Wooster Geologists begin fieldwork in southwestern France

June 1st, 2017

LA BARDE, FRANCE–Macy Conrad and I began our paleontological fieldwork in what may be the most beautiful part of Europe: southwestern France. Our superb guide and colleague is Natural History Museum scientist Dr. Paul Taylor, a long-time friend who has a home in this region with his wife Patricia. Above is a view of our first location: Aubeterre-sur-Drone. Extraordinary. And note the weather!

French food is indeed all it is said to be. This was my lunch: Gallette au Thon. Simple, I know, but very good.

This is our first outcrop. Macy is standing at an exposure of the Biron Formation, a Cretaceous (Campanian) limestone full of fossils, especially Pycnodonte oysters. Many of these oysters are encrusted by bryozoans. This is the “Garage Esso” location, also known as Route D17, in Aubeterre. We are in the exploratory phase of the project — essentially sorting out projects.

The overlying Barbezieux Formation (also Campanian — all the units are Campanian today) has well-exposed Pycnodonte oyster banks. These are of particular interest to us, especially if they are bored or encrusted. This is the “Chemin” section in Aubeterre.

More Barbezieux Formation further up the lane.

Our third unit is the Aubeterre Formation, which dominates the top of the city. This is the “car park outcrop”. All of these rocks are cliff-forming white limestones with abundant fossils.

Paul knew a field near Le Maine Roy where fossils from the Maurens Formation are exposed. This did not sound like a productive site, but it was the best of the day. Above you see a pile of rocks marked by a stake. These are larger stones removed from the fields by farmers. (I was reminded of what many French farmers in the north continually extract from their soil: World War I artillery shells!)

The many fossils include numerous large rudistid clams. It is  hard to imagine these large cones as bivalves, but they are. Rudists go extinct at the end of the Cretaceous.

This is a view of the top of a rudist with its right (capping) valve intact. It has a beautiful mesh structure.

Our last stop of the day was a roadcut near Chalais exposing the Biron Formation. It had a great diversity of fossils, including echinoids, sponges, oysters, and ammonites. It did not have an abundance of sclerobionts, so it probably won’t be a site for us in the future.

In Aubeterre we visited two fantastic churches. The first was St. Jacques. Most of it had been destroyed in the 17th century religious wars, but the Romanesque facade remains. This is the main entrance.

The primary attraction of the remnants of St. Jacques is a set of Medieval carvings. They are extraordinarily detailed, depicted all sorts of mysterious fantastical animals and people.

The second church in Aubeterre is very geological. St. Johns is underground, being carved as a cavern from the Barbezieux Formation. Here is a view of the entrance to what remains.

Inside is a huge space in which the sanctuary is carved. This is one of the largest such underground structures known.

The centerpiece is this reliquary, designed to look like the structure over the tomb of Jesus in the Church of the Holy Sepulchre in Jerusalem. Again, all this is carved out of the limestone.

We are staying in the gorgeous French home of Paul and Patricia Taylor in La Barde. It is an 1820 converted farmhouse, both beautiful and comfortable. The River Dronne is just a few steps away. We’ll have more photos of this wonderful and peaceful place in later posts.

I’ll end this day’s post with a view of some peaceful French woods near a field site.

Location GPS Unit Position
Garage Esso, Route D17, Aubeterre 153 Biron N45° 16.212′ E0° 10.274′
Route D17, Aubeterre 154 Barbezieux N45° 16.127′ E0° 10.268′
Chemin, Aubeterre 155 Barbezieux N45° 16.088′ E0° 10.257′
50 m up lane, Aubeterre 156 Barbezieux N45° 16.115′ E0° 10.229′
Back Chateau entrance, Aubeterre 157 Aubeterre N45° 16.362′ E0° 10.262′
Car Park, Aubeterre 158 Aubeterre N45° 16.344′ E0° 10.176′
Le Maine Roy 159 Maurens N45° 19.383′ E0° 07.885′
Chalais roadcut 160 Biron N45° 16.642′ E0° 02.395′

 

Wooster Geologist in Austria

May 27th, 2017

VIENNA, AUSTRIA–I had the privilege this week to attend the 14th Larwood Symposium of the International Bryozoology Association (IBA) in this beautiful city. It was my first visit, and I was of course very impressed. Above is a view of the Austrian Parliament building (Parlamentsgebäude), and the beautiful blue sky we had for most of our meeting.

About 50 bryozoan experts from 15 countries attended the conference. I love these meetings because of their small size, diversity of disciplines (paleontologists and biologists freely mingle, being nearly indistinguishable until they give their presentations), and friendly fellowship. English was the common language, for which I am grateful to my international colleagues. Above Lee Hsiang Liow of the University of Oslo is giving her talk.

We had an afternoon excursion starting with the small but treasure-filled Krahuletz Museum in Eggenburg, Austria. This is one of those local museums with a national reputation for particular collections. In this case it is fossils, minerals and rocks from the very complex region.

Outside the museum is an excellent rock garden with local varieties well labeled. The above, of course, is a conglomerate with mostly carbonate clasts.

This gneiss shows the useful form of the rock pillars. Four sides are polished and the top is left rough, just the way a geologist likes it.

Patrick Wyse Jackson, President of the IBA, professor at Trinity College Dublin, and a recent visitor in Wooster, manages here to find bryozoans in the museum’s building stone.

After the museum we visited a quarry of fossiliferous Miocene limestone. A nice place, but protected from collecting.

At the end of the day we visited “Fossilienwelt Weinviertel” outside Vienna. It is home to the world’s largest fossil pearl (which somehow I missed seeing) and an excavated Miocene oyster reef. The reef has at least 20,000 large oysters, which are the subject of this “geotainment park”. More than 200 volunteers excavated this reef for public display under a permanent canopy. The oysters seem to have been tossed together by a flood, so they are pushing the definition of “reef”. The lighting of the oysters was so dim that my photographs of them were worthless.

The Fossil World tower is shaped like a Turritella shell.

Here is one of the oysters and some Turritella shells on display at Fossil World. There are many more fossils here than snails and oysters. It is a fun exhibit, but the science has been so diluted for the public that some of the offered explanations are nonsense. (“Stromatolites are made of the poop of algae”.) I recommend a visit, but with a paleontologist as a guide!

Thank you to Thomas Schwaha for organizing this fun trip!

Our IBA group photo, courtesy of Thomas Schwaha.

Wooster’s Fossils of the Week: A trilobite hypostome with an encrusting cyclostome bryozoan (Upper Ordovician of Kentucky)

May 26th, 2017

A quick post this week. Above is a bit of a large isotelid trilobite my students and I found this past spring break on an expedition to the Upper Ordovician (Katian) of northern Kentucky. It was collected at a roadside outcrop of the Corryville Formation (Location C/W-740). It doesn’t look like the usual trilobite bit because it is a less common fragment from the underside of the cephalon known as the hypostome (meaning “under mouth”). Note on the left side of the image some branching white encrustations, shown closer below.

These are encrusting cyclostome bryozoans known as Cuffeyella arachnoidea. The genus Cuffeyella was named in 1996 by two characters you know from this blog: Taylor & Wilson. As you can see, these particular specimens are in terrible shape. We have far better images of well-preserved Cuffeyella elsewhere on this blog. One of the lessons of a paleontological education, though, is to learn how to recognize fossils when they are not at their best.

Wooster’s Fossil of the Week is now going to take a hiatus as the summer research and travel season begins. It will return later!

Reference:

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.

Wooster’s Fossils of the Week: A bouquet of barnacles on a pectenid bivalve from the Upper Miocene of Virginia

May 19th, 2017

These beautiful fossils were found in York State Park by Mae Kemsley (’16). It was a surprise gift I found on my doorstep! They are fossil barnacles completely covering the exterior of a valve of the pectenid bivalve Chesapecten middlesexensis (Mansfield, 1936) from the Upper Pliocene. An excellent example of an ancient sclerobiont community.
This is the reverse of the specimen, showing the interior of the host shell. Note the large single muscle scar typical of monomyarian pectenid bivalves.
Chesapecten is well known among paleontologists. The genus preserves a distinct evolutionary sequence, as seen in the above famous figure from Ward and Blackwelder (1975). This image has been reproduced in countless articles and textbooks.
Chesapecten was also the first fossil from North America to be illustrated in a scientific publication. The above image of what we now know as Chesapecten jeffersonius was illustrated in the third volume of Martin Lister’s Historiae Conchyliorum in 1687.
Martin Lister FRS (1639 – 1712) was a natural historian and physician born into a prominent family in Radcliffe, England. His father, Sir Martin Lister, was a member of the Long Parliament in the eventful politics of mid-17th century England. He was a nephew of James Temple, a regicide (or patriot, take your choice) and Sir Matthew Lister, physician to Charles I (victim of said regicide). These were just a few of his family connections to politics and science.

Martin Lister was graduated from St John’s College, Cambridge, in 1659, and a year later elected a fellow there. He served as a physician for many years in York, including three years as Queen Anne’s doctor. He became a Fellow of the Royal Society in 1671. He died in Epsom in 1712.

Martin Lister was an extraordinary naturalist, becoming the first conchologist (one who studies shells) and arachnologist (a spider expert). He was a prolific writer, so we know much about what he did, how he worked, and his motivations. He discovered ballooning spiders and invented the ubiquitous histogram. For us his most significant work was Historiae Conchyliorum (1685-1692), which had 1062 plates engraved by his daughters, Anna and Susanna. In keeping with his times, Lister noted the resemblances between fossil and modern shells, but believed the fossils were rocky replicas, not actual remnants of living organisms. He would no doubt be thrilled with our modern views of fossils and evolution.

References:

Kelley, P.H. 1983. The role of within-species differentiation in macroevolution of Chesapeake Group bivalves. Paleobiology 9: 261-268.

Lister, M. 1687. Historiae Conchyliorum, volume III. Londini, aere incisi, sumptibus authoris.

Ward, L.W. and Blackwelder, B.W. 1975. Chesapecten, a new genus of Pectinidae (Mollusca, Bivalvia) from the Miocene and Pliocene of eastern North America: USGS Professional Paper 861. US Government Printing Office.

Wooster’s Fossils of the Week: Belemnites (Jurassic of Wyoming)

May 12th, 2017

This week’s fossils are among the most recognizable. They certainly are popular in my paleontology courses because no one has ever misidentified one. Belemnites (from the Greek belemnon, meaning javelin or dart) were squid-like cephalopods that lived in the Jurassic and Cretaceous Periods. You would never guess their original appearance from the fossils above. These are guards or rostra, internal hard parts that look nothing like the external animal. They are often found in large accumulations called “belemnite battlefields” (Doyle and MacDonald, 1993).
The above image shows a remarkable fossil belemnite in the State Museum of Natural History, Stuttgart, Germany (courtesy of User Rai’ke on Wikimedia). It shows their squidy form and ten equal-sized arms studded with little hooks for holding prey. They probably ate small fish and invertebrates.
The guard or rostrum is solid calcite at its distal end with a phragmocone (chambered shell) at the other. This phragmocone is only rarely preserved. The rostrum above is from the Zohar Formation (Jurassic) of the Golan in northern Israel near Neve Atif.

Belemnites have played an important role recently in sorting out Mesozoic climate change. Their solid calcitic rostra are ideal for examining stable isotopes that fluctuated with water temperature. Dera et al. (2011) showed that the Jurassic had significant climate variations based on the isotopes in belemnite fossils.

Belemnites have a long history in folklore. The English called them “thunderbolts” because they thought they were formed by lightning strikes. The Scottish knew them as “botstones” that cured horses of various ailments. The Swedish thought they were “gnome candles”. The Chinese called them “sword stones”. Much more prosaically, the belemnite is the state fossil of Delaware.
An engraving of belemnite rostra by Captain Thomas Brown (1889).

References:

Brown, Captain T. 1889. An atlas of fossil conchology of Great Britain and Ireland. With descriptions of all the species. Swan Sonnenschein & Co.

Dera, G., Brigaud, B., Monna, F., Laffont, R., Pucéat, E., Deconinck, J-F., Pellenard, P., Joachimski, M.M., and Durlet, C. 2011. Climatic ups and downs in a disturbed Jurassic world. Geology 39: 215–218.

Doyle, P. and MacDonald, D.I.M. 1993. Belemnite battlefields. Lethaia 26: 65-80.

[Originally published on November 20, 2011.]

Wooster’s Fossil of the Week: a medullosalean pteridosperm (Upper Carboniferous of northeastern Ohio)

May 5th, 2017

It is time we had another fossil plant in this series. The above specimen is Neuropteris ovata Hoffmann 1826, a relatively common bit of foliage in the Upper Carboniferous of North America. This is a pteridosperm, more commonly known as a seed fern. They weren’t really ferns at all but fern-like plants with some of the first real seeds. They are usually reconstructed as trees, but were also known to be bushy or even like climbing vines.

The taxonomy (naming system) of fossil plants can be very complicated because different plant parts were given different names at different times. A single plant species, then, could have a list of names for its foliage, bark, roots, seeds, etc. The name Neuropteris usually thus refers to the leaves of this particular pteridosperm.

Neuropteris ovata is famous for its use in studies of the distribution of stomata on its leaf surfaces. Stomata, sometimes called guard cells, regulate gas exchange and moisture retention in vascular land plants. The density of stomata on N. ovata leaves in the Late Carboniferous may reflect changes in carbon dioxide levels and the expansion and contraction of tropical forests (Cleal et al., 1999).

Neuropteris ovata was named by Friedrich Hoffmann (1797-1836), a Professor of Geology at the University of Berlin. I wish I knew more about him because not only did he do considerable paleobotanical research, he was also well known for his work on volcanoes in Italy. You don’t see that combination very often!

References:

Beeler, H.E. 1983. Anatomy and frond architecture of Neuropteris ovata and N. scheuchzeri from the Upper Pennsylvanian of the Appalachian Basin. Canadian Journal of Botany 61: 2352-2368.

Cleal, C.J., James, R.M. and Zodrow, E.L. 1999. Variation in stomatal density in the Late Carboniferous gymnosperm frond Neuropteris ovata. Palaios 14: 180-185.

Hoffmann, F. 1826. Untersuchungen über die Pänzen-Reste des Kohlengebirges von Ibbenbühren und von Piesberg bei Osnabrück. Archiv für Bergbau und Hüttenwesen 13: 266-282.

Zodrow, E.L. and Cleal, C.J. 1988. The structure of the Carboniferous pteridosperm frond Neuropteris ovata Hoffman. Palaeontographica Abteilung Palaophytologie 208: 105-124.

[Originally posted on October 23, 2011.]

Wooster’s Fossils of the Week: Sponge and clam borings that revealed an ancient climate event (Upper Pleistocene of The Bahamas)

April 28th, 2017

This week’s fossils celebrate the publication today of a paper in Nature Geoscience that has been 20 years in the making. The title is: “Sea-level oscillations during the Last Interglacial highstand recorded by Bahamas coral”, and the senior author is the geochronological wizard Bill Thompson (Woods Hole Oceanographic Institution). The junior authors are my Smith College geologist friends Al Curran and Brian White and me.

The paper’s thesis is best told with an explanation of this 2006 image:
This photograph was taken on the island of Great Inagua along the coast. The flat dark surface in the foreground is the top of a fossil coral reef (“Reef I”) formed during the Last Interglacial (LIG) about 123,000 years ago. It was eroded down to this flat surface when sea-level dropped, exposing the reef to waves and eventually terrestrial weathering. The student sitting on this surface is Emily Ann Griffin (’07), one of three I.S. students who helped with parts of this project. (The others were Allison Cornett (’00) and Ann Steward (’07).) Behind Emily Ann is a coral accumulation of a reef (“Reef II”) that grew on the eroded surface after sea-level rose again about 119,000 years ago. These two reefs show, then, that sea-level dropped for about 4000 years, eroding the first reef, and then rose again to its previous level, allowing the second reef to grow. (You can see an unlabeled version of the photograph here.) The photograph at the top of this post is a small version of the same surface.

The significance of this set of reefs is that the erosion surface separating them can be seen throughout the world as evidence of a rapid global sea-level event during the Last Interglacial. Because the LIG had warm climatic conditions similar to what we will likely experience in the near future, it is crucial to know how something as important as sea-level may respond. The only way sea-level can fluctuate like this is if glacial ice volume changes, meaning there must have been an interval of global cooling (producing greater glacial ice volume) that lowered sea-level about 123,000 years ago, and then global warming (melting the ice) that raised it again within 4000 years. As we write in the paper, “This is of great scientific and societal interest because the LIG has often been cited as an analogue for future sea-level change. Estimates of LIG sea-level change, which took place in a world warmer than that of today, are crucial for estimates of future rates of rise under IPCC warming scenarios.” With our evidence we can show a magnitude and timing of an ancient sea-level fluctuation due to climate change.

Much of the paper concerns the dating techniques and issues (which is why Bill Thompson, the essential geochronologist, is the primary author). It is the dating of the corals that makes the story globally useful and significant. Here, though, I want to tell how the surface was discovered in the first place. It is a paleontological tale.

In the summer of 1991 I worked with Al Curran and Brian White on San Salvador Island in The Bahamas. They were concentrating on watery tasks that involved scuba diving, boats and the like, while I stayed on dry land (my preferred environment by far). I explored a famous fossil coral exposure called the Cockburntown Reef (Upper Pleistocene, Eemian) that Brian and Al had carefully mapped out over the past decade. The Bahamian government had recently authorized a new harbor on that part of the coastline and a large section of the fossil reef was dynamited away. The Cockburntown Reef now had a very fresh exposure in the new excavation quite different from the blackened part of the old reef we were used to. Immediately visible was a horizontal surface running through the reef marked by large clam borings called Gastrochaenolites (see below) and small borings (Entobia) made by clionaid sponges (see the image at the top of this post).
Inside the borings were long narrow bivalve shells belonging to the species Coralliophaga coralliophaga (which means “coral eater”; see below) and remnants of an ancient terrestrial soil (a paleosol). This surface was clearly a wave-cut platform later buried under a tropical soil.


My colleagues and I could trace this surface into the old, undynamited part of the Cockburntown Reef, then to other Eemian reefs on San Salvador, and then to other Bahamian islands like Great Inagua in the far south. Eventually this proved to be a global erosion surface described or at least mentioned in many papers, but its significance as an indicator of rapid eustatic sea-level fall and rise was heretofore unrecognized. Finally getting uranium-thorium radioactive dates on the corals above and below the erosion surface placed this surface in a time framework and ultimately as part of the history of global climate change.

This project began 25 years ago with the discovery of small holes left in an eroded surface by humble sponges and clams. Another example of the practical value of paleontology.

References:

Thompson, W.G., Curran, H.A., Wilson, M.A. and White, B. 2011. Sea-level oscillations during the Last Interglacial highstand recorded by Bahamas coral. Nature Geoscience (DOI: 10.1038/NGEO1253).

White, B.H., Curran, H.A. and Wilson, M.A. 1998. Bahamian coral reefs yield evidence of a brief sea-level lowstand during the last interglacial. Carbonates and Evaporites 13: 10-22.

Wilson, M.A., Curran, H.A. and White, B. 1998. Paleontological evidence of a brief global sea-level event during the last interglacial. Lethaia 31: 241-250.

[Originally posted September 11, 2011. Some updates and editing.]

Wooster’s Fossil of the Week: A Biserial Graptolite (Middle Ordovician of Tennessee)

April 21st, 2017

This week’s fossils are graptolites (from the Greek for written rocks) I found many years ago in the Lebanon Limestone near the town of Caney Springs south of Nashville, Tennessee. They are of the genus Amplexograptus and probably belong to the species A. perexcavatus (Lapworth, 1876).

Graptolites were colonial organisms consisting of hundreds and sometimes thousands of tiny zooids (individuals) connected together in a flexible proteinaceous skeleton (the rhabdosome). They first appeared in the Late Cambrian (around 510 million years ago) and disappeared forever in the Early Carboniferous (around 350 million years ago). Amplexograptus colonies were probably attached to floats so they could drift through the ancient oceans filtering out organic particles; they would be officially “passively mobile planktonic suspension feeders”. They belong to the Phylum Hemichordata, although there have always been disputes about their actual evolutionary relationships. This matters because graptolites are important index fossils for sorting out the age relationships of Lower and Middle Paleozoic rocks.

Graptolites are usually preserved as thin carbonaceous films on dark shales, making them rather hard to see (as my paleontology students will readily agree). The great 18th Century naturalist Linnaeus even said that they were “pictures resembling fossils rather than true fossils”. Sometimes, though, they are found in lighter-colored rocks like limestones, as above. Goldman et al. (2002) found Amplexograptus in limestones preserved in three dimensions, possibly because the limestones were cemented early around them before they collapsed with decay. They even studied this same species from the Lebanon Limestone. The 3-D preservation allows for a much more detailed analysis of the tiny cups (thecae) which held the individual zooids. It is possible that I could dissolve the limestone shown above and retrieve some delicate three-dimensional graptolites — but I could also just as easily destroy them.

Amplexograptus perexcavatus was originally described in 1876 by the famous geologist Charles Lapworth (1842-1920), who referred it to the genus Diplograptus. Actually, he had two species in his D. perexcavatus group, so it took some taxonomic detective and legal work to fix the current naming system. Lapworth, who I’ve figured below with an inset of his not-very-helpful diagram of the original D. perexcavatus, is well known by paleontologists for his work with graptolites as index fossils. Scientists and historians of science know him as the man who invented the Ordovician Period in 1879 to solve a bitter dispute between Roderick Murchison and Adam Sedgwick who each claimed the same rock interval in Wales for the Silurian and Cambrian periods respectively. Lapworth’s primary biostratigraphic argument for the Ordovician as a separate period was the distribution of graptolites, including our friend Amplexograptus perexcavatus. (Murchison and Sedgwick were long gone by the time their dispute was settled.)

(Charles Lapworth. Image courtesy of The Lapworth Museum of Geology.)

References:

Goldman, D., Campbell, S.M. and Rahl, J.M. 2002. Three-dimensionally preserved specimens of Amplexograptus (Ordovician, Graptolithina) from the North American mid-continent: taxonomic and biostratigraphic significance. Journal of Paleontology 76: 921-927.

Lapworth, C. 1876. The Silurian System in the South of Scotland, p. 1–28. In: Armstrong, J. Young, J. and Robertson, D. (eds.), Catalogue of Western Scottish Fossils. Blackie and Son, Glasgow.

[Originally posted August 28, 2011]

Wooster’s Fossil of the Week: A Conulariid (Lower Carboniferous of Indiana)

April 14th, 2017

I have some affection for these odd fossils, the conulariids. When I was a student in the Invertebrate Paleontology course taught Dr. Richard Osgood, Jr., I did my research paper on them. I had recently found a specimen in the nearby Lodi City Park. It was so different from anything I had seen that I wanted to know much more. I championed the then controversial idea that they were extinct scyphozoans (a type of cnidarian including most of what we call today the jellyfish). That is now the most popular placement for these creatures today, although I arrived at the same place mostly by luck and naïveté. (I love the critical marks in that word! And yes, I always have to look them up.)

The specimen above is Paraconularia newberryi (Winchell) found somewhere in Indiana and added to the Wooster fossil collections before 1974. (The scale below it is in millimeters.) A close view (below) shows the characteristic ridges with a central seam on one of the sides.
Conulariids range from the Ediacaran (about 550 million years ago) to the Late Triassic (about 200 million years ago). They survived three major extinctions (end-Ordovician, Late Devonian, end-Permian), which is remarkable considering the company they kept in their shallow marine environments suffered greatly. Why they went extinct in the Triassic is a mystery.

The primary oddity about conulariids is their four-fold symmetry. They had four flat sides that came together something like an inverted and extended pyramid. The wide end was opened like an aperture, although sometimes closed by four flaps. Preservation of some soft tissues shows that tentacles extended from this opening. Their exoskeleton was made of a leathery periderm with phosphatic strengthening rods rather than the typical calcite or aragonite. (Some even preserve a kind of pearl in their interiors.) Conulariids may have spent at least part of their life cycle attached to a substrate as shown below, and maybe also later as free-swimming jellyfish-like forms.

It is the four-fold symmetry and preservation of tentacles that most paleontologists see as supporting the case for a scyphozoan placement of the conulariids. Debates continue, though, with some seeing them as belonging to a separate phylum unrelated to any cnidarians. This is what’s fun about extinct and unusual animals — so much room for speculative conversations!

[Thanks to Consuelo Sendino of The Natural History Museum (London) for correcting the age range of these fascinating organisms.]

References:

Hughes, N.C., Gunderson, G.D. and Weedon, M.J. 2000. Late Cambrian conulariids from Wisconsin and Minnesota. Journal of Paleontology 74: 828-838.

Van Iten, H. 1991. Evolutionary affinities of conulariids, p. 145-155; in Simonetta, A.M. and Conway Morris, S. (eds.). The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press, Cambridge.

[Modified from an original post on July 31, 2011]

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]

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