Field of Science

Forams with Teeth

Time for another foram post. The above image (copyright Robert P. Speijer, scale bar = 100 µm) shows Turrilina brevispira, a typical Eocene representative of the foram subfamily Turrilininae.

The Turrilininae are a group of calcareous forams that first appeared in Middle Jurassic (Loeblich & Tappan 1964). In most species, the test is what is called a 'high trochospiral' form: that is, it coils in a similar manner to, and overall looks rather like, a high-shelled snail. Each of these whorls is divided into at least three successive chambers, sometimes more. At the end of the test is a loop-shaped aperture. At least one species of turrilinine, Floresina amphiphaga, is a predator/parasite of other forams, drilling into their test to extract their protoplasm.

The turrilinines are most commonly classified in a broader foram superfamily known as the Buliminoidea or Bulimnacea. Other buliminoids commonly resemble turrilinines in their overall form. The group has commonly been defined, however, on the basis of what is called a 'tooth-plate'. This is an outgrowth of the internal wall of the test that runs between the apertures of each chamber. The exact appearance of the tooth-plate differs between taxa; in Turrilina, for instance, it is a trough-shaped pillar that is usually serrated along one end (Revets 1987). I have no idea what the function of the tooth-plate is, if indeed any is known, whether it provides an anchor for some cytoplasmic structure or anything else. However, in more recent decades a number of authors have questioned whether the tooth-plate is as significant a taxonomic feature as previously thought. For instance, Tosaia is a Recent genus of foram whose overall morphology and chamber arrangement is fairly typical for the Turrilininae but which lacks any sign of a tooth-plate (Nomura 1985). Excluding Tosaia from the buliminoids on this basis alone would imply a remarkably strong evolutionary convergence of every other feature of this genus.


Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida vol. 2. The Geological Society of America and the University of Kansas Press.

Nomura, R. 1985. On the genus Tosaia (Foraminiferida) and its suprageneric classification. Journal of Paleontology 59 (1): 222–225.

Revets, S. A. 1987. A revision of the genus Turrilina Andreae, 1884. Journal of Foraminiferal Research 17 (4): 321–332.


  1. Hey sir! Love your posts (and am now a patreon-er too!), you're among the half dozen or so critter blogs I check out regularly.

    I'm an amateur but have been on a nature-therapy kick for the last five years or so. Forams have been a source of frustration for me though because so much of the info out there is about DEAD ones and I'm far more interested in their behaviors and physiology when their alive.

    Do you have any sources you'd recommend? I don't have any college so I might have just missed something obvious that you guys all know about. :)

  2. Thank you very much for your contribution! I really appreciate your support.

    You're certainly right that (largely for economic reasons) forams are one of the groups of organisms that are better known as fossils than they are as living critters. I'm afraid that I don't know off the top of my head of any obvious go-to source for info on living forams (i'm presuming you don't have immediate access to academic journals and the like, though these days you can find a surprising amount of articles free online through just a Google search). A lot of books on fossil forams will open with a section summarising their life histories and the like; for instance, the Treatise on Invertebrate Paleontology volume on forams has quite a detailed section on foram natural history though it definitely suffers from being over fifty years out of date (it was published in 1961). Be warned, though: nothing about forams is simple!

    Perhaps one of the best places to start would be at Skeptic Wonder, one of the other blogs here are Field of Science. Its author used to regularly post stuff on forams when she was writing here, and searching on her site should provide you with plenty to whet your appetite!

  3. Ha! Psi's how I found YOU! I think I stumbled across her Haptoglossa article by way of Small Things Considered (My nature therapy started with big mammals and it went all the way down to molecular machines) :)

    I'm pretty good at working my way around paywalls (hates them I does!) and my bigger problem with Forams has kind of been that (as you alluded), the 'fossil' results just overwhelm everything else. I've had some luck incorporating terms like 'behaviors' but it does seem like lots of the good stuff is either in Journals or else in the intro chapters of larger books.

    And glad to help, I owed you a few bucks!

    I've still got a silly dream where you, Joseph from Real Monstrosities, Psi, and a bunch of other great and quirky life bloggers band together and make something a bit like what you're doing in COO, but with a rich collection of perspectives from each critter/thing all woven together in an approachable front page so everyone gets to be as fascinated as I am.

    And yes, I'm a complete nerd. Thanks for the reply!

  4. Ah! I stumbled across something surprisingly useful online about our little tankmoeba friends!


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