Wooster’s Fossil of the Week: a very large clam (Upper Cretaceous of South Dakota, USA)

June 3rd, 2012

Our version above of the bivalve Inoceramus is actually rather small compared to how big it can get. The record holder is a specimen 187 centimeters in diameter (over six feet) in the Geological Museum of Copenhagen. This Wooster Inoceramus is from the Pierre Shale of South Dakota, a unit my colleague Paul Taylor and student John Sime once explored in some detail.

Inoceramus means “strong pot”, which I assume must refer to its unusually thick shell with calcite prisms oriented perpendicular to the surface. They also had concentric “wrinkles” that make them easily identifiable even in small fragments. In fact, we can even recognize the isolated prisms of inoceramids in thin-sections of sedimentary rocks. This genus was widespread during the Late Cretaceous, being found from British Columbia to Germany. The had very large gill systems that enabled them to live in poorly-oxygenated waters. It makes sense that they are so common in the dark, carbon-rich sediments of the Pierre Shale.
Inoceramus was named by the dapper James Sowerby (above) in 1814, so it is a genus we have known for a very long time. Sowerby (1757-1822) was an Englishman skilled in natural history as well as scientific illustration. He named the first species of the genus as Inoceramus cuvieri to honor the French scientist Georges Cuvier. His illustration of I. cuvieri is below.
Inoceramus was one of the first invertebrate fossils to be the subject of an evolutionary study in a modern way. Woods (1912) studied various species of Inoceramus in the Cretaceous, noting that it apparently underwent rapid intervals of change. My former student Colin Ozanne and his advisor (and my friend) Peter Harries studied Inoceramus and its relatives in the Western Interior Seaway. Their study, published in 2002, showed that inoceramids were greatly stressed by parasites and predators before their final extinction in the Maastrichtian.


Ozanne, C.R and Harries, P.J. 2002. Role of predation and parasitism in the extinction of the inoceramid bivalves: an evaluation. Lethaia 35: 1–19.

Sowerby, J. 1822. On a fossil shell of a fibrous structure, the fragments of which occur abundantly in the chalk strata and in the flints accompanying it. Transactions of the Linnean Society of London XIII: 453-458. Plate XXV.

Woods, H. 1912. The evolution of Inoceramus in the Cretaceous Period. Quarterly Journal of the Geological Society 68: 1-20.

Wooster’s Fossils of the Week: Intricate networks of tiny holes (clionaid sponge borings)

May 13th, 2012

The most effective agents of marine bioerosion today are among the simplest of animals: clionaid sponges. The traces they make in carbonate substrates are spherical chambers connected by short tunnels, as shown above in a modern example excavated in an oyster shell. The ichnogenus thus created is known as Entobia Bronn, 1838. I’ve become quite familiar with Entobia throughout its range from the Jurassic through the Recent (with an interesting early appearance in the Devonian; see Tapanila, 2006).
The holes in this Cretaceous oyster are the sponge boring Entobia; the cyclostome bryozoan is Voigtopora. This specimen is from the Coon Creek Beds of the Ripley Formation (Upper Cretaceous) near Blue Springs, Mississippi. (This specimen was collected during a 2010 Wooster/Natural History Museum expedition to the Cretaceous and Paleogene of the Deep South.)
This is a modern clam shell showing Entobia and several other hard substrate dwelling organisms (sclerobionts).
Entobia was named and first described by Heinrich Georg Bronn (1800-1862), a German geologist and paleontologist. He had a doctoral degree from the University of Heidelberg, where he then taught as a professor of natural history until his death. He was a visionary scientist who had some interesting pre-Darwinian ideas about life’s history.


Bromley, R.G. 1970. Borings as trace fossils and Entobia cretacea Portlock, as an example. Geological Journal, Special Issue 3: 49–90.

Bronn, H.G. 1834-1838. Letkaea Geognostica (2 vols., Stuttgart).

Tapanila, L. 2006. Devonian Entobia borings from Nevada, with a revision of Topsentopsis. Journal of Paleontology 80: 760–767.

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

Wilson, M.A. 2007. Macroborings and the evolution of bioerosion, p. 356-367. In: Miller, W. III (ed.), Trace Fossils: Concepts, Problems, Prospects. Elsevier, Amsterdam, 611 pages.

Wooster’s Fossils of the Week: Three cobble-dwelling oysters from the Upper Cretaceous of southern Israel

March 25th, 2012

These fossils of the week, three well-worn cemented oysters, are highlighted to celebrate the final acceptance this past week of a manuscript that describes their geological setting and significance: Wilson et al., 2012 (see reference below). They are attached to a cobble found at the base of the Menuha Formation (Santonian) near Makhtesh Ramon in southern Israel. These oysters represent the many sclerobionts that inhabited these cobbles. Here is the abstract of the paper:

Reworked concretions have been significant substrates for boring and encrusting organisms through the Phanerozoic. They provide large, relatively stable calcareous surfaces in systems where sedimentation is minimal. Diverse sclerobiont communities have inhabited reworked concretions since the Ordovician, so they have been important contributors to our understanding of the evolution of these ecological systems. Here we describe reworked concretions from southern Israel where they are critical for interpreting the stratigraphy and paleoenvironment of an Upper Cretaceous sedimentary sequence. These cobble-sized concretions (averaging roughly 1000 cubic centimeters) are found at the base of the Menuha Formation (Santonian to lower Campanian, Mount Scopus Group) unconformably above the top of the Zihor Formation (Turonian-Coniacian, Judea Group) exposed in the Ramon region of the Negev Highlands. The concretions are almost entirely composed of micritic limestone, and many are exhumed cemented burrow-fills apparently from 10-20 meters of upper Zihor Formation strata removed by erosion. There are also a few cobbles of dolomitic limestone and rare vertebrate bone. The cobbles are moderately to heavily bored by bivalves (producing Gastrochaenolites) and worms (forming Trypanites), and a few have cemented oysters. They are densely arrayed in a single layer, often touching each other or only a few centimeters apart. The sclerobionts associated with the cobbles, along with their hydrodynamic arrangement, strongly suggest that these cobbles accumulated in very shallow water above normal wave base. Most of them (77%) are encrusted on their top surfaces only, indicating that they were bored in place and not later delivered to a deeper environment by submarine currents. The rest of the Menuha Formation above is a chalk with relatively few macrofossils (primarily shark teeth and oysters) and a few trace fossils (Planolites and Thalassinoides are the most common). These reworked cobbles show that the initial deposits of the Menuha Formation accumulated in very shallow water. This has important implications for the development of the Syrian Arc structures in this region, especially the Ramon Monocline.

Two cobbles in their natural setting: embedded in the chalks at the base of the Menuha Formation.

The beautiful setting south of Makhtesh Ramon. The cliff is an exposure of the resistant Zihor Formation; above it are the white slopes of the far less resistant chalky Menuha Formation. The cobbles are found at the base of the Menuha.

A figure from the manuscript itself showing a cross-section of a cobble. The “T” indicates a Trypanites boring; the “G” shows a Gastrochaenolites boring.

Thank you again to Wooster alumni Micah Risacher and Andrew Retzler and current student Will Cary for helping us collect these specimens!


Wilson, M.A., Zaton, M. and Avni, Y. 2012. Origin, paleoecology and stratigraphic significance of bored and encrusted concretions from the Upper Cretaceous (Santonian) of southern Israel. Palaeobiodiversity and Palaeoenvironments (in press).

A windy, windy day in the Cretaceous

March 16th, 2012

MITZPE RAMON, ISRAEL–Melissa and I finished our work in the Jurassic of Makhtesh Gadol yesterday, so today we went out with Yoav to explore the Upper Cretaceous and Eocene exposures just a few kilometers north of Mitzpe Ramon. This is what we do near the end of each expedition so that we have more ideas for the next. It was cold and very windy on the barren hillsides this morning, but we still saw and learned a great deal.

We examined outcrops of four units: The Ora Formation (Upper Cretaceous) is primarily shales and claystones and below the stratigraphic column shown above. It has an interesting limestone unit composed mostly of rudistid bivalves and their shelly debris shown later below. The Gerofit Formation, also Upper Cretaceous, is a mix of limestones and marls unconformably above the Ora Formation. The Mishash Formation (Upper Cretaceous again) is a chert-rich unit unconformably above the Gerofit here. Andrew Retzler and Micah Risacher, who worked in the region two years ago, will immediately ask, where are the Zichor and Menuhah Formations that are supposed to be between the Gerofit and Mishash? They are absent due to a deep unconformity. On top of the Mishash, above another significant unconformity, are nummulitic limestones of the Avedat Group (Eocene). These three unconformities are all structurally and paleoenvironmentally significant — and they no doubt will be future projects for Wooster Geologists.

Some items of interest in this long section. Just below the Vroman Bank in the Ora Formation is the above cemented horizon with well-distinguished Thalassinoides burrows. These were produced by crustaceans burrowing into stiff mud in shallow waters. This unit is usually not very well exposed, but Yoav and I dropped down into an ancient cistern to see this outcrop.

This is a polished surface at the top of the Vroman Bank in the Ora Formation. Erosion in a small wadi over the centuries smoothed it off. We can see here borings known as Gastrochaenolites, some with outlines of bivalve shells still inside them. This is thus a carbonate hardground.

Some of the units in the Gerofit Formation are lithographic limestones, meaning they are very fine-grained and of uniform composition. You can see in the above photo that the stress pattern around my hammer blow is preserved as a nearly perfect sphere. This rock has been the premier building stone in Israel for millenia. It is known as “Jerusalem Stone” because so many buildings in that city are made of it and its equivalents.

Melissa is standing in what appears to be an ancient quarry for the lithographic limestone. There is a small Iron Age fort made of the stone nearby. Note how bundled up Melissa is. Not the usual image of Israel in this blog!

Finally, all our localities today were on ground that has been part of an IDF training base for decades. There is much discarded military gear around. I thought I would add this old British tin-hat to our blog’s collection of shot-up helmets! (We have German examples already, and somewhere in there is a Russian set.) I neglected to take a photo of a well-worn Egyptian helmet we found this morning.

Wooster’s Fossil of the Week: A holey brachiopod (Lower Cretaceous of southeastern Spain)

February 26th, 2012

This striking and unusual brachiopod is Pygites diphyoides (d’Orbigny, 1847) from Hauterivian (Lower Cretaceous) of Cehegin, Murcia, Spain. Wooster acquired it through a recent generous exchange of brachiopods with Mr. Clive Champion in England. I had heard about this brachiopod genus with a hole through its shell, but never before actually seen one. Thank you very much, Clive.

Pygites diphyoides is a terebratulid brachiopod, an order that is still in existence today. It is commonly called a “keyhole brachiopod” because of the perforation running vertically through the shell. It attached to the substrate with a pedicle (a stem-like device protruding through the pointy end of the shell). Pygites and its relatives appear to have been adapted deep sea, poorly oxygenated conditions, although they are found in shallower facies as well (Dieni and Middlemiss, 1981; Kazmer, 1993; Michalik, 1996).
In this reconstructed cross-section of Pygites (from Michalik, 1996, fig. 4) we can see how the central perforation may have helped with the flow of nutrient-bearing currents through the shell. (Although I must admit to being a bit baffled by the arrows!)
Pygites diphyoides was orginally described as “Terebratula diphyoides” in 1847 by the famous French naturalist Alcide Charles Victor Marie Dessalines d’Orbigny (1802-1857). He was a prolific scientist in many fields, including paleontology, general geology, zoology, archaeology and anthropology. D’Orbigny was a native Frenchman who grew up on the Atlantic coast of his country. He was especially fascinated with marine organisms, even giving the name (in 1826) to a group of protists we now know as “foraminiferans“. He was a proponent of the ideas of his countryman and esteemed zoologist Georges Cuvier during what were exciting times in the development of zoology and paleontology. He was an astonishingly productive scientist, with dozens of reports, papers and books to his credit, and he accumulated a spectacular collection of fossils and zoological specimens. D’Orbigny combined geology and paleontology in very useful ways, becoming one of the earliest biostratigraphers. As a Cuvier disciple, though, he believed the rock record showed a series of successive catastrophes and new creations, so he rejected the developing ideas of evolution during his lifetime (Taylor, 2002).

In 1853 d’Orbigny became professor of paleontology at the Paris Muséum National d’Histoire Naturelle, a new chair created for him. He died at the shockingly young age (for me!) of 54 years.

My friend Paul Taylor at the Natural History Museum in London knows the work of Alcide d’Orbigny very well, and is an expert in his voluminous collections of bryozoans, which you can read about at the link. You will see that the legacy of d’Orbigny is a bit mixed when it comes to his taxonomic contributions, so Paul has his challenges when it comes to sorting out the many names and descriptions this active scientist produced.


Dieni, I. and Middlemiss, F.A. 1981. Pygopid brachiopods from the Venetian Alps. Bollettino della Societá Paleontologica Italiana 20: 19–48.

Kazmer M. 1993. Pygopid brachiopods and Tethyan margins. In: Palfy, J., Voros, A. (eds.), Mesozoic Brachiopods of Alpine Europe. Hungarian Geological Society, Budapest, pp. 59-68.

Michalik, J. 1996. Functional morphology – paleoecology of pygopid brachiopods from the western Carpathian Mesozoic. In: Copper, P. (ed.), Brachiopods: proceedings of the third International Brachiopod Congress, Sudbury, Ontario, Canada, 2-5 September, 1995. CRC Press.

d’Orbigny, A. 1847. Pal. franc., terr. crét., 4, p. 87, pl. 509. Barreme, Lieous, Berrias, Mons, près d’Alais.

Taylor, P.D. 2002. Alcide d’Orbigny (1802-1857). The Linnean 18: 7-12.

Geology and art meet with a ceramic creation from the Cretaceous extinctions

February 16th, 2012

In August 2010 I had a fantastic geologic field trip to the tunnels of Geulhemmmerberg, The Netherlands, to see an unusual exposure of the Cretaceous-Paleogene boundary. There I collected a fist-sized sample of the famous boundary clay, which is found in a variety of thicknesses around the world. I knew just what to do with this sticky handful: give it to my artist friend Walt Zurko at The College of Wooster. He generously made the gorgeous cup-like object above and presented it to me this week.

Walt used every scrap of the clay, even recycling the shavings back into the exterior. There were tiny rock fragments in the original clay sample. They expanded differentially during the heating process and one made a small crack at the lip. I like it — it gives the piece character, like the crack in the Liberty Bell. Walt used several techniques to produce an extraordinary patina on the outside, much of which is not adequately conveyed in my amateur image.

Now we have in the geology department at Wooster a beautiful work of art made from the most famous clay in geological history. Aren’t the liberal arts wonderful?

Inside the tunnels at Geulhemmmerberg, The Netherlands, in August 2010. The rock forming the ceiling is Paleogene and most of the walls are made of Cretaceous limestone. The Cretaceous-Paleogene boundary is visible about a third of a meter down from the top of the wall in the background.

The complicated Cretaceous-Paleogene boundary at Geulhemmmerberg, The Netherlands. This gray clay is one of the thickest boundary clays in the world. I collected a chunk from this section for Walt’s artistic creation.

Wooster’s Fossils of the Week: Bivalve escape trace fossils (Devonian and Cretaceous)

January 29th, 2012

It is time again to dip into the wonderful world of trace fossils. These are tracks, trails, burrows and other evidence of organism behavior. The specimen above is an example. It is Lockeia James, 1879, from the Dakota Formation (Upper Cretaceous). These are traces attributed to infaunal (living within the sediment) bivalves trying to escape deeper burial by storm-deposited sediment. If you look closely, you can see thin horizontal lines made by the clams as they pushed upwards. These structures belong to a behavioral category called Fugichnia (from the Latin fug for “flee”). They are excellent evidence for … you guessed it … ancient storms.
The specimens above are also Lockeia, but from much older rocks (the Chagrin Shale, Upper Devonian of northeastern Ohio). Both slabs show the fossil traces preserved in reverse as sediment that filled the holes rather than the holes themselves. These are the bottoms of the sedimentary beds. We call this preservation, in our most excellent paleontological terminology, convex hyporelief. (Convex for sticking out; hyporelief for being on the underside of the bed.)

The traces we know as Lockeia are sometimes incorrectly referred to as Pelecypodichnus, but Lockeia has ichnotaxonomic priority (it was the earliest name). Maples and West (1989) sort that out for us.
Uriah Pierson James (1811-1889) named Lockeia. He was one of the great amateur Cincinnatian fossil collectors and chroniclers. In 1845, he guided the premier geologist of the time, Charles Lyell, through the Cincinnati hills examining the spectacular Ordovician fossils there. He was the father of Joseph Francis James (1857-1897), one of the early systematic ichnologists.


James, U.P. 1879. The Paleontologist, No. 3. Privately published, Cincinnati, Ohio. p. 17-24.

Maples, C.G. and Ronald R. West, R.R. 1989. Lockeia, not Pelecypodichnus. Journal of Paleontology 63: 694-696.

Radley, J.D., Barker, M.J. and Munt, M.C. 1998. Bivalve trace fossils (Lockeia) from the Barnes High Sandstone (Wealden Group, Lower Cretaceous) of the Wessex Sub-basin, southern England. Cretaceous Research 19: 505-509.

Wooster’s Fossil of the Week: a baculitid ammonite (Cretaceous of Wyoming)

November 13th, 2011

This is a specimen I often place on my Invertebrate Paleontology course lab tests. It is the “straight” ammonite Baculites, which is common enough, but the shell and internal walls (septa) have dissolved completely away, leaving this strangely articulated set of internal molds. This past week, though, it didn’t fool any of my students — they all identified it correctly. They must have a very good paleontology professor.

This is a view of one of the “segments” of the baculitid specimen. It shows the sediment that was pressed up against one of the septa, which then dissolved away. You can barely see branching tunnels made by worms that crawled through the mud looking for deposited organic material, forming trace fossils.

Baculites (meaning “walking stick rock”) was a magnificent ammonite. Its proximal portion was coiled as in all ammonites, but most of the shell (conch) grew straight. They moved like miniature submarines parallel to the seafloor, diving down occasionally to capture prey with their tentacles. They could grow up to two meters long and so must have been impressive predators. The above internal mold of a baculitid is weathering from the Pierre Shale in South Dakota. On the left end the complex sutures (the junctions between septa and conch) are visible; on the right is the extended body chamber.

A happy John Sime (Wooster ’09) holds a nearly complete specimen of Baculites in the collections of the Black Hills Institute of Geological Research. We were on an Independent Study trip in June 2008 to South Dakota, Wyoming and Montana.

A reconstruction of Baculites (foreground) at the Black Hills Institute of Geological Research.

The genus Baculites was named in 1799 by the famous zoologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck (1744-1829). In fact, Lamarck (as he is more usually known) was the first zoologist. He was a soldier as well as a scientist, and he had some of the earliest ideas about the evolution of life. I’m sure he would be proud of my students for their fossil identification skills!


Lamarck J.-B. 1799. Prodrome d’une nouvelle classification des coquilles. Mém. Soc. Hist. nat. Paris, 74.

Wooster’s Fossil of the Week: a venerid bivalve (Upper Cretaceous of Jordan)

September 25th, 2011

This summer I joined a team describing a shell bed in the Upper Cretaceous (lower Campanian, about 80 million years old) Wadi Umm Ghudran Formation exposed northeast of Amman, Jordan (at N 32° 09.241′, E 36° 12.960′, to be exact). I hope someday to visit Jordan, so this work may be my introduction.

The fossils are diverse, including oysters, corals, gastropods and a bivalve of the Family Veneridae shown above. I was struck by how similar this fossil is to its very common modern cousin Mercenaria mercenaria (shown below).

The modern clam shell above, by the way, was one dissected by Invertebrate Paleontology students last year.

These venerid clams are infaunal, meaning they live within the sediment. Thus when east-coasters go “clamming” on a beach they are digging up clams like this from the sand at low tide. They use short tubes (siphons) like watery snorkels to suck in seawater to be filtered through their gills for suspended food particles. Since they live in the sediment their shells are usually clean of encrusters or borers while alive. After death the shells are usually cycled up to the surface and then encrusted and bored as seen below. This is an interesting feature of the Jordanian fossil shell bed — some shells are articulated and clean as the shell at the top; others are disarticulated and heavily bored. Clearly some shells were buried alive and others died long before final internment.

Venerid bivalves are heterodonts, meaning they have “different teeth”. These are not teeth for eating but rather parts of the clam’s hinge structure that hold the valves together. The shapes and sizes of these teeth are used to sort these clams into genera and species. Again, as you can see below, the teeth of the Cretaceous clam are similar to those of the modern shell, but with enough differences to make them separate genera.

The Family Veneridae is entirely marine and includes over 500 living species, many of which are delicious, I’m told. The most common clam consumed in the USA is Mercenaria mercenaria, known as the hard clam or quahog. There are 55 extinct genera in this family, which appeared first in the Early Cretaceous (Cox et al., 1969; Canapa et al., 1996).

This rather plain and common fossil will be the key to deciphering the history of our shell bed in Jordan. Sometimes the most useful fossils are the least flashy.


Canapa, A., Marota, I., Rollo, F. and Olmol, E. 1996. Phylogenetic analysis of Veneridae (Bivalvia): Comparison of molecular and palaeontological data. Journal of Molecular Evolution 43: 517-522.

Cox, L.R. et al. 1969. Treatise on Invertebrate Paleontology, pt. N, Bivalvia vol. 2. The Geological Society of America, Inc. and The University of Kansas.

Mishash, b’gosh

May 29th, 2011

MITZPE RAMON, ISRAEL–Today Will and I drove south, east and north to meet Dr. Yael Edelmen-Furstenburg of the Geological Survey of Israel. She gave us a most excellent tour of the Mishash (pronounced ME-shawsh) Formation (Campanian, Upper Cretaceous) in the Wadi Ashosh region (shown above) near Zuqim and Tsofar in the Negev Desert. We talked much about the fossil fauna, particularly the trace fossils in soft and hard substrates. There could be many future Wooster Independent Study projects in this formation, especially here where it is so diverse.

As seen above, much of the Mishash Formation consists of bands of chert. The folds are syndepositional (formed at the time of deposition) as part of the Syrian Arc deformation. This makes for some very interesting local stratigraphy and depositonal patterns.

The Mishash Formation has exquisite fossil shell beds, often silicified (replaced with silica). Above you can see gastropods and bivalves.

An old Cretaceous friend, the ammonite Baculites, is used to sort out the biostratigraphy of the Mishash. They are identified by the style of ribs they have on the outside of the conch.

Like everywhere else in the Negev Desert, shade is a bonus. We always appreciate the acacia trees, even if their shade is not so complete. Will is standing here next to the Geological Survey of Israel vehicle. Shlomo, an old friend and the driver, gave us quite the off-road adventure. Many people pay for such tours!

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