Wooster’s Fossil of the Week: Star-shaped crinoid columnals from the Middle Jurassic of southern Utah

February 27th, 2015

Isocrinus nicoleti Kane County 585Just a quick Fossil of the Week post. Above we see isolated columnals (stem units) of the crinoid Isocrinus nicoleti (Desor, 1845) found in the Co-Op Creek Member of the Carmel Formation (Middle Jurassic), Kane County, southern Utah. Greg Wiles recently received them as part of a donation to our department collections. They have such perfect star shapes that I had to share them here. For the full analysis, see my previous entry on columnals like these preserved in a limestone from the same location.

References:

Baumiller, T.K., Llewellyn, G., Messing, C.G. and Ausich, W.I. 1995. Taphonomy of isocrinid stalks: influence of decay and autotomy. Palaios 10: 87-95.

Tang, C.M., Bottjer, D.J. and Simms, M.J. 2000. Stalked crinoids from a Jurassic tidal deposit in western North America. Lethaia 33: 46-54.

Wooster’s Fossil of the Week: A molded brachiopod from the Lower Carboniferous of Ohio

February 20th, 2015

Syringothyris bored Wooster CarboniferousWe haven’t had a local fossil featured on this blog for awhile. Above is an external mold of the spiriferid brachiopod Syringothyris typa Winchell, 1863, from the Logan Formation (Lower Carboniferous, Osagean, about 345 million years old) of southeastern Wooster, Ohio. The outcrop is along the onramp from north Route 83 to east Route 30. Older Wooster geologists may remember this area was called “Little Arizona” because of the large roadcuts made for a highway bypass that was never completed. That original outcrop was destroyed several years ago, but the same rocks are exposed in this new section. This is the area where Heather Hunt (’09) did her Senior Independent Study work, and long before her Brad Leach (’83) worked with the same fossils.

The Logan Formation is primarily fine sandstone, with some subordinate conglomerates, silts and shales. It was likely deposited in the proximal portion of a prodelta at or below wavebase. The fossils in the Logan are mostly these large Syringothyris and the bivalve Aviculopecten, along with scattered crinoids, gastropods, bryozoans, nautiloids and ammonoids. This fauna needs more attention. Funny how the fossils in your own backyard are so often ignored.

This brachiopod was first buried in sediment and then the shell dissolved away, leaving an impression behind. Since it is an impression of the exterior of the shell, it is called an external mold. Curiously, all the external molds (and the internal molds as well) in the local Logan Formation have an iron-rich, burnt orange coating much finer than the fine sand matrix. This means that details are preserved that are of higher resolution than the matrix alone would allow. In the case of this fossil, that coating extended down into long, narrow borings in the shell, casting them (see below).
Syringothyris borings 585These borings are odd. Most of them are parallel to the ribs (plicae) of the brachiopod, and appear to have been excavated from the shell periphery towards its apex. This was in the opposite direction of brachiopod shell growth. I suspect they were made by boring annelid worms that started at the growing edge of the shell where the mantle ended. These traces need attention, like most other aspects of this local fossil fauna.

References:

Ausich, W.I., Kammer, T.W. and Lane, N.G. 1979. Fossil communities of the Borden (Mississippian) delta in Indiana and northern Kentucky. Journal of Paleontology 53: 1182-1196.

Bork, K.B. and Malcuit, R.J. 1979. Paleoenvironments of the Cuyahoga and Logan formations (Mississippian) of central Ohio. Geological Society of America Bulletin 90 (12 Part II): 1782-1838.

Leach, B.R. and Wilson, M.A. 1983. Statistical analysis of paleocommunities from the Logan Formation (Lower Mississippian) in Wayne County, Ohio. The Ohio Journal of Science 83: 26.

Wooster’s Fossil of the Week: Sponge and bivalve borings from the Miocene of Spain

February 13th, 2015

Miocene Bored Cobble OutsideThis week we have a rather unimposing limestone cobble, at least from the outside. It was collected way back in 1989 by my student Genga Thavi (“Devi”) Nadaraju (’90) as part of a Keck Geology Consortium field project in southeastern Spain. It comes from the Los Banós Formation (Upper Miocene) exposed near the town of Abanilla. The holes are borings excavated into the carbonate matrix by marine animals. This cobble was tossed about in a coral reef complex that was part of the ancient Fortuna Basin.
Miocene Bored Cobble CutSeeing the cobble in cross-section makes it much more interesting. (Geologists love their rock saws!) We now see two categories of borings: one is large and flask-shaped, and the other a small network of spherical cavities. The large borings were produced by bivalves that tunneled into the limestone to make living chambers (domichnia) from which they could filter-feed. As the bivalve grew, the hole became deeper and wider. There was no escape — making and living in a boring like this is a lifetime occupation. These bivalve borings are classified as the trace fossil Gastrochaenolites lapidicus Kelly and Bromley, 1984. The smaller borings were made by clionaid demosponges that used acid to create a series of connected chambers, also for filter-feeding. These sponges could only penetrate about ten mm or so before their filtering became ineffective, so they are confined to the outer periphery of the cobble. The sponge borings are given the trace fossil ichnogenus Entobia Bronn, 1837.

On the inside surface of the largest boring (right side), encrusting tubes of a serpulid worm are just visible. This serpulid was also a filter-feeder. It took advantage of the cozy hole after the bivalve borer died and decayed. It is called a coelobite, or cavity-dweller. Serpulids would have had a rough time cementing to the outside of the cobble as it rolled around in this high-energy environment.

References:

Bronn, H.G. 1834-1838. Lethaea Geognostica (2 vols., Stuttgart).

Kelly, S.R.A. and Bromley, R.G. 1984. Ichnological nomenclature of clavate borings. Palaeontology 27: 793-807.

Mankiewicz, C. 1995. Response of reef growth to sea-level changes (late Miocene, Fortuna Basin, southeastern Spain). Palaios 10: 322-336.

Mankiewicz, C. 1996. The middle to upper Miocene carbonate complex of Níjar, Almería Province, southeastern Spain, in Franseen, E.K., Esteban, M., Ward, W.C., and Rouchy, J.-M., eds., Models for carbonate stratigraphy from Miocene reef complexes of the Mediterranean regions: Tulsa, SEPM (Society for Sedimentary Geology), p. 141-157.

Nadaraju, G.T. 1990. Borings associated with a Miocene coral reef complex, Fortuna basin, southeastern Spain. Third Keck Research Symposium in Geology (Smith College), p. 165-168.

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

Wooster’s Fossil of the Week: A Pleistocene octocoral holdfast from Sicily

February 6th, 2015

OctocoralHoldfastPleistoceneSicilyMy Italian colleague Agostina Vertino collected this beautiful specimen from the Pleistocene of Sicily and brought it to Wooster when she visited five years ago. It is the attaching base (holdfast) of the octocoral Keratoisis peloritana (Sequenza 1864). Octocorals (Subclass Octocorallia of the Class Anthozoa) are sometimes called “soft corals” because of their organic-rich, flexible skeletons. They are distinguished by polyps with eight tentacles, each of which is pinnate (feathery). Octocorals include beautiful sea fans and sea whips that require a hard substrate for stability. This particular holdfast is on a small slab of limestone.

The genus Keratoisis is known as the “bamboo coral” because it looks jointed like stalks of the plant. I collected fragments of Pleistocene Keratoisis branches during my visit to Sicily last year.
Giuseppe SeguenzaGiuseppe Seguenza (1833-1889) named the species Keratoisis peloritana. He was a Sicilian natural historian with broad interests, especially in geology. Although educated as a pharmacist, he found geology much more exciting on the volcanically active islands of the Mediterranean. He eventually became a professor of geology at the University of Messina (where the bust of him shown above resides). Italian sources say Seguenza received the famous Wollaston Medal from the Geological Society of London, but that does not appear to be true. Instead it appears that he was given “the balance of the proceeds of the Wollaston Fund” as a donation at the time the medal was awarded to Thomas Huxley (in 1876). The records of the society say that “the stipend of an Italian professor was too small to enable him to prosecute his palaeontological researches as fully as he could desire” (Woodward, 1876). Giuseppe Seguenza died in Messina at 56 years old.

References:

Di Geronimo, I., Messina, C., Rosso, A., Sanfilippo, R., Sciuto, F., and Vertino, A. 2005. Enhanced biodiversity in the deep: Early Pleistocene coral communities from southern Italy. In: Cold-Water Corals and Ecosystems, p. 61-86. Springer: Berlin, Heidelberg.

Fois, E. 1990. Stratigraphy and palaeogeography of the Capo Milazzo area (NE Sicily, Italy): clues to the evolution of the southern margin of the Tyrrhenian Basin during the Neogene. Palaeogeography, Palaeoclimatology, Palaeoecology 78: 87-108.

Langer M. 1989. The holdfast internodes and sclerites of Keratoisis melitensis Goldfuss 1826 Octocorallia in the Pliocene foraminifera marl Trubi of Milazzo Sicily Italy. Palaeontologische Zeitschrift 63: 15-24.

Woodward, H. 1876. Reports and proceedings, Geological Society of London. Geological Magazine 13: 181-182.

Wooster’s Fossil of the Week: A stromatoporoid from the Silurian of Estonia

January 30th, 2015

Densastroma pexisumStromatoporoids are extinct sponges that formed thick, laminated skeletons of calcite. They can be very common in Silurian and Devonian carbonate units, sometimes forming extensive reefs. The stromatoporoid above is Densastroma pexisum (Yavorsky, 1929) collected from the Mustjala Member of the Jaani Formation (Silurian, Wenlock) exposed on Saaremaa Island, Estonia. It was part of Rob McConnell’s excellent Senior Independent Study he completed in 2010.
Densastroma pexisum sectionStromatoporoids are rather featureless lumps until you cut a section through them. Then you see their characteristic laminae of calcite. Looking very close you might also glimpse the tiny vertical pillars between the laminae. Identifying the species of stromatoporoid always involves a thin-section or acetate peel to discern the forms of the pillars and laminae.

In the upper left of the sectioned D. pexisum is an oval boring cut through the fabric of the stromatoporoid. This is likely the trace fossil Osprioneides kampto Beuck and Wisshak, 2008. This is the largest known Palaeozoic boring. It is relatively common in Silurian stromatoporoids of the Baltic region. Last year Olev Vinn, Mari-Ann Mõtus and I published a paper describing the same ichnospecies in large trepostome bryozoans from the Estonian Ordovician.
8 schematic drawing of Osprioneides kampto
This diagram of O. kampto is from Figure 8 of the Beuck et al. (2008) paper. The organism that made the boring was almost certainly a filter-feeding worm of some kind that gained a feeding advantage by placing itself high on a hard substrate.
Flügel in 7000 ts by Chris SchulbertDensastroma was originally named in 1958 by Erik Flügel (1934-2004). He combined the Latin densus with the Greek stroma, meaning “dense-layered”. (Yes, taxonomic purists will object to the mix of Latin and Greek in one name.) Flügel was a highly accomplished and diverse scientist who founded the Institute of Paleontology at the University of Erlangen-Nuremberg as well as the journal Facies. He is best known for his advocacy of detailed study of carbonate facies through petrography (“microfacies analysis“), developing a series of techniques and principles that I found very useful in my dissertation work. The above image is a fitting tribute to Erik Flügel made by Chris Schulbert. It is a portrait made of 7000 carbonate thin-sections!

References:

Beuck, L., Wisshak, M., Munnecke, A. and Freiwald, A. 2008. A giant boring in a Silurian stromatoporoid analysed by computer tomography. Acta Palaeontologica Polonica 53: 149-160.

Flügel, E. 1959. Die Gattung Actinostroma Nicholson und ihre Arten (Stromatoporoidea). Annalen des Naturhistorischen Museums in Wien 63: 90-273.

Freiwald, A. 2004. Erik Flügel: 1934–2004. Facies 50: 149-159.

Vinn, O., Wilson, M.A. and Mõtus, M.-A. 2014. The earliest giant Osprioneides borings from the Sandbian (Late Ordovician) of Estonia. PLoS ONE 9(6): e99455. doi:10.1371/journal.pone.0099455.

Wooster’s Fossil of the Week: A predatory gastropod from the Pliocene of Cyprus

January 23rd, 2015

Naticarius millepunctatus Pliocene CyprusThis week we have another fossil from the Nicosia Formation (Pliocene) of the Mesaoria Plain in central Cyprus. It is again from a Keck Geology Consortium project in 1996 with Steve Dornbos (’97). This time, though, instead of our Coral Reef locality, our featured creature is from a sandy marl outcrop we called “Exploration”. We have above an aperture view of Naticarius millepunctatus Risso, 1826, a species still alive today and known as the “many-spotted moon shell”. It is a naticid gastropod, heir to a predatory tradition that strikes fear in the tiny hearts of bivalves.
Naticarius millepunctatus Pliocene Cyprus View 2Naticid gastropods, like our Naticarius, have a well-muscled foot that they use to essentially swim through loose sand to capture infaunal bivalves and other shelled prey. They then use their specialized radula to drill into the shell, kill the unfortunate animal, and then consume the soft goodies. Naticids leave distinct drill holes in the shells of their victims, as shown in a previous Fossil of the Week post. We found a few drilled bivalve shells with our Naticarius millepunctatus at the Exploration site.
André_Marie_Constant_DumérilNaticarius was named as a genus in 1806 by André Marie Constant Duméril (1774-1860). Duméril was another member of that marvelous group of French zoologists that lived through the French Revolution. He was a professor of anatomy, herpetology and ichthyology at the Muséum National d’Histoire Naturelle in Paris, corresponding and collaborating with such eminents as Georges Cuvier and Alexandre Brongniart. His most prominent work was Zoologie analytique, published in 1806. In this massive treatise he compiled descriptions of all the known genera of animals in an effort to sort them out in a repeatable way.
Dumeril KeyThis is a page from Duméril’s Zoologie analytique. We immediately recognize this as a binary taxonomic key, even if we can’t read the French. Starting from the left we make yes or no decisions about the anatomy of the animal we’re trying to identify, eventually ending on the right with a genus. (Naticarius is at number 10.)

André Marie Constant Duméril did prodigious work with reptiles as well, describing in detail 1393 “species” over nine volumes. (Oddly, in defiance of his fellow zoologists, he insisted that amphibians should be counted among the reptiles, thus the quotes around his number of “reptiles”.) Duméril also had major works on insects. His son, Auguste Duméril, was also a zoologist. As the elder Duméril retired, Auguste gradually took over his scientific projects.

References:

Cowper Reed, F.R. 1935. LII.—Notes on the Neogene Faunas of Cyprus.—III. The Pliocene Faunas. Journal of Natural History 16: 489-524.

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.

Duméril, C. 1806. Zoologie analytique, ou Méthode naturelle de classification des animaux, rendue plus facile à l’aide de tableaux synoptiques. Allais, Paris. 344 pp.

Tyler, C.L. and Schiffbauer, J.D. 2012. The fidelity of microstructural drilling predation traces to gastropod radula morphology: paleoecological applications. Palaios 27: 658–666.

Wooster’s Fossil of the Week: Another vermetid gastropod from the Pliocene of Cyprus

January 16th, 2015

Petaloconchus intortus (Lamarck, 1818)Why another one of those strange twisty gastropods from the Pliocene of Cyprus for our Fossil of the Week? Because this one fooled me for years. Above is a pair of images of a specimen of the vermetid gastropod Petaloconchus intortus (Lamarck, 1818) from the Nicosia Formation (Pliocene) of central Cyprus. It is encrusting a branch of the coral Cladocora. Ever since 1996 I’ve cataloged this and other such Cypriot specimens as serpulids, a type of polychaete worm that constructs adherent calcareous tubes like these. In fact, I placed on Wikipedia an image of the specimen below as a serpulid example.
Petaloconchus Cyprus Pliocene 585Last week an anonymous editor on Wikipedia changed the caption on my image from “serpulid worm tube” to “Petaloconchus“. I did some research and yes, he or she was correct. I’ve since remade the image and updated all the Wikipedia pages where it appeared. This is not the first time I’ve posted a fossil image online and been corrected, and I hope it’s not the last. Such feedback and criticism is a major advantage of online science, and I learn a great deal.

In my research on Petaloconchus, I found a delightful Journal of Paleontology paper by Stephen Jay Gould in which he defines a new subspecies of Petaloconchus sculpturatus and discusses the genus and its evolution in classic Gouldian ways (Gould, 1994). He, for example, found this quote by Myra Keen (1961, p. 183):

The Vermetidae (worm gastropods) probably hold a record among molluscs for the degree of confusion they have promoted, both in collections, and in the literature; for they have been misconstrued at every level from subspecies to phylum.

I’m happy to see I’m not the only one who has had trouble with vermetid gastropods. Even in Gould’s (1994, p. 1035) taxonomy of his new subspecies we see some of the issues with Petaloconchus:

Etymology.–alaminatus to recognize key feature of the absent internal laminae. The Linnean name is a paradox, as Petaloconchus means laminate shell (the supposed, but inadequate, definition of the genus), while the subspecific name alaminatus negates this characteristic feature. But who ever denied either nature’s complexity or evolution’s capacity to eliminate structures?

HCLeaPetaloconchus was named in 1843 by Henry Charles Lea (1825-1909), an American historian and political activist — an unexpected description of someone who named a snail. Lea came from a family deeply embedded in early American politics, and his father, Isaac Lea (1792-1886) was a prominent naturalist. Henry was clearly a prodigy in many endeavors. Note that his paper describing Petaloconchus and other fossils was completed when he was just 18 years old. In 1847, as a young man of 22, he suffered a mysterious nervous breakdown. During his long convalescence he read French medieval history, which turned his interests to the humanities. He eventually became a renowned historian of the Spanish Inquisition. (No one expects the Spanish Inquisition.)
LeaPetaloconchusOriginal image of Petaloconchus sculpturatus by Lea (1843).

Serpulids Cyprus PlioceneAbove are some real serpulid worm tubes from the Pliocene of Cyprus, although I’m open to corrections!

References:

Aguirre, J., Belaústegui, Z., Domènech, R., de Gibert, J.M., and Martinell, J. 2014. Snapshot of a lower Pliocene Dendropoma reef from Sant Onofre (Baix Ebre Basin, Tarragona, NE Spain). Palaeogeography, Palaeoclimatology, Palaeoecology 395: 9-20.

Bradley, E.S. 1931. Henry Charles Lea. A Biography. Philadelphia, University of Pennsylvania Press, 418 pages.

Carpenter P. 1857. First steps toward a monograph of the recent species of Petaloconchus, a genus of Vermetidae. Proceedings of the Zoological Society of London 24: 313-317.

Gould, S.J. 1994. Petaloconchus sculpturatus alaminatus, a new Pliocene subspecies of vermetid gastropods lacking its defining generic character, with comments on vermetid systematics in general. Journal of Paleontology 68: 1025-1036.

Keen, A.M. 1961. A proposed reclassification of the gastropod family Vermetidae. Bulletin of the British Museum (Natural History), Zoology, 7:183-213.

Lea, H.C. 1843. Descriptions of some new fossil shells, from the Tertiary of Petersburg, Virginia. Transactions of the American Philosophical Society 9: 229-274. [The volume was actually published in 1846.]

Wooster’s Fossil of the Week: A worm-like gastropod from the Pliocene of Cyprus

January 9th, 2015

Vermetus Pliocene Cyprus aperture viewThis week we continue with fossils from the Nicosia Formation (Pliocene) of the Mesaoria Plain in central Cyprus. These fossils are from a Keck Geology Consortium project in 1996 with Steve Dornbos (’97). Above we have one of the most distinctive forms at the Coral Reef locality: the gastropod Vermetus Daudin, 1800. It doesn’t look much like a snail with its irregular, twisty tube of a shell, but the animal within was very snaily indeed.
Vermetus Pliocene CyprusVermetus and its relatives are still alive today, so we know a lot about their biology. They are sessile benthic, cemented, filter-feeding marine organisms, meaning they are stationary on some hard oceanic substrate sorting out organic materials from the water. They gather their food in one of two ways: capturing plankton in their gills (much like most bivalves) or making a net of mucus threads that is gathered occasionally with their radulae, with the food passed to the mouth. They have separate sexes. The male broadcasts sperm into the water column. The female catches some of this sperm in her mucus feeding net. She then broods the fertilized eggs in her mantle cavity. Vermetids are common enough that they are even used today to determine tectonic movements in the Mediterranean (Sivan et al., 2010).

The genus Vermetus was named in 1800 by François Marie Daudin (1774-1804). Daudin was a French zoologist with a hard, short but very productive life. He contracted a disease in childhood that left his legs paralyzed, and thereafter devoted his time to natural history. He started (but did not complete) one of the first modern books on ornithology, combining description with Linnean taxonomy. His work on amphibians and reptiles was epic, finishing eight volumes that described 517 species. In all his research he was helped by his wife Adèle, who drew his hundreds of illustrations, including those below. She died of tuberculosis in 1804, and he died soon after only 29 years old. They both lived in poverty in Paris during the dislocations of the French Revolution.
Screen Shot 2014-12-31There are no portraits of François Marie Daudin, so the best I can do in his memory is reproduce some of the illustrations of modern Vermetus (drawn by Adèle Daudin) in his 1800 book titled (in translation) “Collection of memories and notes on new or little-known species of molluscs, worms and zoophytes”. Here’s to our memory of the Daudins.

References:

Cowper Reed, F.R. 1935. LII.—Notes on the Neogene Faunas of Cyprus.—III. The Pliocene Faunas. Journal of Natural History 16: 489-524.

Daudin, F.M. 1800. Recueil de Mémoires et de Notes sur des espèces inédites ou peu connues de Mollusques, de Vers et de Zoophytes, orné de gravures. Chez Fuchs, Libraire, rue des Mathurins. Treuttel et Wurtz, quai Voltaire; 50 pp.

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.

Sivan, D., Schattner, U., Morhange, C. and Boaretto, E. 2010. What can a sessile mollusk tell about neotectonics? Earth and Planetary Science Letters 296: 451-458.

Wooster’s Fossil of the Week: An encrusted scallop from the Pliocene of Cyprus

January 2nd, 2015

Chlamys Pliocene CyprusOne of the very best paleontological sites I had the pleasure of collecting was on the hot Mesaoria Plain near the center of the island of Cyprus. It was the summer of 1996 and Steve Dornbos (’97) and I were pursuing research as part of a Keck Geology Consortium project. We were exploring the Nicosia Formation, a Pliocene series of thick marls with occasional fossiliferous beds. We stumbled across a remarkable fossil coral reef preserved in a hillside. This deposit and its fossils became the basis of Steve’s Independent Study project and a paper (Dornbos and Wilson, 1999). One of the most prominent (and beautiful) fossil types we found was the pectinid clam Chlamys. The specimen above fell into our category of “Chlamys sp. 1″ because we couldn’t further identify it. Note that it has near the hinge on the left a juvenile Chlamys attached to it, as well as a circular serpulid tube near the top center. The details of the shell are very well preserved.
Chlamys interior Pliocene CyprusThis is the interior view of the same specimen of Chlamys. Visible at the hinge is the isodont dentition and, extending to the left, the distinctive auricle of the genus. On the right side of the hinge is a bit of the young Chlamys.

This species of Chlamys likely nestled between the branches of the coral in our reef, opening its valves to filter-feed. It was not a swimmer like some of its thin-valved, symmetrical pectinid cousins living in the same reef.
Peter Friedrich RödingChlamys was named in 1798 by Peter Friedrich Röding (1767–1846), a German naturalist who lived in Hamburg. He chose the name from the Greek chlamys (χλαμύς) because he thought it looked like the folds of this ancient Greek cloak. In 1798 Röding published a sale catalogue of mollusk shells (fossil and modern). The descriptions of specimens were minimal, but he had long lists of new taxonomic names, making him the official author of dozens of molluscan genera. Strangely, Röding didn’t put his name on the catalogue. He was only officially recognized as its author by a ruling of the International Commission on Zoological Nomenclature in 1956, thus ensuring the perpetuation of his name in our taxonomic system.

We’ll see more gorgeous fossils from the Pliocene of Cyprus in the coming weeks.

Wooster’s Fossil of the Week feature is four years old today. There have been 208 posts in this series, starting with the first posted on January 2, 2011. I hope there are many more to come!

References:

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.

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.

Wooster’s Fossil of the Week: A Cretaceous oyster with borings and bryozoans from Mississippi

December 26th, 2014

Exogyra costata Prairie Bluff Fm Maastrichtian 585
As winter closes in on Ohio, I start dreaming about past field trips in warm places. This week’s fossil takes me back to fieldwork in Alabama and Mississippi during May of 2010. Paul Taylor (The Natural History Museum, London) and I studied the Upper Cretaceous and Lower Paleogene sections there with our students Caroline Sogot and Megan Innis (Wooster ’11). We had a most excellent and productive time.

The above fossil was very common in our Maastrichtian (Upper Cretaceous) outcrops. It is a left valve of Exogyra costata Say, 1820, from the Prairie Bluff Chalk Formation exposed in Starkville, Mississippi (locality C/W-395). It is a large oyster with a very thick calcitic shell. It has a distinctive spiral, making it look a bit like a snail. Oysters are sessile benthic filter-feeders that usually sit on their large left valves with a flatter and smaller right valve on top. Exogyra stayed stable on the seafloor because of its massive weight.
Interior left 111914This is a view of the inside of the left valve at the top of this entry. You can see the large, dark adductor muscle scar in the center. (The adductors closed the valves.) Note the many evenly-spaced holes in the oyster shell interior, with a closer view below.
Entobia 111914These holes were excavated by a clionaid sponge, producing the trace fossil Entobia. The sponge used the oyster shell as a protective substrate. It infested the valve after the death of the oyster made that particular piece of hard real estate available.
Interior close view 111914In the very center are some tiny encrusting cyclostome cheilostome bryozoans. Caroline, Paul and Liz Harper studied encrusting bryozoans like these from this field area as part of biogeographical and paleoecological investigation of the Cretaceous extinctions (see Sogot et al., 2013). I imagine Paul can even identify this species shown here. I wouldn’t dare! [Update from Paul: “I think these examples are cheilostomes, quite possibly Tricephalopora …” See comments.]
Thomas_Say_1818The genus Exogyra, along with the species E. costata, was named by Thomas Say (1787-1834) in 1820 (pictured above in 1818). Say was a brilliant American natural historian. Among his many accomplishments in his short career, in 1812 he helped found the Academy of Natural Sciences of Philadelphia, the oldest natural science research institution and museum in the New World. He is best known for his descriptive entomology in the new United States, becoming one of the country’s best known taxonomists. he was the zoologists on two famous expeditions led by Major Stephen Harriman Long. The first, in 1819-1820, was to the Great Plains and Rocky Mountains; the other (in 1823) was to the headwaters of the Mississippi. Along with his passion for insects, Say also studied mollusk shells, both recent and fossil. He was a bit of an ascetic, moving to the utopian socialist New Harmony Settlement in Indiana for the last eight years of his life. It is said his simple habits and refusal to earn money caused problems for his family. Say succumbed to what appeared to by typhoid fever when he was just 47.

References:

Harris, G.D. 1896. A reprint of the paleontological writings of Thomas Say. Bulletins of American Paleontology, v. 1, number 5, 84 pp.

Say, T.G., 1820. Observations on some species of Zoophytes, shells, etc., principally fossils. American Journal of Science, 1st series, vol. 2, p. 34-45.

Sogot, C.E., Harper, E.M. and Taylor, P.D. 2013. Biogeographical and ecological patterns in bryozoans across the Cretaceous-Paleogene boundary: Implications for the phytoplankton collapse hypothesis. Geology 41, 631-634.

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