A beautiful day for Wooster Geologists in the Silurian of Ohio

April 18th, 2015

aDSC_5072FAIRBORN, OHIO–It’s field trip season at last for the Wooster Geologists. Several geology classes have now been out in Ohio, taking advantage of windows of spectacular weather. Today was one of those days for 25 students in the Sedimentology & Stratigraphy class. We returned to the Oakes Quarry Park exposures in southwestern Ohio (N 39.81472°, W 83.99471°). Three years ago here in April it was 37°F and raining. This year the conditions were perfect. We studied outcrops of the Brassfield Formation (Early Silurian, Llandovery) in the old quarry walls. The students measured stratigraphic columns of these fossiliferous biosparites as part of an exercise, and then explored the glacially-truncated top of the unit.

bDSC_5079The Brassfield is intensely fossiliferous. Large portions of it are virtually made of crinoid fragments. In the random view above you can see columnals, as well as a few calyx plates. This is why this unit is very popular among my echinodermologist friends at Ohio State.

DSC_5056Kevin Komara, Brian Merritt and Dan Misinay (Team Football) are here contemplating the quarry wall, planning how to measure their sections.

DSC_5063One of our Teaching Assistants, Sarah Bender, is here pointing out one of the many thin intercalated clay units in the Brassfield biosparites.

DSC_5065Fellow Californian Michael Williams directed the action. No, actually he’s doing the time-honored technique of following a measured unit with his finger as he finds a place he can safely climb to it and the units above. He is holding one of our measuring tools, a Jacob’s Staff. Why do we call them “Jacob’s Staffs”? Read Genesis 30:25-43. (Yes, today’s students are mystified by Biblical references.)

DSC_5066Here’s Rachel Wetzel, giving me a heart attack. Don’t worry, insurance companies and parents, she’s fine.

DSC_5068Rachel is again on the left. Team Ultimate Frisbee (Meredith Mann and Mae Kemsley) are in the front, and Sharron Ostermann is above. This is the recommended way to get to the top of the exposure!

DSC_5070We carried our lunches in “to go” boxes from the dining hall. Our Teaching Assistants Sarah Bender and Kaitlin Starr enjoyed a sunny picnic on the rocks.

yDSC_5077The top level of the quarry was cleared of soil and brush many years ago to expose a glacially truncated and polished surface of the Brassfield. Looking for glacial grooves and fossils here are (from the left) Tom Dickinson, Jeff Gunderson (another Californian!), Andrew Conaway, and Luke Kosowatz (who seems to also be making a little pile of rocks as a memorial to a great day).

zDSC_5074One of the many corals we found in the top of the Brassfield was this halysitid (“chain coral”), an indicator fossil for the Late Ordovician and Silurian.

Everyone returned safely to Wooster with their completed stratigraphic columns, lithological descriptions, and a few fossils. Thank you to Mark Livengood, our bus driver. Good luck to the other field trip groups later this month!

Wooster’s Fossil of the Week: A new crinoid genus from the Silurian of Estonia

March 13th, 2015

Velocrinus CD-interray lateralIt is my pleasure to introduce a new Silurian crinoid genus and species: Velocrinus coniculus Ausich, Wilson & Vinn, 2015. The image above is a CD-interray lateral view of the calyx (or head), with the small anal plate in the middle-top. (This will make more sense below.) The scale bar is 2.0 mm, so this is a small fossil. It was captured by the Crinoid Master himself (my friend and colleague Bill Ausich) from the Middle Äigu Beds of the Kaugatuma Formation (Upper Silurian, Pridoli) at the Kaugatuma Cliffs of Saaremaa Island, Estonia. It is described in the latest issue of the Journal of Paleontology. Here’s a link to the abstract. (This is the first issue produced by Cambridge University Press, so we’re honored to be part of publishing history.)
Velocrinus E-ray lateralHere is another view of the calyx, this time looking laterally at the E-ray.
AusichWilsonVinn_Fig3This figure explains the calyx views we see above. It is a plate diagram of Velocrinus coniculus. Imagine it as what the crinoid would look like if we could separate all its preserved ossicles and lay them out. The radial plates are black; the anal plate is shown stippled and marked with an “X”; the other letters indicate the particular rays. The artwork, and the images above, are from Bill Ausich.

The genus Velocrinus is defined this way in the paper: “Crotalocrinitid with a calyx cone shaped, lacking stereomic overgrowths, comprised of relatively large plates; infrabasals not fused, visible in lateral view; two anal plates; primaxil minute, not visible in lateral view; fixed brachials present; free arms not laterally linked; anus on tegmen; (nature of tegmen plating unknown).” This certainly is opaque to most readers. Trust us — it separates this new genus from all described before. Velocrinus is derived from the Latin term velo, which means to cover or conceal (think “veil”). It refers to the tiny primibrachials, which are not visible in lateral view. The species name coniculus refers to the cone-shaped calyx.
Kaugatuma070511Velocrinus coniculus is known only from the Kaugatuma Cliffs locality on Saaremaa Island. This is one of my favorite outcrops in Estonia. The extensive bedding-plane exposures are rare in the region. They show hundreds of holdfasts (essentially roots) of crinoids, some very large. The deposit was a relatively high-energy carbonate sand shifting through a forest of tall crinoids rooted in the sediment. Palmer Shonk (’10) did an excellent Senior Independent Study with rocks and fossils we collected from this place. The site shown above, by the way, was the location of a Soviet amphibious landing in November 1944.
KaugatumaCrinoidStem070511This is a close look at a bedding plane of Middle Äigu Beds of the Kaugatuma Formation. The crinoid stems are robust and abundant. Oddly enough, we’re still not sure what genus is represented by the large stems and holdfasts. The calyx of Velocrinus coniculus is far too small to have been associated with them. I suppose this means we need another expedition to Estonia!

This is the 1000th post in the Wooster Geologists blog.


Ausich, W.I., Wilson, M.A. and Vinn, O, 2012. Crinoids from the Silurian of western Estonia. Acta Palaeontologica Polonica 57: 613–631.

Ausich, W.I., Wilson, M.A. and Vinn, O, 2015. Wenlock and Pridoli (Silurian) crinoids from Saaremaa, western Estonia (Phylum Echinodermata). Journal of Paleontology 89: 72-81.

Wooster’s Fossil of the Week: A stromatoporoid from the Silurian of Estonia

January 30th, 2015

Densastroma pexisumStromatoporoids are extinct sponges that formed thick, laminated skeletons of calcite. They can be very common in Silurian and Devonian carbonate units, sometimes forming extensive reefs. The stromatoporoid above is Densastroma pexisum (Yavorsky, 1929) collected from the Mustjala Member of the Jaani Formation (Silurian, Wenlock) exposed on Saaremaa Island, Estonia. It was part of Rob McConnell’s excellent Senior Independent Study he completed in 2010.
Densastroma pexisum sectionStromatoporoids are rather featureless lumps until you cut a section through them. Then you see their characteristic laminae of calcite. Looking very close you might also glimpse the tiny vertical pillars between the laminae. Identifying the species of stromatoporoid always involves a thin-section or acetate peel to discern the forms of the pillars and laminae.

In the upper left of the sectioned D. pexisum is an oval boring cut through the fabric of the stromatoporoid. This is likely the trace fossil Osprioneides kampto Beuck and Wisshak, 2008. This is the largest known Palaeozoic boring. It is relatively common in Silurian stromatoporoids of the Baltic region. Last year Olev Vinn, Mari-Ann Mõtus and I published a paper describing the same ichnospecies in large trepostome bryozoans from the Estonian Ordovician.
8 schematic drawing of Osprioneides kampto
This diagram of O. kampto is from Figure 8 of the Beuck et al. (2008) paper. The organism that made the boring was almost certainly a filter-feeding worm of some kind that gained a feeding advantage by placing itself high on a hard substrate.
Flügel in 7000 ts by Chris SchulbertDensastroma was originally named in 1958 by Erik Flügel (1934-2004). He combined the Latin densus with the Greek stroma, meaning “dense-layered”. (Yes, taxonomic purists will object to the mix of Latin and Greek in one name.) Flügel was a highly accomplished and diverse scientist who founded the Institute of Paleontology at the University of Erlangen-Nuremberg as well as the journal Facies. He is best known for his advocacy of detailed study of carbonate facies through petrography (“microfacies analysis“), developing a series of techniques and principles that I found very useful in my dissertation work. The above image is a fitting tribute to Erik Flügel made by Chris Schulbert. It is a portrait made of 7000 carbonate thin-sections!


Beuck, L., Wisshak, M., Munnecke, A. and Freiwald, A. 2008. A giant boring in a Silurian stromatoporoid analysed by computer tomography. Acta Palaeontologica Polonica 53: 149-160.

Flügel, E. 1959. Die Gattung Actinostroma Nicholson und ihre Arten (Stromatoporoidea). Annalen des Naturhistorischen Museums in Wien 63: 90-273.

Freiwald, A. 2004. Erik Flügel: 1934–2004. Facies 50: 149-159.

Vinn, O., Wilson, M.A. and Mõtus, M.-A. 2014. The earliest giant Osprioneides borings from the Sandbian (Late Ordovician) of Estonia. PLoS ONE 9(6): e99455. doi:10.1371/journal.pone.0099455.

Wooster’s Fossils of the Week: The mysterious Paleozoic encrusters Ascodictyon and Allonema

September 12th, 2014


1 Slide01The above pair of fossils are small sclerobionts commonly found on hard substrates in shallow marine sediments through much of the Paleozoic, especially the Silurian and Devonian. Paul Taylor and I have been studying them for a few years now and our first paper on them was published this summer (Wilson and Taylor, 2014). Ascodictyon (Silurian-Carboniferous) is on the left and Allonema (Silurian-Permian) is on the right. Both are calcitic encrusters and look, at least in this view, very different from each other. We present evidence in our paper, though, that strongly suggests Ascodictyon and Allonema are actually manifestations of the same organism. What that organism is, exactly, still eludes us. We are persuaded at the very least that they are not bryozoans as originally described by Nicholson, Ulrich and Bassler. Since they are so common their identity is important for studies of fossil diversity and paleoecology.
2 Slide07The above view through a light microscope of Ascodictyon and Allonema shows the perspective paleontologists have had of these encrusters until recently. The clear calcite skeletons sitting on a calcitic brachiopod shell (this is from the Devonian of Michigan) makes for little contrast and poor resolution, and the microscope-camera combination has a very limited depth of field. The rest of the images in this post were made with a Scanning Electron Microscope (SEM) expertly operated by Paul. The difference in morphological detail is not just astonishing, it is a revolution in the study of tiny fossils like this.
3 Slide16 siluriense UKThis is a typical view of Ascodictyon. It consists of stellate clusters of inflated vesicles (like little calcite balloons) connected by thin calcitic tubes called stolons. (Ascodictyon siluriense from the Silurian of the England.)

4 Slide24 waldronense S GotlandThis is a typical Allonema. The primary form is a series of porous vesicles attached in chains like sausages. (Allonema waldronense from the Silurian of Gotland, Sweden.)

5 Slide29 Silica MIHere is where these obscure little encrusters get interesting. This is a specimen from the Silica Shale (Middle Devonian) exposed in Michigan. It was collected in a beautiful suite of fossils by that intrepid citizen scientist, Brian Bade. It consists of Allonema sausages connected to Ascodictyon stolons which are themselves connected to Ascodictyon stellate vesicle clusters. Clear evidence that Allonema and Ascodictyon are end members of a morphological continuum produced by the same organism.

7 Slide33 Silica MIA critical feature we see in this Ascodictyon/Allonema complex is the occurrence of “sockets” at the bases of vesicles like the above from the Silica Shale. These are almost certainly places where some erect portion of the organism extended above the substrate. Maybe these were feeding devices? Reproductive parts? We’ve found no trace of them.

8 Slide39 S GotlandOur hypothesis is that Allonema (left) and Ascodictyon (right, both from the Silurian of Gotland, Sweden) are the basal parts of some as yet unknown erect organism. They may have stored nutrients for the creature. We are convinced they were not bryozoans, foraminiferans, corals or sponges. Unfortunately we can only classify them as incertae sedis or Microproblematica. At some point we’ll have to figure out how to name this complex with two genera and over a dozen species.

It was fun work, and the project continues. For more detail, see Wilson and Taylor (2014).


Nicholson H.A. and Etheridge R. 1877. On Ascodictyon, a new provisional and anomalous genus of Palæozoic fossils. J. Nat. Hist., Series 4, 19: 463-468.

Ulrich E.O. and Bassler R.S. 1904. A revision of the Paleozoic Bryozoa. Smith. Misc. Coll. (Quart.) 45: 256-294.

Wilson M.A. and Taylor P.D. 2001. “Pseudobryozoans” and the problem of encruster diversity in the Paleozoic. PaleoBios 21 (Supplement to No. 2): 134-135.

Wilson, M.A. and Taylor, P.D. 2014. The morphology and affinities of Allonema and Ascodictyon, two abundant Palaeozoic encrusters commonly misattributed to the ctenostome bryozoans. In: Rosso, A., Wyse Jackson, P.N. and Porter, J. (eds.), Bryozoan Studies 2013. Studi trentini di scienze naturali 94: 259-266.

Wooster’s Fossil of the Week: A tubeworm-encrusted parasitic gastropod (Silurian of Indiana)

February 16th, 2014

Platyostoma1_585Last week three Wooster geology students and I visited Ken Karns, an enthusiastic citizen scientist who has developed an extraordinary fossil collection in his home in Lancaster, Ohio. Ken is a man of prodigious energies and skills as he not only is an expert fossil collector and preparator, he also has a world-class curated collection of Ohio beetles! He was introduced to us by our friend Brian Bade, a man with similar enthusiasms and skills. The students were Steph Bosch (’14), Lizzie Reinthal (’14) and Ian Tulungen (’15). Our goals were to meet Ken, see his magnificent collection with Brian and other friends, and then focus on a project for Ian’s future Independent Study work. Success on all counts, and the specimen above is evidence. Ken was very generous in loaning this specimen to us along with several others for Ian’s work.

The above specimen is from the type section of the Waldron Shale Member (Silurian, Wenlockian, Homerian, about 430 million years old) of the Pleasant Mills Formation near St. Paul, south-central Indiana. Ken Karns collected and prepared it. It is a platyceratid snail of the genus Platyostoma Conrad 1842. It is probably of the species P. niagarense Hall 1852, but there is another species in the same unit (P. plebeium Hall 1876). I’m not quite sure of the differences between these species because platyceratids are notoriously variable. It is possible they are synonymous. Unlike most gastropods, platyceratids had calcite shells instead of aragonite, so they are very well preserved. For an excellent taxonomic review of the genus Platyostoma and its founder, Timothy Abbott Conrad, please see Tony Edger’s blog entry. (We’ve talked about Conrad in this blog as well.)
Platyostoma2_585In this different angle on the specimen you can see additional encrusters (sclerobionts) on the surface of the Platyostoma shell. In the lower right is a remnant of a sheet-like bryozoan, but the most prominent sclerobionts are the tubeworms Cornulites proprius Hall 1876. These encrusters interest us very much.
Cornulitids on Platyostoma_585In this closer view it is apparent that several of the cornulitids are aligned with their apertures pointing in the same way. This is a pattern we’ve seen on many of these snails. Platyostoma was a parasitic snail that lived attached to crinoids, which were abundant in the Waldron fauna. They lived high on the calyx of the crinoid firmly fixed to its skeleton. These cornulitids and other encrusters were thus living high off the substrate perched on the snails. They were filter-feeders like the crinoids, so they may have been feeding on some suspended food fraction missed by the crinoid arms, or they were competing for nutrients and added to the parasitic load on the poor crinoids. The cornulitids were further living on a living snail shell, from what we can tell, so they grew with a substrate slowly growing underneath them. This produces all sorts of delicious paleoecological questions to sort out!
Platyostoma long cornulitid_585Check out the size of this specimen of Cornulites proprius attached to another Platyostoma niagarense. Clearly these tubeworms could do very well under these conditions! This is the largest cornulitid I’ve seen.

Ken_Karns_preparatory_labHere is Ken Karns in his fossil preparation laboratory, which he assembled himself. The box with the armholes is for air-abrading specimens to remove matrix.

Display cases KenThis is one section of the display cases Ken has in his basement museum. Most of the specimens shown here are from the Waldron Shale.

Platyostoma collection displayedA closer view of a display of Platyostoma from the Waldron Shale. Note the many encrusters.

Lizzie Brian KenLizzie Reinthal, Brian Bade and Ken talk about fossil preparation with some Waldron material. The cases are full of curated specimens.

Encrusted crinoid rootsThere are so many treasures in Ken’s collections. I am fascinated by this little slab showing the holdfast of a crinoid with sheet-like bryozoans encrusting it. The bryozoans show that the roots were at least partially exposed at some point.

Thank you again to Brian Bade for arranging this trip, and Ken Karns for being such a fantastic host. We are looking forward to many Waldron projects in the future!


Baumiller, T.K. 2003. Evaluating the interaction between platyceratid gastropods and crinoids: a cost–benefit approach. Palaeogeography, Palaeoclimatology, Palaeoecology 201: 199-209.

Baumiller, T.K. and Gahn, F.J. 2002. Fossil record of parasitism on marine invertebrates with special emphasis on the platyceratid-crinoid interaction. Paleontological Society Papers 8: 195-210.

Brett, C.E., Cramer, B.D., McLaughlin, P.I., Kleffner, M.A., Showers, W.J. and Thomka, J.R. 2012. Revised Telychian–Sheinwoodian (Silurian) stratigraphy of the Laurentian mid-continent: building uniform nomenclature along the Cincinnati Arch. Bulletin of Geosciences 87: 733–753.

Feldman, H.R. 1989. Taphonomic processes in the Waldron Shale, Silurian, southern Indiana. Palaios 4: 144-156.

Gahn, F.J. and Baumiller, T.K. 2006. Using platyceratid gastropod behaviour to test functional morphology. Historical Biology 18: 397-404.

Gahn, F.J., Fabian, A. and Baumiller, T.K. 2003. Additional evidence for the drilling behavior of Paleozoic gastropods. Acta Palaeontologica Polonica 48: 156-156.

Hall, J. 1881. Descriptions of the Species of Fossils Found in the Niagara Group at Waldron, Indiana. In: Indiana Department of Geology and Natural Resources, Eleventh Annual Report, p. 217-345. [PDF of the text downloadable here.]

Liddell, W.D. and Brett, C.E. (1982). Skeletal overgrowths among epizoans from the Silurian (Wenlockian) Waldron Shale. Paleobiology 8: 67-78.

Peters, S.E. and Bork, K.B. 1998. Secondary tiering on crinoids from the Waldron Shale (Silurian: Wenlockian) of Indiana. Journal of Paleontology 72: 887-894.

Sutton, M.D., Briggs, D.E.G., Siveter, D.J. and Siveter, D.J. 2006. Fossilized soft tissues in a Silurian platyceratid gastropod. Proceedings of the Royal Society B: Biological Science 273(1590): 1039-1044.

Taylor, P.D. and Wilson, M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103.

Citizen scientist to the rescue (in more ways than one)

November 9th, 2013

StephLizzie110913NEW LONDON, OHIO–The Wooster paleontologists spent a pleasant afternoon with our favorite amateur fossil collector Brian Bade. Brian has been mentioned in this blog previously for the many important fossils he has found and donated. He is a spectacular citizen scientist with a deep love (some would say obsession) with fossils of all kinds. He has a tremendous collection of fossils from the region and elsewhere carefully cataloged as to formations and localities. He knows what specimens may have scientific importance, and he has always been most generous with his time and fossils.

Today Steph Bosch (’14), Lizzie Reinthal (’14) and I visited Brian to examine specimens he recently collected from the Waldron Shale (Silurian) exposed in the St. Paul Stone Quarry in St. Paul, Indiana. My colleagues and I need to examine Silurian microconchids from North America and, sure enough, Brian came to the rescue with his collections and eagle eyes. Not only did he have his cleaned and sorted Waldron material laid out for us, he also had segregated specimens that had encrusting microconchids on them. The fossils were fantastic. Check out this webpage to get an idea of the paleontological diversity at this site.

Brian also brought out other trays and boxes of fossils from the Silurian and Early Devonian that had encrusters. Lizzie and Steph proved adept at picking out the tiny microconchids with their bare, young eyes as I struggled with my usual handlens. (This was the typical situation during our fieldwork in Israel this summer as well.) We accumulated several excellent specimens for later study under a Scanning Electron Microscope. Brian once again came through with critical fossils collected with all the right information for scientific analysis.

And the other rescue by Brian? You can see the situation in the image below. After all the driving I did in exotic places this summer, I managed to burrow into deep mud in Brian’s front yard. My little car was completely mired. (Note the smirking students in the background getting ready to tweet photos.) Brian has a tractor, fortunately enough, and a long chain. I left behind two deep trenches in his grass, and a little bit of my pride.

Wooster’s Fossils of the Week: Very common orthocerid nautiloids from the Siluro-Devonian of Morocco

November 3rd, 2013

Nautiloids585_092313If you’ve been to a rock shop, or even googled “fossil”, you’ve seen these beautiful and ubiquitous objects. They are polished sections through a nautiloid known as “Orthoceras“. We put quotes around the genus name because with these views it is nearly impossible to identify the actual genus, so “Orthoceras” becomes the go-to term for unknown orthoconic (straight) nautiloids. We also do not know exactly where in Morocco these fossils come from, but chances are they were dug out of the Orthoceras Limestone (Siluro-Devonian) exposed near Erfoud in the Ziz Valley near the edge of the Sahara Desert. They are easily excavated, take a nice polish, and look good from almost any angle of cut. People bring these to me often to ask about their origin, so let’s do a Fossil of the Week about the critters.

These fossil nautiloids consisted in life of a long, straight conical shell with internal chambers pierced by a long tube. The shells were originally made of aragonite, but almost all have been replaced and recrystallized with calcite. A squid-like animal produced the shell. Most of its body was in the large body chamber at the open end of the cone. They were effective nektic (swimming) predators during the Paleozoic Era around the world. In some places (like Morocco) nautiloids were so common that their dead shells carpeted shallow seafloors. Nautilus is a living descendant.
SingleNautiloid092313 annotatedIn this closer cross-sectional view of a Moroccan “Orthoceras“, we can identify the critical parts. A = a chamber (or camera); B = the siphuncle (tube running through the center of the shell); C = a septum that divides one chamber from another; D = an orthochoanitic (straight) septal neck of shell that runs briefly along the siphuncle. The white to gray material is crystalline (“sparry”) calcite that filled the empty shell after death and burial.

By the way, you can buy “Orthoceras healing stones“. A quote from that site: “Fossils are believed to increase life span, reduce toxins, anxiety, stress, balance the emotions, make one more confident. Containing supernatural and physical healing powers. They promote a sense of pride and success in business. Healers use fossils to enhance telepathy and stimulate the mind. Traditionally, fossils have been used to aid in  reducing tiredness, fatigue, digestive disorders, and rheumatism.” No wonder paleontologists are always the very image of health and wealth!
BRUGIEREThe genus Orthoceras was named in 1789 by the French zoologist (and physician) Jean Guillaume Bruguière (1749–1798). The only image I could find of him is the small one above. Bruguière earned a medical degree from the University of Montpellier in 1770, but like many aspiring naturalists, he never practiced. He traveled very widely for an 18th Century scientist, usually to pursue living and fossil mollusks on various expeditions. That he was a Republican in revolutionary France probably saved his head, but he lost his income in the turmoil. Most of his descriptions of fossil taxa appeared in print decades after he died on a voyage back from Persia. Of all his taxonomic contributions, the genus Orthoceras is the most widely known.


Histon, K. 2012. Paleoenvironmental and temporal significance of variably colored Paleozoic orthoconic nautiloid cephalopod accumulations. Palaeogeography, Palaeoclimatology, Palaeoecology 367–368: 193–208.

Kröger B. 2008. Nautiloids before and during the origin of ammonoids in a Siluro-Devonian section in the Tafilalt, Anti-Atlas, Morocco. Special Papers in Palaeontology 79, 110 pp.

Lubeseder, S. 2008. Palaeozoic low-oxygen, high-latitude carbonates: Silurian and Lower Devonian nautiloid and scyphocrinoid limestones of the Anti-Atlas (Morocco). Palaeogeography, Palaeoclimatology, Palaeoecology 264: 195-209.

Wooster’s Fossils of the Week: Embedded cornulitids from the Lower Silurian of Estonia

May 12th, 2013

Cornulitids_Strom_051113At first specimen this looks like a series of holes drilled into a small, smooth substrate (like Trypanites), but then you notice that the substrate has grown up around the holes, and on the far left you can make out two cones. These are cornulitid tubes that lived on and then inside a living stromatoporoid sponge. Jonah Novek (’13), a Wooster geologist graduating tomorrow, found these in the Hilliste Formation (Rhuddanian, Llandovery) during his Independent Study work on Hiiumaa Island in Estonia.

My Estonian paleontologist friend Olev Vinn is the expert in bioclaustrated (embedded in a living substrate) cornulitids, as you can see from the papers listed below. These fossils are an excellent example of endosymbiosis, or the living relationship of one organism embedded within the skeleton of another (see Tapanila and Holmer, 2006). We can’t tell yet without a thin-section, but the cornulitid here is probably very similar to the Sheinwoodian (Wenlock) Cornulites stromatoporoides Vinn and Wilson, 2010. The specimen shown above is already in the mail to Estonia for further analysis. This specimen is the earliest example of cornulitid endosymbiosis in the Silurian.
Closer_Cornulitids_Strom_051113A closer view of the embedded cornulitid tubes. The tubes in these holes appear to have dissolved away, at least in their distal parts. Some of the details of the stromatoporoid substrate are just visible.

Jonah_MW_Richa_071213Fond memories of the 2012 Wooster-Ohio State University expedition to Estonia. Jonah Novek (’13), me, and Richa Ekka (’13) on the top of the Kõpu Lighthouse, Hiiumaa Island, Estonia. Photo by our friend Bill Ausich (OSU).

Congratulations to Jonah on his find, and best wishes to all the senior Wooster Geologists on this graduation weekend.


Tapanila, L. and Holmer, L.E. 2006. Endosymbiosis in Ordovician-Silurian corals and stromatoporoids: A new lingulid and its trace from eastern Canada. Journal of Paleontology 80: 750-759.

Vinn, O. and Wilson, M.A. 2010. Abundant endosymbiotic Cornulites in the Sheinwoodian (Early Silurian) stromatoporoids of Saaremaa, Estonia. Neues Jahrbuch für Geologie und Paläontologie 257:13-22.

Vinn, O. and Wilson, M.A. 2012a. Encrustation and bioerosion on late Sheinwoodian (Wenlock, Silurian) stromatoporoids from Saaremaa, Estonia. Carnets de Géologie [Notebooks on Geology], Brest, Article 2012/07 (CG2012_A07).

Vinn, O. and Wilson, M.A. 2012b. Epi- and endobionts on the Late Silurian (early Pridoli) stromatoporoids from Saaremaa Island, Estonia. Annales Societatis Geologorum Poloniae 82: 195-200.

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

April 21st, 2013

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.

Stratigraphy and paleoenvironments of the Soeginina Beds (Paadla Formation, Lower Ludlow, Upper Silurian) on Saaremaa Island, Estonia (Senior Independent Study Thesis by Richa Ekka)

January 28th, 2013


Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We post abstracts of each study as they become available.  The following was written by Richa Ekka, a senior geology major from Jamshedpur, India. She finished her thesis and graduated in December, so her work is the first of her class to be posted. You can see earlier blog posts from Richa’s study by clicking the Estonia tag to the right.

In July 2012, I travelled to Estonia with my advisor, Dr. Mark Wilson, a fellow Wooster geology major Jonah Novek, Dr. Bill Ausich and three geology students of The Ohio State University. It was quite an adventure with a few unexpected changes in our travel plans. Dr. Wilson and I had to spend a day in Tallinn, waiting for Jonah as his flight was delayed. Upon Jonah’s arrival we headed for the island of Saaremaa, where I carried out my research. We stayed in Kuressaare, on the southern shore of the island. I did my field research on the Soeginina Beds at Kübassaare in eastern Saaremaa.

The Kübessaare coastal area is an outcrop of the Soeginina Beds in the Paadla Formation (lowermost Ludlow) that represents a sequence of dolostones, marls, and stromatolites (see figure above). The Soeginina Beds represent rocks just above the Wenlock/Ludlow boundary, which is distinguished by a major disconformity that can be correlated to a regional regression on the paleocontinent of Baltica. The occurrence of these sedimentary structures and fauna in the Soeginina Beds provide us with evidence that there was a change in paleoenvironmental conditions from a shelfal marine environment to a restricted shallow marine setting followed by a hypersaline supratidal setting.

The base of the section has Chondrites trace fossils and marly shale that represent a shelfal marine environment. The next section on top has dolostones with Herrmannina ostracods, oncoids, and eurypterid fragments that indicate a shallow marine setting (lagoonal). The next section above has stromatolites (see figure below) that form in exposed intertidal mud flats. The topmost section has halite crystal molds that represent a hypersaline supratidal setting. Thus, we see a change from shelfal marine environment to a restricted shallow marine setting and finally to a hypersaline supratidal setting.


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