نتایج جستجو برای: fossil

تعداد نتایج: 25461  

Journal: :Current opinion in microbiology 2003
Kevin A Gray Gregory T Mrachko Charles H Squires

Biotechnological techniques enabling the specific removal of sulfur from fossil fuels have been developed. In the past three years there have been important advances in the elucidation of the mechanisms of biodesulfurization; some of the most significant relate to the role of a flavin reductase, DszD, in the enzymology of desulfurization, and to the use of new tools that enable enzyme enhanceme...

Journal: :Zootaxa 2015
Andris Bukejs Vitalii I Alekseev

Based on a well-preserved specimen from Upper Eocene Baltic amber (Kaliningrad region, Russia), Microbregma waldwico sp. nov., the second fossil species of this genus, is described. The new species is similar to the extant Holarctic M. emarginatum (Duftschmid), 1825, and fossil M. sucinoemarginatum (Kuśka), 1992, but differs in its shorter abdominal ventrite 1 (about 0.43 length of ventrite 2) ...

Journal: :Science 1999
M Foote J P Hunter C M Janis J J Sepkoski

Some molecular clock estimates of divergence times of taxonomic groups undergoing evolutionary radiation are much older than the groups' first observed fossil record. Mathematical models of branching evolution are used to estimate the maximal rate of fossil preservation consistent with a postulated missing history, given the sum of species durations implied by early origins under a range of spe...

Journal: :Systematic biology 1999
F Lutzoni F K Barker

of randomly distributed fossil horizons. Paleobiology 20:459–469. MAXWELL, W. D., AND M. J. BENTON. 1990. Historical tests of the absolute completeness of the fossil record of tetrapods. Paleobiology 16:322–335. NORELL, M. A., AND M. J. NOVACEK. 1992a. Congruence between superpositional and phylogenetic patterns: Comparing cladistic patterns with fossil records. Cladistics 8:319–337. NORELL, M....

2013
Michael D. Nowak Andrew B. Smith Carl Simpson Derrick J. Zwickl

Molecular divergence time analyses often rely on the age of fossil lineages to calibrate node age estimates. Most divergence time analyses are now performed in a Bayesian framework, where fossil calibrations are incorporated as parametric prior probabilities on node ages. It is widely accepted that an ideal parameterization of such node age prior probabilities should be based on a comprehensive...

2015
Marcel van Tuinen Christopher R. Torres

Uncertainty in divergence time estimation is frequently studied from many angles but rarely from the perspective of phylogenetic node age. If appropriate molecular models and fossil priors are used, a multi-locus, partitioned analysis is expected to equally minimize error in accuracy and precision across all nodes of a given phylogeny. In contrast, if available models fail to completely account...

2015
Michael J. Landis

15 Standard models of molecular evolution cannot estimate absolute speciation times alone, 16 and require external calibrations to do so. Because fossil calibration methods rely on the 17 unreliable fossil record, most nodes in the tree of life are dated with poor accuracy. However, 18 many major paleogeographical events are dated, and since biogeographic processes depend 19 on paleogeographica...

2008
Claudia L. Mendes de Oliveira Eleazar R. Carrasco

It has been suggested that fossil groups could be the canibalized remains of compact groups, that lost energy through tidal friction. However, in the nearby universe, compact groups which are close to the merging phase and display a wealth of interacting features (such as HCG 31 and HCG 79) have very low velocity dispersions and poor neighborhoods, unlike the massive, cluster-like fossil groups...

Journal: :Systematic biology 2017
Michael J Landis

Standard models of molecular evolution cannot estimate absolute speciation times alone, and require external calibrations to do so, such as fossils. Because fossil calibration methods rely on the incomplete fossil record, a great number of nodes in the tree of life cannot be dated precisely. However, many major paleogeographical events are dated, and since biogeographic processes depend on pale...

2014
Alexei P. iPPolitov olev vinn elenA K. KuPriyAnovA MAnfred Jäger

Ippolitov, A.P., Vinn, O., Kupriyanova, E.K. and Jäger, M. 2014. Written in stone: history of serpulid polychaetes through time. Memoirs of Museum Victoria 71: 123–159. Although the fossil record of annelids in general is poor, calcareous tube-building Serpulidae are a notable exception. The “stumbling block” of understanding the serpulid fossil record is obtaining reliable taxonomic interpreta...

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