Wednesday, April 22, 2009


I shouldn’t be surprised that I bring the same strengths and weaknesses to two separate searches, even if those searches involve very different venues, tools, and quarry. You are who you are.

This is a tale of those two searches, one very modestly successful, the other unsuccessful. The sites are, one, a stream bed in suburban Maryland and, the other, principally the web. At the former, a stream cuts through the Severn Formation, a thin sandy layer punctuated by small quartz pebbles and chunks of gray phosphate and weakly populated with fish and reptile fossils. The Severn Formation is from the late Cretaceous, some 65 to 70 million years ago. At the latter site (the web), a tsunami of information crashes through all known boundaries creating a mess that often defies efforts to make sense of it.


I am particularly taken with fossil teeth from the shark genus Squalicorax, an extinct group of sharks known only with certainty from the Cretaceous (apparently this group did not survive the massive extinction at the end of the Cretaceous that did in the dinosaurs). Fossils from these sharks can be found in the Severn Formation. My attraction is based, I think, on their distinctive shape – crowns with a long convex mesial edge and, depending somewhat upon the species, a short, often straight, distal edge. The edges of the crowns are usually serrated (serrations are, to me, always a highlight in any tooth), and the height of the root relative to the crown can be impressive. This “drawing” of a Squalicorax kaupi nicely captures those attributes (5/8” on the slant).

The First Search

Half a dozen past searches along the stream site had rewarded me with a handful of small shark teeth and fish teeth, but never a fossil Squalicorax tooth. Over the course of these searches, I tried many searching techniques and strategies, from screening (shoveling gravel from gravel bars or the stream bottom into screens to separate the material) to just eyeing the steep banks of the stream looking for the tell-tale signs of the Severn layer. I have told myself (sometimes out loud) to be deliberate and methodical, but most times my lack of patience leads me to use a scattershot approach. I finally learned, though, that the best approach, for me, is surface collecting of the gravel bars that the stream creates, destroys, and recreates from one visit to the next. Unfortunately, the fruitful method of surface collecting here is tedious and painful requiring that I move on my knees along the gravel bars for several hours at a stretch. (At the Lee Creek Mine in North Carolina, this kind of hunting is called the “Pungo crawl” because you’re kneeling on Pungo River Formation material. Knee pads are standard equipment there.)

This past Saturday, I wandered up and down the stream, surface collecting on the gravel bars. Little stuff, fragments, enough to keep me interested and on my knees, but no Squalicorax. As I worked my way back to where the bank offers a gentle slope for climbing out of the stream, I came across some gravel and settled onto my knees for a final time. A little flake of material, black and white, caught my eye, as I picked it up, I recognized a tiny (1/4”) Squalicorax kaupi. I saluted it with a “Yes!”

Granted, it’s only a modest success given its size,very damaged root, and worn serrations. And it’s a curiosity with its strangely colored crown, half of it, including the tip, blanched white, presumably due to prolonged exposure, the other half the expected blue-black.

The Second Search

The second search sprang from the first. Though this find was my first at this particular site, I have found other Squalicorax elsewhere. Still, this one prompted a question. The Squalicorax are known as Crow sharks. Why?

The first step was easy. Do some Googling and (gasp) some shelf walking in my local public library. Shelf walking is the library research equivalent of surface collecting on a gravel bar – get yourself into a favorable location and begin scanning what’s there – similar aches and pains crop up. A lost art I’m afraid. Googling may have its parallel in screening.

This first step was productive – many sources attributed the common name to the scientific name of the genus, Squalicorax, and, more specifically, to the original name of the genus, Corax. This was the name given by Louis Agassiz back in the 1840s (volume III of his Recherches Sur Les Poissons Fossiles, a fundamental work in the paleontological study of sharks and other fish, cited elsewhere in postings on this blog).

Corax is Greek apparently for “raven” which, for fossil collectors, is, I guess, close enough to “crow” for that to be the common name. But, I didn’t think that really answered my question.

(One of the miscellaneous tidbits uncovered in this effort: Corvus corax is the scientific name for the common raven, according to the Dictionary of Birds of the United States by Joel Ellis Holloway and George Miksch Sutton, 2003.)

After lots of meandering through the web, my local library, and my small personal collection of books, I pieced some things together, but, as I ultimately concluded, not enough. This phase of any search can be disheartening. The expectation is that, just around the corner, is the answer. That’s much like a fossil hunt which often stretches into the dusk because that prize specimen is always just around the corner. This phase involves lots of retracing of old ground – the marks of your passage are everywhere, but still, maybe you missed something.

I tried to address the early signs of trouble – the renaming of the genus needed some exploration. The best place to start (and often end) when you’re researching the taxonomic history of an ancient organism is the Paleobiology Database. That source made it clear that the change in genus names occurred in 1939 and the instigator was someone named Whitley.

Well, turns out that, in a 1939 article, ichthyologist G.P. Whitley renamed the genus Squalicorax. Depending upon your source, Squalus is Latin for “fish” or, more to the point, “shark.” Why Whitley felt compelled to do that is still a mystery to me because the article in question isn’t on the web (we're not quite to the point where all of the world’s knowledge is available at your fingertips – yes, there's lots available, particularly if you have an institutional affiliation or money).

Even worse, there seems to be a bit of citation sloppiness on the web (certainly no surprise there) and in scientific journals (a bit of a surprise there) about where he actually made the name change. For example, in an otherwise very informative article entitled “The Oldest Record of the Late Cretaceous Anacoracid Shark, Squalicorax Pristodontus (Agassiz), From the Western Interior, With Comments of Squalicorax Phylogeny” (New Mexico Museum of Natural History and Science Bulletin), authors Shimada and Cicimurri note that Whitley named the genus Squalicorax in 1939. Their reference? An article they attributed to a 1939 issue of the Australian Journal of Zoology. Unfortunately, that journal began publication in 1953. They have the wrong publication. Seems Whitley published his article renaming the genus in the Australian Zoologist, a publication of the Royal Zoological Society of New South Wales (which, incidentally annually awards the Whitley Prize in honor of Gilbert Whitley for “outstanding publications . . . that contain a significant amount of information relating to the fauna of the Australian region").

It’s not a big deal, I guess, but it’s disheartening. Had I wasted lots of time searching for a 1939 article from the Australian Journal of Zoology when the actual piece was readily available that would have been a bitter pill to swallow. The actual article, as much as my ham handed repetitive searching on the web can prove, isn’t available electronically. So, I’ve gone a different route and made an online OCLC request for an interlibrary loan (or, actually, a photocopy) of the article. I don’t know what I will find, but that’s the beauty and the frustration of the search.

The Shimada/Cicimurri citation error is duplicated in other pieces they’ve published and on websites. For example, Mike Everhart has a nice piece on “Large Sharks in the Western Interior Seas” that covers Squalicorax falcatus, and perpetuates the erroneous citation.


But, none of this actually gets at my underlying question. The translation of Corax may account for the common name used now, but that’s missing the point. Why was the word corax used in the first place in naming this group of sharks? That is, what prompted that link between “raven” (or “crow”) and these sharks back in the early 19th century? I don’t know and, as far as I can tell, Agassiz isn’t talking on the web or elsewhere.

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