Wooster’s Fossil of the Week: A swimming clam from the Pliocene of Cyprus

Mark Wilson December 23, 2012 1:20 am

In the summer of 1996, I was a co-director of a Keck Geology Consortium project in Cyprus. One of my students was Steve Dornbos (’97), now a professor at the University of Wisconsin, Milwaukee. We had a great time exploring the Nicosia Formation (Pliocene) and its fossils on the Mesaoria Plain near the center of this Mediterranean island. (We published the study — Steve’s Independent Study thesis at Wooster — in 1999.)

One of our most common fossils in the Nicosia Formation is shown above. It is the pectinoid bivalve Amusium cristatum Röding, 1798. It is a remarkably thin and delicate shell that still retains much of its color after over four million years. Note that it is almost completely equilateral, meaning that it is nearly symmetrical. There’s a functional reason for this we’ll get to later.

Amusium is a genus still very much in existence today. They are usually found in abundance on carbonate platforms, often in the deeper portions. They are called “saucer scallops” or “moon shells” by collectors. There are many living species of Amusium, and they are apparently good eating (see below a platter from Thailand).

Both the genus and species of Amusium were named by Peter Friedrich Röding (1767–1846), a German shell specialist from Hamburg. He wrote a 1798 sale catalogue of a mollusk collection, providing the first publication of over 1500 taxonomic names. His descriptions were minimal, but enough to meet the requirements for new taxa, including Amusium cristatum.

Now, what is the functional importance of the symmetry of this particular scallop? Turns out it is one of the best swimmers in the bivalve world. By clapping its valves together with its strong adductor muscle, Amusium can swim at an average of 37-45 cm/second, usually for 8-10 seconds. Symmetry of the shell gives it good control over swimming direction. Features that also enhance the swimming abilities of Amusium include strengthening ribs (visible in our specimen above), a centrally-located adductor muscle, and a mantle that can direct water expulsion during the “clapping” actions of swimming.

We can be certain, then, that Amusium cristatum was a beautiful and unusually active mollusk in those shallow seas that once covered the beautiful island of Cyprus.

References:

Aguirre, J. 2009. Biological concentrations of Amusium cristatum. Journal of Taphonomy 2-3: 263-264.

Dornbos, S.Q. and Wilson, M.A. 1999. Paleoecology of a Pliocene coral reef in Cyprus: Recovery of a marine community from the Messinian Salinity Crisis. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 213: 103-118.

Morton, B. 1980. Swimming in Amusium pleuronectes (Bivalvia: Pectinidae). Journal of Zoology 190: 1469-7998.

Röding, P.F. 1798. Museum Boltenianum sive catalogus cimeliorum e tribus regnis naturæ quæ olim collegerat Joa. Fried Bolten, M.D. p. d. per XL. annos proto physicus Hamburgensis. Pars secunda continens conchylia sive testacea univalvia, bivalvia & multivalvia. – pp. [1-3], [1-8], 1-199. Hamburgi, Trapp.

Williams, M.J. and Dredge, M.C.L. 1981. Growth of the saucer scallop, Amusium japonicum balloti Habe, in central eastern Queensland. Australian Journal of Marine and Freshwater Research 32: 657–666.

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A spectacular glaciated valley near Ardara, County Donegal, Ireland

Mark Wilson December 20, 2012 4:51 pm

GlacialValleyArdaraDONEGAL, IRELAND — One last post from a great day in the Irish countryside. The above is Glengesh Pass, with the town of Ardara in the background. Glengesh means “Glen of the Swans”. On the south side (right in this image) is Common Mountain (503 meters high). This is a classic U-shaped glaciated valley. Someone has actually posted a YouTube video of driving through Glengesh Pass. (The accompanying music is an eccentric modern Irish ballad called “Las Vegas in The Hills of Donegal“. The fourth ranked Irish single in 1992!)

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Slieve League, County Donegal, Ireland

Mark Wilson December 20, 2012 4:36 pm

SlieveLeagueOneDONEGAL, IRELAND — The above peak sweeping precipitously down into a raging sea is the smaller of the exposures at Slieve League along the southern coast of County Donegal. These are the highest sea cliffs in Ireland, and among the highest in Europe. The road getting to this point had spectacular views along the way. (“Spectacular” means, of course, terrifying.)

SlieveLeagueThreeThis is a view of the highest of the Slieve League peaks, hidden by the fog. It is just over 600 meters from the sea to the peak. The trail up to it is said to be bracing.

SlieveLeagueTwoThe maelstrom at the base of Slieve League. This coast of Ireland has some of the best surfing in Europe, facing as it does the North Atlantic. Surfing right here, though, would be a bit tricky, but there is a landing beach.

Screen shot 2012-12-20 at 3.21.27 PMShanbally on the middle right in this Google Map is the highest point of Slieve League.

FoldedRocks122012There is some structural geology going on as you can see from these folded quartzites just east of Slieve League on Carrigan Head.

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The Grianán of Aileach

Mark Wilson December 20, 2012 3:46 pm

GriananOutsideDONEGAL, IRELAND — In the northeastern part of the county, about 7 km west of Derry in Northern Ireland, is Greenan Mountain. On its very top is a spectacular ringfort called The Grianán of Aileach (“the Solarium of Aileach”, shown above). From it are spectacular views of the countryside 360° around. It is a majestic and yet rather lonely place, maybe because my new friend Andy Quinn and I were the only ones there. It was probably built in some form around the beginning of the common era and no doubt occupied by many successive groups. There is a burial mound on the site (a tumulus) that may date back to 3000 BCE. The local story is that it was originally a place to honor the sun (which I would not have minded seeing today).

The fort’s most prominent days were when it was the royal citadel of the northern Ui Neill sept of Aileach from the 5th to the 12th century. The stone portion of the fort was destroyed in 1101 by Murtogh O’Brien, King of Munster. His soldiers were ordered to take the fort apart and scatter its stones widely. In 1870 it was substantially restored to its present state.

The Grianán of Aileach was an excellent location to visit and have a look at the countryside of eastern County Donegal. The rocks exposed here are among the oldest in Ireland (Late Proterozoic to Early Cambrian).

GriananInsideThe inside of the circular Grianán of Aileach. There are three interior platforms connected by narrow stairs. There is some dispute over whether this was the original architecture of the ringfort before its destruction in 1101.

GriananRocksThe stones are mostly without mortar. They appear to be some kind of quartz mica schist.

GriananPanorama585I tried a panorama of Lough Swilly to the west of the ringfort. It doesn’t convey the real sweeping vista in 585 pixels wide, but you get the idea of a cool view!

GriananHolyWellThis is a “holy well” to the southeast of the ringfort. It is said to have been visited by St. Patrick himself. Then again, everyone wants a connection to The Man!

An Irish myth says that The Grianán of Aileach was built by King Daghda of Tuatha de Danann, and that the grave of his son lies beneath the fortress forever guarding it. In any case, we were suitably respectful of this ancient site.

 

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The wild northwest of Ireland

Mark Wilson December 19, 2012 1:28 pm

DonegalBaySunset121912DONEGAL, IRELAND — Above is an image of Donegal Bay at sunset. It is striking with its still water, wheeling gulls and glacially-rounded rocky islands. I am in County Donegal for a couple of days simply to see the place and get some hints of what is said to be the most complex geology in Ireland. There is also some evidence that the Wilson part of my family comes from the northwest of Ireland, so I might be seeing a bit of ancestral homeland. I am staying in the town of Donegal in the south of the county and will be visiting sites in the north and west tomorrow. Today, after a very bumpy flight and landing (Donegal airport is known for its high winds), I am exploring the town and its surroundings.

DonegalArrival121912This is the little County Donegal airport in the north. It is in one of the most isolated spots in the county — no bus line goes to it and taxis have to be ordered in advance from nearby towns. There were seven people on the plane, including the crew.

AbbeyHotel121912The Abbey Hotel in downtown Donegal. My home for a couple of days.

DonegalAbbey121912The ruins of the Franciscan Abbey in Donegal along the southern shore of the bay. It was built in 1474. As with many such structures in Ireland, it has a long history of sieges and intrigue. This portion has been used as a graveyard for centuries.

DriftDonegal121912The geology just along the shores of Donegal Bay seems complicated enough. There are some rocky outcrops I could not reach, along with exposures of boulder-studded glacial drift such as here.

AbbeyGraveyard121912The stones used in the local walls and in the remaining Abbey structures are diverse. Most are dark gray metabasalts or amphibolites, as seen in this graveyard wall lit by the setting sun.

AbbeyStone121912One prominent stone in the Abbey walls appears to be a quartzite metaconglomerate. Both these rock types are derived from local pre-Paleozoic outcrops.

Aodh_Ruadh_Ó_Domhnaill_585Finally, here is a dramatically-lit statue of Aodh Ruadh Ó Domhnaill (1427-1505) at the head of Donegal Bay and mouth of the River Eske. He was the subject of one of my favorite book-movie combinations as a kid: The Fighting Prince of Donegal. I also think he looks a lot like me, wouldn’t you say?

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Three Amigos in Dublin

Mark Wilson December 18, 2012 6:04 pm

ThreeAmigos121812_585DUBLIN, IRELAND — I have paleontological legends on either side of me, and the best of friends. Paul Taylor is on the left. He and I met in 1985 when I visited The Natural History Museum in London while on my first research leave. My Oxford host, Stuart McKerrow, said I just had to meet a young paleontologist at the museum because we had so many common interests. Indeed. Paul and I have had many adventures since through our long friendship. Also while at Oxford, Jim Kennedy told me that if I was interested in hard-substrate fossils I should take the train to Aberystwyth, Wales, and see Tim Palmer (above on the right). I did and have enjoyed a long and deep friendship and collaboration with him ever since. I think the world of these gentlemen and am grateful for all that they’ve taught me and the many research opportunities I’ve had with them. We had a very special dinner of traditional Irish stews this evening in Ireland’s oldest pub, The Brazen Head (established in 1198 — and I didn’t reverse any digits).

The Annual Meeting of the Palaeontological Association has now ended. Tomorrow morning I leave Dublin for a brief visit to County Donegal in the far northwest of Ireland. I hope to make a blog post or two from there, but I’m not sure I’ll have an internet connection. If not, the next posts will come from home in about a week. Slán agaibh!

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Geological fieldwork on the streets of Dublin

Mark Wilson December 16, 2012 6:25 pm

DublinRainbow121612DUBLIN, IRELAND — What could be more Irish than a rainbow over Dublin? (I know better than to write of leprechauns and pots of gold.)  It certainly crowned the end of a delightful afternoon spent with my friend Tim Palmer looking at building stones.

I am in Dublin attending the annual meeting of the Palaeontological Association. After a long editorial meeting, Tim and I went to the center of the city to look for a particular kind of stone that may have been used in the Medieval portions of the two Dublin cathedrals: St. Patrick’s (National Cathedral of the Church of Ireland) and Christ Church (also for the Church of Ireland but claimed by Roman Catholics — it’s confusing, especially since they are only a short walk from each other). Tim was looking for a limestone called Dundry Stone, part of the Inferior Oolite (Middle Jurassic) in Great Britain. It is notable as a non-oolitic part of the Inferior Oolite, made mostly of tiny fragments of crinoids and calcite cement. Tim quickly found the stone in both cathedrals.

StPatricks121612This is St. Patrick’s Cathedral. Its exterior is mostly restored, but the interior still retains part of its Medieval core. It dates back to 1191.

StPatricksChapelDoorway121612We asked at the door to see the oldest part of St. Patrick’s, and were immediately directed to this small chapel. At the time the cathedral was filling with people for a choir concert, so we were surrounded with the sounds of bells and children practicing their pieces. This chapel was used as a storeroom as well as a tourist site, so there are some incongruities (such as the folding chairs!). Almost all the stone is either covered with cement or replacements except in a few places, like the frame of this small doorway. That white rock is Dundry stone.

ChristChurchCathedral121612This is Christ Church Cathedral, just down the road from St. Patrick’s. (A rivalry between the two dates back to the 12th Century. Two cathedrals in one city is very rare, apparently.) Christ Church is the older of the two cathedrals, dating back to about 1040 when a Viking king of Dublin started construction. It also has a mostly restored exterior, and it too has Dundry stone making up surviving doorways and lintels.

ChapterHouse121612This is an excavated “Chapter House” just outside Christ Cathedral on the grounds. Tim Palmer can be seen in the corner making notes. Apparently monks, priests and other church notables would meet in this building and sit on the stone benches just like Tim. The stones in this ruin include original materials (like the Dundry) and a variety of other lithologies.

I had a great time learning about stonework, Medieval building techniques, and the various structural properties of limestones, all thanks to Tim. Tomorrow I’ll be back in the more secular pews of the paleontological meeting. I’m happy to have had this spot of unexpected fieldwork!

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

Mark Wilson December 16, 2012 1:35 am

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.

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Wooster Geologist in Ireland

Mark Wilson December 15, 2012 7:28 am

IrishFlag121512DUBLIN, IRELAND — In a very quick transition from grading final exams in Wooster yesterday morning, I find myself now in downtown Dublin. I flew in last night to attend the 56th Annual Meeting of the Paleontological Association. I’ve been a member of this wonderful organization since 1985 — in fact, I’m one of the North American Representatives — and I love my rare visits to the main meetings. They are held throughout Europe to recognize the international base of the Palaeontological Association, with an emphasis on its European core. I am here representing the Paleontological Society in my role as Secretary. I am looking forward to meetings with my paleontologist colleagues, and to learning more about our craft and passion.

DublinPostOffice121512Since my first meeting is tomorrow morning, I spent some time looking at some of the historical places in the Dublin City Centre. Most impressive to me is the evocative Post Office, site of the failed Easter Rising by Irish nationalists in 1916. Above is the post office today. Below is the burned-out shell after the 1916 battle with British troops. Bullet scars are still visible in the stonework.

Dublin_Post_Office_1916

FourCourts121512The Four Courts, Ireland’s main court complex. The original structure was built in the 18th Century. The River Liffey is in the foreground.

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

Mark Wilson December 9, 2012 1:34 am

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.

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