Bones of recent mammals in the Amboseli Basin, southern Kenya, exhibit distinctive weathering characteristics that can be related to the time since death and to the local conditions of temperature, humidity and soil chemistry. A categorization of weathering characteristics into six stages, recognizable on descriptive criteria, provides a basis for investigation of weathering rates and processes. The time necessary to achieve each successive weathering stage has been calibrated using known-age carcasses. Most bones decompose beyond recognition in 10 to 15 yr. Bones of animals under 100 kg and juveniles appear to weather more rapidly than bones of large animals or adults. Small-scale rather than widespread environmental factors seem to have greatest influence on weathering characteristics and rates. Bone weathering is potentially valuable as evidence for the period of time represented in recent or fossil bone assemblages, in- cluding those on archeological sites, and may also be an important tool in censusing populations of animals in modern ecosystems.

Taphonomic and Ecologic Information Form Bone Weathering

Fire is a major modifier of communities, but the evolutionary origins of its prevalent role in shaping current biomes are uncertain. Australia is among the most fire-prone continents, with most of the landmass occupied by the fire-dependent sclerophyll and savanna biomes. In contrast to biomes with similar climates in other continents, Australia has a tree flora dominated by a single genus, Eucalyptus, and related Myrtaceae. A unique mechanism in Myrtaceae for enduring and recovering from fire damage likely resulted in this dominance. Here, we find a conserved phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution, dating from 60 to 62 Ma, in the earliest Palaeogene. Thus, fire-dependent communities likely existed 50 million years earlier than previously thought. We predict that epicormic resprouting could make eucalypt forests and woodlands an excellent long-term carbon bank for reducing atmospheric CO2 compared with biomes with similar fire regimes in other continents.

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Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary

Anatomy of the Dicotyledons

The Solanaceae is a plant family of great economic importance. Despite a wealth of phylogenetic work on individual clades and a deep knowledge of particular cultivated species such as tomato and potato, a robust evolutionary framework with a dated molecular phylogeny for the family is still lacking. Here we investigate molecular divergence times for Solanaceae using a densely-sampled species-level phylogeny. We also review the fossil record of the family to derive robust calibration points, and estimate a chronogram using an uncorrelated relaxed molecular clock. Our densely-sampled phylogeny shows strong support for all previously identified clades of Solanaceae and strongly supported relationships between the major clades, particularly within Solanum. The Tomato clade is shown to be sister to section Petota, and the Regmandra clade is the first branching member of the Potato clade. The minimum age estimates for major splits within the family provided here correspond well with results from previous studies, indicating splits between tomato & potato around 8 Million years ago (Ma) with a 95% highest posterior density (HPD) 7–10 Ma, Solanum & Capsicum c. 19 Ma (95% HPD 17–21), and Solanum & Nicotiana c. 24 Ma (95% HPD 23–26). Our large time-calibrated phylogeny provides a significant step towards completing a fully sampled species-level phylogeny for Solanaceae, and provides age estimates for the whole family. The chronogram now includes 40% of known species and all but two monotypic genera, and is one of the best sampled angiosperm family phylogenies both in terms of taxon sampling and resolution published thus far. The increased resolution in the chronogram combined with the large increase in species sampling will provide much needed data for the examination of many biological questions using Solanaceae as a model system.

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A phylogenetic framework for evolutionary study of the nightshades (Solanaceae): a dated 1000-tip tree

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Global vegetation dynamics and latitudinal temperature gradients during the mid to Late Miocene (15.97-5.33 Ma)

A paleobotanical biozonation and a chronostratigraphic chart for the continental Triassic of Argentina are proposed. The biostratigraphic study was based on the multivariate analysis of 218 taxa distributed in 15 lithostratigraphic units and 134 taxa from 28 paleocommunities. The biostratigraphic analysis was also supported on the Permian or Jurassic lineage of several species, their acme, the temporal turnover and the evolution of the paleofloras. This information was evaluated together with the stratigraphic location of the fossiliferous horizons, the geochronologic information and the relationship between paleocommunities and sedimentary facies and environments. Five biozones were defined: 1. Dictvoptiullum castellanosii, [ohnsionia stcizneriana and Saportaea dichotoma Biozone (CSD), Represented by a mixed forest and identified in the Barreal and lschichuca Forrnations. 2. Yabeiella marefesiaca, Scytophylllll11 bonettiae and Protoptvflloctadoxvion cormderitacnsis Biozone (MBC). Mixed forests recognized in the Potrerillos, Cortaderita (lower section) and El Alcazar Formations. 3. Ynbeiella brackebuschiana, Scytophylllll11 neuburgianum and Rhexoxvlon piatnitzkui Biozone (BNP). Mixed forests, identified in the Vera, Potrerillos and Ischigualasto Formations, and in the El Tranquilo Group. 4. Dicroidium odontopteroides and D. lancijolium Biozone (OL). Represented by a herbaceous and shrub-like paleocornmunity, defined in the Cacheuta Formation and in the upper section of the Cortaderita Formation. 5. Dictyop/iylllll11 tenuiserraium, Linguijoliuni arctum and Protocircoporoxylon nuirionoensis Biozone (DLM). Deciduous and mesoxerophytic forests, identified in the Los Colorados and Rio Blanco redbeds, the Paso Flores Formation and the Tronquimalal Group. The following local stages are defined on the bases of biozone chronology, analysis of the main stratigraphic unconformities and evolution of the basin infill: Barrealian (Early to Middle Triassic), Cortaritian (late Middle to early Late Triassic) and Flarian (upper Late Triassic).

Biozonación paleoflorística y cronoestratigrafía del Triásico argentino

Fil: Barreda, Viviana Dora. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

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Diversificación y cambios de las angiospermas durante el Neógeno en Argentina

The Paleocene-Eocene boundary was a period of transient and intense global warming that had a deep effect on middle and high latitude plant groups. Nevertheless, only scarce early Paleogene paleoclimatic records are known from the South American continental sequences deposited at these latitudes. In this contribution clay mineralogy and paleobotanical analyses (fossil woods and phytoliths) were used as paleoclimate proxies from the lower and middle parts of the Rio Chico Group (Golfo San Jorge basin, Patagonia, Argentina). These new data may enable to understand the changing climatic conditions during part of the Paleocene-Eocene transition. In this setting, three clay mineral assemblages were identified: S1 assemblage (smectite) dominates the Penas Coloradas Formation; S2 assemblage (smectitegt;kaolinite) occurs in the stratigraphic transition to the Las Flores Formation; and S3 assemblage (kaolinitegt;smectite) dominates the Las Flores Formation. These trend of change in the detrital clay mineral composition is interpreted as resulting mainly from the changing paleoclimatic conditions that shifted from seasonal warm temperate to tropical affecting the same source area lithology. Moreover, the paleobotanical data suggest that the Early Paleogene vegetation in the Golfo San Jorge basin underwent significant composition and diversity changes, ranging from mixed temperate - subtropical forest to mixed subtropical - tropical, humid forest. The integrated analysis of the clay mineral composition and the palaeobotanical assemblages suggests that, in central Argentinean Patagonia, the Paleocene-Eocene climate changed from temperate warm, humid and highly seasonal precipitation conditions to subtropical-tropical, more continuous year-round rainfall conditions.

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Early Paleogene climate at mid latitude in South America: Mineralogical and paleobotanical proxies from continental sequences in Golfo San Jorge basin (Patagonia, Argentina)

Mariana Brea

Papers

Biozonación paleoflorística y cronoestratigrafía del Triásico argentino

Diversificación y cambios de las angiospermas durante el Neógeno en Argentina

Early Paleogene climate at mid latitude in South America: Mineralogical and paleobotanical proxies from continental sequences in Golfo San Jorge basin (Patagonia, Argentina)

First record of fossil wood and phytolith assemblages of the Late Pleistocene in El Palmar National Park (Argentina)

Four. The Paraná-Paraguay Basin: Geology and Paleoenvironments