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1.
Science ; 368(6489): 420-424, 2020 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-32327597

RESUMO

The global fossil record of marine animals has fueled long-standing debates about diversity change through time and the drivers of this change. However, the fossil record is not truly global. It varies considerably in geographic scope and in the sampling of environments among intervals of geological time. We account for this variability using a spatially explicit approach to quantify regional-scale diversity through the Phanerozoic. Among-region variation in diversity is comparable to variation through time, and much of this is explained by environmental factors, particularly the extent of reefs. By contrast, influential hypotheses of diversity change through time, including sustained long-term increases, have little explanatory power. Modeling the spatial structure of the fossil record transforms interpretations of Phanerozoic diversity patterns and their macroevolutionary explanations. This necessitates a refocus of deep-time diversification studies.


Assuntos
Organismos Aquáticos , Biodiversidade , Fósseis , Animais , Paleontologia
2.
Nature ; 580(7804): 502-505, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32322065

RESUMO

Time-calibrated phylogenies of extant species (referred to here as 'extant timetrees') are widely used for estimating diversification dynamics1. However, there has been considerable debate surrounding the reliability of these inferences2-5 and, to date, this critical question remains unresolved. Here we clarify the precise information that can be extracted from extant timetrees under the generalized birth-death model, which underlies most existing methods of estimation. We prove that, for any diversification scenario, there exists an infinite number of alternative diversification scenarios that are equally likely to have generated any given extant timetree. These 'congruent' scenarios cannot possibly be distinguished using extant timetrees alone, even in the presence of infinite data. Importantly, congruent diversification scenarios can exhibit markedly different and yet similarly plausible dynamics, which suggests that many previous studies may have over-interpreted phylogenetic evidence. We introduce identifiable and easily interpretable variables that contain all available information about past diversification dynamics, and demonstrate that these can be estimated from extant timetrees. We suggest that measuring and modelling these identifiable variables offers a more robust way to study historical diversification dynamics. Our findings also make it clear that palaeontological data will continue to be crucial for answering some macroevolutionary questions.


Assuntos
Biodiversidade , Modelos Biológicos , Filogenia , Animais , Calibragem , Extinção Biológica , Especiação Genética , Paleontologia , Reprodutibilidade dos Testes , Fatores de Tempo
3.
Proc Natl Acad Sci U S A ; 117(13): 7038-7043, 2020 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-32179672

RESUMO

Paleoclimate research has built a framework for Earth's climate changes over the past 65 million years or even longer. However, our knowledge of weather-timescale extreme events (WEEs, also named paleoweather), which usually occur over several days or hours, under different climate regimes is almost blank because current paleoclimatic records rarely provide information with temporal resolution shorter than monthly scale. Here we show that giant clam shells (Tridacna spp.) from the tropical western Pacific have clear daily growth bands, and several 2-y-long (from January 29, 2012 to December 9, 2013) daily to hourly resolution biological and geochemical records, including daily growth rate, hourly elements/Ca ratios, and fluorescence intensity, were obtained. We found that the pulsed changes of these ultra-high-resolution proxy records clearly matched with the typical instrumental WEEs, for example, tropical cyclones during the summer-autumn and cold surges during the winter. When a tropical cyclone passes through or approaches the sampling site, the growth rate of Tridacna shell decreases abruptly due to the bad weather. Meanwhile, enhanced vertical mixing brings nutrient-enriched subsurface water to the surface, resulting in a high Fe/Ca ratio and strong fluorescence intensity (induced by phytoplankton bloom) in the shell. Our results demonstrate that Tridacna shell has the potential to be used as an ultra-high-resolution archive for paleoweather reconstructions. The fossil shells living in different geological times can be built as a Geological Weather Station network to lengthen the modern instrumental data and investigate the WEEs under various climate conditions.


Assuntos
Bivalves/química , Bivalves/crescimento & desenvolvimento , Clima Extremo , Paleontologia/métodos , Animais
4.
Proc Natl Acad Sci U S A ; 117(14): 7845-7850, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32205432

RESUMO

Analysis of modern animals and Ediacaran trace fossils predicts that the oldest bilaterians were simple and small. Such organisms would be difficult to recognize in the fossil record, but should have been part of the Ediacara Biota, the earliest preserved macroscopic, complex animal communities. Here, we describe Ikaria wariootia gen. et sp. nov. from the Ediacara Member, South Australia, a small, simple organism with anterior/posterior differentiation. We find that the size and morphology of Ikaria match predictions for the progenitor of the trace fossil Helminthoidichnites-indicative of mobility and sediment displacement. In the Ediacara Member, Helminthoidichnites occurs stratigraphically below classic Ediacara body fossils. Together, these suggest that Ikaria represents one of the oldest total group bilaterians identified from South Australia, with little deviation from the characters predicted for their last common ancestor. Further, these trace fossils persist into the Phanerozoic, providing a critical link between Ediacaran and Cambrian animals.


Assuntos
Evolução Biológica , Biota/genética , Fósseis , Paleontologia , Animais , Humanos , Amplitude de Movimento Articular/fisiologia , Austrália do Sul
5.
PLoS One ; 15(3): e0229640, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32160212

RESUMO

Dinosaur fossils from the Middle Jurassic are rare globally, but the Isle of Skye (Scotland, UK) preserves a varied dinosaur record of abundant trace fossils and rare body fossils from this time. Here we describe two new tracksites from Rubha nam Brathairean (Brothers' Point) near where the first dinosaur footprint in Scotland was found in the 1980s. These sites were formed in subaerially exposed mudstones of the Lealt Shale Formation of the Great Estuarine Group and record a dynamic, subtropical, coastal margin. These tracksites preserve a wide variety of dinosaur track types, including a novel morphotype for Skye: Deltapodus which has a probable stegosaur trackmaker. Additionally, a wide variety of tridactyl tracks shows evidence of multiple theropods of different sizes and possibly hints at the presence of large-bodied ornithopods. Overall, the new tracksites show the dinosaur fauna of Skye is more diverse than previously recognized and give insight into the early evolution of major dinosaur groups whose Middle Jurassic body fossil records are currently sparse.


Assuntos
Dinossauros/classificação , Animais , Biodiversidade , Dinossauros/anatomia & histologia , Dinossauros/fisiologia , Fósseis , Marcha/fisiologia , História Antiga , Locomoção/fisiologia , Paleontologia , Escócia
6.
Nat Commun ; 11(1): 1534, 2020 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-32210225

RESUMO

Changes in ocean circulation and the biological carbon pump have been implicated as the drivers behind the rise in atmospheric CO2 across the last deglaciation; however, the processes involved remain uncertain. Previous records have hinted at a partitioning of deep ocean ventilation across the two major intervals of atmospheric CO2 rise, but the consequences of differential ventilation on the Si cycle has not been explored. Here we present three new records of silicon isotopes in diatoms and sponges from the Southern Ocean that together show increased Si supply from deep mixing during the deglaciation with a maximum during the Younger Dryas (YD). We suggest Antarctic sea ice and Atlantic overturning conditions favoured abyssal ocean ventilation at the YD and marked an interval of Si cycle reorganisation. By regulating the strength of the biological pump, the glacial-interglacial shift in the Si cycle may present an important control on Pleistocene CO2 concentrations.


Assuntos
Atmosfera/química , Camada de Gelo/química , Isótopos/metabolismo , Água do Mar/química , Silício/metabolismo , Movimentos da Água , Regiões Antárticas , Oceano Atlântico , Dióxido de Carbono/metabolismo , História Antiga , Isótopos/análise , Oceanografia/métodos , Paleontologia/métodos , Água do Mar/análise , Silício/análise , Temperatura
7.
Nat Commun ; 11(1): 1261, 2020 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-32152319

RESUMO

The Ediacara biota represents the first complex macroscopic organisms in the geological record, foreshadowing the radiation of eumetazoan animals in the Cambrian explosion. However, little is known about the contingencies that lead to their emergence, including the possible roles of nutrient availability and the quality of food sources. Here we present information on primary producers in the Ediacaran based on biomarker molecules that were extracted from sediments hosting Ediacaran macrofossils. High relative abundances of algal steranes over bacterial hopanes suggest that the Ediacara biota inhabited nutrient replete environments with an abundance of algal food sources comparable to Phanerozoic ecosystems. Thus, organisms of the Ediacara biota inhabited nutrient-rich environments akin to those that later fuelled the Cambrian explosion.


Assuntos
Ecologia , Alimentos , Thoracica/fisiologia , Animais , Bactérias , Evolução Biológica , Biomarcadores , Ciclo do Carbono , Ecossistema , Fósseis , Sedimentos Geológicos/química , Paleontologia
8.
Nature ; 579(7799): 351-352, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32188944
9.
PLoS One ; 15(2): e0228944, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32045457

RESUMO

There are multiple common methods for collecting fossil material in the field for paleoecological analyses, so it is important to determine if and how different methods may affect the similarities and differences among taxonomic samples. Here, we evaluate the influence of two fossil collection field methods (stratigraphically in-place bulk-sediment versus picking up weathered-out fossils from the ground surface) on paleoecological results, using the Pennsylvanian marine invertebrate assemblages of the Finis Shale in Texas. Based on an informal review of recent paleoecology papers, we observed that the lithology of the study material and the nature of the research question correspond to choice of field collection protocols; however, collection protocols are not always clearly explained or justified in the text of the papers. For the present case study, we collected stratigraphically equivalent samples from three outcrops using both the surface pick-up and in-place bulk sediment methods. We found a difference in the abundance and composition of paleocommunities between these two collection methods. Evidence to support this includes the significant differences between samples using PERMANOVA (p < 0.001), the clear separation in ordination space of samples clustered by sampling method, the significantly higher richness in the surface samples (p < 0.001), and the considerable variation in relative abundances of various taxa and taxonomic groups. Richness and evenness were higher among the surface-collected samples, possibly due to collector bias, weathering artifacts, or spatial and temporal variability. Paleontologists strive to do the best science possible with the material available. Often, paleoecological research methods are limited by time, funding, or the nature of the material. In such cases, we recommend examining both collection methods, even if for only a fraction of the sampling. If only one method is possible, we recommend the use in-place, bulk-collected samples.


Assuntos
Paleontologia/métodos , Manejo de Espécimes/métodos , Animais , Fósseis/anatomia & histologia , Humanos , Texas
10.
Naturwissenschaften ; 107(2): 10, 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-32020295

RESUMO

Reconstructing the living environment of extinct vertebrates is often challenging due to the lack of proxies. We propose a new proxy to the living environment based on the combined oxygen and sulphur stable isotope analysis of vertebrate hydroxyapatite. We tested this isotopic proxy to 64 biogenic apatite (bones) samples that represent a wide spectrum of the extant vertebrate phylogenetic diversity including crocodiles, snakes, turtles, mammals, birds, lizards, fish and amphibians. We show that the combination of these two isotopic systems allows the living environment of all these vertebrates to be unambiguously distinguished between freshwater (aquatic vs semi-aquatic), seawater (aquatic vs semi-aquatic) and terrestrial. The main goal of this study is to provide a present-day isotopic reference frame and to discuss methodological issues that will serve to interpret future oxygen and sulphur isotope results obtained either from fossil or modern skeletal material. This new isotopic approach of combined oxygen and sulphur isotope analysis will be particularly useful to document major aquatic-terrestrial transitions in the fossil record but also to better constrain the living environment of some present-day species.


Assuntos
Ecologia/métodos , Isótopos de Oxigênio/análise , Paleontologia/métodos , Isótopos de Enxofre/análise , Vertebrados/classificação , Animais
11.
PLoS One ; 15(2): e0228546, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32027712

RESUMO

A cave site Shelter in Smolen III (southern Poland) contains an approximately 2-m-thick stratified sequence of Upper Pleistocene and Holocene clastic sediments, unique for Central Europe. The sequence contents abundant fossil fauna, including mollusk, rodent and bat remains. The cave sites with long profiles of subfossil fauna present a great value for reconstructions of regional terrestrial paleoenvironment. We explore the stratigraphy of this site through analyses of the lithology and geochemistry of sediments, radiocarbon dating of faunal and human remains and charcoals, and archaeological study, as well as the paleoecology derived from the taxonomic composition of fossil faunal assemblages. Our data show that the entire period of the Holocene is recorded in the rockshelter, which makes that site an exceptional and highly valuable case. We present paleoenvironmental reconstructions of regional importance, and we propose to regard Shelter in Smolen III as a regional stratigraphic stratotype of Holocene clastic cave sediments.


Assuntos
Arqueologia/métodos , Cavernas/química , Sedimentos Geológicos/análise , Paleontologia/métodos , Animais , Quirópteros/classificação , Classificação , Bases de Dados Factuais , Europa (Continente) , Fósseis/patologia , História Antiga , Humanos , Moluscos/classificação , Polônia , Roedores/classificação
12.
Proc Biol Sci ; 287(1920): 20192806, 2020 02 12.
Artigo em Inglês | MEDLINE | ID: mdl-32075529

RESUMO

By their past and present diversity, rodents are among the richest components of Caribbean land mammals. Many of these became extinct recently. Causes of their extirpation, their phylogenetic affinities, the timing of their arrival in the West Indies and their biogeographic history are all ongoing debated issues. Here, we report the discovery of dental remains from Lower Oligocene deposits (ca 29.5 Ma) of Puerto Rico. Their morphology attests to the presence of two distinct species of chinchilloid caviomorphs, closely related to dinomyids in a phylogenetic analysis, and thus of undisputable South American origin. These fossils represent the earliest Caribbean rodents known thus far. They could extend back to 30 Ma the lineages of some recently extinct Caribbean giant rodents (Elasmodontomys and Amblyrhiza), which are also retrieved here as chinchilloids. This new find has substantial biogeographic implications because it demonstrates an early dispersal of land mammals from South America to the West Indies, perhaps via the emergence of the Aves Ridge that occurred ca 35-33 Ma (GAARlandia hypothesis). Considering both this new palaeontological evidence and recent molecular divergence estimates, the natural colonization of the West Indies by rodents probably occurred through multiple and time-staggered dispersal events (chinchilloids, then echimyid octodontoids (spiny rats/hutias), caviids and lastly oryzomyin muroids (rice rats)).


Assuntos
Evolução Biológica , Filogenia , Roedores , Animais , Fósseis , Paleontologia , Índias Ocidentais
13.
PLoS One ; 15(2): e0229687, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32092121

RESUMO

Radiogenic strontium isotopes (87Sr/86Sr) have long been used in analyses of paleomobility within Mesoamerica. While considerable effort has been expended developing 87Sr/86Sr baseline values across the Maya region, work in central Mexico is primarily focused on the Classic period urban center of Teotihuacan. This study adds to this important dataset by presenting bioavailable 87Sr/86Sr values across central Mexico focusing on the Basin of Mexico. This study therefore serves to expand the utility of strontium isotopes across a wider geographic region. A total of 63 plant and water samples were collected from 13 central Mexican sites and analyzed for 87Sr/86Sr on a Thermo-Finnigan Neptune multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). These data were analyzed alongside 16 published 87Sr/86Sr values from two additional sites within the region of interest. A five-cluster k-means model was then generated to determine which regions of the Basin of Mexico and greater central Mexico can and cannot be distinguished isotopically using 87Sr/86Sr values. Although the two clusters falling within the Basin of Mexico overlap in their local 87Sr/86Sr ranges, many locations within the Basin are distinguishable using 87Sr/86Sr values at the site-level. This study contributes to paleomobility studies within central Mexico by expanding knowledge of strontium isotope variability within the region, ultimately allowing researchers to detect intra-regional residential mobility and gain a greater understanding of the sociopolitical interactions between the Basin of Mexico and supporting outlying regions of central Mexico.


Assuntos
Paleontologia/métodos , Isótopos de Estrôncio/análise , Estrôncio/análise , Monitoramento Ambiental/métodos , Monitoramento Ambiental/normas , México , Radioisótopos
15.
Proc Natl Acad Sci U S A ; 117(5): 2255-2264, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31964850

RESUMO

A climate/vegetation model simulates episodic wetter and drier periods at the 21,000-y precession period in eastern North Africa, the Arabian Peninsula, and the Levant over the past 140,000 y. Large orbitally forced wet/dry extremes occur during interglacial time, ∼130 to 80 ka, and conditions between these two extremes prevail during glacial time, ∼70 to 15 ka. Orbital precession causes high seasonality in Northern Hemisphere (NH) insolation at ∼125, 105, and 83 ka, with stronger and northward extended summer monsoon rains in North Africa and the Arabian Peninsula and increased winter rains in the Mediterranean Basin. The combined effects of these two seasonally distinct rainfall regimes increase vegetation and narrow the width of the Saharan-Arabian desert and semidesert zones. During the opposite phase of the precession cycle (∼115, 95, and 73 ka), NH seasonality is low, and decreased summer insolation and increased winter insolation cause monsoon and storm track rains to decrease and the width of the desert zone to increase. During glacial time (∼70 to 15 ka), forcing from large ice sheets and lowered greenhouse gas concentrations combine to increase winter Mediterranean storm track precipitation; the southward retreat of the northern limit of summer monsoon rains is relatively small, thereby limiting the expansion of deserts. The lowered greenhouse gas concentrations cause the near-equatorial zone to cool and reduce convection, causing drier climate with reduced forest cover. At most locations and times, the simulations agree with environmental observations. These changing regional patterns of climate/vegetation could have influenced the dispersal of early humans through expansions and contractions of well-watered corridors.


Assuntos
Mudança Climática , Planeta Terra , Camada de Gelo , África , Animais , Clima , Simulação por Computador , Gases de Efeito Estufa , Hominidae , Humanos , Paleontologia , Plantas , Chuva , Estações do Ano
16.
PLoS One ; 15(1): e0227789, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31995815

RESUMO

100 Ma sweat bee nests reported herein are the oldest evidence of crown bees. A new phylogeny for short-tongued bees, calibrated with these nests dated with 40Ar/39Ar, attests for the first time for a late Albian rapid diversification of bees along with angiosperms. Such hypothesis lacked paleontological support until this study. The new ichnospecies Cellicalichnus krausei, which was found along with wasp trace fossils and new beetle trace fossils in the Castillo Formation of Patagonia, represents typical Halictini nests composed of sessile cells that are attached to main tunnels. According to geological, paleosol, paleobotanical, and ichnological data, bees, and angiosperms cohabited in an inland and dry environment comparable to an open dry woodland or savanna, under warm-temperate and semiarid-subhumid climate, in the Southern Hemisphere by the Albian.


Assuntos
Abelhas/fisiologia , Evolução Biológica , Magnoliopsida/fisiologia , Animais , Abelhas/anatomia & histologia , Abelhas/genética , Biodiversidade , Ecossistema , Fósseis/anatomia & histologia , Magnoliopsida/anatomia & histologia , Magnoliopsida/genética , Comportamento de Nidação , Paleontologia , Filogenia , Polinização
17.
Proc Natl Acad Sci U S A ; 117(3): 1612-1620, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31888998

RESUMO

The fin-to-limb transition was marked by the origin of digits and the loss of dermal fin rays. Paleontological research into this transformation has focused on the evolution of the endoskeleton, with little attention paid to fin ray structure and function. To address this knowledge gap, we study the dermal rays of the pectoral fins of 3 key tetrapodomorph taxa-Sauripterus taylori (Rhizodontida), Eusthenopteron foordi (Tristichopteridae), and Tiktaalik roseae (Elpistostegalia)-using computed tomography. These data show several trends in the lineage leading to digited forms, including the consolidation of fin rays (e.g., reduced segmentation and branching), reduction of the fin web, and unexpectedly, the evolution of asymmetry between dorsal and ventral hemitrichia. In Eusthenopteron, dorsal rays cover the preaxial endoskeleton slightly more than ventral rays. In Tiktaalik, dorsal rays fully cover the third and fourth mesomeres, while ventral rays are restricted distal to these elements, suggesting the presence of ventralized musculature at the fin tip analogous to a fleshy "palm." Asymmetry is also observed in cross-sectional areas of dorsal and ventral rays. Eusthenopteron dorsal rays are slightly larger than ventral rays; by contrast, Tiktaalik dorsal rays can be several times larger than ventral rays, and degree of asymmetry appears to be greater at larger sizes. Analysis of extant osteichthyans suggests that cross-sectional asymmetry in the dermal rays of paired fins is plesiomorphic to crown group osteichthyans. The evolution of dermal rays in crownward stem tetrapods reflects adaptation for a fin-supported elevated posture and resistance to substrate-based loading prior to the origin of digits.


Assuntos
Nadadeiras de Animais/anatomia & histologia , Extremidades/anatomia & histologia , Peixes/anatomia & histologia , Anfíbios , Nadadeiras de Animais/fisiologia , Animais , Evolução Biológica , Extremidades/fisiologia , Peixes/fisiologia , Fósseis , Paleontologia , Tomografia Computadorizada por Raios X
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