Muelleria spauldingiae

Valves are broadly lanceolate to elliptic-lanceolate in smaller specimens. Valve margins are convex and apices are cuneate. The raphe branches are straight, located between two longitudinal canals. Proximal raphe ends are unilaterally deflected within a small, elliptic central area. Striae are straight and radiate throughout. The central striae are more widely spaced than in the rest of the valve. Areolae in the central striae appear larger and more distinct than areolae in more distal striae. Under SEM, external areolae openings are lineolate and appear as apically-oriented slits. Proximal raphe ends do not enter the first row of areolae and distal raphe fissures are bifurcate with branches that separate at a wide angle.

More work is needed to determine if this taxon is conspecific with Muelleria spauldinga Kociolek 2014. The observed differences in external areolae openings (lineolate in M. spauldingiae, round in M. spauldinga) may be due to differential erosion of the external foramina. Although the maximum reported size of M. spauldinga is 48 µm long and 12 µm wide, larger valves may yet be found. Internal valve SEM views are needed for both taxa.

Nomenclatural note: The names Muelleria spauldingiana and M. spauldingiae were published for different species in January and March 2014, respectively. The epithet spauldingiana is an adjectival form based on the noun Spaulding. The epithet spauldingiae is the genitive form of the same noun. Although the use of the genitive and the adjectival form of the same word to designate two different species of the same genus should be avoided, the names are not likely to be confused and are not considered to be homonyms according to the Melbourne Code (McNeill et al. 2012, Article 53.3, Example 12).