Wooster’s Fossil of the Week: A stromatoporoid (Middle Devonian of central Ohio)

October 30th, 2011

Stromatoporoids are very common fossils in the Silurian and Devonian of Ohio and Indiana, especially in carbonate rocks like the Columbus Limestone (from which the above specimen was collected). Wooster geologists encountered them frequently on our Estonia expeditions in the last few years, and we worked with at least their functional equivalents in the Jurassic of Israel (Wilson et al., 2008).

For their abundance, though, stromatoporoids still are a bit mysterious. We know for sure that they were marine animals of some kind, and they formed reefs in clear, warm seas rich in calcium carbonate (DaSilva et al., 2011). Because of this tropical habit, early workers believed they were some kind of coral, but now most paleontologists believe they were sponges. Stromatoporoids appear in the Ordovician and are abundant into the Early Carboniferous. The group seems to disappear until the Mesozoic, when they again become common with the same form and life habits lasting until extinction in the Late Cretaceous (Stearn et al., 1999).

The typical stromatoporoid has a thick skeleton of calcite with horizontal laminae, vertical pillars, mounds on the upper surface called mamelons, and dendritic canals called astrorhizae shallowly inscribed on the mamelons. These astrorhizae are the key to deciphering what the stromatoproids. They are very similar to those on modern hard sponges called sclerosponges. Stromatoporoids appear to be a kind of sclerosponge with a few significant differences (like a calcitic instead of an aragonitic skeleton).

Stromatoporoid anatomy from Boardman et al. (1987).

Top surface of a stromatoporoid from the Columbus Limestone showing the mamelons.

There is considerable debate about whether the Paleozoic stromatoporoids are really ancestral to the Mesozoic versions. There may instead be some kind of evolutionary convergence between two groups of hard sponges. The arguments are usually at the microscopic level!

The stromatoporoids were originally named by Nicholson and Murie in 1878. This gives us a chance to introduce another 19th Century paleontologist whose name we often see on common fossil taxa: Henry Alleyne Nicholson (1844-1899). Nicholson was a biologist and geologist born in England and educated in Germany and Scotland. He was an accomplished writer, authoring several popular textbooks, and a spectacular artist of the natural world. Nicholson taught in many universities in Canada and Great Britain, finally ending his career as Regius Professor of Natural History at the University of Aberdeen.

Henry Alleyne Nicholson (1844-1899) from the University of Aberdeen museum website.


Boardman, R.S., Cheetham, A.H. and Rowell, A.J. 1987. Fossil Invertebrates. Wiley Publishers. 728 pages.

DaSilva, A., Kershaw, S. and Boulvain, F. 2011. Stromatoporoid palaeoecology in the Frasnian (Upper Devonian) Belgian platform, and its applications in interpretation of carbonate platform environments. Palaeontology 54: 883–905.

Nicholson, H.A. and Murie, J. 1878. On the minute structure of Stromatopora and its allies. Linnean Society, Journal of Zoology 14: 187-246.

Stearn, C.W., Webby, B.D., Nestor, H. and Stock, C.W. 1999. Revised classification and terminology of Palaeozoic stromatoporoids. Acta Palaeontologica Polonica 44: 1-70.

Wilson, M.A., Feldman, H.R., Bowen, J.C. and Avni, Y. 2008. A new equatorial, very shallow marine sclerozoan fauna from the Middle Jurassic (late Callovian) of southern Israel. Palaeogeography, Palaeoclimatology, Palaeoecology 263: 24-29.

Exploring the Silica Formation (Middle Devonian) in Northwestern Ohio

October 22nd, 2011

PAULDING, OHIO–There’s nothing like the stirring rings of 50 geologic hammers in the morning. Today I was a guest of the North Coast Fossil Club and my friend Brian Bade in a quarry exposing the Middle Devonian limestones and shales. There was frost on the ground when we began, but soon the sun rose and made it a delightful fall day of fossil collecting. Thank you to Brian and the NCFC for inviting me on their trip. I’ve spoken twice to the NCFC and they have been good friends since. It was my first visit to the highly fossiliferous Silica Formation (Middle Devonian), and I came away with a bag of treasures for my classes and research projects. Thank you also to the Lafarge Cement Quarry managers for facilitating this productive experience.

The Silica Formation is very well known for its abundant fossils, especially brachiopods, corals, trilobites, and bryozoans. I’ve wanted to examine the Silica for a long time because it has produced significant material for the hederelloid and microconchid projects I have been working on with my Polish, English and Estonian colleagues. For the first time I was able to collect my own specimens of each group, and to see the fossils in their geological context.

A quarry visit always starts with a sign-in process and a reading of the rules. Note the required reflective vests and hard hats. (I was very impressed that everyone knew my name until I realized it was emblazoned on the front of my helmet.)

A wall of the quarry. The thick gray unit is the Dundee Limestone; the thin dark sequence of mixed shales and limestones at the top is the Silica Formation. Both are Middle Devonian in age (Givetian).

Most of us figured out pretty quickly that the best places to collect fossils were in the large weathered blocks in irregular piles well away from the quarry walls. The soft Silica Formation shales erode quickly, releasing the hard calcitic fossils. Climbing around on these rocks is an acquired geological skill.

My paleontology students can tell even from this distant view what kind of coral this is in the top of the Dundee Limestone. (At least they better be able to by now!)

They can also identify the order to which this beautiful and delicate bryozoan belongs, I’m certain.

Bivalves and the spiriferid brachiopod Orthospirifer in the Silica Formation.

Finally, they tend to be overlooked in the excited search for trilobites and other shelled creatures, but there are also spectacular trace fossils in the Dundee Limestone.



Wooster’s Fossil of the Week: A tabulate coral (Middle Devonian of New York)

September 4th, 2011

This week’s specimen is from a group of fossils I gave my Invertebrate Paleontology students as “unknowns” to identify. Since it is their very first week of class I expected them to struggle, but many did remarkably well. (Congratulations to Lauren Vargo and Kit Price for correctly identifying it to the genus level, and to Lauren for hitting the species itself!)

Pleurodictyum americanum Roemer 1876 is pictured above with a view of its living surface. It is a tabulate coral belonging to the Family Favositidae, thus another type of “honeycomb coral” as we’ve discussed before on this blog. This particular species is notable because it is very common in the Middle Devonian of the northeastern United States (Pandolfi and Burke, 1989). Brian Bade collected this coral, along with hundreds of others, from the Kashong Shale exposed in Livingston County, New York. He generously donated it to the paleontological teaching and research collection at Wooster.

What is most interesting about these corals is that they are almost always found with an external mold of a elongate snail shell on the underside at their origin. The snail (more officially called a gastropod) is Palaeozygopleura hamiltoniae (Hall, 1860), and it is best known for its tight relationship with Pleurodictyum americanum. Brett and Cottrell (1982) published a detailed study of P. americanum and its associates, concluding that the coral preferred to encrust P. hamiltoniae shells but only when the snail itself was dead and gone and the shell was occupied by some other organism.
Pleurodictyum americanum underside showing an external mold of the gastropod Palaeozygopleura hamiltoniae.

Closer view of Palaeozygopleura hamiltoniae.

Pleurodictyum americanum was described by Carl Ferdinand von Roemer in 1876. Roemer was a German geologist (you probably guessed) who lived from 1818 to 1891 — a time interval encompassing some of the greatest changes in the Earth Sciences, from the primacy of Charles Lyell to the general acceptance of Darwinian evolution. Roemer was educated at Göttingen to be a lawyer, but in 1840 abandoned the legal profession for the much more exciting life of a geologist. He quickly obtained one of those new-fangled German PhD degrees in 1842 and set to work.
Roemer’s original 1876 drawings of Pleurodictyum americanum.

In 1845, Roemer traveled to the USA and studied the geology of Texas and other southern states. That must have been an adventure — the Battle of the Alamo was less than ten years before. It was during the American work that he began to describe Devonian fossils, including our coral species (Roemer, 1876). Roemer became a professor of geology, paleontology and mineralogy (another field in which he had significant accomplishments) at the Universty of Breslau, where he ended his career.

Carl Ferdinand von Roemer (1818 to 1891) at the University of Breslau (now the University of Wrocław in Poland).


Brett, C.E. and Cottrell, J.F. 1982. Substrate specificity in the Devonian tabulate coral Pleurodictyum. Lethaia 15: 247-262.

Pandolfi, J.M. and Burke, C.D. 1989. Environmental distribution of colony growth form in the favositid Pleurodictyum americanum. Lethaia 22: 69–84.

Roemer, F. von. 1876. Lethaea geognostica: Handbuch der erdgeschichte mit Abbildungen der für die formationen bezeichnendsten Versteinerungen, I. Theil. Lethaea palaeozoica. E. Schweizerbartsche Verlagshandlung (E. Koch), Stuttgart, Germany.

Quality time with a Polish microscope

June 21st, 2011

SOSNOWIEC, POLAND–A day in the lab with my colleague Michał Zatoń at the University of Silesia. We sorted through two very different paleontological problems with a microscope and a lot of hand waving. The first task was to come up with a hypothesis about the origin of the strange pitted tubes shown above. They are found on hiatus concretions of the Late Bathonian (Middle Jurassic) exposed in Zarki, Poland. We recently described and analyzed the sclerobionts on and in these concretions (see Zaton et al., 2011), but these tubes remained a mystery. We think now that they are remnants of egg cases laid by gastropods (snails) on the undersurfaces of the concretions, and we’ve started on the manuscript.

The coiled encrusting shell below is of a Devonian microconchid originally collected by the keen amateur Brian Bade in western New York and generously donated to our research. This group has some fascinating similarities and differences from its Polish cousins, so we have started a systematic project to determine if they represent a new genus or not. (Brian will be excited to hear this.)

Michal's office/lab in the Faculty of Earth Sciences, University of Silesia.

Tomorrow we set off for fieldwork in the area so I’ll post pictures of the wonderful Polish countryside!


Zatoń, M., Machocka, S., Wilson, M.A., Marynowski, L. and Taylor, P.D. 2011. Origin and paleoecology of Middle Jurassic hiatus concretions from Poland. Facies 57: 275-300.

Wooster’s Fossil of the Week: Mysterious tentaculitids (Devonian of Maryland)

May 29th, 2011

The sharp little conical fossils above are common Paleozoic fossils, especially in the Devonian. They are tentaculitids now most commonly placed in the Class Tentaculitoidea Ljashenko 1957. Tentaculitids appeared in the Ordovician and disappeared sometime around the end of the Carboniferous and beginning of the Permian. These specimens are from the Devonian of Maryland.

The systematic placement of the tentaculitids has been controversial. Their straight, narrow shells are usually ornamented by concentric rings, and many had septa (thin shelly partitions) inside the cones. The microstructure of the shells is most interesting — it looks very much like that of brachiopods and bryozoans. For this reason and several others, several of my colleagues and I believe the tentaculitids were lophophorates (animals that filter-feed with a tentacular device called a lophophore). They may thus be related to other problematic tubeworms like microconchids and cornulitids (Taylor et al., 2010).

Tentaculitids from the New Creek Limestone (Lochkovian, Early Devonian) of New Creek, West Virginia.

Knowing how the tentaculitids fit into an evolutionary scheme, though, has not helped us figure out what they did for a living. The figure below, from Cornell et al. (2003), shows these funny cones in just about every lifestyle imaginable!


Cornell, S.R., Brett, C.E. and Sumrall, C.D. 2003. Paleoecology and taphonomy of an edrioasteroid-dominated hardground association from tentaculitid limestones in the Early Devonian of New York: A Paleozoic rocky peritidal community. Palaios 18: 212-224.

Taylor, P.D., Vinn, O. and Wilson, M.A. 2010. Evolution of biomineralization in ‘lophophorates’. Special Papers in Palaeontology 84: 317-333.

Wooster’s Fossil of the Week: The tabulate coral Aulopora (Devonian of northwestern Ohio)

January 2nd, 2011

We’re going to start 2011 with a new blog feature: Fossil of the Week! My colleagues, of course, are welcome to also start “Mineral of the Week”, “Structural Geologic Feature of the Week”, or “Climate Event of the Week”.  The more the better to keep our blog active through the winter!

This week’s fossil was collected by Brian Bade of Sullivan, Ohio, and donated to Wooster as part of my hederelloid project.  It is a beautiful specimen of the tabulate coral Aulopora encrusting a brachiopod valve from the Silica Shale (Middle Devonian — about 390 million years old) of northwestern Ohio.  Auloporid corals are characterized by an encrusting habit, a bifurcating growth pattern, and horn-shaped corallites (individual skeletal containers for the polyps).

What is especially nice about this specimen is that we are looking at a well preserved colony origin.  The corallite marked with the yellow “P” is the protocorallite — the first corallite from which all the others are derived.  You can see that two corallites bud out from the protocorallite 180° from each other.  These two corallites in turn each bud two corallites, but at about 160°.  This pattern continues as the colony develops (a process called astogeny).  The angles of budding begin to vary depending on local obstacles; they never again go below 160°.

The polyps inside the corallites are presumed to have been like other colonial coral polyps.  Each would have had tentacles surrounding a central opening, and all were connecting by soft tissue within the skeleton.  They likely fed on zooplankton in the surrounding seawater.  This type of coral went extinct in the Permian, roughly 260 million years ago.

Again, we thank our amateur geologist friends for such useful donations to the research and educational collections in the Geology Department at Wooster.

Trays of trilobites, buckets of belemnites ….

November 26th, 2010

WOOSTER, OHIO — Last weekend we picked up another load of rocks, minerals and fossils donated by the family of one of our loyal alumni. We will be sorting through them for months getting them ready for displays and our teaching collections. Among the treasures are large numbers of particular items, especially fossils. I want to highlight two of many such sets. The trilobites are Phacops bufo from the Silica Shale (Devonian) of northeastern Ohio; the belemnites below are from the Jurassic of Wyoming. (Belemnites from the Upper Cretaceous of Germany and the Jurassic of Israel have been featured in this blog, as have beautiful trilobites from the Middle Cambrian of British Columbia, Canada.) Numerous nearly-identical fossils such as these play an important role in our teaching. We can, for example, have a fossil in front of each student during lectures for immediate reference (and quizzing!). It is also possible to have biometric measuring exercises in our labs with these fossil “populations” of particular species. Gifts again put to work in education!

Wooster celebrates National Fossil Day

October 13th, 2010

Crinoid holdfasts and bryozoans on a cobble from the Ordovician of northern Kentucky.

WOOSTER, OHIO–Today we are celebrating the first annual National Fossil Day (or at least I am!). Be sure to check out that link from the National Park Service — it contains the official National Fossil Day song! My recognition of this special day is to post some photographs of nice fossil specimens from the Wooster collections. You can find larger versions of these photos — and hundreds more — on my Wikimedia page. Here’s to fossils: beautiful messengers from the distant past.

Shark teeth (Scapanorhynchus) from the Upper Cretaceous of southern Israel. These were collected by Andrew Retzler ('11).

Rudist bivalves from the Upper Cretaceous of the Omani Mountains.

Tentaculitids from the Devonian of Maryland.

Thecideide brachiopods, cyclostome bryozoans and serpulids encrusting a bivalve shell from Zalas Quarry (Jurassic: Callovian-Oxfordian) in southern Poland.

Fossil leaf (Viburnum lesquereuxii) with insect damage; Dakota Sandstone (Cretaceous) of Ellsworth County, Kansas.

The value of amateur paleontology

October 10th, 2010

Brian Bade in the midst of his fossil collection and paleontological library.

SULLIVAN, OHIO–Last month I gave a talk to the North Coast Fossil Club about an obscure fossil group, the hederelloids. My purpose, besides simply enjoying the good company of fossil enthusiasts, was to show the audience a type of small and encrusting fossil they have all collected but probably didn’t notice because these creatures do not (at least to the naked eye) look very interesting. Sure enough, many in the club remembered seeing these fossils, and some had learned a considerable amount about them. Members began to send me specimens in the mail for further study.

One gentleman, though, told me he had hundreds of hederelloid fossils on Devonian brachiopods and corals collected in Ohio, Michigan and Ontario — and that I was welcome to use whatever specimens I needed to advance the science. Today I visited Brian Bade in nearby Sullivan, Ohio. His collection of these fossils and many more astounded me. He has thousands of specimens, matched with an extensive paleontological library. The fossils are very well curated (that is, we can easily tell the collecting localities and stratigraphic horizons) and expertly prepared. Brian is generous with his treasures and wants nothing more than to see them used in scientific studies. I borrowed several dozen encrusted brachiopods and corals to get started on a hederelloid taxonomy project.

Brian Bade with one of many, many drawers of specimens.

Brian is an excellent example of why amateur fossil paleontologists are essential to the progress of professional paleontology. He has a very keen eye for finding fossils and keeping them in their proper geological context (“provenance”). He instinctively can tell which specimens may be most interesting to science, and he shares with the professionals an appreciation for their beauty and rarity. Brian knows how to work with landowners and quarry managers to make sure access to fossil sites is maintained, which is a skill sometimes lacking in casual collectors. Amateur paleontologists often have far more time for fieldwork than the professionals, and usually have more experience in sorting out particular kinds of fossils in their specialties. Many paleontological studies rely upon the skills of amateurs to provide the raw data. Indeed, “amateur paleontologist” is not quite the right title considering the knowledge base and experience these men and women have accumulated. I prefer to call them simply “paleontologists”.

Devonian brachiopods in one of Brian's drawers. This year's paleontology class can now identify them from here!

Hederelloids: Pulled from obscurity! (Well, maybe …)

September 11th, 2010

PARMA, OHIO–This afternoon I gave a talk at a meeting of the North Coast Fossil Club in this suburb of Cleveland. I chose the poorly-known fossil group called hederelloids as my topic because I knew that many people in that enthusiastic group had likely seen and collected them without knowing. They are very common encrusters on Devonian fossils, especially brachiopods, corals and bryozoans from the Middle Devonian of northwestern Ohio. I was not disappointed as several keen members brought me specimens from their collections or told me about large numbers of hederelloids they can send to me for study. Paul Taylor and I have been studying hederelloids for the past five years (as far as I know we are the only paleontologists in this little subfield!) and believe they may hold a key to some curious events in the Devonian and may expand what we know about lophophorate evolution. We need many more specimens, though, for our systematic work. The hard-working, knowledgeable amateur paleontologists in the North Coast Fossil Club are now going to help! Here is a link to the PowerPoint slides of my hederelloid talk. If you just have to know more, here’s a 2008 Taylor and Wilson hederelloid paper as a pdf.

I very much enjoyed talking with members of this club. They love fossils for their beauty, complexity, and historical wonder. To be able to contribute to science is a bonus.

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