Wednesday, November 26, 2014

Fieldwork Equations

I’m wrestling with two realities about paleontology.  The first involves paleontological fieldwork; the second, fieldwork’s aftermath.

To begin with, take fieldwork, a challenging and time consuming endeavor with no assured success.  In an essay on his own fieldwork, evolutionary biologist Stephen Jay Gould erected a straw man argument denigrating fieldwork – “An eminent colleague, a fine theoretician who has paid his dues in the field, once said to me, only partly facetiously, that fieldwork is one hell of a way to get information.  All that time, effort, and money, often for comparatively little when measured against the hours invested.”  (Opus 100, The Flamingo’s Smile:  Reflections in Natural History1985, p. 183-184.)  Responding with his characteristically affirming enthusiasm, Gould said that’s not the reality of fieldwork because the rewards are so great and the enjoyment abundant.  “[A]ll the frustration and dull, repetitive effort vanish to insignificance before the unalloyed joy of finding something new – and this pleasure can be savored nearly every day if one loves the little things as well.”  (p. 184)

Paleontologist Peter Vaughn turned fieldwork into an equation.  According to paleontologist Michael Novacek in his book Time Traveler:  In Search of Dinosaurs and Ancient Mammals from Montana to Mongolia (2002), Vaughn “described paleontological fieldwork as 49 percent anticipation, 49 percent recollection, and 2 percent success.”  (p. 49.)  Certainly, Vaughn was not railing against fieldwork; he was simply being realistic that a lot goes into it and the results are not assured.  Regardless of how puzzling this equation is (e.g., I’m really not sure what “recollection” is and wonder if he’s mixing apples and oranges), that two percent success is pretty slim.  That, asserted Vaughn, is the reality.

Given my last couple of experiences of carefully planning and carrying out forays into the field looking for the fossilized calcium carbonate shells of foraminifera and ostracodes with absolutely nothing to show for the effort, I decided, for just a moment, to ward off Gould’s zeal and buy into his straw man argument because, right then, I concluded a two percent solution isn’t a strong enough allure.  I eschewed fieldwork (my half-assed version of it) and bought (oh, the horror) some Cretaceous matrix online – yes, I let someone else do the fieldwork for me.

Sight unseen, I purchased slightly more than two and a half pounds of purportedly unsorted matrix collected from a Cretaceous formation from which I hoped to extract microfossil shells.  It didn’t start off well.  What tumbled out of the box that came through the mail was some pretty dispiriting rock.

There’s another paleontological reality which came into play at this point – fieldwork engenders tedious, painstaking, seemingly never ending lab work.  When Peter Makovicky, associate curator at the Field Museum, described the work on the fossil bones of the dinosaur Siats meekerorum, an apex predator, he concluded that every hour of fieldwork generated 100 hours of lab work (and, for the S. meekerorum, there was a lot of fieldwork – a summer of exploring and finding, and two summers of excavating).  (Steve Johnson, Dinosaur Discovered by Field Expedition Rivaled T. rex, Chicago Tribune, November 22, 2013.)

I am no stranger to that reality. Take my recent, unsuccessful efforts in the field, they generated many hours of soaking and screening matrix, and days spent hunched over the microscope.  In fact, for microfossils, it’s lab work itself that determines whether the fieldwork is successful or not.  In many ways, the lab work under those circumstances becomes a continuation of the searching and exploration in the field.

The mail-order Cretaceous material came with a mix of unknowns and knowns.  It was collected, at some unknown point in the past, at a construction site somewhere near the Texas town of Prosper (about 35 miles north of Dallas and marked in the geologic map below), by someone, whom I don’t know, who, for a small price, mailed it to me.

The polka-dotted green area in this map shows the presence of rocks of the Austin Group.  (This map is a tiny excerpt from the Sherman sheet of the geologic atlas of Texas.)   Somewhere in that green near Prosper was the construction site where the Atco Formation (part of the Austin Group) outcropped.  This material, averred the seller, came from this formation which dates to the Coniacian Age (89.8 to 86.3 million years ago) during the Upper Cretaceous Period.  One could be skeptical that the seller had it right about the formation, but, for better or worse (mostly worse), much about the matrix screams “Atco Formation!”

The rocks of the Atco Formation are dominated by, and bound together by, calcium carbonate. It has been described as composed of “thin-bedded calcisiltite and indurated chalky limestone interbedded with gray calcareous shale and mudstone.”  (Charles C. Smith, Calcareous Nannoplankton and Stratigraphy of Late Turonian, Coniacian, and Early Santonian Age of the Eagle Ford and Austin Groups of Texas, Geological Survey Professional Paper 1075, U.S. Geological Survey, 1981, p. 1)  The key word is “indurated.”  Porous rock is considered indurated if it has been “cemented” together through mineral deposition.  (John O. E. Clark and Stella Stiegeler, The Facts on File Dictionary of Earth Science, 2000, p. 172.)  In other words, it becomes very solid, resistant to pressure and scraping.  Appropriately enough, the formation is named after the company whose quarry is the type locality – the Universal Atlas Cement Company (of McLennan County, Texas).

A lot of what I bought is chunks of hard rock, studded with bits of pebbles and, on occasion, teeth; the rest is fairly friable, crumbling with manual pressure.  With some of former, I decided to sacrifice the microfossil shells by soaking these chunks in vinegar, letting the acetic acid interact with the calcium carbonate in the rock, turning it into calcium acetate which stays in solution and carbon dioxide which bubbles away.  Time consuming, sure, but I just let the acid do its thing.  The effort has been going on for some three weeks – I periodically refresh the vinegar, and poke at and otherwise abrade the surfaces of the soaking rocks  to expose more calcium carbonate.  I am encouraged – some of these pieces are actually breaking apart.

There are “little things” in the effort to dissolve the calcium carbonate that have exerted a bit of magic and kept me engaged, even opening up new areas of exploration (such as the chemistry of the interaction between calcium carbonate and acetic acid).  Just the visual display that is involved in the process is entertaining.  One piece of matrix, which gave off bubbles at a furious pace from several points on its surface, amused me for some time because of the organized array of bubbles that emanated from it and how they arranged themselves on the surface of the vinegar – miniature, carbon dioxide fireworks.

The material that could be crumbled into much smaller grains was soaked in water for several days and then screened.  The smallest of the particles captured by my screens might yield forams and ostracodes, if anything in this material will.  Afraid of the verdict, I haven’t yet examined this material for microfossils.  But, I have scrutinized the particles of one millimeter or slightly larger and, though few, there have been some interesting finds.  Here are a couple of them.

The first specimen is a tooth from a shark, a Squalicorax falcatus.  The tooth is certainly the worse for wear, but some of the serrations have come through those nearly 90 million years.  The second photo shows the occlusal (left in the photo) and lingual (right) sides of a tiny tooth from what I believe to be a Ptychotrygon triangularis, a ray.  Both are first time finds for me.  (These identifications are based on Bruce J. Welton and Roger F. Farish’s The Collector’s Guide to Fossil Sharks and Rays From the Cretaceous of Texas, 1993.)

Okay, it’s not much to show for three weeks and counting invested in two and half pounds of mercenary Cretaceous matrix – some bubbles and a few teeth.  The work has been tedious and tiring, but, I have to admit that Gould had it right – be open to enjoying and marveling in those “little things” experienced in the field and, I'd add, in some of the lab work as well.

When biologist and gardener Roger B. Swain penned a piece about Viktor Muhlenbach of the Missouri Botanical Garden, who spent years walking along the railroad tracks in St. Louis cataloguing the incredible variety of flora he found growing there, Swain reflected on the possible attraction such an activity might hold.  He likened walking the rails searching for plants to similar endeavors such as birding and beachcombing.  I’d insert paleontological fieldwork and, even, some lab work into his list.  Swain concluded that their allure arises from the very doubt about the outcome.  He wrote,
Such excursions are risky, of course.  There is always the chance that you’ll find nothing, but that chance makes the finding more momentous . . . .  That very uncertainty is more important than most of us realize.  God does play dice with the universe, and out of the uncertainty comes anticipation, and, in turn, hope.  (Field Days:  Journal of an Itinerant Biologist, 1983, p. 122.)

Monday, November 3, 2014

Mysterious Assassin at the Natural History Museum

The assassin moved slowly through the small lobby.  Reaching the sunlight that streamed through a set of locked glass doors, she (he?) paused.  For the moment, she was alone in this area open only to staff and volunteers of the Smithsonian’s National Museum of Natural History.  Later, we would wonder how she made it into this inner sanctum.  Did someone unknowingly give her access?  Certainly, not knowingly, because she was a dedicated and skilled assassin, sporting a fear-inducing piece of armor and able to dispatch her victims with the stab of her long, curved weapon.

As soon as I opened the stairway door to the lobby, I knew something was amiss.  It took me a moment to register what was definitely out of place here.  Ignorant of her lethal nature, I innocently approached her.  She went still at my approach and, when I dropped a tissue next to her, she crawled onto it.  Her size alone gave me pause.  Gingerly holding the tissue at one corner and then another as she moved inexorably up toward my hand, I hurried through a corridor, past museum offices, then into the public lobby, and finally out into the open air and the noises of Constitution Avenue.  I deposited the tissue in the grass behind a bush and the assassin slowly, very slowly walked off.

This is the large Arilus cristatus, a member of the group of bugs known as Assassin Bugs.  She bears the popular name of Wheel Bug in recognition of the extension of her thorax, a striking cogwheel structure.  This crest (cristatus is Latin for “crest”) is unique among U.S. insect species, but its function remains largely a mystery.  As zoologist Bob Thomas observes
There are no firm opinions on the purpose of the gear-like structure on the wheel bug’s thorax. It may serve them in species recognition, may help potential predators recognize them as dangerous, or the teeth on the gears may make them less palatable or more uncomfortable to eat. Since they have a ravenous appetite for agriculturally damaging insects, maybe the wheels are indeed a Rotary symbol of “service above self.”  (Wheel Bug, Arilus cristatus, Loyola Center for Environmental Communication, Loyola University of New Orleans, November 11, 2009.)
Her prey are a mixture of insect heroes and villains, among them caterpillars, Japanese Beetle larvae, wasps, lady bugs, and honey bees.  In the nymph stage, she feasts on aphids.

Her modus operandi is quite dramatic.  With that long, curved, red proboscis, she injects her victims with a paralyzing mixture of enzymes that quickly dissolves the internal organs which are then sucked out.

Much of what I’ve read emphasizes how slowly this insect moves, whether walking or flying.  Coming in at between some 1 and 1 1/4th inches long, it’s probably just as well for the rest of us that the adults are not in a hurry.

Even more disconcerting, particularly given my maneuver through the museum’s corridors with the Wheel Bug-bearing tissue, is that, when disturbed, she is known to use her sharp proboscis on humans, delivering a deeply painful and enduring bite.  As described in the online Wheel Bug profile prepared by the Entomology and Nematology Department of the University of Florida:
This bite has been described variously as worse than stings from bees, wasps, or hornets. Barber (1919) and Hall (1924) described in detail the effects of such bites. In general, initial pain often is followed by numbness for several days. The afflicted area often becomes reddened and hot to the touch, but later may become white and hardened at the puncture area. Occasionally, a hard core may slough off, leaving a small hole at the puncture site. Healing time varies but usually takes two weeks.
(The two citations in the preceding description of the effect of a Wheel Bug’s bite are: G.W. Barber, On the bite of Arilus cristatus, Journal of Economic Entomology, Volume 12, 1919; and M.C. Hall, Lesions due to the bite of the wheel-bug, Arilus cristatus (Hemiptera; Reduviidae), Journal of the Washington Academy of Science, Volume 14, 1924.)

Wheel Bugs have a single generation during the year, largely spending the spring as nymphs, the summer as adults, and the winter as eggs (which, incidentally, look much like a compact collection of bullet cartridges).

Now, I have to admit that, not knowing what insect this was when I encountered it on the sunlit floor, my instinctive action of removing her to the great outdoors was perhaps somewhat misguided.  Afterwards, before heading to the literature, I did wonder if she could have been some rare, tropical insect escaped from the museum’s Entomology Department and if what I’d done was such a good thing.  Was this an invasive that would soon disturb the ecology of the Washington, D.C. area?  Luckily, no.  I assume she came in from the grassy area outside the glass doors; though, how this slow-moving assassin accomplished that trick remains a mystery.

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