| 1. |
- Ahlberg, Per, 1963-
(författare)
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Follow the footprints and mind the gaps : a new look at the origin of tetrapods
- 2019
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - : CAMBRIDGE UNIV PRESS. - 1755-6910 .- 1755-6929. ; 109:1-2, s. 115-137
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis that tetrapods evolved from elpistostegids during the Frasnian, in a predominantly aquatic context, has been challenged by the discovery of Middle Devonian tetrapod trackways predating the earliest body fossils of both elpistostegids and tetrapods. Here I present a new hypothesis based on an overview of the trace fossil and body fossil evidence. The trace fossils demonstrate that tetrapods were capable of performing subaerial lateral sequence walks before the end of the Middle Devonian. The derived morphological characters of elpistostegids and Devonian tetrapods are related to substrate locomotion, weight support and aerial vision, and thus to terrestrial competence, but the retention of lateral-line canals, gills and fin rays shows that they remained closely tied to the water. Elpistostegids and tetrapods both evolved no later than the beginning of the Middle Devonian. The earliest tetrapod records come from inland river basins, sabkha plains and ephemeral coastal lakes that preserve few, if any, body fossils; contemporary elpistostegids occur in deltas and the lower reaches of permanent rivers where body fossils are preserved. During the Frasnian, elpistostegids disappear and these riverine-deltaic environments are colonised by tetrapods. This replacement has, in the past, been misinterpreted as the origin of tetrapods.
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| 2. |
- Chen, Dong Lei, 1985-, et al.
(författare)
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A partial lower jaw of a tetrapod from "Romer's Gap"
- 2018
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 108:1, s. 55-65
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Tidskriftsartikel (refereegranskat)abstract
- The first half of the Mississippian or Early Carboniferous (Tournaisian to mid-Visean), an interval of about 20 million years, has become known as "Romer's Gap" because of its poor tetrapod record. Recent discoveries emphasise the differences between pre-"Gap" Devonian tetrapods, unambiguous stem-group members retaining numerous "fish" characters indicative of an at least partially aquatic lifestyle, and post-"Gap" Carboniferous tetrapods, which are far more diverse and include fully terrestrial representatives of the main crown-group lineages. It seems that "Romer's Gap" coincided with the cladogenetic events leading to the origin of the tetrapod crown group. Here, we describe a partial right lower jaw ramus of a tetrapod from the late Tournaisian or early Visean of Scotland. The large and robust jaw displays a distinctive character combination, including a significant mesial lamina of the strongly sculptured angular, an open sulcus for the mandibular lateral line, a non-ossified narrow Meckelian exposure, a well-defined dorsal longitudinal denticle ridge on the prearticular, and a mesially open adductor fossa. A phylogenctic analysis places this specimen in a trichotomy with Crassigyrinus and baphetids + higher tetrapods in the upper part of the tetrapod stem group, above Whatcheeria, Pederpes, Ossinodus, Sigournea and Greererpeton. It represents a small but significant step in the gradual closure of "Romer's Gap".
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| 3. |
- Hall, Adrian M., et al.
(författare)
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Early and Middle Pleistocene environments, landforms and sediments in Scotland
- 2019
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 110:1-2, s. 5-37
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from Scotland into the North Sea but only 4-5 advances have been identified from the terrestrial stratigraphy. Two primary modes of glaciation, mountain ice cap and full ice sheet modes, can be recognised. Different zones of glacial erosion in Scotland reflect this bimodal glaciation and the spatially and temporally variable dynamics at glacier beds. Depths of glacial erosion vary from almost zero in Buchan to hundreds of metres in glens in the western Highlands and in basins both onshore and offshore. The presence of tors and blockfields indicates repeated development of patches of cold-based, non-erosive glacier ice on summits and plateaux. In lowlands, chemical weathering continued to operate during interglacials, but gruss-type saprolites are mainly of Pliocene to Early Pleistocene age. The Middle Pleistocene terrestrial stratigraphic record in Scotland, whilst fragmentary and poorly dated, provides important and accessible evidence of changing glacial, periglacial and interglacial environments over at least three stadial-interstadial-interglacial cycles. The distributions of blockfields and tors and the erratic contents of glacial sediments indicate that the configuration, thermal regime and pattern of ice flow during MIS 6 were broadly comparable to those of the last ice sheet. Improved control over the ages of Early and Middle Pleistocene sediments, soils and saprolites and on long-term rates of weathering and erosion, combined with information on palaeoenvironments, ice extent and sea level, will in future allow development and testing of new models of Pleistocene tectonics, isostasy, sea-level change and ice sheet dynamics in Scotland.
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| 4. |
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| 5. |
- Kamska, Viktoriia, et al.
(författare)
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Long-bone development and life-history traits of the Devonian tristichopterid Hyneria lindae
- 2019
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - : CAMBRIDGE UNIV PRESS. - 1755-6910 .- 1755-6929. ; 109:1-2, s. 75-86
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Tidskriftsartikel (refereegranskat)abstract
- Hyneria lindae is one of the largest Devonian sarcopterygians. It was found in the Catskill Formation (late Famennian) of Pennsylvania, USA. The current study focuses on the palaeohistology of the humerus of this tristichopterid and supports a low ossification rate and a late ossification onset in the appendicular skeleton. In addition to anatomical features, the large size of the cell lacunae in the cortical bone of the humerus mid-shaft may suggest a large genome size and associated neotenic condition for this species, which could, in turn, be a partial explanation for the large size of H. lindae. The low metabolism of H. lindae revealed here by bone histology supports the hypothesis of an ambush predatory behaviour. Finally, the lines-of-arrested-growth pattern and late ossification of specimen ANSP 21483 suggest that H. lindae probably had a long juvenile stage before reaching sexual maturity. Although very few studies address the life-history traits of stem tetrapods, they all propose a slow limb development for the studied taxa despite different ecological conditions and presumably distinct behaviours. The bone histology of H. lindae would favour the hypothesis that a slow long-bone development could be a general character for stem tetrapods.
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| 6. |
- Mehlqvist, Kristina, et al.
(författare)
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A palynological study from Sweden reveals stable terrestrial environments during Late Silurian extreme marine conditions
- 2015
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - : The Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 105, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- A palynological study of the upper Silurian Öved–Ramsåsa Group in Skåne, Sweden yields a well preserved spore assemblage with low relative abundances of marine microfossils. In total, 26 spore taxa represented by 15 genera were identified. The spore assemblage is dominated by long-ranging cryptospore taxa, and the trilete spore Ambitisporites avitus-dilutus. However, key-species identified include Artemopyra radiata, Hispanaediscus lamontii, H. major, H. verrucatus, Scylaspora scripta and Synorisporites cf. libycus. Importantly, Scylaspora klintaensis was identified, allowing correlation with the Klinta 1 drillcore (Skåne). A Ludlow age is inferred for the exposed succession, which agrees well with previous conodont stratigraphy. The organic residue is dominated by phytodebris and spores, but with high relative abundances of acritarchs at two levels, possibly related to flooding surfaces. Based on the palynofacies analysis, a near-shore marine environment is proposed. The close proximity to land is inferred by the high proportions of spores, and the dispersed assemblage most likely represents the local flora growing on delta plains. The palynological signal also infers a stable terrestrial environment and vegetation, in contrast to unstable conditions in the marine environment characterised by ooid formation in an evaporitic environment. Comparisons with coeval spore assemblages from Gotland, Avalonia and Laurentia show relatively close similarities in taxonomic composition at the generic level.
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| 7. |
- Merritt, Jon W., et al.
(författare)
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Late Pleistocene sediments, landforms and events in Scotland : a review of the terrestrial stratigraphic record
- 2019
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 110:1-2, s. 39-91
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Forskningsöversikt (refereegranskat)abstract
- Lithostratigraphical studies coupled with the development of new dating methods has led to significant progress in understanding the Late Pleistocene terrestrial record in Scotland. Systematic analysis and re-evaluation of key localities have provided new insights into the complexity of the event stratigraphy in some regions and the timing of Late Pleistocene environmental changes, but few additional critical sites have been described in the past 25 years. The terrestrial stratigraphic record remains important for understanding the timing, sequence and patterns of glaciation and deglaciation during the last glacial/interglacial cycle. Former interpretations of ice-free areas in peripheral areas during the Last Glacial Maximum (LGM) are inconsistent with current stratigraphic and dating evidence. Significant challenges remain to determine events and patterns of glaciation during the Early and Middle Devensian, particularly in the context of offshore evidence and ice sheet modelling that indicate significant build-up of ice throughout much of the period. The terrestrial evidence broadly supports recent reconstructions of a highly dynamic and climate-sensitive British-Irish Ice Sheet (BIIS), which apparently reached its greatest thickness in Scotland between 30 and 27ka, before the global LGM. A thick (relative to topography) integrated ice sheet reaching the shelf edge with a simple ice-divide structure was replaced after the LGM by a much thinner one comprising multiple dispersion centres and a more complex flow structure.
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| 8. |
- Märss, T., et al.
(författare)
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Biodiversity of the Silurian osteostracans of the East Baltic
- 2014
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 105:2, s. 73-148
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Forskningsöversikt (refereegranskat)abstract
- The sculpture and histology of osteostracan head shields and trunk squamations from the Silurian of Estonia are described, illustrated and used for the identification of disarticulated microremains collected from outcrop sections and numerous drill cores in Estonia and Latvia over the last 40 years. The scattered osteostracan material contains thousands of specimens of scales and shield fragments. The sculpture and histology of species of the previously identified eight genera in the region (Tremataspis, Dartmuthia, Saaremaaspis, Oeselaspis, Aestiaspis, Thyestes, Procephalaspis, Witaaspis) are redescribed, together with Ateleaspis, found in Estonia for the first time. The sculpture on the cornua of several taxa is described for the first time. The new taxa Tremataspis perforata sp. nov., Dartmuthia procera sp. nov., Eldaaspis miklii gen. et sp. nov., Tahulaspis ordinata gen. et sp. nov., Tahulaspis praevia gen. et sp. nov., Meelaidaspis gennadii gen. et sp. nov. and Ohesaareaspis ponticulata gen. et sp. nov. are established, based upon sculpture and histological characteristics of the exoskeleton. The supraoral field with denticles of that field are described for the first time in Oeselaspis pustulata, as is the supraoral plate with buccal denticles in Meelaidaspis gennadii gen. et sp. nov. Thin sections of all taxa (except of Witaaspis) have been studied. This work sheds light on East Baltic osteostracan biodiversity from the Maasi Beds of the Jaagarahu Stage, Sheinwoodian, lower Wenlock up to the Ohesaare Stage, upper Pidoli, Silurian.
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| 9. |
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| 10. |
- Smith, David E., et al.
(författare)
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Quaternary sea level change in Scotland
- 2019
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Ingår i: Earth and environmental science transactions of the Royal Society of Edinburgh. - 1755-6910 .- 1755-6929. ; 110:1-2, s. 219-256
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarises developments in understanding sea level change during the Quaternary in Scotland since the publication of the Quaternary of Scotland Geological Conservation Review volume in 1993. We present a review of progress in methodology, particularly in the study of sediments in isolation basins and estuaries as well as in techniques in the field and laboratory, which have together disclosed greater detail in the record of relative sea level (RSL) change than was available in 1993. However, progress in determining the record of RSL change varies in different areas. Studies of sediments and stratigraphy offshore on the continental shelf have increased greatly, but the record of RSL change there remains patchy. Studies onshore have resulted in improvements in the knowledge of rock shorelines, including the processes by which they are formed, but much remains to be understood. Studies of Late Devensian and Holocene RSLs around present coasts have improved knowledge of both the extent and age range of the evidence. The record of RSL change on the W and NW coasts has disclosed a much longer dated RSL record than was available before 1993, possibly with evidence of Meltwater Pulse 1A, while studies in estuaries on the E and SW coasts have disclosed widespread and consistent fluctuations in Holocene RSLs. Evidence for the meltwater pulse associated with the Early Holocene discharge of Lakes Agassiz-Ojibway in N America has been found on both E and W coasts. The effects of the impact of storminess, in particular in cliff-top storm deposits, have been widely identified. Further information on the Holocene Storegga Slide tsunami has enabled a better understanding of the event, but evidence for other tsunami events on Scottish coasts remains uncertain. Methodological developments have led to new reconstructions of RSL change for the last 2000 years, utilising state-of-the-art GIA models and alongside coastal biostratigraphy to determine trends to compare with modern tide gauge and documentary evidence. Developments in GIA modelling have provided valuable information on patterns of land uplift during and following deglaciation. The studies undertaken raise a number of research questions which will require addressing in future work.
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