S. López‐Torres, Ornella C. Bertrand, Madlen M. Lang, Ł. Fostowicz‐Frelik, M. Silcox, Jin Meng
Anagalids are an extinct group of primitive mammals from the Asian Palaeogene thought to be possible basal members of Glires. Anagalid material is rare, with only a handful of crania known. Here we describe the first virtual endocast of an anagalid, based on the holotype of Anagale gobiensis (AMNH 26079; late Eocene, China), which allows for comparison with published endocasts from fossil members of modern euarchontogliran lineages (i.e. primates, rodents, lagomorphs). The endocast displays traits often observed in fossorial mammals, such as relatively small petrosal lobules and a low neocortical ratio, which would be consistent with previous inferences about use of subterranean food sources based on heavy dental wear. In fact, Anagale gobiensis has the lowest neocortical ratio yet recorded for a euarchontogliran. This species was olfaction‐driven, based on the relatively large olfactory bulbs and laterally expansive palaeocortex. The endocast supports previous inferences that relatively large olfactory bulbs, partial midbrain exposure and low encephalization quotient are ancestral for Euarchontoglires, although the likely fossorial adaptations of Anagale gobiensis may also partly explain these traits. While Anagale gobiensis is a primitive mammal in many aspects, some of its derived endocranial traits point towards a new, different trajectory of brain evolution within Euarchontoglires.
{"title":"Cranial endocast of Anagale gobiensis (Anagalidae) and its implications for early brain evolution in Euarchontoglires","authors":"S. López‐Torres, Ornella C. Bertrand, Madlen M. Lang, Ł. Fostowicz‐Frelik, M. Silcox, Jin Meng","doi":"10.1111/pala.12650","DOIUrl":"https://doi.org/10.1111/pala.12650","url":null,"abstract":"Anagalids are an extinct group of primitive mammals from the Asian Palaeogene thought to be possible basal members of Glires. Anagalid material is rare, with only a handful of crania known. Here we describe the first virtual endocast of an anagalid, based on the holotype of Anagale gobiensis (AMNH 26079; late Eocene, China), which allows for comparison with published endocasts from fossil members of modern euarchontogliran lineages (i.e. primates, rodents, lagomorphs). The endocast displays traits often observed in fossorial mammals, such as relatively small petrosal lobules and a low neocortical ratio, which would be consistent with previous inferences about use of subterranean food sources based on heavy dental wear. In fact, Anagale gobiensis has the lowest neocortical ratio yet recorded for a euarchontogliran. This species was olfaction‐driven, based on the relatively large olfactory bulbs and laterally expansive palaeocortex. The endocast supports previous inferences that relatively large olfactory bulbs, partial midbrain exposure and low encephalization quotient are ancestral for Euarchontoglires, although the likely fossorial adaptations of Anagale gobiensis may also partly explain these traits. While Anagale gobiensis is a primitive mammal in many aspects, some of its derived endocranial traits point towards a new, different trajectory of brain evolution within Euarchontoglires.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42119866","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}
I present a simulation model on vital statistics, absolute abundance (N, total number of individuals that ever lived) and preservation rate (p, minimum number of fossils known divided by N) of Tyrannosaurus rex. It is based on a published age‐structured population model that assumes a reptile or bird‐like reproduction for T. rex to estimate its age‐specific survival rates. My model applies input variables and equations from a recently published model on N and p. This model yielded 2.5 billion T. rex individuals (N) and one fossil per 80 million individuals (p). The average N values calculated by my model were at minimum 27.6% and p values at maximum 361.5% that of a previous model and uncertainties in all output variables were always larger in my model. The equation on output variable ‘population density’ introduced the largest uncertainty to N and p. The output variable ‘generation time’ differed the most between models, but for N and p, the huge size of the input area modelled and geological longevity minimized this difference. Unlike my model, the generation time as well as life expectancies, gross reproduction rates, and reproductive values of individuals calculated from the previous model all strongly contradicted our current understanding of the biology of T. rex and of other theropods. Their values also disagreed with those of large extant reptiles, birds and mammals. All of these shortcomings of the previous model favour the assessment of individual and population characteristics of T. rex and of other extinct species using my model.
{"title":"Vital statistics, absolute abundance and preservation rate of Tyrannosaurus rex","authors":"E. Griebeler","doi":"10.1111/pala.12648","DOIUrl":"https://doi.org/10.1111/pala.12648","url":null,"abstract":"I present a simulation model on vital statistics, absolute abundance (N, total number of individuals that ever lived) and preservation rate (p, minimum number of fossils known divided by N) of Tyrannosaurus rex. It is based on a published age‐structured population model that assumes a reptile or bird‐like reproduction for T. rex to estimate its age‐specific survival rates. My model applies input variables and equations from a recently published model on N and p. This model yielded 2.5 billion T. rex individuals (N) and one fossil per 80 million individuals (p). The average N values calculated by my model were at minimum 27.6% and p values at maximum 361.5% that of a previous model and uncertainties in all output variables were always larger in my model. The equation on output variable ‘population density’ introduced the largest uncertainty to N and p. The output variable ‘generation time’ differed the most between models, but for N and p, the huge size of the input area modelled and geological longevity minimized this difference. Unlike my model, the generation time as well as life expectancies, gross reproduction rates, and reproductive values of individuals calculated from the previous model all strongly contradicted our current understanding of the biology of T. rex and of other theropods. Their values also disagreed with those of large extant reptiles, birds and mammals. All of these shortcomings of the previous model favour the assessment of individual and population characteristics of T. rex and of other extinct species using my model.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48265776","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}
‘Strophodontoid’ brachiopods represented the majority of strophomenide brachiopods in the Silurian and Devonian periods. They are characterized by denticles developed along the hinge line. The evolution of denticles correlated with the disappearance of dental plates and teeth and were already present when the clade originated in the Late Ordovician. Specimens of Eostropheodonta parvicostellata from the Kuanyinchiao Bed (early–middle Hirnantian, uppermost Ordovician) in the Hetaoba Section, Meitan, Guizhou Province, South China, display clear fossil population variation, during a process of loss of dental plates and the development of denticles. Three phenotypes of E. parvicostellata are recognized in a single fossil bed, likely heralding a speciation process. Non‐metric multidimensional scaling (NMDS) based on five key characters of genera of the Family Leptostrophiidae shows a much wider morphospace for Silurian genera than for those in the Devonian. Phylogenetic analysis of the Family Leptostrophiidae supports the NMDS analysis and mostly tracks their geological history. The fossil population differentiation in E. parvicostellata discovered between the two phases of the Late Ordovician mass extinction event (LOME) linked to a major glaciation, suggests a Hirnantian origination of the ‘strophodontoid’ morphology, and links microevolutionary change to a macroevolutionary event.
{"title":"Did the Late Ordovician mass extinction event trigger the earliest evolution of ‘strophodontoid’ brachiopods?","authors":"Bing Huang, Diann-Yih Chen, D. Harper, Jiayu Rong","doi":"10.1111/pala.12642","DOIUrl":"https://doi.org/10.1111/pala.12642","url":null,"abstract":"‘Strophodontoid’ brachiopods represented the majority of strophomenide brachiopods in the Silurian and Devonian periods. They are characterized by denticles developed along the hinge line. The evolution of denticles correlated with the disappearance of dental plates and teeth and were already present when the clade originated in the Late Ordovician. Specimens of Eostropheodonta parvicostellata from the Kuanyinchiao Bed (early–middle Hirnantian, uppermost Ordovician) in the Hetaoba Section, Meitan, Guizhou Province, South China, display clear fossil population variation, during a process of loss of dental plates and the development of denticles. Three phenotypes of E. parvicostellata are recognized in a single fossil bed, likely heralding a speciation process. Non‐metric multidimensional scaling (NMDS) based on five key characters of genera of the Family Leptostrophiidae shows a much wider morphospace for Silurian genera than for those in the Devonian. Phylogenetic analysis of the Family Leptostrophiidae supports the NMDS analysis and mostly tracks their geological history. The fossil population differentiation in E. parvicostellata discovered between the two phases of the Late Ordovician mass extinction event (LOME) linked to a major glaciation, suggests a Hirnantian origination of the ‘strophodontoid’ morphology, and links microevolutionary change to a macroevolutionary event.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48189022","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}
E. Capel, C. Monnet, C. Cleal, J. Xue, T. Servais, B. Cascales‐Miñana
The Silurian–Devonian plant radiation was a critical development in the evolution of early terrestrial ecosystems. Characterizing the diversity dynamics of this radiation has been a focus of numerous studies. However, little is known about the impact of geological bias on our perception of this biodiversification. Here, we use a new, comprehensive compilation of plant occurrences from North America, together with a Macrostrat lithological dataset, to elucidate the relationships between the palaeobotanical and geological records of early land plants. Results show that observed raw diversity patterns at both species and genus rank are significantly correlated with fluctuations of sedimentary rock volume, especially of non‐marine fossiliferous deposits. The lack of terrestrial sedimentary deposits before the Emsian (Early Devonian) makes it difficult to obtain an accurate depiction of the pre‐Emsian plant diversification in North America. However, complementary analyses reveal that sampling‐standardized diversity patterns partially correct the raw trajectories, especially at the genus‐level if enough preserved non‐marine sediments are available for sampling. Our findings highlight that geological incompleteness remains a fundamental bias for describing early plant diversification. This indicates that, even when sampling is extensive, observed diversity patterns potentially reflect the heterogeneity of the rock record, which blurs our understanding of the early history of land vegetation.
{"title":"The effect of geological biases on our perception of early land plant radiation","authors":"E. Capel, C. Monnet, C. Cleal, J. Xue, T. Servais, B. Cascales‐Miñana","doi":"10.1111/pala.12644","DOIUrl":"https://doi.org/10.1111/pala.12644","url":null,"abstract":"The Silurian–Devonian plant radiation was a critical development in the evolution of early terrestrial ecosystems. Characterizing the diversity dynamics of this radiation has been a focus of numerous studies. However, little is known about the impact of geological bias on our perception of this biodiversification. Here, we use a new, comprehensive compilation of plant occurrences from North America, together with a Macrostrat lithological dataset, to elucidate the relationships between the palaeobotanical and geological records of early land plants. Results show that observed raw diversity patterns at both species and genus rank are significantly correlated with fluctuations of sedimentary rock volume, especially of non‐marine fossiliferous deposits. The lack of terrestrial sedimentary deposits before the Emsian (Early Devonian) makes it difficult to obtain an accurate depiction of the pre‐Emsian plant diversification in North America. However, complementary analyses reveal that sampling‐standardized diversity patterns partially correct the raw trajectories, especially at the genus‐level if enough preserved non‐marine sediments are available for sampling. Our findings highlight that geological incompleteness remains a fundamental bias for describing early plant diversification. This indicates that, even when sampling is extensive, observed diversity patterns potentially reflect the heterogeneity of the rock record, which blurs our understanding of the early history of land vegetation.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49068713","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}
Trilobites are an abundant group of Palaeozoic marine euarthropods that appear abruptly in the fossil record c. 521 million years ago. Quantifying the development of morphological variation (or ‘disparity’) through time in fossil groups like trilobites is critical in understanding evolutionary radiations such as the Cambrian ‘explosion’. Here, I use geometric morphometrics to quantify ‘cumulative disparity’ in functionally‐important structures within the trilobite cephalon across their initial radiation during Cambrian Series 2. Overall cephalic disparity increased rapidly and attained a maximum within several million years. This pattern is dominated by the cephalic outline (in particular the genal spines), reflecting rapid, convergent expansion to the extremes of morphospace in a few early families. In contrast, removing the outline and focusing on structures such as the glabella and eye ridges (associated with feeding and vision, respectively) showed a more gradual increase in disparity, closer in line with taxonomic diversity and supporting the hypothesis of a relatively accurate trilobite fossil record. These contrasting patterns suggest that disparity in different structures was constrained in different ways, with extrinsic (ecological) factors probably having the major impact on overall disparity. It also implies that patterns of disparity in isolated substructures cannot necessarily be taken individually as representative of overall morphologies.
{"title":"Contrasting patterns of disparity suggest differing constraints on the evolution of trilobite cephalic structures during the Cambrian ‘explosion’","authors":"J. D. Holmes","doi":"10.1111/pala.12647","DOIUrl":"https://doi.org/10.1111/pala.12647","url":null,"abstract":"Trilobites are an abundant group of Palaeozoic marine euarthropods that appear abruptly in the fossil record c. 521 million years ago. Quantifying the development of morphological variation (or ‘disparity’) through time in fossil groups like trilobites is critical in understanding evolutionary radiations such as the Cambrian ‘explosion’. Here, I use geometric morphometrics to quantify ‘cumulative disparity’ in functionally‐important structures within the trilobite cephalon across their initial radiation during Cambrian Series 2. Overall cephalic disparity increased rapidly and attained a maximum within several million years. This pattern is dominated by the cephalic outline (in particular the genal spines), reflecting rapid, convergent expansion to the extremes of morphospace in a few early families. In contrast, removing the outline and focusing on structures such as the glabella and eye ridges (associated with feeding and vision, respectively) showed a more gradual increase in disparity, closer in line with taxonomic diversity and supporting the hypothesis of a relatively accurate trilobite fossil record. These contrasting patterns suggest that disparity in different structures was constrained in different ways, with extrinsic (ecological) factors probably having the major impact on overall disparity. It also implies that patterns of disparity in isolated substructures cannot necessarily be taken individually as representative of overall morphologies.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49643578","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}
Susana Gutarra, Thomas L. Stubbs, B. Moon, Beatrice H. Heighton, M. Benton
The aftermath of the end‐Permian mass extinction provided ecological opportunities for many groups of reptiles, marking the beginning of reptile dominance of the Mesozoic oceans. Clades such as ichthyosaurs, thalattosuchians, sauropterygians, mosasaurs and turtles evolved a remarkable diversity of ecological niches and became important components of aquatic ecosystems. Locomotion is a key aspect of ecology, crucial for many biological functions such as foraging and migration. However, the evolution of locomotory adaptations across all Mesozoic marine reptiles remains poorly understood. Here we present multivariate and disparity analyses based on body proportions, body size and post‐cranial proxies for locomotion in 125 species of Mesozoic marine reptiles. Our analysis highlights key anatomical transformations in the evolution of swimming modes, characterizing two divergent evolutionary paths in the transition from drag‐based to lift‐based propulsion in both the axial and appendicular spectrum. Analyses against geological time do not show evidence for an explosive radiation after the end‐Permian extinction, pointing instead to a gradual increase in locomotory disparity during the whole Mesozoic, which reached the highest levels in the Cretaceous. Our analysis also provides insight into the evolution of locomotion in particular clades. Some notable findings are the high aquatic specialization in the earliest ichthyosauromorphs and the morphospace overlap between mosasauroids and ichthyosauromorphs.
{"title":"The locomotor ecomorphology of Mesozoic marine reptiles","authors":"Susana Gutarra, Thomas L. Stubbs, B. Moon, Beatrice H. Heighton, M. Benton","doi":"10.1111/pala.12645","DOIUrl":"https://doi.org/10.1111/pala.12645","url":null,"abstract":"The aftermath of the end‐Permian mass extinction provided ecological opportunities for many groups of reptiles, marking the beginning of reptile dominance of the Mesozoic oceans. Clades such as ichthyosaurs, thalattosuchians, sauropterygians, mosasaurs and turtles evolved a remarkable diversity of ecological niches and became important components of aquatic ecosystems. Locomotion is a key aspect of ecology, crucial for many biological functions such as foraging and migration. However, the evolution of locomotory adaptations across all Mesozoic marine reptiles remains poorly understood. Here we present multivariate and disparity analyses based on body proportions, body size and post‐cranial proxies for locomotion in 125 species of Mesozoic marine reptiles. Our analysis highlights key anatomical transformations in the evolution of swimming modes, characterizing two divergent evolutionary paths in the transition from drag‐based to lift‐based propulsion in both the axial and appendicular spectrum. Analyses against geological time do not show evidence for an explosive radiation after the end‐Permian extinction, pointing instead to a gradual increase in locomotory disparity during the whole Mesozoic, which reached the highest levels in the Cretaceous. Our analysis also provides insight into the evolution of locomotion in particular clades. Some notable findings are the high aquatic specialization in the earliest ichthyosauromorphs and the morphospace overlap between mosasauroids and ichthyosauromorphs.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48201374","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}
Tomoyuki Mikami, Takafumi Ikeda, Yusuke Muramiya, Tatsuya Hirasawa, W. Iwasaki
Tullimonstrum gregarium, also known as the Tully monster, is a well‐known phylogenetic enigma, fossils of which have been found only in the Mazon Creek Lagerstätte. The affinities of Tullimonstrum have been debated since its discovery in 1966, because its peculiar morphology with stalked eyes and a proboscis cannot easily be compared with any known animal morphotypes. Recently, the possibility that Tullimonstrum was a vertebrate has attracted much attention, and it has been postulated that Tullimonstrum might fill a gap in the fossil record of early vertebrates, providing important insights into vertebrate evolutionary history. With the hope of resolving this debate, we collected 3D surface data from 153 specimens of Tullimonstrum using a high‐resolution laser 3D scanner and conducted x‐ray micro‐computed tomographic (μCT) analysis of stylets in the proboscis. Our investigation of the resulting comprehensive 3D morphological dataset revealed that structures previously regarded as myomeres, tri‐lobed brain, tectal cartilages and fin rays are not comparable with those of vertebrates. These results raise further doubts about its vertebrate affinities, and suggest that Tullimonstrum may have been either a non‐vertebrate chordate or a protostome.
Tullimonstrum clusterium，也被称为Tully怪物，是一个众所周知的系统发育谜，其化石仅在Mazon Creek Lagerstätte发现。自1966年被发现以来，Tullimonstrum的亲缘关系一直存在争议，因为它有柄眼睛和长鼻的特殊形态很难与任何已知的动物形态进行比较。最近，Tullimonstrum是脊椎动物的可能性引起了人们的关注，人们认为Tullimontrum可能填补了早期脊椎动物化石记录的空白，为脊椎动物进化史提供了重要的见解。为了解决这一争论，我们使用高分辨率激光3D扫描仪从153个Tullimonstrum标本中收集了3D表面数据，并对长鼻中的探针进行了x射线显微计算机断层扫描（μCT）分析。我们对由此产生的综合3D形态学数据集的调查显示，以前被认为是子宫肌瘤、三叶脑、顶盖软骨和鳍射线的结构与脊椎动物的结构不可比较。这些结果进一步引起了人们对其脊椎动物亲缘关系的怀疑，并表明Tullimonstrum可能是一种非脊椎动物脊索动物或原口动物。
{"title":"Three‐dimensional anatomy of the Tully monster casts doubt on its presumed vertebrate affinities","authors":"Tomoyuki Mikami, Takafumi Ikeda, Yusuke Muramiya, Tatsuya Hirasawa, W. Iwasaki","doi":"10.1111/pala.12646","DOIUrl":"https://doi.org/10.1111/pala.12646","url":null,"abstract":"Tullimonstrum gregarium, also known as the Tully monster, is a well‐known phylogenetic enigma, fossils of which have been found only in the Mazon Creek Lagerstätte. The affinities of Tullimonstrum have been debated since its discovery in 1966, because its peculiar morphology with stalked eyes and a proboscis cannot easily be compared with any known animal morphotypes. Recently, the possibility that Tullimonstrum was a vertebrate has attracted much attention, and it has been postulated that Tullimonstrum might fill a gap in the fossil record of early vertebrates, providing important insights into vertebrate evolutionary history. With the hope of resolving this debate, we collected 3D surface data from 153 specimens of Tullimonstrum using a high‐resolution laser 3D scanner and conducted x‐ray micro‐computed tomographic (μCT) analysis of stylets in the proboscis. Our investigation of the resulting comprehensive 3D morphological dataset revealed that structures previously regarded as myomeres, tri‐lobed brain, tectal cartilages and fin rays are not comparable with those of vertebrates. These results raise further doubts about its vertebrate affinities, and suggest that Tullimonstrum may have been either a non‐vertebrate chordate or a protostome.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42540941","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}
Jane C. Reeves, R. Wogelius, J. N. Keating, Robert S. Sansom
The fossil record of non‐biomineralizing, soft‐bodied taxa is our only direct evidence of the early history of vertebrates. A robust reconstruction of the affinities of these taxa is critical to unlocking vertebrate origins and understanding the evolution of skeletal tissues, but these taxa invariably have unstable and poorly supported phylogenetic positions. At the cusp between mineralized bony vertebrates and entirely soft‐bodied vertebrates is the enigmatic Lasanius, a purported anaspid from the Silurian of Scotland. Interpretations of its affinity and significance are conflicted, principally because of its poorly understood anatomy due to taphonomic distortion and loss of soft‐tissues. Here we use an array of modern techniques to reassess the anatomy of Lasanius via a comprehensive study of 229 complete and partial specimens. A new reconstruction clarifies the identity and position of preserved features, including paired sensory organs, a notochord, and digestive tract, supporting the vertebrate affinities of this genus. SEM‐EDS trace element mapping suggests a bone‐like composition of mineralized parts, but finds no evidence for mineralized dermal armour. Phylogenetic analysis recovers Lasanius as an early stem‐cyclostome, and subsequent analysis supports the rejection of alternative placements (such as stem‐gnathostome). We highlight that while distinguishing between the early cyclostome and gnathostome condition is problematic, increasing confidence in the anatomy of key taxa, such as Lasanius, is vital for increased stability throughout the early vertebrate tree.
{"title":"Lasanius, an exceptionally preserved Silurian jawless fish from Scotland","authors":"Jane C. Reeves, R. Wogelius, J. N. Keating, Robert S. Sansom","doi":"10.1111/pala.12643","DOIUrl":"https://doi.org/10.1111/pala.12643","url":null,"abstract":"The fossil record of non‐biomineralizing, soft‐bodied taxa is our only direct evidence of the early history of vertebrates. A robust reconstruction of the affinities of these taxa is critical to unlocking vertebrate origins and understanding the evolution of skeletal tissues, but these taxa invariably have unstable and poorly supported phylogenetic positions. At the cusp between mineralized bony vertebrates and entirely soft‐bodied vertebrates is the enigmatic Lasanius, a purported anaspid from the Silurian of Scotland. Interpretations of its affinity and significance are conflicted, principally because of its poorly understood anatomy due to taphonomic distortion and loss of soft‐tissues. Here we use an array of modern techniques to reassess the anatomy of Lasanius via a comprehensive study of 229 complete and partial specimens. A new reconstruction clarifies the identity and position of preserved features, including paired sensory organs, a notochord, and digestive tract, supporting the vertebrate affinities of this genus. SEM‐EDS trace element mapping suggests a bone‐like composition of mineralized parts, but finds no evidence for mineralized dermal armour. Phylogenetic analysis recovers Lasanius as an early stem‐cyclostome, and subsequent analysis supports the rejection of alternative placements (such as stem‐gnathostome). We highlight that while distinguishing between the early cyclostome and gnathostome condition is problematic, increasing confidence in the anatomy of key taxa, such as Lasanius, is vital for increased stability throughout the early vertebrate tree.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44375663","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}
Geometric morphometric approaches become increasingly applied in the fields of biology and palaeontology. Taxonomy is a good example, where a long‐standing intention of scientists is to eliminate subjectivity as much as possible. In the case of biostratigraphically important conodont elements, the application of such methods is not widespread. Only a handful of studies attempted to deal with the morphological variance of conodont elements from this aspect. The detailed description of five lower Norian (Upper Triassic) taxa (Ancyrogondolella quadrata, A. rigoi, A. triangularis, A. uniformis and Metapolygnathus mazzai) is presented here based on landmarks and Fourier analysis of the P1 element and keel outlines. Both methods led to similar outcomes regarding taxonomic differentiation and exposing shape variability. Consensus shapes were generated to objectively reveal the typical contour shape of each taxon, which allowed their comparison with each other, and with the members of their respective sample population including the holotypes. The results demonstrated that the holotype of a taxon is generally not an average representative, but rather a peripheral form with well separable morphological characteristics. Ancyrogondolella quadrata and A. rigoi turned out to represent a morphological continuum with ample transitional forms between these two end‐members that may cause bias in their biostratigraphic applicability, however their combined shape variance seems to be too large for uniting them into a single species. Given the results that may be too subtle to realize based solely on qualitative observations, future taxonomic studies and type material designation could greatly benefit from the application of similar methodologies.
{"title":"Potential of closed contour analysis for species differentiation and holotype designation: a case study on lower Norian (Upper Triassic) conodonts","authors":"A. Virág, Viktor Karádi","doi":"10.1111/pala.12649","DOIUrl":"https://doi.org/10.1111/pala.12649","url":null,"abstract":"Geometric morphometric approaches become increasingly applied in the fields of biology and palaeontology. Taxonomy is a good example, where a long‐standing intention of scientists is to eliminate subjectivity as much as possible. In the case of biostratigraphically important conodont elements, the application of such methods is not widespread. Only a handful of studies attempted to deal with the morphological variance of conodont elements from this aspect. The detailed description of five lower Norian (Upper Triassic) taxa (Ancyrogondolella quadrata, A. rigoi, A. triangularis, A. uniformis and Metapolygnathus mazzai) is presented here based on landmarks and Fourier analysis of the P1 element and keel outlines. Both methods led to similar outcomes regarding taxonomic differentiation and exposing shape variability. Consensus shapes were generated to objectively reveal the typical contour shape of each taxon, which allowed their comparison with each other, and with the members of their respective sample population including the holotypes. The results demonstrated that the holotype of a taxon is generally not an average representative, but rather a peripheral form with well separable morphological characteristics. Ancyrogondolella quadrata and A. rigoi turned out to represent a morphological continuum with ample transitional forms between these two end‐members that may cause bias in their biostratigraphic applicability, however their combined shape variance seems to be too large for uniting them into a single species. Given the results that may be too subtle to realize based solely on qualitative observations, future taxonomic studies and type material designation could greatly benefit from the application of similar methodologies.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48191062","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 evolutionary context in which shark bioluminescence originated is poorly understood, despite it being critical to uncovering influential factors in the evolutionary history and diversity of living chondrichthyans as well as the mechanisms of deep‐water colonization by vertebrates. This study provides the first joint reconstruction of the habitats, lifestyles, and occurrence of bioluminescence in the evolution of squalomorph sharks using ancestral state estimation analysis to resolve the timing of deep‐sea colonization, the evolutionary origin of bioluminescence and the ancestral ecologies of this group. The results suggest that most squalomorphs originated in neritic environments from where they colonized deep waters on several independent occasions during the Late Jurassic and Early Cretaceous, predating most of the previous estimates of the timing of this event. The colonization of the deep sea took place via the benthic zone, in contrast to the view that an intermediate mesopelagic stage occurred during this ecological transition. Finally, the analyses accounting for uncertainty of the presence of bioluminescence strongly support that this trait evolved only once among sharks in a bathydemersal ancestor. This study reveals that shark bioluminescence evolved in a complex scenario that combines elements of several previous proposals, and enriches our perspective on the sequence of events that characterized the vertebrate conquest of the deep sea.
{"title":"Illuminating the evolution of bioluminescence in sharks","authors":"H. Ferrón","doi":"10.1111/pala.12641","DOIUrl":"https://doi.org/10.1111/pala.12641","url":null,"abstract":"The evolutionary context in which shark bioluminescence originated is poorly understood, despite it being critical to uncovering influential factors in the evolutionary history and diversity of living chondrichthyans as well as the mechanisms of deep‐water colonization by vertebrates. This study provides the first joint reconstruction of the habitats, lifestyles, and occurrence of bioluminescence in the evolution of squalomorph sharks using ancestral state estimation analysis to resolve the timing of deep‐sea colonization, the evolutionary origin of bioluminescence and the ancestral ecologies of this group. The results suggest that most squalomorphs originated in neritic environments from where they colonized deep waters on several independent occasions during the Late Jurassic and Early Cretaceous, predating most of the previous estimates of the timing of this event. The colonization of the deep sea took place via the benthic zone, in contrast to the view that an intermediate mesopelagic stage occurred during this ecological transition. Finally, the analyses accounting for uncertainty of the presence of bioluminescence strongly support that this trait evolved only once among sharks in a bathydemersal ancestor. This study reveals that shark bioluminescence evolved in a complex scenario that combines elements of several previous proposals, and enriches our perspective on the sequence of events that characterized the vertebrate conquest of the deep sea.","PeriodicalId":56272,"journal":{"name":"Palaeontology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45729079","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：