Bory de Saint-Vincent 1824      Category: Araphid
TYPE SPECIES: Diatoma vulgaris Bory de Saint-Vincent




Smallest to largest - 4 taxa sorted by maximum length

Image Credit: Marina Potapova

CLASS: Fragilariophyceae
  ORDER: Fragilariales
    FAMILY: Fragilariaceae

  1. Sternum may be discernable, or not
  2. Transapical ribs heavily silicified
  3. Spines absent, or scattered at porefields
  4. Rimoportula present

The genus Diatoma possesses a raised central sternum, which may or may not be distinct. Transverse costae are characteristically thickened and septae are absent. Striae are comprised of uniseriate rows of areolae. Each valve has a single rimoportula, positioned near a valve terminus and oriented transapically. A ligula is present on the second girdle band, which attaches to the polar position of the valve, adjacent to the interlocking valvocopula. Spines are scattered near the polar porefields, but are absent elsewhere. Living cells contain numerous discoid, or platelike plastids.

Jüttner et al. (2015) propose that Diatoma and Odontidium, previously thought of as sub-generic sister taxa, should be considered separate genera. Together, Diatoma and Odontidium comprise one of the two monophyletic araphid groups to evolve heavily silicified transapical ribs. The other group includes Meridion, Distrionella, Tetracyclus and Tabellaria.

Cite This Page:
Spaulding, S., and Edlund, M. (2008). Diatoma. In Diatoms of the United States. Retrieved April 25, 2018, from http://westerndiatoms.colorado.edu/taxa/genus/Diatoma

Contributor: Sarah Spaulding | Mark Edlund - December 2008
Reviewer: Sam Rushforth - May 2010


September 20th, 2017 - Change in circumscription

Re-examination of the genera Diatoma and Odontidium led Jüttner et al. (2015) to recommend the use of the name Odontidium at the generic level for taxa treated from that sub-genus of Diatoma. Refer to Jüttner et al. for an account, including a neotype designation for O. hyemale and commentary on the nomenclatural priority of Odontidium.

This taxon appeared as Diatoma, including Odontidium and Diatoma as subgenera, in the Diatoms of the US flora from May 2010 through September 2017. As of September 2017, the genus circumscribes the more narrow concept of Diatoma. A new page for Odontidium was created at this time.