Thursday, May 27, 2010

The Gulf Disaster and Filefishes By The Book

I have watched some of the live video feed from British Petroleum showing the oil flow from the wreck of its exploratory well on the floor of the Gulf of Mexico. At one juncture, I couldn’t stand the silence of the video stream, so for several minutes I gave it a soundtrack – Shapes of Things by The Yardbirds.

Shapes of things before my eyes,
Just teach me to despise.
Will time make men more wise?

An incredibly sobering juxtaposition of sight and sound. But, I could only let the song loop a couple of times – the combination was too depressing. I hope the current effort to seal the well is successful, though I know the nightmare for wildlife in the Gulf is only just beginning.

Among the victims of this oil spill, now being described as the worst in U.S. history, will be some species of filefishes, members of the diverse Family Monacanthidae, with about 32 different genera and 102 species. (Joseph S. Nelson, Fishes of the World, 2006, p. 454-455) These fish are a distinctive flattened shape with a prominent dorsal spine, sometimes joined by another, much smaller spine. Some species come in a brilliant array of colors. Filefishes range in size from ones appropriate for home aquaria to the Orange Filefish (Aluterus schoepfii) which can grow to about two feet in length. Filefishes’ teeth are designed specifically for nibbling which makes it clear they aren’t near the top of the food chain. The pictures below show a Fringed Filefish (Monacanthus ciliatus) (on left) and a pair of White-Spotted Filefish (Cantherhines macrocerus) (on right), two of the filefish species that live in the Gulf of Mexico.

Paleontology has a way of revealing my ignorance, often leading to a research voyage of discovery. A fossil acquisition a couple of weeks ago launched one of those voyages. At a fossil club raffle, I won a couple of fish vertebrae in a small plastic bag. The label identified the contents as:

Filefish sp.
Two vertebrae
Early Pliocene
Yorktown Fm.
Lee Creek, NC

Love the use of “sp.” following “Filefish” to indicate an unknown species – makes it seem so scientific, though, of course, there’s nothing scientific about using the popular name “Filefish.” I was pleasantly surprised to see that, not only did I have two vertebrae, they were fused together.

So, I asked myself, what is a “filefish” and should I have any confidence in the other information on the label?

Lee Creek? I’ve collected there. Two different geological formations yield specimens at this site – the Pungo River Formation (the fossil-producing units of this formation are mid-Miocene, laid down roughly 14-16 million years ago) and the Yorktown Formation (early to mid-Pliocene, deposited about 3-5 million years ago). Though the marine environments were different in both time periods, these were fauna-rich places. In the mid-Miocene, this area was covered with relatively quiet, temperate to semi-tropical ocean waters. During the Pliocene, the Gulf Stream may have diverged into this area meeting a cold upwelling, creating a rich feeding ground. The fossils of a combined total of 104 different species of fishes collected from these two formations, according to Purdy et al., “represent the first fossil record of a marine vertebrate, high use feeding area and the largest and most diverse fossil fish fauna known from the Atlantic Coast Plain.” (Robert W. Purdy, et al., The Neogene Sharks, Rays, and Bony Fishes From Lee Creek Mine, Aurora, North Carolina, Geology and Paleontology of the Lee Creek Mine, North Carolina III, Smithsonian Contributions to Paleobiology, Volume 90, 2001, p. l88)

Most of my collecting at Lee Creek has been from Pungo River material, so I was startled to find in my collection a group of small vertebrae that were very, very similar to my raffle win. These were clearly labeled as coming from the Pungo River Formation.

Hmm, maybe the Yorktown identification for the new addition to my collection is out of whack.

I then decided to do this “by the book.” The full reach of the fossil fauna or flora at a specific location is sometimes the subject of an amateur or professional paleontologist’s written labor of love, and he or she creates a reference for collectors, a scholarly analysis, or a textbook. These are a godsend to the amateur collector. For more than a decade, the Smithsonian Institution, in its series called Contributions to Paleobiology, has been publishing treatises on the fossils of Lee Creek Mine. The bible for Lee Creek fossil fish is the lengthy article titled The Neogene Sharks, Rays, and Bony Fishes from Lee Creek Mine, written by Purdy et al. (Full cite given above.)

But, even with the product of such a labor of love in hand, there’s no guarantee of success. Such a bible doesn’t necessarily have the answers you seek, may undermine what little you thought you actually knew, or raise other, more vexing questions. An unambiguous answer from these good books is certainly not a given.

So, when I turned to “filefish” in the article by Purdy and colleagues, what did they have to offer? Just an unambiguous answer. Amazing.

The filefishes, they said, at Lee Creek were Aluterus sp. and their fossil vertebrae are found in both the Pungo River and Yorktown Formations (“common” in the former and “abundant” in the latter). They then spoke directly to me when they noted that two or three of the vertebrae “are often found as a fused unit.” I was thrilled. The picture of three fused vertebrae included in their description of the Aluterus sp. sealed the deal. (The line labeled f is 1.25 cm long.)

I realize now that these are common fossils, well known to the seasoned collector at this site. Though nothing surprising in the larger scheme of things was revealed by this voyage, to this novice, it was exciting.

Still, this voyage was also tinged with sadness.

As a fossil collector, I realize that a specimen I hold in my hand may be the product of a painful death, triggered, perhaps, by some natural disaster. Death and extinction are facts of life. It’s a cautionary thought, but one that doesn’t excuse us for visiting such death upon many members of myriad species through the unnatural disaster unfolding in the Gulf of Mexico.

In the picture below, a Scrawled Filefish (Aluterus scriptus) swims in the Florida Keys National Marine Sanctuary.

Credits for Photos

All pictures of extant filefishes are from the NOAA Photo Library: Fringed Filefish,
White-Spotted Filefish, and
Scrawled Filefish.

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