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

March 24th, 2013

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.

Wooster’s Fossil of the Week: A brittle star from the Upper Jurassic of Germany

March 10th, 2013

Ophiopetra lithographica aboral larger 010813_585Wooster geologists have again greatly benefited from the donation of a collection by an alumnus. George Chambers (’79), a successful professional photographer, sent us several boxes of minerals, rocks and fossils he had acquired in his lifelong passion for geology. (George was a geology major at Wooster in the class just after mine.) Among the many world-class specimens he gave us are two fossil ophiuroids (brittle stars). They are Ophiopetra lithographica Enay and Hess, 1962, from the Lower Hienheim Beds (Lower Tithonian, Upper Jurassic) near Regensburg, Germany. They are part of the “Fossillagerstätte Hienheim“, a preserved brittle star ecosystem in a lagoon at the edge of a Late Jurassic sea. This is the same set of lithographic limestones in which the famous bird fossil Archaeopteryx was found.
Ophiopetra lithographica 010813_585In both these images you see the spiny arms of the brittle stars twisted about. It is their flexibility and snake-like movements in life that provoked the scientific name ophiuroids (serpent-forms) for the brittle stars. The “brittle” term comes from their ability to autotomize (spontaneously detach) their arms when threatened, leaving a squirming distraction for a predator as they escape.
Ophiopetra lithographica aboral 010813_585Ophiopetra lithographica is probably the most common fossil brittle star known. It was preserved by the countless millions in these Jurassic lagoons in Germany. Most geologists believe they were buried by fine-grained carbonate sediment suspended by sudden storms. As you can see in the above close-up, the preservation of the plates and spines is remarkable.

Most brittle stars are suspension feeders (sorting out food particles from the water), deposit feeders (eating organic material in the sediment) or scavengers. Ophiopetra lithographica may have been a carnivore with its heavily-spined arms and strong jaws. It likely ate small arthropods on the seafloor.

The evolution of brittle stars is interesting and controversial. They were relatively common in the Paleozoic and then just barely survived the Permian extinctions. Their rapid evolution into a variety of taxa in the Mesozoic and Cenozoic has led to many debates about their phylogeny. Even the placement of Ophiopetra into a family is a problem. Does it belong to the Family Aplocomidae where it was originally placed or to the older Family Ophiolepididae as has been recently suggested?

Our students will enjoy these fine fossils in the invertebrate paleontology course. They have doubled our collection of brittle stars! Thank you again to George Chambers for his thoughtfulness and generosity.


Enay, R. and Hess, H. 1962. Sur la découvertes d’Ophiures (Ophiopetra lithographica n.g. n.sp.) dans le Jurassique supérieur du Haut-Valromey (Jura méridional). Eclogae geologicae Helvetiae 55: 657-678.

Hess, H. and Meyer, C.A. 2008. A new ophiuroid (Geocoma schoentalensis sp. nov.) from the Middle Jurassic of northeastern Switzerland and remarks on the Family Aplocomidae Hess 1965. Swiss Journal of Geosciences 101: 29-40.

Röper, M. and Rothgänger, M. 1998. Die Plattenkalke von Hienheim (Landkreis Kelheim) – Echinodermen-Biotope im Südfränkischen Jura. Eichendorf (Eichendorf Verlag), 110 S.

Stöhr, S. 2012. Ophiuroid (Echinodermata) systematics—where do we come from, where do we stand and where should we go? In: Kroh, A. and Reich, M. (Eds.) Echinoderm Research 2010: Proceedings of the Seventh European Conference on Echinoderms, Göttingen, Germany, 2–9 October 2010. Zoosymposia, 7: 147-161.

Thuy, B., Klompmaker, A.A. and Jagt, J.W.M. 2012. Late Triassic (Rhaetian) ophiuroids from Winterswijk, the Netherlands; with comments on the systematic position of Aplocoma (Echinodermata, Ophiolepididae). In: Kroh, A. and Reich, M. (Eds.) Echinoderm Research 2010: Proceedings of the Seventh European Conference on Echinoderms, Göttingen, Germany, 2–9 October 2010. Zoosymposia, 7: 163-172.

Wooster’s Pseudofossil of the Week: Manganese dendrites from Germany

January 20th, 2013

We haven’t had a pseudofossil in this space for awhile. A pseudofossil is an object that is often mistaken for a fossil but is actually inorganic. The above may look like  fossil fern, but it is instead a set of beautiful manganese dendrites in the Solnhofen Limestone (Jurassic) of Germany (scale in millimeters). I put this photo on Wikipedia a long time ago as manganese dendrites. That didn’t stop one website from still using it as an example of a fossil.

Manganese dendrites are thin, branching crystals that grew over a surface in a rock or mineral. Often they are found in cracks or along bedding planes (as in the above example). These dendrites are usually some variety of manganese oxide. The minerals represented can include hollandite, coronadite, and cryptomelane. Apparently they are never pyrolusite, despite what you may see in textbooks. It is also impossible to tell the mineralogy from the shape of the dendrites alone.

How can you tell this is not a fossil plant? For one, the branches are too perfect: none overlap or are folded over or broken as you would expect in a buried three-dimensional plant. Next you’ll notice that all the branches extend from a line at the bottom of the image rather than from a single branching point. Finally, there is no distinction between branch, stem or leaf; instead it is a fractal-like distribution of tiny sharp-edged crystals.

As a bonus, check out this benefit you get from having manganese dendrites:

“Metaphysically, stones with dendrites resonate with blood vessels and nerves. They help heal the nervous system and conditions such as neuralgia. Dendrites can help with skeletal disorders, reverse capillary degeneration and stimulate the circulatory system. It is the stone of plenitude; it also helps create a peaceful environment and encourage the enjoyment of each moment. Dendrites deepen your connection to the earth and can bring stability in times of strife or confusion.”

The Stone of Plenitude! (I hope you do see my sarcasm here …)

This post, by the way, marks the completion of the second year of Wooster’s Fossils of the Week. So far we’ve had 104 posts. Check out our very first edition about a sweet auloporid coral!


Potter, R.M. and Rossman, G.R. 1979. The mineralogy of manganese dendrites and coatings. American Mineralogist 64: 1219-1226.

Post, J.E. and McKeown, D.A. 2001. Characterization of manganese oxide mineralogy in rock varnish and dendrites using X-ray absorption spectroscopy. American Mineralogist 86: 701-713.

Wooster’s Fossils of the Week: Episkeletozoans from the Middle Jurassic of Israel

December 30th, 2012

Stomatopora122812Last week I had a delightful research afternoon with my former student Lisa Park Boush, now a professor in the Department of Geology and Environmental Science at The University of Akron, and currently Program Director, National Science Foundation, Sedimentary Geology and Paleontology Program, EAR Division. Lisa also directs an Environmental Scanning Electron Microscope (ESEM) lab in Akron. We worked there with the FEI Quanta 200 microscope looking at encrusters on echinoid fragments from the Matmor Formation (Middle Jurassic) of southern Israel. These encrusters are called episkeletozoans, a five-nickel word meaning that they are animals that encrusted the exteriors of skeletal fragments.

The specimen above is an eroded bryozoan episkeletozoan on the interior of an echinoid coronal fragment. It’s been beat up a bit and partially recrystallized, but we can see enough to identify it as the cyclostome Stomatopora Bronn, 1825.
SpineForam1This is the base of an echinoid spine with a tiny foraminiferan attached to it.
ForamSpine2Here is a close-up of the above foraminiferan. It is probably Placopsilina d’Orbigny, 1850. You can see an apparent aperture looking a bit like a blowhole on the left end top.
LisaSEM122812Above is our hero Lisa running the ESEM. This complicated device uses low vacuum so that we can look at uncoated specimens. We just stuck the specimens onto stubs with conducting tape and placed them in the chamber (on the right). I remember the old days when electron microscopy specimens had to be carefully dried and sputter-coated with gold or carbon. The advent of the ESEM made high quality imaging much easier, and thus more commonly done.

The images we took on this day are part of a larger project describing and interpreting the paleoecology of the Matmor Formation. It is a huge task, but every helpful session like this moves us closer to completion. Thanks, Lisa!


Guilbault, J.-P., Krautter, M., Conway, K.W., and Barrie, J.V. 2006. Modern Foraminifera attached to hexactinellid sponge meshwork on the West Canadian Shelf: Comparison with Jurassic counterparts from Europe. Palaeontologia Electronica 9, Issue 1; 3A:48p; http://palaeo-electronica.org/paleo/2006_1/sponge/issue1_06.htm

Richardson-White, S. and S.E. Walker, S.E. 2011. Diversity, taphonomy and behavior of encrusting Foraminifera on experimental shells deployed along a shelf-to-slope bathymetric gradient, Lee Stocking Island, Bahamas. Palaeogeography, Palaeoclimatology, Palaeoecology 312: 305–324.

Taylor, P.D. and Furness, R.W. 1978. Astogenetic and environmental variation of zooid size within colonies of Jurassic Stomatopora (Bryozoa, Cyclostomata). Journal of Paleontology 52: 1093-1102.

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

Walker, S.E., Parsons-Hubbard, K., Richardson-White, S., Brett, C. and Powell, E. 2011. Alpha and beta diversity of encrusting foraminifera that recruit to long-term experiments along a carbonate platform-to-slope gradient: Paleoecological and paleoenvironmental implications. Palaeogeography, Palaeoclimatology, Palaeoecology 312: 325–349.

Geological fieldwork on the streets of Dublin

December 16th, 2012

DublinRainbow121612DUBLIN, IRELAND — What could be more Irish than a rainbow over Dublin? (I know better than to write of leprechauns and pots of gold.)  It certainly crowned the end of a delightful afternoon spent with my friend Tim Palmer looking at building stones.

I am in Dublin attending the annual meeting of the Palaeontological Association. After a long editorial meeting, Tim and I went to the center of the city to look for a particular kind of stone that may have been used in the Medieval portions of the two Dublin cathedrals: St. Patrick’s (National Cathedral of the Church of Ireland) and Christ Church (also for the Church of Ireland but claimed by Roman Catholics — it’s confusing, especially since they are only a short walk from each other). Tim was looking for a limestone called Dundry Stone, part of the Inferior Oolite (Middle Jurassic) in Great Britain. It is notable as a non-oolitic part of the Inferior Oolite, made mostly of tiny fragments of crinoids and calcite cement. Tim quickly found the stone in both cathedrals.

StPatricks121612This is St. Patrick’s Cathedral. Its exterior is mostly restored, but the interior still retains part of its Medieval core. It dates back to 1191.

StPatricksChapelDoorway121612We asked at the door to see the oldest part of St. Patrick’s, and were immediately directed to this small chapel. At the time the cathedral was filling with people for a choir concert, so we were surrounded with the sounds of bells and children practicing their pieces. This chapel was used as a storeroom as well as a tourist site, so there are some incongruities (such as the folding chairs!). Almost all the stone is either covered with cement or replacements except in a few places, like the frame of this small doorway. That white rock is Dundry stone.

ChristChurchCathedral121612This is Christ Church Cathedral, just down the road from St. Patrick’s. (A rivalry between the two dates back to the 12th Century. Two cathedrals in one city is very rare, apparently.) Christ Church is the older of the two cathedrals, dating back to about 1040 when a Viking king of Dublin started construction. It also has a mostly restored exterior, and it too has Dundry stone making up surviving doorways and lintels.

ChapterHouse121612This is an excavated “Chapter House” just outside Christ Cathedral on the grounds. Tim Palmer can be seen in the corner making notes. Apparently monks, priests and other church notables would meet in this building and sit on the stone benches just like Tim. The stones in this ruin include original materials (like the Dundry) and a variety of other lithologies.

I had a great time learning about stonework, Medieval building techniques, and the various structural properties of limestones, all thanks to Tim. Tomorrow I’ll be back in the more secular pews of the paleontological meeting. I’m happy to have had this spot of unexpected fieldwork!

Wooster’s Fossil of the Week: A new crinoid species from the Middle Jurassic of southern Israel

November 11th, 2012

About a year ago I showed my good friend Bill Ausich (The Ohio State University) hundreds of crinoid pieces from the Matmor Formation (Jurassic, Callovian) exposed in Hamakhtesh Hagadol, southern Israel. We knew the crinoid represented by all these pieces belonged to the genus Apiocrinites Miller, 1821, but we could not place the species. Bill, crinoid genius that he is, then figured out this was a new species. We now have the pleasure of introducing Apiocrinites negevensis Ausich & Wilson, 2012.

This species of Apiocrinites, the first described from Jurassic tropical latitudes, is distinguished by features in its calyx (or crown or head). A. negevensis has a narrow radial facet and adjacent arms are not in lateral contact. It also has large aboral cup plates. (And it is gorgeous.) In the above image from Figure 1 of our paper, the A. negevensis holotype is shown as 1-3; 1 is a lateral view, radial plate missing from either side of the single preserved radial plate; 2, radial facet; 3, inside of cup with cavity extending to proximale; 4, a partial cup with proximale, one complete and one broken basal plates, and one broken radial plate (note numerous barnacle borings, Rogerella Saint-Seine, 1951, on this specimen).

A holdfast of Apiocrinites negevensis that was attached to the underside of a coral. (From Figure 1 of Ausich and Wilson, 2012.)

Apiocrinites negevensis parts in the  field (Matmor Formation, Hamakhtesh Hagadol, southern Israel). See this post for a discussion of our fieldwork.

The taxonomic category we know as the Crinoidea was established in 1821 by J.S. Miller, who separated the stalked echinoderms from all the others. At the same time he erected the genus Apiocrinites.

Cover of Miller’s 1821 book describing the crinoids, including the new Apiocrinites.

Miller’s (1821) illustrations of Apiocrinites.


Ausich, W.I. and Wilson, M.A. 2012. New Tethyan Apiocrinitidae (Crinoidea; Articulata) from the Jurassic of Israel. Journal of Paleontology 86: 1051-1055.

Feldman, H.R. and Brett, C.E. 1998. Epi- and endobiontic organisms on Late Jurassic crinoid columns from the Negev Desert, Israel: Implications for co-evolution. Lethaia 31: 57-71.

Miller, J.S. 1821. A natural history of the Crinoidea or lily-shaped animals, with observation on the genera Asterias, Euryale, Comatula, and Marsupites. Bryan & Co, Bristol, 150 pp.

Wilson, M.A., Feldman, H.R. and Krivicich, E.B. 2010. Bioerosion in an equatorial Middle Jurassic coral-sponge reef community (Callovian, Matmor Formation, southern Israel). Palaeogeography, Palaeoclimatology, Palaeoecology 289: 93-101.

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

Presenting a Jurassic echinoid story on the last day of GSA 2012

November 7th, 2012

CHARLOTTE, NORTH CAROLINA–The last day of a scientific meeting is always less frantic. About half the attendees have left for home, the exhibitors start to give away merchandise so they don’t have to ship it home, and the speakers are a bit more relaxed. Meagen Pollock and I had talks on this final day of the Geological Society of America annual meeting. It felt good to finally give them to audiences made up in large part by our friends and students. I am simply presenting here a few of my slides, including the title image above. The story you may have read in bits and pieces in the Israel entries at this blog. Here is our abstract.

The second group of Wooster GSA 2012 posters

November 5th, 2012

CHARLOTTE, NORTH CAROLINA–Matt Peppers (’13), a member of the intrepid Team Utah, presented his poster today at the 2012 Geological Society of America annual meeting. Matt is working on the dynamics of the volcanic flows in the Black Rock Desert. Here is his abstract.

Melissa Torma (’13) showed her poster in the same session. She worked in the Negev of southern Israel on the Middle Jurassic Matmor Formation fauna. Her GSA abstract is here.

The third Wooster presenter was Richa Ekka (’13), who worked on Saaremaa Island in Estonia this summer. Her abstract describing her project with a Silurian shallow water dolomitic sequence is here.

Once again it was a joy to watch our students interact with the many geologists who discussed their posters and projects. I now can’t imagine coming to these meetings without an enthusiastic group of our students.

Wooster’s Fossils of the Week: Sea urchin bits (Middle Jurassic of southern Israel)

September 2nd, 2012

Our fossils this week come from our growing collection of material found in the Matmor Formation (Callovian-Oxfordian) of Makhtesh Gadol, southern Israel. In November I will be giving a talk at the annual meeting of the Geological Society of America in Charlotte, North Carolina, on the taphonomy of Matmor regular echinoids (“sea urchins”). The abstract is online. Taphonomy is the study of the fossilization process. In this case it is essentially what happened to the echinoid remains after death and before final burial. This part of the fossilization history can tell us much about the environment of deposition of the Matmor Formation. The image above is one of the rare complete tests (skeletons) in our study. It is probably a rhabdocidarid echinoid, but the preservation is not quite good enough to tell.

Echinoids are especially interesting for this kind of work. (That link will send you to a wonderful site explaining all you’ll want to know about echinoids and their evolutionary history.) They originated way back in the Ordovician Period, about 450 million years ago, and have retained the same general skeletal structure since then. Their response to physical and chemical conditions on the ocean floor has thus been consistent over time, and we can experiment with modern representatives to estimate their decay and disarticulation processes.

Typical test plate fragments from a rhabdocidarid echinoid in the Matmor Formation. The specimen on the right is encrusted by a very thin plicatulid bivalve, which is in turn encrusted by small branching stomatoporid bryozoans.

A flattened and thorny rhabdocidarid spine. The left end has a socket that attached to a tubercle (bump) on the test of the echinoid.

This cool spine was apparently bitten by a Jurassic fish! Wish I had at least one of that fish’s teeth.

The strange swollen sphere with little holes at the base of this echinoid is a cyst that likely formed from a copepod parasitic infection. Neat (and so far undescribed in the literature).

We can conclude that the Matmor Formation was deposited in very shallow, warm marine waters, probably lagoonal (a favorite living place for rhabdocidarid echinoids), that were only occasionally disturbed by storms and “burial events”. The echinoids decayed and disarticulated on the seafloor (a process that takes about a week) and the pieces tossed around for awhile gathering sclerobionts (encrusters, in this case) and experiencing significant abrasion. This matches other evidence from our previous paleontological studies of the Matmor’s depositional environment.


Donovan, S.K., and Gordon, C.M., 1993, Echinoid taphonomy and the fossil record: Supporting evidence from the Plio-Pleistocene of the Caribbean. Palaios, v. 8, p. 304-306.

Greenstein, B.J., 1991, An integrated study of echinoid taphonomy: Predictions for the fossil record of four echinoid families: Palaios, v. 6, p. 519-540.

Greenstein, B.J., 1992, Taphonomic bias and the evolutionary history of the Family Cidaridae (Echinodermata: Echinoidea): Paleobiology, v. 18, p. 50-79.

Greenstein, B.J., 1993, Is the fossil record of the regular echinoid really so poor? A comparison of Recent and subfossil assemblages: Palaios, v. 8, p. 587-601.

Kidwell, S.M. and Baumiller, T., 1990, Experimental disintegration of regular echinoids: Roles of temperature, oxygen and decay thresholds: Paleobiology, v. 16, p. 247-271.

Wooster’s Fossils of the Week: an enigmatic set of tubes (Middle Jurassic of Poland)

August 26th, 2012

The fossils this week celebrate the appearance of an article in the latest issue of Palaios authored by an international team led by my good friend and colleague Michał Zatoń (University of Silesia, Poland). The fossils are strange polka-dotted tubes encrusting Middle Jurassic oncoids and concretions from the Polish Jura — a place I enjoyed visiting last summer with Michał. The fossils were quite mysterious to us, but with the help of our new colleague Yasunori Kano (The University of Tokyo), we think we now have a good idea what they represent. Above you see one of the tubes on a concretion.
The polka dots are actually small, regular divots in the sides of the tubes, as shown above in this view through a scanning electron microscope. It turns out that these concavities are the same size as ooids (rounded carbonate grains) in the depositional environment. In fact, occasional ooids are still in their holes, as shown by the white arrow in the image.
In this cross-section through one of the tubes, each of the exterior holes is lined with a thin layer of carbonate, which is apparently the outer layer of an ooid that was cemented into each space. The tube itself is completely occupied by fine carbonate sediment.

Our hypothesis is that the tubes were formed by some sort of polychaete worm similar to serpulids and sabellids (with which they are associated). The worm may have built a hollow living tube by gluing ooids together and possibly taking advantage of the quick-cementing characteristics of this Jurassic calcite sea. It may have then fed on the surrounding microbial mats that covered the concretion and oncoid surfaces. This hypothesis explains the sessile nature of the tubes, their shape and construction, and their association with thin mineralized layers formed by cyanobacteria.

No polychaetes today are known to build living tubes out of ooids, so these Jurassic forms are thus far unique in the fossil and living record. It was a fun paleontological puzzle to tackle with my friends!

We are proud that our little study was chosen as the cover story for the August 2012 issue of Palaios:

“Unusual tubular fossils associated with microbial crusts from the Middle Jurassic of Poland. Upper left, an exposure of Middle Jurassic (Bathonian) clays at Ogrodzieniec in the Polish Jura; lower left, ESEM pictures of morphology and structure of the Middle Jurassic tubular fossils interpreted as remnants of agglutinated polychaete tubes; lower right, two pictures of tubular fossils encrusting oncoid and concretion; upper right, two pictures of recent agglutinated polychaete tubes from Japan.”


Zatoń, M., Kano, Y., Wilson, M.A. and Filipiak, P. 2012. Unusual tubular fossils associated with microbial crusts from the Middle Jurassic of Poland: agglutinated polychaete worm tubes? Palaios 27: 550-559.

Zatoń, M., Kremer, B., Marynowski, L., Wilson, M.A. and Krawczynski, W. 2012. Middle Jurassic (Bathonian) encrusted oncoids from the Polish Jura, southern Poland. Facies 58: 57–77.

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