paleonet Tentaculitids

[jmghist@xxxxxxxxxxx]

Perhaps, I can add some information concerning the tentaculites.  Quite a few years ago, I worked on tentaculites from the Devonian in Ohio. (Master's thesis).  

First of all, the specimens in the thin-sections definitely look like tentaculites.  If they are, this would rstrict the the sediments to a Silurian-Devonian age.  The group appears to have become extinct at the Frasnian-Fammenian boundary, although I have heard reports that a very small number may have just made it through into the Fammenian.  They definitely did not last into the Carboniferous.  The specimens appear to be all fairly thin shelled with one or two showing an initial bulbous chamber (center of Tenta03-248).  This would suggest that they probably belong to one of the "planktonic" forms (my interpretation based on buoyancy studies of the shells) (e.g. Nowakia, Viratellina, Styliona).  The apparent lack of rings on many would narrow this down to one of the styliolinids.  I would need to reference some materials to be any more definite.  

As to your comment "they only been found within deep marine settings", tentaculites have been found at all depths.  In Ohio, large thick shelled forms (Tentaculites scalariformis) occur in relatively shallow-water limestones in some abundance.  These forms are as indicated above, thicker shelled and usually possess septa.  They also grow to fairly large size (30mm+).  The planktonic forms are usually much smaller (<10mm).

Any specific identification is difficult from thin-sections.  Macro views of specimens would allow more precise and definitive identification.  Do you have any such photos?

Most of the people I knew working on tentaculites in the 70's are probably not any more.  Although names that come to mind are Larssen (Sweden) (spelling?), Lardeux (France), Blind (Germany or Austria), and Hasjlasz (Poland) (again spelling?)

If you want, I can do some more checking around.  You can contact me either through paleonet or directly at jmghist@netzero.com.

John M. Ghist
Bailey, Colorado
USA