Wooster’s Fossil of the Week: Predatory trace from the Upper Cretaceous of southwestern France

September 15th, 2017

One hole in a shell is unremarkable. Several in a repeating pattern is a story. Above is a right valve (exterior) of the oyster Pycnodonte vesicularis from the Campanian (Upper Cretaceous) of southwestern France. It was collected during our fantastic summer excursion into the Type Campanian at the Archiac location, which had beautiful exposures of the Aubeterre Formation. Note the jagged hole near the center, the subject of this post.Here is the other side of the right valve (the interior). We have multiple such examples in our collection, all in right valves and all near or on what would have been the oyster’s adductor (closing) muscle attachment. (Those of you with sharp eyes may also find some sweet Rogerella borings made by  barnacles, along with several encrusting bryozoan colonies.)A closer view of the hole showing spalled shell layers. (Also more bryozoans!)
Another close view of the above hole on the other side of the valve. It appears that these holes have been produced by some hard object punching through, spalling away the edges. This is what some predators do to shelled organisms to break them apart. Pether (1995) named the “ballistic trace” resulting from stomatopod shrimp predation as Belichnus. Cadée and de Wolf (2013) extended the range of trace makers to include seagulls. In both cases the predators essentially “spear” the shell, with the ensuing hole looking rather squarish and jagged. This is one of the “fracture-shaped bioerosion traces” in the architectural analysis of Buatois et al. (2017).

In our Cretaceous examples, the culprit was most likely some type of stomatopod (a large, diverse and long-lived group) smacking its way into the oysters through the thin right valve. Striking the muscle attachment would be the quickest way of forcing the shell open to reveal all the oysters goodness. The previously oldest example of Belichnus in the fossil record is Oligocene (David, 1997), so this occurrence extends the range back to the Late Cretaceous. That’s not a big deal because the ichnotaxon (trace fossil formal name) is relatively young and those who would look for it are very few. Its stratigraphic range is still maturing.

Update: Katherine Marenco sent this great video of mantis shrimp in action, including a “smasher”.

References:

Buatois, L., Wisshak, M., Wilson, M.A. and Mángano, G. 2017. Categories of architectural designs in trace fossils: A measure of ichnodisparity. Earth-Science Reviews 164: 102-181.

Cadée, G. C. and de Wolf, P. 2013. Belichnus traces produced on shells of the bivalve Lutraria lutraria by gulls. Ichnos 20: 15-18.

David, A. 1997. Predation by muricid gastropods on Late-Oligocene (Egerian) molluscs collected from Wind Brickyard, Eger, Hungary. Malak Táj 16: 5–12

Pether, J. 1995. Belichnus new ichnogenus, a ballistic trace on mollusc shells from the Holocene of the Benguela region, South Africa. Journal of Paleontology 69: 171-181.

 

Wooster’s Fossil of the Week: A rudist clam from the Upper Cretaceous of southwestern France

September 8th, 2017

When we picked up this beautiful fossil in southwestern France this summer, Paul Taylor immediately predicted it would become a Wooster Fossil of the Week. Macy Conrad (’18), Paul and I were on our wonderful expedition in the Type Campanian (Upper Cretaceous) of France. Paul took us to a most unpromising plowed field, claiming there were fossils here from the Maurens Formation. Sure enough we found a pile of large fossils that farmers had picked from their fields. They included probably the most distinctive invertebrate organism of the Late Cretaceous: the rudist clam. Hard to believe these conical objects were clams, but such is evolution. (They have the disconcerting shape and size of other objects found in some French fields: artillery shells!)

The cone itself is the right valve of these sedentary bivalves. The capping valve is the left, as seen here from the top. (Right and left make little sense unless you think of their more traditional bivalved ancestors.) Note that this valve has a reticulate, almost lacy pattern to the shell. Rudists were filter-feeders like most bivalves, but they may have also supplemented their nutrition with photosynthetic symbionts in their mantle tissue. The holes in the top valve may have allowed sunlight to hit the upper mantle.

This stratigraphic chart, courtesy of Platel et al. (1999) via Paul Taylor, shows the Maurens Formation at the top of the Campanian in southwestern France. Our primary Campanian work in SW France is with the three units below (the Biron, Barbezieux and Aubeterre formations).

A typical heterodont clam is in the upper left of this diagram; the rest are elaborate rudist clams. In the lower right is a drawing of the type of rudist photographed above. Diagram from Schumann & Steuber (1997).

Rudists flourished in Cretaceous seas right up until the mass extinction at the end of the period. They are often characterized as reef builders, but most were probably living on soft sediment substrates, like our friend here.

References:

Gili, E., Masse, J.P. and Skelton, P.W. 1995. Rudists as gregarious sediment-dwellers, not reef-builders, on Cretaceous carbonate platforms. Palaeogeography, Palaeoclimatology, Palaeoecology 118: 245-267.

Platel, J.-P. 1996. Stratigraphie, seédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.

Platel, J.-P., Faugeras, P., Mauroux, B., Spencer, C., Charnet, F., Célerier, G., Harielle, B. and Jacquement, P. 1999. Notice explicative, Carte géologie France (1/50 000), feuille Thenon, Orléans, BRGM, 128 p.

Schumann, D. and Steuber, T. 1997. Rudisten. Erfolgreiche Siedler und Riffbauer der Kreidezeit. Städte unter Wasser-2 Milliarden Jahre.-Kleine Senckenberg-Reihe 24: 117-122.

Steuber, T., Mitchell, S.F., Buhl, D., Gunter, G. and Kasper, H. U. 2002. Catastrophic extinction of Caribbean rudist bivalves at the Cretaceous-Tertiary boundary. Geology 30: 999-1002.

Wooster’s Fossils of the Week: Oysters from the Upper Cretaceous (Campanian) of southwestern France

August 22nd, 2017

Wooster’s Fossil of the Week returns from its summer hiatus. It is appropriate, then, to feature as our first fossil of the new season an oyster species prominent in our summer research. This is Pycnodonte vesicularis (Lamarck, 1806), a very common fossil in the Cretaceous around the world. These particular specimens are from the Aubeterre Formation (Upper Campanian, Upper Cretaceous) exposed in the town of Archiac in southwestern France. They were collected by Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and me during our June 2017 expedition. Above is the interior of a deeply concave left valve. The large spot near the middle is the single adductor muscle scar (thus the oyster, like all oysters, is monomyarian). It was a free-living oyster in soft, shallow platform marine sediments. This species has been used for all sorts of studies, from investigating paleoecology and evolution to paleoseasonality (see references below for a start).

This is the interior of the right valve, showing the corresponding muscle scar. The valves are very different in size and shape, so this oyster is termed inequivalved.The exterior of the right valve, with characteristic faint radiating ridges. The tag, by the way, indicates the locality. Every one of our hundreds of oysters is tagged in this way.Macy Conrad (’18) is seen here at the Archiac outcrop collecting specimens of Pycnodonte vesicularis.

A typical bed of P. vesicularis in the Upper Campanian of SW France. This one is exposed along the sea cliffs at Pointe de Suzac.

References:

Brezina, S.S., Romero, M.V., Casadío, S. and Bremec, C. 2014. Boring polychaetes associated with Pycnodonte (Phygraea) vesicularis (Lamarck) from the Upper Cretaceous of Patagonia. A case of commensalism? Ameghiniana 51129-140.

De Winter, N.J., Vellekoop, J., Vorsselmans, R., Golreihan, A., Petersen, S.V., Meyer, K.W., Speijer, R.P. and Claeys, P. 2017. Cretaceous honeycomb oysters (Pycnodonte vesicularis) as palaeoseasonality records: A multi-proxy study. EGU General Assembly Conference Abstracts 19: 4359.

Lamarck, J.B. 1806. Suite des mémoires sur les fossiles des environs de Paris. Annales du Muséum National d’Histoire Naturelle 7: 130-139.

Platel, J.-P. 1996. Stratigraphie, seédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.

Videt, B. 2003. Dynamique des paléoenvironnements à huîtres du Crétacé supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne): biodiversité, analyse séquentielle, biogéochimie (Doctoral dissertation, Université Rennes 1).

Meanwhile, what are the Wooster Paleontologists up to?

July 19th, 2017

Wooster, Ohio — The igneous petrology team has a thorough and entertaining report about their activities in the Wooster geology labs this summer. It has encouraged the summer paleontologists (that would be me and Macy Conrad ’18) to give a progress report. Compared to the high-temperature geochemistry going on in the basement, we are decidedly low-tech upstairs in the Paleo Lab!

Above is our set of fossil oysters (Pycnodonte vesicularis) from the Campanian (Upper Cretaceous) of southwestern France we collected this summer. Each oyster has been cleaned, labeled, and given its own tray. We’ve examined each specimen in a preliminary way to sort out the prominent sclerobionts (hard-substrate dwellers, like encrusters and borings). So far we’ve determined which have bryozoans, serpulids, sabellids, foraminiferans and bivalves attached to them, and we’ve recorded the types of borings we see on each, which makes an impressive list: Entobia, Rogerella, Maeandropolydora, Gnathichnus, Radulichnus, Talpina, Belichnus, Oichnus, and maybe Podichnus.

The diverse encrusting bryozoans are the greatest challenge, and they will produce the most interesting and rich data for our paleoecological and evolutionary hypotheses. These fine creatures are difficult to identify, but we have one of the world’s greatest bryozoologists on our side: Paul Taylor of the Natural History Museum. He gave us a large computer file of scanning electron microscope (SEM) images of the most likely bryozoans we will encounter. We printed each of the 232 images as our “mugshots”. We have started with the uniserial and multiserial cyclostome bryozoans because they’re the easiest recognize. When we see one, we identify the specimen with a pink tag.

This microscope is our most sophisticated equipment so far! Later we will scan our best specimens in London on Paul’s SEM.

Here’s a tray of oysters from the Aubeterre Formation with the beginning of our colorful tagging. Laborious, detailed work, but already we see that the diversity of sclerobionts will generate some good stories.

Future updates will include some of our own photomicrographs!

French oysters. Aged to perfection.

June 30th, 2017

Wooster, Ohio — After our glorious fieldwork in France earlier this month, the Campanian (Upper Cretaceous) oysters Macy Conrad (’18), Paul Taylor (Natural History Museum, London), and I collected are now in our cozy Wooster Paleontology Lab. Now the less glamorous work begins: washing, sorting and labeling the specimens. Macy is shown at work with the collection arranged by localities.

This part of the work requires very low-tech equipment: scissors, paper, and water-soluble white glue. Generations of Wooster students know this procedure. Every specimen must be labelled with a number indicating its locality, even if we have hundreds of them. Paleontologists worry a lot about losing the context of a specimen, so we are obsessive about labelling. First we give a C/W code to each locality, print the numbers by the hundreds, cut them out, and then glue them to appropriate places on each fossil. White glue is great because it is easy to use, non-toxic, and it dissolves in water in case we need to remove or change a label. I learned this simple process in graduate school.Here are some fossil oysters with our coding sheet above.
A close-up of labeled specimens. We place the labels on matrix stuck to the fossil if possible.

These are the customized tags we’ll eventually fill out for each specimen recording our observations of the sclerobionts (hard-substrate dwellers like encrusters and borings). This will keep Macy and me busy for a long time. It’s not dramatic work, but we thought you might like to see all aspects of paleontological research through this project. More to come!

Wooster Geologists in Europe (Summer 2017)

June 10th, 2017

This summer Professor Mark Wilson and Independent Study student Macy Conrad (’18) were in Europe for geological adventures. Professor Wilson first attended a meeting in Vienna, and then traveled to Paris to meet Macy for her IS fieldwork in southwestern France with Dr. Paul Taylor, Merit Researcher at the Natural History Museum, London. Here are the detailed posts of the adventures:

May 27: Wooster Geologist in Austria
May 28: Wooster Geologist in Vienna
May 30: A Wooster Geologist on the Somme Battlefield
June 1: Wooster Geologists begin fieldwork in southwestern France
June 2: A day of geology on the coast of southwestern France
June 4: Wooster Geologists get to work in southwestern France
June 5: A day of collecting Cretaceous fossils on the southwestern coast of France
June 6: A day of rocks and churches in southwestern France
June 7: Revisiting the Gironde Estuary for our last day of fieldwork in France
June 8: Wooster Geologists visit Saint-Emilion in southwestern France

Looking ahead —

June 30: Cleaning and labeling the oysters in Wooster’s paleontology lab
July 19: Meanwhile, what are the Wooster Paleontologists up to?

The above stratigraphic chart, courtesy of Platel (1999) via Paul Taylor, shows the three Campanian (Upper Cretaceous) units studied in southwestern France: The Biron, Barbezieux, and Aubeterre Formations.

Here is Macy at Caillaud with the very white, chalky and fossiliferous Biron Formation. The succeeding Barbezieux and Aubeterre formations look pretty much the same!

Since it was Europe, there were plenty of cultural delights, some with useful outcrops immediately at hand.

Please check out the posts linked above, or follow the tags “Austria” and “France”.

The Natural History Museum in Vienna.

Our final list of localities, with registered localities first, followed by the complete detailed list —

Chemin Aubeterre 155 C/W-745
Caillaud south 162 C/W-746
Plage des Nonnes 164 C/W-747
Archiac 166 C/W-748
Pointe de Suzac 168 C/W-749
Bonnes 171 C/W-750

 

Location GPS Unit Position
Garage Esso Route D17 Aubeterre 153 Biron N45° 16.212′ E0° 10.274′
Route D17 Aubeterre 154 Barbezieux N45° 16.127′ E0° 10.268′
Chemin Aubeterre 155 Barbezieux N45° 16.088′ E0° 10.257′
50 m up lane Aubeterre 156 Barbezieux N45° 16.115′ E0° 10.229′
Back Chateau entrance Aubeterre 157 Aubeterre N45° 16.362′ E0° 10.262′
Car Park Aubeterre 158 Aubeterre N45° 16.344′ E0° 10.176′
Le Maine Roy 159 Maurens N45° 19.383′ E0° 07.885′
Chalais roadcut 160 Biron N45° 16.642′ E0° 02.395′
Cliff north of Mortagne 161 Segonzac – upper N45° 28.963′ W0° 47.943′
Caillaud south 162 Biron N45° 31.805′ W0° 53.629′
Caillaud north 163 Biron N45° 31.916′ W0° 54.206′
Plage des Nonnes 164 Aubeterre N45° 33.534′ W0° 57.895′
Roadcut above Plage des Nonnes 165 Aubeterre N45° 33.627′ W0° 57.894′
Archiac 166 Aubeterre N45° 31.413′ W0° 17.909′
Chez Allard 167 Segonzac N45° 37.040′ W0° 11.546′
Pointe de Suzac 168 Aubeterre N45° 34.933′ W0° 59.352′
Pointe de Suzac south 169 Aubeterre N45° 34.599′ W0° 59.382′
Mirambeau 170 Barbezieux N45° 22.211′ W0° 34.252′
Bonnes 171 Barbezieux N45° 14.735′ E0° 08.935′

Wooster Geologists visit Saint-Émilion in southwestern France

June 8th, 2017

La Barde, France — On our last full day in southwestern France, Independent Study student Macy Conrad (’18) and I had a cultural visit with our host Paul and Patricia Taylor to the ancient town of Saint-Émilion. This town, set in a place that has been inhabited for millenia, is a World Heritage site amidst extensive vineyards and wineries. It has many architectural and historical treasures, which we could only touch upon during our short visit.

This wall is all that remains of a 13th-Century monastery demolished in 1337. It is referred to as the “Great Wall”. The building stones in this wall and most of the town itself are Oligocene limestones, some rich with fossil fragments.

The interior of the Collegiate Church, a mix of Romanesque and Gothic architecture.

12th-Century frescoes still survive in the Collegiate Church of Saint-Émilion. This set shows the grisly story of Saint Catherine.

The cloisters of the Collegiate Church. Imagine the characters who walked through these passages, from Crusaders of the 12th Century to occupying German soldiers of the 20th.

More 13th century frescoes in the cloisters.

The building stones show magnificent weathering over the last 700 years or so.

The most elaborate weathering accentuates burrow systems in the Oligocene limestones. Later building stones in other regions were actually carved to show apparent weathering patterns like these.

Our lunch view. The bell tower is for a church carved into the limestone below. This is another underground church like the one we visited in Aubeterre.

Our lunch in Saint-Émiliion. Yes, fieldwork is tough in southwestern France. Macy Conrad (’18) is on the left, with Patricia and Paul Taylor and then me.

I want to add an image of the war memorial in Saint-Émilion. Every French village, town and city has at least one. They were erected after World War I and usually inscribed with hundreds of names. The World War II local dead are often inscribed later on the bases.

Finally, a few images from our delightful lodgings in the Taylor home at Bard’s End, La Barde. This is the lounge, which held livestock when this was a farmhouse in the 19th and 20th centuries.

The lounge from the other side, with Paul Taylor entering from outside.

The multi-talented Macy was a great help to the Taylors as they assembled a set of furniture from Ikea.

All our dinners were outside on the patio facing the River Dronne. Delightful!

Thank you again to Paul and Patricia Taylor for making this research expedition such a success and pleasure. We will report our results in later posts!

Macy and I leave tomorrow morning on a long train trip to Paris. I then fly home and Macy continues her European adventure with a visit to friends in Norway. Team France is done with fieldwork. The extensive labwork begins this summer with our specimens.

 

 

Revisiting the Gironde Estuary for our last day of fieldwork in southwestern France

June 7th, 2017

La Barde, France — Today Paul Taylor, Macy Conrad (’18) and I had our last fieldwork in France for this expedition. We returned to sites along the eastern shore of the Gironde Estuary to study the Biron Formation (Campanian, Upper Cretaceous), thus completing our three-part stratigraphic survey along with the Barbezieux and Aubeterre Formations. Macy is seen above crouching at the Caillaud South locality.

This is a view of the Caillaud South cliff from the south. The camera can’t convey how very white the rocks are and still keep the rest of the image in a correct exposure. A salt marsh is in the foreground.

The Pycnodonte vesicularis oysters are common at the Caillaud south locality, but they are well cemented into the limestone matrix. We’re looking here at an articulated shell with the right valve on top. This would have been the oyster’s living position.

There is a normal fault exposed in the Caillaud. It is still Biron Formation in either block, but the facies are slightly different on one side from the other.

This part of the estuary was the site of a significant Gallo-Roman settlement.

We also revisited the north side of Caillaud, where again it is Biron Formation with about a meter of Barbezieux on top of the cliff. The structures to the left are fishing towers.

Bryozoans are abundant in this exposure. Here is a nice bryozoan colony, probably the cyclostome Meliceritites, according to Paul.

Talmont-sur-Gironde from the south. This tiny place receives half a million visitors a year. Note the tidal mudflat in the foreground. We were near low tide.

This is an aerial view of the village, courtesy of Wikipedia. It is nearly surrounded by the sea at high tide. The village was founded in 1284 by Edward I of England. In 1652 it was destroyed by the Spanish. I’m surprised it survived World War II.

I’ll end this post with a French wildflower of some type we saw today. It symbolizes the beautiful countryside we had the privilege to explore. Thank you again to Paul and Patricia Taylor for hosting us so elegantly. Paul was also a spectacular field driver on the small country roads, and his knowledge of the fossils and stratigraphy is astonishing.

We have one more day in southwestern France, and then Macy and I head back to Paris.

 

 

A day of rocks and churches in southwestern France

June 6th, 2017

La Barde, France — This is our second-to-last day in southwestern France on this research expedition. Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and I are continuing our study of sclerobionts on Upper Cretaceous (Campanian) oysters. I know the images of us facing into yet another set of white rocks are getting dull, so we’ll get the field shots out of the way first! Above, Macy is looking at the Barbezieux Formation just outside the village of Bonnes, a locality new to us on this trip.

Our second stop was one we visited last week: the Barbezieux Formation exposed in a narrow lane (“Chemin”) in Aubeterre. Another successful day with the Cretaceous oysters and their associates.

We visited two notable churches during our journey today. This one in St. Aulaye is notable for its very old tower and preserved Romanesque facade.

The Medieval carvings around the entrance are delightful. This is a man and what is apparently his donkey.

The second church we visited as in Bourg-du-Bost. This is a Thirteenth-Century building mostly intact.

The interior is richly decorated, and had automated organ music playing as we entered. The lights also switched on and off in a pattern I didn’t catch.

This church is known for its 13th century frescoes still mostly in place with their original colors.

The ceiling of the sanctuary is magnificent. Much attention was given over the centuries to detailed ornamentation and preservation in this relatively small country church. It survived countless wars in this region, including the most devastating ones of the 20th century.

Location GPS Unit Position
Bonnes 171 Barbezieux N45° 14.735′ E0° 08.935′

Wooster Geologists get to work in southwestern France

June 4th, 2017

La Barde, France — After a day of almost solid rain, we woke up the next morning to brilliant weather in southwestern France. Macy, Paul and I drove to the small town of Archiac, where we collected a bag full of gorgeous specimens of the oyster Pycnodonte vesicularis from the Aubeterre Formation.

The oysters could be easily pulled from the marly matrix. Our goal was to collect as many specimens with fossil sclerobionts on them as we could. Sclerobionts are organisms that live in or on hard substrates, in this case it means borings and encrusters.

Thanks to Paul Taylor for this modification of the stratigraphic column from Platel (1999). The three formations we are collecting from are the Biron, Barbezieux, and Aubeterre, all in the Upper Campanian.

We also visited an outcrop of the Segonzac Formation near Segonzac itself so Paul could collect bryozoans. We were at the edge of a vineyard.

The view from our last outcrop was wonderful. Peaceful countryside. That’s our field car parked on the roadside.

Location GPS Unit Position
Archiac 166 Aubeterre N45° 31.413′ W0° 17.909′
Chez Allard 167 Segonzac N45° 37.040′ W0° 11.546′

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