Jared C. Richards, Karma Nanglu, Javier Ortega-Hernández
The Fezouata Shale Formation has dramatically impacted our understanding of Early Ordovician marine ecosystems before the great Ordovician biodiversification event (GOBE), thanks to the abundance and quality of exceptionally preserved animals within it. Systematic work has noted that the shelly fossil subassemblages of the Fezouata Shale biota are typical of open-marine deposits from the Lower Ordovician, but no studies have tested the quantitative validity of this statement. We extracted 491 occurrences of recalcitrant fossil genera from the Paleobiology Database to reconstruct 31 subassemblages to explore the paleoecology of the Fezouata Shale and other contemporary, high-latitude (66°S–90°S) deposits from the Lower Ordovician (485.4–470 Ma) and test the interpretation that the Fezouata Shale biota is typical for an Ordovician open-marine environment. Sørensen's dissimilarity metrics and Wilcoxon tests indicate that the subassemblages of the Tremadocian-aged lower Fezouata Shale are approximately 20% more heterogenous than the Floian-aged upper Fezouata Shale. Dissimilarity metrics and visualization suggest that while the lower Fezouata and upper Fezouata share faunal components, the two sections have distinct faunas. We find that the faunal composition of the lower Fezouata Shale is comparable with other Tremadocian-aged subassemblages from high latitudes, suggesting that it is typical for an Early Ordovician open-marine environment. We also find differences in faunal composition between Tremadocian- and Floian-aged deposits. Our results corroborate previous field-based and qualitative systematic studies that concluded that the shelly assemblages of the Fezouata Shale are comparable with those of other Lower Ordovician deposits from high latitudes. This establishes the first quantitative baseline for examining the composition and variability within the assemblages of the Fezouata Shale and will be key to future studies attempting to discern the degree to which it can inform our understanding of marine ecosystems just before the start of the GOBE.
{"title":"The Fezouata Shale Formation biota is typical for the high latitudes of the Early Ordovician—a quantitative approach","authors":"Jared C. Richards, Karma Nanglu, Javier Ortega-Hernández","doi":"10.1017/pab.2024.7","DOIUrl":"https://doi.org/10.1017/pab.2024.7","url":null,"abstract":"The Fezouata Shale Formation has dramatically impacted our understanding of Early Ordovician marine ecosystems before the great Ordovician biodiversification event (GOBE), thanks to the abundance and quality of exceptionally preserved animals within it. Systematic work has noted that the shelly fossil subassemblages of the Fezouata Shale biota are typical of open-marine deposits from the Lower Ordovician, but no studies have tested the quantitative validity of this statement. We extracted 491 occurrences of recalcitrant fossil genera from the Paleobiology Database to reconstruct 31 subassemblages to explore the paleoecology of the Fezouata Shale and other contemporary, high-latitude (66°S–90°S) deposits from the Lower Ordovician (485.4–470 Ma) and test the interpretation that the Fezouata Shale biota is typical for an Ordovician open-marine environment. Sørensen's dissimilarity metrics and Wilcoxon tests indicate that the subassemblages of the Tremadocian-aged lower Fezouata Shale are approximately 20% more heterogenous than the Floian-aged upper Fezouata Shale. Dissimilarity metrics and visualization suggest that while the lower Fezouata and upper Fezouata share faunal components, the two sections have distinct faunas. We find that the faunal composition of the lower Fezouata Shale is comparable with other Tremadocian-aged subassemblages from high latitudes, suggesting that it is typical for an Early Ordovician open-marine environment. We also find differences in faunal composition between Tremadocian- and Floian-aged deposits. Our results corroborate previous field-based and qualitative systematic studies that concluded that the shelly assemblages of the Fezouata Shale are comparable with those of other Lower Ordovician deposits from high latitudes. This establishes the first quantitative baseline for examining the composition and variability within the assemblages of the Fezouata Shale and will be key to future studies attempting to discern the degree to which it can inform our understanding of marine ecosystems just before the start of the GOBE.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Humans have dramatically transformed ecosystems over the previous millennia and are potentially causing a mass extinction event comparable to the others that shaped the history of life. However, only a fraction of these impacts has been directly recorded, limiting conservation actions. Conservation paleobiology leverages geohistorical records to offer a long-term perspective on biodiversity change in the face of anthropogenic stressors. Nevertheless, the field's on-the-ground contributions to conservation outcomes are still developing. Here, we present an overview of directions in which paleobiological research could progress to aid conservation in the coming decades using elasmobranchs (sharks, rays, and skates)—a highly threatened group with a rich fossil record—as a model. These research directions are guided by areas of overlap between an expert-led list of current elasmobranch conservation priorities and available fossil and historical records. Four research topics emerged for which paleobiological research could address open questions in elasmobranch science and conservation: (1) baselines, (2) ecological roles, (3) threats, and (4) conservation priorities. Increasingly rich datasets and novel analytical frameworks present exciting opportunities to apply the elasmobranch fossil record to conservation practice. A similar approach could be extended to other clades. Given the synthetic nature of these research topics, we encourage collaboration across timescales and with conservation practitioners to safeguard the future of our planet's rapidly disappearing species.
{"title":"Aligning paleobiological research with conservation priorities using elasmobranchs as a model","authors":"Erin M. Dillon, Catalina Pimiento","doi":"10.1017/pab.2024.11","DOIUrl":"https://doi.org/10.1017/pab.2024.11","url":null,"abstract":"Humans have dramatically transformed ecosystems over the previous millennia and are potentially causing a mass extinction event comparable to the others that shaped the history of life. However, only a fraction of these impacts has been directly recorded, limiting conservation actions. Conservation paleobiology leverages geohistorical records to offer a long-term perspective on biodiversity change in the face of anthropogenic stressors. Nevertheless, the field's on-the-ground contributions to conservation outcomes are still developing. Here, we present an overview of directions in which paleobiological research could progress to aid conservation in the coming decades using elasmobranchs (sharks, rays, and skates)—a highly threatened group with a rich fossil record—as a model. These research directions are guided by areas of overlap between an expert-led list of current elasmobranch conservation priorities and available fossil and historical records. Four research topics emerged for which paleobiological research could address open questions in elasmobranch science and conservation: (1) baselines, (2) ecological roles, (3) threats, and (4) conservation priorities. Increasingly rich datasets and novel analytical frameworks present exciting opportunities to apply the elasmobranch fossil record to conservation practice. A similar approach could be extended to other clades. Given the synthetic nature of these research topics, we encourage collaboration across timescales and with conservation practitioners to safeguard the future of our planet's rapidly disappearing species.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Romain Pintore, John R. Hutchinson, Peter J. Bishop, Henry P. Tsai, Alexandra Houssaye
Theropods are obligate bipedal dinosaurs that appeared 230 Ma and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown whether these body mass increases led to similar specializations between distinct lineages. Here we studied femoral shape variation across 41 species of theropods (n = 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated that the heaviest theropods evolved wider epiphyses and a more distally located fourth trochanter, as previously demonstrated in early archosaurs, along with an upturned femoral head and a mediodistal crest that extended proximally along the shaft. Phylogenetically informed analyses highlighted that these traits evolved convergently within six major theropod lineages, regardless of their maximum body mass. Conversely, the most gracile femora were distinct from the rest of the dataset, which we interpret as a femoral specialization to “miniaturization” evolving close to Avialae (bird lineage). Our results support a gradual evolution of known “avian” features, such as the fusion between lesser and greater trochanters and a reduction of the epiphyseal offset, independent from body mass variations, which may relate to a more “avian” type of locomotion (more knee than hip driven). The distinction between body mass variations and a more “avian” locomotion is represented by a decoupling in the mediodistal crest morphology, whose biomechanical nature should be studied to better understand the importance of its functional role in gigantism, miniaturization, and higher parasagittal abilities.
{"title":"The evolution of femoral morphology in giant non-avian theropod dinosaurs","authors":"Romain Pintore, John R. Hutchinson, Peter J. Bishop, Henry P. Tsai, Alexandra Houssaye","doi":"10.1017/pab.2024.6","DOIUrl":"https://doi.org/10.1017/pab.2024.6","url":null,"abstract":"Theropods are obligate bipedal dinosaurs that appeared 230 Ma and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown whether these body mass increases led to similar specializations between distinct lineages. Here we studied femoral shape variation across 41 species of theropods (<jats:italic>n</jats:italic> = 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated that the heaviest theropods evolved wider epiphyses and a more distally located fourth trochanter, as previously demonstrated in early archosaurs, along with an upturned femoral head and a mediodistal crest that extended proximally along the shaft. Phylogenetically informed analyses highlighted that these traits evolved convergently within six major theropod lineages, regardless of their maximum body mass. Conversely, the most gracile femora were distinct from the rest of the dataset, which we interpret as a femoral specialization to “miniaturization” evolving close to Avialae (bird lineage). Our results support a gradual evolution of known “avian” features, such as the fusion between lesser and greater trochanters and a reduction of the epiphyseal offset, independent from body mass variations, which may relate to a more “avian” type of locomotion (more knee than hip driven). The distinction between body mass variations and a more “avian” locomotion is represented by a decoupling in the mediodistal crest morphology, whose biomechanical nature should be studied to better understand the importance of its functional role in gigantism, miniaturization, and higher parasagittal abilities.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rachel C. Mohr, Thomas S. Tobin, Emily M. Tompkins
A traditional typological approach to taxonomy often does not adequately account for intraspecific variation and can result in taxonomic oversplitting. For many groups, including ammonoids of the Placenticeras genus, intraspecific variation documented in recent studies (e.g., ontogenetic changes, sexual dimorphism, polymorphism) challenges the historic proliferation of species names. Here, we used a population approach to taxonomy and quantitatively evaluated morphometric variation in a sample of Late Cretaceous (Santonian–Campanian) Placenticeras from Alabama and adjacent counties. We used linear mixed models (LMMs) to characterize how morphological variables scale with conch size across the sample, exploiting mixed longitudinal data to evaluate individual variation in growth and inform interpretations of multivariate analyses. Extended LMMs incorporating geological formation evaluated morphological changes through time. Principal component analysis and clustering analysis were then used to evaluate the number of distinct clusters that emerged in multivariate morphospace independent of previous taxon name assignments. Discontinuous scaling relationships and distinct clusters in multivariate space suggest sexual dimorphism characterized by differences in adult size and, secondarily, shape. Previous Stantonoceras and Placenticeras assignments broadly overlap in our morphospace, failing to justify this historic distinction (as sexual dimorphs or as genera or subgenera). Placenticeras conch morphology and ornament placement changed through time, suggesting a potential utility for coarse (stage-level) biostratigraphy. However, temporal changes were not associated with distinct clusters in morphospace, and our data fail to support the plethora of reported species names. As few as one or two (successive) species may be present in our sample (representing 130 years of collection effort). In addition to highlighting the need for a significant taxonomic revision of the Placenticeras genus, this study demonstrates the utility of LMMs for distinguishing between different sources of morphological variation, improving interpretations of morphospace under a population approach to taxonomy, and maximizing the amount of ontogenetic information that can be obtained nondestructively.
{"title":"Morphometric analysis of the Late Cretaceous Placenticeras of Alabama, USA: sexual dimorphism, allometry, and implications for taxonomy","authors":"Rachel C. Mohr, Thomas S. Tobin, Emily M. Tompkins","doi":"10.1017/pab.2024.3","DOIUrl":"https://doi.org/10.1017/pab.2024.3","url":null,"abstract":"A traditional typological approach to taxonomy often does not adequately account for intraspecific variation and can result in taxonomic oversplitting. For many groups, including ammonoids of the <jats:italic>Placenticeras</jats:italic> genus, intraspecific variation documented in recent studies (e.g., ontogenetic changes, sexual dimorphism, polymorphism) challenges the historic proliferation of species names. Here, we used a population approach to taxonomy and quantitatively evaluated morphometric variation in a sample of Late Cretaceous (Santonian–Campanian) <jats:italic>Placenticeras</jats:italic> from Alabama and adjacent counties. We used linear mixed models (LMMs) to characterize how morphological variables scale with conch size across the sample, exploiting mixed longitudinal data to evaluate individual variation in growth and inform interpretations of multivariate analyses. Extended LMMs incorporating geological formation evaluated morphological changes through time. Principal component analysis and clustering analysis were then used to evaluate the number of distinct clusters that emerged in multivariate morphospace independent of previous taxon name assignments. Discontinuous scaling relationships and distinct clusters in multivariate space suggest sexual dimorphism characterized by differences in adult size and, secondarily, shape. Previous <jats:italic>Stantonoceras</jats:italic> and <jats:italic>Placenticeras</jats:italic> assignments broadly overlap in our morphospace, failing to justify this historic distinction (as sexual dimorphs or as genera or subgenera). <jats:italic>Placenticeras</jats:italic> conch morphology and ornament placement changed through time, suggesting a potential utility for coarse (stage-level) biostratigraphy. However, temporal changes were not associated with distinct clusters in morphospace, and our data fail to support the plethora of reported species names. As few as one or two (successive) species may be present in our sample (representing 130 years of collection effort). In addition to highlighting the need for a significant taxonomic revision of the <jats:italic>Placenticeras</jats:italic> genus, this study demonstrates the utility of LMMs for distinguishing between different sources of morphological variation, improving interpretations of morphospace under a population approach to taxonomy, and maximizing the amount of ontogenetic information that can be obtained nondestructively.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is a pleasure to be invited to contribute to the celebration of the publication of “punctuated equilibria” (“punk eek”) 50 years ago—the canonical version I did with Steve Gould (Eldredge and Gould 1972) at the behest of Tom Schopf for his visionary project to inject more thought, more interpretation and theory, into the working lives of paleontologists.
{"title":"Reflections on punctuated equilibria","authors":"Niles Eldredge","doi":"10.1017/pab.2024.8","DOIUrl":"https://doi.org/10.1017/pab.2024.8","url":null,"abstract":"It is a pleasure to be invited to contribute to the celebration of the publication of “punctuated equilibria” (“punk eek”) 50 years ago—the canonical version I did with Steve Gould (Eldredge and Gould 1972) at the behest of Tom Schopf for his visionary project to inject more thought, more interpretation and theory, into the working lives of paleontologists.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Scaling fluctuation analyses of marine animal diversity and extinction and origination rates based on the Paleobiology Database occurrence data have opened new perspectives on macroevolution, supporting the hypothesis that the environment (climate proxies) and life (extinction and origination rates) are scaling over the “megaclimate” biogeological regime (from ≈1 Myr to at least 400 Myr). In the emerging picture, biodiversity is a scaling “crossover” phenomenon being dominated by the environment at short timescales and by life at long timescales with a crossover at ≈40 Myr. These findings provide the empirical basis for constructing the Fractional MacroEvolution Model (FMEM), a simple stochastic model combining destabilizing and stabilizing tendencies in macroevolutionary dynamics, driven by two scaling processes: temperature and turnover rates. Macroevolution models are typically deterministic (albeit sometimes perturbed by random noises) and are based on integer-ordered differential equations. In contrast, the FMEM is stochastic and based on fractional-ordered equations. Stochastic models are natural for systems with large numbers of degrees of freedom, and fractional equations naturally give rise to scaling processes. The basic FMEM drivers are fractional Brownian motions (temperature, T) and fractional Gaussian noises (turnover rates, E+) and the responses (solutions), are fractionally integrated fractional relaxation noises (diversity [D], extinction [E], origination [O], and E− = O − E). We discuss the impulse response (itself representing the model response to a bolide impact) and derive the model's full statistical properties. By numerically solving the model, we verified the mathematical analysis and compared both uniformly and irregularly sampled model outputs with paleobiology series.
{"title":"The Fractional MacroEvolution Model: a simple quantitative scaling macroevolution model","authors":"Shaun Lovejoy, Andrej Spiridonov","doi":"10.1017/pab.2023.38","DOIUrl":"https://doi.org/10.1017/pab.2023.38","url":null,"abstract":"Scaling fluctuation analyses of marine animal diversity and extinction and origination rates based on the Paleobiology Database occurrence data have opened new perspectives on macroevolution, supporting the hypothesis that the environment (climate proxies) and life (extinction and origination rates) are scaling over the “megaclimate” biogeological regime (from ≈1 Myr to at least 400 Myr). In the emerging picture, biodiversity is a scaling “crossover” phenomenon being dominated by the environment at short timescales and by life at long timescales with a crossover at ≈40 Myr. These findings provide the empirical basis for constructing the Fractional MacroEvolution Model (FMEM), a simple stochastic model combining destabilizing and stabilizing tendencies in macroevolutionary dynamics, driven by two scaling processes: temperature and turnover rates. Macroevolution models are typically deterministic (albeit sometimes perturbed by random noises) and are based on integer-ordered differential equations. In contrast, the FMEM is stochastic and based on fractional-ordered equations. Stochastic models are natural for systems with large numbers of degrees of freedom, and fractional equations naturally give rise to scaling processes. The basic FMEM drivers are fractional Brownian motions (temperature, <jats:italic>T</jats:italic>) and fractional Gaussian noises (turnover rates, <jats:italic>E</jats:italic><jats:sub>+</jats:sub>) and the responses (solutions), are fractionally integrated fractional relaxation noises (diversity [<jats:italic>D</jats:italic>], extinction [<jats:italic>E</jats:italic>], origination [<jats:italic>O</jats:italic>], and <jats:italic>E</jats:italic><jats:sub>−</jats:sub> = <jats:italic>O − E</jats:italic>). We discuss the impulse response (itself representing the model response to a bolide impact) and derive the model's full statistical properties. By numerically solving the model, we verified the mathematical analysis and compared both uniformly and irregularly sampled model outputs with paleobiology series.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ailie S. MacKenzie, Glenn A. Brock, Matthew R. McCurry
Apicobasal ridges are longitudinal ridges of enamel that are particularly common in several clades of aquatic-feeding predatory amniotes, including Plesiosauria, Ichthyosauria, Mosasauridae, Crocodylia, and Spinosauridae, as well as some early members of Cetacea. Although the repeated evolution of these dental ridges in unrelated clades suggests an adaptive benefit, their primary function in feeding is debated. Hypothesized functions range from increasing tooth strength to improving prey puncture or removal efficiency, but these have never been quantitatively tested. This study utilizes finite element analysis (FEA) to assess the impact of apicobasal ridges upon tooth crown strength in aquatic-feeding amniotes. Drawing on morphometric data from fossilized tooth crowns, a set of digital models was constructed to calculate the performance of smooth and ridged tooth variants under simulated bite force loadings. The similarities in overall stress distribution patterns across models of the same tooth shape, regardless of the presence or morphology of ridges, indicate that apicobasal ridges have little impact on stress reduction within the tooth crown. Ultimately, these findings suggest that apicobasal ridges have a minimal role in improving crown strength and form a framework for future research into the remaining hypotheses.
{"title":"The impact of apicobasal ridges on dental load-bearing capacity in aquatic-feeding predatory amniotes","authors":"Ailie S. MacKenzie, Glenn A. Brock, Matthew R. McCurry","doi":"10.1017/pab.2024.10","DOIUrl":"https://doi.org/10.1017/pab.2024.10","url":null,"abstract":"<p>Apicobasal ridges are longitudinal ridges of enamel that are particularly common in several clades of aquatic-feeding predatory amniotes, including Plesiosauria, Ichthyosauria, Mosasauridae, Crocodylia, and Spinosauridae, as well as some early members of Cetacea. Although the repeated evolution of these dental ridges in unrelated clades suggests an adaptive benefit, their primary function in feeding is debated. Hypothesized functions range from increasing tooth strength to improving prey puncture or removal efficiency, but these have never been quantitatively tested. This study utilizes finite element analysis (FEA) to assess the impact of apicobasal ridges upon tooth crown strength in aquatic-feeding amniotes. Drawing on morphometric data from fossilized tooth crowns, a set of digital models was constructed to calculate the performance of smooth and ridged tooth variants under simulated bite force loadings. The similarities in overall stress distribution patterns across models of the same tooth shape, regardless of the presence or morphology of ridges, indicate that apicobasal ridges have little impact on stress reduction within the tooth crown. Ultimately, these findings suggest that apicobasal ridges have a minimal role in improving crown strength and form a framework for future research into the remaining hypotheses.</p>","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140809261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electron backscatter diffraction (EBSD) has been widely used in recent studies of eggshells for its convenience in collecting in situ crystallographic information. China has a wide variety of dinosaur eggshells, although nearly none have been studied with this technique. Elongatoolithid eggs include many oogenera, although the microstructural differences of some were not highly appreciated, leading to several parataxonomic problems. In this paper, we surveyed seven elongatoolithid oogenera in China using EBSD in order to acquire more information about their microstructural variation. It is shown in this paper that in some elongatoolithid eggshells, scaly calcite grains that form the squamatic ultrastructure are not the only form of calcite in the continuous layer. Large columnar grains separated by high-angled grain boundaries and slender subgrains separated by radially arranged low-angled grain boundaries could exist in certain areas of the eggshells such as Macroolithus and Macroelongatoolithus. This paper discusses the criteria for identifying squamatic ultrastructure and proposes type I (rich in rugged high-angled grain boundaries) and type II (rich in both rugged high- and low-angled grain boundaries) squamatic ultrastructures. A pathological layer is found in Undulatoolithus pengi. An external zone is identified in the eggshell of Heishanoolithus changii, which does not support its position within the oofamily Elongatoolithidae. We argue that Paraelongatoolithus no longer belongs to Elongatoolithidae based on a combination of reticulated ornamentation, columnar continuous layer, and acicular mammillae. The high structural variation in elongatoolithid eggshells also implies that it may be inappropriate to relate all previous elongatoolithid eggshells to oviraptorosaurs and assume they are non-monophyletic.
{"title":"Electron backscatter diffraction (EBSD) study of elongatoolithid eggs from China with microstructural and parataxonomic implications","authors":"Xufeng Zhu, Qiang Wang, Xiaolin Wang","doi":"10.1017/pab.2024.9","DOIUrl":"https://doi.org/10.1017/pab.2024.9","url":null,"abstract":"\u0000 Electron backscatter diffraction (EBSD) has been widely used in recent studies of eggshells for its convenience in collecting in situ crystallographic information. China has a wide variety of dinosaur eggshells, although nearly none have been studied with this technique. Elongatoolithid eggs include many oogenera, although the microstructural differences of some were not highly appreciated, leading to several parataxonomic problems. In this paper, we surveyed seven elongatoolithid oogenera in China using EBSD in order to acquire more information about their microstructural variation. It is shown in this paper that in some elongatoolithid eggshells, scaly calcite grains that form the squamatic ultrastructure are not the only form of calcite in the continuous layer. Large columnar grains separated by high-angled grain boundaries and slender subgrains separated by radially arranged low-angled grain boundaries could exist in certain areas of the eggshells such as Macroolithus and Macroelongatoolithus. This paper discusses the criteria for identifying squamatic ultrastructure and proposes type I (rich in rugged high-angled grain boundaries) and type II (rich in both rugged high- and low-angled grain boundaries) squamatic ultrastructures. A pathological layer is found in Undulatoolithus pengi. An external zone is identified in the eggshell of Heishanoolithus changii, which does not support its position within the oofamily Elongatoolithidae. We argue that Paraelongatoolithus no longer belongs to Elongatoolithidae based on a combination of reticulated ornamentation, columnar continuous layer, and acicular mammillae. The high structural variation in elongatoolithid eggshells also implies that it may be inappropriate to relate all previous elongatoolithid eggshells to oviraptorosaurs and assume they are non-monophyletic.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140653692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tom Forêt, Paul Aubier, Stéphane Jouve, Jorge Cubo
Crocodylomorpha is a large and diverse clade with a long evolutionary history now restricted to modern crocodilians. Tethysuchia is a less-inclusive clade of semi-amphibious taxa that crossed two biological crises: the second Oceanic Anoxic Event (OAE 2) and the Cretaceous/Paleogene (K/Pg) crisis. Numerous studies have sought to find the driving factors explaining crocodylomorph evolution, producing contradictory conclusions. Studies of included groups may be useful. Here, we study factors driving tethysuchian evolution using phylogenetically informed statistical analyses. First, we tested the phylogenetic structure of tethysuchian extinction at the OAE 2 and K/Pg crises. We then used phylogenetic comparative methods to test the influence of intrinsic (body size, snout proportion) and extrinsic (temperature, paleolatitude) factors on the evolution of tethysuchian diversity at the OAE 2 and the K/Pg crises. Finally, we tested whether temperature influenced the evolution of body size. We conclude that (1) extinction was not random in regard to phylogeny for Tethysuchia at the OAE 2 and K/Pg crises; (2) while an important tethysuchian turnover follows OAE 2, the K/Pg crisis was followed by an explosion in diversity of tethysuchians, probably linked to the colonization of emptied ecological niches; (3) tethysuchians lived in warmer environments after the OAE 2 crisis, possibly because of both global warming and latitudinal distribution shifts; (4) there is a significant change of snout proportion after the OAE 2 and the K/Pg crises, likely caused by niche partitioning; and (5) there is a positive correlation between body size and temperature, possibly because of a longer growth season.
{"title":"Biotic and abiotic factors and the phylogenetic structure of extinction in the evolution of Tethysuchia","authors":"Tom Forêt, Paul Aubier, Stéphane Jouve, Jorge Cubo","doi":"10.1017/pab.2024.5","DOIUrl":"https://doi.org/10.1017/pab.2024.5","url":null,"abstract":"\u0000 Crocodylomorpha is a large and diverse clade with a long evolutionary history now restricted to modern crocodilians. Tethysuchia is a less-inclusive clade of semi-amphibious taxa that crossed two biological crises: the second Oceanic Anoxic Event (OAE 2) and the Cretaceous/Paleogene (K/Pg) crisis. Numerous studies have sought to find the driving factors explaining crocodylomorph evolution, producing contradictory conclusions. Studies of included groups may be useful. Here, we study factors driving tethysuchian evolution using phylogenetically informed statistical analyses. First, we tested the phylogenetic structure of tethysuchian extinction at the OAE 2 and K/Pg crises. We then used phylogenetic comparative methods to test the influence of intrinsic (body size, snout proportion) and extrinsic (temperature, paleolatitude) factors on the evolution of tethysuchian diversity at the OAE 2 and the K/Pg crises. Finally, we tested whether temperature influenced the evolution of body size. We conclude that (1) extinction was not random in regard to phylogeny for Tethysuchia at the OAE 2 and K/Pg crises; (2) while an important tethysuchian turnover follows OAE 2, the K/Pg crisis was followed by an explosion in diversity of tethysuchians, probably linked to the colonization of emptied ecological niches; (3) tethysuchians lived in warmer environments after the OAE 2 crisis, possibly because of both global warming and latitudinal distribution shifts; (4) there is a significant change of snout proportion after the OAE 2 and the K/Pg crises, likely caused by niche partitioning; and (5) there is a positive correlation between body size and temperature, possibly because of a longer growth season.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140671353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fitness of groups is often considered to be the average fitness among constituent members. This assumption has been useful for developing models of multilevel selection, but its uncritical adoption has held back our understanding of how multilevel selection actually works in nature. If group fitness is only equal to mean member fitness, then it is a simple task to erode the importance of group-level selection in all multilevel scenarios—species selection could then be reduced to organismal selection as easily as group selection can. Because selection from different levels can act on a single trait, body size, for example, there must be a way to translate one level of fitness to another. This allows the calculation of the contributions of selection at each level. If high-level fitness is not a simple function of member fitness, then how do they interlace? Here we reintroduce Leigh Van Valen’s argument for the inclusion of expansion as a component of fitness. We show that expansion is an integral part of fitness even if one does not subscribe to the energetic view of fitness from which Van Valen originally derived it. From a hierarchical perspective, expansion is the projection of demographic fitness from one level to the next level up; differential births and deaths at one level produce differential expansion one level above. Including expansion in our conceptual tool kit helps allay concerns about our ability to identify the level of selection using a number of methods as well as allowing for the various forms of multilevel selection to be seen as manifestations of the same basic process.
群体的适合度通常被认为是组成成员的平均适合度。这一假设有助于建立多级选择模型，但不加批判地采用这一假设却阻碍了我们对多级选择在自然界中实际作用的理解。如果群体适合度只等于平均成员适合度，那么在所有多级选择情景中，削弱群体级选择的重要性就是一件轻而易举的事--物种选择可以像群体选择一样被简化为生物体选择。由于不同层次的选择可以作用于单一性状，例如体型，因此必须有一种方法可以将一个层次的适应性转化为另一个层次的适应性。这样就可以计算出每个层次的选择贡献。如果高层次的适应性不是成员适应性的简单函数，那么它们之间又是如何交错的呢？在这里，我们重新引入利-范-瓦伦（Leigh Van Valen）的论点，将扩展作为适合度的一个组成部分。我们的研究表明，即使我们不赞同范-瓦伦最初提出的关于适应性的能量观点，扩张也是适应性不可分割的一部分。从等级的角度来看，扩张是人口适存度从一个等级向下一个等级的投射；一个等级的出生和死亡差异会产生上一个等级的扩张差异。将扩展纳入我们的概念工具包，有助于减轻我们对使用多种方法识别选择层次的能力的担忧，并允许将各种形式的多层次选择视为同一基本过程的表现形式。
{"title":"Levels of selection and macroevolution in organisms, colonies, and species","authors":"Carl Simpson, Andrea Halling, Sarah Leventhal","doi":"10.1017/pab.2024.12","DOIUrl":"https://doi.org/10.1017/pab.2024.12","url":null,"abstract":"The fitness of groups is often considered to be the average fitness among constituent members. This assumption has been useful for developing models of multilevel selection, but its uncritical adoption has held back our understanding of how multilevel selection actually works in nature. If group fitness is only equal to mean member fitness, then it is a simple task to erode the importance of group-level selection in all multilevel scenarios—species selection could then be reduced to organismal selection as easily as group selection can. Because selection from different levels can act on a single trait, body size, for example, there must be a way to translate one level of fitness to another. This allows the calculation of the contributions of selection at each level. If high-level fitness is not a simple function of member fitness, then how do they interlace? Here we reintroduce Leigh Van Valen’s argument for the inclusion of expansion as a component of fitness. We show that expansion is an integral part of fitness even if one does not subscribe to the energetic view of fitness from which Van Valen originally derived it. From a hierarchical perspective, expansion is the projection of demographic fitness from one level to the next level up; differential births and deaths at one level produce differential expansion one level above. Including expansion in our conceptual tool kit helps allay concerns about our ability to identify the level of selection using a number of methods as well as allowing for the various forms of multilevel selection to be seen as manifestations of the same basic process.","PeriodicalId":54646,"journal":{"name":"Paleobiology","volume":null,"pages":null},"PeriodicalIF":2.7,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140636610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：