Sunday, January 1, 2012

Index Fossils of North America

One of the highs in my 2011 was the surprise gift of a copy of Index Fossils of North America by Hervey Woodburn Shimer and Robert Rakes Shrock.  It came wrapped with the exhilaration always associated with the addition of a long-sought volume to my book collection.  This magisterial compilation of descriptions and images of mostly index fossils, first published in 1944 and reprinted many times, though no longer in print, offers a fossil collector of my ilk an almost unparalleled resource for identifying invertebrate specimens and getting oriented for further research.  Is the content showing some age?  Sure, but that’s true for me, too.

Upon first opening this book, I followed up on a comment left to a recent posting on this blog about surface patterns on the Eodictyonella brachiopod.  The commenter directed me to similar patterns on the Permian brachiopod Waagenoconcha montpelierensis Girty as shown in several images in Index Fossil of North America.  There they were . . . spot on.

My second exploration was prompted by randomly thumbing through the book (the work invites that kind of relaxed interaction) and stumbling upon images of Micrabacia corals.  I have a couple of specimens of this kind of solitary coral in my collection and the book’s description of the genus, though terse, was precise.  (In this case, a solitary coral is a very small button-like object.)  More impressive to me was that Shimer and Shrock’s photographs, and associated annotations, of the various Micrabacia coral species made it clear that I had these tiny coral upside down in the pictures I’ve taken and in how I placed them in a display case.  The picture below corrects that and honors my tidbit of new knowledge.  (I’ve left the label in the picture uncertain as to species because Shimer and Shrock seemed to be steering me to Micrabacia cribraria, while the guide I have to material from the Chesapeake and Delaware Canal where this specimen was found pointed to M. hilgardi.  Ah, more research.)

The Index Fossils of North America has a worthy pedigree.  In 1937, a young Robert Shrock (1904 – 1993) joined the geology faculty at the Massachusetts Institute of Technology (MIT) which featured, among its luminaries, Hervey W. Shimer (1872 – 1965).  Shimer’s “fame throughout North America was based largely on the five books he wrote alone or with others – books that played an important role for more than half a century in the training of geology students.”  (Shrock, Geology at MIT 1865 – 1965, 1982, p. 43.)  Trained at Columbia University, Shimer began his teaching career at MIT in 1903, becoming full professor in 1922.  He would be on the faculty for four decades, retiring as professor emeritus in 1942.  The first of the five books upon which his reputation rested was the nearly 1,800 page-long, two-volume North American Index Fossils, coauthored with Columbia University professor Amadeus William Grabau (1870 – 1946) and published in 1909 and 1910.

Soon after his appointment to the MIT faculty, Shrock assumed major responsibility for rethinking and rewriting Grabau and Shimer’s North American Index Fossils.  He and Shimer took seven years to rework the opus, publishing it in 1944, two years after Shimer’s retirement.  So the Index Fossils of North America became the fifth and last of Shimer’s major books and was subtitled A New Work Based on the Complete Revision and Reillustration of Grabau and Shimer’s “North American Index Fossils.”  This single volume came in at over 800 pages with, according to a 1943 advertisement in Science, 8,000 illustrations and descriptions of 7,500 species.  Surely an exaggerated count of illustrations and descriptions, but you get the idea.  (By the way, though he gave it a good try, Shrock just missed surpassing Shimer in terms of longevity on the MIT faculty.  He was made professor emeritus in 1970, 33 years after his initial appointment, and then stayed on for 5 more years as a senior lecturer.  (Robert Shrock, 88, Fossil Expert, The New York Times, obituary written by Wolfgang Saxon, June 23, 1993.))

The central focus of the Index Fossils of North America, like that of its two-volume predecessor, is on the identification of index fossils which the authors defined as follows:  “A genus which has a narrow stratigraphic range and rather broad geographic distribution is now considered an index fossil.”  (p. 1)  In other words, these fossil genera or species are relatively short-lived (as genera or species) and closely associated with specific rock formations while, at the same time, being found in many places.  As a result of these attributes, index fossils, according to Shimer and Shrock, “can be used to identify and date formations and to correlate them from one area to another.”

The book may serve me well because I think the authors subtly shaped elements of it to assist the geologists into whose hands the book was destined to fall.  The non-paleontological users would need that assistance in order to identify fossils, otherwise they wouldn’t attain the goal of identifying, dating, and correlating formations.  For example,  Shimer and Shrock included some genera that appear over broad ranges of time (i.e., they have “long vertical ranges”) simply because they are common, not because they could serve as index fossils.  They argued, “The investigator should know what is useless and not send such material to specialists.”  Hmmm, shielding the paleontologically knowledgeable from some geologists (?) who might be less so?  Tension between the fields?

Perhaps I’m reading more into this than it merits or misreading it altogether, but in fact there were some particular strains in the relationship between paleontology and geology in this period.  As David Sepkoski, historian of science at the University of North Carolina, Wilmington, outlined in his account of the development of paleobiology, the 1940s into the 1960s witnessed a debate over the fit of paleontology with geology.  (The Emergence of Paleobiology, in The Paleobiological Revolution:  Essays on the  History of Recent Paleontology, 2009.)  He noted that J. Brookes Knight in his 1946 presidential address to the Paleontological Society urged his colleagues to free themselves from subservience to geology and turn toward biology.  Of course, there was pushback from within and outside the paleontology ranks.

I would guess some hostility might have flowed in the opposite direction, from geologists toward paleontology, prompted by the way some of them were taught about . . . wait for it . . . index fossils.  As Alan Shaw wrote in Time in Stratigraphy (1964) (as quoted by Donald R. Prothero in Bringing Fossils to Life (1998), p. 182):
It would be difficult to estimate how many nascent geologists have been turned aside from paleontology by being forced during the course of some dismal semester to learn hundreds of index fossils and the formations of which they are the index.  Many geologists’ sole memory of the whole discipline of paleontology is the unerasable fact that “Spirifer grimesi is the index fossil of the Burlington Limestone” or some such tidbit.
Thank God, I’m not using this wonderful book that way.

1 comment:

  1. Thanks for writing about this topic. It inspired me to create a blog posting related to the reference book you mention. Find at Louisville Fossils Blog


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