Siliceous and Delicious

Private Kotrc, reporting for duty. It’s 8:31, I’m installed at Darwin’s with a cup of coffee and another one already pre-paid, four swift miles under my belt and two cookies seeking to join them in the course of the morning. I am amped and ready to go—the radiolarian lineage project had better prepare to meet its maker.

Step one is to look over the two Sanfilippo papers I found last week, which may harbor some useful information on the Lophocyrtis lineage, and where I might find samples from which to study it. The Sanfilippo and Caulet (1998) paper, which I recall was one of the two, is of limited use, because it’s focused on the Lophocyrtis lineage at high latitudes. Since my master’s work (along with Dave’s undergraduate student) demonstrated that most of the change in silicification occurs at low latitudes, and that the high latitudes see very little change in silicification (if any), I want to be looking at tropical samples for this study.

For some unfortunate reason, I don’t seem to have saved the second reference I discovered—so it’s back to google scholar. Aha. There it is. Well, upon a first reading, it doesn’t necessarily make my life easier… One point of some concern is that she says the 150µm size fraction was the most useful for these forms—but the prepared slides in the MRC are (almost all, as far as I know) sieved at 63µm. So, the material I need may be missing. Also, her paper describes a whole host of descendant lineages from the ancestral Lophocyrtis, and it would of course make most sense to quantify silicification through the ranges of all of them. This seems like an unreasonable amount of work. If I am to choose, though, how to choose which one(s) to study?

I wonder if Sanfilippo has the samples used in that paper in her personal collection. Should I just email her to ask? I drafted up a quick email, but decided to move on to the next lineage quickly before losing too much momentum, as I could feel my motivation starting to flag a little.

The next lineage down the list is Artophormis. Let’s see if that’s any easier to get a handle on. Another search on google scholar confirms there are no useful references on this lineage beyond the entry in the Bolli volume (which was the reference I cited in my “game plan” document). There is a description of both species, A. barbadensis (the ancestor) and A. gracilis (the descendant), in the ODP Technical Note #27 (“Cenozoic Radiolarian Stratigraphy for Low and Middle Latitudes”, Nigrini and Sanfilippo, 2001), and it supports their evolutionary relationship, though it gives no additional information. In a sense, this makes things easier—I am looking for 15 samples that contain either species, over their stratigraphic range. So, into R I delve…

The most promising single-site candidate for this lineage is leg 41, holes 366 and 366A. They cover most of the range of the taxon… but the occurrences appear to be mostly A. gracilis, with only 5/61 being A. barbadensis. This might be a problem. Let me see how much A. barbadensis there is in Neptune at all. Hmm… again, the data in Neptune suggest that things aren’t as clear-cut as the literature would suggest: A. barbadensis (blue in the image below) doesn’t just change into A. gracilis (red squares) at the E/O, but they seem to coexist, and the ancestor seems to persist well into the Oligocene, and at least one sample suggests it’s still around in the earliest Miocene (although, this could of course be due to any sort of error, too).

In any case, I’ll go ahead and select samples adequately covering the ranges of both species according to the view afforded by Neptune, since it’s what I’ve got to go by.

Continued working on this after lunch, for which I had to return to the office (for use of the microwave), but found that progress slowed immeasurably once I was back in the windowless, fluorescent-lit hole I’m relegated to now that my office is being “refurbished” (these quotation marks justified by the complete absence of any workers since Thursday). Alas, I’m stuck here for the afternoon, as it’s not worth moving since I have to back here at 4 pm for lab meeting, which I don’t have the balls to miss—Andy was so excited, and seemed to really want me to be there. It doesn’t seem smart to snub your advisor when the aim is to graduate, and he’s the man who will make that happen.

Anyhow. My brilliant hunch to use site 366 for all my Artophormis needs fell flat on its face: the MRC collection does not have slides made at the relevant intervals. This is a bit of ginormous bummer, because I’m now going to have to scrounge around other sites and patch something together, probably from various ocean basins. It all goes to show that the Oligocene is a bit of a shithole when it comes to microfossils. It’s surprising that it would be so hard, given the great cloud of Oligocene points in the Neptune database, to find made slides that might contain Artophormis…

So, on I pressed… Had to stop for lab meeting, which was—unsurprisingly—pretty uninspiring. Andy announced that lab meetings would rotate among various levels of inclusivity this year, from once-monthly meetings of just the Knoll group, to those including the Knoll, Johnston, and Pearson group, to those including the whole geobiology group (including MIT). A heinous approach, if you ask me—lab meetings are barely ever productive as it is, and the bigger the groups get beyond that, the worse it is… Fortunately, a bigger group also means it’s less likely I’ll be missed if I don’t show up… which I imagine will be a frequent happenstance in the months to come.

At just before 7pm, I finished sample selection for Artophormis, the first completed task of the day. Not terribly motivating—at one lineage per day, it’ll take me another four days to finish sample selection (rather than the two days I have set myself as a target)… But, this is the Great Three Day Push, and thus not the time for doubt or dalliance, but as in other sorts of labor, the time for sharp, fast exhalations and pushing hard.

I resisted the monumental urge to reward myself with some procrastination I felt I had earned, and instead pressed ahead to the next lineage, Stichocorys. Not tremendous amounts of literature immediately apparent, so far as I can tell. According to the Bolli volume, and Sanfilippo & Riedel 1970, and the ODP technical note, S. delmontense is ancestral to/evolves into S. peregrina. S. wolffii is considered ‘probably not a good biological species’, so I’m best off disregarding it, I think. I can’t find anything about the phylogenetic relationships of S. johnsoni, and the other species of Stichocorys in Neptune (diploconus, armata, seriata, and biconica) don’t seem to have much in the way of mention in the literature at all (certainly not in the ODP technical note). I’m going to disregard them all for now; fortunately S. delmontense and S. peregrina make up three quarters of the of the Stichocorys occurrences in Neptune, so I should be OK.