Archive for January, 2016

Wooster’s Fossil of the Week: A brachiopod with a heavy burden (Upper Ordovician of southeastern Indiana)

January 29th, 2016

1 Trepostome on Hebertella richmondensisYes, the above image doesn’t look much like a brachiopod, but just wait. We see a trepostome bryozoan with extended knobs and a few borings. Flip it over, though …
2 Hebertella richmondensis ventral view 585… and we see that the bryozoan almost entirely covers a brachiopod. So far, so common among Ordovician fossils. However, look closely at the margin of the brachiopod valve and how clearly it is delineated from the bryozoan. It is apparent that the bryozoan had encrusted a living brachiopod, and the brachiopod stayed alive, keeping the essential commissure (the gap between the valves) open for feeding. We are looking at the valve that was in contact with the substrate (the underside of the living brachiopod). The bryozoan occupied the upper exposed surface, growing across that valve (which is invisible to us now), past its edge, but not closing the gap with the other valve. The same bryozoan species is found on the above visible valve, but only as two thin films unconnected to the colony on the upper side.
3 Hebertella richmondensis bryo close annotatedA closer view of the brachiopod hinge shows additional evidence that the bryozoan and brachiopod were living together. The red arrow on the left points to where the fleshy pedicle (attaching stalk) of the brachiopod extended from the shell to meet the substrate. The bryozoan here curves around the now-vanished pedicle. The yellow arrow on the right shows how the bryozoan growth surface folded to accommodate the opening valves at the hinge. Pretty cool.

I can’t identify the bryozoan beyond Order Trepostomata without cutting it open. The brachiopod, though, appears to be Hebertella richmondensis Foerste, 1909. This specimen is from the Whitewater Formation (Upper Ordovician, upper Katian) exposed near Richmond, Indiana. It was collected on one of my field trips in 2003.
4 Hebertella richmondensis ventral view 585 annotatedWhat do we learn from this little assemblage? We first see a relatively uncommon example of a clear living relationship between a sclerobiont and its host. We also learn that the brachiopod could continue to open its valves for feeding despite the heavy calcitic bryozoan weighing it down. We even can see that this brachiopod was not living on a soft muddy substrate because only a small triangular-shaped area (see above) in the center was clear of encrusters; the thin bryozoan (and maybe a bit of the stromatoporid sponge Dermatostroma) had enough space between the valve and the substrate to feed and respire. None of this is surprising, but it is nice to see our models of how these organisms lived are congruent with the evidence.


Alexander, R.R. and Scharpf, C.D. 1990. Epizoans on Late Ordovician brachiopods from southeastern Indiana. Historical Biology 4: 179-202.

Foerste, A.F. 1909. Preliminary notes on Cincinnati fossils. Bulletin of the Scientific Laboratory of Denison University 14: 208–232.

Walker, L.G. 1982. The brachiopod genera Hebertella, Dalmanella, and Heterorthina from the Ordovician of Kentucky. USGS Professional Paper 1066-M.

Wright, D.F. and Stigall, A.L. 2013. Phylogenetic revision of the Late Ordovician orthid brachiopod genera Plaesiomys and Hebertella from Laurentia. Journal of Paleontology 87: 1107-1128.

Wooster’s Fossils of the Week: Gastropod opercula from the Pliocene of Cyprus

January 22nd, 2016

Opercula coral reef Pliocene Cyprus 585This week’s brief entry (it is short because we’re in the first few days of a new semester at Wooster) is related to last week’s post. Above are two gastropod opercula from the Nicosia Formation (Pliocene) of Cyprus. They were collected on a Keck Geology Consortium expedition to Cyprus in the summer of 1996 with Steve Dornbos (’97). An operculum for a gastropod is a kind of hard door attached to the muscular foot that closes off the aperture when the snail is fully retracted into its shell. On the left is the inside of an operculum, and on the right is the elegantly spiraled outside. The operculum provides protection for the snail from both drying out during a low tide and from prying (literally!) predators.

We can’t tell for certain, but we think these opercula are from the herbivorous gastropod Astraea rugosa featured in last week’s entry. We found them at our fossil coral reef site in the same deposit as the A. rugosa shells. They also look very much like these modern A. rugosa opercula.
Astraea_Screen Shot 2013-08-22 at 8.37.54 PM copyAbove is a diagram of Astraea rugosa with the operculum (“opérculo calcificado”) in place. (The drawing comes from a Spanish webpage no longer in existence.)


Checa, A.G. and Jiménez-Jiménez, A.P. 1998. Constructional morphology, origin, and evolution of the gastropod operculum. Paleobiology 24: 109-132.

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 Fossil of the Week: A turbinid gastropod from the Pliocene of Cyprus

January 15th, 2016

Astraea rugosa (Linnaeus, 1767) opened coral reefWe saw this broken gastropod from the Pliocene of Cyprus in this blog post about two and a half years ago. I recently rediscovered it while sorting specimens and decided to show this intriguing perspective through the broken part of the shell. It was collected on a Keck Geology Consortium expedition to Cyprus in the summer of 1996. My Independent Study student on that expedition was Steve Dornbos (’97), now a professor of geology at the University of Wisconsin, Milwaukee. One sunny day Steve and I came across a beautiful 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′ — go ahead, search these coordinates for a great satellite view). The reef records 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.
Astraea rugosa (Linnaeus, 1767) worm coral reefOur 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”. In the top image you can see the internal shell twist at the axis of coiling called the columella. In the image above is a delicate little coiled tube of the vermetid gastropod Petaloconchus preserved where it attached to the shell about five million years ago.

Stay tuned here for additional fossils from the Pliocene of Cyprus. They are too good not to share!


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.

Update from Classifying the Unknown: the Lunar Edition

January 10th, 2016

9[Guest Blogger: Annette Hilton (’17)]

This past summer I had the privilege of working as an intern in the Earth and Planetary Sciences department at the American Museum of Natural History (AMNH) — please see my previous blog post. Since then I’ve been lucky enough to continue research with my advisor, Dr. Juliane Gross (Rutgers University, associate of AMNH).

Our project was to investigate a new meteorite found in Northwest Africa in 2015 to: 1) confirm its lunar origin and potential grouping, 2) classify the rock, 3) place constraints on its crystallization history and source location, and 4) improve our understanding of unsampled areas of the Moon and expand our knowledge of lunar highland rock types.

During our research we conducted Electron Probe Micro-Analysis (EPMA) at the AMNH and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) at the Lamont-Doherty Earth Observatory (LDEO) of Columbia University to obtain geochemical data. We additionally calculated modal mineralogy using qualitative elemental X-ray maps in combination with two computational programs called IDRISI Selva (Eastman, 2012; Fisher, 1936) and XMapTools (MATlab) (Lanari et al., 2013). Using this data set in conjunction with a computational program (Calzada-Diaz et al., 2015), we were able to estimate a few potential source locations on the lunar surface from which the meteorite might have originated.

The name and classification for the meteorite was accepted by the Meteoritical Society in late December 2015. Its official name is Northwest Africa 10401 and is one of 60 approved meteorites classified as lunar. We classified the petrography of the rock as an anorthositic troctolite with a granulitic texture, which means it contains mainly plagioclase with a mafic component (i.e., olivine and pyroxene) that has a granular (rounded) texture. Composition of the rock was based on our 6 x12mm thick section of the sample and is composed primarily of Ca-bearing plagioclase (59-65%), with lesser olivine (23-26%), pyroxene (12-15%) (orthopyroxene and clinopyroxene), glass, and accessory phases spinel and metal.

We submitted an abstract to the 47th Lunar and Planetary Sciences Conference in March 2016, at which Juliane Gross and I will present our research about this meteorite Northwest Africa 1040.
Annette010716Fig. 1: Mosaic X-ray elemental maps of the meteorite thick section. a) Si Kα map b) Ca Kα map d) combined RedGreenBlue (RGB-SiFeCa)) map. In general, blue-green = olivine; blue = orthopyroxene; light pink = clinopyroxene; pink = maskelynite (shocked plagioclase); white = epoxy (Hilton et al., 2016).

The meteoritical bulletin classification can be found at:

Acknowledgements: A big thank you to Juliane Gross, AMNH, NSF REU Program for Physical Sciences, Abigail Calzada-Diaz for running the computational program for the lunar surface, and Wooster’s excellent Geology professors and staff.

[College news release. January 11, 2016]


Calzada-Diaz, A., Joy, K.H., Crawford, I.A., and Nordheim, T.A. 2015. Constraining the source regions of lunar meteorites using orbital geochemical data. Meteoritics & Planetary Science 50: 214–228.

Eastman, J.R., 2012. IDRISI Selva. Clark University, Worcester, MA.

Fisher, R.A. 1936. The use of multiple measurements in taxonomic problems. Annals of Eugenics 7: 179-188.

Hilton, A., Gross, J., Korotev, R., Calzada-Diaz, A. 2016. Classifying the unknown–the lunar edition: North West Africa 10401 a new type of the Mg-suite rock?  47th Lunar and Planetary Science Conference. Abstract.

Lanari, P., et al. 2013.  XMapTools: A MATLAB©-based program for electron microprobe X-ray image processing and geothermobarometry. Computers & Geosciences,

Science Highlights from VMSG 2016

January 8th, 2016

Dublin, Ireland – The technical program of VMSG 2016 concluded today and I am saturated with new ideas about igneous systems. Abstracts for all of the talks and posters can be found on the VMSG 2016 website.  There were so many excellent presentations, but I thought I’d mention just a few of the highlights.

Ian Saginor at Keystone College shared his xxxx initiative to use 3-D models for volcanology education and outreach.

Ian Saginor  shared his Volcano Terrain Initiative to use 3-D models for volcanology education and outreach.


Maren Kahl used a clever systems approach to understand the magmatic plumbing system at Mt. Etna. She combined kinetic and thermodynamic modeling of complexly zoned olivine crystals erupted over time. (Link to her 2015 Journal of Petrology paper)

When Ben Hayes discussed his idea for the formation of plagioclase-pyroxene layering in the Bushveld Complex by downward percolation of a dense melt through a crystal mush, Mary Reinthal (’16) said she felt like she was reliving Petrology class. I guess that layered mafic intrusions lab had an impact!

Janine Kavanagh presented her experimental work on dikes in which she observed hybrid sill-dike intrusions when her injected fluids impinged on boundaries between layers in the host rock. (Link to her 2015 Earth and Planetary Science Letters paper)

John Maclennan gave a talk about the uncertainties (and deadly implications) of interpreting pressures from CO2 compositions of melt inclusions.

Chris Bean explained that, by recording long period (Lp) seismic events close to the source, we can see that they are better explained by brittle failure events in shallow edifice rocks rather than magma movement. (Link to his 2014 Nature paper)

Many presenters referred to the recent Nature paper by 2015 by Bergantz, Schleicher, and Burgisser on magma mush dynamics. Their study related magma injection rate to complex mineral textures and fabrics in magmatic systems. (Link to Bergantz et al., 2015 Nature paper)

Wooster’s Fossils of the Week: Atrypid brachiopods attached to a trepostome bryozoan from the Upper Ordovician of southern Indiana

January 8th, 2016

Zygospira Attached 585This is a follow-up post to our entry on Christmas Day two weeks ago. Above is a trepostome bryozoan (the long porous piece) with specimens of the atrypid brachiopod Zygospira modesta clustered around it. They are positioned with their ventral valves outward because in life they were attached to this bryozoan with tiny fleshy stalks called pedicles. They were buried quickly enough that this spatial relationship was preserved. Cool. This assemblage was found in the Liberty Formation (Upper Ordovician) exposed in a roadcut in southern Indiana.
Zygospira modesta dorsal annotatedThis is a view of the dorsal side of Zygospira modesta showing the pedicle opening in the ventral valve at the apex of the shell.


Copper, P. 1977. Zygospira and some related Ordovician and Silurian atrypoid brachiopods. Palaeontology 20: 295-335.

Sandy, M.R. 1996. Oldest record of peduncular attachment of brachiopods to crinoid stems, Upper Ordovician, Ohio, USA (Brachiopoda; Atrypida: Echinodermata; Crinoidea). Journal of Paleontology 70: 532-534.

Good things happen at VMSG

January 7th, 2016

Dublin, Ireland – Congratulations to Mary Reinthal (’16) for a successful poster presentation at VMSG 2016!

image-5-768x1024_sizedMary did a fantastic job giving her ‘lightning talk,’ a two-minute round-robin-style presentation of her poster.

The poster session was everything that it should be. Mary received excellent feedback and advice on her research, met a number of people who are working on similar projects, and expanded her post-graduation career opportunities. She was an excellent representative of the Wooster Geology program. Well done!

Wooster Geologists in Ireland

January 6th, 2016

Greetings from Dublin! Mary Reinthal (’16) and I are attending the annual conference of the Volcano and Magmatic Studies Group (#VMSG2016) at Trinity College. Volcanologists, petrologists, geochemists, and geophysicists have gathered to share their research on igneous topics ranging from large igneous provinces (LIPs) to volcanic hazards. We started the conference, appropriately, with a tour of the architecture and building stones on Trinity’s campus.

The tour began in Parliament Square, so named for the Parliament that supported the construction of the surrounding buildings during the 1700s.

The tour began in Parliament Square, so named for the Parliament that supported the construction of the surrounding buildings during the 1700s.

In the background, you see the Chapel (1787-98), which is composed of the golden brown, granular Leinster granite. The windows are surrounded by Portland Stone, a fossiliferous limestone from Dorset.

The floor of the square is paved with polished glacial cobbles of a variety of lithologies, including limestone and andesite.

The floor of the square is paved with polished glacial cobbles of a variety of lithologies, including limestone and andesite.

Walkways of marble from China were added later to make the square more accessible.

Walkways of gneiss from China were added later to make the square more accessible.

Our last stop was the Museum Building, which houses the Geology and Engineering Departments. The building was recently cleaned in a painstaking effort that lasted ~4 years and involved the removal of gypsum deposits by dental drill and soot by a slow stream of water, but it was worth the effort. The architectural details of the Museum Building are breathtaking. On the exterior, the Portland Stone features intricate and unique carvings of leaves, birds, cats and mice, and other natural objects.

Visitors are greeted with robust pillars of limestone or Connemara marble.

Inside the building, visitors are greeted with robust pillars of limestone or Connemara marble.

Step past the pillars and you'll be awed by a soaring, colorful enameled brick ceiling.

Step past the pillars and you’ll be awed by a soaring, colorful enameled brick ceiling.

The Museum Building was the perfect venue for tonight’s conference ice-breaker, where we were finally able to connect faces to familiar names. Overall, it was a successful introduction to a vibrant and welcoming community of scientists. Tomorrow, Mary becomes an official member of that community when she’ll present her research on water on subglacial volcanics.



Five-Year Anniversary Edition of Wooster’s Fossil of the Week: A tabulate coral from the Devonian of northwestern Ohio

January 1st, 2016

AuloporaDevonianSilicaShale010211This post of Wooster’s Fossil of the Week marks five years of this feature. If you’re counting, that is 260 entries, with never a week missed. To celebrate, I’m returning to the very first fossil in the series, a beautiful encrusting tabulate coral. The original entry is below, with some updates and added links.

This week’s fossil was collected by Brian Bade of Sullivan, Ohio, and donated to Wooster as part of my hederelloid project.  It is a beautiful specimen of the tabulate coral Aulopora encrusting a brachiopod valve from the Silica Shale (Middle Devonian — about 390 million years old) of northwestern Ohio.  [Update: I now know the species is A. microbuccinata Watkins, 1959.] Auloporid corals are characterized by an encrusting habit, a bifurcating growth pattern, and horn-shaped corallites (individual skeletal containers for the polyps).

What is especially nice about this specimen is that we are looking at a well preserved colony origin.  The corallite marked with the yellow “P” is the protocorallite — the first corallite from which all the others are derived.  You can see that two corallites bud out from the protocorallite 180° from each other.  These two corallites in turn each bud two corallites, but at about 160°.  This pattern continues as the colony develops (a process called astogeny).  The angles of budding begin to vary depending on local obstacles; they never again go below 160°.

The polyps inside the corallites are presumed to have been like other colonial coral polyps.  Each would have had tentacles surrounding a central opening, and all were connecting by soft tissue within the skeleton.  They likely fed on zooplankton in the surrounding seawater.  This type of coral went extinct in the Permian, roughly 260 million years ago.

Again, we thank our amateur geologist friends for such useful donations to the research and educational collections in the Geology Department at Wooster.

Later I began to add information about a notable paleontologist associated with the highlighted fossil. I especially wanted to put a face and brief biography with a name we may often see in our taxonomic pursuits but know little about. We can now add this German gentleman from a previous entry —
August_Goldfuss_1841Aulopora was first described in 1826 by Georg August Goldfuss (1782-1848), a German paleontologist and zoologist. (Goldfuß is the proper spelling, if I can use that fancy Germanic letter.) He earned a PhD from Erlangen in 1804 and later in 1818 assumed a position teaching zoology at the University of Bonn. With Count Georg zu Münster, he wrote Petrefacta Germaniae, an ambitious attempt to catalog all the invertebrate fossils of Germany (but only got through some of the mollusks). The 1841 portrait above is by Adolf Hohneck (1812-1879).

Since the first few entries I began to add a few critical references for the fossils and related stratigraphy. At first these were for me so that I could remember where I got the information used in the text. Later I noted that students and others were finding these entries online and using them as brief introductions to particular taxa. A few references made each entry a starting point for someone else’s paleontological explorations. Here are some added citations for Aulopora


Fenton, M.A. 1937. Species of Aulopora from the Traverse and Hamilton Groups. American Midland Naturalist 18: 115-119.

Fenton, M.A. and Fenton, C.L. 1937. Aulopora: a form-genus of tabulate corals and bryozoans. American Midland Naturalist 18: 109-115.

Goldfuß, G.A. 1826-1844. Petrefacta Germaniae. Tam ea, quae in museo universitatis Regia Borussicae Fridericiae Wilhelmiae Rhenanae servantur, quam alia quaecunque in museis Hoeninghusiano Muensteriano aliisque extant, iconibus et descriptionibus illustrata = Abbildungen und Beschreibungen der Petrefacten Deutschlands und der angränzenden Länder, unter Mitwirkung von Georg Graf zu Münster, Düsseldorf.

Helm, C. 1999. Astogenese von Aulopora cf. enodis Klaamann 1966 (Visby-Mergel, Silur von Gotland). Paläontologische Zeitschrift 73 (3/4): 241–246. [Courtesy of Paul Taylor]

Scrutton, C.T. 1990. Ontogeny and astogeny in Aulopora and its significance, illustrated by a new non‐encrusting species from the Devonian of southwest England. Lethaia 23: 61-75.

Watkins, J.L. 1959. Middle Devonian auloporid corals from the Traverse Group of Michigan. Journal of Paleontology 33: 793-808.