FLOW PATTERN AROUND THE RIGID CEPHALIC SHIELD OF THE DEVONIAN AGNATHANERRIVASPIS WAYNENSIS(PTERASPIDIFORMES: HETEROSTRACI)

Palaeozoic armoured agnathans (or ostraco- derms) are characterised by having an external, bone shield enclosing the anterior part of their bodies, which demon- strate great diversity of both forms and sizes. The functional significance of these cephalic shields remains unclear (they may have been a functional analogue of the vertebral col- umn, or merely afforded protection). Here we assess the importance of the cephalic shield in terms of locomotion. In order to do this, we have studied flow patterns of the Devo- nian heterostracan Errivaspis waynensis (White, 1935), using an anatomically correct model of E. waynensis positioned at different pitching angles. The fluid flow was visualised …