Wooster’s Fossils of the Week: Large Miocene barnacles with bioimmurations from Maryland

November 28th, 2014

Barnacle side viewThese two beautiful barnacles are from the Calvert Formation (Middle Miocene) exposed near Parker Creek in Maryland. They are likely of the genus Chesaconcavus. Barnacles are most unlikely crustacean arthropods, cousins of shrimp, crabs and lobsters. Most, like these above, cement themselves head-downwards on a hard substrate like a rock or shell (or boat hull), build a carapace around themselves of calcitic plates, and then filter-feed by kicking their filamentous legs in the water above to catch suspended food. They are entirely marine and usually live in shallow water.
Chesaconcavus top view 585This is a top view of the barnacle pair. We can look straight into the carapace because the opercular plates, which form a kind of door system, have been removed. For barnacles, these are a healthy large size.
Barnacle baseNow we’ve turned the barnacles upside-down to see their attachment surface. The substrate to which they were glued is gone, so we can see the details of the basal plates. The barnacles may have just sloughed off a shell or rock, or maybe they were attached to an aragonitic shell that dissolved away. What is cool here is that we can see other organisms that were on the substrate the barnacles encrusted, including two smaller barnacles completely absorbed within the larger skeletons. This is again an example of bioimmuration. The smaller barnacles look like upside-down cones in this perspective. Note that in the apex of each you can see preserved opercular plates — the insides of the “doors” that are opened for feeding. In the fine-grained skeleton of the larger attachment surface you can see growth lines made by the large barnacles as they occupied the substrate. There are even some small serpentine impressions that may represent soft-bodied organisms that were bioimmured.
Chesaconcavus base detail 585Here’s a closer view of the above basal features. I love the frilly edge of the bioimmured barnacle in the top left.


Kidwell, S.M. 1989. Stratigraphic condensation of marine transgressive records: Origin of major shell deposits in the Miocene of Maryland. Journal of Geology 97: 1-24.

Zullo, V.A. 1992. Revision of the balanid barnacle genus Concavus Newman, 1982, with the description of a new subfamily, two new genera, and eight new species. Paleontological Society Memoir 27: 1-46.

Wooster’s Fossils of the Week: A trace fossil from the Ordovician of Estonia

November 21st, 2014

Hyoliths03_585The fossils above have been in a previous post as examples of hyolith internal molds from the Middle Ordovician of northern Estonia. I collected them on my first visit to the Baltic countries in 2006. This week I want to recognize them again, but this time for the squiggly trace fossils you can just make out on their outer surfaces. These are the ichnospecies Arachnostega gastrochaenae Bertling, 1992. They are the subject of a paper that has just appeared in Palaeontologia Electronica entitled, simply enough, “The trace fossil Arachnostega in the Ordovician of Estonia (Baltica)“. The senior author is my Estonian buddy Olev Vinn. My Polish friend Michał Zatoń, my new Estonian colleague Ursula Toom, and I are co-authors.
399-861 copyAbove is an unpublished image of a gastropod internal mold from the Estonian Ordovician taken by Olev. It shows very well the variable branching nature Arachnostega. This trace was formed by a deposit-feeding organism mining organic material in a sediment-filled shell. It worked along the sediment-shell interface, probably because there was more nutrient value at that margin. The internal mold was formed when sediment filling the shell was cemented and the shell dissolved away, leaving the hard mold behind.
Screen Shot 2014-11-02 at 4.05.40 PMThis is Figure 3.1 in the new paper. Note the variation in the traces as well as the shells it inhabited. The caption as published: Arachnostega gastrochaenae Bertling in a gastropod from Haljala Regional Stage (Sandbian), Aluvere Quarry, northern Estonia. GIT 399-948-1. 2. Arachnostega gastrochaenae Bertling in a gastropod from the Kunda Regional Stage (Darriwilian), Kunda Ojaküla, northern Estonia. GIT 404-355-1. 3. Arachnostega gastrochaenae Bertling in a bivalve from the Haljala Regional Stage (Sandbian), Aluvere Quarry, northern Estonia. GIT 399-1590-1. 4. Arachnostega gastrochaenae Bertling in a bivalve from the Haljala Regional Stage (Sandbian), Aluvere Quarry, northern Estonia. GIT 399-1601-1. 5. Arachnostega gastrochaenae Bertling in a cephalopod from the Uhaku Regional Stage (Darriwilian), Püssi, northern Estonia. GIT 695-12-1.

Our paper analyzes the distribution of Arachnostega through the Ordovician of Baltica, a paleocontinent with a long history, including a collision with Avalonia (western Europe today, more or less) in the Late Ordovician. By plotting the occurrences of Arachnostega over time, we conclude that the makers of Arachnostega likely preferred cool climates and bivalve shells over gastropods. The tracemakers may have also been negatively influenced by the many biotic changes associated with the Great Ordovician Biodiversification Event.

Please check out the article itself. As with all papers in Palaeontologia Electronica, it is open access.


Bertling, M. 1992. Arachnostega n. ichnog. – burrowing traces in internal moulds of boring bivalves (late Jurassic, northern Germany). Paläontologische Zeitschrift 66: 177-185.

Vinn, O., Wilson, M.A., Zatoń, M. and Toom, U. 2014. The trace fossil Arachnostega in the Ordovician of Estonia (Baltica). Palaeontologia Electronica 17, Issue 3; 41A; 9 p.

Wooster’s Fossils of the Week: A new crinoid species from the Middle Jurassic of southern Israel (with a bonus parasitic infection)

November 14th, 2014

1 PitBelowCalyxThese fossils are a joy to present this week. Lizzie Reinthal (’14), Bill Ausich (Ohio State University) and I have a new paper out in the latest issue of the Journal of Paleontology. It is titled: “Parasitism of a new apiocrinitid crinoid species from the Middle Jurassic (Callovian) of southern Israel”. Allow me to introduce Apiocrinites feldmani, a new articulate crinoid species. In the image above we have fused columnals (the “buttons” that make up a crinoid stem) upwards through two radial plates (from the calyx) with two pits and associated swollen columnals (due to a nasty little parasite; see below). A gnarly beast it is, and that’s what makes this creature interesting. I posted another even more twisted specimen earlier.

This new species is named after my friend Howard Feldman of Touro College and the American Museum of Natural History in New York. He was a pathfinder with the Matmor Formation and its fossils in Hamakhtesh Hagadol, Negev, southern Israel.
2 Extracted holdfast 2Apiocrinites feldmani is a small crinoid that lived in a brachiopod-coral-sponge community with a larger cousin named Apiocrinites negevensis (named earlier by Bill Ausich and me). Above we see a pluricolumnal (range of articulated columnals) with the holdfast of another A. feldmani wrapped around them. (I’m also showing off my mad skills at extracting an image from its background.)
3 Gnarly pluricolumnalThis pluricolumnal shows how bad the parasitic infection could get for many A. feldmani specimens. These gall-like growths are responses to some soft-bodied parasite that became embedded within the crinoid skeleton. The crinoid stems were deformed and likely lost considerable flexibility because of these parasites.
4 PitThis is a cross-section through one of the pits in an A. feldmani stem. Note that the narrow end of the pit begins at the articulation between two columnals. The parasite apparently wedged into that space, forcing the crinoid to grow around it as it grew itself. The result was a conical pit with swollen columnals surrounding it.
5 PitPluricolumnalHere we’re looking straight into one of the conical pits with a magnificent swelling around it. You can barely make out the articulation lines of the swollen columnals. Sometimes these cone-shaped pits were closed off by crinoid skeletal growth, presumably because the parasite inside died or otherwise left the premises. We don’t know the identity of this parasite, but we can surmise that it was a soft-bodied filter-feeder that probably gained an advantage from living high above the seafloor on these crinoid stems. Oddly, the larger A. negevensis crinoids in the same community did not have these parasites.

Living crinoids are afflicted by a variety of parasites. There are none today that have this sort of effect on the stems, but there are reports of fossil crinoids with similar pathologies all the way back to the Silurian (Brett, 1978).
6 BivalveBoringCrinoidEven after death these Jurassic crinoid stems provided homes for other organisms. Above is another cross-section through a stem of A. feldmani. “A” is one of the columnals, “B” is a section through an articulated bivalve filled with a relatively coarse sediment, and “C” is a fine sediment that filled in around the bivalve. The bivalve bored into the crinoid stem after death to make a crypt from which it could conduct its filter-feeding with some safety and seclusion.
7 Apiocrinites feldmani specimens 585Finally, here are the type specimens of Apiocrinites feldmani all packed up to be delivered to the Orton Geological Museum at Ohio State University. This museum has a large collection of echinoderms from around the world and so is an appropriate place for our treasures to reside awaiting further study.

This was a fun study that was part of Lizzie Reinthal’s 2013-2014 Independent Study project at Wooster. She concentrated on the taphonomy and sclerobiont successions as we both worked up the parasite and systematic story with our echinoderm expert friend Bill Ausich. There aren’t that many accounts of parasite-host relationships in the fossil record, so we’re proud to add one.

So many beautiful fossils in the Jurassic of southern Israel. More papers to come!


Ausich, W.I. and Wilson, M.A. 2012. New Tethyan Apiocrinitidae (Crinoidea, Articulata) from the Jurassic of Israel. Journal of Paleontology 86: 1051–1055.

Brett, C.E. 1978. Host-specific pit-forming epizoans on Silurian crinoids. Lethaia 11: 217–232.

Feldman, H.R. and Brett, C.E. 1998. Epi- and endobiontic organisms on Late Jurassic crinoid columns from the Negev Desert, Israel: Implications for co-evolution. Lethaia 31: 57–71.

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.

Wilson, M.A., Reinthal, E.A. and Ausich, W.I. 2014. Parasitism of a new apiocrinitid crinoid species from the Middle Jurassic (Callovian) of southern Israel. Journal of Paleontology 88: 1212-1221.

Last Fieldtrip for Climate Change

November 13th, 2014


As the weather cools – the Wooster Geology Climate Change class ventured out in the field one more time. For the remainder of the semester we will try to get some work done. Two sites were visited – the Cedar Creek Mastodon Site and the OARDC.

excavationTwo weeks ago a pit was dug from our coring sites to the Mastodon excavation site. The mission was to link the cores to the archaeological site.


The general stratigraphy of the mastodon site. The muds have a high calcium carbonate content that helped preserve the bones and tusk. Note the plow horizon about 25 cm down – the trip also focused on the agricultural history of Ohio and the role it plays in climate change.

anomalyJeff Dilyard, who hosted us at the site, explains to the class that a GPR (ground penetrating radar) survey identified an anomaly at this location. Isabel probed the area (see below) and “clunked” on a tile.

probingIsabel above used a tile probe to investigate the subsurface (note the chin method she is employing).

tileWhat is a “tile”? above is an old drainage tile from the site. This one is plugged with mud and the plugging was the reason the mastodon was discovered. New tiles were installed last year and the digging brought up the original tooth of the mastodon. Tile and draining of the Midwest allowed for our great agricultural history. In addition, the tile and draining allowed widespread plowing that released the carbon in naturally sequestered organic rich wetland soils to the atmosphere.

in_pitThe crucial end of the backhoe pit where probing and sampling links the bog cores to the mastodon site.


A quick stop ate the Triplett-Van Doren Experimental Plot. For over 50 years a variety of experiments have been underway here. We discussed the side-by-side no-till and mold board plowed sites and their ability to sequester carbon. Not plowing (no-till) sequesters carbon and mitigates erosion. Less carbon dioxide to the atmosphere and less sediment flux on the landscape.


A darker colored soil in the core barrel above shows more carbon in the soil relative to the one below.


A quick stop at Secrest Arboretum to view the famous Dawn Redwoods. Under the proper conditions these trees can grow a meter each year. Our tree-ring data from this stand helps define the optimum conditions for their growth. Planting trees sequesters carbon and helps out in lots of other ways as well.


In addition to the no-till fields and trees at Secrest – there is a meteorological record that spans more than 120 years (note how Tom – far left, seems to be the only student listening to the instructor). These instruments have been keeping track of climate and we will use it to compare with our tree ring study. Our tree ring project asks the question: during the time of European Settlement in Ohio what were the climate conditions like? (precipitation and temperature) and could the widespread deforestation and tile and draining of the region have perturbed the climate (see this video for more on this subject). This question is relevant to the ever-present striving of climate scientists to investigate the relative roles of natural climate variability and anthropogenic change.





Wooster’s Fossil of the Week: Upper Ordovician bivalve bioimmured by a bryozoan

November 7th, 2014

DSC_4503This week’s fossil is a simple and common form in the Cincinnatian Series (Upper Ordovician) of the Ohio, Indiana and Kentucky tri-state area. We are looking above at the base of a trepostome bryozoan that encrusted the outside of an aragonite bivalve shell. The bivalve shell (probably a species of Ambonychia) dissolved away, leaving its impression in the base of the calcitic bryozoan. This fossil is from the Upper Whitewater Formation (Richmondian) in eastern Indiana near Richmond itself.
DSC_4516In this closer view you can see the plications (“ribs”) of the bivalve preserved in negative relief on the attachment surface of the bryozoan. Close examination shows the individual zooecia of the bryozoan exquisitely molding the bivalve topography.

This is a kind of substrate bioimmuration, a preservational mode in which a skeletal organism (the bryozoan here) overgrows another organism (with a soft body or hard skeleton), making an impression of it in its base. The overgrown organisms is rots or dissolves away, leaving the exposed mold. You can also think of it as a kind of external mold produced by a living organism (the encruster). Such “vital immuration” was first described by Vialov (1961), and it is thoroughly covered by Paul Taylor in his 1990 paper cited below.

Again, these fossils are common in the Cincinnatian, and this one is far from being the fanciest. It is the Fossil of the Week because of its very ordinary nature, yet it provides extraordinary information. The aragonitic shell the bryozoan encrusted would have been lost forever after it dissolved if this bryozoan hadn’t occupied it and built a calcitic memorial. I’ve collected now hundreds of these substrate bioimmurations, and they have been critical in many studies, from the preservation of soft-bodied sclerobionts (see Wilson et al., 1994) to the revelation of boring interiors (and thus the behavior of the borers) and skeletal sclerobiont paleoecology. I’m also convinced there are many aragonitic mollusk taxa in the Cincinnatian that are known only through this bioimmuration process. These are fascinating fossils my students and I will continue to collect and study.


Taylor, P.D. 1990. Preservation of soft-bodied and other organisms by bioimmuration—a review. Palaeontology 33: 1-17.

Vialov, O.S. 1961. Phenomena of vital immuration in nature. Dopovidi Akademi Nauk Ukrayin’ skoi RSR 11: 1510-1512.

Wilson, M.A., Palmer, T.J. and Taylor, P.D. 1994. Earliest preservation of soft-bodied fossils by epibiont bioimmuration: Upper Ordovician of Kentucky. Lethaia 27: 269-270.

Wooster’s Fossils of the Week: Upper Carboniferous seed casts from northeastern Ohio

October 31st, 2014

Trigonocarpus trilocularis Hildreth 1838We haven’t had a paleobotanical fossil of the week for awhile, so here are a couple of nice seed casts from the Upper Carboniferous Massillon Sandstone exposed near Youngstown, Ohio. They fall within the “form genus” Trigonocarpus Brongniart 1828. A form taxon is one that may not have any systematic or evolutionary validity, but it is a convenient resting place for taxa that share a particular morphological pattern but can’t be easily classified elsewhere. Trigonocarpus consists of seed casts that are “radially symmetrical, decorticated, and have their surface marked by three prominent ridges” (Gastaldo and Matten, 1978, p. 884). These particular seeds appear to be Trigonocarpus trilocularis (Hildreth, 1837). The taxa here are problematic, of course, because these seeds belong to larger plants that have their own names.
Trigonocarpus trilocularis Hildreth 1838_585These seeds appear to be from medullosalean trees, which were small relatives of today’s cycads. They were common in wetlands throughout North America and Europe during the Carboniferous, especially the Late Carboniferous. The seeds we have were likely attached to small stalks. You can see what appears to be a circular attachment scar above.
Samuel Prescott Hildreth (1783–1863)
Dr. Samuel Prescott Hildreth (1783-1863) was a physician and historian with a keen eye for natural history, especially including fossils and rocks. He was born in Massachusetts of strong Patriot stock and moved to the dangerous territory of Ohio in 1806, settling in Marietta in 1808. Dr. Hildreth is often cited as one of the first scientists in the country west of the Alleghany Mountains. His prolific writing is fast-moving, diverse and interesting, so he must have been a great traveling companion. Dr. Hildreth served in the Ohio Legislature and was on the first Ohio Geological Survey.
HildrethNutThe above is a figure from Hildreth (1837, p. 29) showing the fossil seed he named Carpolithus trilocularis. He wrote that “[t]his nut is probably the fruit of some antediluvian palm”, which is not far from what we think now (apart from the Flood reference!).


Gastaldo, R.A. and Matten, L.C. 1978. Trigonocarpus leeanus, a new species from the Middle Pennsylvanian of southern Illinois. American Journal of Botany 65: 882-890.

Hildreth, S.P. 1837. Miscellaneous observations made during a tour in May, 1835, to the Falls of the Cuyahoga, near Lake Erie: extracted from the diary of a naturalist. American Journal of Science and Arts 31:1-84

Zodrow, E.L. 2004. Note on different kinds of attachments in trigonocarpalean (Medullosales) ovules from the Pennsylvanian Sydney Coalfield, Canada. Atlantic Geology 40: 197-206.

An Epic Geologic Competition in Cuyahoga Valley National Park

October 26th, 2014

VIRGINIA KENDALL, CUYAHOGA VALLEY NATIONAL PARK (CVNP) — What an absolutely awesome day for geology in the field!!  One of my geologic mentors once told me that “every day in the field is a day of vacation”, and today proved to be just that day.  Late October…temperatures above 60 degrees…with the fall colors everywhere!!  I could not have asked for a better day to take my Structural Geology class to “The Ledges”, part of Virginia Kendall, which is only about an hour north of campus.  Essentially, we have a National Park right in northeast Ohio, and fall is the best time to visit the area.

However, we were not just going there for a day hike.  We were on a mission.  I set up a scenario for my class:  CVNP exposes strata that in the subsurface is rich in oil and gas.  The goal for the students was to undertake a complete geologic study (including the stratigraphy, sedimentology, structure, and geomorphology) of the exposed rock in the area as an analog in order to better assess oil and gas fluid migration in the subsurface.  The class was split into two teams — seniors vs juniors.  Each team is not permitted to talk to one another about data collection, analysis, or synthesis.  Eventually, these Research and Development (R&D) Teams will share their findings with Wooster’s Production Experts (Drs. Pollock, Wiles, and Wilson) via a poster presentation later in the semester.

So, while there were literally hundreds of people out for a day hike near The Ledges, Wooster’s geologists were busy at work.  The Ledges is located just south of Happy Days Visitor Center and southeast of Peninsula, OH.

lock-29-location-map_585blogThe area between State Route 303 and Kendall Ledges Road (where there are all the green hiking trails) was our field area for the day.


The R&D Teams quickly noticed the amazing joint sets that are exposed all along The Ledges.  Essentially, we have ledges in this area due to the large fracture system (i.e., joints) affecting the rocks.  These joint sets are very easy to measure and to access due to a wonderful trail system next to the exposures in Virginia Kendall.  Notice above that these joints can be at various orientations and that those in the photo above appear to be nearly perpendicular to one another.

DSC01271_585blogLet me introduce the R&D Team of Woo seniors (’15), from left to right: Coleman Fitch, Zach Downes, Willy Nelson, and Leo Jones.  It appears that they are discussing their team’s strategy early in the day.  Michael Williams (’16), of the opposing team, is in the background.  Is Michael trying to eavesdrop on the opposing team?

DSC01269_585blogTwo members of our R&D team of Woo juniors (’16) are taking notes on this rock exposure.  Eric Parker (left) and Kaitlin Starr (right, white hat) appear to be focused on the gorgeous geology.

DSC01276_585blogThe other two members of the R&D team of Woo juniors (’16) were found hiding in a dark “slot canyon” among the joints.  Michael Williams is in the front, while Adam Silverstein is in the orange hoodie, peeking out from deep inside the “canyon”.  It appears that the juniors are separated from one another!!  It is OK; everyone had maps and GPS units, so perhaps their strategy for the day was to divide and conquer?

DSC01274_585blogWow!!  Check out this entrance to Ice Box Cave, which was formed by the intersection of several joint sets.  Unfortunately, we were not able to go any closer to the cave entrance than this, because…

DSC01273_585blog…the National Park Service is trying to save the bats, which are susceptible to White-Nose Syndrome.

DSC01278_585blogNow, I could not just end the blog without showing you such a wonderful photo.  Check out the amazing set of cross-beds that you can see exposed in the upper half of the photo.  These rocks, which are some of the youngest rocks exposed in CVNP, have been interpreted to be deposited by ancient stream deposits.  Superimposed on the cross-bedding is the characteristic honeycomb weathering that affects many of the sandstone exposures along The Ledges.  And, notice that some of the rocks appear to be more brown or rust colored; some scientists have identified limonite and pyrite (two iron-rich minerals) in the unit.

What an awesome day to be a geologist!!  Who else gets to spend a great fall day with friends, enjoy the weather, learn a little more about rocks, and measure joints along the way?  Geology rocks.



Wooster Geologists return to the Cedar Creek Bog and Excavation Site

October 25th, 2014

DigOverview102514WOOSTER, OHIO–Greg Wiles and I got to experience a bit of field archaeology today at the Cedar Creek Mastodon excavation site. Greg’s Climate change class has visited the site and its associated bog twice this semester: once to do some soil probing and exploration, and then again to extract a core from the bog. This time Greg and I went to consult with the chief archaeologist of the site, Nigel Brush of Ashland University. Nigel wanted our opinions on the stratigraphy of the dig, especially those parts associated with mastodon remains and flint artifacts. The hypothesis the archaeologists are testing is that the mastodon bones and flint blades are part of an ancient butchery site.  It was a joy to join our friends on this fantastic Fall day.

BonesFlagged102514Who doesn’t love an archaeology site? All that enthusiastic hard work with brushes, spades and trowels revealing hidden treasures. Those little orange flags above are tagging bits of mastodon bone that the volunteer excavators have uncovered for mapping and collection. Several schools are represented at this site, and at least a couple dozen citizen scientists.

HannahJim102514Wooster is represented at the dig by archaeology professor Nick Kardulias, along with two of his students shown above. Hannah Matulek is on the left; Jim Torpy on the right.

BoneFragment102514Here is some mastodon bone embedded in one of the excavation walls. The bones are scattered, with some large pieces and many small fragments.

Sieving102514This is the line of sieves for sorting through the excavated sediment. Pleasant enough work today, but I can imagine it’s not so fun in the rain and sleet.

GregSoilProbing102514And now for our bit of work. Greg went off into the bog with a soil probe to plan out a new trench to be dug by the landowner. This trench will help correlate the strata in the excavation with what Greg and his students have cored from the bog.

StratView102514I spent most of my time in the excavations examining the simple layering of the sediments. At the bottom we have a coarse conglomerate with cobble-sized rounded grains. The bones and artifacts lie on top of and among these clasts. Above that unit is a matrix-supported conglomeratic mud with broken rock fragments. At the top is a loam representing the disturbed (plowed) part of the section.

MudWithClasts102514This is a closer view of that middle unit with the “floating” angular rock fragments. My quick assessment (just a suggestion!) is that the coarse gravels beneath are part of a deltaic complex feeding into the bog, which was at the time a marl lake. The mud-with-clasts above it is a debris flow from the surrounding elevations that cascaded down the creek channel and its banks, entombing the bones and artifacts under a slurry of muddy debris. There is scattered charcoal throughout this unit and the top of the cobbles below. Maybe a forest fire denuded the upstream slopes and led to a rain-soaked mudslide? Then again, the charcoal could have come from an ancient barbecue of the mastodon meat.

In any case, Greg and I had a great time visiting our archaeological colleagues on such a fine day.


Wooster’s Fossils of the Week: A pair of molded nautiloids from the Upper Ordovician of northern Kentucky

October 24th, 2014

1 Nautiloid pair 091314Two nautiloids are preserved in the above image of a slab from the Upper Ordovician of northern Kentucky. (I wish I knew which specific locality. This is why paleontologists are such fanatics about labeling specimens.) The top internal mold (meaning it is sediment that infilled a shell now dissolved away) has been covered in a previous blog entry. This week I want to concentrate on the nautiloid at the bottom.

These nautiloids belong to the Family Orthoceratidae McCoy, 1844, which existed from the Early Ordovician (490 million years ago) through the Triassic (230 million years ago). They had conical, aragonitic shells with walls inside separating chambers (camerae) and a central tube (the siphuncle) connecting them. They were swimming (nektic) predators that could control their buoyancy through a mix of gases and liquids in the camerae mediated by the siphuncle.

What is most interesting here is the preservation of these nautiloids. The aragonitic shells were dissolved away at about the same time the internal sediment was cemented, forming the internal molds. These molds were exposed on the seafloor, attracting encrusting organisms. This means the dissolution and cementation took place quickly and in the marine environment, not after burial. This rapid dissolving of aragonite and cementation by calcite is typical of Calcite Sea geochemistry, something we don’t see in today’s Aragonite Seas.
2 Nautiloid siphuncle 091314Above is a close view of the cemented siphuncle of the lower nautiloid, heavily encrusted by a trepostome bryozoan.
3 Bryozoan undersideEven more cool, the outside of the lower nautiloid was encrusted by several trepostome bryozoan colonies. When the shell dissolved it left the undersides of these bryozoans exposed, as seen above. These undersides often contain the remains of shelly organisms the bryozoans encrusted (see the Independent Study project by Kit Price ’13) and even soft-bodied animals (epibiont bioimmuration; see Wilson et al., 1994).

A neat package here resulting from biological, sedimentological and geochemical factors.


Palmer, T.J., Hudson, J.D. and Wilson, M.A. 1988. Palaeoecological evidence for early aragonite dissolution in ancient calcite seas. Nature 335 (6193): 809–810.

Sweet, W.C. 1964. Nautiloidea — Orthocerida, in Treatise on Invertebrate Paleontology. Part K. Mollusca 3, Geological Society of America, and University of Kansas Press, New York, New York and Lawrence, Kansas.

Wilson, M.A., Palmer, T.J. and Taylor, P.D. 1994. Earliest preservation of soft-bodied fossils by epibiont bioimmuration: Upper Ordovician of Kentucky. Lethaia 27: 269-270.

Wooster’s Fossils of the Week: Bivalve borings, bioclaustrations and symbiosis in corals from the Upper Cretaceous (Cenomanian) of southern Israel

October 17th, 2014

Fig. 2 Aspidiscus1bw_scale 585The stark black-and-white of these images are a clue that the fossil this week has been described in a paper. Above is the scleractinian coral Aspidiscus cristatus (Lamarck, 1801) from the En Yorqe’am Formation (Cenomanian, Upper Cretaceous) of southern Israel. The holes are developed by and around tiny bivalves and given the trace fossil name Gastrochaenolites ampullatus Kelly and Bromley, 1984. This specimen was collected during my April trip to Israel, a day recorded in this blog. I crowd-sourced the identification of these corals, and they were highlighted as earlier Fossils of the Week. Now I’d like to describe them again with new information, and celebrate the publication of a paper about them.

En Yorqe'am040914aThis is the exposure of the En Yorqe’am Formation where Yoav Avni and I collected the coral specimens approximately 20 meters from its base in Nahal Neqarot, southern Israel (30.65788°, E 35.08764°). It is an amazingly fossiliferous unit here with brachiopods, stromatoporoid sponges, zillions of oysters, gastropods, ammonites and the corals.

The abstract of the Wilson et al. (2014) paper tells the story: “Specimens of the small compound coral Aspidiscus cristatus (Lamarck, 1801) containing evidence of symbiosis with bivalves have been found in the En Yorqe’am Formation (Upper Cretaceous, early Cenomanian) of southern Israel. The corals have paired holes on their upper surfaces leading to a common chamber below, forming the trace fossil Gastrochaenolites ampullatus Kelly and Bromley, 1984. Apparently gastrochaenid bivalve larvae settled on living coral surfaces and began to bore into the underlying aragonitic skeletons. The corals added new skeleton around the paired siphonal tubes of the invading bivalves, eventually producing crypts that were borings at their bases and bioclaustrations at their openings. When a boring bivalve died its crypt was closed by the growing coral, entombing the bivalve shell in place. This is early evidence of a symbiotic relationship between scleractinian corals and boring bivalves (parasitism in this case), and the earliest record of bivalve infestation of a member of the Suborder Microsolenina. It is also the earliest occurrence of G. ampullatus.”

Fig. 3 BoringPair2bw_scale 585 Paired apertures of Gastrochaenolites ampullatus in the coral Aspidiscus cristatus.

Fig. 4 EmbeddedBivalve1bw_scale_rev 585Polished cross-section through a specimen of Gastrochaenolites ampullatus in an Aspidiscus cristatus coral. In the lower left of the chamber are layered carbonates (A) representing boring linings produced by the bivalve. An articulated bivalve shell (B) is preserved in the chamber. The chamber has been roofed over by coral growth (C).

Thank you very much to Tim Palmer and Olev Vinn for their critical roles in this paper, and, of course, thanks to Yoav Avni, the best field geologist I know.


Avnimelech, M. 1947. A new species of Aspidiscus from the Middle Cretaceous of Sinai and remarks on this genus in general. Eclogae geologicae Helvetiae 40: 294-298.

Gill, G.A. and Lafuste, J.G. 1987. Structure, repartition et signification paleogeographique d’Aspidiscus, hexacoralliaire cenomanien de la Tethys. Bulletin de la Societe Geologique de France 3: 921-934.

Kleemann, K., 1994. Associations of corals and boring bivalves since the Late Cretaceous. Facies 31, 131-140.

Morton, B. 1990. Corals and their bivalve borers: the evolution of a symbiosis. In: Morton, B. (Ed.), The Bivalvia: Proceedings of a Memorial Symposium in Honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. Hong Kong University Press, Hong Kong, pp. 11-46

Pandey, D.K., Fürsich, F.T., Gameil, M. and Ayoub-Hannaa, W.S. 2011. Aspidiscus cristatus (Lamarck) from the Cenomanian sediments of Wadi Quseib, east Sinai, Egypt. Journal of the Paleontological Society of India 56: 29-37.

Wilson, M.A., Vinn, O. and Palmer, T.J. 2014. Bivalve borings, bioclaustrations and symbiosis in corals from the Upper Cretaceous (Cenomanian) of southern Israel. Palaeogeography, Palaeoclimatology, Palaeoecology 414: 243-245.


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