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.

References:

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 Fossil of the Week: Thoroughly encrusted brachiopod from the Upper Ordovician of Indiana

March 30th, 2014

1 Rafinesquina ponderosa (Hall) ventralLast week was an intensely bored Upper Ordovician bryozoan, so it seems only fair to have a thoroughly encrusted Upper Ordovician brachiopod next. The above is, although you would hardly know it, the ventral valve exterior of a common strophomenid Rafinesquina ponderosa from the Whitewater Formation exposed just south of Richmond, Indiana (locality C/W-148). I collected it earlier this month on a trip with Coleman Fitch (’15).
2 Rafinesquina ponderosa (Hall) dorsalThis is the other side of the specimen. We are looking at the dorsal valve exterior. Enough of the brachiopod shows through the encrusters that we can identify it. Note that both valves are in place, so we say this brachiopod is articulated. Usually after death brachiopod valves become disarticulated, so the articulation here may indicate that the organism had been quickly buried. This brachiopod is concavo-convex, meaning that the exterior of the dorsal valve is concave and the exterior of the ventral valve is convex.
3 Protaraea 032314Returning to the ventral valve, this is a close-up of the encruster that takes up its entire exterior surface. It is the colonial heliolitid coral Protaraea richmondensis Foerste, 1909. (Note the species name and that it was collected just outside Richmond, Indiana.) This thin coral is a common encruster in the Upper Ordovician. Usually it is a smaller patch on a shell. This is the most developed I’ve seen the species. The holes, called corallites, held the individual polyps.
4 Bryo on Protaraea 032314The encrusting coral has an encruster on top of it. This is a trepostome bryozoan, which you can identify by the tiny little holes (zooecia) that held the individuals (zooids). The patch of coral it is occupying must have been dead when the bryozoan larva landed and began to bud.
5 Trepostome 032314Now we’re returning to the concave dorsal valve with its very different set of encrusters. This is a close-up of another kind of trepostome bryozoan, this one with protruding bumps called monticules. They may have functioned as “exhalant current chimneys”, meaning that they may have helped channel feeding currents away from the surface after they passed through the tentacular lophophores of the bryozoan zooids. For our purposes, this is a feature that distinguishes this bryozoan species from the one on the ventral valve.
6 Cuffeyella 032314There is a third, very different bryozoan on the dorsal valve. This blobby, ramifying form is a well-developed specimen of Cuffeyella arachnoidea (Hall, 1847). It is again a common encruster in the Upper Ordovician, but not usually so thick.
7 Cuffeyella on hinge 032314If we look closely at the hinge of the brachiopod on the dorsal side, we can see a much smaller C. arachnoidea spreading on the ventral valve.
8 Encrusted edge 032314Finally, this is a side view of the brachiopod with the ventral valve above and the dorsal valve below. We’re looking at the junction of the articulated valves, the commissure. For the entire extent of the commissure, the encrusting coral grows to the edge of the ventral valve and no further. This is a strong indication that the brachiopod was alive when the coral was growing on it. The brachiopod needed to keep that margin clear for its own feeding.

The paleoecological implications here are that the coral was alive at the same time as the brachiopod. This means that the convex exterior surface of the ventral valve was upwards for the living brachiopod. The concave exterior surface of the dorsal valve faced downwards. The coral and bryozoan encrusting the top of the living brachiopod were exposed to the open sea; the bryozoans encrusting the undersurface of the living brachiopod were encrusting a cryptic space. We are thus likely seeing the living relationships between the encrusters and the brachiopod — this encrustation took place during the life of the brachiopod.

Further, this demonstrates that this concavo-convex strophomenid brachiopod was living with the convex side up. This has been a controversy for decades in the rarefied world of brachiopod paleoecology. This tiny bit of evidence, combined with some thorough recent studies (see Dattilo et al., 2009; Plotnick et al., 2013), strengthens the case for a convex-up orientation. Back when I was a student these would be fighting words!

References:

Alexander, R.R. and Scharpf, C.D. 1990. Epizoans on Late Ordovician brachiopods from southeastern Indiana. Historical Biology 4: 179-202.

Dattilo, B.F., Meyer, D.L., Dewing, K. and Gaynor, M.R. 2009. Escape traces associated with Rafinesquina alternata, an Upper Ordovician strophomenid brachiopod from the Cincinnati Arch Region. Palaios 24: 578-590.

Foerste, A.F. 1909. Preliminary notes on Cincinnatian fossils. Denison University, Scientific Laboratories, Bulletin 14: 208-231.

Mõtus, M.-A. and Zaika, Y. 2012. The oldest heliolitids from the early Katian of the East Baltic region. GFF 134: 225-234.

Ospanova, N.K. 2010. Remarks on the classification system of the Heliolitida. Palaeoworld 19: 268–277.

Plotnick, R.E., Dattilo, B.F., Piquard, D., Bauer, J. and Corrie, J. 2013. The orientation of strophomenid brachiopods on soft substrates. Journal of Paleontology 87: 818-825.

Wooster’s Fossil of the Week: Bryozoan bored and bryozoan boring in the Upper Ordovician of Indiana

March 16th, 2014

Bored Bryo on Brach top 585This week and next we will highlight fossils collected during our brief and successful expedition to the Upper Ordovician (Cincinnatian) of Indiana (with Coleman Fitch ’15) and Kentucky (with William Harrison ’15). We found what we needed to pursue some very specific topics.

Above is a trepostome bryozoan collected from the Liberty Formation (we should be calling it the Dillsboro Formation in Indiana; our locality C/W-149) on IN-101 in southeastern Indiana (N 39.48134°, W84.94843°). You can see the regular network of tiny little holes representing the zooecia (zooid-bearing tubes) of the calcitic zoarium (colony) of the bryozoan. The larger, irregular holes (still pretty small!) are borings cut by worm-like organisms into the bryozoan skeleton shortly after the death of the colony.
Bored Bryo on Brach bottom 585Flipping the specimen over we see the most interesting parts. On the left is a remnant of the original calcitic strophomenid brachiopod shell that was encrusted by the trepostome bryozoan. On the right the shell has broken away, exposing the encrusting surface of the trepostome. We are thus looking here at the inside of a brachiopod valve and the underside of the bryozoan that encrusted it.

This is just what we hoped to find for Coleman’s project on interpreting half-borings in brachiopod shell exteriors. This specimen demonstrates two crucial events after encrustation: First, the borings in the bryozoan extended down to the brachiopod shell and turned sideways to mine along the shell/bryozoan junction (note half-borings in the bryozoan base on the right), and second, the bryozoan broke mostly free of the brachiopod shell, with only a bit remaining on the left. Somewhere there is or was a fragment of that brachiopod with an exterior showing half-borings and no bryozoan encrustation. Thus a brachiopod without bryozoan encrusters may have actually been encrusted at some point, but the bryozoans were later detached. We’ve added a bit to the uncertainty of the encrusting fossil record — even calcitic skeletal evidence on this small scale can go missing. We’ve also started on a good story about the behavior of the tiny critters that bored into this shelly complex.
Ctenostome closer 031314_585A bonus in this specimen can be seen in this closer view of that brachiopod shell interior above. That branching network is a complex ctenostome bryozoan boring called Ropalonaria. This is a particularly well developed specimen with thicker, shorter zooids than I’ve seen before. This kind of boring is the subject of a previous Fossil of the Week entry.

Coleman has a great start on his Independent Study project with specimens like these. He has a lot of sectioning and adequate peeling ahead of him!

References:

Brett, C.E., Smrecak, T., Parsons-Hubbard, K. and Walker, S. 2012. Marine sclerobiofacies: Encrusting and endolithic communities on shells through time and space. In: Talent, J.A. (ed.) Earth and Life, International Year of Planet Earth, p. 129-157. Springer.

Pohowsky, R.A. 1978. The boring ctenostomate Bryozoa: taxonomy and paleobiology based on cavities in calcareous substrata. Bulletins of American Paleontology 73(301): 192 p.

Smrecak, T.A. and Brett, C.E. 2008. Discerning patterns in epibiont distribution across a Late Ordovician (Cincinnatian) depth gradient. Geological Society of America Abstracts with Programs 40:18.

Wilson, M.A., Dennison-Budak, C.W. and Bowen, J.C. 2006. Half-borings and missing encrusters on brachiopods in the Upper Ordovician: Implications for the paleoecological analysis of sclerobionts. Geological Society of America Abstracts with Programs 38:514.

Ordovician bioerosion and encrustation project begins

March 9th, 2014

Coleman 030914RICHMOND, INDIANA–Meet Coleman Fitch (’15) standing on the iconic outcrop of the Whitewater Formation (Upper Ordovician) on Route 27 about a mile south of Richmond (C/W-148; N 39.78722°, W 84.90166° — which has a nice Google Maps street view). This was his first day of fieldwork for his study of the complex relationship between borings and encrusters on brachiopods and mollusks. Note that Coleman has manfully taken off one glove for fossil collection. Despite the sun, we were freezing for science. Later in the day we collected from a warmer exposure of the Liberty Formation (Locality C/W-149) on IN-101 (N 39.48134°, W84.94843°).

Our collecting was very successful today. We found numerous examples of “half-borings” on trepostome bryozoan attachment surfaces, and many other curious fossils showing an interplay of early diagenesis (especially aragonite dissolution and calcite precipitation) and biotic processes.

Richmond specimen 030914Above is an example of the fun and complex fossils at the Whitewater locality. What processes do you think this specimen represents?

Tomorrow I meet William Harrison (’15) in northern Kentucky to search for bored bryozoans and bioclaustrations. It promises to be much warmer down there!

Wooster paleontologists begin a new field season

March 8th, 2014

Southgate 030814RICHMOND, INDIANA–This is the first day of what upper midwesterners hilariously call “spring break”, so it is time to get some students in the field. I can’t say this is the first Wooster geology fieldwork of the year because that crazy Greg Wiles lab was out on the ice in deepest January. I spent today in eastern Indiana exploring field sites for a new generation of Independent Study students. Tomorrow and Monday Coleman Fitch (’15) and William Harrison (’15) will be joining me to collect specimens for their I.S. projects on Cincinnatian (Upper Ordovician) fossils. We’ll highlight their work in the next couple of days.

Above is one of the best known fossil sites in southeastern Indiana. It is the Southgate Hill section (sometimes called the St. Leon roadcut) at N 39.33899°, W 84.95287°. Exposed here are (from bottom to top) the Oregonia, Waynesville, Liberty, Whitewater and Saluda units of the Cincinnatian Group. It is a rich site — and incredibly muddy today. I suppose I’ll take mud over ice. Note the blue sky. By the end of the day it was as gray as the rocks, making the search for tiny fossil details difficult. Tomorrow promises to be much sunnier. Brach Slab 030814The brachiopods at the Southgate exposure are incredibly abundant and well preserved. These are strophomenids. Crinoids Bryozoans 030814Bryozoans (the twiggy bits) and crinoids (the circular fossils with star-shaped central holes). Can’t go wrong with this combination. More tomorrow and Monday as Coleman and William get to work. Meanwhile I’m wondering how I managed to get a motel room right next to an active railway …

Wooster’s Fossil of the Week: A tubeworm-encrusted parasitic gastropod (Silurian of Indiana)

February 16th, 2014

Platyostoma1_585Last week three Wooster geology students and I visited Ken Karns, an enthusiastic citizen scientist who has developed an extraordinary fossil collection in his home in Lancaster, Ohio. Ken is a man of prodigious energies and skills as he not only is an expert fossil collector and preparator, he also has a world-class curated collection of Ohio beetles! He was introduced to us by our friend Brian Bade, a man with similar enthusiasms and skills. The students were Steph Bosch (’14), Lizzie Reinthal (’14) and Ian Tulungen (’15). Our goals were to meet Ken, see his magnificent collection with Brian and other friends, and then focus on a project for Ian’s future Independent Study work. Success on all counts, and the specimen above is evidence. Ken was very generous in loaning this specimen to us along with several others for Ian’s work.

The above specimen is from the type section of the Waldron Shale Member (Silurian, Wenlockian, Homerian, about 430 million years old) of the Pleasant Mills Formation near St. Paul, south-central Indiana. Ken Karns collected and prepared it. It is a platyceratid snail of the genus Platyostoma Conrad 1842. It is probably of the species P. niagarense Hall 1852, but there is another species in the same unit (P. plebeium Hall 1876). I’m not quite sure of the differences between these species because platyceratids are notoriously variable. It is possible they are synonymous. Unlike most gastropods, platyceratids had calcite shells instead of aragonite, so they are very well preserved. For an excellent taxonomic review of the genus Platyostoma and its founder, Timothy Abbott Conrad, please see Tony Edger’s blog entry. (We’ve talked about Conrad in this blog as well.)
Platyostoma2_585In this different angle on the specimen you can see additional encrusters (sclerobionts) on the surface of the Platyostoma shell. In the lower right is a remnant of a sheet-like bryozoan, but the most prominent sclerobionts are the tubeworms Cornulites proprius Hall 1876. These encrusters interest us very much.
Cornulitids on Platyostoma_585In this closer view it is apparent that several of the cornulitids are aligned with their apertures pointing in the same way. This is a pattern we’ve seen on many of these snails. Platyostoma was a parasitic snail that lived attached to crinoids, which were abundant in the Waldron fauna. They lived high on the calyx of the crinoid firmly fixed to its skeleton. These cornulitids and other encrusters were thus living high off the substrate perched on the snails. They were filter-feeders like the crinoids, so they may have been feeding on some suspended food fraction missed by the crinoid arms, or they were competing for nutrients and added to the parasitic load on the poor crinoids. The cornulitids were further living on a living snail shell, from what we can tell, so they grew with a substrate slowly growing underneath them. This produces all sorts of delicious paleoecological questions to sort out!
Platyostoma long cornulitid_585Check out the size of this specimen of Cornulites proprius attached to another Platyostoma niagarense. Clearly these tubeworms could do very well under these conditions! This is the largest cornulitid I’ve seen.

Ken_Karns_preparatory_labHere is Ken Karns in his fossil preparation laboratory, which he assembled himself. The box with the armholes is for air-abrading specimens to remove matrix.

Display cases KenThis is one section of the display cases Ken has in his basement museum. Most of the specimens shown here are from the Waldron Shale.

Platyostoma collection displayedA closer view of a display of Platyostoma from the Waldron Shale. Note the many encrusters.

Lizzie Brian KenLizzie Reinthal, Brian Bade and Ken talk about fossil preparation with some Waldron material. The cases are full of curated specimens.

Encrusted crinoid rootsThere are so many treasures in Ken’s collections. I am fascinated by this little slab showing the holdfast of a crinoid with sheet-like bryozoans encrusting it. The bryozoans show that the roots were at least partially exposed at some point.

Thank you again to Brian Bade for arranging this trip, and Ken Karns for being such a fantastic host. We are looking forward to many Waldron projects in the future!

References:

Baumiller, T.K. 2003. Evaluating the interaction between platyceratid gastropods and crinoids: a cost–benefit approach. Palaeogeography, Palaeoclimatology, Palaeoecology 201: 199-209.

Baumiller, T.K. and Gahn, F.J. 2002. Fossil record of parasitism on marine invertebrates with special emphasis on the platyceratid-crinoid interaction. Paleontological Society Papers 8: 195-210.

Brett, C.E., Cramer, B.D., McLaughlin, P.I., Kleffner, M.A., Showers, W.J. and Thomka, J.R. 2012. Revised Telychian–Sheinwoodian (Silurian) stratigraphy of the Laurentian mid-continent: building uniform nomenclature along the Cincinnati Arch. Bulletin of Geosciences 87: 733–753.

Feldman, H.R. 1989. Taphonomic processes in the Waldron Shale, Silurian, southern Indiana. Palaios 4: 144-156.

Gahn, F.J. and Baumiller, T.K. 2006. Using platyceratid gastropod behaviour to test functional morphology. Historical Biology 18: 397-404.

Gahn, F.J., Fabian, A. and Baumiller, T.K. 2003. Additional evidence for the drilling behavior of Paleozoic gastropods. Acta Palaeontologica Polonica 48: 156-156.

Hall, J. 1881. Descriptions of the Species of Fossils Found in the Niagara Group at Waldron, Indiana. In: Indiana Department of Geology and Natural Resources, Eleventh Annual Report, p. 217-345. [PDF of the text downloadable here.]

Liddell, W.D. and Brett, C.E. (1982). Skeletal overgrowths among epizoans from the Silurian (Wenlockian) Waldron Shale. Paleobiology 8: 67-78.

Peters, S.E. and Bork, K.B. 1998. Secondary tiering on crinoids from the Waldron Shale (Silurian: Wenlockian) of Indiana. Journal of Paleontology 72: 887-894.

Sutton, M.D., Briggs, D.E.G., Siveter, D.J. and Siveter, D.J. 2006. Fossilized soft tissues in a Silurian platyceratid gastropod. Proceedings of the Royal Society B: Biological Science 273(1590): 1039-1044.

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

Wooster’s Fossils of the Week: Bioclaustration-boring structures in bryozoans from the Upper Ordovician of the Cincinnati region

February 9th, 2014

Chimneys 149aAnother bioerosion mystery from those fascinating Upper Ordovician rocks around Cincinnati. Above you see a flat, bifoliate trepostome bryozoan (probably Peronopora) with pock holes scattered across its surface. At first you may think, after reading so many blog posts here, that these are again the simple cylindrical boring Trypanites, but then you note that they are shallow and have raised rims so that they look like little meteorite craters. These holes thus represent tiny organisms on the bryozoan surface while it was alive. The bryozoan grew around these infesters, producing the reaction tissue of the rims. This is a kind of preservation called bioclaustration (literally, “walled-in life” from the same root in claustrophobia and cloisters). The specimen is from locality C/W-149 (Liberty Formation near Brookville, Franklin County, Indiana; 39º 28.847′ N, 84º 56.941′ W).
Chimneys 153aThis is another trepostome bryozoan with these rimmed pits. It is from locality C/W-153 (Bull Fork Formation near Maysville, Mason County, Kentucky; 38º 35.111′ N, 083º 42.094′ W). The pits are more numerous and have more pronounced reaction rims.
Chimneys 153bA closer view. One of the interesting questions is whether these pits are also borings. Did they cut down into the bryozoan skeleton at the same time it was growing up around them? We should be able to answer that by making a cross-section through the pits to see what their bases look like. The bryozoan walls should be either cut or entire.
Chimneys 153cThis is an older image I made back in the days of film to show the density of the rimmed pits in the same bryozoan as above. If we assume that the pit-maker was a filter-feeding organism, how did it affect the nutrient intake of the host bryozoan? Maybe the infester had a larger feeding apparatus and took a larger size fraction of the suspended food? (This could be a project where we apply aerosol filtration theory.)  Maybe the bryozoan suffered from a cut in its usual supply of food and had a stunted colony as a result? These are questions my students and I plan to pursue this summer and next year.

It is good to get back to the glorious Cincinnatian!

References:

Ernst, A., Taylor, P.D. and Bohatý, J. 2014. A new Middle Devonian cystoporate bryozoan from Germany containing a
new symbiont bioclaustration. Acta Palaeontologica Polonica 59: 173–183.

Kammer, T.W. 1985. Aerosol filtration theory applied to Mississippian deltaic crinoids. Journal of Paleontology 59: 551-560.

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

Rubinstein, D.I. and Koehl, M.A.R. 1977. The mechanisms of filter feeding: some theoretical considerations. American Naturalist 111: 981-994.

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

Taylor, P.D. and Voigt, E. 2006. Symbiont bioclaustrations in Cretaceous cyclostome bryozoans. Courier Forschungsinstitut Senckenberg 257: 131-136.

Wooster’s Fossil of the Week: Tubular drillholes (Upper Ordovician of the Cincinnati Region)

April 28th, 2013

Trypanites_hardground_585_010213

This is one of the simplest fossils ever: a cylindrical hole drilled into a hard substrate like a skeleton or rock. The above image is of a hardground (cemented carbonate seafloor) from the Upper Ordovician of northern Kentucky with these borings cut perpendicularly to the bedding and descending downwards. Each boring is filled with light-colored dolomite crystals. This boring type is given the trace fossil name Trypanites weisi Magdefrau 1932.
Trypanites_Bryozoan_010213_585Trypanites, shown above cutting into a trepostome bryozoan from the Upper Ordovician of southeastern Indiana, is a very long-ranging trace fossil. It first appears in the Lower Cambrian and it is still formed today — a range of 540 million years (James et al., 1977; Taylor and Wilson, 2003). It was (and is) made by a variety of worm-like organisms, almost always in carbonate substrates. Today the most common producers of Trypanites are some polychaete and sipunculid worms. Trypanites was the most common boring until the Jurassic, when it was overtaken in abundance by bivalve and sponge borings. Trypanites was the primary boring in the Ordovician Bioerosion Revolution (Wilson and Palmer, 2006).
Trypanites_Horizontal_585Trypanites is defined as a cylindrical, unbranched boring in a hard substrate (such as a rock or shell) with a length up to 50 times its width (Bromley, 1972). The typical Trypanites is only a few millimeters long, but some are known to be up to 12 centimeters in length (Cole and Palmer, 1999). The above occurrence of Trypanites is one of my favorites. The organisms bored into a bryozoan colony (the fossil in the upper left and center with tiny holes) and down into a bivalve shell the bryozoan had encrusted. The borer then turned 90° and drilled horizontally through the aragonitic and calcitic layers of the shell. The aragonite dissolved, revealing the half-borings of Trypanites.
LibertyBorings_585In this bedding plane view, Trypanites weisi borings are shown cutting into a hardground from the Liberty Formation (Upper Ordovician) of southeastern Indiana. This is a significant occurrence because the borings are cutting through brachiopod shells cemented into the hardground surface. When the brachiopods are dislodged from the hardground, those with holes in them erroneously appear to have been bored by predators (see Wilson and Palmer, 2001).

The simplest of fossils turns out to have its own levels of complexity!

References:

Bromley, R.G. 1972. On some ichnotaxa in hard substrates, with a redefinition of Trypanites Mägdefrau. Paläontologische Zeitschrift 46: 93–98.

Cole, A.R. and Palmer, T.J. 1999. Middle Jurassic worm borings, and a new giant ichnospecies of Trypanites from the Bajocian/Dinantian unconformity, southern England. Proceedings of the Geologists’ Association 110 (3): 203–209.

James, N.P., Kobluk, D.R. and Pemberton, S.G. 1977. The oldest macroborers: Lower Cambrian of Labrador. Science 197 (4307): 980–983.

Taylor, P.D. and Wilson. M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62 (1-2): 1–103.

Wilson, M.A. and Palmer, T.J. 2001. Domiciles, not predatory borings: a simpler explanation of the holes in Ordovician shells analyzed by Kaplan and Baumiller, 2000. Palaios 16: 524-525.

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 bryozoan etching (Upper Ordovician of Indiana)

February 24th, 2013

Ropalonaria_venosa_585_010213Another trace fossil of a sort this week. Above you see the dorsal valve exterior of a strophomenid brachiopod from the Upper Ordovician of southeastern Indiana. Across the surface is a network of grooves looking a bit like a spider web. This is a feature formed when a soft-bodied ctenostome bryozoan colony etched its way down into the shell it was encrusting. Ropalonaria venosa Ulrich, 1879 is the official name of this fossil.
Ropalonaria_close_010513Above is a closer view of the same Ropalonaria venosa. Tiny crystals of yellow dolomite fill the excavations. The ctenostome bryozoan that made it had no skeleton and used some sort of chemical to dissolve the shell beneath it. The fidelity of this etching is good enough to identify various details of the colony structure and zooecial form. This is where our fossil classification system goes a bit awry: Is Ropalonaria a trace fossil (evidence of animal activity) or a kind of external mold of the original organism? Arguments have been made for each category, and the name Ropalonaria shows up on lists of both trace fossils and body fossils.
Ulrich_EO_1927Ropalonaria venosa is the type species of the genus Ropalonaria erected by Edward Oscar Ulrich in 1879 (above in 1927). E.O. Ulrich, as he is better known, was one of the most colorful and controversial geologists of the late 19th and early 20th century. He was born in Covington, Kentucky, in 1857. Covington is across the Ohio River from Cincinnati, Ohio, and is undergirded by the famous fossiliferous limestones and shales of the Cincinnatian Group (Upper Ordovician). Ulrich started as a child collecting fossils in the region. He was an early member of the Cincinnati Society of Natural History, often bringing fossils to meetings for identifications. (There he met another young man very interested in fossils: the future paleontologist Charles Schuchert. Schuchert was the advisor of my advisor’s advisor, so he’s in my “academic genealogy”.)

Ulrich took courses at German Wallace College (today’s Baldwin Wallace University in Berea, Ohio) and the Ohio Medical College. He had an eclectic youth exploring all sorts of topics, from opera to spiritualism, but always kept geology and fossils close to his heart. He had an adventurous stint as a superintendent in a Colorado silver mine. Returning back east, Ulrich became an enormously productive geologist with the geological surveys of Illinois, Minnesota, and Ohio. He was President of the Paleontological Society in 1915. In 1931 he received the Mary Clark Thompson Medal from the National Academy of Sciences, and the next year the Geological Society of America awarded him the prestigious Penrose Medal. He died in 1944 in Washington, D.C.

E.O. Ulrich is still a polarizing figure in American geology. He is famous for resisting the modern concept of facies in sedimentary geology, preferring a concept now known as “layer cake stratigraphy“. (In his defense, the rocks in the Cincinnati area really do fit much of his model; his error was extending it much too far.) Ulrich also has a reputation as a bit of a “splitter” in paleontology. (Someone who makes more species than necessary by “splitting” groups into smaller subgroups.)

Despite what we think of E.O. Ulrich today, his paleontological contributions have mostly held up, including the description of the intriguing fossil Ropalonaria.

References:

Bassler, R.S. 1944. Memorial to Edward Oscar Ulrich. Proceedings of the Geological Society of America for 1944: 331–351.

Pohowsky, R.A. 1978. The boring ctenostomate Bryozoa: taxonomy and paleobiology based on cavities in calcareous substrata. Bulletins of American Paleontology 73(301): 192 p.

Ruedemann, R. 1946. Biographical memoir of Edward Oscar Ulrich, 1857-1944. National Academy of Sciences of the United States of America. Biographical Memoirs, Volume XXIV, 7th Memoir, 24 pp.

Ulrich, E.O. 1879. Descriptions of new genera and species of fossils from the Lower Silurian about Cincinnati: Journal of the Cincinnati Society of Natural History 2: 8-30.

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

February 3rd, 2013

Protaraea111712What we have above is a heliolitid coral known as Protaraea richmondensis Foerste, 1909. It has completely encrusted a gastropod shell with its thin corallum. Stephanie Jarvis, a Wooster student at the time and now a graduate student at Southern Illinois University, found this specimen during her paleontology class field trip to the Whitewater Formation exposed near Richmond, Indiana.

Protaraea is a confusing taxon to my Invertebrate Paleontology students. It is a very common encruster in their Ordovician field collections, being found on hard substrates as varied as rugose corals and orthid brachiopods. It is so thin, though, that it is hard to believe it was a colonial coral. Plus it has tiny septa (vertical partitions) in its corallites (the holes that held the polyps), very unlike most corals of the heliolitid variety. This is a group the students have to identify by matching pictures and taking our word for it.

We can’t identify the gastropod underneath. Note that it has a sinus evident in the last whorl (an open slot parallel to the coiling). The coral grew right up to the edge of this sinus, preserving it and its extension through the shell.

References:

Alexander, R.R. and Scharpf, C.D. 1990. Epizoans on Late Ordovician brachiopods from southeastern Indiana. Historical Biology 4: 179-202.

Foerste, A.F. 1909. Preliminary notes on Cincinnatian fossils. Denison University, Scientific Laboratories, Bulletin 14: 208-231.

Mõtus, M.-A. and Zaika, Y. 2012. The oldest heliolitids from the early Katian of the East Baltic region. GFF 134: 225-234.

Ospanova, N.K. 2010. Remarks on the classification system of the Heliolitida. Palaeoworld 19: 268–277.

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