BACKGROUND AND AIMS Worldwide, many plant species are confined to open, shallow-soil, rocky habitats. Although several hypotheses have been proposed to explain this habitat specificity, none has been convincing. We suggest that the high level of endemism on shallow soils is related to the edaphic specialization needed to survive in these often extremely drought-prone habitats. Previous research...

The soil resources of Sierra Leone remain an integral part sustainable agricultural development but knowledge the suitability soils and their management requirements for a variety land uses is still lacking to greater extent. In this view, detailed survey three chiefdoms in Northern was undertaken evaluate genesis interpret soil-landscape properties relationships using toposequence free style a...

In previous investigations, nearshore pyritic shale horizons in the Mid-Proterozoic Newland Formation were interpreted to be due to "non-clastic" colloidal iron supply by streams. New data on the chemical composition of shales in the Newland Formation support this interpretation. In these shales, Fe and Al show a positively correlated trend that intercepts the Fe axis above the origin. These re...

Comparative anatomists since the time of Richard Owen (1) have observed that birds and crocodilians have a four-chambered heart and have speculated that such a heart was present in extinct archosaurs as well. Until recently, no direct evidence of the cardiovascular system had been reported in any archosaur fossil. Fisher et al. (2), however, using computerized tomography (CT) scanning, reported...