Wooster’s Fossil of the Week: A bivalve boring from the Upper Ordovician of southern Ohio

December 16th, 2012

This week’s fossil is from close to home. In fact, it sit in my office. The above is a trace fossil named Petroxestes pera. It was produced on a carbonate hardground by a mytilacean bivalve known as Modiolopsis (shown below). Apparently the clam rocked back and forth on this substrate to make a small trench to hold it in place for its filter-feeding. This particular specimen of Petroxestes was found in the Liberty Formation (Upper Ordovician) of Caesar Creek State Park in southern Ohio. This is a place many Wooster paleontology students know well from field trips.
The original Petroxestes was at first known only from the Cincinnatian Group, but now it is known from many other places and time intervals, even including the Cretaceous and Miocene. It is a good lesson about trace fossils. They are defined by their morphology, not what organisms made them. It turns out that this slot-shaped trace can be made by other animals besides Modiolopsis, which went extinct in the Permian.

References:

Jagt, J.W.M., Neumann, C. and Donovan, S.K. 2009. Petroxestes altera, a new bioerosional trace fossil from the upper Maastrichtian (Cretaceous) of northeast Belgium. Bulletin de l’Institut royal des Sciences naturelles de Belgique, Sciences de la Terre 79: 137-145.

Pickerill, R.K., Donovan, S.K. and Portell, R.W. 2001. The bioerosional ichnofossil Petroxestes pera Wilson and Palmer from the Middle Miocene of Carriacou, Lesser Antilles. Caribbean Journal of Science 37: 130-131.

Pojeta Jr., J. and Palmer, T.J. 1976. The origin of rock boring in mytilacean pelecypods. Alcheringa 1: 167-179.

Tapanila, L. and Copper, P. 2002. Endolithic trace fossils in Ordovician-Silurian corals and stromatoporoids, Anticosti Island, eastern Canada. Acta Geologica Hispanica 37: 15–20.

Wilson, M.A. and Palmer, T.J. 1988. Nomenclature of a bivalve boring from the Upper Ordovician of the midwestern United States. Journal of Paleontology 62: 306-308.

Wilson, M.A. and Palmer, T.J. 2006. Patterns and processes in the Ordovician Bioerosion Revolution. Ichnos 13: 109–112.

Wooster’s Fossil of the Week: A horn coral from the Upper Ordovician of Indiana

December 9th, 2012

This week’s fossil is a very common one from the Whitewater Formation (Richmondian, Upper Ordovician) exposed near Richmond, Indiana. It was collected, along with hundreds of other specimens, during one of many Invertebrate Paleontology field trips to an outcrop along a highway. The fossil is Grewingkia canadensis (Billings, 1862), a species my students know well because many made acetate peels of cross-sections they cut through it.

Grewingkia canadensis belongs to the Order Rugosa, a group commonly called the “horn corals” because their solitary forms (as above) have a horn-like shape. Children often think they are dinosaur teeth! It is so common in Richmondian rocks that it is sometimes used to indicate current direction. Its robust skeleton provided attachment space to many encrusting organisms, and it often has multiple borings in its thick calcite theca.

We believe that the rugose corals lived much like corals today. They sat partially buried in the sediment with the wide end of the skeleton facing upwards. A polyp sat inside the cup-shaped opening, spreading its tentacles to catch small organisms swimming by.

Grewingkia canadensis has a complicated taxonomic history. It is likely also known as Streptelasma rusticum, Grewingkia rustica, Streptelasma vagans, Streptelasma insolitum, and Streptelasma dispandum. G. canadensis is characterized by cardinal and counter septa (the vertical partitions inside the coral skeleton) that are longer than the other major septa throughout ontogeny (growth).
The handsome man shown above is, of course, a paleontologist. This is Elkanah Billings (1820-1876), Canada’s first government paleontologist and the one who named Grewingkia canadensis. (He originally placed it in the genus Zaphrentis.) Billings was born on a farm near Ottawa. He went to law school and became a lawyer in 1845. But he loved fossils and in 1852 founded a journal called the Canadian Naturalist (and Geologist). In 1856, Billings left the law and joined the Geological Survey of Canada as its first paleontologist. He named over a thousand new species in his career, and is best known for describing the first fossil from the Ediacaran biota — a critical time in life’s early history. The Billings Medal is given annually by the Geological Association of Canada to the most outstanding of its paleontologists.

References:

Billings, E. 1862. New species of fossils from different parts of the Lower, Middle, and Upper Silurian rocks of Canada. Paleozoic Fossils, Volume 1, Canadian Geological Survey, p. 96-168.

Elias, R.J. and Lee, D.J. 1993. Microborings and growth in Late Ordovician halysitids and other corals. Journal of Paleontology 67: 922-934.

Elias, R.J., McAuley, R.J. and Mattison, B.W. 1987. Directional orientations of solitary rugose corals. Canadian Journal of Earth Sciences 24: 806-812.

Wooster’s Fossil of the Week: A gumdrop bryozoan (Middle Ordovician of eastern Iowa)

November 25th, 2012

This simple, rounded fossil with tiny holes on its surface is the trepostome bryozoan Prasopora falesi (James, 1884) from the Middle Ordovician Galena Group of eastern Iowa. It was collected with dozens of others on an Independent Study field trip in 2003 with Aaron House (2004). Aaron was studying the paleoecology of these bryozoans; he was especially interested in borings in these calcitic bryozoans called Trypanites.

Part of Aaron’s project involved cutting through these Prasopora colonies to see the borings on the inside. He made acetate peels of polished slabs of the bryozoans, a technique that produces a detailed acetate replica of internal details.
The image above is of one of those acetate peels. You can see the tubular zooecia that contained the original zooids (or individuals) of the bryozoan colony. (They are a series of ellipses because of the angle of the cut and variations in zooecial growth directions.) The black dots are very curious: they are apparently brown bodies, the fossilized remains of the tiny polypides inside the zooecia. These organic remains were replaced by dark minerals and preserved all these 470 million years since.

References:

Anstey, R.L. and Perry, T.G. 1972. Eden Shale bryozoans: a numerical study (Ordovician, Ohio Valley). Michigan State University Publications of the Museum, Paleontological Series, Vol. 1, 80 p.

James, U.P. 1884. Descriptions of four new species of fossils from the Cincinnati Group. The Journal of the Cincinnati Society of Natural History 7: 137-140.

Morrison, S.J. and Anstey, R.L. 1979. Ultrastructure and composition of brown bodies in some Ordovician trepostome bryozoans. Journal of Paleontology 53: 943-949.

Nicholson, H.A. and Etheridge, R., Jr. 1877. On Prasopora Grayae, a new genus and species of Silurian corals. Annals and Magazine of Natural History 4:388–392.

The first Wooster Geology student posters at GSA 2012

November 4th, 2012

CHARLOTTE, NORTH CAROLINA–The brave souls Jonah Novek (’13) above and Kit Price (’13) below were the first Wooster students to present their posters at the 2012 Geological Society of America meeting. Jonah worked in Estonia this past summer on Early Silurian recovery faunas in the Hilliste Formation on Hiiumaa Island. You can read his abstract directly here, and you can recall his field adventures by searching for “Jonah” in this blog. Kit collected Upper Ordovician cryptic sclerobiont fossils in Indiana in the late summer. Her abstract is here, and you can see her work in this blog by searching for “Kit“. Jonah and Kit started off our GSA presentation experience with confidence and joy.

Wooster’s Fossil of the Week: a deformed brachiopod (Upper Ordovician of Indiana)

September 23rd, 2012

Kevin Silver (’13), a sharp-eyed paleontology student, found this odd brachiopod on our field trip earlier this month in southeastern Indiana. It comes from the Upper Ordovician (Katian) Whitewater Formation. Kevin correctly identified it as Vinlandostrophia acutilirata (Conrad, 1842), an orthid brachiopod formerly in the genus Platystrophia (see Zuykov and Harper, 2007). The above view is looking at the anterior of the brachiopod with the dorsal valve above and the ventral valve below.

What we see right away is that this brachiopod specimen is asymmetric: the right side is much shorter than the left. This is a feature of this individual, not the species. Is it a teratology — a deformity of growth? Probably. It is unlikely to be from post-depositional squeezing because the shell is otherwise in excellent shape. The oddity did not seem to hinder this individual from growing to a full adult size.

The same specimen looking at the dorsal valve with the hinge at the top of the image. The fold in the center is coming up towards us.

The posterior of our specimen, with the dorsal valve at the top. This is the hinge of the brachiopod.

A view of the ventral valve with the sulcus in the center.

(The above images are to help my paleontology students with their brachiopod morphology!)

References:

Alberstadt, L.P. 1979. The brachiopod genus Platystrophia. United States Geological Survey Professional Paper 1066-B: 1-20.

Boucot A.J. and Sun, Y.L. 1998. Teratology, possible pathologic conditions in fossil articulate brachiopods: p. 506-513, Collected works of the international symposium on Geological Sciences, Peking.

Conrad, T.A. 1842. Observations on the Silurian and Devonian Systems of the United States, with descriptions of new organic remains. Journal of the Academy of Natural Sciences of Philadelphia 8: 228-280.

Zuykov, M.A. and Harper, D.A.T. 2007. Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera. Estonian Journal of Earth Sciences 56: 11-34.

Wooster’s Fossils of the Week: a little sclerobiont community (Upper Ordovician of Indiana)

September 16th, 2012

Last week the students of my Invertebrate Paleontology class found many excellent fossils in the Whitewater and Liberty Formations of southeastern Indiana. We will be featuring some of them in this space. I want to start with one of my own finds: an orthid brachiopod from the Whitewater known as Vinlandostrophia acutilirata (Conrad, 1842), the inside of which is encrusted by old friends Cuffeyella arachnoidea (Hall, 1847) and Cornulites flexuosus (Hall 1847).

A sclerobiont is an organism living in or on a hard substrate. The branching form in the image is Cuffeyella arachnoidea, an encrusting cyclostome bryozoan well represented in the Cincinnatian Group (Taylor and Wilson, 1996). The conical encrusters are the lophophorate Cornulites flexuosus, a species we covered earlier in detail.

These sclerobionts were well protected from weathering on the outcrop by the concavity of the brachiopod’s interior, giving us a beautiful vignette of an ancient ecosystem.

References:

Conrad, T.A. 1842. Observations on the Silurian and Devonian Systems of the United States, with descriptions of new organic remains. Journal of the Academy of Natural Sciences of Philadelphia 8: 228-280.

Hall, J. 1847. Paleontology of New York, v. 1: Albany, State of New York, 338 p.

Taylor, P.D. and Wilson, M.A. 1996. Cuffeyella, a new bryozoan genus from the Late Ordovician of North America, and its bearing on the origin of the post-Paleozoic cyclostomates, p. 351-360. In: Gordon, D.P., A.M. Smith and J.A. Grant-Mackie (eds.), Bryozoans in Space and Time. Proceedings of the 10th International Bryozoology Conference, Wellington, New Zealand, 1995. National Institute of Water & Atmospheric Research Ltd, Wellington, 442 pages.

Paleontology field trip in southeastern Indiana

September 9th, 2012

RICHMOND, INDIANA–Geology students in the Cincinnati area are a bit spoiled when it comes to finding fossils in the field. The Upper Ordovician rocks here are world-famous for the extraordinary abundance, variety and preservation of invertebrate fossils.like those shown above and below.

Today Wooster’s Invertebrate Paleontology class had its annual field trip to collect specimens for lab projects and analyses. We traveled to roadcut outcrops south of Richmond, Indiana — places Wooster Geologists have been visiting for about 30 years. Most recently Kit Price (’13) and her team was here collecting specimens for her Independent Study project. She was on this trip as well, and the class found lots of goodies for her work.

Our fleet of vehicles at our first outcrop (the Whitewater Formation).

Matt Peppers (’13) and Will Cary (’13) striking a Team Utah pose with the Whitewater Formation. Note that this rock unit is mostly resistant limestone beds.

The outcrop of the Liberty Formation at our second stop. (The Liberty is known as the Dillsboro Formation in Indiana, but we tend to use the Ohio names just across the border.) Note the prominence of less resistant shale.

It was a great day — sunny, warm and full of fossils. This class was especially adept at finding unusual specimens, several of which will show up us Fossils of the Week!

Upside-down and inside-out: Cryptic skeletobiont communities from the Late Ordovician of Ohio, Indiana, and Kentucky — An abstract submitted to the Geological Society of America for the 2012 annual meeting

August 14th, 2012

Editor’s note: The Wooster Geologists in Indiana this summer wrote an abstract for the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Kit Price in the format required for GSA abstracts:

Upside-down and inside-out: Cryptic skeletobiont communities from the Late Ordovician of Ohio, Indiana, and Kentucky

PRICE, Katherine W. and WILSON, Mark A., Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691

In the majority of the studies in which skeletobiont communities are described, they are found on the exteriors of shell substrates. Skeletobiont communities that inhabited cryptic environments inside some of these same organisms are poorly known. In those instances where cryptic skeletobiont communities have been described, they are on a much larger scale (i.e., cavities in bryozoan reefs and under hardground ledges) and do not include smaller cryptic communities. The Cincinnatian Series of Ohio, Indiana, and Kentucky has many examples of these cryptic communities. Skeletobionts encrusted the interiors of gastropod, monoplacophoran, and nautiloid shells post-mortem, and are mostly made up of sheet and runner-type bryozoans and cornulitids, along with some craniid brachiopods and microconchids. Interestingly, in contrast to other studies on skeletobionts, the majority of the encrusters in our study do not appear to have been concerned with the location of the host aperture. Only the runner-type bryozoans (Cuffeyella and Corynotrypa) appear to have some directional preference, generally increasing their crypticity and branching away from the aperture. However, increasing crypticity is not always the case; sometimes the bryozoans branch parallel to the aperture or even grew towards it. Aside from shedding light on the life habits of these encrusters, these cryptic skeletobionts also inadvertently preserved their hosts through bioimmuration. Bioimmuration is a type of fossil preservation in which a skeletal organism overgrows another, preserving its negative relief. These cryptic communities not only tell us more about the organisms living in these isolated cavities, but they also have preserved detailed external and internal molds of their host aragonitic fauna. This provides information about shell morphology that would have otherwise been lost to dissolution. Because of the abundance of skeletal bioimmuration in the Cincinnatian, a comparison of cryptic to exposed skeletobionts living in the same environments can be made.

____________________________________________________________

The header photograph is of an internal mold of a monoplacophoran mollusk. At the left you can see the branching runners of the bryozoan Cuffeyella, shown in closer view below.

Above is a close-up of the monoplacophoran internal mold. This bryozoan (Cuffeyella) was growing on the inside of the monoplacophoran shell. That shell filled with sediment and then dissolved, leaving the cemented sediment and the underside of the encrusting bryozoan. (Thus the “upside-down and inside-out” preservation.)

This is a view of the underside of skeletobionts that grew inside a nautiloid conch. The conch dissolved, leaving the undersides of various encrusters. A = the inarticulate brachiopod Petrocrania; B = sheet-like bryozoan; C = a rare microconchid with an extended apertural tube; D = another sheet-like bryozoan; E = one of many Trypanites or Palaeosabella borings.

Kit Price (’13) on one of her outcrops in Indiana (C/W-149) on July 28, 2012.

Wooster’s Fossil of the Week: a bifoliate bryozoan (Upper Ordovician of Indiana, USA)

August 12th, 2012

The specimen above is a species within the trepostome bryozoan genus Peronopora Nicholson, 1881. I don’t know which species because that would require me to slice it open and examine its microscopic skeletal details. (A reason why trepostome bryozoans are not especially popular among fossil collectors!) I found it on a recent field trip to the Whitewater Formation (Upper Ordovician, about 450 million years old) in eastern Indiana for Kit Price’s Independent Study project. Below is a photograph of the outcrop taken by Katherine Marenco (’03) — the most dramatic perspective I’ve seen for that simple roadcut!
Peronopora is bifoliate, meaning that it grew erect and budded on two sides from a central plane. Its skeleton was made of thick calcite, so it was resistant on the Ordovician seafloor during life and after death. As you can see in the close-up image below, the surface of this bryozoan is complex. It had other thin bryozoans growing on it (mainly Cuffeyella), and it was bored by worm-like organisms before and after death.

The genus Peronopora is one of the best studied trepostome bryozoans because of its thick, well preserved skeleton and abundance from the Middle through the Upper Ordovician. (Our specimen is in the Richmondian Stage and so is one of the last of its kind.) Paleontologists listed below in the references have examined in detail the colony growth (astogeny), paleoenvironments, biogeography and stratigraphic occurrences of Peronopora, making it a model for the order. My colleague Tim Palmer and I collected the genus to find beautiful examples of the bioclaustration Catellocaula vallata.

Peronopora was described in 1881 by Henry Alleyne Nicholson (1844-1899), an English paleontologist we’ve seen previously in this blog. The genus has a complicated early taxonomic history, having at one point been considered a kind of sponge.

References:

Anstey, R.L. and Pachut, J.F. 2004. Cladistic and phenetic recognition of species in the Ordovician bryozoan genus Peronopora. Journal of Paleontology 78: 651-674.

Boardman, R.S. and Utgaard, J. 1966. A revision of the Ordovician bryozoan genera Monticulipora, Peronopora, Heterotrypa, and Dekayia. Journal of Paleontology 40: 1082-1108.

Hickey, D.R. 1988. Bryozoan astogeny and evolutionary novelties: Their role in the origin and systematics of the Ordovician monticuliporid trepostome genus Peronopora. Journal of Paleontology 62: 180-203.

Nicholson, H.A. 1881. On the structure and affinities of the genus Monticulipora and its subgenera. William Blackwood and Sons, Edinburgh, 235 p.

Pachut, J.F. and Anstey, R.L. 2009. Inferring evolutionary modes in a fossil lineage (Bryozoa: Peronopora) from the Middle and Late Ordovician. Paleobiology 35: 209-230.

Wooster Geologists in Indiana!

July 28th, 2012

WOOSTER, OHIO–I’ve seen a lot of fossils in my blessedly long time as a paleontologist, and I’ve had the opportunity to study them in many exotic places. I’m often reminded, though, that one of the best preserved and most diverse fossil faunas is in my backyard: the Cincinnati Region. The fossils here from the Upper Ordovician are extraordinary, and they will always be a resource for paleontological research. They’re just plain fun to find, too. There is a reason why so many American paleontologists have educational roots in the Ohio, Kentucky and Indiana area.

Sure, the setting is not always glorious. Instead of castles in the distance, we are often working in roadside ditches, but the fossils are so fascinating that we forget the prosaic American recreational weekend traffic zooming by to local parks, lakes and rivers. In the above image you see Katherine Marenco (’03), Richa Ekka (’13) and Kit Price (’13) today on our first outcrop of the in eastern Indiana just south of Richmond (C/W-148 in our locality system). It is an outcrop of the Whitewater Formation (Richmondian, Upper Ordovician) known by many Wooster geologists from paleontology course field trips to Indiana. It is chock-jammy-full of fossils, as you can see from the random shot below:

We are here today to collect material for Kit Price’s Junior (and then Senior) Independent Study project. She will be studying bioimmuration processes in these rocks. We will have more on her study after we unpack and clean the treasures we collected today.

Accompanying us on this field trip is Dr. Katherine Nicholson Marenco (Wooster ’03), shown above. She is visiting to Wooster to renew work on Jurassic bioimmuration and aragonite dissolution in the Portlandian of southern England, the topic of her Senior Independent Study in 2002-2003. She went on to graduate school and a post-doc position and is now at Bryn Mawr in Pennsylvania. We are very fortunate to have her with us because of her expertise on the topic of “upside-down encrusters” and her many creative ideas. We look forward to much collaboration! (You can see her in this old page on Paleontology at Wooster.)

Richa Ekka (above) generously volunteered to help us find and collect fossils. You may remember Richa from her very recent work in Estonia. (It is difficult to believe that just two weeks ago we were on islands in the Baltic.) Richa, as always, found great specimens.

Here is Kit working on our last Cincinnatian outcrop near Brookville, Indiana (C/W-111). Note the very dry grass, a result of the continuing drought in this part of the state. The temperatures today, by the way, were in the pleasant high 60s and low 70s.

Finally, we just had to share a photograph of our rented field vehicle: a Dodge Avenger. We think this is the trendiest car color of 2012: burnt pumpkin.

More in later posts on what we found on this field trip, and Kit’s developing Independent Study project. It was a spectacular field day with excellent fossils and great conversations.

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