Wooster’s Fossil of the Week: Echinoid bite marks from the Upper Cretaceous of southwestern France

November 30th, 2017

Above is another beautiful image from Paul Taylor’s paleontological lab at the Natural History Museum, London. It is one of our fossil oysters (Pycnodonte vesicularis) from the French Type Campanian collected in the town of Archiac in southwestern France on our most enjoyable expedition this past summer. The fine crossing short grooves are bite marks produced by grazing regular echinoids (sea urchins). They form the trace fossil Gnathichnus pentax Bromley, 1975. You can learn more about this type of fossil in a previous blog entry describing Cretaceous Gnathichnus from southern Israel.

This is a good time to update our readers on the French Campanian sclerobiont project. Macy Conrad (’17) has done extraordinary work identifying the hundreds of encrusting bryozoans on our oysters. She is using a series of mugshots of Campanian bryozoans produced by our colleague Paul Taylor to name our specimens as accurately as possible. All the pink you see in these trays represents bryozoans that have been identified.

Here is a closer view. Very distinct patterns of diversification of bryozoans and trace fossils upward through the stratigraphic column are emerging. Macy will continue this work next semester as she finishes her Independent Study thesis. I will be doing my parts as well, but from a bit of a distance: I’ll be on a research leave next semester.

Which leads me to this announcement: Wooster’s Fossil of the Week will no longer be weekly. Since I’ll have other writing goals and travel plans over the next several months during my leave, I will contribute blog entries less frequently. The name “Fossil of the Week” has become a bit of a brand, so I’ll keep it, just no longer post every week (which I’ve been doing since January 2, 2011).

 

 

Wooster’s Fossils of the Week: Barnacle borings from the Cretaceous of southwestern France

November 24th, 2017

Small comma-shaped trace fossils this week in a Cretaceous (Upper Campanian) oyster (Pycnodonte vesicularis) from the Aubeterre Formation of southwestern France. (Locality C/W-747, Plage des Nonnes, to be exact.) These are borings produced by barnacles, which are sedentary crustaceans more typically found in multi-plated shells of their own making. We’ve seen this fine type of boring before in this blog, so some of this information is repeated.

These boring barnacles (yes, I know the joke) are still around today, so we know quite a bit about their biology. (More on how in a minute.) These acrothoracican barnacles drill into shells head-down and then kick their legs up through the opening to filter seawater for food. They’ve been doing it since the Devonian (Seilacher, 1969; Lambers and Boekschoten, 1986).

This particular trace fossil is Rogerella elliptica Codez & Saint-Seine, 1958. It is part of a diverse set of borings collected on our wonderful field trip this past summer to the Bordeaux region with Paul Taylor.

We know so much about boring barnacles because Charles Darwin himself took an almost obsessive interest in them early in his scientific career. While on his famous voyage on the HMS Beagle, Darwin noticed small holes in a conch shell, and he dug out from one of them a curious little animal shown in the diagram below.

Cryptophialus Darwin, 1854

He called it “Mr. Arthrobalanus” in his zoological notes. He figured out early that it was a barnacle, but he was astonished at how different it was from others of its kind. He later gave it a scientific name (Cryptophialus Darwin, 1854) and took on the problem of barnacle systematics and ecology. Eight years and four volumes later his young son would ask one of his friends, “Where does your father do his barnacles?” The diversity of barnacles played a large role in Darwin’s intellectual development and, consequently, his revolutionary ideas about evolution (Deutsch, 2009).

Burrowing barnacle diagram from an 1876 issue of Popular Science Monthly.

References:

Codez, J. and Saint-Seine, R. de. 1958. Révision des cirripedes acrothoracique fossiles. Bull. Soc. géol. France 7: 699-719.

Darwin, C.R. 1854. Living Cirripedia, The Balanidae, (or sessile cirripedes); the Verrucidae. Vol. 2. London: The Ray Society.

Deutsch, J.S. 2009. Darwin and the cirripedes: Insights and dreadful blunders. Integrative Zoology 4: 316–322.

Lambers, P. and Boekschoten, G.J. 1986. On fossil and recent borings produced by acrothoracic cirripeds. Geologie en Mijnbouw 65: 257–268.

Seilacher, A. 1969. Paleoecology of boring barnacles. American Zoologist 9: 705–719

 

Wooster’s Fossils of the Week: Bryozoan encrusting a bryozoan (Campanian of southwestern France)

October 27th, 2017

Today’s post is in honor of Macy Conrad’s (Wooster ’18) poster at the annual meeting of the Geological Society of America, which was held earlier this week. It is also to recognize again the Scanning Electron Microscopy (SEM) genius of our friend Paul Taylor (Natural History Museum, London). The scene is the curving bryozoan ?Oncousoecia sp. encrusting the bifoliate erect bryozoan known as Onychocella aglaia (d’Orbigny, 1851). The specimen is from the Biron Formation (Upper Campanian,Upper Cretaceous), at Cailleau on the north side beneath fishing carrelets near Talmont-sur-Gironde, Charente Maritime, France. We collected from this location this past summer on our wonderful French paleontological expedition. This image comes from a fantastic library of Type Campanian encrusting bryozoan SEM photographs Paul gave us for our identifications in the Wooster lab. I especially like encrusters on encrusters.

This encrusting ?Oncousoecia is, as you can tell from the question mark, not placed for certain in this cyclostome genus, but it is similar to other known examples. This is a closer view of its ancestrula, the first zooid. You can also see pseudopores in the skeleton. The underlying Onychocella aglaia (d’Orbigny, 1851) is a cheilostome bryozoan. This is another reason I find this view interesting: Our larger project examines the dynamics of cyclostome and cheilostome distribution in the Campanian.

This image of Macy’s GSA poster is only symbolic because it is way too small to read. It at least conveys Macy’s neat organization and colorful images. You can read her published abstract on the GSA site. Nice work, Macy, and a major milestone on your way to completing your Independent Study thesis.

References:

Agostini, V., Ritter, M., Macedo, A., Muxagata, E., and Erthal, F., 2017, What determines sclerobiont colonization on marine mollusk shells? PLOS ONE, v. 12, doi.org/10.1371/journal.pone.0184745.

Neumann, M., Platel, J.-P., Andreiff, P., Bellier, J.-P., Damotte, R., Lambert, B., Masure, E., and Monciardini, C., 1983, Le Campanien stratotypique: étude lithologique et micropaléontologique: Géologie Méditerranéenne, v. 10, p. 41-57.

Platel, J.-P., Célerier, G., Duchadeau-Kervazo, C., Chevillot, C., and Charnet, F., 1999, Notice explicative, Carte géologie France (1/50 000), feuille Ribérac, Orléans, BRGM, 103 p.

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

Taylor, P.D. and Zatoń, M. 2008. Taxonomy of the bryozoan genera Oncousoecia, Microeciella and Eurystrotos (Cyclostomata: Oncousoeciidae). Journal of Natural History, v. 42, p. 2557-2574.

Wooster’s Fossils of the Week: Foraminifera clustered around a sponge boring (Campanian of southwestern France)

October 20th, 2017

If all goes to plan, today I leave for the Annual Meeting of the Geological Society of America, held this year in Seattle, Washington. To mark the occasion, this week’s fossil is from a poster Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and I are presenting on Tuesday at the meeting. It comes from our delightful work in southwestern France this summer. There we explored the Type Campanian (Upper Cretaceous) and collected bucketfuls of the oyster Pycnodonte vesicularis. We’ve been studying the sclerobionts on these oysters ever since.

Above are two bore holes formed by a clionaid sponge, making the trace fossil Entobia. A group of foraminiferans has encrusted around one of the holes, making a kind of chimney. Bromley and Nordmann (1971) described a nearly identical occurrence from the Maastrichtian (Upper Cretaceous) of Denmark. It is likely the forams grew around the hole to take advantage of the sponge’s feeding currents, thus making this another example of symbiosis in the fossil record.

I know you can’t actually read this poster, one of a pair Macy and I are presenting, but at least you can see its colorful arrangement! Here’s a link to the abstract. In a later blog post you’ll see the second poster on which Macy is the senior author. My second presenting senior, Brandon Bell, will also get his moment of blog fame soon.

The Geology Department faculty hopes to have numerous posts from the GSA meeting, so more to come!

References:

Breton, G. 2017. Les sclérobiontes des huîtres du Cénomanien supérieur du Mans (Sarthe, France). Annales de Paléontologie 103: 173-183.

Bromley, R.G. and Nordmann, E. 1971. Maastrichtian adherent foraminifera encircling clionid pores. Bulletin of the Geological Society of Denmark 20: 362-368.

Coquand, H. 1858. Description physique, géologique, paléontologique et minéralogique du département de la Charente: Besançon, Dodivers, 420 p.

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.

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

Wooster’s Fossil of the Week: A terebratulid brachiopod from the Upper Cretaceous of southwestern France

October 6th, 2017

Yes, we’ve had a run of French Cretaceous fossils here. This is because we’re in the midst of a major project stemming from summer fieldwork in the Type Campanian of southwestern France. The fossils are delicious, and they are before us every day in the lab.

The above terebratulid brachiopod was found by Macy Conrad (’18) at our Caillaud South locality in the Biron Formation. It is so beautifully symmetrical that it just had to be a Fossil of the Week. I’ve apparently felt this way before about terebratulid brachiopods since I’ve previously written about Triassic, Jurassic and Miocene examples before in this blog. A Cretaceous example at least completes the Mesozoic set.

The above view of our articulated specimen shows the fragmentary smooth dorsal valve of the terebratulid, with the posterior portion of the ventral valve extending upwards at the top. The ventral valve has the characteristic round pedicle opening.

This is the flip side showing only the exterior of the ventral valve. A bit of chalky matrix adheres in the lower left, and the darker circles at the top are a form of silicification called beekite rings.

Here is the side view of our terebratulid, with the dorsal valve on top and larger ventral valve below. You can see why brachiopods were given the common name “lamp shells” because of the resemble to a Roman oil lamp.

References:

Coquand, H. 1858. Description physique, géologique, paléontologique et minéralogique du département de la Charente. Besançon, Dodivers, 420 p.

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

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!

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