Wooster’s Fossils of the Week: Chaetetids from the Upper Carboniferous of Liaoning Province, North China

September 22nd, 2017

1 Benxi chaetetid 2a 585Three years ago I had a short and painful trip to China to meet my new colleague and friend Yongli Zhang (Department of Geology, Northeastern University, Shenyang). The China part was great; the pain was from an unfortunately-timed kidney stone I brought with me. Nevertheless, I got to meet my new colleagues and we continued on a project involving hard substrates in the Upper Carboniferous of north China. Above is one of our most important fossils, a chaetetid demosponge from the Benxi Formation (Moscovian) exposed in the Benxi area of eastern Liaoning Province. We are looking at a polished cross-section through a limestone showing the tubular, encrusting chaetetids. This month the paper on these fossils has at last appeared.
2 Chaetetid Benxi Formation (Moscovian) Benxi Liaoning China 585This closer view shows two chaetetids. The bottom specimen grew first, was covered by calcareous sediment, and then the system was cemented on the seafloor. After a bit of erosion (marked by the gray surface cutting across the image two-thirds of the way up), another chaetetid grew across what was then a hardground that partially truncated the first chaetetid. This little scenario was repeated numerous times in this limestone, producing a kind of bindstone with the chaetetids as a common framework builder.
3 Chaetetid Benxi cross-section 585Here is the closest view of the chaetetids, showing the tubules running vertically, each with a series of small diaphragms as horizontal floors.

Last week’s fossil was a chaetetid, introducing the group. They are hyper-calcified demosponges, and the classification of the fossil forms is still not clear. Their value for paleoecological studies, though, is clear. This particular chaetetid from the Benxi Formation preferred a shallow, warm, carbonate environment, and it was part of a diverse community of corals, fusulinids, foraminiferans, brachiopods, crinoids, bryozoans, gastropods, and algae. Such hard substrate communities are not well known in the Carboniferous, and this is one of the best.

References:

Gong, E.P, Zhang, Y.L., Guan, C.Q. and Chen, X.H. 2012. The Carboniferous reefs in China. Journal of Palaeogeography 1: 27-42.

West, R.R. 2011a. Part E, Revised, Volume 4, Chapter 2A: Introduction to the fossil hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 20: 1–79.

West, R.R. 2011b. Part E, Revised, Volume 4, Chapter 2C: Classification of the fossil and living hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 22: 1–24.

Zhang, Y.L., Gong, E.P., Wilson, M.A., Guan, C.Q., Sun, B.L. and Chang, H.L. 2009. Paleoecology of a Pennsylvanian encrusting colonial rugose coral in South Guizhou, China. Palaeogeography, Palaeoclimatology, Palaeoecology 280: 507-516.

Zhang, Y.L., Gong, E.P., Wilson, M.A., Guan, C.Q.. and Sun, B.L. 2010. A large coral reef in the Pennsylvanian of Ziyun County, Guizhou (South China): The substrate and initial colonization environment of reef-building corals. Journal of Asian Earth Sciences 37: 335-349.

Zhang, Y., Gong, E., Wilson, M.A., Guan, C., Chen, X., Huang, W., Wang, D. and Miao, Z. 2017. Palaeoecology of Late Carboniferous encrusting chaetetids in North China. Palaeobiodiversity and Palaeoenvironments https://doi.org/10.1007/s12549-017-0300-5

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.

Unknown fossils for the Invertebrate Paleontology class at Wooster

September 1st, 2017

I start my Invertebrate Paleontology classes with an unknown fossil given to each student. I pick something I have enough examples of so that everyone gets the same species. As their first assignment, the students are asked to identify their fossils as specifically as possible using whatever method works, short of asking me or my teaching assistant. Once they’ve identified their specimens, they are then asked to provide an age and likely location of collection. The beautiful fossils above were the unknowns for this semester’s class. Do you know what they are?

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These are specimens of the trepostome bryozoan Prasopora falesi (James, 1884) from the Decorah Formation (Katian, Upper Ordovician) of Decorah, Iowa. They were collected by Rachel Wetzel (’17) as part of our Team Minnesota expedition in 2016. Four of my current students figured this out to the species level! Most knew we were in bryozoan territory.

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!

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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