Wooster’s Fossil of the Week: A faulted oyster ball from the Middle Jurassic of Utah

July 25th, 2014

Split oyster ball 062914I’m returning this week to one of my favorite fossil types: the ostreolith, popularly known as the “oyster ball”. These were lovingly described in a previous blog entry, so please click there to see how they were formed and some additional images. They are found almost exclusively in the Carmel Formation (Middle Jurassic) of southwestern Utah.They are circumrotatory (a fancy word for “rolling around while forming”) accumulations of small cup-like oysters along with minor numbers of plicatulid bivalves, disciniscid brachiopods, cyclostome bryozoans (see Taylor & Wilson, 1999), and mytilid bivalves that drilled borings known as Gastrochaenolites. They are nice little hard-substrate communities originally nucleated on bivalve shells (Wilson et al., 1998).

oyster ball close 062914Here is a close view of the oyster valves on the outside of the ostreolith. They are attached to similar valves below them, and it is oysters all the way to the center.

What is special about our specimen here is that it managed to obtain a fault right through its center! The chances of this happening are slim, given that they are relatively rare in the rock matrix. The faulting was probably during the Miocene related to a “left-lateral transfer zone that displaces north-south–trending crustal blocks of the eastern Basin and Range Province to the west” (Petronis et al., 2014, p. 534). This is an interesting tectonic region between the Basin and Range Province and the Colorado Plateau.

Slickenfibers 062914A close view of the fault surface shows it is a striated slickenside. The striations (called slickenlines) are parallel to the direction of movement, not that we have to guess when we look at the ostreolith itself. There are also calcitic deposits here formed during faulting called slickenfibres. These elongated crystals have tiny step-like breaks in them that show the actual direction of movement.

Another nice specimen combining paleontology and structural geology.


Petronis, M.S., Holm, D.K., Geissman, J.W., Hacker, D.B. and Arnold, B.J. 2014. Paleomagnetic results from the eastern Caliente-Enterprise zone, southwestern Utah: Implications for initiation of a major Miocene transfer zone. Geosphere 10: 534-563.

Taylor, P.D. and Wilson, M.A. 1999. Middle Jurassic bryozoans from the Carmel Formation of southwestern Utah. Journal of Paleontology 73: 816-830.

Wilson, M.A., Ozanne, C.R. and Palmer, T.J. 1998. Origin and paleoecology of free-rolling oyster accumulations (ostreoliths) in the Middle Jurassic of southwestern Utah, USA. Palaios 13: 70-78.

Wooster’s Fossils of the Week: Silicified productid brachiopods from the Permian of West Texas

July 18th, 2014

Productids ventral valves 052514The three beauties above are productid brachiopods from the Road Canyon Formation (Middle Permian, Roadian, approximately 270 million years old) in the Glass Mountains of southwestern Texas. They are part of a series we’ve done on the silicified fauna of a block of limestone we dissolved in the lab many years ago. The calcitic shells have been replaced with silica during the process of fossilization, so they can be extracted from the carbonate matrix with hydrochloric acid. This is a primary way we can see delicate parts of a fossil, like the long hollow spines above. Ordinarily these would have been lost under the usual processes of taphonomy.

The specimens are highly convex ventral valves, which are characteristic of the productid brachiopods. The long hollow spines helped distribute the weight of these brachiopods on soft and unstable substrata, like a sandy or muddy sediment. This is often called “the snowshoe effect”. Below is a diagram reconstructing productid brachiopods on a sandy substrate with their spines keeping them from sinking below the sediment-water interface.

productid diagramProductid Permian Texas 585Here is a closer view of the ventral valve exterior of one of these productid brachiopods. You can see how delicate the hollow spines are.

Productid interior ventral Permian Texas 585This is the interior of the same valve. Each spine has a hole connecting it to the inside of the shell. The mantle, which secretes the shell and has other physiological functions, extended out into each spine to build its length and possibly carry some sort of sensory abilities.

I have been unable to identify these brachiopods because of the bewilderingly large number of them described by Cooper and Grant in the 1960s and 1970s. Maybe one of our readers can give it a shot!


Brunton, C.H.C., Lazarev, S.S. and Grant, R.E. 1995. A review and new classification of the brachiopod order Productida. Palaeontology 38: 915-936.

Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas. American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Cooper, G.A. and Grant, R.E. 1972. Permian brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology 14: 1–228. [and five other volumes]

Shiino, Y. and Suzuki, Y. 2007. Articulatory and musculatory systems in a Permian concavo-convex brachiopod Waagenoconcha imperfecta Prendergast, 1935 (Productida, Brachiopoda). Paleontological research 11: 265-275.

Wooster’s Fossils of the Week: Silicified chonetid brachiopods from the Permian of West Texas

July 11th, 2014

Dyoros planiextensus Cooper and Grant 1975 585Above are four valves of the chonetid brachiopod Dyoros planiextensus Cooper and Grant, 1975. They are preserved by silicification and were recovered from a block of the Road Canyon Formation (Roadian Stage of the Guadalupian Series of the Permian System) from the Glass Mountains of southwestern Texas. It is from the same unit and location as the rhynchonellid brachiopod presented two weeks ago in this blog. (Please see that entry for additional links and explanations of the preservation.)

It took me awhile to work out the systematics of this species, so I must show you in exquisite detail —

Phylum Brachiopoda
Class Strophomenata Williams et al., 1996
Order Productida Sarytcheva and Sokolskaya, 1959
Suborder Chonetidina Muir-Wood, 1955
Superfamily Chonetoidea Bronn, 1862
Family Rugosochonetidae Muir-Wood, 1962
Genus Dyoros Stehli 1954
Species Dyoros planiextensus Cooper and Grant, 1975

Like music!

The chonetid brachiopods (at the suborder level) can be extremely common in Permo-Carboniferous units. I’ve seen hillsides in southeastern Ohio that seemed coated with them as they eroded from the shales beneath. They were well adapted to living on soft sediments with their flat, thin shells. In life they had a series of small hollow spines extended from the hinge line (the straight parts of the shell where the valves articulated; top in the photos above) to help anchor them as juveniles and possibly serve as extensions of their sensory systems.

Just a short entry this week. If all proceeded by plan, I’m somewhere deep in China right now!


Cooper, G.A. and Grant, R.E. 1975. Permian brachiopods of West Texas, III. Smithsonian Contributions to Paleobiology 19:795-1921.

Racheboeuf, P.R., Moore, T.E. and Blodgett, R.B. 2004. A new species of Dyoros (Brachiopoda; Chonetoidea) from Nevada (United States) and stratigraphic implications for the Pennsylvanian and Permian Antler Overlap assemblage. Geobios 37: 382-394.

Stehli, F.G. 1954. Lower Leonardian Brachiopoda of the Sierra Diablo. Bulletin of the American Museum of Natural History 105: 257-358.

Wooster’s Fossil of the Week: A barnacle and sponge symbiosis from the Middle Jurassic of Israel

July 4th, 2014

Barnacle boring bioclaustration 1

[Programing note: Wooster's Fossil of the Week is now being released on Fridays to correspond with the popular Fossil Friday on Twitter and other platforms.]

This week’s fossil is again from the Matmor Formation (Middle Jurassic, Callovian) of southern Israel. (What can I say? We have a lot of them!) We are looking above at a crinoid pluricolumnal (a section of the stem made of several columnals) almost completely encrusted by a calcareous sponge (the sheet-like form with tiny pores). A round oyster is attached to the sponge in the lower center. In the left half you see the items of our interest this week: ovoid holes produced by barnacles. This specimen was studied by Lizzie Reinthal (’14) as part of her Senior Independent Study on the taphonomy of the Matmor crinoids.
Barnacle boring bioclaustration 2These barnacle holes are interesting because we can see in this closer view that the sponge grew around them. There is thickened sponge wall at the margins of the holes, and the feature in the middle is a thick mound built around one of these holes. The barnacles in the holes and the sponge were living together. If they weren’t either the sponge would have overgrown the empty holes or the barnacle would have cut through the dead sponge skeleton. This is an example of symbiosis. It would be a facultative relationship because the sponge and barnacle did not need each other to survive; each does just fine without the other. It could be considered parasitic if the barnacles acquired nutrients the sponge would have ordinarily received, or vice versa.
Barnacle boring bioclaustration 3This third view is of the edge of the sponge skeleton as it partially overlaps the barnacle holes. Now we see the nature of the intergrowth. The barnacle holes are actually borings into the crinoid pluricolumnal below. They are the trace fossil called Rogerella, which we have seen before in this blog. The sponge grew along the crinoid substrate covering all sorts of small holes, cracks and crevices, but when it reached these borings living barnacles were still in them filter-feeding away with their filamentous legs. The sponge thus laid its skeleton right up to the hole edges, eventually surrounding them with their spongy matrix.

The holes are borings, a kind of trace fossil. The structure created when the sponge surrounds a living boring barnacle like this is more difficult to name. It is not technically a bioimmuration (see Taylor, 1990) because the barnacles were not passively subsumed within the sponge skeleton. It may be a bioclaustration (Palmer and Wilson, 1988) because the sponge adapted its skeleton to isolate and surround the barnacle. I think we can at least say these are trace fossils in the ethological (behavioral) group called Impedichnia (Tapanila, 2005) because the barnacles acted as impediments, or limiting factors, to the growth of the sponge.

I love these examples of symbiosis in the fossil record, and the interesting debates about their interpretations.


Cónsole‐Gonella, C. and Marquillas, R.A. 2014. Bioclaustration trace fossils in epeiric shallow marine stromatolites: the Cretaceous‐Palaeogene Yacoraite Formation, northwestern Argentina. Lethaia 47: 107-119.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939–949.

Tapanila, L. 2005. Palaeoecology and diversity of endosymbionts in Palaeozoic marine invertebrates: Trace fossil evidence. Lethaia 38: 89–99.

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

Vinn, O. and Mõtus, M.A. 2014. Symbiotic worms in biostromal stromatoporoids from the Ludfordian (Late Silurian) of Saaremaa, Estonia. GFF (in press).

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.

Last day of work at the Natural History Museum, and some special visitors

June 25th, 2014

pdt16846 copyLONDON, ENGLAND — I know it is an acquired taste, and way too esoteric, but I think the above scanning electron micrograph is beautiful. This is an undescribed species of the cyclostome bryozoan Corynotrypa from the Upper Ordovician Bromide Formation of Oklahoma. There are all sorts of juicy details in this image that tell us about the growth and development of this extinct colonial organism, its paleoecology, and even its evolutionary relationships. It is also just plain exquisite. Paul and I had a productive and enjoyable time scanning this and several other Ordovician bryozoan specimens in our exploration of the early cyclostomes.

Paul and I stumbled upon something very surprising in our scanning this morning. We think it is potentially significant. Sorry for the tease, but we’re not ready to announce it yet. I just want to say again that we had a very good day of science!

Davis family 062514This afternoon we had great visitors to the Natural History Museum in London and its behind-the-scenes collections. From the left is Hudson Davis, his grandfather the prominent structural geologist George Davis (Wooster ’64), another grandson named, curiously, George Davis, and Merrily Davis. Paul (on the far right) gave all of us an excellent tour of the museum, including special collections and an emphasis on the awesome bryozoans. Paul and I were very impressed at how well prepared the Davis family was for this experience. They had excellent questions and a deep appreciation for natural history. It was also good to see a bit of Wooster here!

Photo by George Davis.

Photo by George Davis.

A day’s work in the Natural History Museum, London

June 23rd, 2014

NHM exterior 062314LONDON, ENGLAND — This is one of my favorite places in the world. It is a Victorian cathedral of science: The Natural History Museum in London. Today I began three intense days of research with Paul Taylor in his paleontology lab.

Lab desk 062314Here is my lab station. Today I did the most alpha level of alpha paleontology: sorting fossils for later detailed examination. You see above trays of specimens sitting to the right of the microscope. My task was to examine each fossil for the encrusters (sclerobionts) on its surface, as well as any other interesting features like bioerosion or evidence of biotic interactions. After I finished these trays –

Specimens to go 062314– there were plenty of other trays to plow through. Paul and I had an assembly line going where he washed the fossils and I sorted.

zigzag 062314This beautiful creature in one of Paul’s excellent Scanning Electron Microscope (SEM) images is what we were primarily looking for today. It is an undescribed zig-zag cyclostome bryozoan from the Bromide Formation (Upper Ordovician, Sandbian) of the Arbuckle Mountains in Oklahoma. Paul and other colleagues from the Natural History Museum collected the trays of fossils we’ve been sorting while on an expedition to Oklahoma in 2013. This bryozoan type encrusts larger bryozoans, brachiopods, and other shelly substrates in this assemblage. Tomorrow we will use the SEM on the new specimens we discovered today in the expedition’s materials.

I also give a seminar at the museum tomorrow afternoon on Wooster Geology work in the Jurassic of Israel. Yikes.



Wooster Geologist in London at the British Museum

June 22nd, 2014

Front BM 062214LONDON, ENGLAND — I arrived late last night in London after a series of delays in my departure from Poland, so I was pleased that today was a Sunday so I could chill a bit before work with Paul Taylor tomorrow. If I can visit one place in London (other than the Natural History Museum, of course) it is always the British Museum (above). As you can see, the weather was spectacular — and the crowds took advantage of it. I thought I’d just highlight a set of exhibits that is very cool, despite the fact that few visitors seem to spend much time with it.

Enlightenment textIt is the “Enlightenment: Discovering the World in the Eighteenth Century” gallery. I think it is well done and highly evocative, at least for scientists. My favorite part is there on the right end: “The Natural World”.

Enlightenment cabinetThe cases are deliberately old-timey to evoke the “cabinets of curiosity” 18th Century polymaths had for their collected treasures. In fact, some of these cabinets themselves date back to that period. Here we see rocks, fossils, plants and animals collected by Enlightenment explorers, philosophers, historians, and just plain rich guys. These were the very specimens that thrilled and puzzled some very great minds — not that we don’t have plenty of mysteries remaining about them.

Mastodon BM 062214This is a mastodon jaw (Mammuthus americanum) collected “near the Ohio River” and given to the museum in 1768. It was called “The Unknown American” and thought to be from some extinct carnivorous elephant-like beast.

Smith fossils BM 062214My favorite set of fossils here was collected and used by the famous William “Strata” Smith (1769-1839)  in his pioneering work on geological correlation and mapping. Fossils like these were crucial to working out the relationships of rock layers (“strata”) and early concepts of Earth history. There is something inexplicably enchanting about seeing objects handled by past luminaries.

Schist sarcophygusOn an unrelated but geological note, I have a complaint about a small number of the displays. This ancient Egyptian sarcophagus is an example. What is the rock type here? I’d say a basalt or maybe a fine-grained granodiorite (like the Rosetta Stone).

Schist closer BM 062214Here’s a closer view of the sarcophagus. The sharpness of the carving shows how fine-grained and massive this rock seems to be. (I know the rules — no scratching the artifacts to test their properties.) But what does the sign say?

Schist signBlack schist? No way. Schist is foliated and flakey and most decidedly not massive and so superbly suited to carving. Maybe someone will correct my notion of “schist”, but right now I’m certain this part of the label is wrong. I’ve seen this fairly often in museum displays: the rock types given don’t always match what appears to be the actual lithologies. Not enough geoarchaeologists to go around, I suppose.

Romano British hed 062214Here’s a cool Romano-British sculpture that did have a proper identification as “limestone”. (And to be fair, most are correctly labeled.) I liked this artifact in particular because you could look closely at the broken bits –

Ooids 062214The rock is made primarily of these little calcitic spheres called ooids. I would not be at all surprised to learn that this is a Portlandian (Upper Jurassic) limestone from southern England.

It was a fun day at one of the world’s finest museums. Tomorrow I begin work at another.

Wooster’s Fossil of the Week: A silicified rhynchonellid brachiopod from the Permian of West Texas

June 22nd, 2014

Rhynchonellid crura Permian Texas 585Sometimes fossils can be more useful when broken than whole. Above is a much-abused rhynchonellid brachiopod from the Road Canyon Formation (Middle Permian, Roadian, about 270 million years old) found in the Glass Mountains of southwestern Texas. It is part of a set of silicified fossils we etched out of a block of limestone in the last century. The shell has been replaced with resistant silica, so it was easy to extract from the limestone matrix with a long bath in hydrochloric acid that dissolved the carbonate but left everything else. The fossils are like delicate little glass husks. We’ve featured them in this blog several times.

Update: Matt Clapham kindly corrected me in the comments, and it is worth repeating in the text: “It’s Stenoscisma. The large spoon-shaped projection is actually called a spondylium, formed from merged dental plates and it’s quite distinctive for the Stenoscismatidae. The crura are broken but still visible in your specimen; they are the little struts parallel to the narrowest part of the spondylium. There are five Stenoscisma species that appear common in the Road Canyon Formation and yours looks most similar to Stenoscisma triquetrum to me (weakly sulcate with ribs that are somewhat subtle but still extend near the beak).” I made a bonehead mistake labeling the spondylium incorreectly, hence the “c”. Here’s to the value of Twitter, blogging, and knowledgeable colleagues!
Rhynchonellid Permian Texas 585Here’s the dorsal side of the specimen for completion. The exterior is in poor shape.

I’d love to identify this specimen to at least the genus level [update: see above and the comments!], but there is not enough detail preserved, at least for my skill set. The Permian brachiopods of West Texas were famously studied by G. Arthur Cooper and Richard E. Grant in the 1960s and 1970s. The numbers of species are overwhelming in this ancient reef system, and almost all of them are preserved in this delicate way.


Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas. American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Cooper, G.A. and Grant, R.E. 1972. Permian brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology 14: 1–228. [and five other volumes]

Olszewski, T.D. and Erwin, D.H. 2009. Change and stability in Permian brachiopod communities from western Texas. Palaios 24: 27-40.

The Triassic limestones at Góra Świętej Anny, Poland

June 18th, 2014

Gora sw. Anny signSOSNOWIEC, POLAND — My friends Michał Zatoń and Tomasz Borszcz took me on a very pleasant day trip to Góra Świętej Anny in southwestern Poland about an hour’s drive northwest from Sosnowiec. This is a place of considerable geological and historical interest. It is an eroded volcanic caldera and the easternmost occurrence of the fine-grained igneous rock basalt in Europe. You would think I’d be able to show you at least a bit of basalt, but we saw only the surrounding Middle Triassic limestone country rock. (Sorry, Dr. Pollock.) We’ll talk about the history later. Now we’ll look at the geology.

Muschelkalk long 061814Here is a great exposure of the Muschelkalk, a Middle Triassic sequence of limestones and dolomites that extends across central and western Europe. This is its best exposure in Poland. The rock appears very massive in this old quarried wall, but it actually has many distinct layers. Michał is standing at the top of stairs that lead down into a massive Nazi amphitheater called a Thingstätte, but more on this later.

Muschelkalk brachs 061814Part of the Muschelkalk unit is dominated by terebratulid brachiopods, many of which are seen on this slab.

Triassic encrinite 061814The topmost Muschelkalk here contains thick beds made primarily of crinoid skeletal debris, a kind of deposit known as an encrinite. We’ve seen encrinites before in this blog.

trace fossil sign 061814You don’t often see informative signs dedicated to the description of a trace fossil type. Rhizocorallium commune is the most common ichnofossil in this part of the Muschelkalk. It is a ropy, loopy tube produced in this case by crustaceans, probably including the decapod shrimp Pemphix.

Rhizocorallium 061814The slabs used to pave the walks and plazas in this area are filled with Rhizocorallium commune traces.

View 061814Finally, this is a view west from Góra Świętej Anny towards the Oder River. It is the highest place around, dominating this fertile valley rich with farms, mines and factories. This will be the reason it is so culturally and historically significant in Silesia.

A new Polish colleague (and cool dinosaur model)

June 17th, 2014

T rex 061714SOSNOWIEC, POLAND — The above full-scale model of Tyrannosaurus rex is one of my favorite dinosaur reconstructions. It sits in front of the Earth Sciences Building at the University of Silesia. Since it is outside the lighting is always dramatic, and the artists paid close attention to even tiny details like the reported coat of downy feathers on its back (see below).

T rex feathers 061714The roughening you see in the upper half of the image represents the feathery covering. We can only imagine what colors were present in the original.

Alina MW 061714Here is a new Polish colleague I met this morning. Alina Chrząstek is a paleontologist at the University of Wroclaw. She is a specialist in invertebrates and trace fossils. A few months ago she sent me photos of rock and fossil specimens she had questions about, and I told her we could meet when I was in Poland. She came today with boxes and bags of specimens, a few of which are shown below.

Erratics collection 061714These are glacial erratics from a moraine in southwestern Poland. They are rocks of a variety of types and ages scraped up by glaciers in the north and deposited in the south. Alina is sorting through what fossils are in them. It is a fun collection because it contains rocks from the Cambrian to the Cenozoic, with all manner of trace and body fossils. They can be quite a challenge to identify because the stratigraphic context is gone.

Half my day was spent writing, so I have nothing else to report. Tomorrow, though, is going to contain a field trip to the Góra Świętej Anny Mountain. (I hope everyone is noticing how hard I work at getting the Polish letters correct!)

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