Phaeodactylum tricornutum UTEX640. Valve biological interior (side towards the cell) from acid cleaned material.

<p>Fig 3a. Largely intact valve showing greatly thickened longitudinal costae around raphe. Fig. 3b. Central area of a broken valve showing recurved proximal raphe ends.</p

Phaeodactylum tricornutum UTEX640. Whole cells.

<p>Fig 1a. TEM thin section of an oval cell across the transapical plane. A single valve is observed at the top of the cell. Fig 1b. SEM of an entire cell after critical point drying, with a visible siliceous valve. Fig. 1c. SEM of a critically point dried cell in girdle view. There was no valve on either side.</p

Phaeodactylum tricornutum UTEX640. Valve biological exterior (side towards the environment) from acid cleaned material.

<p>Fig 2a. Largely intact valve illustrating simple proximal endings of raphe in exterior view. Fig 2b. Broken valve in external view. 2c. Higher magnification of central area of the specimen in 2b. The arrow indicates the position of the recurved raphe ending, best seen in broken valves or in interior view.</p

Simplified maximum likelihood tree.

<p>The optimal maximum likelihood tree with crown clades collapsed. Numbers at nodes are bootstrap support values of 50% or above. The solid line clades or terminal strains represent taxa which could not be rejected by the AU test as sister to <i>P</i>. <i>tricornutum</i> plus <i>G</i>. cf. <i>exigua</i>.</p