactions

Abstract The Kačák Event is a late Eifelian (Mid-Devonian) episode of marine dysoxia/anoxia with associated extinctions. It has been widely recognized in the shelf seas that surrounded the Old Red Sandstone continent. It was contemporary with the lacustrine Orcadian Basin in Scotland. This basin contains the distinctive Achanarras lake horizon that contains a rich and diverse fish fauna. The Achanarras lake was wide and deep and would have been filled by rainfall from a monsoon system at an insolation maximum. Faunal elements within the lake are in common with the Kernavė Member in Estonia and this level can be conodont dated as late Eifelian eiflius or ensensis Zone. Therefore the group of lacustrine flooding climatic events that occur at and above the Achanarras level can be correlated with the marine Kačák Event ( sensu lato ) and both can be regarded as having a common climatic cause and driven by an insolation maximum. A reconstruction of the Orcadian Basin drainage system and a water balance model based on the calcium flux within the lake shows that a very significant volume of water would have been seasonally discharged to the Rheic Ocean and would have caused an additional environmental effect.

Danziella artesiana, a new name for Zosterophyllum artesianum from the Lower Devonian of Artois, northern France

A reinvestigation of the Lower Devonian plant, Zosterophyllum artesianum Danzé-Corsin 1956, based on original collections and undescribed material leads to the erection of a new taxon, Danziella artesiana. The genus shares with Zosterophyllum smooth axes with lateral stalked sporangia comprising two equal valves, but in the French plant the stalks, attached at right angles to the fertile axes, are long and straight. Distal dehiscence occurs in the same plane of compression as the subtending axis. Sporangia are attached at irregular intervals and there is no well-defined spike. Anatomical evidence that would confirm affinity with the Zosterophyllales is lacking in these compression fossils. Consideration is also given to its relationship to taxa such as Renalia Gensel that appear to share characters with zosterophylls and rhyniophytes, with consensus that a basal position in the former seems more likely. However the age of the fossils, (Pragian–Emsian), based indirectly on spores, fish and field relationships, postdates that of the major radiation of zosterophylls elsewhere on the Old Red Sandstone Continent.

NEW FLAT-BACKED ARCHIPOLYPODAN MILLIPEDES FROM THE UPPER DEVONIAN OF NORTH AMERICA

Two new flat-backed archipolypodan millipede taxa, Orsadesmus rubecollus n. gen. and sp. and Zanclodesmus willetti n. gen. and sp., are described from the Upper Devonian of Clinton County, Pennsylvania, and Miguasha, Quebec, respectively. These new taxa are placed in the new family Zanclodesmidae within the order Archidesmida. Archidesmida have previously only been described from the United Kingdom, and their presence in North America confirms a geographic continuum in the millipede fauna across the Old Red Sandstone Continent during the Devonian.

Morphometric analysis of proposed evolutionary lineages of Early Devonian land plant spores

Early Devonian miospore assemblages from ‘La Gileppe’ (Eastern Belgium) include five varieties of trilete spore belonging to the genus Emphanisporites. These five varieties show a continuous variation of their morphological characteristics. The variation in morphological characteristics can be related to the evolution of morphological features and allows us to define the Emphanisporites micrornatus Morphon. A statistical evaluation of this population highlights the interdependence of almost all morphological parameters. This study proves the increase in size of ornamental and structural parameters over several million years. The biometric changes and the progressive replacement of older morphotypes by younger ones indicate that a temporal link exists between these different varieties. Two phylogenetic hypotheses for the E. micrornatus Morphon are proposed. This morphological evolution is so far observed only on the Eastern Old Red Sandstone Continent and defines a palaeophytogeographic sinuosus–zavallatus Province.

An articulated phyllolepid fish (Placodermi) from the Devonian of central Australia: implications for non-marine connections with the Old Red Sandstone continent

A second species of the placoderm genus Placolepis (Pl. harajica sp. nov.), based on a single articulated specimen from Givetian–Frasnian strata in the MacDonnell Ranges, demonstrates the occurrence of this taxon across the Australian craton. Placolepis (order Phyllolepida) is endemic to east Gondwana, and other phyllolepids are widespread in the Givetian and younger of Gondwana (Australia, Antarctica, Turkey, Venezuela), but do not occur until Late Devonian (Famennian) time in the Northern Hemisphere (Europe, Russia, Greenland, North America). The disjunct space–time distribution of the Phyllolepida is inconsistent with palaeomagnetic evidence indicating a wide equatorial ocean between Gondwana and Laurussia in Late Devonian time. This new species provides additional evidence supporting a Gondwana origin for the group, and later access to northern landmasses resulting from closure of the ocean between Gondwana and Laurussia and continental connection at or near the Frasnian–Famennian boundary.