A Technique for developing fossils from the matrix in which they are embended

Volume: XXII

Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective

Widespread fish clades that occur mainly or exclusively in fresh water represent a key target of biogeographical investigation due to limited potential for crossing marine barriers. Timescales for the origin and diversification of these groups are crucial tests of vicariant scenarios in which continental break‐ups shaped modern geographic distributions. Evolutionary chronologies are commonly estimated through node‐based palaeontological calibration of molecular phylogenies, but this approach ignores most of the temporal information encoded in the known fossil record of a given taxon. Here, we review the fossil record of freshwater fish clades with a distribution encompassing disjunct landmasses in the southern hemisphere. Palaeontologically derived temporal and geographic data were used to infer the plausible biogeographic processes that shaped the distribution of these clades. For seven extant clades with a relatively well‐known fossil record, we used the stratigraphic distribution of their fossils to estimate confidence intervals on their times of origin. To do this, we employed a Bayesian framework that considers non‐uniform preservation potential of freshwater fish fossils through time, as well as uncertainty in the absolute age of fossil horizons. We provide the following estimates for the origin times of these clades: Lepidosireniformes [125–95 million years ago (Ma)]; total‐group Osteoglossomorpha (207–167 Ma); Characiformes (120–95 Ma; a younger estimate of 97–75 Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235–21 Ma); Cyprinodontiformes (80–67 Ma); Channidae (79–43 Ma); Percichthyidae (127–69 Ma). These dates are mostly congruent with published molecular timetree estimates, despite the use of semi‐independent data. Our reassessment of the biogeographic history of southern hemisphere freshwater fishes shows that long‐distance dispersals and regional extinctions can confound and erode pre‐existing vicariance‐driven patterns. It is probable that disjunct distributions in many extant groups result from complex biogeographic processes that took place during the Late Cretaceous and Cenozoic. Although long‐distance dispersals likely shaped the distributions of several freshwater fish clades, their exact mechanisms and their impact on broader macroevolutionary and ecological dynamics are still unclear and require further investigation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/1/brv12473_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/2/brv12473.pd

Art and illustration in African publishing

Just as African literature is going through a process,-of change and adaptation to new conditions, so African art is combining new techniques and ideas with ‘traditional’ ideas of the place of art in society. The illustrated book is a relatively new phenomenon in African literature, and the whole area of design and illustration is a problematic one for African publishers.Illustration has so far had a limited role in African publishing — there are very few lavishly illustrated books produced in Africa. To those used to the production and design standards of the West, it is difficult not to overlook the vitality, excitement and potential of the existing examples of illustration. This is not to say that I think African publishers have fully exploited talent available to them, or explored the scope allowed them in spite of limitations of finance, production methods and market pressures. These limitations have been overcome in examples quoted below.</jats:p

PROBLEMS OF EASTERN AFRICA1

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