Acritarch clusters from the Cambrian (Miaolingian) of the Příbram-Jince Basin, Czech Republic

Monogeneric clusters of five acritarch genera (<i>Adara</i>, <i>Cymatiosphaera</i>, <i>Eliasum</i>, <i>Synsphaeridium</i> and <i>Timofeevia</i>) were discovered in palynological residues obtained from fine-grained siliciclastic samples from the middle Cambrian (Miaolingian) Jince Formation of the Příbram–Jince Basin (Czech Republic). The clusters consist of two to more than 100 individual specimens and lack a common pattern of organisation. Acritarchs within clusters fall within a similar size range, regardless of generic affinity. Proposed mechanisms for the formation of these acritarch clusters are discussed: for the Jince Formation clusters, aggregation within algal blooms or primary colonial behaviour are the most plausible explanations. In addition, a summary of reports of acritarch clusters from lower Palaeozoic strata is included: clusters of a variety of acritarch genera have been documented from rocks of early Cambrian to Late Devonian age.