Trochosira polychaeta: a colonial diatom from the late Cretaceous exhibiting two contrasting chain-linking mechanisms and a wide range of preservation

Abstract

The fossil species Trochosira polychaeta Strelnikova, exhibits a wide range of preservational states that has led to contrasting interpretations with regard to its resting stage or vegetative cell status. Within shallow-buried, well-preserved diatomites from the Alpha Ridge of the Arctic Ocean, a continuum of dissolution effects is documented and a vegetative cell status is clearly indicated. The chains are formed by a central linking process, but complex marginal structures also constitute a complementary linking mechanism. The double linkage may have supported the integrity of the colonial chains and provided a mechanism for enhanced nutrient uptake. The presence of two distinct types of linking might also represent a stage in a transition from the Cretaceous, when central linking structures were common, through the Cenozoic to the modern, with more common linking through marginal structures.

Keywords:

• Trochosira polychaeta
• Cretaceous
• diatoms
• dissolution
• chain linkage
• transitional form

Acknowledgements

This research was funded by a NERC Research Grant (AESK) and NERC Research Studentship (AD). We acknowledge the benefit of discussions with Jakub Witkowski and Jenny Pike, and the manuscript also benefited from two thorough reviews. We are grateful to Kate Davies for drafting the figures and thank Peta Mudie for arranging access to the CESAR-6 core.