Book Review: Fossils of the Upper Ordovician Platteville Formation in the Upper Midwest USA: An Overview
This may be the book with the longest title that means the least to the layperson of any book I’ve ever read. But what Dennis R. Kolata lacks in whipping up a snappy title he more than makes up for in delivering a thorough catalog of the life forms that rooted or scooted around in the vast sea off the coast of Laurentia 450 million years ago. Kolata, a 30+-year staffer at the Illinois State Geological Survey, not only authored this work but also loaned his considerable talent as an visual artist to several illustrations, including the cover art shown above.
Words and pictures combine to describe the long-vanished denizens of the late Ordovician (~458.4 Ma to ~443.8 Ma). Kolata catalogs the fossils of the Platteville by phylum, starting with the poriferans (sponges) and ranging through the echinoderms (starfish, crinoids) before ending with chapters on miscellaneous macrofossils, miscellaneous microfossils and trace fossils. True confession: trace fossils don’t particularly interest me, which tarnishes my paleontological bona fides a bit; I’m more interested in the fossilized remnants of the dead critters than I am in the burrows they called home or the tracks they left as ate and mated their way across the seafloor. Hey, we all have our weaknesses.
In the book, on the other hand, I found no weaknesses. The volume itself is a handsome hardback printed on high-quality glossy paper, which ensures that the images of the fossils in the numerous pages of photographic plates are clear and detailed—so detailed, in fact, that one of the foundational stories of my fossil fascination had to be rewritten thanks to an image on page 168. My midlife rockhounding rebirth occurred on the morning of April 4, 2021, when, on a hike, I looked down and saw what, out of the corner of my eye, looked like the soleprint of a shoe. From somewhere in the back of my brain came the voice of my eight-year-old self, and following the urging of the kid in me, I went back and took a better look. I’ll be damned! It was a trilobite fossil! And not just any trilobite fossil—a whole, complete (well, maybe complete, the head was covered by matrix) trilobite the size of the palm of my hand. Oh, happy day! Oh, joyous moment! Oh, the places I would go and the things I would do thanks to this unlooked-for discovery on an April morning! Trilobite, my trilobite, you reopened the world of the past into my present, and life has not been the same since.
Lovely story . . . except that, ahem, what I found was not a trilobite. A few days shy of the 3-year anniversary of the find that started my geologic madness, I was making my way through “Chapter 11 – Nautiloid Cephalopods” when I stumbled on the photo of a fossil of Gonioceras occidentale, a member of order Actinocerida within the Actinoceratoidea subclass that was not of phylum Arthropoda but was of phylum Mollusca—and was a virtual twin of the “trilobite” holding pride of place in my display case. Kolata’s description of the species at least made me feel a bit better for being fooled for the past three years:
Moderately large, straight, rapidly expanding smooth shell, strongly depressed in cross section with ventral side flat to slightly convex and dorsal side fully convex; both sides meet laterally at an acute angle; aperture contracted; septa deeply concave, closely arranged, septal sutures curve strongly downward toward the apex along the longitudinal axis of the venter and dorsum, then curve abruptly upward before reversing direction again along the flanks, producing an overall distinct trilobate pattern. (167; emphasis mine)
If Kolata’s thousand words don’t paint the picture in your mind’s eye, you can take a look at this photo of the photo in the book and my fossil side by side. I’m clearly not ready to be a curator, but at least I got the trilobate pattern right. And, my little Gonioceras occidentale, I still love you as much as ever. Now every time I find a cephalopod, I think of you.
One other feature of the work I found especially helpful is the “Remarks” section that follows the “Description” section for most species. In this section, Kolata often provides correlates with roughly contemporaneous Ordovician strata in other regions where these same fossils have been found, including various “hometown” Tennessee layers with which I’m familiar (e.g., the Lebanon Limestone, the Carters Formation). This section is usually followed by an “Occurrence” section that details locations and Upper Platteville Formation members in which each species has been found. Unfortunately for me, many of the locations where Kolata and others collected the specimens in the photos are quarries which are, for the most part, off-limits to lay collectors. But I’m a pretty decent scavenger of road cuts, and between Kolata and Agate Dad, I think a road trip through Illinois, Wisconsin and Minnesota may be in the offing for late summer. I’ll definitely make use of Fossils of the Upper Ordovician Platteville Formation to guide my travels.