Wooster’s Fossils of the Week: Belemnites (Jurassic of Wyoming)

November 20th, 2011

This week’s fossils are among the most recognizable. They certainly are popular in my paleontology courses because no one has ever misidentified one. Belemnites (from the Greek belemnon, meaning javelin or dart) were squid-like cephalopods that lived in the Jurassic and Cretaceous Periods. You would never guess their original appearance from the fossils above. These are guards or rostra, internal hard parts that look nothing like the external animal. They are often found in large accumulations called “belemnite battlefields” (Doyle and MacDonald, 1993).
The above image shows a remarkable fossil belemnite in the State Museum of Natural History, Stuttgart, Germany (courtesy of User Rai’ke on Wikimedia). It shows their squidy form and ten equal-sized arms studded with little hooks for holding prey. They probably ate small fish and invertebrates.
The guard or rostrum is solid calcite at its distal end with a phragmocone (chambered shell) at the other. This phragmocone is only rarely preserved. The rostrum above is from the Zohar Formation (Jurassic) of the Golan in northern Israel near Neve Atif.

Belemnites have played an important role recently in sorting out Mesozoic climate change. Their solid calcitic rostra are ideal for examining stable isotopes that fluctuated with water temperature. Dera et al. (2011) showed that the Jurassic had significant climate variations based on the isotopes in belemnite fossils.

Belemnites have a long history in folklore. The English called them “thunderbolts” because they thought they were formed by lightning strikes. The Scottish knew them as “botstones” that cured horses of various ailments. The Swedish thought they were “gnome candles”. The Chinese called them “sword stones”. Much more prosaically, the belemnite is the state fossil of Delaware.
An engraving of belemnite rostra by Captain Thomas Brown (1889).


Brown, Captain T. 1889. An atlas of fossil conchology of Great Britain and Ireland. With descriptions of all the species. Swan Sonnenschein & Co.

Dera, G., Brigaud, B., Monna, F., Laffont, R., Pucéat, E., Deconinck, J-F., Pellenard, P., Joachimski, M.M., and Durlet, C. 2011. Climatic ups and downs in a disturbed Jurassic world. Geology 39: 215–218.

Doyle, P. and MacDonald, D.I.M. 1993. Belemnite battlefields. Lethaia 26: 65-80.

Wooster’s Fossils of the Week: barnacle borings (Middle Jurassic of Israel)

August 7th, 2011

Tiny little trace fossils this week in a Jurassic crinoid stem from the Matmor Formation of the Negev Desert. They are borings produced by barnacles, which are sedentary crustaceans more typically found in conical shells of their own making. These barnacles 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 Period (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 in the Matmor Formation (Callovian) of Hamakhtesh Hagadol, Israel, recently described in Wilson et al. (2010).

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 in 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.


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.

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

Wooster’s Fossil of the Week: Ancient shrimp burrows (Middle Jurassic of Israel)

July 10th, 2011

This week we have a trace fossil, the burrow Thalassinoides. It is represented by one of my favorite images, reproduced above, showing a very large Thalassinoides suevicus in the Zohar Formation (Middle Jurassic, Callovian) of Makhtesh Qatan in the Negev of southern Israel. Holding the scale is Wooster geologist and Independent Study student Allison Mione (’05) during our 2004 Israel expedition. These burrows were originally described as giant desiccation cracks, but I.S. student Kevin Wolfe (’05), Israeli geologist Yoav Avni and I reinterpreted them as burrows in a rocky shore complex (see Wilson et al., 2005).

Thalassinoides is a complex trace fossil that is today made primarily by thalassinidean crustaceans (a type of shrimp; see below). We know a lot about how the burrows are made today by shrimp, and our knowledge is growing about how the ancient systems were excavated, at least in the Mesozoic and later. We have fossil shrimp preserved in Thalassinoides from the Jurassic (Sellwood, 1971) and the Cretaceous (Carvalho et al., 2007).

Pestarella tyrrhena, a modern thalassinidean shrimp. Image from Wikipedia.

Reconstruction of Mecochirus rapax in a Cretaceous Thalassinoides. A) In its burrowing life mode; B) Predominantly horizontal Thalassinoides suevicus burrow systems showing two successive event levels, with Mecochirus in life position. From Carvalho et al. (2007, fig. 3).

The burrow systems in the Zohar Formation of Israel were critical in working out the depositional environment of these carbonate sediments. We could see that first the water was comparatively deep (below wavebase) with worm burrows (Planolites). Then relative sea level dropped and the Thalassinoides burrows cut through the Planolites fabric, showing that the sediment was become stiffer. Finally bivalve borings (Gastrochaenolites) in the same rock indicated that the sediment had cemented into a shallow water hardground. This hardground showed tidal channels cut into its top surface (Wilson et al., 2005).

This work was done with virtually no “body fossils”, meaning evidence of the actual bodies of the organisms living in and on the sediment. Trace fossils, evidence of organism activity, were the only indications of this significant environmental change. This is why the study of trace fossils (ichnology) should be a part of the education of every paleontologist and sedimentologist.


Carvalho, C.N., Viegas, P.A. and Cachao, M. 2007. Thalassinoides and its producer: Populations of Mecochirus buried within their burrow systems, Boca Do Chapim Formation (Lower Cretaceous), Portugal. Palaios 22: 104-109.

Sellwood, B.W. 1971. A Thalassinoides burrow containing the crustacean Glyphaea undressieri (Meyer) from the Bathonian of Oxfordshire. Palaeontology 14: 589-591.

Wilson, M.A., Wolfe, K.R., and Avni, Y. 2005. Development of a Jurassic rocky shore complex (Zohar Formation, Makhtesh Qatan, southern Israel). Isr. J. Earth Sci. 54: 171–178.

A geological and historical tour of the Polish Jura

June 23rd, 2011

SOSNOWIEC, POLAND–A most memorable day traveling through part of the Polish Jura with Michał Zatoń and his delightful family of his wife Aneta and son Tomasz (4 and a half years old). The Polish Jura, also known as the Kraków-Częstochowa Upland, is a long exposure of Upper Jurassic (Oxfordian) limestones in southwestern Poland. We saw a bit of the rock yesterday — a hard white carbonate with a core of lithistid sponge mounds. The area is deeply eroded by karstic processes and so has vertical cliffs, pillars of limestone, sinkholes and caves. Since at least the 14th Century there have been stone fortifications (called “Eagles’ Nests”)  built on these rocks overlooking the deep valleys and access to inner Poland. One of these is the Castle of Pieskowa Skała shown above.

Michał Zatoń showing how the Jurassic limestones are used to effectively lengthen and strengthen the castle walls at Pieskowa Skała. When bedrock is used like this it is called evocatively “living stone”. A similar use of living stone was recorded in this blog two years ago from Jerusalem.

A large karstic pillar called Hercules’ Club near the Castle at Pieskowa Skała. It is juxtaposed with the castle most dramatically when viewed from down in the valley and is included in almost every early drawing or painting of the castle.

Another one of the Eagles’ Nests is Ojców Castle built in the second half of the 14th century by King Kazimierz the Great commemorating the exile and hiding in the area of his father Władysław Lokietek (called “The Elbow-High” because of his stature). The cliffs give this castle (now in ruins) an excellent view of the valley below.

The 14th Century King Władysław Lokietek mentioned above hid from his rivals in this karstic terrain. There is a legend that he took refuge in this particular cave now called “Grota Lokietka”. It is a good excuse to develop the cave into a tourist attraction. We walked through the slippery, dark and cold passages and chambers with a large crowd of enthusiastic Poles examining cave structures and listening to tales of cryptic royalty.

The third castle of the day is not in the Polish Jura, but I’ve included it for completion. It is Będzin Castle in Będzin, a small city next to Sosnowiec and the home of Michał and his family. It too was built in the second half of the 14th Century and obviously took advantage of the local geology, in this case exposures of Triassic limestones. More on the tragic history of Będzin in a later post. We had a very interesting, informative and touching tour of the city center near the end of the day.

I again want to thank my Polish paleontologist host, colleague and friend Michał Zatoń for arranging a wonderful and productive visit. I shall return with Wooster students someday soon. I am certain they will enjoy their visit and work here as much as I have.

A delightful day in the Jurassic of Polish Silesia

June 22nd, 2011

SOSNOWIEC, POLAND–It could not have been a better day for field work: warm with a light, cooling breeze and plenty of leafy green shade. Our team consisted of me and three Polish scientists: Michał Zatoń and Wojciech Krawczyński (I work hard to get those special Polish letters in there!) of the University of Silesia, and PhD student Tomasz Borszcz of the Institute of Oceanology in Sopot, Poland (near the famed city of Gdansk on the Polish Baltic coast). Our goal was to simply see some Jurassic rocks and fossils and talk geology. Mission accomplished.

The top image shows outcrops of remarkable lithistid sponge mounds from the Oxfordian (earliest Upper Jurassic) punching up through the forest cover a few kilometers northeast of Sosnowiec. They formed relatively deep on the Jurassic seafloor and supported an associated brachiopod community.

I was able to visit for the first time one of the localities from which large Middle Jurassic oncoids (cobbles and pebbles covered with the deposits of microbial biofilms) were found and became the basis for a paper co-authored with Michał and Wojciech. In the picture above of a broken cobble you will notice bivalve borings (Gastrochaenolites) penetrating from the outside.

Lunch was in a tavern near the town square of Sławków in the Silesian Highlands. The Polish custom of carving the date of the building on the central roof beam meant we could see right away it was constructed in 1701. (It seems to be preserved in a modern shell of some kind.) I had a typical Silesian meal of rolled beef and dumplings (I think).

A view of the Silesian Highlands from a street in Sławków. This small city is the western terminus of the Broad Gauge Metallurgy Line, a rail system designed “in communist times” to transport iron ore from Ukraine to iron smelters in Poland. The rail gauge in Ukraine and points east is wider than the standard gauge in western Europe.

Our last stop of the day was to a set of deep holes in the middle of a forest. Amateur fossil collectors dug through about two meters of soil and Pleistocene sediment to expose a layer of Callovian (latest Middle Jurassic) rock rich in ammonites, belemnites and other fossils. The three paleontologists, in typical paleontological poses, are from the right Wojciech, Michał and Tomasz.



Quality time with a Polish microscope

June 21st, 2011

SOSNOWIEC, POLAND–A day in the lab with my colleague Michał Zatoń at the University of Silesia. We sorted through two very different paleontological problems with a microscope and a lot of hand waving. The first task was to come up with a hypothesis about the origin of the strange pitted tubes shown above. They are found on hiatus concretions of the Late Bathonian (Middle Jurassic) exposed in Zarki, Poland. We recently described and analyzed the sclerobionts on and in these concretions (see Zaton et al., 2011), but these tubes remained a mystery. We think now that they are remnants of egg cases laid by gastropods (snails) on the undersurfaces of the concretions, and we’ve started on the manuscript.

The coiled encrusting shell below is of a Devonian microconchid originally collected by the keen amateur Brian Bade in western New York and generously donated to our research. This group has some fascinating similarities and differences from its Polish cousins, so we have started a systematic project to determine if they represent a new genus or not. (Brian will be excited to hear this.)

Michal's office/lab in the Faculty of Earth Sciences, University of Silesia.

Tomorrow we set off for fieldwork in the area so I’ll post pictures of the wonderful Polish countryside!


Zatoń, M., Machocka, S., Wilson, M.A., Marynowski, L. and Taylor, P.D. 2011. Origin and paleoecology of Middle Jurassic hiatus concretions from Poland. Facies 57: 275-300.

Wooster’s Fossil of the Week: Coated snails! (Middle Jurassic of France)

June 5th, 2011

In 1988 I had my first visit to France, hosted by my English friend Tim Palmer. We explored Bathonian (Middle Jurassic) limestones in Normandy tracking looking at hardgrounds and other hard substrates. Along the way we stopped in a quarry near the pretty little town of Aubry-en-exmes. There we found thousands of cylindrical white stones. Where broken, we could see they contained some sort of fossil in the center. When I got back to Wooster I cut a few open and polished them down to their centers, revealing the gorgeous snail shells seen above. The shells were originally the mineral aragonite now replaced with coarsely-crystalline calcite.

The snail is known as Bactroptyxis trachaea of the extinct Family Nerineidae in the informal group “Lower Heterobranchia” (which is still around). Cross sections of nerineids like this show their most distinctive feature: elaborate chamber walls inside the whorls of the shell (as seen in a close up below). It was once thought that these complicated structures evolved to strengthen the shell against shell-crushing predators, but now the most common view is that they held special digestive glands to enable them to exploit nutrient-poor organics on carbonate substrates (Barker, 1990).

There is another fossil type here as well: the thick, white calcareous coating of the snails. These are oncolites, a precipitate formed by cyanobacteria. The shells rolled around in a current as the bacteria added layer after layer of calcium carbonate, preserving the shells in such fine detail — and by the thousands.

Reference –

Barker, M.J., 1990. The palaeobiology of nerineacean gastropods. Historical Biology 3: 249-264.

Crinoid success

May 25th, 2011

Will Cary collecting crinoid pieces at a site we creatively call "GPS 055". In the upper left you can see a triangular exposure of marl where Jeff Bowen did his Independent Study work in 2005.

MITZPE RAMON, ISRAEL–One of our missions on this expedition to Israel is to find more and better examples of a distinctive crinoid in the Middle Jurassic Matmor Formation. Crinoids are stemmed echinoderms with a very long geological history, dating back to the Ordovician (or Cambrian, depending on who you believe). They are still alive today so we know much about their biology. They usually have long stems with a holdfast on one end (attaching it to the substrate) and a calyx on the other containing most of the body. The calyx has feathery arms attached at the top that filter the water to catch fine-grained organic particles and pass them down to a central mouth.

Parts of the Matmor Formation have abundant crinoid fragments, all belonging to at least two types of Apiocrinites (a crinoid genus). Two years ago I collected some beautiful specimens, but still lacked some critical pieces. Today Will and I revisited my earlier localities (thank you, GPS technology) and found beautiful specimens.

Our prize is the holdfast pictured above. This is a mass of skeletal calcite the crinoid used to glue itself to the bottom of a coral. The shallow pits apparently represent additional “roots” it used to brace itself in a cavity under the coral. The stem then horizontally protrudes to the right so that the calyx and feeding arms could eventually reach the open seawater. I’ve never seen a holdfast this elaborate in the Jurassic.

Above are typical other parts of this Jurassic crinoid (imaged with all my hotel room photographic skills). At the top are two calyx side pieces showing the interior (left) and exterior (right). The star-shaped object in the middle is the calyx base, seen from the inside. It is flanked by stem fragments, the one on the far right encrusted by an oyster. At the bottom is a crinoid stem with a branching holdfast of another crinoid attached to it.

Mission accomplished as far as the crinoids go!

First field day: Makhtesh Gadol (A large bowl of geological delights)

May 23rd, 2011

MITZPE RAMON, ISRAEL–Today Will Cary, Yoav Avni (our friend from the Geological Survey of Israel) and I worked in the northern end of Makhtesh Gadol (“the large crater”). This geomorphic feature looks a bit like an oblong impact crater, but it is actually a kind of breached anticline known as a makhtesh.

Makhtesh Gadol from Google Maps.

We are interested in the Matmor Formation, a series of Middle Jurassic marls and limestones in the center of the structure. Our special interest is a fossiliferous unit in the Matmor Formation that is found throughout the exposure. It is very rich in crinoids, echinoids, corals and sponges, with a few brachiopods, ammonites and bivalves as well. We want to understand the distribution of this unit and its fossils.

Yoav Avni and Will Cary marching through the Matmor Formation.

If we saw this formation in only two dimensions, as in a typical roadcut, it would be easy to interpret. However, we have it exposed in 3-D because it is heavily dissected by small wadis. More data this way, and far more complications. We learned today that there are distinct facies (rock types characterized by fossils and/or sediments indicating a particular depositional environment) found in very close relationships. The rock units are patchy and the fossils patchy within the lithological patchiness. The number of variables used to predict fossil occurrences is now very large!

All these facies are laterally equivalent in a very small space.

One of the many scleractinian corals in the Matmor Formation. These corals were originally aragonitic and are now replaced by calcite. The replacement process was unusually fine-grained here.

Wooster’s Fossil of the Week: A scleractinian coral (Middle Jurassic of Israel)

May 15th, 2011

In advance of my next field trip to Israel (watch this space!), our highlighted fossil this week is the scleractinian coral Microsolena, a genus named by the French naturalist Jean Vincent Félix Lamouroux in 1821. The specimen above was collected from the Matmor Formation in Hamakhtesh Hagadol in the Negev Desert. It is Callovian in age, specifically the athleta Zone. (I know a lot of details about this area!) This coral is thus roughly 160-165 million years old.

Scleractinian corals appeared first in the Triassic and are the primary coral in today’s oceans. Unlike their extinct Paleozoic cousins, scleractinians have skeletons made of aragonite rather than calcite. Aragonite is relatively unstable and easily dissolves over geological time. Our specimen above has been replaced with the more stable calcite. This means that the exterior is preserved well enough to identify to the genus level, but details in the interior necessary for species determination have been recrystallized beyond recognition.

A nice oyster is still attached to the coral surface. Oyster shells are made of calcite and so are usually preserved very well. You can also see holes in the coral made by boring bivalves and given the name Gastrochaenolites. One of the bivalve borings is in a raised lump of the coral (center top of the image). This is reaction tissue built by the coral in response to the invading bivalve, a clear indication that some of the boring took place while the coral was alive. Most of the corals in the Matmor Formation are heavily bored by bivalves.

Field view of cross-sections of bivalve borings (some with bivalve shells still in them) in a scleractinian coral in the Matmor Formation.

The Matmor Formation is exposed only in the cavity of Hamakhtesh Hagadol. Here it is about 100 meters thick and consists mostly fossiliferous marls and sponge-coral patch reefs. (One of the previous Fossils of the Week is a thecideide brachiopod attached to corals like the one above.) The Matmor sediments were deposited on a shallow marine ramp near the Middle Jurassic equator. It is this equatorial deposition that makes the Matmor such an interesting subject for paleoecological analysis. Most other described Jurassic faunas are in Europe and North America, and they were all formed under more temperate conditions.

Fossil patch reef exposed in the Matmor Formation.


Pandey, D.K., Ahmad, F. and Fürsich, F.T. 2000. Middle Jurassic scleractinian corals from northwestern Jordan. Beringeria 27: 3-29.

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

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

« Prev - Next »