Article: Ludlow benthonic assemblages
The communities recently described by Calef and Hancock are considered to provide an inadequate picture of Ludlow faunas and their palaeoecological significance. Alternative assemblages, including the important non-brachiopod benthos, have been compiled from the evidence of published faunal lists. It is here maintained that these four assemblages reflect more accurately than those of Calef and Hancock the faunal distribution within the Ludlow rocks but no special significance is claimed for them; each contains subdivisions which may be more readily explained in palaeoecological terms. It is suggested that the recent emphasis on depth-communities has led to neglect of other very important environmental controls, particularly the nature of the substrate. The concept of continuous regression through the Ludlow is considered untenable in the light of sedimentological evidence. The degree of diachronism of the shelly faunas is assessed. It is concluded that the picture drawn by Calef and Hancock is an oversimplification resulting, perhaps, from the attempt to impose a relatively straightforward Llandovery pattern on to the more complex Ludlow rocks.