Pennate diatoms having a
on only one
A monoraphid diatom is a type of
diatom. Example genera include Cocconeis, Achnanthidium, and Eucocconeis.
During the ontogeny of monorahid diatoms, a raphe begins to form on each valve. One valve completes its raphe, and becomes the raphe valve. The other valve fills its incipient raphe with silica, leaving a thickened axial rib, and becomes the rapheless valve.
The genus Nupela includes some monoraphid species and some biraphid species. In this web flora, Nupela is included in the biraphid group.