Proceedings of the National Academy of Sciences, 2002
We show that the rates of diversification of the marine fauna and the levels of atmospheric CO 2 ... more We show that the rates of diversification of the marine fauna and the levels of atmospheric CO 2 have been closely correlated for the past 545 million years. These results, using two of the fundamental databases of the Earth's biota and the Earth's atmospheric composition, respectively, are highly statistically significant ( P < 0.001). The strength of the correlation suggests that one or more environmental variables controlling CO 2 levels have had a profound impact on evolution throughout the history of metazoan life. Comparing our work with highly significant correlations described by D. H. Rothman [Rothman, D. H. (2001) Proc. Natl. Acad. Sci. USA 98, 4305–4310] between total biological diversity and a measure of stable carbon isotope fractionation, we find that the rates of diversification rather than total diversification correlate with environmental variables, and that the rate of diversification follows the record of CO 2 projected by R. A. Berner and Z. Kothavala ...
Cnidarians represent an early diverging animal group and thus insight into their origin and diver... more Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnidarian jellyfish fossils from the Middle Cambrian (,505 million years old) Marjum Formation of Utah. These are the first described Cambrian jellyfish fossils to display exquisite preservation of soft part anatomy including detailed features of structures interpreted as trailing tentacles and subumbrellar and exumbrellar surfaces. If the interpretation of these preserved characters is correct, their presence is diagnostic of modern jellyfish taxa. These new discoveries may provide insight into the scope of cnidarian diversity shortly after the Cambrian radiation, and would reinforce the notion that important taxonomic components of the modern planktonic realm were in place by the Cambrian period.
The Cambrian radiation represents a key time period in the history of life. Here, we add to the m... more The Cambrian radiation represents a key time period in the history of life. Here, we add to the mounting evidence accumulating on the nature of deuterostomes from this time period through description of a new species of stalked deuterostome, Herpetogaster haiyanensis nov. sp., from the lower Cambrian (series 2, stage 3) Chengjiang biota of China. This represents the first occurrence of the genus in Gondwana, the first juvenile specimen, and the oldest specimens to date. Herpetogaster haiyanensis nov. sp. differs from H. collinsi Caron et al. (2010) in having a stolon that is separated into an outer and inner layer, the segmentation of the body and in the shape and number of branches of the tentacles. The new species reiterates earlier suggestions of deuterostome affinities of the genus―it appears closely related to Phlogites and then successively more distantly related to Cotyledon and Eldonia―and may have fed on hyolithids.
Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here... more Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here, a new deposit preserving soft-bodied fossils is reported from the Middle Ordovician (Dapingian-Darriwilian) upper Valongo Formation of northern Portugal. The deposit contains the first known occurrences of soft-bodied fossils from the Middle Ordovician (Dapingian-Darriwilian) of Portugal and is the first Ordovician example of soft-tissue preservation involving carbonaceous films from the Iberian Peninsula. It also represents the lone deposit of soft-bodied fossils from the Middle Ordovician of northern Gondwana. Thus temporally, it lies between the exceptional deposits of the Lower Ordovician of Fezouata (Morocco) and the Upper Ordovician of the Soom Shale (South Africa); it also serves as a biogeographic link between these and the various Ordovician soft-bodied deposits in Laurentia. The soft-bodied fossils come from the deep-water slates of the upper part of the Valongo Formation and include a discoidal fossil questionably referable to Patanacta, wiwaxiid sclerites, and a possible pseudoarctolepid arthropod.
The Cambrian radiation represents a key time period in the history of life. Here, we add to the m... more The Cambrian radiation represents a key time period in the history of life. Here, we add to the mounting evidence accumulating on the nature of deuterostomes from this time period through description of a new species of stalked deuterostome, Herpetogaster haiyanensis nov. sp., from the lower Cambrian (series 2, stage 3) Chengjiang biota of China. This represents the first occurrence of the genus in Gondwana, the first juvenile specimen, and the oldest specimens to date. Herpetogaster haiyanensis nov. sp. differs from H. collinsi Caron et al. (2010) in having a stolon that is separated into an outer and inner layer, the segmentation of the body and in the shape and number of branches of the tentacles. The new species reiterates earlier suggestions of deuterostome affinities of the genus-it appears closely related to Phlogites and then successively more distantly related to Cotyledon and Eldonia-and may have fed on hyolithids.
The Cambrian Marjum Formation of western Utah (USA) preserves a diverse soft-bodied fauna from th... more The Cambrian Marjum Formation of western Utah (USA) preserves a diverse soft-bodied fauna from the upper Drumian that is slightly younger than the well-known Burgess Shale. While the Marjum is dominated by arthropods, animals belonging to a variety of phyla have been found. Here, we document the second occurrence of the rare, enigmatic taxon Skeemella clavula, which was previously thought to be restricted to the Pierson Cove Formation of the Drum Mountains. The occurrence in the Marjum represents a new preservational setting, as well as a slightly younger deposit. The new specimens also expand the number of known specimens to three. In addition, they improve understanding of the morphology of this representative of the problematic phylum Vetulicolia.
Here we present a stand-alone, upper level undergraduate laboratory exercise that integrates orga... more Here we present a stand-alone, upper level undergraduate laboratory exercise that integrates organismal ecology and evolutionary concepts and minimizes the need for student memorization. This laboratory seeks to integrate both anatomical and conceptual content into paleontology lab pedagogy by demonstrating how taxon-specific anatomical information are the fundamental data by which scientists evaluate big picture questions related to the study of macroevolution and ecology. Real specimen photos are provided to familiarize students with a relatively limited suite of anatomical terms and taxonomic detail while allowing schools lacking large paleontology collections to participate in specimen-based inquiry. A matching exercise requires students to assign various trilobite morphologies to their interpreted ecological niches, thus reinforcing the students' new anatomical knowledge and helping students to distinguish between primary and secondary interpretation of scientific evidence. The use of trilobites as a macroevolutionary case study introduces students to questions still being actively investigated by scientists and provides an effective refutation of creationist arguments. By deemphasizing systematics and highlighting intriguing patterns from the recent published literature, this laboratory hopes to promote paleontology as a vibrant and relevant field, and avoid the misconception that paleontologists are simply stamp collectors, intent on naming and categorizing fossils. We hope that the broad implementation of this laboratory exercise will generate the data necessary to evaluate the validity of this approach and its ease of use in the classroom.
The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätt... more The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätte in northeastern Utah and southeastern Idaho. It is older than the more well-known Wheeler and Marjum Lagerstätten from western Utah, and the Burgess Shale from Canada. The Spence Shale shares several species in common with these younger deposits, yet it also contains a remarkable number of unique species. Because of its relatively broad geographic distribution, and the variety of different palaeoenvironments and taphonomy, the fossil composition and likelihood of recovering weakly skeletonized (or soft-bodied) taxa varies across localities. The Spence Shale is not only widely acknowledged for its collection of soft-bodied taxa, but also for its abundant trilobites and hyoliths. Recent discoveries from the Spence include problematic taxa and insights about the nature of palaeoenvironmental and taphonomic variation between different localities.
Museums at the Forefront of the History and Philosophy, 2018
Museum collections provide a tremendous wealth of data bearing on biogeography, the field that fo... more Museum collections provide a tremendous wealth of data bearing on biogeography, the field that focuses on the study of the distribution of organisms in space and time. Biogeography is a discipline that played a fundamental role in the development of ideas on evolution in the nineteenth century, and it still is a vibrant research area today. One way that biogeography has remained vibrant is through the burgeoning area of biodiversity science. There are many aspects of biodiversity science relevant to paleontology, running the gamut from conservation paleobiology to ecosystem observations , etc. Our especial focus here is on biodiversity science approaches involving the analysis of museum specimen records using mapping and analytical approaches, such as the geographic information system (GIS) and ecological niche modeling (ENM), to quantify how climate change has caused (and will continue to cause) species to move across the face of the globe through time. Initial efforts considered extant taxa, but now analyses of extinct taxa are becoming more commonplace. These analyses of fossil taxa offer extensive opportunities to gain increased insight into biogeography and also macroevolution. This contribution focuses specifically on approaches using fossil taxa and their associated museum specimen data. Such approaches have shown how invasive species have contributed to ancient biodiversity crises, how species niches largely remain stable over geological time scales, how it is predominately abiotic factors, as opposed to competition, that influence species distributions and determine species survival in the long term, and finally how extant species that have been present in marine ecosystems for millions of years are now in grave peril due to impending climate changes projected to occur in the near term. Each of these discoveries will be highlighted in order to help show the value that museum collections of fossils continue to have in the twenty-first century.
Basal metabolic rate (BMR) is posited to be a fundamental control on the structure and dynamics o... more Basal metabolic rate (BMR) is posited to be a fundamental control on the structure and dynamics of ecological networks, influencing organism resource use and rates of senescence. Differences in the maintenance energy requirements of individual species therefore potentially predict extinction likelihood. If validated, this would comprise an important link between organismic ecology and macroevolutionary dynamics. To test this hypothesis, the BMRs of organisms within fossil species were determined using body size and temperature data, and considered in the light of species' survival and extinction through time. Our analysis focused on the high-resolution record of Pliocene to recent molluscs (bivalves and gastropods) from the Western Atlantic. Species-specific BMRs were calculated by measuring the size range of specimens from museum collections, determining ocean temperature using the HadCM3 global climate model, and deriving values based on relevant equations. Intriguingly, a statistically significant difference in metabolic rate exists between those bivalve and gastropod taxa that went extinct and those that survived throughout the course of the Neogene. This indicates that there is a scaling up from organismic properties to species survival for these communities. Metabolic rate could therefore represent an important metric for predicting future extinction patterns, with changes in global climate potentially affecting the lifespan of individuals, ultimately leading to the extinction of the species they are contained within. We also find that, at the assemblage level, there are no significant differences in metabolic rates for different time intervals throughout the entire study period. This may suggest that Neogene mollusc communities have remained energetically stable, despite many extinctions.
The Red Queen hypothesis (RQH) is both familiar and murky, with a scope and range that has broade... more The Red Queen hypothesis (RQH) is both familiar and murky, with a scope and range that has broadened beyond its original focus. Although originally developed in the palaeontological arena, it now encompasses many evolutionary theories that champion biotic interactions as significant mechanisms for evolutionary change. As such it de-emphasizes the important role of abiotic drivers in evolution, even though such a role is frequently posited to be pivotal. Concomitant with this shift in focus, several studies challenged the validity of the RQH and downplayed its propriety. Herein, we examine in detail the assumptions that underpin the RQH in the hopes of furthering conceptual understanding and promoting appropriate application of the hypothesis. We identify issues and inconsistencies with the assumptions of the RQH, and propose a redefinition where the Red Queen's reign is restricted to certain types of biotic interactions and evolutionary patterns occurring at the population level.
We describe a new species of enigmatic stalked filter feeder, Siphusauctum lloydguntheri, from th... more We describe a new species of enigmatic stalked filter feeder, Siphusauctum lloydguntheri, from the middle Cambrian (Series 3, Stage 5) Antimony Canyon locality of the Spence Shale of northern Utah. The described specimen is the only one known from the Spence Shale, represents the first occurrence of Siphusauctum outside the Burgess Shale, and is only the second described species from the genus. Siphusauctum lloydguntheri n. sp. differs from S. gregarium O'Brien and Caron, 2012 in the shape of its calyx and the position of the digestive tract. The new species provides some additional information about the possible affinities of enigmatic stalked Cambrian filter feeders, as well as the taphonomic pathways that lead to preservation of Siphusauctum.
The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early... more The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician Discophyllum Hall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to as another clade, the eldonids, which includes the enigmatic Eldonia Walcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio-or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process.
A new synziphosurine, Anderella parva gen. et sp. nov., extends the known range of this group fro... more A new synziphosurine, Anderella parva gen. et sp. nov., extends the known range of this group from the Silurian to the Carboniferous and is the youngest known so far from the fossil record. Previously the youngest synziphosurine, Kasibelinurus, was from the Devonian of North America. Anderella parva has a semi-oval carapace with pointed genal regions, nine freely articulating opisthosomal segments and a long styliform tail spine. It is the third xiphosuran genus to be described from the Bear Gulch Limestone and its discovery highlights this deposit as containing an unusually diverse xiphosuran biota. It is also the only known locality where synziphosurines occur alongside the more derived xiphosurids. Xiphosurans reached their greatest diversity in the Carboniferous when the xiphosurids began to occupy brackish and freshwater habitats and became dominant over the synziphosurines. The discovery of the only known Carboniferous synziphosurine in marine sediments may indicate their inability to exploit these same environments.
Proceedings of the National Academy of Sciences, 2002
We show that the rates of diversification of the marine fauna and the levels of atmospheric CO 2 ... more We show that the rates of diversification of the marine fauna and the levels of atmospheric CO 2 have been closely correlated for the past 545 million years. These results, using two of the fundamental databases of the Earth's biota and the Earth's atmospheric composition, respectively, are highly statistically significant ( P < 0.001). The strength of the correlation suggests that one or more environmental variables controlling CO 2 levels have had a profound impact on evolution throughout the history of metazoan life. Comparing our work with highly significant correlations described by D. H. Rothman [Rothman, D. H. (2001) Proc. Natl. Acad. Sci. USA 98, 4305–4310] between total biological diversity and a measure of stable carbon isotope fractionation, we find that the rates of diversification rather than total diversification correlate with environmental variables, and that the rate of diversification follows the record of CO 2 projected by R. A. Berner and Z. Kothavala ...
Cnidarians represent an early diverging animal group and thus insight into their origin and diver... more Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnidarian jellyfish fossils from the Middle Cambrian (,505 million years old) Marjum Formation of Utah. These are the first described Cambrian jellyfish fossils to display exquisite preservation of soft part anatomy including detailed features of structures interpreted as trailing tentacles and subumbrellar and exumbrellar surfaces. If the interpretation of these preserved characters is correct, their presence is diagnostic of modern jellyfish taxa. These new discoveries may provide insight into the scope of cnidarian diversity shortly after the Cambrian radiation, and would reinforce the notion that important taxonomic components of the modern planktonic realm were in place by the Cambrian period.
The Cambrian radiation represents a key time period in the history of life. Here, we add to the m... more The Cambrian radiation represents a key time period in the history of life. Here, we add to the mounting evidence accumulating on the nature of deuterostomes from this time period through description of a new species of stalked deuterostome, Herpetogaster haiyanensis nov. sp., from the lower Cambrian (series 2, stage 3) Chengjiang biota of China. This represents the first occurrence of the genus in Gondwana, the first juvenile specimen, and the oldest specimens to date. Herpetogaster haiyanensis nov. sp. differs from H. collinsi Caron et al. (2010) in having a stolon that is separated into an outer and inner layer, the segmentation of the body and in the shape and number of branches of the tentacles. The new species reiterates earlier suggestions of deuterostome affinities of the genus―it appears closely related to Phlogites and then successively more distantly related to Cotyledon and Eldonia―and may have fed on hyolithids.
Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here... more Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here, a new deposit preserving soft-bodied fossils is reported from the Middle Ordovician (Dapingian-Darriwilian) upper Valongo Formation of northern Portugal. The deposit contains the first known occurrences of soft-bodied fossils from the Middle Ordovician (Dapingian-Darriwilian) of Portugal and is the first Ordovician example of soft-tissue preservation involving carbonaceous films from the Iberian Peninsula. It also represents the lone deposit of soft-bodied fossils from the Middle Ordovician of northern Gondwana. Thus temporally, it lies between the exceptional deposits of the Lower Ordovician of Fezouata (Morocco) and the Upper Ordovician of the Soom Shale (South Africa); it also serves as a biogeographic link between these and the various Ordovician soft-bodied deposits in Laurentia. The soft-bodied fossils come from the deep-water slates of the upper part of the Valongo Formation and include a discoidal fossil questionably referable to Patanacta, wiwaxiid sclerites, and a possible pseudoarctolepid arthropod.
The Cambrian radiation represents a key time period in the history of life. Here, we add to the m... more The Cambrian radiation represents a key time period in the history of life. Here, we add to the mounting evidence accumulating on the nature of deuterostomes from this time period through description of a new species of stalked deuterostome, Herpetogaster haiyanensis nov. sp., from the lower Cambrian (series 2, stage 3) Chengjiang biota of China. This represents the first occurrence of the genus in Gondwana, the first juvenile specimen, and the oldest specimens to date. Herpetogaster haiyanensis nov. sp. differs from H. collinsi Caron et al. (2010) in having a stolon that is separated into an outer and inner layer, the segmentation of the body and in the shape and number of branches of the tentacles. The new species reiterates earlier suggestions of deuterostome affinities of the genus-it appears closely related to Phlogites and then successively more distantly related to Cotyledon and Eldonia-and may have fed on hyolithids.
The Cambrian Marjum Formation of western Utah (USA) preserves a diverse soft-bodied fauna from th... more The Cambrian Marjum Formation of western Utah (USA) preserves a diverse soft-bodied fauna from the upper Drumian that is slightly younger than the well-known Burgess Shale. While the Marjum is dominated by arthropods, animals belonging to a variety of phyla have been found. Here, we document the second occurrence of the rare, enigmatic taxon Skeemella clavula, which was previously thought to be restricted to the Pierson Cove Formation of the Drum Mountains. The occurrence in the Marjum represents a new preservational setting, as well as a slightly younger deposit. The new specimens also expand the number of known specimens to three. In addition, they improve understanding of the morphology of this representative of the problematic phylum Vetulicolia.
Here we present a stand-alone, upper level undergraduate laboratory exercise that integrates orga... more Here we present a stand-alone, upper level undergraduate laboratory exercise that integrates organismal ecology and evolutionary concepts and minimizes the need for student memorization. This laboratory seeks to integrate both anatomical and conceptual content into paleontology lab pedagogy by demonstrating how taxon-specific anatomical information are the fundamental data by which scientists evaluate big picture questions related to the study of macroevolution and ecology. Real specimen photos are provided to familiarize students with a relatively limited suite of anatomical terms and taxonomic detail while allowing schools lacking large paleontology collections to participate in specimen-based inquiry. A matching exercise requires students to assign various trilobite morphologies to their interpreted ecological niches, thus reinforcing the students' new anatomical knowledge and helping students to distinguish between primary and secondary interpretation of scientific evidence. The use of trilobites as a macroevolutionary case study introduces students to questions still being actively investigated by scientists and provides an effective refutation of creationist arguments. By deemphasizing systematics and highlighting intriguing patterns from the recent published literature, this laboratory hopes to promote paleontology as a vibrant and relevant field, and avoid the misconception that paleontologists are simply stamp collectors, intent on naming and categorizing fossils. We hope that the broad implementation of this laboratory exercise will generate the data necessary to evaluate the validity of this approach and its ease of use in the classroom.
The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätt... more The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätte in northeastern Utah and southeastern Idaho. It is older than the more well-known Wheeler and Marjum Lagerstätten from western Utah, and the Burgess Shale from Canada. The Spence Shale shares several species in common with these younger deposits, yet it also contains a remarkable number of unique species. Because of its relatively broad geographic distribution, and the variety of different palaeoenvironments and taphonomy, the fossil composition and likelihood of recovering weakly skeletonized (or soft-bodied) taxa varies across localities. The Spence Shale is not only widely acknowledged for its collection of soft-bodied taxa, but also for its abundant trilobites and hyoliths. Recent discoveries from the Spence include problematic taxa and insights about the nature of palaeoenvironmental and taphonomic variation between different localities.
Museums at the Forefront of the History and Philosophy, 2018
Museum collections provide a tremendous wealth of data bearing on biogeography, the field that fo... more Museum collections provide a tremendous wealth of data bearing on biogeography, the field that focuses on the study of the distribution of organisms in space and time. Biogeography is a discipline that played a fundamental role in the development of ideas on evolution in the nineteenth century, and it still is a vibrant research area today. One way that biogeography has remained vibrant is through the burgeoning area of biodiversity science. There are many aspects of biodiversity science relevant to paleontology, running the gamut from conservation paleobiology to ecosystem observations , etc. Our especial focus here is on biodiversity science approaches involving the analysis of museum specimen records using mapping and analytical approaches, such as the geographic information system (GIS) and ecological niche modeling (ENM), to quantify how climate change has caused (and will continue to cause) species to move across the face of the globe through time. Initial efforts considered extant taxa, but now analyses of extinct taxa are becoming more commonplace. These analyses of fossil taxa offer extensive opportunities to gain increased insight into biogeography and also macroevolution. This contribution focuses specifically on approaches using fossil taxa and their associated museum specimen data. Such approaches have shown how invasive species have contributed to ancient biodiversity crises, how species niches largely remain stable over geological time scales, how it is predominately abiotic factors, as opposed to competition, that influence species distributions and determine species survival in the long term, and finally how extant species that have been present in marine ecosystems for millions of years are now in grave peril due to impending climate changes projected to occur in the near term. Each of these discoveries will be highlighted in order to help show the value that museum collections of fossils continue to have in the twenty-first century.
Basal metabolic rate (BMR) is posited to be a fundamental control on the structure and dynamics o... more Basal metabolic rate (BMR) is posited to be a fundamental control on the structure and dynamics of ecological networks, influencing organism resource use and rates of senescence. Differences in the maintenance energy requirements of individual species therefore potentially predict extinction likelihood. If validated, this would comprise an important link between organismic ecology and macroevolutionary dynamics. To test this hypothesis, the BMRs of organisms within fossil species were determined using body size and temperature data, and considered in the light of species' survival and extinction through time. Our analysis focused on the high-resolution record of Pliocene to recent molluscs (bivalves and gastropods) from the Western Atlantic. Species-specific BMRs were calculated by measuring the size range of specimens from museum collections, determining ocean temperature using the HadCM3 global climate model, and deriving values based on relevant equations. Intriguingly, a statistically significant difference in metabolic rate exists between those bivalve and gastropod taxa that went extinct and those that survived throughout the course of the Neogene. This indicates that there is a scaling up from organismic properties to species survival for these communities. Metabolic rate could therefore represent an important metric for predicting future extinction patterns, with changes in global climate potentially affecting the lifespan of individuals, ultimately leading to the extinction of the species they are contained within. We also find that, at the assemblage level, there are no significant differences in metabolic rates for different time intervals throughout the entire study period. This may suggest that Neogene mollusc communities have remained energetically stable, despite many extinctions.
The Red Queen hypothesis (RQH) is both familiar and murky, with a scope and range that has broade... more The Red Queen hypothesis (RQH) is both familiar and murky, with a scope and range that has broadened beyond its original focus. Although originally developed in the palaeontological arena, it now encompasses many evolutionary theories that champion biotic interactions as significant mechanisms for evolutionary change. As such it de-emphasizes the important role of abiotic drivers in evolution, even though such a role is frequently posited to be pivotal. Concomitant with this shift in focus, several studies challenged the validity of the RQH and downplayed its propriety. Herein, we examine in detail the assumptions that underpin the RQH in the hopes of furthering conceptual understanding and promoting appropriate application of the hypothesis. We identify issues and inconsistencies with the assumptions of the RQH, and propose a redefinition where the Red Queen's reign is restricted to certain types of biotic interactions and evolutionary patterns occurring at the population level.
We describe a new species of enigmatic stalked filter feeder, Siphusauctum lloydguntheri, from th... more We describe a new species of enigmatic stalked filter feeder, Siphusauctum lloydguntheri, from the middle Cambrian (Series 3, Stage 5) Antimony Canyon locality of the Spence Shale of northern Utah. The described specimen is the only one known from the Spence Shale, represents the first occurrence of Siphusauctum outside the Burgess Shale, and is only the second described species from the genus. Siphusauctum lloydguntheri n. sp. differs from S. gregarium O'Brien and Caron, 2012 in the shape of its calyx and the position of the digestive tract. The new species provides some additional information about the possible affinities of enigmatic stalked Cambrian filter feeders, as well as the taphonomic pathways that lead to preservation of Siphusauctum.
The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early... more The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician Discophyllum Hall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to as another clade, the eldonids, which includes the enigmatic Eldonia Walcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio-or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process.
A new synziphosurine, Anderella parva gen. et sp. nov., extends the known range of this group fro... more A new synziphosurine, Anderella parva gen. et sp. nov., extends the known range of this group from the Silurian to the Carboniferous and is the youngest known so far from the fossil record. Previously the youngest synziphosurine, Kasibelinurus, was from the Devonian of North America. Anderella parva has a semi-oval carapace with pointed genal regions, nine freely articulating opisthosomal segments and a long styliform tail spine. It is the third xiphosuran genus to be described from the Bear Gulch Limestone and its discovery highlights this deposit as containing an unusually diverse xiphosuran biota. It is also the only known locality where synziphosurines occur alongside the more derived xiphosurids. Xiphosurans reached their greatest diversity in the Carboniferous when the xiphosurids began to occupy brackish and freshwater habitats and became dominant over the synziphosurines. The discovery of the only known Carboniferous synziphosurine in marine sediments may indicate their inability to exploit these same environments.
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Papers by B. Lieberman