Glance at the list of fungi in the Biodiversity Action Plan and you will see that one group has been singled out above all. These are the tooth-fungi. What are tooth-fungi, and why are they so important? The tooth-fungi are not necessarily a closely related group. They share 'teeth' in the same way as dolphins and herrings share a fin – the teeth have evolved on unrelated species because it happened to suit their particular lifestyles.