Wooster’s Fossil of the Week: A terebratulid brachiopod from the Miocene of Spain

September 29th, 2013

Terebratula maugerii Boni, 1933_585These large brachiopods are of the species Terebratula maugerii Boni, 1933. They were found in Upper Miocene (Tortonian-Messinian) beds near Cordoba, Spain. Wooster acquired them through a generous exchange of brachiopods with Mr. Clive Champion in England.

The specimen on the left is oriented with the dorsal valve upwards. The ventral valve is below and visible at the top of the image. The ventral valve of terebratulids has a rounded opening through which the attaching device, called the pedicle, extended. The specimen on the right is shown with its ventral valve upwards. Since this is the largest valve, you can’t see the dorsal valve below.

I like these specimens because they have that beautiful fold in the center of the shell. This is much more pronounced than in the usual terebratulid brachiopod (it is said to be “strongly plicated“), so students get to see some variety in this large but generally uniform group.

By the Cenozoic, brachiopods are rather rare in fossiliferous deposits. Shelly beds from the Paleocene on are dominated by mollusks, especially bivalves. This large brachiopod, though, is an exception found in the Upper Miocene shellbeds of southern Spain. It is found in meter-thick accumulations, making it for a very short time a significant carbonate component in marine sediments. Terebratula maugerii was most common in the deep subtidal in high-energy deposits. (See Reolid et al., 2012, for details.)
RomanLampFinally, brachiopods are commonly called “lamp shells“, which makes no sense to most modern students. They were given this nickname way back in the 18th century because of their resemblance to Roman oil lamps, such as those figured above in the same orientation as our shells. These were filled with oil through the central hole and a wick was placed in what we now see as the “pedicle opening”. It is an archaic comparison, but it works!

References:

Boni, A. 1933. Fossili miocenici del Monte Vallassa. Bolletino della Società Geologica Italiana 52: 73-156.

García Ramos, D.A. 2006. Nota sobre Terebratulinae del Terciario de Europa y su relación con los representantes neógenos del sureste español. Boletín de la Asociación Cultural Paleontológica Murciana 5: 23-83.

Llompart, C. and Calzada, S. 1982. Braquio ́podos messinienses de la isla de Menorca. Bol R Soc Espanola Hist Nat 80: 185–206.

Reolid, M., García-García, F., Tomasovych, A. and Soria, J.M. 2012. Thick brachiopod shell concentrations from prodelta and siliciclastic ramp in a Tortonian Atlantic–Mediterranean strait (Miocene, Guadix Basin, southern Spain). Facies 58: 549-571.

Toscano-Grande, A., García-Ramos, D., Ruiz-Muñoz, F., González-Regalado, M.L., Abad, M., Civis-Llovera, J., González-Delgado, J.A., Rico-García, A., Martínez-Chacón, M.L., García, E.X. and Pendón-Martín, J.G. 2010. Braquiópodos neógenos del suroeste de la depresión del Guadalquivir (sur de España). Revista Mexicana de Ciencias Geológicas 27: 254-263.

Wooster’s Fossil of the Week: A delicate brachiopod from the Pliocene of Cyprus

September 22nd, 2013

Terebratulid Pliocene CyprusThese thin-shelled brachiopods were collected in the summer of 1996 on a Keck Geology Consortium project in Cyprus. Strangely enough, they were the first brachiopods I had ever seen in the Cenozoic. These are ventral valves of the terebratulid Maltaia pajaudi García–Ramos, 2006. On the left is the external view, and on the right is the internal. In the internal view at the top (posterior) portion of the shell you can see the rounded pedicle opening and two teeth of the hinge mechanism that articulated the valves.

The fieldwork that summer was with three students: Steve Dornbos (’97) of Wooster, Ellen Avery of Bryn Mawr, and Lorraine Givens of SUNY-Buffalo State. We found hundreds of gorgeous fossils, many of which have been described in these webpages. All are from the Nicosia Formation (Pliocene) exposed on the Mesaoria Plain in the center of Cyprus near the village of Meniko. The brachiopods above were found at a site we termed “Pelican-Brachiopod” that had 37 different fossil species. It was an unusual paleocommunity with large numbers of predatory gastropods, many of which left their marks as boreholes in shells. We figured from the microfossils present, as well as the fine silty sediment, that this fauna lived in relatively deep waters, probably several hundred meters. We had other Nicosia Formation sites in very shallow waters (including a coral reef), so we were able to show considerable paleoenvironmental diversity in this thick unit.
G. Arthur Cooper and the "Emerald Queen"The Mediterranean brachiopod genus Maltaia was named in 1983 by the famous American paleontologist G. Arthur Cooper (1902-2000). I actually met the man in 1977 when I was an undergraduate attending the North American Paleontological Convention in Lawrence, Kansas. I was awestruck because he was legendary for his prodigious systematic work with brachiopods, especially those of the Permian in western Texas. The classic photo above shows him in the field with his Smithsonian Institution vehicle he named the “Emerald Queen”.

Cooper earned his B.S. degree at Colgate University with a chemistry major in 1924. He did his PhD work at Yale University with the epic paleontologists Carl O. Dunbar and Charles Schuchert, earning his degree in 1929. He loved brachiopods and was encouraged to pursue them by Schuchert. Cooper joined the paleontological staff at the United States National Museum in 1930, flourishing there through his retirement in 1974 into active emeritus status. He named hundreds of new fossil brachiopods during his career. I would not be surprised to hear he has the record of new fossil taxonomic descriptions. He was much honored in his time, including receipt of the second Paleontological Society medal in 1964.

References:

Bitner, M.A. and Martinell, J. 2001. Pliocene brachiopods from the Estepona Area (Málaga, South Spain). Revista Española de Paleontología 16: 177-185.

Bitner, M.A. and Moissette, P. 2003. Pliocene brachiopods from north-western Africa. Geodiversitas 25: 463-479.

Cooper, G.A. 1983. The Terebratulacea (Brachiopoda), Triassic to Recent: A study of the brachidia (loops). Smithsonian Contributions to Paleobiology 50: 1–445.

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.

Toscano-Grande, A., et al. 2010. Neogene brachiopods from the southwestern Guadalquivir basin (south Spain). Revista Mexicana de Ciencias Geologicas 27: 254-263.

A Wooster Geologist goes to Washington for a different kind of fieldwork

September 18th, 2013

1photo1_091813WASHINGTON, DC–Today I was in Washington, DC, with 70 other colleagues for the annual Geosciences Congressional Visits Day organized by the American Geosciences Institute (AGI). I was ostensibly representing the Paleontological Society as its secretary, but I was really a member of the Ohio delegation there to speak to staffers in the offices of Ohio senators and representatives. The weather was strikingly beautiful, and all the more lovely considering how much time I spent looking at it through windows in one office or another.

The AGI organized this set of visits with great precision. We were split into state teams (my partner was Pete MacKenzie of the Ohio Oil and Gas Association), each guided by a coordinator (we had Julie McClure, a science policy fellow). Our Ohio team went to the offices of Senators Rob Portman and Sherrod Brown, Congressmen James Renacci and Pat Tiberi, and then we met with a counsel for the Senate Energy and Natural Resources Committee. We had a few minutes in each office to make the case for “steady federal investments” in Earth and space sciences. It was a difficult “ask” because of the diversity of agencies and constituents, so I hope our enthusiasm at least left an impression. I am SO grateful to Pete and Julie for their experience and leadership in our little squad.

2photo9_091813This is a rotunda in the Russell Senate Office Building, with Pete Mackenzie serving as scale. This is a spot commonly used for television interviews of senators. The statue is of Senator Richard Russell himself.

3photo8_091813Literally one of the halls of Congress. This is again in the Russell Senate Office Building.

4photo6_091813We saw these clocks throughout the Russell Senate Office Building. The lights indicate the number of buzzers sounded to call senators to various votes and quorum calls. The red light means the Senate is in session.

5photo7_091813Yes, here is Country Mouse outside the office of his representative: James Renacci of the Ohio 16th District (“the fighting 16th!”). I felt casually dressed, and one staffer said I must be the professor with “that hair”. While I learned a lot, I can’t say I was comfortable with the process. I’m grateful for all the bright people who enjoy these things!

6photo2_091813OK, out of the offices in time for a little sight-seeing on the way back to the airport. Here is one of my favorite statues in the capitol: Nathan Hale. This tragic hero looks so much like a college student to me.

7photo5_091813You just have to love democracy in action at the heart of our government! This is just one example of the many temporary and permanent demonstrations going on in the capitol. I’ve resisted showing you the displays of the anti-circumcisionists!

8photo3_091813Finally, there must be a little geology here. This was the first time I’ve visited the extraordinary National Museum of the American Indian. Highly recommended, and the food court is to die for. The architecture is intended to resemble southwestern cliffs of sandstone with inset dwellings. I think it is a spectacular success.

9photo4_091813Some of the stone is set with the bedding planes facing outwards. Several trace fossils are visible. These were formed by worm-like animals burrowing through muds sandwiched between layers of sand. I wish I knew the age and location of this deposit.

My visit to Washington was an excellent experience and the basis for future such work with science policy issues. It was surprisingly easy to visit congressional offices, so one primary value of our trip was to show other scientists that their elected representatives are anxious to hear our opinions and use our knowledge and skills for crafting legislation. Of course, everyone we talked to was preoccupied by the latest political maneuvers associated with trying to pass a budget for the next fiscal year (good luck with that), but we were always listened to carefully and treated with respect.

You may also notice in the top photo that the flags are at half-staff on the capitol building. This is because on Monday, the first day of our training workshop, there was a mass shooting at the Navy Yard in DC. This tragedy was a shadow over us all, and it was a reminder of how important good governance is in an unpredictable world.

 

Wooster’s Fossils of the Week: An ancient predator/prey system from the Lower Pleistocene of Sicily

September 15th, 2013

Bored and Borer for FOTWThe above fossils were collected from a Lower Pleistocene silty marl exposed near the Megara archaeological site east of Augusta, Sicily, Italy. I was on that epic International Bryozoology Association field trip this summer I’ve been blogging about. The shells in this locality are very abundant with hundreds of species represented, from foraminiferans to shark teeth. I thought this little vignette of a predator and its typical prey was worth noting.

On the far right is a naticid gastropod (moon snail). These mollusks are predators who kill and consume their prey by drilling holes into their shells with a specialized radula (a kind of tooth-bearing “tongue”). Their holes are distinctively beveled, with a wider portion on the outside narrowing to a smaller inner opening. The three organisms on the left all show boreholes indicating that they were likely killed and eaten by a naticid.

Or at least that’s the traditional story. A paper came out this year (Gorzelak et al., 2013) comparing predatory drill holes in shells with holes produced by physical abrasion by experimental tumbling. The sizes, shapes and locations of these abrasion-produced holes are shockingly similar to those made by drilling predators. It looks like we must be careful which holes we assign to predation and which were produced by other means.

As I look at the three victims above, two of them (the high-spired turritellid gastropod on the far left and the bivalve second from the right) have nicely beveled holes with almost perfectly circular shapes. The gastropod shell that is second from the left, though, presents problems. First, it has two holes that completely penetrate the shell. Predators occasionally bore a shell twice, but not very often. Second the holes are more irregular in shape and don’t have a noticeable beveling. This could be a feature of the thinner shell of this gastropod not recording the usual naticid boring evidence, or it could be the result of physical abrasion and not predation. It is a difficult call but an important one to those plotting the evolution of this predator/prey system through time.

References:

Gorzelak, P., Salamon, M.A., Trzęsiok, D. and Niedźwiedzki, R. 2013. Drill holes and predation traces versus abrasion-induced artifacts revealed by tumbling experiments. PLoS ONE 8(3): e58528. doi:10.1371/journal.pone.0058528

Kelley, P.H. and Hansen, T.A. 2006. Comparisons of class- and lower taxon-level patterns in naticid gastropod predation, Cretaceous to Pleistocene of the US Coastal Plain. Palaeogeography, Palaeoclimatology, Palaeoecology 236: 302–320.

Kowalewski, M., Dulai, A. and Fürsich, F.T. 1998. A fossil record full of holes: The Phanerozoic history of drilling predation. Geology 26: 1091–1094.

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.

A paleontology field trip into the Upper Ordovician of Ohio

September 8th, 2013

DSC_2515The 2013 Invertebrate Paleontology class at Wooster had its first field trip today. The weather was absolutely perfect, and the usual boatload of fossils was collected. We traveled this year to Caesar Creek State Park and worked in the emergency spillway created and maintained by the US Army Corps of Engineers for the Caesar Creek Lake dam. Exposed here are the Arnheim, Waynesville, Liberty and Whitewater Formations of the Richmondian Stage in the Cincinnatian Series of the Ordovician System. These units are enormously rich with fossils, especially brachiopods, bryozoans, trilobites, clams, snails, nautiloids, corals and crinoids. There is no better place to get students started on paleontological fieldwork, and to follow up with lab preparation, identification and interpretation throughout the semester.

Spillway090813The Caesar Creek Lake emergency spillway is at N 39.480069°, W 84.056832° along Clarksville Road just south of the dam. The authorities keep it clear of vegetation, and so it is an extensive exposure of bare rock and sediment. The sharp southern boundary is the rock wall shown in the top image (with the intrepid Willy Nelson and Zach Downes). Students quickly fanned out along the entire exposure, so I never did get an image of the whole class of 22 students in one place.

DSC_2505This is the bedding plane of a slab of micritic limestone with numerous worm burrows. Trace fossils are very abundant here. These units, in fact, have some of the first trace fossils to be specifically described in North America.

DSC_2506On some limestone slabs are internal and external molds of straight orthocerid nautiloids. They are often paired like this, with both facing in the same direction. This is an effect of seafloor currents that oriented the shells. The current here was flowing from the left to the right.

DSC_2508Many of the limestones are extremely rich in shelly fossils. Here you can see several types of brachiopods, an isotelid trilobite genal spine, and some molluscan internal molds.

DSC_2511I always check in here with my favorite borings: Petroxestes pera. These are bivalve incisions on a cemented seafloor (a carbonate hardground). This is the type area for this ichnogenus and ichnospecies.

DSC_2512Two of our sophomore paleo students, Michael Williams and Adam Silverstein, are here happily filling their sample bags with fossils. I wanted to get a photo of them in the field because they had such a geologically adventurous summer in both cool and wet Iceland and hot, dry Utah. Not many sophomores have these opportunities!

DSC_2520Here is another pair of nautiloids, this time showing the characteristic internal mold features of curved septal walls. Again they are nestled together and oriented because of seafloor currents.

For the rest of the semester the paleo students will be studying the fossils they collected today, each eventually constructing a paleoecological interpretation based on their identifications and growing knowledge of marine invertebrate life habits and history. Now we’re really doing paleontology!

Wooster’s Fossil of the Week: A nautiloid from the Middle Jurassic of southern Israel

September 8th, 2013

Cymatonautilus_AThis is the first nautiloid specimen I’ve seen in the Matmor Formation (Middle Jurassic, Callovian) after ten years of collecting in it. Our colleague Yoav Avni (Geological Survey of Israel) picked it up during this summer’s fieldwork. It is a beautiful internal mold in which the outer shell has been mostly removed, revealing the radiating lines where the internal walls (septa) intersected the outer shell. These intersections are called sutures. Here we see nice, simple sutures characteristic of nautiloids. Ammonites, on the other hand, can have very complex sutures indeed. Note that some of the outer shell still remains as an orangish layer recrystallized to calcite from the original aragonite. There are two round holes in the foreground. I’d like to think these are tooth marks from a predator, but there is not enough evidence to say that with any seriousness.
Cymatonautilus072913_BThis view of the outer edge of the top specimen shows a diagnostic feature of this particular genus: a deep sulcus (channel) running along the venter (periphery). Most nautiloids have a rounded venter, so this characteristic stands out.
Cymatonautilus072913_CThis is a side view of another specimen of the same nautiloid, also found by Yoav. The large hole at the center of coiling is called the umbilicus. It is especially large in this Matmor nautiloid. Note again the radiating sutures where the outer wall has been removed.

This nautiloid appears to belong to the genus Paracenoceras Spath 1927. I had to have this beaten into me by a half-dozen cephalopod workers. I thought it looked a lot like Cymatonautilus collignoni Tintant, 1969. If so, it would have been a new occurrence of this rare genus — the closest it has previously been found is in Saudi Arabia. Most importantly, it would have been a range extension for this genus. Previously it has been well documented as having appeared in a very short time interval: the latest early Callovian into the middle Callovian. In the Matmor Formation we found it in a bed in the upper Callovian, specifically subunit 52 in the Quenstedtoceras (Lamberticeras) lamberti Zone. Alas, my dreams of a paper describing this discovery was not to be. Another beautiful idea skewered by reality.

Paracenoceras was described by Leonard Frank Spath (1882-1957) in 1927. Spath was an interesting character. He was a British paleontologist who specialized in ammonites, but also delved into other cephalopods like our nautiloid genus here. He was a BSc graduate of Birkbeck College in 1912, eventually earning a doctorate at the same institution, now known as Birkbeck, University of London. He was a curator in the British Museum (Natural History) for most of his career. He was especially interested precise Jurassic and Cretaceous biostratigraphy using ammonites. He published more than 100 papers and monographs, was elected as a Fellow of the Royal Society, and received the Lyell Medal from the Geological Society of London in 1945. Spath was well known for his biting criticisms of German paleontologists, especially those who worked on ammonites. Turns out that he was keeping a secret from everyone, including his own children: his parents were German! His son (F.E. Spath) discovered this long after his death, publishing an account of his father in 1982. The elder Spath no doubt kept his German heritage secret for the obvious reasons, given his time and place.

References:

Branger, P. 2004. Middle Jurassic Nautiloidea from western France. Rivista Italiana di Paleontologia e Stratigrafia 110: 141-149.

Halder, K. 2000. Diversity and biogeographic distribution of Jurassic nautiloids of Kutch, India, during the fragmentation of Gondwana. Journal of African Earth Sciences 31: 175-185.

Halder, K. and Bardhan, S. 1996. The fleeting genus Cymatonautilus (Nautiloidea): new record from the Jurassic Charl Formation, Kutch, India. Canadian Journal of Earth Sciences 33: 1007-1010.

Kummel, B. 1956. Post-Triassic nautiloid genera. Bulletin of the Museum of Comparative Zoology 114(7): 320-494.

Spath, F.E. 1982. L.F. Spath (1882 – 1957), ammonitologist. Archives of Natural History 11: 103-105.

Tintant, H. 1969. Les “Nautiles à Côtes” du Jurassique. Annales de Paleontologie Invertébrés 55: 53-96.

Tintant, H. 1987. Les Nautiles du Jurassique d’Arabie Saoudite. Geobios 20: 67-159.

Tintant, H. and Kabamba, M. 1985. The role of the environment in the Nautilacea, p. 58-66. In: Bayer, U. and Seilacher, A. (eds.), Sedimentary and Evolutionary Cycles. Lecture Notes in Earth Sciences, vol. 1, Springer (Berlin).

Wooster’s Fossil of the Week: A strophomenid brachiopod from the Middle Devonian of Michigan

September 1st, 2013

Stropheodonta demissa 585Every year in the first class session of my Invertebrate Paleontology course I give my students each an unknown fossil. It must be something relatively common so that I can give 20 nearly-identical specimens, and it is ideally of a species that can be identified (eventually) using web resources. This year I gave each student the strophomenid brachiopod shown above.

This is Strophodonta demissa (Conrad, 1842) from the Silica Shale Formation (Traverse Group, Givetian, Middle Devonian) exposed in an abandoned quarry near Milan, Washtenaw County, Michigan. These were collected by my friend Brian Bade, an ace amateur paleontologist. In the views above, the shell on the left has the dorsal valve exterior up, and the shell on the right has the ventral valve exterior up. Since the dorsal valve is concave and the ventral valve is convex, this brachiopod shape is called concavo-convex. It also has a long hinge line so we also call it strophic. The fine radiating lines are costae, and so this species is costate. Those characters pretty much define a typical strophomenid brachiopod. (And now all my students understand this, I’m sure.)

Strophodonta is a genus named by the famous American paleontologist James Hall (1811-1898), someone we previously profiled on this blog. The type species of the genus is Strophomena demissa Conrad, 1842, so that name becomes Strophodonta demissa (Conrad, 1842). The author names following taxa are known as the “authority”. They go into brackets for a species that was later placed in another genus. (T.A. Conrad was also mentioned and pictured in a previous entry.)
Screen Shot 2013-08-12 at 3.36.36 PMNow James Hall left us a bit of a puzzle with Strophodonta. In 1852 he published his original description of the genus and called it “Stropheodonta” (see above from the original). Note the addition of the “e”.
Screen Shot 2013-08-12 at 3.33.40 PMHowever, as you see above, in 1858 Hall referred to the same genus and spelled it Strophodonta, without the “e”. This is not only another spelling, it is another pronunciation of the name. He even retroactively refers to his 1852 name as Strophodonta as if he is correcting the spelling. (And indeed, he has “Strophodonta” also in the text of the 1852 monograph, but not in the description.) We’re thus faced with two names for the same genus, which is very naughty in taxonomy for obvious reasons. Today when you search for “Stropheodonta” on Google you get 3850 hits. Searching for “Strophodonta“, though, produces 121,000 hits.

So which spelling is correct? I’ve always used “Stropheodonta“, although now I see that puts me in the minority. A check of the Paleobiology Database shows Stropheodonta and Strophodonta as “alternative spelling” on one page. On another is the unhelpful statement: “It was corrected as Strophodonta by Williams et al. (2000); it was misspelled as Strophodonta by Sepkoski (2002).” (Yes, you have to read it carefully. I cut-and-pasted to make sure I got it as is.)

The Treatise on Invertebrate Paleontology is where we go to resolve problems like this (if an updated version is available). It turns out there that “Stropheodonta” is corrected as Strophodonta. Hall’s retroactive spelling change was accepted and Strophodonta is now the proper spelling and pronunciation. “Stropheodonta” is now a nomen vanum, or “vain name”. This means that it has “unjustified but intentional emendations”.

Ah, the legalese of scientific taxonomy! Obscure but essential for keeping our language relevant and useful.

References:

Conrad, T.A. 1842. Observations on the Silurian and Devonian systems of the United States, with descriptions of new organic remains. Journal of the Academy of Natural Sciences, Philadelphia 8: 228–280.

Hall, J. 1852. Palaeontology of New-York, vol. II. Containing descriptions of the organic remains of the lower middle division of the New-York System (equivalent in parts to the Middle Silurian rocks of Europe). C. Van Benthuysen Printers; Albany, New York, p. 63.

Hall, J. and Whitney, J.D. 1858. Report on the geological survey of the state of Iowa: embracing the results of investigations made during portions of the years 1855, 56 & 57, vol. I, part II: Palaeontology. C. Van Benthuysen Printers; Albany, New York, p. 491.

Williams, A., Brunton, H.C. and Carlson, S.J. 2000. Treatise on Invertebrate Paleontology. Part H, Brachiopoda Revised, Vol. 2: Linguliformea, Craniiformea, and Rhynchonelliformea (part). Treatise on invertebrate paleontology. Geological Society of America, Boulder, Colorado.

Wooster’s Fossil of the Week: A crab’s meal from the Pliocene of Cyprus

August 25th, 2013

Astraea rugosa side view_585This week’s fossil was collected on a Keck Geology Consortium expedition to Cyprus in the summer of 1996. My Independent Study student on that adventure was Steve Dornbos (’97), now a professor at the University of Wisconsin, Milwaukee (and a new father!). The other students on our paleontological project were Ellen Avery and Lorraine Givens. One day Steve and I stumbled across a beautifully-exposed coral reef weathering out of the silty Nicosia Formation (Pliocene) on the hot and dry Mesaoria Plain in the center of the island near the village of Meniko (N 35° 5.767′, E 33° 8.925′). The significance of this reef was that it represents the early recovery of marine faunas following the Messinian Salinity Crisis and the subsequent refilling of the basin (the dramatic Zanclean Flood). Steve and I published our observations and analyses of this reef community in 1999.

Our featured fossil is the herbivorous turbinid gastropod Astraea rugosa (Linnaeus, 1767). That beautiful generic name means “star-maiden” in Greek and was originally used by Linnaeus in homage to the mythological Astraea, daughter of Zeus (maybe) and a “celestial virgin”. The species name rugosa means “rough” or “wrinkled”, in reference to the many ridges on the shell. The common name for this species, which is still alive today (as you can see in this video) is “rough star”.

What was most interesting to Steve and me was how this shell is broken. Most of the shell appears to have been peeled away, leaving the central axis and top in excellent shape. This is characteristic of crab predation. The crab, usually using one enlarged claw, peels the shell open by breaking it at the aperture and moving up the spiral. Eventually it hits the terrified snail pulled up as far as it could go in its twisty spiral of doom.
Astraea_Screen Shot 2013-08-22 at 8.37.54 PM copyThe image above, from this Spanish webpage, shows one of the further defenses Astraea rugosa had against crab predation: a thick calcareous operculum blocking the aperture like a heavy door. In some places these opercula are commonly preserved, but we found only a few and could not associate them with any particular species.
Astraea rugosa apical_585Finally, here is the top view of Astraea rugosa from the Pliocene of Cyprus. There is wonderful detail still preserved in the apical region of the shell, including characteristic star-like projecting spines.

We’ll see more fossils from the Pliocene of Cyprus in this space!

References:

Cowper Reed, F.R. 1935. Notes on the Neogene faunas of Cyprus, III: the Pliocene faunas. Annual Magazine of Natural History 10 (95): 489-524.

Cowper Reed, F.R. 1940. Some additional Pliocene fossils from Cyprus. Annual Magazine of Natural History 11 (6): 293-297.

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.

Wooster’s Fossils of the Week: A foraminiferal ooze from the Pleistocene of Italy

August 18th, 2013

YCM forams 1On a recent field trip to Sicily, our paleontological party visited outcrops at Cala Sant’Antonino on the western side of the Milazzo Peninsula in the northwestern part of the island. We saw there an Early Pleistocene sedimentary unit informally called the “Yellow Calcareous Marls”. With a handlens you would see a close view of the rock like the image above. It consists almost entirely of tiny hollow white spheres with occasional dark flecks. In the lab back home these little calcitic balls were revealed to be tests (skeletons) of foraminiferans known as Globorotalia inflata (d’Orbigny, 1839). This is a classic example of a biogenic sediment called foraminiferal ooze, samples of which are now in Wooster’s paleontological and sedimentological teaching collections.
Foram-Marl-060913This is the outcrop of the “Yellow Calcareous Marls” at Cala Sant’Antonino from which the above samples were collected. The rock is very soft and powdery to the touch.

YCM forams 2In this closer view of the rock the individual foraminiferal tests are more apparent. Near the center is one example showing the connected bulbous chambers (making it multilocular) and the slit-like aperture between them. These tests are slightly recrystallized, giving them a sugary look. The dark bits are sand-sized volcaniclastic grains derived from early eruptions of the Mount Etna complex.

Globorotalia_inflataThese are modern examples of Globorotalia inflata. (The scale bars are 0.1 mm.) The bumpy surface texture, bulbous chambers and distinctive aperture make identification of the fossil examples fairly easy. The images were taken by Bruce Hayward.

Globorotalia inflata is a long-lived planktonic species, meaning it floats about near the top of the water column throughout the oceans. In life these single-celled organisms extend thin strands of material (pseudopodia) into the water around them to collect organic material and the occasional diatom or radiolarian for nutrition. They live in populations with billions of individuals, so under the right conditions their tests can accumulate on the seafloor in numbers so vast they form thick deposits, our foraminiferal oozes. Our particular ooze in this story formed in relatively deep (epibathyal), cool waters during one of the early glacial intervals. This foraminiferan turns out to be a critical guide to the age of the unit as well as its paleoenvironmental context.

References:

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.

Sciuto, F. 2012. Bythocythere solisdeus n. sp. and Cytheropteron eleonorae n. sp. (Crustacea, Ostracoda) from the Early Pleistocene bathyal sediments of Cape Milazzo (NE, Sicily). Geosciences 2012 2: 147-156.

 

Wooster’s Fossil of the Week: An almost planispiral gastropod from the Middle Jurassic of southern Israel

August 11th, 2013

 

Discohelix tunisiensis apical copyAdd this to the list of fossils that have confused me. This summer, during a Wooster expedition, Lizzie Reinthal and Steph Bosch collected the above specimen from the Matmor Formation (Middle Jurassic, Callovian) of southern Israel. I simply assumed it was an ammonite, especially because we were anxious to find ammonites to further reinforce our biostratigraphic framework (how we tell in which geological time interval our fossils belong). When I later tried to identify it by searching through the Jurassic ammonite literature, though, I could find nothing like it. I then sent a photograph to my friend Zeev Lewy, a prominent ammonite expert recently retired from the Geological Survey of Israel. His answer was a surprise: this fossil is the gastropod Discohelix tunisiensis Cox 1969.
Discohelix tunisiensis adapicalHow could this be a snail when it looks so much like a cool, multi-whorled planispiral ammonite, complete with ribs? Well, it is not planispiral, now that I look at it again. Above you see the other side of the specimen, with its slightly depressed center. Most ammonites don’t show such asymmetry. This actually is a gastropod, and it represents an ancient group (the clade Vetigastropoda — don’t get me started on the complications of gastropod systematics!) with primitive features reminiscent of Paleozoic marine snails (from a group I learned to call “archaeogastropods“). It is not as much that the snail has converged on an ammonite style of shell, it’s that the ammonites developed a similar shell much later for entirely different reasons (swimming, for example). Discohelix was likely an herbivore grazing in patchy coral reefs like we have represented in the Matmor Formation. It has become a useful index fossil for the Jurassic of the Tethyan Realm, although this is the first time I’ve found it in Israel.
Pseudotorinia (Architae-group) retiferaThe above is the marine snail Pseudotorinia (Architae-group) retifera. It used to be called Discohelix retifera, and you can see why. It may not be in the same genus, but you can see that this modern group and Discohelix are closely related. Discohelix itself is now known only from the fossil record.
DunkerDiscohelix was named as a genus in 1847 by Wilhelm Bernhard Rudolph Hadrian Dunker (1809-1885), a German natural scientist with interests in geology, paleontology and marine zoology. (I love that middle name of “Hadrian”.) Like so many 19th Century paleontologists, Dunker started with a practical training in mining engineering and then followed a passion for fossils and modern shells. He had a huge collection of materials that eventually ended up in the Museum für Naturkunde in Berlin. He traded and corresponded with many top scientists of his day, including Charles Darwin. He also published many monographs on modern and fossil molluscan taxa. In 1846, he and Hermann von Meyer established the journal Palaeontographica. This journal survives to this day in two descendants: Palaeontographica A (Paleozoology, Stratigraphy) and Palaeontographica B (Paleobotany).

References:

Cox, L.R. 1969. Gasteropodes Jurassiques du Sud-Est Tunisien [Jurassic gastropods from SE Tunisia]. Annales de Paleontologie, Invertebres 55: 241-268.

Grundel, J. 2005. The genus Discohelix Dunker, 1847 (Gastropoda) and on the content of the Discohelicidae Schroder, 1995. Neues Jahrbuch fur Geologie und Palaontologie-Monatshefte 12: 729-748.

Tëmkin, I., Glaubrecht, M. and Köhler, F. 2009. Wilhelm Dunker, his collection, and pteriid systematics. Malacologia 51: 39-79.

Wendt, J.1968. Discohelix (Archaeogastropoda, Euomphalacea) as an index fossil in the Tethyan Jurassic. Palaeontology 11: 554-575.

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