It has long been recognized that terrestrial floras underwent major and long-lasting changes duri... more It has long been recognized that terrestrial floras underwent major and long-lasting changes during the Permian and Triassic, some of which have been attributed to the end-Permian mass extinction. However, these changes are still poorly understood with regard to the late Permian and Early Triassic. In particular, the impact that ecological disturbances around the Permian-Triassic boundary had on the composition and palaeogeographical distribution of land plant communities needs to be scrutinized. We analyse this impact based on fossil floras from across the world, covering the Wuchiapingian to Ladinian time interval. The plant assemblages are assigned to biomes representing particular environmentally controlled community types. Variations in the distribution of biomes between stages indicate shifts in the environmental parameters affecting terrestrial floras, and provide insights into population turnover dynamics. A substantial shift towards increasing seasonality and a reduction of biome diversity occurs in the earliest Triassic and stabilised throughout the Middle Triassic. However, results also show that the stratigraphically and (palaeo-) geographically unequal distribution of sampled localities constitutes an important limitation for this kind of analysis.
In this paper, we provide an overview of the historically known Triassic floras from the Eastern ... more In this paper, we provide an overview of the historically known Triassic floras from the Eastern Southern Alps (e.g., Raibl and Recoaro), as well as the newer macro- and micro-plant assemblages that have been recorded during the 20th and 21st centuries. This includes some specimens stored in various European museums. The plant assemblages are presented here in chronostratigraphic order, starting with the Early Triassic, an interval of which only very few plant fragments are known from the area, whereas palynological data are available. In contrast to the Early Triassic, the Anisian floras (e.g., Kühwiesenkopf/Monte Prà della Vacca) are quite diverse, in both macrofloras – including in situ spores – and palynological assemblages. Similarly, the Ladinian of the Eastern Southern Alps is well known from the flora of Monte Agnello, which is outstanding in terms of both diversity and in total number of specimens, with additional information being derived from a large number of smaller macrofloral collections. The Carnian flora of the Eastern Southern Alps is also represented by a wide range of plant fossils, in contrast to the Norian/Rhaetian floras, which are represented only by a low number of macroremains and dispersed pollen and spores findings. A special subject of interest is the presence of amber in some of the Triassic sediments of the Southern Alps. Between the Wengen/La Valle and Heiligkreuz formations, the Dolomites represent the largest Triassic amber deposit known to date. In addition to macrofossil collections, the palynological data from many localities permits the reconstruction of environmental conditions during the various stages of the Triassic in the Southern Alps. They provide evidence for at least three shifts from xerophytic to hygrophytic palynoassemblages. Moreover, (chrono-)stratigraphic revision of the various localities enables a better understanding of the geographic and temporal distribution of the various taxa. Focusing on the overview picture of Triassic flora in the Eastern Southern Alps, only one necessary systematic aspect is highlighted herein. We transfer the material described as Sphenozamites wengensis to the genus Macropterygium as Macropterygium wengensis (Wachtler et Van Konijnenburg-van Cittert, 2000) Kustatscher et Van Konijnenburg-van Cittert comb. nov. The genus Macropterygium has been redefined for species with pinnate leaves with wedge-shaped segments that do not yield any cuticles and, thus, cannot be assigned to either the Cycadales or the Bennettitales, thereby distinguishing it from Apoldia and Sphenozamites.
The Laurinswand section in the Rosengarten/Catinaccio Massif (Dolomites, Southern Alps, Italy) co... more The Laurinswand section in the Rosengarten/Catinaccio Massif (Dolomites, Southern Alps, Italy) covers the Permian-Triassic boundary in a proximal marine setting. The section has been studied for palynology, ostracods and carbonate microfacies. Five microfacies types are defined for the carbonates of the Bellerophon Formation (Changhsingian) in this section. Ostracod assemblages from the upper Bellerophon Formation show a moderate to high diversity and mostly indicate normal marine conditions, with some samples from the upper Casera Razzo Member being dominated by eurytopic forms. The ostracod fauna follows transgressive-regressive trends with low diverse assemblages occurring in the regres-sive parts. These trends are also reflected in the microfacies and can be assigned to three sequences. Palynological assemblages are dominated by phytoclasts, which is typical for proximal marine environments. Sporomorphs are represented predominantly by bisaccate and asaccate pollen grains and are mostly minor components of the palynofacies. Other minor , but consistent components in the Bellerophon Formation are acritarchs, Reduviasporonites and unidentified possible algae or fungi. The latter are particularly abundant in samples with ostracod faunas indicating restricted conditions. The Werfen Formation (uppermost Permian to Lower Triassic) yielded quantitatively poor palynological assemblages, with one sample from the Tesero Member showing a notable increase in spores and spore tetrads. This is indicative of the so-called "spore spike", a well-known signal from this interval. One sample from the overlying Mazzin Member demonstrated a high relative abundance of Reduviasporonites, which may be related to mass occurrences of this taxon in the Tesero Member at Tesero and at other localities near the Permian-Triassic boundary. Such a mass occurrence normally pre-dates the spore spike, whereas at the Laurinswand, the former postdates the latter considerably.
Terrestrial floras underwent important changes during the Lopingian (late Permian), Early Triassi... more Terrestrial floras underwent important changes during the Lopingian (late Permian), Early Triassic, and Middle Triassic, i.e., before, during, and after the end-Permian mass extinction. An accurate account of these developments requires reliable correlation. Macrofossils of land plants can only provide a low-resolution biostratigraphy, while detailed zonation schemes based on palynomorphs are available for many regions. Their applicability is still limited due to several factors, such as (micro-)floral provincialism, a lack of suitable marker taxa commonly occurring at important boundaries, and in many cases a lack of independent age control. Nevertheless, these palynostratigraphic schemes are regularly used for dating and correlation of successions between different regions. To support such efforts, the biozonation schemes based on palynomorphs from the Lopingian up to and including the Middle Triassic from across the world are summarized and revised. Thus, a consistent correlation of palynozones with the currently recognized international stages is established.
The most severe mass extinction among animals took place in the latest Permian (ca. 252 million y... more The most severe mass extinction among animals took place in the latest Permian (ca. 252 million years ago). Due to scarce and impoverished fossil floras from the earliest Triassic, the common perception has been that land plants likewise suffered a mass extinction, but doubts remained. Here we use global occurrence data of both plant macro- and microfossils to analyse plant biodiversity development across the Permian–Triassic boundary. We show that the plant fossil record is strongly biased and that evidence for a mass extinction among plants in the latest Permian is not robust. The taxonomic diversities of gymnosperm macrofossils and of the pollen produced by this group are particularly incongruent. Our results indicate that gymnosperm macrofossils are considerably undersampled for the Early Triassic, which creates the impression of increased gymnosperm extinction in the latest Permian.
The Middle Ordovician (Darriwilian) Winneshiek Shale from Winneshiek County, Iowa, USA, hosts a K... more The Middle Ordovician (Darriwilian) Winneshiek Shale from Winneshiek County, Iowa, USA, hosts a Konservat‐Lagerstätte that has yielded a diverse fauna including soft‐bodied fossils. The shale is rich in organic content; in particular, algal material and fragmentary cuticular remains. Palynological acid treatment alongside modified, low‐manipulation processing enables the extraction of these ‘small carbonaceous fossils’ (SCFs) from the matrix, allowing a more detailed view of their morphology. Together these methods have yielded exceptionally well‐preserved crustacean‐type setae and a population of distinctive microfossils which we identify as the feeding appendages of a small‐bodied arthropod. We present two hypotheses for their identity: as either pancrustacean mandibles, or euchelicerate coxae. Overall, the detailed topological similarities and implied functional equivalence to the coxae of xiphosurid chelicerates, in particular, outweigh the resemblance to certain branchiopodan and hexapodan mandibles. In turn, however, the restricted size range and lack of associated limb or carapace fragments pose a taphonomic conundrum, suggesting an extreme biostratinomic bias. By comparison with previously described arthropodan SCFs from the Cambrian of Canada, the Winneshiek fossils extend the geographic, palaeoenvironmental and temporal range of this taphonomic window and provide a complementary tool for reconstructing the diversity and ecology of the Winneshiek biota.
Keywords: Konservat-Lagerstätten Sedimentology Ordovician Gondwana Morocco Fezouata The Lower Ord... more Keywords: Konservat-Lagerstätten Sedimentology Ordovician Gondwana Morocco Fezouata The Lower Ordovician Fezouata Konservat-Lagerstätte from southern Morocco has been one of the major palaeontological discoveries of the last decade. It provides a unique insight into one of the most critical periods in the evolution of marine life: the Cambrian–Ordovician transition. However, its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position, age and environmental setting. Based on extensive fieldwork, fossil evidence, and facies recognition, our study provides clarification on these three crucial issues. Exceptional preservation is limited to two intervals within the Fezouata Shale. Graptolites indicate a late Tremadocian age for the Fezouata Konservat-Lagerstätte as a whole, which is supported by biostratigraphical evidence provided by acritarchs. Sedimentological features and reconstructed patterns of relative sea-level changes indicate relatively shallow-water environmental conditions, under distal storm influence, in an offshore to lower shoreface siliciclastic ramp setting. The Fezouata Biota represents a unique and exceptional window into the palaeobiodiversity in open-marine conditions, thus contrasting with the other Ordovician Konservat-Lagerstätten presently known. In our analyses of this new set of data, we pave the way for accurate temporal, faunal and environmental comparisons with other Lower Palaeozoic Konservat-Lagerstätten, and unlock the full potential of the Fezouata Biota to better understand the processes and scenarios of early animal radiations.
The present study documents new palynological investigations of the Fezouata Shale from the Anti-... more The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstätte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstätte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.
Most early Palaeozoic acritarchs are thought to represent a part of the marine phytoplankton and ... more Most early Palaeozoic acritarchs are thought to represent a part of the marine phytoplankton and so constituted a significant element at the base of the marine trophic chain during the ‘Cambrian Explosion’ and the subsequent ‘Great Ordovician Biodiversification Event.’ Cambrian acritarch occurrences have been recorded in a great number of studies. In this paper, published data on Cambrian acritarchs are assembled in order to reconstruct taxonomic diversity trends that can be compared with the biodiversity of marine invertebrates. We compile a database and calculate various diversity indices at global and regional (i.e. Gondwana or Baltica) scales. The stratigraphic bins applied are at the level of the ten Cambrian stages, or of fourteen commonly used biozones in a somewhat higher resolved scheme. Our results show marked differences between palaeogeographical regions. They also indicate limitations of the data and a potential sampling bias, as the taxonomic diversity indices of species are significantly correlated with the number of studies per stratigraphic bin. The total and normalized diversities of genera are not affected in the same way. The normalized genus diversity curves show a slow but irregular rise over the course of the Cambrian. These also are the least biased. A radiation of species and to a lesser extent of genera in the ‘lower’ Cambrian Series 2 appears to mirror the ‘Cambrian Explosion’ of metazoans. This radiation, not evident on Gondwana, is followed by a prominent low in species diversity in the upper Series 3 and lower Furongian. Highest diversities are reached globally, and on both Baltica and Gondwana, in the uppermost Cambrian Stage 10, more precisely in the Peltura trilobite Zone, preceding a substantial phase of acritarch species extinction below and at the Cambrian/Ordovician boundary. Nearly all the genera present in Stage 10 survived into the Ordovician. The forms that emerged during the Cambrian therefore became the foundation for the more rapid radiation of acritarchs during the ‘Great Ordovician Biodiversification Event’.
The upper Tremadocian to lower Floian messaoudensis-trifidum acritarch assemblage was first descr... more The upper Tremadocian to lower Floian messaoudensis-trifidum acritarch assemblage was first described from the Skiddaw Group of England and subsequently from several localities on the Gondwanan margin that were positioned in high southern latitudes during the Early Ordovician. It is here reported for the first time from North Africa, from the Fezouata formations (Tremadocian to Floian) in the AZ-1 borehole, southeastern Morocco. The assemblage is comparable with that from the Skiddaw Group, with Cymatiogalea deunffii, C. messaoudensis, C. velifera, Caldariola glabra glabra, Stelliferidium trifidum and Veryhachium lairdii s.l. The Moroccan assemblage indicates a late Tremadocian age.
It has long been recognized that terrestrial floras underwent major and long-lasting changes duri... more It has long been recognized that terrestrial floras underwent major and long-lasting changes during the Permian and Triassic, some of which have been attributed to the end-Permian mass extinction. However, these changes are still poorly understood with regard to the late Permian and Early Triassic. In particular, the impact that ecological disturbances around the Permian-Triassic boundary had on the composition and palaeogeographical distribution of land plant communities needs to be scrutinized. We analyse this impact based on fossil floras from across the world, covering the Wuchiapingian to Ladinian time interval. The plant assemblages are assigned to biomes representing particular environmentally controlled community types. Variations in the distribution of biomes between stages indicate shifts in the environmental parameters affecting terrestrial floras, and provide insights into population turnover dynamics. A substantial shift towards increasing seasonality and a reduction of biome diversity occurs in the earliest Triassic and stabilised throughout the Middle Triassic. However, results also show that the stratigraphically and (palaeo-) geographically unequal distribution of sampled localities constitutes an important limitation for this kind of analysis.
In this paper, we provide an overview of the historically known Triassic floras from the Eastern ... more In this paper, we provide an overview of the historically known Triassic floras from the Eastern Southern Alps (e.g., Raibl and Recoaro), as well as the newer macro- and micro-plant assemblages that have been recorded during the 20th and 21st centuries. This includes some specimens stored in various European museums. The plant assemblages are presented here in chronostratigraphic order, starting with the Early Triassic, an interval of which only very few plant fragments are known from the area, whereas palynological data are available. In contrast to the Early Triassic, the Anisian floras (e.g., Kühwiesenkopf/Monte Prà della Vacca) are quite diverse, in both macrofloras – including in situ spores – and palynological assemblages. Similarly, the Ladinian of the Eastern Southern Alps is well known from the flora of Monte Agnello, which is outstanding in terms of both diversity and in total number of specimens, with additional information being derived from a large number of smaller macrofloral collections. The Carnian flora of the Eastern Southern Alps is also represented by a wide range of plant fossils, in contrast to the Norian/Rhaetian floras, which are represented only by a low number of macroremains and dispersed pollen and spores findings. A special subject of interest is the presence of amber in some of the Triassic sediments of the Southern Alps. Between the Wengen/La Valle and Heiligkreuz formations, the Dolomites represent the largest Triassic amber deposit known to date. In addition to macrofossil collections, the palynological data from many localities permits the reconstruction of environmental conditions during the various stages of the Triassic in the Southern Alps. They provide evidence for at least three shifts from xerophytic to hygrophytic palynoassemblages. Moreover, (chrono-)stratigraphic revision of the various localities enables a better understanding of the geographic and temporal distribution of the various taxa. Focusing on the overview picture of Triassic flora in the Eastern Southern Alps, only one necessary systematic aspect is highlighted herein. We transfer the material described as Sphenozamites wengensis to the genus Macropterygium as Macropterygium wengensis (Wachtler et Van Konijnenburg-van Cittert, 2000) Kustatscher et Van Konijnenburg-van Cittert comb. nov. The genus Macropterygium has been redefined for species with pinnate leaves with wedge-shaped segments that do not yield any cuticles and, thus, cannot be assigned to either the Cycadales or the Bennettitales, thereby distinguishing it from Apoldia and Sphenozamites.
The Laurinswand section in the Rosengarten/Catinaccio Massif (Dolomites, Southern Alps, Italy) co... more The Laurinswand section in the Rosengarten/Catinaccio Massif (Dolomites, Southern Alps, Italy) covers the Permian-Triassic boundary in a proximal marine setting. The section has been studied for palynology, ostracods and carbonate microfacies. Five microfacies types are defined for the carbonates of the Bellerophon Formation (Changhsingian) in this section. Ostracod assemblages from the upper Bellerophon Formation show a moderate to high diversity and mostly indicate normal marine conditions, with some samples from the upper Casera Razzo Member being dominated by eurytopic forms. The ostracod fauna follows transgressive-regressive trends with low diverse assemblages occurring in the regres-sive parts. These trends are also reflected in the microfacies and can be assigned to three sequences. Palynological assemblages are dominated by phytoclasts, which is typical for proximal marine environments. Sporomorphs are represented predominantly by bisaccate and asaccate pollen grains and are mostly minor components of the palynofacies. Other minor , but consistent components in the Bellerophon Formation are acritarchs, Reduviasporonites and unidentified possible algae or fungi. The latter are particularly abundant in samples with ostracod faunas indicating restricted conditions. The Werfen Formation (uppermost Permian to Lower Triassic) yielded quantitatively poor palynological assemblages, with one sample from the Tesero Member showing a notable increase in spores and spore tetrads. This is indicative of the so-called "spore spike", a well-known signal from this interval. One sample from the overlying Mazzin Member demonstrated a high relative abundance of Reduviasporonites, which may be related to mass occurrences of this taxon in the Tesero Member at Tesero and at other localities near the Permian-Triassic boundary. Such a mass occurrence normally pre-dates the spore spike, whereas at the Laurinswand, the former postdates the latter considerably.
Terrestrial floras underwent important changes during the Lopingian (late Permian), Early Triassi... more Terrestrial floras underwent important changes during the Lopingian (late Permian), Early Triassic, and Middle Triassic, i.e., before, during, and after the end-Permian mass extinction. An accurate account of these developments requires reliable correlation. Macrofossils of land plants can only provide a low-resolution biostratigraphy, while detailed zonation schemes based on palynomorphs are available for many regions. Their applicability is still limited due to several factors, such as (micro-)floral provincialism, a lack of suitable marker taxa commonly occurring at important boundaries, and in many cases a lack of independent age control. Nevertheless, these palynostratigraphic schemes are regularly used for dating and correlation of successions between different regions. To support such efforts, the biozonation schemes based on palynomorphs from the Lopingian up to and including the Middle Triassic from across the world are summarized and revised. Thus, a consistent correlation of palynozones with the currently recognized international stages is established.
The most severe mass extinction among animals took place in the latest Permian (ca. 252 million y... more The most severe mass extinction among animals took place in the latest Permian (ca. 252 million years ago). Due to scarce and impoverished fossil floras from the earliest Triassic, the common perception has been that land plants likewise suffered a mass extinction, but doubts remained. Here we use global occurrence data of both plant macro- and microfossils to analyse plant biodiversity development across the Permian–Triassic boundary. We show that the plant fossil record is strongly biased and that evidence for a mass extinction among plants in the latest Permian is not robust. The taxonomic diversities of gymnosperm macrofossils and of the pollen produced by this group are particularly incongruent. Our results indicate that gymnosperm macrofossils are considerably undersampled for the Early Triassic, which creates the impression of increased gymnosperm extinction in the latest Permian.
The Middle Ordovician (Darriwilian) Winneshiek Shale from Winneshiek County, Iowa, USA, hosts a K... more The Middle Ordovician (Darriwilian) Winneshiek Shale from Winneshiek County, Iowa, USA, hosts a Konservat‐Lagerstätte that has yielded a diverse fauna including soft‐bodied fossils. The shale is rich in organic content; in particular, algal material and fragmentary cuticular remains. Palynological acid treatment alongside modified, low‐manipulation processing enables the extraction of these ‘small carbonaceous fossils’ (SCFs) from the matrix, allowing a more detailed view of their morphology. Together these methods have yielded exceptionally well‐preserved crustacean‐type setae and a population of distinctive microfossils which we identify as the feeding appendages of a small‐bodied arthropod. We present two hypotheses for their identity: as either pancrustacean mandibles, or euchelicerate coxae. Overall, the detailed topological similarities and implied functional equivalence to the coxae of xiphosurid chelicerates, in particular, outweigh the resemblance to certain branchiopodan and hexapodan mandibles. In turn, however, the restricted size range and lack of associated limb or carapace fragments pose a taphonomic conundrum, suggesting an extreme biostratinomic bias. By comparison with previously described arthropodan SCFs from the Cambrian of Canada, the Winneshiek fossils extend the geographic, palaeoenvironmental and temporal range of this taphonomic window and provide a complementary tool for reconstructing the diversity and ecology of the Winneshiek biota.
Keywords: Konservat-Lagerstätten Sedimentology Ordovician Gondwana Morocco Fezouata The Lower Ord... more Keywords: Konservat-Lagerstätten Sedimentology Ordovician Gondwana Morocco Fezouata The Lower Ordovician Fezouata Konservat-Lagerstätte from southern Morocco has been one of the major palaeontological discoveries of the last decade. It provides a unique insight into one of the most critical periods in the evolution of marine life: the Cambrian–Ordovician transition. However, its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position, age and environmental setting. Based on extensive fieldwork, fossil evidence, and facies recognition, our study provides clarification on these three crucial issues. Exceptional preservation is limited to two intervals within the Fezouata Shale. Graptolites indicate a late Tremadocian age for the Fezouata Konservat-Lagerstätte as a whole, which is supported by biostratigraphical evidence provided by acritarchs. Sedimentological features and reconstructed patterns of relative sea-level changes indicate relatively shallow-water environmental conditions, under distal storm influence, in an offshore to lower shoreface siliciclastic ramp setting. The Fezouata Biota represents a unique and exceptional window into the palaeobiodiversity in open-marine conditions, thus contrasting with the other Ordovician Konservat-Lagerstätten presently known. In our analyses of this new set of data, we pave the way for accurate temporal, faunal and environmental comparisons with other Lower Palaeozoic Konservat-Lagerstätten, and unlock the full potential of the Fezouata Biota to better understand the processes and scenarios of early animal radiations.
The present study documents new palynological investigations of the Fezouata Shale from the Anti-... more The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstätte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstätte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.
Most early Palaeozoic acritarchs are thought to represent a part of the marine phytoplankton and ... more Most early Palaeozoic acritarchs are thought to represent a part of the marine phytoplankton and so constituted a significant element at the base of the marine trophic chain during the ‘Cambrian Explosion’ and the subsequent ‘Great Ordovician Biodiversification Event.’ Cambrian acritarch occurrences have been recorded in a great number of studies. In this paper, published data on Cambrian acritarchs are assembled in order to reconstruct taxonomic diversity trends that can be compared with the biodiversity of marine invertebrates. We compile a database and calculate various diversity indices at global and regional (i.e. Gondwana or Baltica) scales. The stratigraphic bins applied are at the level of the ten Cambrian stages, or of fourteen commonly used biozones in a somewhat higher resolved scheme. Our results show marked differences between palaeogeographical regions. They also indicate limitations of the data and a potential sampling bias, as the taxonomic diversity indices of species are significantly correlated with the number of studies per stratigraphic bin. The total and normalized diversities of genera are not affected in the same way. The normalized genus diversity curves show a slow but irregular rise over the course of the Cambrian. These also are the least biased. A radiation of species and to a lesser extent of genera in the ‘lower’ Cambrian Series 2 appears to mirror the ‘Cambrian Explosion’ of metazoans. This radiation, not evident on Gondwana, is followed by a prominent low in species diversity in the upper Series 3 and lower Furongian. Highest diversities are reached globally, and on both Baltica and Gondwana, in the uppermost Cambrian Stage 10, more precisely in the Peltura trilobite Zone, preceding a substantial phase of acritarch species extinction below and at the Cambrian/Ordovician boundary. Nearly all the genera present in Stage 10 survived into the Ordovician. The forms that emerged during the Cambrian therefore became the foundation for the more rapid radiation of acritarchs during the ‘Great Ordovician Biodiversification Event’.
The upper Tremadocian to lower Floian messaoudensis-trifidum acritarch assemblage was first descr... more The upper Tremadocian to lower Floian messaoudensis-trifidum acritarch assemblage was first described from the Skiddaw Group of England and subsequently from several localities on the Gondwanan margin that were positioned in high southern latitudes during the Early Ordovician. It is here reported for the first time from North Africa, from the Fezouata formations (Tremadocian to Floian) in the AZ-1 borehole, southeastern Morocco. The assemblage is comparable with that from the Skiddaw Group, with Cymatiogalea deunffii, C. messaoudensis, C. velifera, Caldariola glabra glabra, Stelliferidium trifidum and Veryhachium lairdii s.l. The Moroccan assemblage indicates a late Tremadocian age.
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Papers by Hendrik Nowak
In addition to macrofossil collections, the palynological data from many localities permits the reconstruction of environmental conditions during the various stages of the Triassic in the Southern Alps. They provide evidence for at least three shifts from xerophytic to hygrophytic palynoassemblages. Moreover, (chrono-)stratigraphic revision of the various localities enables a better understanding of the geographic and temporal distribution of the various taxa.
Focusing on the overview picture of Triassic flora in the Eastern Southern Alps, only one necessary systematic aspect is highlighted herein. We transfer the material described as Sphenozamites wengensis to the genus Macropterygium as Macropterygium wengensis (Wachtler et Van Konijnenburg-van Cittert, 2000) Kustatscher et Van Konijnenburg-van Cittert comb. nov. The genus Macropterygium has been redefined for species with pinnate leaves with wedge-shaped segments that do not yield any cuticles and, thus, cannot be assigned to either the Cycadales or the Bennettitales, thereby distinguishing it from Apoldia and Sphenozamites.
In addition to macrofossil collections, the palynological data from many localities permits the reconstruction of environmental conditions during the various stages of the Triassic in the Southern Alps. They provide evidence for at least three shifts from xerophytic to hygrophytic palynoassemblages. Moreover, (chrono-)stratigraphic revision of the various localities enables a better understanding of the geographic and temporal distribution of the various taxa.
Focusing on the overview picture of Triassic flora in the Eastern Southern Alps, only one necessary systematic aspect is highlighted herein. We transfer the material described as Sphenozamites wengensis to the genus Macropterygium as Macropterygium wengensis (Wachtler et Van Konijnenburg-van Cittert, 2000) Kustatscher et Van Konijnenburg-van Cittert comb. nov. The genus Macropterygium has been redefined for species with pinnate leaves with wedge-shaped segments that do not yield any cuticles and, thus, cannot be assigned to either the Cycadales or the Bennettitales, thereby distinguishing it from Apoldia and Sphenozamites.