Wooster’s Fossil of the Week: A conulariid revisited (Lower Carboniferous of Indiana)

July 31st, 2015

Conulariid03 585

This summer I’ve been updating some of the photos I placed in the Wikipedia system (check them out here, if you like; free to use for any purpose). I was especially anxious to replace a low-resolution image I had made of an impressive conulariid (Paraconularia newberryi) from the Lower Carboniferous of Indiana. The new version is above. Since I used the same specimen as a Fossil of the Week exactly four years ago to the day, I thought I’d take advantage of a slow summer and update that earlier text for this week:

I have some affection for these odd fossils, the conulariids. When I was a student in the Invertebrate Paleontology course taught Dr. Richard Osgood, Jr., I did my research paper on them. I had recently found a specimen in the nearby Lodi City Park that was so different from anything I had seen that I wanted to know much more. I championed the then controversial idea that they were extinct scyphozoans (a type of cnidarian including most of what we call today the jellyfish). That is now the most popular placement for these creatures today, although I arrived at the same place mostly by luck and naïveté.

The specimen above is Paraconularia newberryi (Winchell) found somewhere in Indiana and added to the Wooster fossil collections before 1974. A close view (below) shows the characteristic ridges with a central seam on each side.

Conulariid01 585Conulariids range from the Ediacaran (about 550 million years ago) to the Late Triassic (about 200 million years ago). They survived three major extinctions (end-Ordovician, Late Devonian, end-Permian), which is remarkable considering the company they kept in their shallow marine environments suffered greatly. Why they went extinct in the Triassic is a mystery.

ConulataThe primary oddity about conulariids is their four-fold symmetry. They had four flat sides that came together something like an inverted and extended pyramid. The wide end was opened like an aperture, although sometimes closed by four flaps. Preservation of some soft tissues shows that tentacles extended from this opening. Their exoskeleton was made of a leathery periderm with phosphatic strengthening rods rather than the typical calcite or aragonite. (Some even preserve a kind of pearl in their interiors.) Conulariids may have spent at least part of their life cycle attached to a substrate as shown below, and maybe also later as free-swimming jellyfish-like forms.

It is the four-fold symmetry and preservation of tentacles that most paleontologists see as supporting the case for a scyphozoan placement of the conulariids. Debates continue, though, with some seeing them as belonging to a separate phylum unrelated to any cnidarians. This is what’s fun about extinct and unusual animals — so much room for speculative conversations!


Driscoll, E.G. 1963. Paraconularia newberryi (Winchell) and other Lower Mississippian conulariids from Michigan, Ohio, Indiana, and Iowa. Contributions from the Museum of Palaeontology, The University of Michigan 18: 33-46.

Hughes, N.C., Gunderson, G.D. and Weedon, M.J. 2000. Late Cambrian conulariids from Wisconsin and Minnesota. Journal of Paleontology 74: 828-838.

Sendino, C., Zagorsek, K. and Taylor, P.D. 2012. Asymmetry in an Ordovician conulariid cnidarian. Lethaia, 45: 423-431.

Van Iten, H.T., Simoes, M.G., Marques, A.C. and Collins, A.G. 2006. Reassessment of the phylogenetic position of conulariids (?Vendian–Triassic) within the subphylum Medusozoa (Phylum Cnidaria). Journal of Systematic Palaeontology 4, 109–118.


Wooster’s Fossil of the Week: A calcareous sponge from the Lower Cretaceous of England

July 24th, 2015

Raphidonema faringdonense 070715a 585One of my favorite fossil localities is a gravel pit in Oxfordshire, England. Gravel pits are not usually good for fossil collecting given their coarse nature and high-energy deposition, but the Lower Cretaceous (Aptian) Faringdon Sponge Gravels are special. They are tidal gravels sitting unconformably over Jurassic rocks that have an extraordinary diversity and abundance of marine fossils, both from the Cretaceous and reworked from the Jurassic below. I have previously described in this blog bored cobbles, bryozoans, ammonites and a plesiosaur vertebra from this unit. Above is one of the most characteristic fossils from Faringdon, the calcareous sponge Raphidonema faringdonense (Sharpe, 1854).
Raphidonema faringdonense 070715b 585This is a view of the upper surface of this sponge. Like most sponges it was a filter-feeder sitting stationary on the seafloor. This one was probably attached to a cobble in the gravel. It is in the Class Calcarea because it has a fused network of calcitic spicules making up its skeleton. This is why it has remained a very resistant, rigid object long after death. It probably spent some time rolling around in those gravels with the tidal currents.
Sophie Faringdon 2007The Faringdon Sponge Gravels are a member of the Faringdon Sand Formation. They are cross-bedded gravels that have been mined for construction purposes since Roman times. Above is Wooster Geologist Sophie Lehmann (as a student) when she and I visited one of the gravel pits in 2007. For the record, this sponge comes from the Red Gravel, 5.5-8.5 meters above the disconformity with Oxfordian limestones, in the Wicklesham gravel pit on the southeast edge of Faringdon, Oxfordshire (51.647112° N, 1.585094° W).

after Maull & Polyblank, photogravure, circa 1856

Daniel Sharpe FRS (1806-1856) named Raphidonema faringdonense in 1854. He was born in Marylebone, Middlesex, England. His mother died shortly after his birth and he was raised by his uncle Samuel Rogers, a literary figure of some merit. He entered the mercantile business as an apprentice when he was 16, and he stayed connected with trading the rest of his life. His first research as a geologist (and this was very early in the discipline of geology) was examining geological structures around Lisbon, Portugal. He then studied the strata of north Wales and the Lake District of England. Sharpe was an early opponent of Adam Sedgwick in a dispute over the Cambrian, which brought him some notoriety among English geologists. His most prominent geological work was sorting out what rock cleavage meant in regard to stress and strain, using distorted fossils as part of his evidence. He died as the result of a riding accident in 1856, shortly after he had been elected president of the Geological Society of London.

Sorting out the taxonomic history of Raphidonema faringdonense is more complex than I would have expected for such a simple fossil. I’m using the most common version of the name, but we also see “farringdonense“, “faringdonensis” and farringdonensis“. (I know. Who worries about such things?)
Manon farringdonense Sharpe figuresManon farringdonense description 1854Above are Sharpe’s original figures of Raphidonema faringdonense, along with his description (and the nice bryozoan Reptoclausa hagenowi below). We can see that he spelled the species name with a double r in keeping with a common spelling of the village’s name then. I don’t know when we lost one of those letters.

Just to add to the complexity, Raphidonema is also the genus name of a filamentous green alga. Since it is not an animal, though, there is no legal problem with having the name also refer to a sponge. (There should be a rule against such homonymy, but there’s not.)


Austen, R.A.C. 1850. On the age and position of the fossiliferous sands and gravels of Faringdon. Quarterly Journal of the Geological Society of London 6: 454-478.

Lhwyd, E. 1699. Lithophylacii Britannici Ichnographia. 139 pp. London.

Pitt, L.J. and Taylor, P.D. 1990. Cretaceous Bryozoa from the Faringdon Sponge Gravel (Aptian) of Oxfordshire. Bulletin of the British Museum, Natural History. Geology 46: 61-152.

Sharpe, D. 1854. On the age of the fossiliferous sands and gravels of Farringdon and its neighbourhood. Quarterly Journal of the Geological Society of London 10: 176-198.

Wilson, M. A. (1986). Coelobites and spatial refuges in a Lower Cretaceous cobble-dwelling hardground fauna. Palaeontology, 29(4), 691-703.

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.

Wooster’s Fossil of the Week: A small lobster from the Lower Cretaceous of North Yorkshire, England

July 10th, 2015

Meyeria ornata fullMae Kemsley (’16) found this little beauty during her Independent Study fieldwork last month on the Speeton Cliffs of North Yorkshire. It is Meyeria ornata (Phillips, 1829), a decapod of the lobster variety, from the Speeton Clay. It is relatively common in Bed C4, so much so that it is referred to as “the shrimp bed”. Mae is the only one of our team of four who found one, though, so it is special to us. The above is a lateral view, with the head to the left and abdomen on the top of this small concretion.
Dorsal Meyeria ornataHere is a dorsal view looking down on the abdominal segments.
Screen Shot 2015-07-01 at 9.14.03 PMSimpson and Middleton (1985, fig. 1b) have this excellent diagram of Meyeria ornata in life position. The scale bar is one centimeter. “Details of pleopods, third maxillipeds and first antennae of M. ornata unknown. Dashed line represents length of extended abdomen. Symbols: a branchiocardiac groove; c postcervical groove; e cervical groove; m3 third maxilliped; p pereiopod; pi pleopod; t telson; u uropods; x ‘x’ area; r rostrum; al first antennae; a2 second antennae; ar antennal ridge; sr suborbital ridge; 1,2,3. branchial ridges.”

According to Simpson and Middleton (1985), Meyeria ornata actively crawled about on the muddy substrate like modern lobsters. They did not have true chelae (large claws), so they were likely scavengers in the top layers of the sediment rather than predators.

3 Mae working 060915Mae at work.


Charbonnier, S., Audo, D., Barriel, V., Garassino, A., Schweigert, G. and Simpson, M. 2015. Phylogeny of fossil and extant glypheid and litogastrid lobsters (Crustacea, Decapoda) as revealed by morphological characters. Cladistics 31: 231-249.

M’Coy F. 1849. On the classification of some British fossil Crustacea with notices of new forms in the University Collection at Cambridge. Annals and Magazine of Natural History, series 2, 4, 161-179.

Phillips, J. 1829. Illustrations of the geology of Yorkshire, Part 1. The Yorkshire coast: John Murray, London, 184 p.

Simpson, M.I. and Middleton, R. 1985. Gross morphology and the mode of life of two species of lobster from the Lower Cretaceous of England: Meyeria ornata (Phillips) and Meyerella magna (M’Coy). Transactions of the Royal Society of Edinburgh: Earth Sciences 76: 203-215.

Wooster’s Fossils of the Week: An Upper Ordovician cave-dwelling bryozoan fauna and its exposed equivalents

July 3rd, 2015

1 Downwards 063015This week’s fossils were the subject of a presentation at the 2015 Larwood Symposium of the International Bryozoology Association in Thurso, Scotland, last month. Caroline Buttler, Head of Palaeontology at the National Museum Wales, Cardiff, brilliantly gave our talk describing cryptic-and-exposed trepostome bryozoans and their friends in an Upper Ordovician assemblage I found years ago in northern Kentucky. They were the subject of an earlier Fossil of the Week post, but Caroline did so much fine work with new thin sections and ideas that they deserve another shot at glory. We are now working on a paper about these bryozoans and their borings. Below you will find the abstract of the talk and a few key slides to tell the story.


Trepostome bryozoans have been found as part of an ancient cave fauna in rocks of the Upper Ordovician (Caradoc) Corryville Formation exposed near Washington, Mason County, Kentucky.

Bryozoans are recognized as growing from the ceiling of the cave and also from an exposed hardground surface above the cave. Multiple colonies are found overgrowing one another and the majority are identified as Stigmatella personata. Differences between those growing upwards and those growing down from the roof have been detected in the limited samples.

The colonies have been extensively bored, these borings are straight and cylindrical. They are identified as Trypanites and two types are recognised. A smaller variety is confined within one colony overgrowth and infilled with micrite. In thin section it is observed that the borings follow the lines of autozooecial walls and do not cut across. This creates a polygonal sided boring, suggesting that the colonies were not filled with calcite at the time of the boring. The second variety has a larger tube size and its infilling sediment has numerous dolomite rhombs and some larger fossil fragments including cryptostomes, shell and echinoderm pieces. These cut through several layers of overgrowing bryozoans. Some of the borings contain cylindrical tubes of calcite similar to the ‘ghosts’ of organic material described by Wyse Jackson & Key (2007).

Very localised changes in direction of colony growth due to an environmental effect are seen.

Bioclaustration in these samples provides evidence for fouling of the colony surface, indicating that the bryozoans overgrew unknown soft-bodied organisms.


Wyse Jackson, P. N., and M. M. Key, Jr. (2007). Borings in trepostome bryozoans from the Ordovician of Estonia: two ichnogenera produced by a single maker, a case of host morphology control. Lethaia. 40: 237-252.

2 Title 0630153 Location 0630154 Strat position 0630155 hdgd up 0630156 hdgd down 0630157 Growth up 0630158 Growth down 0630159 Stigmatella 06301510 Cartoon 06301511 Boring A 06301512 Boring B 06301513 Ghosts explanation14 Ghosts 06301515 Overgrowths 06301516 Further questions 063015

Wooster’s Fossils of the Week: An encrusted bivalve external mold from the Upper Ordovician of Indiana

June 26th, 2015

1 Anomalodonta gigantea Waynesville Franklin Co IN 585I love this kind of fossil, which explains why you’ve seen so many examples on this blog. We are looking at an encrusted external mold of the bivalve Anomalodonta gigantea found in the Waynesville Formation exposed in Franklin County, Indiana. I collected it many years ago as part of an ongoing study of this kind of preservation and encrustation.
2 Anomalodonta gigantea Waynesville Franklin Co IN 585 annotatedTo tell this story, I’ve lettered the primary interest areas on image above. First, an external mold is an impression of the exterior of an organism. In this case we have a triangular clam with radiating ribs in its shell. The exterior of the shell with its ribs was buried in sediment and the shell dissolved, leaving the basic impression above. It is a negative relief. Please now refer to the letters for the close-up images below.

3 Bryo Anomalodonta gigantea Waynesville Franklin Co INA. At the distal end of the bivalve mold is what looks at first to be the original shell. It is calcitic, though, and we know this bivalve had an aragonitic shell. A closer look shows that this is actually the attaching surface of an encrusting bryozoan that bioimmured the original bivalve shell, which has since dissolved away. This smooth surface is the bryozoan underside; we see the characteristic zooecia (tubes holding the individual zooids) only when this surface is weathered away.

4 Borings Anomalodonta gigantea Waynesville Franklin Co INB. These tubular objects are infillings of borings (maybe Trypanites)that were cut into the original aragonitic shell of the bivalve. The tunnels of the borings were filled with fine sediment, and then the shell dissolved away, leaving these casts of the borings.

5 Inarticulate scar Anomalodonta gigantea Waynesville Franklin Co INC and D. In the middle of the external mold is this curious circular feature (C) mostly surrounded by a bryozoan (D). There was at one time a circular encruster, likely an inarticulate brachiopod like Petrocrania, that sat directly on the external mold surface. The bryozoan colony grew around but not over it because it was alive and still opening and closing its valves for feeding. The bryozoan built a vertical sheet of skeleton around it as a kind of sanitary wall. You may be able to see the other three or four structures in the top image showing brachiopod encrusters that left the building. This is an example of fossils showing us a living relationship, even if one is not longer preserved.

This fossil and its sclerobionts (hard substrate dwellers) show us that soon after the bivalve died its aragonitic shell dissolved away, leaving as evidence the external mold in the sediment, the bioimmuring bryozoan, and the boring casts. Very soon thereafter bryozoans and brachiopods encrusted the available hard substrate. This is a typical example of early aragonite dissolution on the sea floor during a Calcite Sea interval.


Palmer, T.J. and Wilson, M.A. 2004. Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas. Lethaia 37: 417-427.

Taylor, P.D. 1990. Preservation of soft-bodied and other organisms by bioimmuration—a review. Palaeontology 33: 1-17.

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

Wilson, M.A., Palmer, T.J. and Taylor, P.D. 1994. Earliest preservation of soft-bodied fossils by epibiont bioimmuration: Upper Ordovician of Kentucky. Lethaia 27: 269-270.

Wooster’s Fossil of the Week: An undescribed cyclostome bryozoan from the Upper Ordovician of Oklahoma

June 19th, 2015

HT_1276 585Paul Taylor and I presented a talk this month at the Larwood Symposium of the International Bryozoology Association in Thurso, Scotland. (Yes, way in the tippy-top of Scotland. Very cool.) Paul found the above wiggly bryozoan encrusting the interior of an orthid brachiopod identified as Multicostella sulcata (thanks, Alycia Stigall!) in the Lower Echinoderm Zone of the Mountain Lake Member of the Bromide Formation (Upper Ordovician, Sandbian) near Fittstown, Oklahoma. This bryozoan is “new to science”, as we grandly say. Paul generously invited me to describe it with him in this presentation and in a future paper. We did a 1994 paper together on Corynotrypa, a similar cyclostome bryozoan. The following are a few slides from our Larwood talk.






Slide21_052815This last image showing what appear to be an interior wall with a pore is critical. Corynotrypa does not have such walls, so our bryozoan is more like a sagenellid cyclostome.


Carlucci, J.R., Westrop, S.R., Brett, C.E. and Burkhalter, R. 2014. Facies architecture and sequence stratigraphy of the Ordovician Bromide Formation (Oklahoma): a new perspective on a mixed carbonate-siliciclastic ramp. Facies 60: 987-1012.

Taylor, P.D. and Wilson, M.A. 1994. Corynotrypa from the Ordovician of North America: colony growth in a primitive stenolaemate bryozoan. Journal of Paleontology 68: 241-257.

Wooster’s Fossils of the Week: Chaetetids from the Upper Carboniferous of Liaoning Province, North China

June 12th, 2015

1 Benxi chaetetid 2a 585Last year I had a short and painful trip to China to meet my new colleague and friend Yongli Zhang (Department of Geology, Northeastern University, Shenyang). The China part was great; the pain was from an unfortunately-timed kidney stone I brought with me. Nevertheless, I got to meet my new colleagues and we continued on a project involving hard substrates in the Upper Carboniferous of north China. Above is one of our most important fossils, a chaetetid demosponge from the Benxi Formation (Moscovian) exposed in the Benxi area of eastern Liaoning Province. We are looking at a polished cross-section through a limestone showing the tubular, encrusting chaetetids.
2 Chaetetid Benxi Formation (Moscovian) Benxi Liaoning China 585This closer view shows two chaetetids. The bottom specimen grew first, was covered by calcareous sediment, and then the system was cemented on the seafloor. After a bit of erosion (marked by the gray surface cutting across the image two-thirds of the way up), another chaetetid grew across what was then a hardground that partially truncated the first chaetetid. This little scenario was repeated numerous times in this limestone, producing a kind of bindstone with the chaetetids as a common framework builder.
3 Chaetetid Benxi cross-section 585Here is the closest view of the chaetetids, showing the tubules running vertically, each with a series of small diaphragms as horizontal floors.

Last week’s fossil was a chaetetid, introducing the group. They are hyper-calcified demosponges, and the classification of the fossil forms is still not clear. Their value for paleoecological studies, though, is clear. This particular chaetetid from the Benxi Formation preferred a shallow, warm, carbonate environment, and it was part of a diverse community of corals, fusulinids, foraminiferans, brachiopods, crinoids, bryozoans, gastropods, and algae. Such hard substrate communities are not well known in the Carboniferous, and this is one of the best.


Gong, E.P, Zhang, Y.L., Guan, C.Q. and Chen, X.H. 2012. The Carboniferous reefs in China. Journal of Palaeogeography 1: 27-42.

West, R.R. 2011a. Part E, Revised, Volume 4, Chapter 2A: Introduction to the fossil hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 20: 1–79.

West, R.R. 2011b. Part E, Revised, Volume 4, Chapter 2C: Classification of the fossil and living hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 22: 1–24.

Zhang, Y.L., Gong, E.P., Wilson, M.A., Guan, C.Q., Sun, B.L. and Chang, H.L. 2009. Paleoecology of a Pennsylvanian encrusting colonial rugose coral in South Guizhou, China. Palaeogeography, Palaeoclimatology, Palaeoecology 280: 507-516.

Zhang, Y.L., Gong, E.P., Wilson, M.A., Guan, C.Q.. and Sun, B.L. 2010. A large coral reef in the Pennsylvanian of Ziyun County, Guizhou (South China): The substrate and initial colonization environment of reef-building corals. Journal of Asian Earth Sciences 37: 335-349.

Wooster’s Fossil of the Week: A chaetetid demosponge from the Upper Carboniferous of southern Nevada

June 5th, 2015

1 Chaetetid Bird Spring Upper Carboniferous Nevada 585I collected this lump of a specimen during my dissertation research in the Bird Spring Formation (Carboniferous-Permian) of southern Nevada. It was found in a richly-fossiliferous Upper Carboniferous (Moscovian) portion near Mountain Springs Pass, which is about 40 km southwest of Las Vegas. It is a chaetetid, which at the time I interpreted conventionally as a singular extinct sponge in the genus “Chaetetes“. Since then we’ve learned a lot more about chaetetids. (And about the stratigraphy of the Bird Spring Formation. I wish we had sequence stratigraphy way back then!)
2 Chaetetid Bird Spring closer Upper Carboniferous Nevada 585Excellent and thorough work, especially by Ron West, has shown that the chaetetids are “hyper-calcified” members of the Class Demospongiae of the Phylum Porifera. They are sponges indeed, but the tubular chaetetid skeleton is found in at least three orders of the demosponges, including living ones. The chaetetid skeleton, which consists of very thin tubes (as shown above) is polyphyletic, meaning several groups of organisms converged on the same form.
3 Chaetetid Bird Spring closest 585In this oblique section of a chaetetid you can see the calcitic tubules, somewhat blurred by recrystallization.
4 Chaetetid Bird Spring cross-section Upper Carboniferous Nevada 585Here is a cross-section through one of the Bird Spring chaetetids. The tubules are very thin and long, somewhat resembling hair. Chaeto– comes from the Greek chaite for “hair or hairy”.

Now we know from systematic studies that the fossil “chaetetids” cannot be classified from their tubular skeletons alone. Without evidence of the spicules (which are rarely found, or at least recognized) and original mineralogy of the skeleton (many are recrystallized or, like the one at the top of this entry, replaced with silica) we can only refer to skeletal specimens such as ours as “chaetetid hyper-calcified demosponges”.

This is enough, though, for me to reintroduce them into my Invertebrate Paleontology classes. I had removed them from the teaching collections several years ago because of the confusion as to their status. Now they are at least demosponges, hyper-calcified at that.


Almazán, E., Buitrón, B., Gómez-Espinosa, C. and Daniel Vachard. 2007. Moscovian chaetetid (boundstone) mounds in Sonora, Mexico. In: Vennin, E., Aretz, M., Boulvain, F. and Munnecke, A., eds., Facies from Palaeozoic reefs and bioaccumulations. Mémoires du Muséum national d’Histoire naturelle 195: 269–271.

Martin, L.G., Montañez, I.P. and Bishop, J.W. 2012. A paleotropical carbonate-dominated archive of Carboniferous icehouse dynamics, Bird Spring Fm., southern Great Basin, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 329: 64-82.

West, R.R. 1994. Species in coralline demosponges: Chaetetida. In: Oekentorp-Küster, P., ed., Proceedings of the VI International Symposium on Fossil Cnidaria and Porifera, Munster Cnidarian Symposium, v. 2. Courier Forschungsinstitut Senckenberg 172: 399–409.

West, R.R. 2011a. Part E, Revised, Volume 4, Chapter 2A: Introduction to the fossil hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 20: 1–79.

West, R.R. 2011b. Part E, Revised, Volume 4, Chapter 2C: Classification of the fossil and living hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 22: 1–24.

West, R.R. 2012c. Part E, Revised, Volume 4, Chapter 2D: Evolution of the hypercalcified chaetetid-type Porifera (Demospongiae). Treatise Online 35: 1–26.

Wilson, M.A. 1985. Conodont biostratigraphy and paleoenvironments at the Mississippian-Pennsylvanian boundary (Carboniferous: Namurian) in the Spring Mountains of southern Nevada. Newsletters on Stratigraphy 14: 69-80.

Wooster’s Fossil of the Week: Petrified conifer wood

May 29th, 2015

1Petrified Wood 052615 585This is one of the most beautiful fossils in Wooster’s teaching collections. It is a polished section of petrified wood. It has vibrant colors and exquisite detail, as you’re about to see. Unfortunately any label that accompanied this specimen disappeared long ago. No matter how fantastic a fossil is, without its original location and stratigraphic context it has little scientific value. It works for our teaching collection, but I can’t tell you the age of the specimen, nor where it was found.
2Petrified wood close 052615 585Petrified wood is one of the most common types of fossil known to the public because of its abundance, attractiveness, hardiness (many a house out west has been built with petrified logs), and variety. Through the process of permineralization, minerals (quartz and chalcedony in this case) have infiltrated the porous organic structure, giving us three-dimensional, highly detailed preservation. This wood was first buried in low-oxygen sediments before it could decay on the forest floor. Groundwater circulated through the conductive tissue of the wood, depositing minerals in and around the cell walls of lignin and cellulose.

3Season of wood 052615 585It is hard to believe as we look closer and closer at the specimen that this is a fossil and not modern wood. Here we see the structure of the annual rings. The light-colored section is the new growth, the darker is when growth slowed at the end of the season. Our Wooster dendrochronologists, Greg Wiles and Nick Wiesenberg, could tell from this view that our tree was some kind of conifer.

4Polished petrified wood cells 585An even closer view of the same specimen. Now the perspective is dominated by vertical elements (rays) extending from the core of the tree outwards.

5Wood cells closest 052615 585This is as close as I could get with our photographic equipment. The cell walls and intervening rays are very distinct. Again, we’re looking at minerals here, not the original wood!

Again, fully label your fossils when you collect them. Because it has no locality information, this unlabeled specimen has little scientific worth. Too bad!


Hickey, L.J. 2010. The Forest Primeval: The Geologic History of Wood and Petrified Forests. Yale Peabody Museum Series, 62 pp.

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