Upper Cretaceous Foraminifera

As an introduction to foraminifera, I will give you an idea of their size and actual appearance.  Below is a montage showing a number of pictures of the same slide.   The images range in size from just about what can be made out with the naked eye, to just about the best you can do with light photography (at higher magnifications photographs tend to become poor because of depth of field problems - you can't focus both on the top and bottom of the specimen).  Each "box" of the slide grid is 3.75mm across, and the final specimen is approximately 100 by150 microns in size.

"Bigger" forams allow for better pictures.

"Oliver"

Hedbergella brittonensis
(though there are some who might disagree...)

Small (less than around 100µm) forams are difficult to capture effectively.
That is why SEM pictures are typically used....

While SEM images can show dramatic details they have a major draw back,  Because you must first coat a specimen in a very thin layer of gold or carbon (to make it reflect the electrons) you end up only capturing surface features.  Coloring and internal structure visible in reflected light (through the translucent calcite walls) are not seen.   Understandably many foram workers are quite frustrated by this limitation.   Recent advances in microscopy and image processing have "solved" this problem.  It is possible to take multiple images of a foram in reflected light at different focal distances - and then recombine only the focused pixels into a completely focused image.  There are still some difficulties with picturing "really small" forams, partly to do with lighting and extremely limited focal depths.   So, I've not yet undertaken a complete re-photographing of hundreds of species (though it is certainly my plan).  In future updates I'll include more about this process, some images, and some thoughts on how the process is coming along.

I am not really all that pleased with the following picture (but it helps to illustrate the above commentary).  Still, if you examine the comparative images below you can see the improvement (particularly when compared to the slide image above).

Identifying Forams

Here is a series of shots which show some of how I go about identifying a foram.   To begin with, you have to look at the specimen.  The left image is a reflected light photograph of a specimen (it is approximately 150µm in height).   Typically forams will show different details if you get them wet (they become somewhat translucent and surface light dispersion is limited).  Frequently that is necessary to recover important morphologic information.  But, it is hard to photograph them that way.  Usually it is helpful to draw the specimen you are looking at partly to have a record of it, but mostly because it forces you to really look at it and see its detailed structure (and also because you can see things with your eye that are hard to capture on film, and your mind can often fill in little blanks and make sense of "dirty" specimens).  The middle picture (below) is a picture of such a sketch, from the index card I keep for each species - with a drawing and various taxonomic and nomenclatural notes.  After having seen what the specimen you are trying to identify really looks like, is a good time to search the literature for a species which is a good match for the one you are looking at.   To the right (below) is a camera Lucida drawing made by Helen Tappan, and published by A. R. Loeblich in 1946.  In later samples I found an individual that preserved more of the last few chambers.  So, I feel pretty good about calling this species:

Ammobaculoides plummerae.

Some time after I did the identification I took these SEM photos

This page is under development.

To those few of my professional colleges who might have stumbled down this far....

Here is a mediocre light photograph of the quite weathered holotype for Anomalina (Gavelinella?) petita, and some SEMs (9-13) of specimens of the species with the characteristic heavy sutures preserved.  When you get the holotype wet you can actually see the limbate nature of the sutures.  See also (14-16), co-occurring smaller specimens I've called cf. petita - but which are likely within the range of natural variability for the species.  The correspondence to the holotype is much more apparent.  Discussion...?