Wooster’s Fossils of the Week: Bivalve escape trace fossils (Devonian and Cretaceous)

April 7th, 2017

It is time again to dip into the wonderful world of trace fossils. These are tracks, trails, burrows and other evidence of organism behavior. The specimen above is an example. It is Lockeia James, 1879, from the Dakota Formation (Upper Cretaceous). These are traces attributed to infaunal (living within the sediment) bivalves trying to escape deeper burial by storm-deposited sediment. If you look closely, you can see thin horizontal lines made by the clams as they pushed upwards. These structures belong to a behavioral category called Fugichnia (from the Latin fug for “flee”). They are excellent evidence for … you guessed it … ancient storms.
The specimens above are also Lockeia, but from much older rocks (the Chagrin Shale, Upper Devonian of northeastern Ohio). Both slabs show the fossil traces preserved in reverse as sediment that filled the holes rather than the holes themselves. These are the bottoms of the sedimentary beds. We call this preservation, in our most excellent paleontological terminology, convex hyporelief. (Convex for sticking out; hyporelief for being on the underside of the bed.)

The traces we know as Lockeia are sometimes incorrectly referred to as Pelecypodichnus, but Lockeia has ichnotaxonomic priority (it was the earliest name). Maples and West (1989) sort that out for us.
Uriah Pierson James (1811-1889) named Lockeia. He was one of the great amateur Cincinnatian fossil collectors and chroniclers. In 1845, he guided the premier geologist of the time, Charles Lyell, through the Cincinnati hills examining the spectacular Ordovician fossils there. He was the father of Joseph Francis James (1857-1897), one of the early systematic ichnologists.

References:

James, U.P. 1879. The Paleontologist, No. 3. Privately published, Cincinnati, Ohio. p. 17-24.

Maples, C.G. and Ronald R. West, R.R. 1989. Lockeia, not Pelecypodichnus. Journal of Paleontology 63: 694-696.

Radley, J.D., Barker, M.J. and Munt, M.C. 1998. Bivalve trace fossils (Lockeia) from the Barnes High Sandstone (Wealden Group, Lower Cretaceous) of the Wessex Sub-basin, southern England. Cretaceous Research 19: 505-509.

[Originally published January 29, 2012]

Wooster’s Fossils of the Week: A slab of Upper Ordovician bivalves from northern Kentucky

March 31st, 2017

Earlier this month, Luke Kosowatz, Matt Shearer and I went on a field trip through the Cincinnati region collecting Upper Ordovician (Katian) bryozoans and examples of bioerosion for their Independent Study projects and other investigations. I picked up the above slab and put it in our vehicle for future study not because of its beauty, but the preservational modes it displays. The black, rounded objects are bivalves, probably of the Order Modiomorphida. They are miserable fossils to identify because they originally had shells made of the mineral aragonite, which dissolved quickly after the animals died. What is left are a few scrappy molds and that black film. This is a common preservation of bivalves in the Cincinnatian.

This is the Corryville Formation outcrop from which the slab came. It is just west of Maysville, Kentucky, along the AA Highway (N 38.60750°, W 83.76775°; C/W-740).

Here is the slab along the roadside before we cleaned it up. Not much to see, really, except the low-relief black blobs that are remains of bivalves.

As you see, not much detail in the bivalves other than an outline matching somewhat the modiomorphids. Those of you with sharp paleontological eyes will note a round gray patch with radiating lines. This is a bryozoan that was attached to the bivalve shell. When the shell dissolved, the bryozoan attachment surface became visible. In other words, this is an upside-down encrusting bryozoan, a condition we’ve seen several times in this blog.

Here’s another bivalve with an upside-down encrusting bryozoan. This time you can see that the black film was underneath the bryozoan and on the outside of the bivalve shell. In a 2004 paper, Tim Palmer and I wrote: “We have also long been curious about why some of the epifaunal aragonitic Ordovician genera in the Cincinnatian such as Modiolopsis are preserved with a thick black outer shell covering (e.g. Pojeta 1971, pl. 15, fig. 6). It now seems likely that this was a hypertrophied periostracum that conferred some protection against dissolution during life, similar to the situation seen in Recent unionids that are susceptible to dissolution in their fresh-water habitats” (p. 425). Maybe it’s time we followed up on these speculations? I’m sure other paleontologists have had similar ideas.

Among the indistinct modiomorphid bivalves is this old friend: Ambonychia with its characteristic radiating ridges.

References:

Palmer, T.J. and Wilson, M.A. 2004. Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas. Lethaia 37: 417-427.
Pojeta, J. 1971. Review of Ordovician pelecypods. United States Geological Survey, Professional Paper 695, 1-46.

Wooster’s Fossils of the Week: Strophomenid brachiopods from the Upper Ordovician of southern Ohio

March 24th, 2017

Usually I find fossils in the field or lab and then craft a Fossil of the Week entry around them. This time, though, I started with a paper and then searched for fossils to illustrate it. I found this recent paper very well done:

Bauer, J.E. and Stigall, A.L. 2016. A combined morphometric and phylogenetic revision of the Late Ordovician brachiopod genera Eochonetes and Thaerodonta. Journal of Paleontology 90: 888-909.

It does classic systematics on a group of brachiopods with the modern tools of morphometric and phylogenetic analyses. Its conclusions are direct and convincing: The genus Thaerodonta is synonymous with Eochonetes, and a variety of species are shifted around, solving problems that have lingered for over a century, Plus as a bonus, who can’t love a new species named Eochonetes voldemortus? So I set out to find specimens of this brachiopod group in our collections. Above are internal valve views of the brachiopod Eochonetes clarksvillensis (Foerste, 1912), showing characteristic denticles (little teeth) along the hinge line. Below are external valve views. Jen Bauer herself kindly confirmed the identifications!

These specimens come from the Waynesville Formation (Katian) exposed at Caesar Creek in southern Ohio, a place we have had many paleontology field trips. E. clarksvillensis is common in the Waynesville and overlying Liberty formations. Read much more about it in Bauer and Stigall (2016).

The genus Eochonetes was named by Frederick Richard Cowper Reed in 1917 from the Ordovician of Scotland. (The British Isles were not too far away from Ohio in the Late Ordovician.) Reed was born in London in 1869 and died in Cambridge, England, in 1946. I tried mightily but could find no images of him to enter into the digital archives of the web. He was a smart and diverse geologist, attending Trinity College, Cambridge, and winning important awards and scholarships. He was appointed assistant to the Woodwardian Professor of Geology at Cambridge in 1892, a position he kept until retirement. In 1901 he earned the Sedgwick Prize for his work on the rivers of East Yorkshire, wrote a book on the geology of the British Empire (much easier to do today!), and yet still found time to describe fossils in numerous papers.

The author of Eochonetes clarksvillensis is much better known to paleontologists of the Cincinnati region. It is August F. Foerste (1862-1936), who named Thaerodonta clarksvillensis in 1912. Foerste grew up and worked in the Dayton, Ohio, area, graduating from Denison University after publishing many papers as a student. He returned to Dayton after earning a PhD from Harvard, teaching high school for 38 years. When he retired he turned down a teaching position at the University of Chicago and instead worked at the Smithsonian Institution until the end of his life. He is one of the giants of the Cincinnati School of paleontology.

References:

Bauer, J.E. and Stigall, A.L. 2016. A combined morphometric and phylogenetic revision of the Late Ordovician brachiopod genera Eochonetes and Thaerodonta. Journal of Paleontology 90: 888-909.

Reed, F.R.C. 1917. The Ordovician and Silurian Brachiopoda of the Girvan District: Transactions of the Royal Society of Edinburgh 51: 795–998.

Wooster’s Fossil of the Week: A large trepostome bryozoan on a nautiloid conch (Upper Ordovician of northern Kentucky)

March 17th, 2017

This massive trepostome bryozoan, a solid lump of biogenic calcite, was collected earlier this week on the latest Team Cincinnati field expedition into the treasure-filled Upper Ordovician underlying and surrounding that city. Wooster students Matt Shearer, Luke Kosowatz and I are pursuing projects related to trepostome bryozoans and bioerosion (the biological destruction of hard substrates). The above specimen combines both these worlds, and more. Note the concavity at the base of the specimen. It comes from the Bellevue Formation (Katian) exposed on Bullitsville Road near the infamous Creation Museum (C/W-152).

Underneath the bryozoan colony (its zoarium) is this conical impression. It is an external mold of a straight nautiloid conch, the shell of a common squid-like cephalopod during the Ordovician. After the death of the nautiloid its empty tubular conch rested on the seafloor. This hard surface attracted the larvae of a variety of bryozoans that spread their calcitic zoaria (colonial skeletons) across the surface. Eventually one trepostome bryozoan species gained dominance over the space and occupied it all, growing into the large colony we see today. It even wrapped around the aperture of the conch (on the left) and grew a bit into the tube. Since the nautiloid conch was made of unstable aragonite, it long ago dissolved away, leaving an impression (external mold) in the stable calcite of the bryozoan.

How do we know there were earlier generations of bryozoans on this conch? We see them exposed upside-down on the surface of the external mold. Above we see the thin, branching cyclostome bryozoan Cuffeyella in the foreground, with a sheet of an encrusting trepostome bryozoan in the background. There are several other earlier bryozoans visible on this surface, revealing an ecological succession. There may be soft-bodied organisms preserved on this surface as well. This locality yielded the first described specimens of bioimmuration in the Ordovician (see Wilson et al., 1994).

There were other large trepostome bryozoans found in this same locality. I couldn’t resist cutting one in half to see what the inside looked like.

In this close view of the cross-section through the calcitic trepostome bryozoan we see numerous round holes drilled by some sort of worm seeking protective space so it could filter-feed. (In other words, it was not preying on the bryozoan.) The most intense boring of the specimen appears to have taken place just before and after the death of the colony. We know some borings were excavated into living bryozoan skeleton because the bryozoan formed reactive tissue around the intruder. The very tiny reddish-brown dots scattered in layers are “brown bodies“, the organic remnants of bryozoan polypides in their skeletal tubes (zooecia).

It has been a pleasure to return to the extraordinary Cincinnati fossils!

References:

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

Wilson, M.A. 1985. Disturbance and ecologic succession in an Upper Ordovician cobble-dwelling hardground fauna. Science 228: 575-577.

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.

Team Cincinnati moves into Kentucky for additional fieldwork

March 12th, 2017

Maysville, Kentucky — It was another frigid morning under the clear, pitiless skies of the Cincinnati region, but Luke Kosowatz (’17) was in good spirits. He is collecting at our first stop of the day: an exposure of the Bellevue Formation (Upper Ordovician, Katian) along the Bullitsville Road in northern Kentucky (N 39.08121°, W 84.79230°; C/W-152). Luke is sorting out bioeroded bryozoans and brachiopods here.

Matt Shearer (’18) joins Luke on the outcrop. If the place looks familiar it’s because William Harrison (’15) and I were here almost exactly three years ago.

In cosmic irony, the Bullitsville outcrop is nearly a neighbor of the Creation Museum. It was closed this Sunday morning — who would have guessed? Do Creationists ponder the fact that their pseudoscientific establishment sits on an incredible record of fossils 450 million years old? They do indeed: “These conditions and processes would be expected during the global catastrophic Flood described in the Scriptures. The thin alternating coarse-grained limestone and fine-grained shale layers could be deposited quickly under such catastrophic conditions.” Of course.

We were also near Big Bone Lick State Park, the birthplace of American vertebrate paleontology.

This site has an excellent life-sized diorama of Late Pleistocene animals (mammoths, mastodons, bison, ground sloths and even vultures) getting mired in bogs infused with salty water.

Team Cincinnati then traveled east for about an hour to the magnificent exposures of the Cincinnatian Group around Maysville, Kentucky. Here we targeted the Corryville Formation exposed along the AA Highway (N 38.60750°, W 83.76775°).

As with all our sites, the fossils are extraordinary. This is an ordinary slab of limestone from the Corryville with dozens of well-preserved strophomenid brachiopods.

For nostalgia on my part, we visited an outcrop along US 62 at the southern edge of Maysville where the Corryville Formation is again exposed (N 38.60932°, W 83.81070°). It is at this site that I collected a cave-dwelling bryozoan fauna now the subject of a manuscript Caroline Buttler (National Museum Wales) and I are finishing up this month. The cave interval was destroyed by later roadwork, but the remaining outcrops were superb for our purposes.

We ended the field day about seven kilometers north at another outcrop of the Corryville along US 62 (N 38.6445°, W 83.77678°).  I was so distracted by the diversity of fossils that I forgot to take pictures!

Dinner was at El Caminante Mexican Restaurant in Maysville. It was so good we are compelled to recommend it to future geological visitors.

Wooster Geologists launch Team Cincinnati 2017

March 11th, 2017

Harrison, Ohio — Our first fieldwork of the year started on this cold, cold March day in southeastern Indiana. (Note the white icicles on the outcrop.) Luke Kosowatz, Matt Shearer and I have begun our projects in the magnificent Cincinnatian Group (Upper Ordovician, Katian) with its fantastic fossils on the first day of Wooster’s spring break. Despite the sunlight, it was 19°F when we had to leave the warm vehicle to start collecting fossils at our first stop shown above. This is the US 27 roadcut outside Richmond, Indiana, beloved by paleontologists (N 39.78631°, W 84.90318°). Here the upper Whitewater Formation is well exposed and weathered just right to release millions of fossils from their rocky tombs. Luke is studying patterns of bioerosion (almost entirely borings) in the Cincinnatian for his Independent Study thesis, and Matt is examining the distribution of bryozoan taxa for his I.S. work. We’ll have more details on their investigations later.

Today we started at the top of the Cincinnatian Group and worked our way down section as we moved south through Indiana towards the Ohio River. One of our sites was the Brookville Lake Dam emergency spillway exposure, seen above on the other end of the dam.

We climbed up the dam itself to get to the spillway exposure, which is magnificent. We did not collect here, though, because we couldn’t assure tight stratigraphic control of our specimens. There is too much downslope movement of fossils and rocks at this site for us to be certain about the horizons from which the fossils came.

Southgate Hill is a spectacular series of roadcuts north of St. Leon, Indiana (N 39.33909°, W 84.95306°). Matt and Luke are here collecting from the top of the Waynesville Formation.

Our last outcrop of the day was at the top of this sequence of limestones and shales exposed at another large roadcut, this one near Lawrenceburg, Indiana (N 39.09863°, W 84.87683°). At the very top is the rubbly Bellevue Formation, from which we collected magnificent trepostome bryozoans, many with beautiful borings.

Despite the temperatures, we had fun today and look forward to another three days of field paleontology in what must be the most fossiliferous rocks in the world. We are fortunate to live so close to these treasures.

Wooster’s Fossil of the Week: Encrusting craniid brachiopods (Upper Ordovician of southeastern Indiana)

March 10th, 2017

The two irregular patches above are brachiopods known as Petrocrania scabiosa encrusting the ventral valve of yet another brachiopod (Rafinesquina). That species name “scabiosa” is evocative if not a little unpleasant — it is also the root of the English “scab”.

Petrocrania scabiosa is in a group of brachiopods we used to call “inarticulates” because their two valves are not articulated by a hinge as they are in most brachiopods. Instead they are held together by a complex set of muscles. Now we place these brachiopods in the Class Craniforma, an ancient group which originated in the Cambrian and is still alive today.

Petrocrania scabiosa was a filter-feeder like all other brachiopods, extracting nutrients from the seawater with a fleshy lophophore. The Wooster specimens are part of our large set of encrusting fossils (a type of sclerobiont) in our hard substrate collection. They have irregular shells that are circular in outline when they grew alone, and angular when they grew against each other.

Some craniid brachiopods were so thin that their shells repeated the features of the substrate underneath them, a phenomenon known as xenomorphism (“foreign-form”).

Petrocrania scabiosa brachiopods (circular) on a Rafinesquina brachiopod, along with a trepostome bryozoan that encrusted some brachiopods and grew around others. The P. scabiosa on the far left shows xenomorphic features. Specimen borrowed from the University of Cincinnati paleontology collections.

A 2007 College of Wooster paleontology field trip to the Upper Ordovician locality near Richmond, Indiana, where these specimens were found. Students are in the traditional paleontological poses.

[Originally published May 22, 2011.]

Wooster’s Fossil of the Week: Mysterious tentaculitids (Devonian of Maryland)

March 3rd, 2017

The sharp little conical fossils above are common Paleozoic fossils, especially in the Devonian. They are tentaculitids now most commonly placed in the Class Tentaculitoidea Ljashenko 1957. Tentaculitids appeared in the Ordovician and disappeared sometime around the end of the Carboniferous and beginning of the Permian. These specimens are from the Devonian of Maryland.

The systematic placement of the tentaculitids has been controversial. Their straight, narrow shells are usually ornamented by concentric rings, and many had septa (thin shelly partitions) inside the cones. The microstructure of the shells is most interesting — it looks very much like that of brachiopods and bryozoans. For this reason and several others, several of my colleagues and I believe the tentaculitids were lophophorates (animals that filter-feed with a tentacular device called a lophophore). They may thus be related to other problematic tubeworms like microconchids and cornulitids (Taylor et al., 2010).

Tentaculitids from the New Creek Limestone (Lochkovian, Early Devonian) of New Creek, West Virginia.

Knowing how the tentaculitids fit into an evolutionary scheme, though, has not helped us figure out what they did for a living. The figure below, from Cornell et al. (2003), shows these funny cones in just about every lifestyle imaginable!

References:

Cornell, S.R., Brett, C.E. and Sumrall, C.D. 2003. Paleoecology and taphonomy of an edrioasteroid-dominated hardground association from tentaculitid limestones in the Early Devonian of New York: A Paleozoic rocky peritidal community. Palaios 18: 212-224.

Taylor, P.D., Vinn, O. and Wilson, M.A. 2010. Evolution of biomineralization in ‘lophophorates’. Special Papers in Palaeontology 84: 317-333.

[Originally published May 29, 2011.]

Wooster’s Fossil of the Week: A scaphitid ammonite (Late Cretaceous of Mississippi)

February 24th, 2017

The beauty above is Discoscaphites iris (Conrad, 1858) from the Owl Creek Formation of Ripley, Mississippi. Megan Innis and I collected it during our expedition to the Cretaceous-Paleogene boundary in the southern United States last summer. It is a significant index fossil in biostratigraphy: the Discoscaphites iris Zone is the latest in the Cretaceous (the late Maastrichtian Stage). This animal lived in the final days of the Mesozoic Era just before the mass extinction 65.5 million years ago.

Discoscaphites iris is an ammonite, a type of extinct cephalopod mollusk related to the modern octopus, squid and nautilus. It had a planispirally-coiled shell with chambers divided from each other by complexly-folded walls. If you look closely near the top of the fossil above, you will see where the shell has flaked away revealing an internal mold of sediment and a peek at the folded walls inside. “Ammonite”, by the way, is a very old term for these fossils. Pliny the Elder himself used a variant of the name, which comes from the Egyptian god Amun with his occasional coiled ram’s horn headgear.

Reconstruction of an ammonite by Arthur Weasley (via Wikipedia).

Ammonite shells were made of the carbonate mineral aragonite. This is the mineral that makes many modern mollusk shells have prismatic colors, which we call nacreous. You may know it best as “mother of pearl” or as pearls themselves. Aragonite has an unstable crystal structure and so is not common in rocks older than a few million years. The original aragonite in our ammonite fossil is thus a bonus.

In an oddly topical note, Discoscaphites iris was recently found in the Upper Cretaceous of Libya, giving it a disjunct range from the US Gulf and Atlantic coasts to the Mediterranean coast of northern Africa (Machalski et al., 2009).

Reference:

Machalski, M., Jagt, J.W.M., Landman, N.H. and Uberna, J., 2009. First record of the North American scaphitid ammonite Discoscaphites iris from the upper Maastrichtian of Libya. N. Jb. Geol. Paläont. Abh. 254: 373-378.

[Originally published April 24, 2011]

Wooster’s Fossil of the Week: A stromatoporoid (Middle Devonian of central Ohio)

February 17th, 2017

Stromatoporoids are very common fossils in the Silurian and Devonian of Ohio and Indiana, especially in carbonate rocks like the Columbus Limestone (from which the above specimen was collected). Wooster geologists encountered them frequently on our Estonia expeditions in the last few years, and we worked with at least their functional equivalents in the Jurassic of Israel (Wilson et al., 2008).

For their abundance, though, stromatoporoids still are a bit mysterious. We know for sure that they were marine animals of some kind, and they formed reefs in clear, warm seas rich in calcium carbonate (DaSilva et al., 2011). Because of this tropical habit, early workers believed they were some kind of coral, but now most paleontologists believe they were sponges. Stromatoporoids appear in the Ordovician and are abundant into the Early Carboniferous. The group seems to disappear until the Mesozoic, when they again become common with the same form and life habits lasting until extinction in the Late Cretaceous (Stearn et al., 1999).

The typical stromatoporoid has a thick skeleton of calcite with horizontal laminae, vertical pillars, mounds on the upper surface called mamelons, and dendritic canals called astrorhizae shallowly inscribed on the mamelons. These astrorhizae are the key to deciphering what the stromatoproids. They are very similar to those on modern hard sponges called sclerosponges. Stromatoporoids appear to be a kind of sclerosponge with a few significant differences (like a calcitic instead of an aragonitic skeleton).

Stromatoporoid anatomy from Boardman et al. (1987).

Top surface of a stromatoporoid from the Columbus Limestone showing the mamelons.

There is considerable debate about whether the Paleozoic stromatoporoids are really ancestral to the Mesozoic versions. There may instead be some kind of evolutionary convergence between two groups of hard sponges. The arguments are usually at the microscopic level!

The stromatoporoids were originally named by Nicholson and Murie in 1878. This gives us a chance to introduce another 19th Century paleontologist whose name we often see on common fossil taxa: Henry Alleyne Nicholson (1844-1899). Nicholson was a biologist and geologist born in England and educated in Germany and Scotland. He was an accomplished writer, authoring several popular textbooks, and a spectacular artist of the natural world. Nicholson taught in many universities in Canada and Great Britain, finally ending his career as Regius Professor of Natural History at the University of Aberdeen.

Henry Alleyne Nicholson (1844-1899) from the University of Aberdeen museum website.

References:

Boardman, R.S., Cheetham, A.H. and Rowell, A.J. 1987. Fossil Invertebrates. Wiley Publishers. 728 pages.

DaSilva, A., Kershaw, S. and Boulvain, F. 2011. Stromatoporoid palaeoecology in the Frasnian (Upper Devonian) Belgian platform, and its applications in interpretation of carbonate platform environments. Palaeontology 54: 883–905.

Nicholson, H.A. and Murie, J. 1878. On the minute structure of Stromatopora and its allies. Linnean Society, Journal of Zoology 14: 187-246.

Stearn, C.W., Webby, B.D., Nestor, H. and Stock, C.W. 1999. Revised classification and terminology of Palaeozoic stromatoporoids. Acta Palaeontologica Polonica 44: 1-70.

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

[Originally published on October 30, 2011]

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