Hasil untuk "Paleontology"

M. Kohn

L. Parfrey, Daniel J. G. Lahr, Andrew H. Knoll et al.

L. W. Alvarez, W. Álvarez, F. Asaro et al.

M. Mckenna, S. K. Bell, G. Simpson

R. Ricklefs

E. Davidson, D. Erwin

S. Gould, N. Eldredge

W. Fitch, F. Ayala

L. Sagan

G. Kukla

M. Mckinney

M. Benton, P. Donoghue

M. Sabaj

Assembled here is a reasonably complete list of annotated codes for historical and modern natural history collections associated with lost and extant specimens of fossil and Recent fishes, amphibians, and reptiles. A total of 3,845 codes are anchored to about 2,064 distinct collections and/or institutions in 155 countries. At least 633 of those collections are exclusively paleontological or include fossil specimens. The list is primarily derived from the scientific literature and may serve as a resource for plainly citing specimens in publications and for linking such citations to records in online databases.

James, F., Parham et al.

Our ability to correlate biological evolution with climate change, geological evolution, and other historical patterns is essential to understanding the processes that shape biodiversity. Combining data from the fossil record with molecular phylogenetics represents an exciting synthetic approach to this challenge. The first molecular divergence dating analysis (Zuckerkandl and Pauling 1962) was based on a measure of the amino acid differences in the hemoglobin molecule, with replacement rates established (calibrated) using paleontological age estimates from textbooks (e.g., Dodson 1960). Since that time, the amount of molecular sequence data has increased dramatically, affording ever-greater opportunities to apply molecular divergence approaches to fundamental problems in evolutionary biology. To capitalize on these opportunities, increasingly sophisticated divergence dating methods have been, and continue to be, developed. In contrast, comparatively, little attention has been devoted to critically assessing the paleontological and associated geological data used in divergence dating analyses. The lack of rigorous protocols for assigning calibrations based on fossils raises serious questions about the credibility of divergence dating results (e.g., Shaul and Graur 2002; Brochu et al. 2004; Graur and Martin 2004; Hedges and Kumar 2004; Reisz and Muller 2004a, 2004b; Theodor 2004; van Tuinen and Hadly 2004a, 2004b; van Tuinen et al. 2004; Benton and Donoghue 2007; Donoghue and Benton 2007; Parham and Irmis 2008; Ksepka 2009; Benton et al. 2009; Heads 2011). The assertion that incorrect calibrations will negatively influence divergence dating studies is not controversial. Attempts to identify incorrect calibrations through the use of a posteriori methods are available (e.g., Near and Sanderson 2004; Near et al. 2005; Rutschmann et al. 2007; Marshall 2008; Pyron 2010; Dornburg et al. 2011). We do not deny that a posteriori methods are a useful means of evaluating calibrations, but there can be no substitute for a priori assessment of the veracity of paleontological data. Incorrect calibrations, those based upon fossils that are phylogenetically misplaced or assigned incorrect ages, clearly introduce error into an analysis. Consequently, thorough and explicit justification of both phylogenetic and chronologic age assessments is necessary for all fossils used for calibration. Such explicit justifications will help to ensure that divergence dating studies are based on the best available data. Unfortunately, the majority of previously published calibrations lack explicit explanations and justifications of the age and phylogenetic position of the key fossils. In the absence of explicit justifications, it is difficult to distinguish between correct and incorrect calibrations, and it becomes difficult to reevaluate previous claims in light of new data. Paleontology is a dynamic science, with new data and perspectives constantly emerging as a result of new discoveries (see Kimura 2010 for a recent case where the age of the earliest known record of a clade was more than doubled). Calibrations based upon the best available evidence at a given time can become inappropriate as the discovery of new specimens, new phylogenetic analyses, and ongoing stratigraphic and geochronologic revisions refine our understanding of the fossil record. Our primary goals in this paper are to establish the best practices for justifying fossils used for the temporal calibration of molecular phylogenies. Our examples derive mainly, but not exclusively, from the vertebrate fossil record. We hope that our recommendations will lead to more credible calibrations and, as a result, more reliable divergence dates throughout the tree of life. A secondary goal is to help the community (researchers, editors, and reviewers) who might be unfamiliar with fossils to understand and overcome the challenges associated with using paleontological data. In order to accomplish these goals, we present a specimen-based protocol for selecting and documenting relevant fossils and discuss future directions for evaluating and utilizing phylogenetic and temporal data from the fossil record. We likewise encourage biologists relying on nonfossil calibrations for molecular divergence estimates (e.g., ages of island or mountain range formations, continental drift, and biomarkers) to develop their own set of rigorous guidelines so that their calibrations may also be evaluated in a systematic way.

T. Morelli, C. Daly, S. Dobrowski et al.

Refugia have long been studied from paleontological and biogeographical perspectives to understand how populations persisted during past periods of unfavorable climate. Recently, researchers have applied the idea to contemporary landscapes to identify climate change refugia, here defined as areas relatively buffered from contemporary climate change over time that enable persistence of valued physical, ecological, and socio-cultural resources. We differentiate historical and contemporary views, and characterize physical and ecological processes that create and maintain climate change refugia. We then delineate how refugia can fit into existing decision support frameworks for climate adaptation and describe seven steps for managing them. Finally, we identify challenges and opportunities for operationalizing the concept of climate change refugia. Managing climate change refugia can be an important option for conservation in the face of ongoing climate change.

D. Grimaldi, M. Engel, Paul c. Nascimbene

Abstract Amber from Kachin, northern Burma, has been used in China for at least a millennium for carving decorative objects, but the only scientific collection of inclusion fossils, at the Natural History Museum, London (NHML), was made approximately 90 years ago. Age of the material was ambiguous, but probably Cretaceous. Numerous new records and taxa occur in this amber, based on newly excavated material in the American Museum of Natural History (AMNH) containing 3100 organisms. Without having all groups studied, significant new records and taxa thus far include the following (a † refers to extinct taxa): For Plants: An angiosperm flower (only the third in Cretaceous amber), spores and apparent sporangia of an unusual but common fungus, hepatophyte thalli and an archegoniophore of Marchantiaceae, and leafy shoots of Metasequoia (Coniferae). Metasequoia is possibly the source of the amber. For Animals: Mermithidae and other Nematoda; the oldest ixodid tick (a larval Amblyomma); bird feathers; and the only Mesozoic record of the Onychophora (“velvet” worms), described as †Cretoperipatus burmiticus, n. gen., n. sp. (Peripatidae). Poinar's classification of the Onychophora is substantially revised. Still largely unstudied, the fauna of mites (Acari) and spiders (Araneae) appears to be the most diverse ones known for the Mesozoic. For Insecta: Odonata indet. (wing fragment); Plecoptera indet.; new genera of Dermaptera, Embiidina, and Zoraptera (the latter two as the only definitive Mesozoic fossils of their orders). Within Hemiptera, there are primitive new genera in the Aradidae, Hydrometridae, Piesmatidae, Schizopteridae, and Cimicomorpha (Heteroptera), as well as in †Tajmyraphididae (Aphidoidea), and †′otopsyllidiidae. An adult snakefly (Raphidioptera: †Mesoraphidiidae) is the smallest species in the order, and new genera occur in the Neuroptera: Coniopterygidae, Berothidae, and Psychopsidae, as well as larvae of apparent Nevrorthidae. Coleoptera are largely unstudied, but are probably the most diverse assemblage known from the Cretaceous, particularly for Staphylinidae. An adult lymexylid, the most primitive species of Atractocerus, is the first Mesozoic record of the family. In Hymenoptera there are primitive ants (Formicidae: Ponerinae n. gen., and †Sphecomyrma n.sp [Sphecomyrminae]), the oldest record of the Pompilidae, and significant new records of †Serphitidae and †Stigmaphronidae, among others. Diptera are the most diverse and abundant, with the oldest definitive Blephariceridae and mosquito (Culicidae), as well as new genera in the Acroceridae, Bibionidae, Empidoidea; a new genus near the enigmatic genus Valeseguya, and an unusual new genus in the †Archizelmiridae. †Chimeromyia (Diptera: Eremoneura), known previously in ambers from the Lower Cretaceous, is also represented. The stratigraphic distribution of exclusively Mesozoic arthropods in Burmese amber is reviewed, which indicates a probable Turonian-Cenomanian age of this material (90–100 Ma). Paleofaunal differences between the NHML and AMNH collections are discussed, as is the distinct tropical nature of the original biota. Burmese amber probably harbors the most diverse biota in amber from the Cretaceous, and one of the most diverse Mesozoic microbiotas now known.

W. Johnson, E. Eizirik, J. Pecon-Slattery et al.

R. Raiswell, D. Hardisty, T. Lyons et al.

Cong Wu, Fang Chen, Ying Tian et al.

The genus Provanna (belonging to Superfamily Abyssochrysoidea) is a group of globally distributed gastropods commonly discovered in the deep-sea chemosynthetic environments. To date it is composed of 29 extant and nine fossil species and all of them seem to be endemic to vents, seeps or organic falls. Despite the increasing interest in cold seeps in South China Sea in recent decades, how this genus is distributed in this area is largely unknown. A new fossil species, Provanna dongshaensis sp. nov., collected from the hydrate-bearing sediments in the cold seep area of northern SCS, was studied. A basic morphological description together with the observation of shell microstructures was made, and a brief comparison to known Provanna species was summarized. The occurrence depths of this new species are consistent with the remarkable negative carbon isotope of carbonate layers, which mutually supports the relationship to the ancient seep. Such sedimentary samples from drilling cores may be potentially better materials for systematic research of deep-sea gastropods and other chemosynthesis fauna.

T. J. Pollard, J. D. Woodhead, R. N. Drysdale et al.

<p>The U–Th and U–Pb dating methods are widely employed for radiometric dating of Pleistocene carbonates, such as speleothems and corals. The U–Th dating method has been progressively refined over recent decades, largely through advances in mass spectrometry, and is now capable of providing accurate and precise ages for carbonates as old as <span class="inline-formula">∼</span> 650 000 years under optimal circumstances. Similarly, the U–Pb method, traditionally restricted to dating pre-Quaternary materials, has been adapted in recent years for dating young carbonates. As a result, there is now substantial overlap in the applicable age range of these two dating methods but, thus far, only limited assessment of their consistency and relative performance when dating samples over this shared age interval.</p> <p>In this study, we conduct a systematic comparison of the U–Th and U–Pb dating methods, focusing on a significant part of their overlapping age range (approximately 630–430 ka). We achieve this by dating speleothem (secondary cave mineral deposit) samples from Corchia Cave, central Italy, using both methods and evaluate their consistency and performance in terms of age precision and other factors. We adopt analytical approaches that employ state-of-the-art multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) measurement protocols, including a U–Th measurement protocol that utilises a Faraday cup equipped with a <span class="inline-formula">10¹³</span> <span class="inline-formula">Ω</span> resistor to collect the low-abundance <span class="inline-formula">²³⁴U⁺</span> and <span class="inline-formula">²³⁰Th⁺</span> ion beams. This approach is particularly well-suited to dating samples approaching the limits of the U–Th method but also enables accurate determination of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi/><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi><msup><mo>/</mo><mn mathvariant="normal">235</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="62b133e2ddbd9f6ca36fd78db1302347"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-7-335-2025-ie00001.svg" width="52pt" height="15pt" src="gchron-7-335-2025-ie00001.png"/></svg:svg></span></span> ratios. Thus, as a secondary component of this study, we compare our <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi/><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi><msup><mo>/</mo><mn mathvariant="normal">235</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="81e267774a2569df45cc421336a6df91"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-7-335-2025-ie00002.svg" width="52pt" height="15pt" src="gchron-7-335-2025-ie00002.png"/></svg:svg></span></span> measurements with previously published speleothem values.</p> <p>Our results demonstrate excellent agreement between the U–Th and U–Pb dating methods and suggest that both are capable of providing accurate and precise ages over this interval. We find that U–Pb age uncertainties are generally less predictable than U–Th age uncertainties but, on average, do not increase significantly over the interval considered. U–Th age uncertainties, on the other hand, tend to increase in a more predictable and approximately exponential manner. Additionally, U–Pb age uncertainties are highly dependent on the availability of sub-samples with a substantial spread<span id="page336"/> in parent/daughter ratios and/or highly “radiogenic” (i.e. very low inherited Pb) material. In our dataset, U–Pb isochron age precision surpasses that of U–Th precision at <span class="inline-formula">∼</span> 520 ka, although the exact crossover point is expected to vary for different sample types and depositional settings. Overall, these findings support the prospect of obtaining accurate and internally consistent U-series chronologies spanning the Middle Pleistocene. They also suggest that, for some carbonate samples, the U–Pb dating method may provide superior age precision to the U–Th method prior to the latter reaching its upper age limit.</p> <p>Finally, our results show that most speleothems exhibit <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi/><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi><msup><mo>/</mo><mn mathvariant="normal">235</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="799dcbfa9bb5158a64ae5406e891656e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-7-335-2025-ie00003.svg" width="52pt" height="15pt" src="gchron-7-335-2025-ie00003.png"/></svg:svg></span></span> ratios consistent with global carbonate values and that these ratios typically deviate from the conventional value of 137.88, widely adopted in geochronology, in agreement with previous studies.</p>