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Pan A.D.,Fort Worth Museum of Science and History | Jacobs B.F.,Southern Methodist University | Herendeen P.S.,Chicago Botanic Garden
Botanical Journal of the Linnean Society | Year: 2010

New species of caesalpinioid legumes, Cynometra sensu lato and Afzelia, are described from the Late Oligocene (27.23 Ma) Guang River flora in north-western Ethiopia. Both taxa show leaf characteristics that are shared with extant species in the Guineo-Congolian, Sudanian and/or Zambezian regions of Africa today. The presence of these two species in Ethiopia during the Palaeogene provides further evidence of the importance of the legume tribe Detarieae in northern and north-eastern Africa throughout much of the Cenozoic, even although the clade is poorly represented in these regions today. The fossil record documents a significant palaeogeographical and evolutionary history of Detarieae in Africa, especially compared with that of Europe and Anatolia. Based on this evidence, it is unlikely that significant diversification of extant African Detarieae took place on the Eurasian landmass. © 2010 The Linnean Society of London.

Pan A.D.,Fort Worth Museum of Science and History
Review of Palaeobotany and Palynology | Year: 2010

Fossil leaf compressions from the Late Oligocene (27.23 Ma) Guang River flora of northwestern Ethiopia include a new record of Vepris and the earliest record of Clausena and the subfamily Aurantioideae. These fossils, along with most other African rutaceous fossils, are associated with a tropical moist forest community. The large number of Rutaceae taxa in eastern Africa during the Late Oligocene and Early Miocene is likely due to a radiation within Africa or dispersal to Africa associated with the continental expansion of moist tropical forest during this time interval. © 2009 Elsevier B.V. All rights reserved.

Pan A.D.,Fort Worth Museum of Science and History | Pan A.D.,Botanical Research Institute of Texas | Pan A.D.,Don Harrington Discovery Center | Currano E.D.,Miami University Ohio | And 4 more authors.
International Journal of Plant Sciences | Year: 2012

Numerous fossil winged seeds from the early Miocene (22-21 MA) of Ethiopia represent the earliest and only definitive record of the ecologically and economically important legume genus Newtonia (Fabaceae: ''Mimoseae''). These fossils represent a new species and provide evidence that tropical moist forest persisted on the Ethiopian Plateau into the early Miocene. © 2012 by The University of Chicago.

Currano E.D.,Miami University Ohio | Jacobs B.F.,Southern Methodist University | Pan A.D.,Fort Worth Museum of Science and History | Tabor N.J.,Southern Methodist University
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

Environmental disturbances profoundly impact the structure, composition, and diversity of modern forest communities. A review of modern studies demonstrates that important characteristics used to describe fossil angiosperm assemblages, including leaf margin type, plant form, plant diversity, insect herbivore diversity and specialization, and variation in herbivory among plant species, differ between early and late successional forests. Therefore, sequences of fossil floras that include a mix of early and later successional communities may not be appropriate to study long-term temporal trends or biotic effects of climate, latitude, or other variables.We conducted sedimentological, paleobotanical, and insect damage analyses at two contemporaneous late Oligocene (27-28. Ma) leaf localities in the Chilga Basin, northwest Ethiopia, to test the hypothesis that successional stage explains variation between the assemblages. The Guang River and Bull's Bellow fossil plant localities are stratigraphically equivalent and only 1.5. km apart, but they have no plant species in common. Sedimentary structures at Bull's Bellow suggest multiple episodes of deposition and a more disturbed environment than the single, featureless mudstone that composes the Guang River fossil unit. Bull's Bellow has a significantly higher percentage of plant species with toothed margins, lower plant and insect herbivore damage diversity, and less specialized herbivore damage than Guang. Furthermore, the nearest living relatives of many of the Bull's Bellow plant species are associated with early successional forests, whereas the Guang River plants are a mix of early and late successional species. Thus, the physiological and ecological attributes of the Guang flora are consistent with a more mature forest community, and the differences between the two floras emphasize the importance of collecting multiple floras from the same stratigraphic level in order to account for landscape-level ecological processes. More specifically, accurate estimates of diversity and feeding specialization in tropical, angiosperm-rich fossil assemblages are essential to address adequately the origin and persistence of relatively high species diversity in the modern tropics, and diversity differences between regions such as modern tropical Africa and South America. © 2011 Elsevier B.V.

Agency: NSF | Branch: Standard Grant | Program: | Phase: SEDIMENTARY GEO & PALEOBIOLOGY | Award Amount: 42.49K | Year: 2011

Project Abstract
Collaborative Research: A multi-proxy approach to Early Miocene community, landscape, and climate reconstruction, Ethiopian Plateau
Technical Description: The Cenozoic rock record contains a rich and critically important history of varied climates and biotic communities, and these serve as aids to understanding current and future climatic and biotic change. While the scales are different, the deep geologic past provides test cases against which climate models can be compared or from which they can be created. However, spatial coverage by paleoclimate proxies is best for middle latitudes, and quite limited for the tropics and subtropics, especially in the terrestrial realm. This project will investigate a new extraordinary Early Miocene (22 Ma) site where carbonaceous shales and tuffaceous sediments preserve lagerstätten-quality fossils including abundant compressed leaves, fruits and seeds with exquisite cuticular features, complete frogs with both skeletal and soft body parts, fish and large mammal bones. These enable reconstruction of paleoclimate, pCO2, paleoecology, and significant biogeographic data for African flora, and perhaps fauna. The objectives of this project are to:
1. compare Early Miocene and Late Oligocene paleoclimate, paleoecology, and biogeography using multiple independent proxies.
2. provide pCO2 estimates from pedogenic goethite and stomatal indices.
3. provide Early Miocene paleoecological and paleoclimatological context for faunal evolution during an otherwise poorly known, but significant time interval for Africa.
4. address plant biogeographic questions, e.g. a decline in palm richness and importance
5. test methods by (a) comparing δD isotopes from aquatic and terrestrial lipids to test for enrichment of D due to evapotranspiration, (b) comparing goethite and stomatal index pCO2 data (c) evaluating the consistency of paleotemperature and precipitation reconstructions using methods based upon leaf physiognomy, overlapping ranges of plant taxa, qualitative and quantitative paleosol analyses, and multiple isotope geochemical proxies.
Non-technical Description and Broader Significance: This grant funds a multidisciplinary team of scientists who will sample rocks and fossils from the Ethiopian Plateau northeast of Addis Ababa to reconstruct past climate, vegetation, atmospheric CO2 concentration (pCO2), and the physical landscape 22 million years ago in an integrated and collaborative way. Team members, who have collaborated before on rocks from the Plateau that are 27 million years old, have expertise in the study of plant fossil identification, insect damage to fossil leaves, the reconstruction of past climate and ecology, the geochemistry of ancient soils and organic plant compounds, and geology. The locality preserves extraordinary plant fossils having cellular detail, smaller vertebrates including frogs with soft tissue preservation, and large mammal bones. The scientific significance of our work is that it will resolve currently conflicting data regarding global temperature and pCO2 between 27 million and 22 million years ago. Marine records show a significant rise in global temperature between these times, but some records of pCO2 show a decline and others a rise. Resolution of this conflict by acquisition of temperature and pCO2 data from one region using multiple independent sources will tell us if our understanding of CO2, in relation to global temperature is correct. Furthermore, the modern land connection between Africa and Eurasia was established about 24 million years ago, so we will be able to compare the younger plant and animal fossils with those from a time prior to contact with Eurasia. Africa?s flora and fauna was in a period of transition at this time, and its documentation is important for understanding the origins of modern biomes.
Educational outreach includes distance learning for thousands of K-12 students. This team has a history of blogs, currently hosted by the SMU Public Affairs office on the main website, and recently through the NY Times Scientist at Work pages. Students will be an integral part of this project ? this team has regularly taken students into the field and will continue to do so. We also plan to host an Ethiopian graduate student for training in the U.S.

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