Unidentified Diatom Toome Bridge


Charles Suslavage
 

Hello Dick,
I did get a little free time today and went to work on the unidentified diatom that was earlier identified as T. flocculosa. This diatom is just beyond the capabilities of my economic Chinese microscope. The only statement I can make with any certainty after viewing four examples at 1600x, oil, is no rimoportula. Observing spines maybe pore field not a chance this side of Hyades. The examples of T. flocculosa all had rimoportula so I am able to observe and image this feature.
Charles


Richard Carter
 

Charles,

Thanks for sharing the new images of your unknown.  Looking at your T. flocculosa specimen with its clear rimoportula tells me that your microscope is certainly capable of showing you what you need to see!  Your unknown specimens really don't look like Tabellaria at all, never mind that they look like that drawing in Patrick & Reimer -- that's just a really poor representation, period.  The fact that there is no rimoportula is a strong argument against IDing these as a Tabellaria species.  Also, it appears that the striae come very close to the valve end, leaving no room for the pore field.  (You won't see the actual pores; they are too small to resolve in my microscope, and I'd guess that's probably true for yours, also.)  The pore fields simply look like "bare" areas at the valve ends, no striae there.  And the striae of your unknown look very different from those of your true T. flocculosa.  I still think this all fits Staurosira quite nicely.

I looked at a few more slides today, and discovered one that has all three of the Tabellaria taxa I illustrated.  The slide is on loan from Keith, and the sample is from Cherryfield.  The T. quadriseptata in this sample is essentially identical to the Kilroe West population in terms of valve outline and girdle band structure, but the marginal spines are a little harder to see.  I also remembered seeing some Tabellaria on a slide from a Pliocene deposit in California, and had another look at them.  They look like T. fenestrata, with lightly capitate ends and open girdle bands.  Much shorter than the average for modern populations I've seen, though.  Probably different enough to qualify as a separate taxon, I think.

Off to sleep,

Dick


From: charles
To: diatom_forum@...
Sent: Sunday, August 19, 2012 10:00 PM
Subject: [diatom_forum] Unidentified Diatom Toome Bridge

 
Hello Dick,
I did get a little free time today and went to work on the unidentified diatom that was earlier identified as T. flocculosa. This diatom is just beyond the capabilities of my economic Chinese microscope. The only statement I can make with any certainty after viewing four examples at 1600x, oil, is no rimoportula. Observing spines maybe pore field not a chance this side of Hyades. The examples of T. flocculosa all had rimoportula so I am able to observe and image this feature.
Charles