Wooster’s Fossil of the Week: A mystery fossil for my Invertebrate Paleontology students

September 4th, 2015

1 Stereolasma singleAt the beginning of my Invertebrate Paleontology course I give each student a fossil to identify by whatever means necessary. I challenge them to take it down to the species level, and tell me its age and likely place of collection. The fossil this year is shown above: the rugose coral Stereolasma rectum (Hall, 1843) from the Middle Devonian of New York. I collected the specimens on my western New York adventure last month from the Wanakah Shale Member of the Ludlowville Formation at Buffalo Creek in Erie County. (There were a lot of them! This coral is so common that you can buy them online at science supply stores.)

The corals I collected were well weathered on the Devonian seafloor. You can see some evidence of this in the exterior which shows opened tunnels of borings. They were not appreciably weathered on the outcrop because they were directly excavated from the shale matrix.
2 Stereolasma cross section 585This is a cross-section through one of the S. rectum specimens. The internal radiating calcitic partitions (septa) are well preserved by clear calcite cement. There appear to be at least two generations of sediment that penetrated into the interior after the death of the polyp. The posthumous events affecting these corals may be more interesting than their life histories.

That awkward species name comes from the Latin rectus for “straight”. The anatomical rectum that we all know well comes from the same root but is based on a misconception by early anatomists that the terminal part of the large intestine in mammals is straight. It’s not, as a Google search will quickly show you. (I decided against including an image.)
3 Wanakah coralsReferences:

Baird, G.C. and Brett, C.E. 1983. Regional variation and paleontology of two coral beds in the Middle Devonian Hamilton Group of Western New York. Journal of Paleontology 57: 417-446.

Brett, C.E. and Baird, G.C. 1994. Depositional sequences, cycles, and foreland basin dynamics in the late Middle Devonian (Givetian) of the Genesee Valley and western Finger Lakes region. In: Brett, C.E., and Scatterday, J., eds., Field trip guidebook: New York State Geological Association Guidebook, no. 66, 66th Annual Meeting, Rochester, NY, p. 505-585.

Busch, D.A. 1941. An ontogenetic study of some rugose corals from the Hamilton of western New York. Journal of Paleontology 15: 392-411.

Stumm, E.C. and Watkins, J.L. 1961. The metriophylloid coral genera Stereolasma, Amplexiphyllum, and Stewartophyllum from the Devonian Hamilton group of New York. Journal of Paleontology 35: 445-447.

A day’s excursion into the Middle Devonian of western New York

August 7th, 2015

1 Wanakah at Buffalo CreekLOCKPORT, NEW YORK (August 7, 2015) — Today Andrej Ernst and I were able to join Brian Bade and his friends on a collecting trip up Buffalo Creek in Erie County, New York. Our goal was simply to look for interesting fossils in the Wanakah Shale Member of the Ludlowville Formation (Middle Devonian) and enjoy the fellowship of fossil enthusiasts. Success on both counts. It was a great day, and rather fun wading through the cool waters of the creek as we examined the shale on the banks.

2 Wanakah TrilobiteHere is an external mold of a trilobite in the soft Wanakah Shale. An external mold is an impression of the exterior of the organism. If you look at this upside-down it pops into reverse relief! This fossil is not recoverable because it would break into bits with any attempt to hammer it out. Andrej and I found plenty of bryozoans here, along with other cool fossils.

3 Bethany Center Centerfield LimestoneAs a bonus we also were able to visit the Bethany Center exposure of the Centerfield Limestone, also Middle Devonian. There isn’t much left of the exposure, as you can see, but we still found numerous encrusting organisms (sclerobionts) on brachiopods and the abundant rugose corals. We also got plenty of sun here.

Wooster’s Fossil of the Week: A coiled nautiloid from the Middle Devonian of Ohio

July 17th, 2015

Goldringia cyclops Columbus Ls Devonian 585The above fossil is a nautiloid cut in cross-section, showing the large body chamber at the bottom and behind it to the left and above the phragmocone, or chambered portion of the conch (shell). It is a species of Goldringia Flower, 1945, found in the Columbus Limestone (Middle Devonian, Eifelian) exposed in the Owen Stone Quarry near Delaware, Ohio. It is a nice specimen for both what it shows us about a kind of nautiloid coiling and for clues to its preservation.

This specimen was originally labelled Gyroceras cyclops Hall, 1861. In 1945, Rousseau Flower designated this taxon the type species of Goldringia. I can’t tell if we really have G. cyclops here or some other species, so I’m leaving it at the genus level. The old name lingers, though, in the term for this kind of open coiling: gyroceraconic. It is one of the earliest examples of the nautiloids having the phragmocone positioned above the body chamber, presumably for stable buoyancy.
Pentamerid embedded 071315I like the clues to the early history of this conch after death. The chambers are entirely filled with sediment, a fossiliferous micrite. You can see places where the original shell was broken and larger bits infiltrated, like the whole brachiopod shown above. This brachiopod appears from its cross-section to be a pentamerid. Also visible are strophomenid brachiopods and gastropods.
Winifred GoldringRousseau Hayner Flower (1913–1988) described Goldringia in 1945. He doesn’t directly say who he named it after, but he thanks “Dr. Winifred Goldring of the New York State Museum” in the acknowledgments. We can tell Flower’s story later (and it’s a good one), but this gives us a chance to introduce Winifred Goldring (1888-1971). She was the first paleontologist to describe the famous Gilboa fossil flora (Devonian) in upstate New York, and she was the first woman State Paleontologist of New York (or anywhere, for that matter). (Now there is Lisa Amati in this prestigious position. Congratulations, Lisa!) Goldring grew up near Albany, New York, one of nine children in a very botanical family. She graduated from Wellesley College in 1909 with a bachelor’s degree in geology (very unusual for a woman at the time). She stayed at Wellesley to earn a master’s degree (1912). She also taught geology courses at Wellesley. In 1913 she studied geology at Columbia University with the famous Amadeus Grabau. In 1914, Goldring joined the scientific staff at the New York State Museum as a “scientific expert”. She worked her way up through the many ranks there to become State Paleontologist in 1939. She is best known as a paleontologist for her work with the fascinating Gilboa fossil forest, bringing her early upbringing by botanists to full circle. Along the way she was the first woman president of the Paleontological Society (in 1949) and vice-president of the Geological Society of America (in 1950). A hero of paleontology.


Flower, R.H. 1945. Classification of Devonian nautiloids. American Midland Naturalist 33: 675–724.

Goldring, W. 1927. The oldest known petrified forest. Scientific Monthly 24: 514–529.

Koninck, L.G.D. 1880. Faune du Calcaire Carbonifere de la Belgique, deuxieme partie, Genres Gyroceras, Cyrtoceras, Gomphoceras, Orthoceras, Subclymenia et Goniatites. Annales du Musee Royal d‘Histoire Naturelle, Belgique 5: 1–333.

A Day in Stromness

June 21st, 2015

1 Stromness Museum sceneSTROMNESS, SCOTLAND (June 21, 2015) — I intended to explore the region around Stromness today as I waited for the late afternoon ferry to Thurso, but it rained continuously. Since I can’t afford to get my meager kit wet while traveling, I was confined to indoors activities, including visiting the excellent though small Stromness Museum.

2 Labradorite as ballastThe bulk of the museum displays are devoted to maritime history, naturally, but there is always some geology. This, for example, is a beautiful piece of labradorite (from, naturally, Labrador) used as ship ballast.

3 Hugh Miller fossilI was very pleased to see this small exhibit on the brilliant polymath Hugh Miller (1802-1856) and the fossils he collected from Devonian rocks in the region. This is his most famous specimen: “The Asterolepis of Stromness”. He was the earliest expert on the Old Red Sandstone and its fossils.

This afternoon I take the ferry across these stormy seas back to the Scottish mainland. I’ve very much enjoyed Orkney, cold and wet though it is.

Wooster’s Fossils of the Week: The mysterious Paleozoic encrusters Ascodictyon and Allonema

September 12th, 2014


1 Slide01The above pair of fossils are small sclerobionts commonly found on hard substrates in shallow marine sediments through much of the Paleozoic, especially the Silurian and Devonian. Paul Taylor and I have been studying them for a few years now and our first paper on them was published this summer (Wilson and Taylor, 2014). Ascodictyon (Silurian-Carboniferous) is on the left and Allonema (Silurian-Permian) is on the right. Both are calcitic encrusters and look, at least in this view, very different from each other. We present evidence in our paper, though, that strongly suggests Ascodictyon and Allonema are actually manifestations of the same organism. What that organism is, exactly, still eludes us. We are persuaded at the very least that they are not bryozoans as originally described by Nicholson, Ulrich and Bassler. Since they are so common their identity is important for studies of fossil diversity and paleoecology.
2 Slide07The above view through a light microscope of Ascodictyon and Allonema shows the perspective paleontologists have had of these encrusters until recently. The clear calcite skeletons sitting on a calcitic brachiopod shell (this is from the Devonian of Michigan) makes for little contrast and poor resolution, and the microscope-camera combination has a very limited depth of field. The rest of the images in this post were made with a Scanning Electron Microscope (SEM) expertly operated by Paul. The difference in morphological detail is not just astonishing, it is a revolution in the study of tiny fossils like this.
3 Slide16 siluriense UKThis is a typical view of Ascodictyon. It consists of stellate clusters of inflated vesicles (like little calcite balloons) connected by thin calcitic tubes called stolons. (Ascodictyon siluriense from the Silurian of the England.)

4 Slide24 waldronense S GotlandThis is a typical Allonema. The primary form is a series of porous vesicles attached in chains like sausages. (Allonema waldronense from the Silurian of Gotland, Sweden.)

5 Slide29 Silica MIHere is where these obscure little encrusters get interesting. This is a specimen from the Silica Shale (Middle Devonian) exposed in Michigan. It was collected in a beautiful suite of fossils by that intrepid citizen scientist, Brian Bade. It consists of Allonema sausages connected to Ascodictyon stolons which are themselves connected to Ascodictyon stellate vesicle clusters. Clear evidence that Allonema and Ascodictyon are end members of a morphological continuum produced by the same organism.

7 Slide33 Silica MIA critical feature we see in this Ascodictyon/Allonema complex is the occurrence of “sockets” at the bases of vesicles like the above from the Silica Shale. These are almost certainly places where some erect portion of the organism extended above the substrate. Maybe these were feeding devices? Reproductive parts? We’ve found no trace of them.

8 Slide39 S GotlandOur hypothesis is that Allonema (left) and Ascodictyon (right, both from the Silurian of Gotland, Sweden) are the basal parts of some as yet unknown erect organism. They may have stored nutrients for the creature. We are convinced they were not bryozoans, foraminiferans, corals or sponges. Unfortunately we can only classify them as incertae sedis or Microproblematica. At some point we’ll have to figure out how to name this complex with two genera and over a dozen species.

It was fun work, and the project continues. For more detail, see Wilson and Taylor (2014).


Nicholson H.A. and Etheridge R. 1877. On Ascodictyon, a new provisional and anomalous genus of Palæozoic fossils. J. Nat. Hist., Series 4, 19: 463-468.

Ulrich E.O. and Bassler R.S. 1904. A revision of the Paleozoic Bryozoa. Smith. Misc. Coll. (Quart.) 45: 256-294.

Wilson M.A. and Taylor P.D. 2001. “Pseudobryozoans” and the problem of encruster diversity in the Paleozoic. PaleoBios 21 (Supplement to No. 2): 134-135.

Wilson, M.A. and Taylor, P.D. 2014. The morphology and affinities of Allonema and Ascodictyon, two abundant Palaeozoic encrusters commonly misattributed to the ctenostome bryozoans. In: Rosso, A., Wyse Jackson, P.N. and Porter, J. (eds.), Bryozoan Studies 2013. Studi trentini di scienze naturali 94: 259-266.

Wooster’s Fossils of the Week: Orthid brachiopods from the Middle Devonian of New York

August 29th, 2014

Tropidoleptus carinatus 585On the first day of the Invertebrate Paleontology course at Wooster, I give all the students a fossil to identify as best they can. Everyone gets the same kind of specimen, and they can use any means to put as specific a name on it as possible. Most students struggle with the exercise, of course — I just want them to spend some time looking at fossils online and getting a feel for distinguishing characteristics and preservation. This week, though, one student nailed it. Meredith Mann (’16) identified the target fossil above as Tropidoleptus carinatus (Conrad, 1839) from the Middle Devonian of  New York. I suppose if I asked she could have told me it was from the Kashong Shale Member of the Moscow Formation, and that it was collected by my friend Brian Bade. Nicely done, Meredith!

Tropidoleptus carinatus (Conrad, 1839) is a member of the Orthida, an order of brachiopods that lived from the Early Cambrian up to the Permian extinction. Orthids are a difficult group to characterize because they were so variable in shell shape and form. T. carinatus, for example, is one of the few orthids to have a concavo-convex shell, meaning that one side is concave (on the right in the image above) and the other convex (left). Most orthids are biconvex, meaning that both sides are convex. (A lima bean would also be biconvex by this definition.)

I like these little brachiopods because their shells are often encrusted by wonderful little creatures like bryozoans, Allonema, Ascodictyon, and microconchids. Each shell had the potential of hosting its own little community of encrusters.

Wooster’s Fossil of the Week: An interlocking rugose and tabulate coral (Devonian of Michigan)

February 23rd, 2014

Hexagonaria percarinata colony viewThis beautifully polished fossil looks like half of an antique bowling ball. Normally I hate polished fossils because the external details have been erased, but in this case the smooth surface reveals details about the organisms and their relationship. We have here a large colonial rugose coral with a smaller tabulate coral embedded within it. The specimen is from the Devonian of Michigan. It may look familiar because it is a large “Petoskey Stone“, the state stone (not fossil!) of Michigan. The large rugose coral is Hexagonaria percarinata (Sloss, 1939).
Hexagonaria percarinata close view 585In this closer view you can see the multiple star-like corallites of this coral. Each corallite held a tentacular feeding polyp in life. The radiating lines are thin vertical sheets of skeleton called septa. The corallites in this type of coral shared common walls and nestled up against each other as close as possible. In the lower center of the image you can see a very small corallite that represents a newly-budded polyp inserting itself as the colony grew. If rugose corals were like modern corals (and they probably were), the polyps were little sessile benthic carnivores catching small passing organisms with a set of tentacles. They may also have had photosymbionts to provide oxygen and carbohydrates through photosynthesis.
Tabulate coral intergrown with HexagonariaIn the midst of the rugose coral is this irregular patch with another type of coral: a tabulate coral distinguished by numerous horizontal partitions in its corallites (and no septa). It was likely a favositid coral, sometimes called a “honeycomb coral”. It was clearly living in the rugosan skeleton and not pushed into it by later burial. Note, though, the ragged boundary between the two corals. The rugose coral has the worst of it with some corallites deeply eroded. What seems to have happened is that the rugose coral had an irregular opening in its corallum (colonial skeleton) after death and the tabulate grew within the space, eventually filling it. The tabulate likely stuck out far above the rugose perimeter, but the polishing shaved them down to the same level. This is thus not a symbiotic relationship but one that happened after the death of the rugose coral.
Stumm, Erwin C   copyThe rugose coral species, Hexagonaria percarinata, was named in 1939 by Laurence Sloss, a famous sedimentary geologist with an early start in paleontology, but it is best known through the research of Erwin Charles Stumm (1908-1969; pictured above). Stumm was at the end of his life a Professor of Geology and Mineralogy and the Curator of Paleozoic Invertebrates in the Museum of Paleontology at the University of Michigan. Stumm grew up in California and then moved east for his college (George Washington University, ’32) and graduate (PhD from Princeton in 1936) education. He taught geology at Oberlin College up the road for ten years, and then moved to Michigan to start as an Associate Curator and Assistant Professor. I knew his name because in 1967 he was President of the Paleontological Society. He is said to have been a dedicated teacher of undergraduates and effective graduate advisor. It is fitting that his name is connected to such a popular fossil as Hexagonaria percarinata.


Sloss, L. 1939. Devonian rugose corals from the Traverse Beds of Michigan. Journal of Paleontology 13: 52-73.

Stumm, E.C. 1967. Growth stages in the Middle Devonian rugose coral species Hexagonaria anna (Whitfield) from the Traverse Group of Michigan. Contributions from the Museum of Paleontology, The University of Michigan 21(5): 105-108.

Stumm, E.C. 1970. Corals of the Traverse Group of Michigan Part 13, Hexagonaria. Contributions from the Museum of Paleontology, The University of Michigan 23(5): 81-91.

Citizen scientist to the rescue (in more ways than one)

November 9th, 2013

StephLizzie110913NEW LONDON, OHIO–The Wooster paleontologists spent a pleasant afternoon with our favorite amateur fossil collector Brian Bade. Brian has been mentioned in this blog previously for the many important fossils he has found and donated. He is a spectacular citizen scientist with a deep love (some would say obsession) with fossils of all kinds. He has a tremendous collection of fossils from the region and elsewhere carefully cataloged as to formations and localities. He knows what specimens may have scientific importance, and he has always been most generous with his time and fossils.

Today Steph Bosch (’14), Lizzie Reinthal (’14) and I visited Brian to examine specimens he recently collected from the Waldron Shale (Silurian) exposed in the St. Paul Stone Quarry in St. Paul, Indiana. My colleagues and I need to examine Silurian microconchids from North America and, sure enough, Brian came to the rescue with his collections and eagle eyes. Not only did he have his cleaned and sorted Waldron material laid out for us, he also had segregated specimens that had encrusting microconchids on them. The fossils were fantastic. Check out this webpage to get an idea of the paleontological diversity at this site.

Brian also brought out other trays and boxes of fossils from the Silurian and Early Devonian that had encrusters. Lizzie and Steph proved adept at picking out the tiny microconchids with their bare, young eyes as I struggled with my usual handlens. (This was the typical situation during our fieldwork in Israel this summer as well.) We accumulated several excellent specimens for later study under a Scanning Electron Microscope. Brian once again came through with critical fossils collected with all the right information for scientific analysis.

And the other rescue by Brian? You can see the situation in the image below. After all the driving I did in exotic places this summer, I managed to burrow into deep mud in Brian’s front yard. My little car was completely mired. (Note the smirking students in the background getting ready to tweet photos.) Brian has a tractor, fortunately enough, and a long chain. I left behind two deep trenches in his grass, and a little bit of my pride.

Wooster’s Fossils of the Week: Very common orthocerid nautiloids from the Siluro-Devonian of Morocco

November 3rd, 2013

Nautiloids585_092313If you’ve been to a rock shop, or even googled “fossil”, you’ve seen these beautiful and ubiquitous objects. They are polished sections through a nautiloid known as “Orthoceras“. We put quotes around the genus name because with these views it is nearly impossible to identify the actual genus, so “Orthoceras” becomes the go-to term for unknown orthoconic (straight) nautiloids. We also do not know exactly where in Morocco these fossils come from, but chances are they were dug out of the Orthoceras Limestone (Siluro-Devonian) exposed near Erfoud in the Ziz Valley near the edge of the Sahara Desert. They are easily excavated, take a nice polish, and look good from almost any angle of cut. People bring these to me often to ask about their origin, so let’s do a Fossil of the Week about the critters.

These fossil nautiloids consisted in life of a long, straight conical shell with internal chambers pierced by a long tube. The shells were originally made of aragonite, but almost all have been replaced and recrystallized with calcite. A squid-like animal produced the shell. Most of its body was in the large body chamber at the open end of the cone. They were effective nektic (swimming) predators during the Paleozoic Era around the world. In some places (like Morocco) nautiloids were so common that their dead shells carpeted shallow seafloors. Nautilus is a living descendant.
SingleNautiloid092313 annotatedIn this closer cross-sectional view of a Moroccan “Orthoceras“, we can identify the critical parts. A = a chamber (or camera); B = the siphuncle (tube running through the center of the shell); C = a septum that divides one chamber from another; D = an orthochoanitic (straight) septal neck of shell that runs briefly along the siphuncle. The white to gray material is crystalline (“sparry”) calcite that filled the empty shell after death and burial.

By the way, you can buy “Orthoceras healing stones“. A quote from that site: “Fossils are believed to increase life span, reduce toxins, anxiety, stress, balance the emotions, make one more confident. Containing supernatural and physical healing powers. They promote a sense of pride and success in business. Healers use fossils to enhance telepathy and stimulate the mind. Traditionally, fossils have been used to aid in  reducing tiredness, fatigue, digestive disorders, and rheumatism.” No wonder paleontologists are always the very image of health and wealth!
BRUGIEREThe genus Orthoceras was named in 1789 by the French zoologist (and physician) Jean Guillaume Bruguière (1749–1798). The only image I could find of him is the small one above. Bruguière earned a medical degree from the University of Montpellier in 1770, but like many aspiring naturalists, he never practiced. He traveled very widely for an 18th Century scientist, usually to pursue living and fossil mollusks on various expeditions. That he was a Republican in revolutionary France probably saved his head, but he lost his income in the turmoil. Most of his descriptions of fossil taxa appeared in print decades after he died on a voyage back from Persia. Of all his taxonomic contributions, the genus Orthoceras is the most widely known.


Histon, K. 2012. Paleoenvironmental and temporal significance of variably colored Paleozoic orthoconic nautiloid cephalopod accumulations. Palaeogeography, Palaeoclimatology, Palaeoecology 367–368: 193–208.

Kröger B. 2008. Nautiloids before and during the origin of ammonoids in a Siluro-Devonian section in the Tafilalt, Anti-Atlas, Morocco. Special Papers in Palaeontology 79, 110 pp.

Lubeseder, S. 2008. Palaeozoic low-oxygen, high-latitude carbonates: Silurian and Lower Devonian nautiloid and scyphocrinoid limestones of the Anti-Atlas (Morocco). Palaeogeography, Palaeoclimatology, Palaeoecology 264: 195-209.

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.


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.

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