The fossil record of early tetrapods: worker effort and the end-Permian mass extinction

It is important to understand the quality of the fossil record of early tetrapods (Tetrapoda, minus Lissamphibia and Amniota) because of their key role in the transition of vertebrates from water to land, their dominance of terrestrial faunas for over 100 million years of the late Palaeozoic and earlyMesozoic, and their variable fates during the end−Permian mass extinction. The first description of an early tetrapod dates back to 1824, and since then discoveries have occurred at a rather irregular pace, with peaks and troughs corresponding to some of the vicissitudes of human history through the past two centuries. As expected, the record is dominated by the well−sampled sedimentary basins of Europe and North America, but finds from other continents are increasing rapidly. Comparisons of snapshots of knowledge in 1900, 1950, and 2000 show that discovery of new species has changed the shape of the species−level diversification curve, contrary to earlier studies of family−level taxa. There is, however, little evidence that taxon counts relate to research effort (as counted by numbers of publications), and there are no biasing effects associated with differential study of different time intervals through the late Palaeozoic and Mesozoic. In fact, levels of effort are apparently not related to geological time, with no evidence that workers have spent more time on more recent parts of the record. In particular, the end−Permian mass extinction was investigated to determine whether diversity changes through that interval might reflect worker effort: it turns out that most records of early tetrapod taxa (when corrected for duration of geological series) occur in the Lower Triassic

Red Queen Coevolution on Fitness Landscapes

Species do not merely evolve, they also coevolve with other organisms. Coevolution is a major force driving interacting species to continuously evolve ex- ploring their fitness landscapes. Coevolution involves the coupling of species fit- ness landscapes, linking species genetic changes with their inter-specific ecological interactions. Here we first introduce the Red Queen hypothesis of evolution com- menting on some theoretical aspects and empirical evidences. As an introduction to the fitness landscape concept, we review key issues on evolution on simple and rugged fitness landscapes. Then we present key modeling examples of coevolution on different fitness landscapes at different scales, from RNA viruses to complex ecosystems and macroevolution.Comment: 40 pages, 12 figures. To appear in "Recent Advances in the Theory and Application of Fitness Landscapes" (H. Richter and A. Engelbrecht, eds.). Springer Series in Emergence, Complexity, and Computation, 201

The taxonomy and anatomy of rauisuchian archosaurs from the Late Triassic of Germany and Poland

The German Late Triassic archosaur Teratosaurus suevicus is a historically important taxon, being the first described rauisuchian. Unfortunately the holotype is a single element, a maxilla, which is poorly preserved and incomplete. We redescribe this maxilla and identify a single potential autapomorphy. The fragmentary type specimen complicates attempts to refer additional material to this taxon, and other unassociated archosaur and rauisuchian specimens from the Mittlerer Stubensandstein of Germany cannot be referred to T. suevicus with any degree of confidence. The stratigraphically older T. silesiacus, from the upper Carnian of Poland, is represented by a much more complete and better preserved specimen. Comparison of the maxillae of T. suevicus and T. silesiacus reveals that the two are distinct taxa, contra recent suggestions, but also that they do not share any synapomorphies or a unique combination of characters relative to Postosuchus kirkpatricki and other rauisuchians. Thus, the Polish material must be transferred to a new genus, Polonosuchus gen. nov. Both Polonosuchus and Teratosaurus are very similar to Postosuchus kirkpatricki, and the three taxa are likely closely related

Internal representations of smell in the Drosophila brain

Recent advances in sensory neuroscience using Drosophila olfaction as a model system have revealed brain maps representing the external world. Once we understand how the brain's built-in capability generates the internal olfactory maps, we can then elaborate how the brain computes and makes decision to elicit complex behaviors. Here, we review current progress in mapping Drosophila olfactory circuits and discuss their relationships with innate olfactory behaviors

Structure and chromosomal location of the bovine gene for the heart muscle isoform of cytochrome c oxidase subunit VIII

We have isolated the bovine COX8H gene for the heart/muscle isoform of cytochrome c oxidase (COX) subunit VIII from a library of bovine genomic DNA cloned into lambda EMBL3. Primer extension assays on bovine heart mRNA mapped the 5′ ends of COX8H transcripts to a CA dinucleotide 62-bp upstream from the ATG codon. The gene thus spans 1565-bp and comprises two exons and one large intron of 1227 bp. Exon 1 encodes the 5′ untranslated region, a 24-amino acid presequence, and the first 13 amino acids of the mature COX VIII-H protein. Exon 2 encodes the remainder of the cDNA: amino acids 14 to 46 plus the 66-bp 3′ untranslated region. The exon-intron boundaries matched the consensus splice junction sequences. Two protein polymorphisms were seen: an Ala/Val polymorphism at position-6 in the presequence and the previously noted Lys/Arg polymorphism at residue 7 of the mature protein. A Taq I polymorphism occurs in the intron. The COX8H gene was mapped by bovine x rodent somatic cell hybrid mapping panels to bovine (BTA) Chromosome (Chr) 25 with 100% concordancy. BTA25 is conserved relative to the long arm of human (HSA) Chr 11, which contains COX8, the gene for the single human COX VIII subunit that is homologous to the liver isoform.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47018/1/335_2004_Article_BF00303255.pd

Observation of X(3872) production in pp collisions at √s=7TeV

Using 34.7 pb−1 of data collected with the LHCb detector, the inclusive production of the X(3872) meson in pp collisions at √s = 7 TeV is observed for the first time. Candidates are selected in the X(3872)→J/ψπ+π− decay mode, and used to measure σ(pp→X(3872)+anything)B(X(3872)→J/ψπ+π−) = 5.4 ±1.3 (stat)±0.8 (syst) nb, where σ(pp →X(3872) + anything) is the inclusive production cross section of X(3872) mesons with rapidity in the range 2.5–4.5 and transverse momentum in the range 5–20 GeV/c. In addition the masses of both the X(3872) and ψ(2S) mesons, reconstructed in the J/ψπ+π− final state, are measured to be mX(3872) = 3871.95± 0.48 (stat)±0.12 (syst) MeV/c2 and mψ(2S) = 3686.12±0.06 (stat) ±0.10 (syst) MeV/c2

Characterization of ribosomal DNA (rDNA) in Drosophila arizonae

Ribosomal DNA (rDNA) is a multigenic family composed of one or more clusters of repeating units (RU). Each unit consists of highly conserved sequences codifying 18S, 5.8S and 28S rRNA genes intercalated with poorly conserved regulatory sequences between species. In this work, we analyzed the rDNA of Drosophila arizonae, a member of the mulleri complex (Repleta group). Using genomic restriction patterns, cloning and mapping of some representative rDNA fragments, we were able to construct a representative restriction map. RU in this species are 13.5-14 kb long, restriction sites are completely conserved compared with other drosophilids and the rDNA has an R1 retrotransposable element in some RU. We were unable to detect R2 elements in this species.<br>O DNA ribossômico (rDNA) é uma família multigênica composta de um ou mais aglomerados de unidades de repetição (RU). Cada unidade consiste de seqüências altamente conservadas que codificam os rRNAs 18S, 5.8S e 28S, intercaladas com seqüências regulatórias pouco conservadas entre as espécies. Neste trabalho analisamos o rDNA de Drosophila arizonae, um membro do complexo mulleri (grupo Repleta). Usando padrões de restrição genômicos, clonagem e mapeamento de alguns fragmentos de rDNA representativos, estabelecemos um mapa de restrição do rDNA representativo desta espécie. Neste drosofilídeo, a RU tem um tamanho médio de 13.5-14 kb e os sítios de restrição estão completamente conservados com relação a outras drosófilas. Além disto, este rDNA possui um elemento transponível tipo R1 presente em algumas unidades. Neste trabalho não tivemos evidências da presença de elementos R2 no rDNA desta espécie