Fellipe P. Muniz, M. C. Bissaro-Júnior, E. Guilherme, Jonas Pereira de Souza Filho, F. R. Negri, A. S. Hsiou
Abstract: The Niterói and Talismã sites comprise two of the most important fossiliferous deposits of the Neogene in Brazil. After 30 years of research, these sites have revealed rich assemblages of vertebrates and provided a glimpse of the Amazonian fauna and environment during the Miocene. Despite this, detailed studies that attempt to explain the genesis of these bonebeds are still scarce and hamper more robust paleoenvironmental and paleoecological reconstructions. Here we provide the first in-depth taphonomic analysis for both locations. Sedimentological and taphonomic evidence suggest that the depositional environments of Niterói and Talismã were similarly represented by shallow and calm waters in lacustrine/swampy contexts. We propose that the accumulation of bones and teeth is the result of attritional (day-to-day) mortality of organisms of the local community in a low sedimentation environment. The thanatocoenosis was exposed to biostratinomic processes for longer periods of time, which explains the high disarticulation, disassociation, fragmentation and loss of skeletal elements. The almost absence of weathering indicates that the aquatic environment slowed down the organic degradation of bioclasts, while the rarity of abrasion shows a limited influence of hydraulic flows in transporting and remobilizing bioclasts. Thus, both sites preserve mostly autochthonous to parautochthonous bioclasts, with a moderate level of time-averaging. Our results corroborate the hypothesis that lentic environments can present remarkable preservational conditions for the formation of attritional accumulations of vertebrate remains. Moreover, we show how the different collecting methods affect the description of preservational features and taphonomic interpretations of both fossil assemblages.
{"title":"VERTEBRATE TAPHONOMY OF TWO UPPER MIOCENE BONEBEDS IN WESTERN PROTO-AMAZONIA (SOLIMÕES FORMATION, BRAZIL): INSIGHTS FROM MACROVERTEBRATE AND MICROVERTEBRATE FOSSILS","authors":"Fellipe P. Muniz, M. C. Bissaro-Júnior, E. Guilherme, Jonas Pereira de Souza Filho, F. R. Negri, A. S. Hsiou","doi":"10.2110/palo.2021.020","DOIUrl":"https://doi.org/10.2110/palo.2021.020","url":null,"abstract":"Abstract: The Niterói and Talismã sites comprise two of the most important fossiliferous deposits of the Neogene in Brazil. After 30 years of research, these sites have revealed rich assemblages of vertebrates and provided a glimpse of the Amazonian fauna and environment during the Miocene. Despite this, detailed studies that attempt to explain the genesis of these bonebeds are still scarce and hamper more robust paleoenvironmental and paleoecological reconstructions. Here we provide the first in-depth taphonomic analysis for both locations. Sedimentological and taphonomic evidence suggest that the depositional environments of Niterói and Talismã were similarly represented by shallow and calm waters in lacustrine/swampy contexts. We propose that the accumulation of bones and teeth is the result of attritional (day-to-day) mortality of organisms of the local community in a low sedimentation environment. The thanatocoenosis was exposed to biostratinomic processes for longer periods of time, which explains the high disarticulation, disassociation, fragmentation and loss of skeletal elements. The almost absence of weathering indicates that the aquatic environment slowed down the organic degradation of bioclasts, while the rarity of abrasion shows a limited influence of hydraulic flows in transporting and remobilizing bioclasts. Thus, both sites preserve mostly autochthonous to parautochthonous bioclasts, with a moderate level of time-averaging. Our results corroborate the hypothesis that lentic environments can present remarkable preservational conditions for the formation of attritional accumulations of vertebrate remains. Moreover, we show how the different collecting methods affect the description of preservational features and taphonomic interpretations of both fossil assemblages.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"269 - 282"},"PeriodicalIF":1.6,"publicationDate":"2021-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45887524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: Tectonic changes have influenced the evolution of the marine community by changing the land and seaway configuration through time. Two such events during the Oligo-Miocene—the closure of the Tethyan seaway due to development of the Gomphotherium Landbridge leading to separation of the Arabian Sea from proto-Mediterranean Sea (∼ 19 Ma) and significant uplift of the Tibetan Plateau marking the initiation of the monsoon (∼ 16 Ma)—represent a classic case of tectonic shift influencing the regional environment of the Indian subcontinent. We investigated the taxonomic and body-size related response of the shallow marine fauna to this regional change using bivalves from 11 time-constrained shellbeds of the Kutch Basin (western India) from three formations—Maniyara Fort (Chattian), Khari Nadi (Aquitanian) and Chhasra (Burdigalian-Langian) representing a time span of ∼ 9 Ma (24.4–15 Ma). Our collection of over 2000 individuals represents a total of 15 families and 61 morphospecies. The fossils are predominantly calcitic in nature and families of aragonitic composition are often preserved as molds indicating a potential negative effect of diagenesis. The taphonomic nature, however, does not vary substantially across shellbeds and hence, less likely produced a temporal pattern. The five most abundant species, Ostrea latimarginata, Ostrea angulata, Talochlamys articulata, Anomia primaeva, and Placuna lamellata occur in all the formations. The species composition of the Maniyara Fort Formation is substantially different from those of the younger formations, implying the possible effect of biogeographic separation. The absence of proto-Mediterranean taxa in Oligocene shellbeds supports limited faunal exchange between the Mediterranean-Iranian Province (MIP) and the western Indian Province (WIP) as early as ∼ 24.4 Ma (Chattian). Faunal exchange, however, continued between the WIP and the adjacent Eastern African-Arabian Province (EAAP). Formation-specific evenness shows a monotonic decrease from the Maniyara Fort to the Chhasra Formation. However, shellbed-specific analyses of diversity and body size do not show a strong directional trend through time and supports the stasis model. Although it is difficult to rule out the negative influence of taphonomy on the diversity of the studied fauna, the Oligo-Miocene marine bivalve fauna of the Kutch Basin demonstrates little or no influence of the Tethyan closure and Himalayan upliftment on the diversity through time.
{"title":"RESPONSE OF THE OLIGO-MIOCENE BIVALVE FAUNA OF THE KUTCH BASIN (WESTERN INDIA) TO REGIONAL TECTONIC EVENTS","authors":"S. Dutta, Devapriya Chattopadhyay","doi":"10.2110/palo.2020.040","DOIUrl":"https://doi.org/10.2110/palo.2020.040","url":null,"abstract":"Abstract: Tectonic changes have influenced the evolution of the marine community by changing the land and seaway configuration through time. Two such events during the Oligo-Miocene—the closure of the Tethyan seaway due to development of the Gomphotherium Landbridge leading to separation of the Arabian Sea from proto-Mediterranean Sea (∼ 19 Ma) and significant uplift of the Tibetan Plateau marking the initiation of the monsoon (∼ 16 Ma)—represent a classic case of tectonic shift influencing the regional environment of the Indian subcontinent. We investigated the taxonomic and body-size related response of the shallow marine fauna to this regional change using bivalves from 11 time-constrained shellbeds of the Kutch Basin (western India) from three formations—Maniyara Fort (Chattian), Khari Nadi (Aquitanian) and Chhasra (Burdigalian-Langian) representing a time span of ∼ 9 Ma (24.4–15 Ma). Our collection of over 2000 individuals represents a total of 15 families and 61 morphospecies. The fossils are predominantly calcitic in nature and families of aragonitic composition are often preserved as molds indicating a potential negative effect of diagenesis. The taphonomic nature, however, does not vary substantially across shellbeds and hence, less likely produced a temporal pattern. The five most abundant species, Ostrea latimarginata, Ostrea angulata, Talochlamys articulata, Anomia primaeva, and Placuna lamellata occur in all the formations. The species composition of the Maniyara Fort Formation is substantially different from those of the younger formations, implying the possible effect of biogeographic separation. The absence of proto-Mediterranean taxa in Oligocene shellbeds supports limited faunal exchange between the Mediterranean-Iranian Province (MIP) and the western Indian Province (WIP) as early as ∼ 24.4 Ma (Chattian). Faunal exchange, however, continued between the WIP and the adjacent Eastern African-Arabian Province (EAAP). Formation-specific evenness shows a monotonic decrease from the Maniyara Fort to the Chhasra Formation. However, shellbed-specific analyses of diversity and body size do not show a strong directional trend through time and supports the stasis model. Although it is difficult to rule out the negative influence of taphonomy on the diversity of the studied fauna, the Oligo-Miocene marine bivalve fauna of the Kutch Basin demonstrates little or no influence of the Tethyan closure and Himalayan upliftment on the diversity through time.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"73 - 87"},"PeriodicalIF":1.6,"publicationDate":"2021-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46942366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: The terrestrial feeding trace Edaphichnium lumbricatum is known from the Triassic to the Pleistocene and is characterized by tubular burrows with ellipsoidal fecal pellets, indicating substrate feeding by earthworms or other invertebrates. We describe 11 specimens attributable to Edaphichnium isp. from Egg Mountain, a terrestrial locality with a diverse fossil assemblage from the Upper Cretaceous Two Medicine Formation in Montana, USA, and assess their paleoenvironmental and paleoecological implications. These ichnofossils were recovered from a 1.5 meter stratigraphic succession comprised of calcareous siltstones and limestones with abundant fossil insect pupal cases, representing well-drained paleosols. Although burrows are not always present, three recurring arrangements of Edaphichnium isp. fecal pellets are identified: linearly arranged pellets, horizon-confined pellets, and pellets in clusters dispersed vertically and horizontally throughout the matrix. Two color patterns (light and dark pellets) are also distinguished. Pellets are fine-grained and have a consistently ellipsoidal shape (length:diameter of 1.57), with maximum lengths ranging from 1.9–6.7 mm (mean 4.1 mm) and maximum diameters ranging from 1.0–4.1 mm (mean 2.6 mm). Geochemical analyses indicate pellets are comprised of varying proportions of calcite, plagioclase, and quartz, and are enriched in phosphorus relative to the sedimentary host matrix. Possible trace makers include chafer or other coleopteran larvae, millipedes, and earthworms, suggesting a range of capable trace makers of Edaphichnium-like fecal pellets. Edaphichnium isp. at specific stratigraphic horizons suggests increased organic content in the subsurface, potentially connected to depositional hiatuses. Edaphichnium isp. adds a secondary component to the Celliforma ichnofacies known from Egg Mountain and surrounding strata, and to the array of nesting, feeding, and dwelling traces of wasps, beetles, other invertebrates, mammals, and dinosaurs from the locality.
{"title":"PALEOENVIRONMENTAL IMPLICATIONS OF INVERTEBRATE FECAL PELLETS (EDAPHICHNIUM ISP.) AT AN ICHNOFOSSIL-RICH DINOSAUR NESTING LOCALITY, UPPER CRETACEOUS TWO MEDICINE FORMATION, MONTANA, USA","authors":"William J. Freimuth, D. Varricchio, K. Chin","doi":"10.2110/palo.2021.003","DOIUrl":"https://doi.org/10.2110/palo.2021.003","url":null,"abstract":"Abstract: The terrestrial feeding trace Edaphichnium lumbricatum is known from the Triassic to the Pleistocene and is characterized by tubular burrows with ellipsoidal fecal pellets, indicating substrate feeding by earthworms or other invertebrates. We describe 11 specimens attributable to Edaphichnium isp. from Egg Mountain, a terrestrial locality with a diverse fossil assemblage from the Upper Cretaceous Two Medicine Formation in Montana, USA, and assess their paleoenvironmental and paleoecological implications. These ichnofossils were recovered from a 1.5 meter stratigraphic succession comprised of calcareous siltstones and limestones with abundant fossil insect pupal cases, representing well-drained paleosols. Although burrows are not always present, three recurring arrangements of Edaphichnium isp. fecal pellets are identified: linearly arranged pellets, horizon-confined pellets, and pellets in clusters dispersed vertically and horizontally throughout the matrix. Two color patterns (light and dark pellets) are also distinguished. Pellets are fine-grained and have a consistently ellipsoidal shape (length:diameter of 1.57), with maximum lengths ranging from 1.9–6.7 mm (mean 4.1 mm) and maximum diameters ranging from 1.0–4.1 mm (mean 2.6 mm). Geochemical analyses indicate pellets are comprised of varying proportions of calcite, plagioclase, and quartz, and are enriched in phosphorus relative to the sedimentary host matrix. Possible trace makers include chafer or other coleopteran larvae, millipedes, and earthworms, suggesting a range of capable trace makers of Edaphichnium-like fecal pellets. Edaphichnium isp. at specific stratigraphic horizons suggests increased organic content in the subsurface, potentially connected to depositional hiatuses. Edaphichnium isp. adds a secondary component to the Celliforma ichnofacies known from Egg Mountain and surrounding strata, and to the array of nesting, feeding, and dwelling traces of wasps, beetles, other invertebrates, mammals, and dinosaurs from the locality.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"283 - 300"},"PeriodicalIF":1.6,"publicationDate":"2021-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42420954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: Taxonomic comparisons of death assemblages with extant communities continue to provide insight for ecological studies but whether demographic aspects such as age structure, sex ratio, and causes of mortality are accurately captured by the former remains little studied. At a 110 ha dystropic lake in western Canada, seasonal shoreline accumulations of fish carcasses were collected annually for 12 years (N=4499) during 95 full lake-circuits and analyzed for taxa, body size frequencies, sex ratio relative to live-captures and sources of mortality. Rank order of the four fish species (Gasterosteus aculeatus, Oncorhynchus clarki, O. keta, Salvelinus malma) was similar for live-captures and carcasses. Of the dominant species (G. aculeatus), modal adult body length (∼80 mm SL) was the same for carcasses and live-captures and shifted by about 10% over 30 years with parallel trends between the groups for both sexes. Age-specific body size was about 5% larger (P<0.001) in carcasses than live-captures. Carcasses were significantly female-biased (2:1) each year relative to a population sex ratio of 1:1 in the lake. There was a complete absence of juvenile fish (<30 mm) among carcasses but these constituted 70% of the live population. Estimated relative contributions to mortality for the carcasses include starvation (<1%), parasitism (3%), senescence (4%) and lethal injuries from predator attack (70–80%). If these carcasses are representative of a fossil series in freshwater lake sediments, then several demographic parameters including age-specific body size, age-class frequencies and sex ratio depart substantially from the live population. As well, the virtual absence of avian piscivores in the carcass assemblage, the major source of predation on the fish population, warrants additional attention in paleoecological studies.
摘要：死亡组合与现存群落的分类学比较继续为生态学研究提供见解，但前者是否准确地捕捉到了人口统计学方面的信息，如年龄结构、性别比和死亡原因，目前研究较少。在加拿大西部一个110公顷的非热带湖泊，在95个完整的湖泊回路中，每年收集12年（N=4499）的季节性海岸线鱼类尸体堆积，并分析分类群、体型频率、与活捕获物的性别比和死亡率来源。四种鱼类（Gastrosteus acureatus、Oncorhynchus clarki、O.keta、Salvelinus malma）的活捕获物和尸体的等级顺序相似。在优势物种（G.acureatus）中，尸体和活体捕获的成年体长（~80 mm SL）相同，在30年内变化了约10%，两性之间的趋势平行。尸体中特定年龄的体型比活捕获的大约5%（P＜0.001）。相对于湖中1:1的种群性别比，每年的胴体都明显偏向雌性（2:1）。尸体中完全没有幼鱼（<30毫米），但这些幼鱼占活种群的70%。估计对尸体死亡率的相对贡献包括饥饿（<1%）、寄生（3%）、衰老（4%）和捕食者攻击造成的致命伤害（70-80%）。如果这些尸体是淡水湖沉积物中化石系列的代表，那么几个人口统计学参数，包括特定年龄的体型、年龄级频率和性别比，都与活种群有很大差异。此外，作为鱼类种群捕食的主要来源，尸体组合中几乎没有鸟类食豆动物，这值得古生态学研究给予更多关注。
{"title":"EVALUATING COMPOSITIONAL FIDELITY AND SOURCES OF MORTALITY OF SHORELINE FISH CARCASSES IN A FRESHWATER LAKE COMMUNITY IN WESTERN CANADA","authors":"T. Reimchen","doi":"10.2110/palo.2020.045","DOIUrl":"https://doi.org/10.2110/palo.2020.045","url":null,"abstract":"Abstract: Taxonomic comparisons of death assemblages with extant communities continue to provide insight for ecological studies but whether demographic aspects such as age structure, sex ratio, and causes of mortality are accurately captured by the former remains little studied. At a 110 ha dystropic lake in western Canada, seasonal shoreline accumulations of fish carcasses were collected annually for 12 years (N=4499) during 95 full lake-circuits and analyzed for taxa, body size frequencies, sex ratio relative to live-captures and sources of mortality. Rank order of the four fish species (Gasterosteus aculeatus, Oncorhynchus clarki, O. keta, Salvelinus malma) was similar for live-captures and carcasses. Of the dominant species (G. aculeatus), modal adult body length (∼80 mm SL) was the same for carcasses and live-captures and shifted by about 10% over 30 years with parallel trends between the groups for both sexes. Age-specific body size was about 5% larger (P<0.001) in carcasses than live-captures. Carcasses were significantly female-biased (2:1) each year relative to a population sex ratio of 1:1 in the lake. There was a complete absence of juvenile fish (<30 mm) among carcasses but these constituted 70% of the live population. Estimated relative contributions to mortality for the carcasses include starvation (<1%), parasitism (3%), senescence (4%) and lethal injuries from predator attack (70–80%). If these carcasses are representative of a fossil series in freshwater lake sediments, then several demographic parameters including age-specific body size, age-class frequencies and sex ratio depart substantially from the live population. As well, the virtual absence of avian piscivores in the carcass assemblage, the major source of predation on the fish population, warrants additional attention in paleoecological studies.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"260 - 268"},"PeriodicalIF":1.6,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46856285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Culver, S. Sutton, D. Mallinson, M. Buzas, M. Robinson, H. Dowsett
Abstract: The presence/absence and abundance of benthic foraminifera in successive discrete beds (Shattuck “zones”) of the Miocene Calvert and Choptank formations, exposed at the Calvert Cliffs, Maryland, USA, allows for investigation of community dynamics over space and time. The stratigraphic distribution of benthic foraminifera is documented and interpreted in the context of sea-level change, sequence stratigraphy, and the previously published distribution of mollusks. Neritic benthic foraminiferal communities of four sea-level cycles over ∼4 million years of the middle Miocene, encompassing the Miocene Climatic Optimum and the succeeding middle Miocene Climate Transition, are dominated by the same abundant species. They differ in the varying abundance of common species that occur throughout most of the studied section and in the different rare species that appear and disappear. Transgressive systems tracts (TSTs) have higher species diversity than highstand systems tracts (HSTs) but much lower density of specimens. In contrast to some previous research, all beds in the studied section are interpreted as being from the inner part of a broad, low gradient shelf and were deposited at water depths of less than ∼50 m. It is suggested that species are recruited from a regional species pool of propagules throughout the duration of TSTs. Recruitment is curtailed during highstands leading to lower diversity in the HSTs.
{"title":"MIOCENE NERITIC BENTHIC FORAMINIFERAL COMMUNITY DYNAMICS, CALVERT CLIFFS, MARYLAND, USA: SPECIES POOL, PATTERNS AND PROCESSES","authors":"S. Culver, S. Sutton, D. Mallinson, M. Buzas, M. Robinson, H. Dowsett","doi":"10.2110/palo.2020.069","DOIUrl":"https://doi.org/10.2110/palo.2020.069","url":null,"abstract":"Abstract: The presence/absence and abundance of benthic foraminifera in successive discrete beds (Shattuck “zones”) of the Miocene Calvert and Choptank formations, exposed at the Calvert Cliffs, Maryland, USA, allows for investigation of community dynamics over space and time. The stratigraphic distribution of benthic foraminifera is documented and interpreted in the context of sea-level change, sequence stratigraphy, and the previously published distribution of mollusks. Neritic benthic foraminiferal communities of four sea-level cycles over ∼4 million years of the middle Miocene, encompassing the Miocene Climatic Optimum and the succeeding middle Miocene Climate Transition, are dominated by the same abundant species. They differ in the varying abundance of common species that occur throughout most of the studied section and in the different rare species that appear and disappear. Transgressive systems tracts (TSTs) have higher species diversity than highstand systems tracts (HSTs) but much lower density of specimens. In contrast to some previous research, all beds in the studied section are interpreted as being from the inner part of a broad, low gradient shelf and were deposited at water depths of less than ∼50 m. It is suggested that species are recruited from a regional species pool of propagules throughout the duration of TSTs. Recruitment is curtailed during highstands leading to lower diversity in the HSTs.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"247 - 259"},"PeriodicalIF":1.6,"publicationDate":"2021-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42801931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: This is a neoichnologic study of Microcavia australis (Rodentia: Caviidae) burrow systems from two environments of the semiarid region of central Argentina, with the main purpose of contributing to the interpretation of fossil tetrapod burrows. We compared three burrow systems from the Monte and three from the Espinal biogeographic provinces to discern which burrow system features vary with environmental parameters (soil texture, climatic conditions, and vegetation type) and identify the distinctive ichnologic features of M. australis burrow systems. Burrow systems from the Monte occur in nebkhas with sparse xerophytic, psammophilic, and halophilic shrubs in sandy and loose soils. In the Espinal province the burrows appear in Prosopis caldenia forest, with shrubs and herbs in silty and harder soils. The Monte burrow systems comprise an intricate pattern with two levels, closed circuits, and larger tortuosity and fractal dimension. The burrow systems from the Espinal display an L-shaped or linear pattern with a single level and commonly lack closed circuits. The average ratio of total chamber volume to tunnel volume and the tunnel diameter is significantly larger in the Monte systems, which is interpreted as a reflection of larger colony size and individuals having larger body mass. Primary surface ornamentation (sets of claw traces related to producer digging) is better developed in the Espinal burrow systems, and secondary surface ornamentation (herein interpreted as arthropod burrows) dominated in the Monte systems. We propose that the distinctive features of M. australis burrow systems can be used as a model to recognize fossil burrows of colonial and fossorial herbivorous rodents that construct a permanent burrow structure with open entrances in semiarid settings. A set of ichnotaxobases for fossil vertebrate burrows is also suggested.
{"title":"ENVIRONMENTAL INFLUENCE ON BURROW SYSTEM FEATURES OF A COLONIAL AND FOSSORIAL RODENT: IMPLICATIONS FOR INTERPRETING FOSSIL TETRAPOD BURROWS","authors":"M. C. Cardonatto, Ricardo N. Melchor","doi":"10.2110/palo.2020.065","DOIUrl":"https://doi.org/10.2110/palo.2020.065","url":null,"abstract":"Abstract: This is a neoichnologic study of Microcavia australis (Rodentia: Caviidae) burrow systems from two environments of the semiarid region of central Argentina, with the main purpose of contributing to the interpretation of fossil tetrapod burrows. We compared three burrow systems from the Monte and three from the Espinal biogeographic provinces to discern which burrow system features vary with environmental parameters (soil texture, climatic conditions, and vegetation type) and identify the distinctive ichnologic features of M. australis burrow systems. Burrow systems from the Monte occur in nebkhas with sparse xerophytic, psammophilic, and halophilic shrubs in sandy and loose soils. In the Espinal province the burrows appear in Prosopis caldenia forest, with shrubs and herbs in silty and harder soils. The Monte burrow systems comprise an intricate pattern with two levels, closed circuits, and larger tortuosity and fractal dimension. The burrow systems from the Espinal display an L-shaped or linear pattern with a single level and commonly lack closed circuits. The average ratio of total chamber volume to tunnel volume and the tunnel diameter is significantly larger in the Monte systems, which is interpreted as a reflection of larger colony size and individuals having larger body mass. Primary surface ornamentation (sets of claw traces related to producer digging) is better developed in the Espinal burrow systems, and secondary surface ornamentation (herein interpreted as arthropod burrows) dominated in the Monte systems. We propose that the distinctive features of M. australis burrow systems can be used as a model to recognize fossil burrows of colonial and fossorial herbivorous rodents that construct a permanent burrow structure with open entrances in semiarid settings. A set of ichnotaxobases for fossil vertebrate burrows is also suggested.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"41 1","pages":"225 - 245"},"PeriodicalIF":1.6,"publicationDate":"2021-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67708587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: Laboratory-based decay experiments have become commonly used to supplement our understanding of how organisms enter the fossil record. Differences in how these experiments are designed and evaluated, however, including dissimilarities in qualitative decay-scoring indices superimposed on variability in model organisms, renders any semblance of comparison between studies unreliable. Here, we introduce the utility of X-ray tomographic microscopy (µCT) as a means for reliable and repeatable analysis of soft-tissue decay experiment products. As proof-of-concept, we used a relatively simple experimental design with classic studies as comparators, and present our analytical protocol using µCT for capturing the entire volume of the decay subject. Segmentation software then allows for 3D volume analysis and high-resolution internal and external character identification. We describe the workflow from sample preparation, contrast-staining, and data collection to processing and analysis of the resulting data, using peppermint shrimp (Lysmata wurdemanni) as model organisms, and compare our results to previous taphonomic studies. These methods allow for improved visualization and quantification of decay and internal volume analysis with minimal handling as compared to traditional qualitative scoring methods. Using the same scoring criteria as previous studies, this study revealed similar decay results for certain features, while we were additionally able to detect other feature loss or alteration earlier—importantly without need for potentially distortive sample handling. We conclude that µCT is a more effective, straightforward, and exact means for extracting quantitative data on the progression of decay and should be adopted in future studies, where available, to streamline and standardize comparisons.
{"title":"X-RAY TOMOGRAPHIC MICROSCOPY AS A MEANS TO SYSTEMATICALLY TRACK EXPERIMENTAL DECAY AND FOSSILIZATION","authors":"T. Selly, J. Schiffbauer","doi":"10.2110/palo.2021.004","DOIUrl":"https://doi.org/10.2110/palo.2021.004","url":null,"abstract":"Abstract: Laboratory-based decay experiments have become commonly used to supplement our understanding of how organisms enter the fossil record. Differences in how these experiments are designed and evaluated, however, including dissimilarities in qualitative decay-scoring indices superimposed on variability in model organisms, renders any semblance of comparison between studies unreliable. Here, we introduce the utility of X-ray tomographic microscopy (µCT) as a means for reliable and repeatable analysis of soft-tissue decay experiment products. As proof-of-concept, we used a relatively simple experimental design with classic studies as comparators, and present our analytical protocol using µCT for capturing the entire volume of the decay subject. Segmentation software then allows for 3D volume analysis and high-resolution internal and external character identification. We describe the workflow from sample preparation, contrast-staining, and data collection to processing and analysis of the resulting data, using peppermint shrimp (Lysmata wurdemanni) as model organisms, and compare our results to previous taphonomic studies. These methods allow for improved visualization and quantification of decay and internal volume analysis with minimal handling as compared to traditional qualitative scoring methods. Using the same scoring criteria as previous studies, this study revealed similar decay results for certain features, while we were additionally able to detect other feature loss or alteration earlier—importantly without need for potentially distortive sample handling. We conclude that µCT is a more effective, straightforward, and exact means for extracting quantitative data on the progression of decay and should be adopted in future studies, where available, to streamline and standardize comparisons.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"216 - 224"},"PeriodicalIF":1.6,"publicationDate":"2021-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46374253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. McLain, P. Ullmann, R. Ash, Keifer Bohnstedt, D. Nelsen, Robert O. Clark, L. Brand, A. Chadwick
Abstract: A dinosaur-bearing bonebed (Rose Quarry) from the uppermost Cretaceous (Maastrichtian) Lance Formation has yielded abundant, yet fragmentary, disarticulated, and disassociated bones and teeth of dinosaurs, turtles, crocodilians, and fish contained within a channelized sandstone unit along with large mud clasts. The vertebrate fossils of Rose Quarry possess varying abrasion states, tooth traces, and trampling marks, suggesting a complicated taphonomic history. To independently test hypotheses about the genesis of the assemblage, Rose Quarry bone samples were sent to members of our team who conducted “blind” analyses of their trace element signatures without knowledge of the physical taphonomic attributes of each specimen. The independent analyses of the chemical and physical taphonomic signatures both support a mixed, attritional bone concentration. Based on our cumulative data, we present a depositional model for the Rose Quarry bonebed in which a flooding event mixed bones already present in the channel or from an older bonebed with bones from the floodplain that had been scavenged, trampled, and broken. Our study demonstrates that striking variability is possible among fluvial bonebeds, and that such variability is influenced by pre-burial and post-burial factors, as well as depositional subenvironments and burial mechanisms. Additionally, we demonstrate that physical and chemical taphonomic analyses can independently confirm the taphonomic history of a bonebed.
{"title":"INDEPENDENT CONFIRMATION OF FLUVIAL REWORKING AT A LANCE FORMATION (MAASTRICHTIAN) BONEBED BY TRADITIONAL AND CHEMICAL TAPHONOMIC ANALYSES","authors":"M. McLain, P. Ullmann, R. Ash, Keifer Bohnstedt, D. Nelsen, Robert O. Clark, L. Brand, A. Chadwick","doi":"10.2110/palo.2020.064","DOIUrl":"https://doi.org/10.2110/palo.2020.064","url":null,"abstract":"Abstract: A dinosaur-bearing bonebed (Rose Quarry) from the uppermost Cretaceous (Maastrichtian) Lance Formation has yielded abundant, yet fragmentary, disarticulated, and disassociated bones and teeth of dinosaurs, turtles, crocodilians, and fish contained within a channelized sandstone unit along with large mud clasts. The vertebrate fossils of Rose Quarry possess varying abrasion states, tooth traces, and trampling marks, suggesting a complicated taphonomic history. To independently test hypotheses about the genesis of the assemblage, Rose Quarry bone samples were sent to members of our team who conducted “blind” analyses of their trace element signatures without knowledge of the physical taphonomic attributes of each specimen. The independent analyses of the chemical and physical taphonomic signatures both support a mixed, attritional bone concentration. Based on our cumulative data, we present a depositional model for the Rose Quarry bonebed in which a flooding event mixed bones already present in the channel or from an older bonebed with bones from the floodplain that had been scavenged, trampled, and broken. Our study demonstrates that striking variability is possible among fluvial bonebeds, and that such variability is influenced by pre-burial and post-burial factors, as well as depositional subenvironments and burial mechanisms. Additionally, we demonstrate that physical and chemical taphonomic analyses can independently confirm the taphonomic history of a bonebed.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"193 - 215"},"PeriodicalIF":1.6,"publicationDate":"2021-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46278975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. I. Bezerra, Enzo Victorino Hernández Agressot, M. Solórzano-Kraemer, Paulo Tarso C. Freire, A. R. Paschoal, J. H. Da Silva, M. Mendes
Abstract: The Fonseca Formation (Eocene–Oligocene boundary, Minas Gerais, Brazil) is well known for its paleoflora, especially of flowering plants. The richness of this insect-bearing fossil locality is significantly less well understood, but we can shed light on the insect paleocommunity. One hundred and eight fossil insect specimens were examined and separated into four grades based on their preservational quality. We conducted analyses of taphonomic features, including body orientation, size, articulation, and chemical composition. Our results reveal differences in the body articulation of the insects. The fully articulated specimens apparently did not experience extensive flotation time at the water-air interface, whereas for partially articulated and disarticulated specimens the opposite is true. These taphonomic features would be acquired during the biostratinomy stage, and not early diagenesis. We also employed high resolution techniques (SEM-EDS and Raman spectroscopy) to understand their fossilization potential. Our chemical data suggest that the Fonseca insects are preserved as organic remains in carbonaceous compressions. Thus, chitin biomolecules most likely were transformed into more resistant biopolymers during diagenesis. This interpretation may also imply that the carbonaceous material originated from the insect itself. In this study, we document new discoveries and also provide future prospects for study of the Fonseca Formation.
{"title":"TAPHONOMIC ANALYSIS OF THE PALEOENTOMOFAUNA ASSEMBLAGE FROM THE CENOZOIC OF THE FONSECA BASIN, SOUTHEASTERN BRAZIL","authors":"F. I. Bezerra, Enzo Victorino Hernández Agressot, M. Solórzano-Kraemer, Paulo Tarso C. Freire, A. R. Paschoal, J. H. Da Silva, M. Mendes","doi":"10.2110/palo.2020.067","DOIUrl":"https://doi.org/10.2110/palo.2020.067","url":null,"abstract":"Abstract: The Fonseca Formation (Eocene–Oligocene boundary, Minas Gerais, Brazil) is well known for its paleoflora, especially of flowering plants. The richness of this insect-bearing fossil locality is significantly less well understood, but we can shed light on the insect paleocommunity. One hundred and eight fossil insect specimens were examined and separated into four grades based on their preservational quality. We conducted analyses of taphonomic features, including body orientation, size, articulation, and chemical composition. Our results reveal differences in the body articulation of the insects. The fully articulated specimens apparently did not experience extensive flotation time at the water-air interface, whereas for partially articulated and disarticulated specimens the opposite is true. These taphonomic features would be acquired during the biostratinomy stage, and not early diagenesis. We also employed high resolution techniques (SEM-EDS and Raman spectroscopy) to understand their fossilization potential. Our chemical data suggest that the Fonseca insects are preserved as organic remains in carbonaceous compressions. Thus, chitin biomolecules most likely were transformed into more resistant biopolymers during diagenesis. This interpretation may also imply that the carbonaceous material originated from the insect itself. In this study, we document new discoveries and also provide future prospects for study of the Fonseca Formation.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"182 - 192"},"PeriodicalIF":1.6,"publicationDate":"2021-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43856311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract: The Paleozoic evolution of vegetation transformed terrestrial landscapes, facilitating novel sedimentary processes and creating new habitats. This transformation left a permanent mark on the sedimentary record, perhaps most strikingly via an upsurge in preserved terrestrial mudrock. Whereas feedbacks between evolving vegetation and river structure have been widely studied, Paleozoic estuaries have so far received scant attention. Located at the interface between the land and sea, the co-adjustment of estuarine morphology and plant traits are fundamentally tied to a varied range of geochemical cycles, and determine how global silicate weathering patterns may have varied over time. Here we employ an eco-morphodynamic model with an in-built vegetation code to simulate estuarine morphology through five key stages in plant evolution. An abiotic model (early Precambrian?) saw mud deposition restricted to fortuitous instances of limited erosion along bar-flanks. Estuaries colonized by microbial mats (Precambrian onwards) facilitated mud accretion that sufficiently stabilized bar surfaces to promote extensive mudflat development. Small-stature, rootless vegetation (Silurian–Early Devonian) introduced novel above-ground baffling effects which led to notable mud accumulation in lower-energy environments. The incorporation of roots (Early Devonian) strengthened these trends, with root structures decreasing the mortality of the occupying plants. Once the full complement of modern vascular plant architectures had evolved (Middle Devonian), dense colonization promoted the formation of in-channel islands accompanied with system-wide mud accumulation. These simulations suggest estuaries underwent profound change during the Paleozoic, with the greening of the continents triggering processes and feedbacks which render all previous source-to-sink sediment pathways non-uniformitarian.
{"title":"MUDDYING THE WATERS: MODELING THE EFFECTS OF EARLY LAND PLANTS IN PALEOZOIC ESTUARIES","authors":"M. Brückner, W. McMahon, M. Kleinhans","doi":"10.2110/palo.2020.073","DOIUrl":"https://doi.org/10.2110/palo.2020.073","url":null,"abstract":"Abstract: The Paleozoic evolution of vegetation transformed terrestrial landscapes, facilitating novel sedimentary processes and creating new habitats. This transformation left a permanent mark on the sedimentary record, perhaps most strikingly via an upsurge in preserved terrestrial mudrock. Whereas feedbacks between evolving vegetation and river structure have been widely studied, Paleozoic estuaries have so far received scant attention. Located at the interface between the land and sea, the co-adjustment of estuarine morphology and plant traits are fundamentally tied to a varied range of geochemical cycles, and determine how global silicate weathering patterns may have varied over time. Here we employ an eco-morphodynamic model with an in-built vegetation code to simulate estuarine morphology through five key stages in plant evolution. An abiotic model (early Precambrian?) saw mud deposition restricted to fortuitous instances of limited erosion along bar-flanks. Estuaries colonized by microbial mats (Precambrian onwards) facilitated mud accretion that sufficiently stabilized bar surfaces to promote extensive mudflat development. Small-stature, rootless vegetation (Silurian–Early Devonian) introduced novel above-ground baffling effects which led to notable mud accumulation in lower-energy environments. The incorporation of roots (Early Devonian) strengthened these trends, with root structures decreasing the mortality of the occupying plants. Once the full complement of modern vascular plant architectures had evolved (Middle Devonian), dense colonization promoted the formation of in-channel islands accompanied with system-wide mud accumulation. These simulations suggest estuaries underwent profound change during the Paleozoic, with the greening of the continents triggering processes and feedbacks which render all previous source-to-sink sediment pathways non-uniformitarian.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"36 1","pages":"173 - 181"},"PeriodicalIF":1.6,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46144953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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