Thursday, February 17, 2011

The Taxonomy Apprentice


And they're running! Wet and wetter
get the stairs, the rooms, the hall!
What a deluge! What a flood!
Lord and master, hear my call!
Ah, here comes the master!
I have need of Thee!
from the spirits that I called
Sir, deliver me!
 ~ from the poem Der Zauberlehrling (The Sorcerer’s Apprentice) by Johann Wolfgang von Goethe
 (Translation by Brigitte Dubiel)
The wise systematist wandered out for a breath of air or a nap, leaving me alone, a pupil knowing just enough to unleash a fury, but not enough to steer or rein it in.

Over the past several weeks, I’ve often thought that now was the time to compose this posting only to have my demon muse set before me still more leads to explore – more comments, articles, papers, and books that might, just might, be relevant to the topic at hand.  The futile search for an item that appeared in a 1927 edition of the Geological Survey of Nigeria, Occasional Papers sparked my rebellion and set me to writing.  Still, it grew (and grows) out of control.

[References and links (where available) are provided in a listing of sources at the end of this posting.  Some, though not cited in this posting, are included because they may be of interest.  Some references that are possibly relevant aren’t included because I haven’t been able to get my hands on them, such as the 1927 paper just mentioned.  Also, any references originally embedded in quotations below have been omitted.]

This quest began innocently enough with my high bid, indeed, the only bid (a warning sign?) on a small fossil in a silent auction.  This specimen is light tan and projectile-shaped (first picture on left below), both ends clearly broken off, exposing a dark brown glassy interior (first picture on right).  This fragment is 53 mm long (a little more than 2 inches) and 7 mm wide (a bit above a quarter inch) at the widest end.  Longitudinal grooves (and complementary ridges) cover the exterior.  On one side there’s a single pair of distinctive grooves, wider than the others with small cavities running along their bases (second picture on left).  This pair of unique grooves extends the length of the fragment, with a single, narrow groove between it.  A total of 25 narrow grooves can be counted at the wider end of the fragment, including the one running between the wider pair.  Also, at certain junctures, one of the narrower grooves is seen to die out (second picture on right).

The label for the fossil reads:

Cylindracanthus sp.
Fish rostral spine
Lutetian/Middle Eocene
Blue Circle quarry, Harleyville, SC

I’d never seen a Cylindracanthus before and, to be honest, wasn’t sure what a “rostral spine” might be.  A spine projecting from the rostrum or snout of the fish?  Sticking straight out at the end or at an angle?  How much of the spine did I now have?  What kind of fish might sport this?

All good questions.  Unfortunately, I asked another and unleashed the floodgates – what’s its taxonomic history?

This posting focuses on my effort to uncover and make some sense out of the taxonomic treatment of Cylindracanthus.  The story that unfolded for me is one that stretches from the early 1800s to the first decade of the 21st Century, and, in all likelihood, will be adding chapters in the coming decades.  It involves members of the pantheon of paleontological greats, such as the Swiss naturalist Louis Agassiz and John Leidy, one of my favorites, who, at the height of his paleontological career, was the dean of this field in the United States.  A host of other players also enter the story.  Each of these, the leading lights and the lesser ones, affects the story, sometimes moving it forward, but often forcing us to go back and work out a kink in the plot.  International in its scope, the story plays out not only in the U.S., but in England and Europe, and elsewhere.

I wish I could say I understand all of the plot twists and their meanings, but I cannot.  This is, after all, the land of taxonomy and fossils, a strange place where not everything is what it seems (as I described in the posting immediately preceding this one).

In the acerbic words of some of its scientific reviewers, the Cylindracanthus genus has been in “taxonomic chaos” (Fierstine, 1974, p. 43), or “long been a taxonomic problem” (Parris et al., 2001, p. 161).  Unfortunately, I didn’t know any of that when I turned to my small collection of books for any mention of Cylindracanthus and then switched on my computer.

Appropriately enough, the taxonomic history begins by offering a choice among three different opening chapters.

First, there’s Leidy with his description in 1856 of some fossilized fragments of “apparent bone” from Cretaceous formations in New Jersey and Alabama (Leidy, 1856).  The best of the fragments was “over three inches in length with the extremities broken off, is straight and gradually tapering, and is perfectly circular in transverse section” (Leidy, 1856, p. 12).  If I interpret his words properly, he saw two small holes on the interior of the specimen.  He remarked on the “ridges” and noted that sometimes they joined to create a single one.

He considered these fossils to be “ichthyodorulites,” a nifty catch-all classification for fossils of detached elements, such as spines, dermal parts, and other growths presumably coming from cartilaginous fishes such as sharks and chimaeras.  Though a much more scientific name than, say, “Miscellaneous Stuff,” it apparently fell out of favor after the early 20th Century.  (Chimaeroids, also known as rabbitfishes or ghost fishes, are truly bizarre with very evident evolutionary roots in the Carboniferous Period.)

Leidy named the fish from which he presumed these ichthyodorulites to have come Cylindracanthus ornatus.  He married the Greek word root cylindro (a "roll" or "cylinder") with either word root anthus ("flower") or, perhaps, canth ("corner of the eye"), I don’t know which.  Given the awkwardness of the resulting combination, I may have the second root wrong.

Or, we can begin this story by taking a decade-long step back and join Agassiz in the mid 1840s as he publishes the fifth volume of his monumental Recherches sur les Poissons Fossiles (Agassiz, 1843).  In it, he described some Early Eocene fossil fragments as “elongated beaks” with a channel running the length of the interior, and named their genus Coelorhynchus.  Clearly, he stated, these belonged to the Xiphiidae Family (swordfish) and he identified two species C. rectus and C. sinuatus.  Agassiz’s choice of the generic name is nicely appropriate – the word root coelo means “hollow” in Greek, and rhynchus is “snout” or “beak.”

Or, there still another choice, begin with naturalist Michel Esprit Giorna of Turin who, in 1805, named an extant genus of bony fish (not my fossil) as Coelorhynchus (see Leriche, 1906).  Though Giorna had best reside in the background for awhile (as he did in actuality), under taxonomic protocols, even those applicable at the time, Agassiz’s name for this fossil was preoccupied and, so, invalid.  But, if no one is paying attention, if the venue is obscure enough . . . .

Does a tree falling in the woods . . . ?

Instead, Agassiz and Leidy seem to demand attention first.  Agassiz, I know, would want it that way.

Leidy’s description had appeared in February, 1856.  Agassiz moved quickly and, by December, Leidy published a second comment on these fossils.  In his typical, gracious fashion, Leidy eschewed controversy, as, indeed, he actually should have:
The fossil fragments of long, conical bones, which I supposed to be portions of the dorsal spine of a fish, Prof. Agassiz informs me he considers to be the snout of a peculiar genus of sword fishes, which he has incidentally mentioned in the Poissons Fossiles, under the name of Coelorhynchus.  The correctness of this view I do not hesitate to admit, and it appears to receive confirmation by the inspection of a figure which I have since observed in Dixon's Geology of Sussex, representing the snout with its free extremity perfect.  (Leidy, 1856, p. 302)
Apparently, when he published his initial comment, Leidy hadn’t been keeping up with his reading.  Not only, as Leidy himself noted, had English doctor and naturalist Frederick Dixon published (posthumously) several drawings of Coelorhynchus rectus in 1850 (see pictures below, Dixon, 1850), but English paleobotanist W. C. Williamson had, one year earlier, described Coelorhychus at some length (Williamson, 1849).




Williamson is important to the story because he was the first to introduce a completely different notion from Agassiz’s about what these fossils were.  They had never been true bone, he hypothesized, but rather were dermal teeth-like structures.  In questioning the exact nature of what he had in hand, he would be just one of many over the years.  "The true nature of the appendage itself, as well as that of the fish to which it belongs, is yet uncertain . . . .” (Williamson, 1849, p. 472)

English paleontologist Sir Arthur Smith Woodward took up Williamson’s hypothesis and joined the debate over the origins and function of these objects.  In at least two works (Woodward, 1888 and 1891), he argued that the Coelorhynchus “spines” were “dermal in nature” and “probably occupied a forward position upon the back . . . .”  (Woodward, 1888, p. 223, 225)  The animals responsible for these “spines” had an affinity to either sharks or chimaeroids.  He favored the latter.

All the while, Giorna and his Coelorhynchus waited.  Actually, Woodward did look askance at the name Agassiz had given these fossils, not because it violated some taxonomic rule, but, rather, as I read his comment, he thought the name was inappropriate because this wasn’t a snout or beak (Woodward, 1888, p. 226).

A century of silence on the name front was broken by Maurice Leriche, a professor of geology at the University of Brussels, who, in a 1906 treatise, declared that Giorna’s prior use of the name meant Coelorhynchus could not be retained for the fossils at hand (Leriche, 1906).  He proposed a new genus name, Glyptorhynchus.  The Greek root glypto means “carved” or “engraved.”   Coupled with rhynchus (“snout” or “beak”), Giorna brought another nice name into play.

Unfortunately, in correcting one error, Leriche committed another.  Leidy’s name, Cylindracanthus, should have taken precedence.  Soon enough, though, he recognized his mistake and, in print a couple of years later, resurrected the name Cylindracanthus for the genus.

Over the course of the next century and more, the name game took back seat to somewhat infrequent consideration of the more fundamental questions of what these structures had been in life, what organism did they come from, and where did this organism fit into the scheme of things?

In 1911, Henry Fowler of the Academy of Natural Sciences of Philadelphia wrote of the genus that “[i]ts true position must still be considered doubtful” (Fowler, 1911, p. 141).  Nevertheless, Agassiz’s contention that Cylindracanthus’ affinities lay with the swordfish (within the Order Perciformes, including the so-called “billfishes”) was buttressed by several papers from the early part of the 20th Century (ones that I’ve been unable to lay my hands on and so are not listed below).  Specifically, they posited that Cylindracanthus was related to the fossil Blochiidae Family of billfishes.

When, in 1974, biologist Harry L. Fierstine of California Polytechnic State University, San Luis Obispo, went over the fossil record of billfishes, he came out against the notion that these objects had any tooth-like features or functions, since none had ever been found with teeth.  Rather, they were, he thought, likely to turn out to be “fin spines,” not rostral spines, because there were just too many of them “in the fossil record for each to represent an individual fish” (Fierstine, 1974, p. 43).

Some 20 years later, a specimen found in a Cretaceous formation in South Dakota did, indeed, have teeth, a find that prompted David C. Parris of the New Jersey State Museum and his colleagues in 2001 to re-examine many of the other Cylindracanthus fossils in the fossil record.  There they saw plenty of signs of teeth.  These were rostral projections but, according to Parris, the evidence of when Cylindracanthus first appeared in the fossil record and its cartilaginous nature showed that it was not related to billfishes.  Rather, he posited that Cylindracanthus was akin to sturgeon-like fishes (Acipenseriforme Order) (Parris, 2001).

I find it interesting that in the 21st Century we may still have taxonomic trees falling in the woods with no one to hear them, particularly when one of them (the “tree” that follows) threatens to undo the entire story told so far.

In 2005, Kenneth Monsch of the University of Wrocław, Poland, published a full revision of the fossils of the scombroid (mackerel-like) fishes which include billfishes.  In doing so, he had to decide whether and where the Cylindracanthus might fit among these fishes.  Like Parris, he rejected its placement with the billfishes.  But, after reviewing the research, he leveled a shot right at the heart of this taxonomic story.
The present author is particularly concerned about 'rostrum'-based taxa such as Cylindracanthus; he is uncertain if these can really be assigned to teleosts [largest group of extant ray-finned bony fish] or even to fish at all (Monsch, 2005, p. 484).
Not fish?

At this stage in the story, people apparently are speaking past each other.

Monsch made no reference to Parris’ 2001 paper that had come out four years earlier, an omission that probably would not have surprised Parris.  In a 2007 piece, Parris noted that the 2001 hypothesis about the placement of Cylindracanthus had “not been further commented upon by other authors, to our knowledge.”  (Parris, 2007, p. 100)  He, in turn, did not cite Monsch’s 2005 study.

And so it goes.

But, I still have to ask, what’s residing in my collection?


Sources

Agassiz, Louis.  Recherches sur les Poissons Fossiles, volume 5, 1843.

Dixon, Frederick.  The Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex, 1850.

Fallaw, Wallace.  Cylindracanthus From the Eocene of the Carolinas.  Journal of Paleontology, volume 38, number 1, January 1964, p. 128-129.

Fierstine, Harry.  The Paleontology of Billfish -- The State of the Art.  In Proceedings of the International Billfish Symposium, 1974, p. 34-44.

Fowler, Henry W.  A Description of the Fossil Fish Remains of the Cretaceous, Eocene and Miocene Formations of New Jersey.  Geological Survey of New Jersey, Bulletin 4, 1911.

Leidy, Joseph.  Description of two Ichthyodorulites (February), Remarks on certain extinct species of Fishes (December).  Proceedings of the Academy of Natural Sciences of Philadelphia, volume VIII, 1856, published 1857, p. 11-12, 301-302.

Leriche, Maurice.  Contribution a L'Étude des Poissons Fossiles du Nord de la France et des Régions Voisines.  Mémoires de la Société Géologique du Nord, volume 5, 1906.

Monsch, Kenneth A.  Revision of the scombroid fishes from the Cenozoic of England.  Transactions of the Royal Society of Edinburgh:  Earth Sciences, volume 95, 2005, p. 445-489.

Parris, David C., et al.  Reassessment of the Affinities of the Extinct Genus Cylindracanthus (Osteichthyes).  Proceedings of the South Dakota Academy of Science, vol. 80, 2001, p. 161-172.

Parris, David C., et al.  Fossil fish from the Pierre Shale Group (Late Cretaceous):  Clarifying the biostratigraphic record.  The Geology and Paleontology of the Late Cretaceous Marine Deposits of the Dakotas:  Geological Society of America Special Paper 427, 2007, p. 99-109.

Williamson, W.C.  On the Microscopic Structure of the Scales and Dermal Teeth of Some Ganoid and Placoid Fish.  Philosophical Transactions of the Royal Society of London, 1849, p. 435-475.

Woodward, Arthur Smith.  On the fossil Fish-spines named Coelorhynchus, Agassiz.  The Annals and Magazine of Natural History, Including Zoology, Botany, and Geology, volume II, 1888, p. 223-226.

Woodward, Arthur Smith.  Catalogue of the Fossil Fishes in the British Museum (Natural History), part II, 1891.

4 comments:

  1. Dear Tony,

    Here's Ken Monsch; I've found your blog by accident, but I'm glad I've found it. To be honest, I was completely unaware of Parrish' works that mention Cylindracanthus. I did not intentionally ignore those works. I'll have a look at Parish' papers. More about Cylindracanthus: please check Stevens et al. (2011) in Neues Jahrbuch Geol. Palaont. Abhandlungen 260 (3): 289-296. If you wish, you can reach me at kenneth.monsch@ncbnaturalis.nl

    ReplyDelete
  2. Ken:
    Thanks for your generous comment. I will follow up on your lead.
    Tony

    ReplyDelete
  3. Enjoyed the blog, Tony. I've shared it with Facebook Ichthyolith Issues. 'Acanthus' a spine as in many other "ichthyodorulites". Has anyone done any proper histological analysis to see if these fossils are indeed bone and or dentine?

    ReplyDelete
    Replies
    1. Glad you liked it. I finally had a moment to go back through some of the papers I have on the Cylindracanthus and I don't see any such analysis. Parris reported that he found teeth, a finding which appears to have been based on the morphology of the structures he so identified.

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