Wooster’s Fossil of the Week: A pentamerid brachiopod from the Lower Silurian of New York

Pentamerus oblongus Sowerby, 1839Another brachiopod this week. This simple fossil is an internal mold of the brachiopod Pentamerus oblongus (J. de C. Sowerby, 1839). It was a very common and widespread taxon throughout North America and Europe in the Early Silurian. This particular specimen was found in a dolomite of the Clinton Group of New York State. This species has been an important fossil for reconstructing Early Silurian paleocommunities, and it is useful in biostratigraphy as well.

I chose this specimen because it has the preservation I have seen in almost every pentamerid brachiopod I have collected: it is an internal mold formed when sediment filled the calcitic shell, was cemented, and then the shell dissolved. We are looking at an impression of a sort of the interior surface of the brachiopod. The posterior (hinge region) of the brachiopod is at the top of this view. You can see a straight slit that represents the ventral muscle field complex (spondylium) that was part of the ventral valve. This was a kind of shelly septum on the floor of the brachiopod interior. we would not see this feature (or rather what is left of it) if the exterior shell had not been removed.
Pentamerus_drawingThe above is a drawing of Pentamerus oblongus as it looked with its original shell. In this view, unlike our specimen, we are looking at the dorsal valve with the ventral valve visible beneath it.
James_d_c_SowerbyThe genus Pentamerus was named in 1813 by James Sowerby (1757-1822), a prolific scientist we met earlier with our specimen of the Cretaceous bivalve Inoceramus. The species Pentamerus oblongus was fittingly named by his eldest son, James de Carle Sowerby (1787-1871), in 1839. J. de C. Sowerby is shown above in his latter years. The younger Sowerby was an unusual combination of a paleontologist, botanist and mineralogist. He was a friend of the extraordinary scientist Michael Faraday (1791-1867), so he would have had encouragement to be an accomplished polymath. He is said to have conceived one of the first classification of minerals by their chemical compositions. In 1838, J. de C. Sowerby and his cousin Philip Barnes founded the Royal Botanic Society and Gardens (now part of Regent’s Park, London). On top of all this, he was a spectacular scientific illustrator. How many such diverse scientists do we have today?


Johnson. M.E. 1977. Succession and replacement in the development of Silurian brachiopod populations. Lethaia 10: 83-93.

Johnson, M.E. and Colville, V.R. 1982. Regional integration of evidence for evolution in the Silurian Pentamerus-Pentameroides lineage. Lethaia 15: 41-54.

Ziegler, A.M., Cocks, L.R.M. and Bambach, R.K. 1968. The composition and structure of Lower Silurian marine communities. Lethaia 1: 1-27.

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Keck Symposium Warmup for Wooster’s IS Symposium

Wooster’s Senior Research Symposium is exactly a week away, so many seniors will be spending this weekend practicing their poster presentations. Two senior Wooster Geologists have had a recent poster presentation warmup; In early April, Anna Mudd (’13) and Joe Wilch (’13) presented their Independent Studies at the 26th Annual Keck Symposium. The Keck Geology Consortium provides opportunities for Wooster geologists to work on a variety of projects with faculty and students from many other institutions. Keck projects involve an intense four-week summer experience followed by a year-long guided research project at the home institution. The symposium represents the culmination of the project, bringing the Keck team back together to synthesize their results and present their work.

This year, Anna worked on the Northeast Oregon project. She studied the clay mineralogy of paleosols in the Powder River volcanic field. By identifying the clay species, she was able to interpret the climate at the time of soil formation, approximately 14 million years ago.

Anna Mudd ('13) presented her work on paleosols in the Powder River volcanic field.

Anna Mudd (’13) presented her work on paleosols in the Powder River volcanic field.

While Anna was in Oregon, Joe  was in the Northern Snake Range in Nevada. He used 40Ar/39Ar thermochronology of muscovites and K-feldspars to understand how the footwall of a detachment fault was exhumed.

Joe Wilch ('13) presented his work on the thermochronology of muscovites and K-feldspar in the Snake Range.

Joe Wilch (’13) presented his work on the thermochronology of muscovites and K-feldspar in the Snake Range.

Best of luck to Anna, Joe, and the other geology seniors who will be presenting their research next week. If you’re in the area next Friday, you should definitely try to make it to the symposium. Most of the geology posters will be in the Writing Center in Andrews Library between 1 and 3 pm. Joe’s poster will be presented with the mathematicians on the third floor of Taylor between 9 and 11 am.

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Wooster’s Fossil of the Week: A terebratulid brachiopod from the Middle Triassic of southern Israel

Coenothyris oweni Anisian 041013 585Sure, I could have picked a pristine shell from our collection, but I like the rugged character of this one. It is the terebratulid brachiopod Coenothyris oweni Feldman, 2002, from the lower Saharonim Formation (Middle Triassic) of Har Devanim, southern Israel. I picked it up, along with a dozen others, during our 2010 Israel expedition.

Above we have a dorsal view of this brachiopod. The posterior is at the top, anterior at the bottom. The round hole is the pedicle opening in the ventral valve. (The pedicle is a fleshy stalk the brachiopod uses to attach to a substrate.) As with all brachiopods, you can see the bilateral symmetry of the shell with the plane perpendicular to the hinge between the valves. Terebratulids are still around.


The layered units at the top of this ridge of Har Devanim are the lower part of the Saharonim Formation (Anisian, Middle Triassic). Micah Risacher (’11) is just visible.


Coenothyris oweni was named in 2002 by my friend Howie Feldman. He also wrote a 2005 paper on the paleoecology of this species in the Saharonim Formation of southern Israel. The brachiopods are sometimes found in obrution deposits, meaning they were buried alive by storm-driven sediments (see above).


The genus Coenothyris was named by Joseph Henri Ferdinand Douvillé in 1879 (above as a young man and older). He was a French paleontologist and geologist who worked first as a mining engineer and then a professor of paleontology at the École des Mines (School of Mines). His research took him around the world, but his most prominent papers were on French fossils and geology. In 1881 he became president of the Société géologique de France; in 1907 he was elevated to the Académie des Sciences.


Feldman, H.R. 2002. A new species of Coenothyris (Brachiopoda) from the Triassic (Upper Anisian-Ladinian) of Israel. Journal of Paleontology 76: 34-42.

Feldman, H.R. 2005. Paleoecology, taphonomy, and biogeography of a Coenothyris community (Brachiopoda, Terebratulida) from the Triassic (Upper Anisian-Lower Ladinian) of Israel. American Museum Novitates, no. 3479: 1-19.

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Expanding Your Horizons in Geology

Wooster, OH – The Wooster X-ray Lab hosted girls from the Expanding Your Horizons program, a series of workshops aimed at encouraging young women to pursue careers in the sciences. The geology workshop focused on minerals and their wide variety of uses. One popular use of minerals is in beaded jewelry.

These colorful beads are made of minerals.

These colorful beads are actually polished pieces of minerals.

Our goal was to figure out which minerals each bead represented. To do this, we used the X-ray Diffractometer (XRD).  The XRD zaps the minerals with X-rays, which get reflected off of the atomic layers in the minerals, giving us information about their structures. Each mineral has a unique set of reflections, sort of like a fingerprint, which allows us to identify the mineral.

One of the girls prepares a sample for the XRD.

One of the girls prepares a sample for the XRD.

While we were waiting for the samples to run, the girls made bracelets out of the beads.

While we were waiting for the samples to run, the girls made bracelets out of the beads.

Someone made a bracelet that said, "Science Rocks!"

Someone made a bracelet that said, “Science Rocks!” We love the geology pun.

By the end of the workshop, we learned that three of our beads were actually varieties of quartz: Tiger’s Eye Quartz, Amethyst, and Jasper. Our dark blue bead was Sodalite. Maybe the most surprising result was the bead that looked like Turquoise. It was actually Calcite!  Tricky, tricky!




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Virtual Cascades Volcano Observatory in Wooster

Wooster, OH – We hosted a virtual visitor in today’s GeoClub seminar. Dave Ramsay, a geologist from the Cascades Volcano Observatory, connected with us via the web to tell us about the geology of Crater Lake.

Shelley Judge and Dave Ramsey bumped into eachother at the conference on Volcanism in the American Southwest. Both are alumni of the same undergraduate geology program!

Shelley Judge and Dave Ramsey bumped into eachother at the conference on Volcanism in the American Southwest. Both are alumni of the same undergraduate geology program!

Dave and his colleagues have done fantastic work mapping the floor of Crater Lake. Crater Lake formed from the explosive eruption of Mount Mazama about 7700 years ago. On most geologic maps, Crater Lake is a blue body of water. But Dave and his colleagues used multibeam swath echo sounders and a human occupied submersible to map the geology of the lake floor.

Map of Crater Lake showing features of interest on the lake floor. Klimasauskas, E., Bacon, C., and Alexander, J., 2002, Mount Mazama and Crater Lake: Growth and Destruction of a Cascade Volcano: U.S. Geological Survey Fact Sheet 092-02.

Dave took us on a fly-through tour of the geology and told us stories about how many of the geologic features developed. He and his colleagues found that Wizard Island is much bigger than we may have expected, and that it erupted both under and above water while Merriam Cone erupted exclusively under water.

Snapshot of the geology of the floor of Crater Lake.  Here, Wizard Island (gray peak) extends below the water (green). (Photo Credit: David Ramsey).

Snapshot of the geology of the floor of Crater Lake. Here, Wizard Island (gray peak) extends below the water (green). (Photo Credit: David Ramsey).

Many thanks to Dave for talking to us first thing this morning (west coast time) and for giving such an engaging and entertaining seminar.



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Wooster’s Fossil of the Week: A camerate crinoid from the Lower Carboniferous of north-central Ohio

Cusacrinus_daphne033013Visitors often bring rocks and fossils to the Geology Department for identification. We love to solve the puzzles (or at least make the attempt), and our new friends appreciate names and ages for their treasures. (Usually. We’ve disappointed more than a few finders of “meteorites”.) Last week a home-schooling group came in from nearby Ashland with a tray of stones they found in a stream bed eroding an exposure of the Lower Carboniferous (Kinderhookian) Meadville Shale Member of the Cuyahoga Formation. One of the objects was the spectacular fossil shown above.

This is a calyx and the attached arms (essentially the “head”) of a camerate crinoid known as Cusacrinus daphne (Hall, 1863). (Our friend Bill Ausich of Ohio State University provided the identification — these crinoids are his speciality.) It is preserved as an external mold, meaning that the actual skeleton was covered in sediment (or in this case a concretion) and then dissolved away, leaving a cavity showing a mold of its exterior details. It is a rare fossil to find in our part of the world.

CrinoidCalyx033013Above is a close-up of the calyx of Cusacrinus daphne (Hall, 1863). Note the radiating ridges on the exteriors of each thecal plate. They are characteristic of this species.

CrinoidArms033013These are some of the arms of the crinoid. They are complex because each arm is lined with tiny branches called pinnules, making feather-like extensions for filter-feeding.

Thank you to our new Ashland friends for sharing such a beauty with us!


Ausich, W.I. and Roeser, E.W. 2012. Camerate and disparid crinoids from the Late Kinderhookian Meadville Shale, Cuyahoga Formation of Ohio. Journal of Paleontology 86: 488-507.

Kammer, T.W. and Roeser, E.W. 2012. Cladid crinoids from the Late Kinderhookian Meadville Shale, Cuyahoga Formation of Ohio. Journal of Paleontology 86: 470-487.

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Wooster’s Fossil of the Week: A pretty little fish from the Eocene of Wyoming

Knightia_eocaena_033013_585Most people have seen this fossil fish type. Geologists, in fact, have probably seen Knightia eocaena Jordan, 1907, thousands of times. It is present in nearly every gift shop that sells fossils, usually as small plaques or glued to refrigerator magnets. It is the state fossil of Wyoming and, by all accounts, the most numerous fossil fish in the world. In fact, it is likely the most common vertebrate fossil ever. It is thus no surprise that Wooster has dozens of specimens, most of them donated by students and alumni.

Knightia lived in freshwater lakes throughout western North America during the Eocene. It is closely related to herring and sardines, and almost certainly had similar life habits. We know that it lived in large schools, and we suspect it had a diet of phytoplankton and insect larvae. It was low on the ecological food chain, just like its modern cousins, and so was an important food source for all sorts of larger fish, reptiles, birds and mammals.
MeagensFish585We tend to see most often beautifully preserved, complete Knightia specimens like the one at the top of the page. This is because if a fossil is very common, collectors can afford to keep only the best specimens. It is fun, though, to see what the average Knightia looks like in the fossil record. Above is a specimen collected by our petrologist Meagen Pollock from an outcrop in Wyoming. Note that the fish are contorted and often overlapping — specimens that are usually discarded by collectors. This slab shows better that these fossils occur in vast, complicated, messy death assemblages, probably because of volcanic ash falls or quick changes in lake chemistry.
Knightia_BW_TamuraThis is a digital reconstruction of Knightia (© N. Tamura). Note the deeply forked tail and flattened top of the head.

Dsjordan_wikipediaKnightia was named in 1907 by the accomplished and very problematic David Starr Jordan (1851-1931). Jordan was a well known fish expert, having been inspired by the iconic ichthyologist Louis Agassiz himself. He taught at several colleges and universities, eventually serving as president of Indiana University (at 34, the youngest university president at the time) and as the first president of Stanford University. He was a very successful university president, especially in the first years of Stanford.

But, but … David Starr Jordan was also a eugenicist, believing in compulsory sterilization of the “unfit”. On the bright side (if there is one here), he opposed war because it tended to kill the most fit members of society. Jordan also shockingly covered up the apparent murder of Jane Stanford, co-founder of the university, in 1905. Jordan does not look good at all in that story, most of which was sorted out only about ten years ago. Who would have guessed that a murder mystery could lurk in the taxonomic history of these pretty little fish?


Grande, L. 1982. A revision of the fossil genus Knightia, with a description of a new genus from the Green River Formation (Teleostei, Clupeidae). American Museum Novitates 2731: 1-22.

Jordan, D.S. 1907. The fossil fishes of California; with supplementary notes on other species of extinct fishes. Bulletin, Department of Geology, University of California 5:136.

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The field trip scout

MeadvilleLodi033013WOOSTER, OHIO–One of the early spring pleasures of a geologist in the Upper Midwest is finally getting outside and scouting the field trips for the semester. Today we had bright sun and temperatures in the 50s (I know — I’m settling) so I went out to plan the late April field trip for my sedimentology and stratigraphy class. The sites I’ve been using in the last few years have become too overgrown, so it is time to find new projects in new places. Since the delightfully underbrush-free Mojave Desert is too far away, I’m looking at places in northeastern Ohio. It was a fun day.

Above is an outcrop of the Meadville Shale Member of the Cuyahoga Formation (Lower Carboniferous, late Kinderhookian) exposed in the Lodi Community Park about 20 miles north of Wooster. A tributary of the Black River (the East Fork Black River) flows through a small valley, exposing the shale in its cutbanks. I’m a bit partial to this location because from here a fellow Wooster student found a trilobite that became the basis of my first scientific publication. The unit here is moderately fossiliferous and contains numerous rock types besides shale. It will make a fine place for students to measure and describe stratigraphic sections next month. It certainly was a beautiful place to spend a sunny Saturday morning.

TurkeyVulture033013There were many turkey vultures (Cathartes aura) perched in the still-leafless trees in northern Wayne and southern Medina Counties. Here’s one keeping an eye on me. Turkey vultures are a sign in Ohio that spring really is coming (even if it is supposed to snow tomorrow morning!).

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Dr. Michael Mann visits Wooster

MichaelMann032713WOOSTER, OHIO–We were honored this week when Dr. Michael E. Mann, one of the world’s foremost climate-change experts and a leader in the efforts to educate the public about anthropogenic effects on the atmosphere, came to Wooster as part of our Richard G. Osgood, Jr., Memorial Lecture series. He gave a public lecture in the nearly-full Gault Recital Hall Wednesday evening (“The Hockey Stick and the Climate Wars: Dispatches from the Front Lines”), and then a Geology Club lecture the next day in Scovel (“The Past as Prologue: Learning from the Climate Changes in Past Centuries”). Students, faculty and staff of the Geology Department also had a wonderfully informative dinner with him in the Wooster Inn.

Michael Mann is very well known in the diverse community that studies climate change in the past, present and future. He was the senior author of a pivotal article in the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report in 2001. It set the direction for more than a decade of later climate research. He has written dozens of other papers and two books on climate change. He has received numerous awards, most recently the Hans Oeschger Medal of the European Geosciences Union.

The public Osgood lecture Dr. Mann presented on Wednesday was centered on his latest book. He described the recent scientific history of climate change research and then how he became an “accidental public figure” through the famous “Climategate” theft and publication of private email messages. His stories of attempted congressional interference in his work and that of other climate scientists were astonishing, representing what he calls “the scientization of politics” (where science — or pseudoscience — is used as a political tool).

The image at the top of the page is Dr. Mann near the end of his Osgood Lecture. The image on the screen is of his daughter enjoying a moment in the polar bear pool at the Pittsburgh Zoo and PPG Aquarium. He fears that someday such animals will be found only in zoos because humans “melted their Arctic environment.” Numerous questions and conversations followed.
MannLecture032813Dr. Mann gave a Geology Club presentation this morning in Scovel Hall on some of his scientific work (shown above). He talked about using proxies to model historical climate change and then predict future climate.
WilesMann032813For me one of the best moments was his conversation with Greg Wiles in our dendrochronology lab (above). It was great fun to see how the work of Wooster Geologists is part of the unfolding grand story of what factors control our climate, and why such research is critical in our efforts to cope with future changes.

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Wooster’s Fossil of the Week: A grazed oyster from the Middle Jurassic of Gloucestershire, England

Praeexogyra_acuminata_585This small oyster is not in itself unusual. In fact, it is one of the most common fossils in the Jurassic of western Europe: Praeexogyra acuminata (Sowerby, 1816). It may be better known by its older name: Ostrea acuminata. Local collectors call it the “sickle oyster” because of its curved shape. This specimen is from the Sharp’s Hill Formation (Middle Bathonian) exposed in the Snowshill Quarry near Moreton-in-Marsh, Gloucestershire, England. I collected it on my first trip to England in 1985.
Praeexogyra_acuminata_closerWhat attracted me to this particular shell can be seen in the above close-up: lots of little straight lines incised across its outer surface (along with a serpulid worm tube). The lines were scraped by the Aristotle’s Lantern of one or more regular echinoids (sea urchins). This is the trace fossil Gnathichnus pentax Bromley, 1975. We met this fossil last month cut into a Cretaceous oyster from Israel. One or more echinoids grazed over this Jurassic oyster, probably consuming algae and other organic materials.

Praeexogyra acuminata was an epifaunal filter-feeder, meaning it lived on the substrate sucking in seawater and sorting from it organic material for food. During the Middle Jurassic these oysters were so common that their shells formed thick deposits. It is possible that some deposits rich in these shells were formed in brackish waters rather than under fully marine conditions.

Ostrea acuminata was named by by the enthusiastic English natural historian James Sowerby (1757-1822). We met him earlier as the author of a Cretaceous bivalve genus.


Bernard-Dumanois, A. and Delance, J-H. 1983. Microperforations par algues et champignons sur les coquilles des «Marnes à Ostrea acuminata (Bajocien supérieur) de Bourgogne (France), relations avec le milieu et utilisation paléobathymétrique. Geobios 16: 419-429.

Bernard-Dumanois, A. and Rat, P. 1983. Etagement des milieux sédimentaires marins. Paléoécologie des Huîtres dans les “Marnes à Ostrea acuminata” du Bajocien de Bourgogne (France). Comptes rendus de l’Académie des sciences Paris 296: 733-737.

Hudson, J.D. and Palmer, T.J. 1976. A euryhaline oyster from the Middle Jurassic and the origin of true oysters. Palaeontology 19: 79-93.

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