Wooster’s Fossils of the Week: Silicified sclerobionts (Middle Permian of southwestern Texas)

October 21st, 2012

During my work at the National Museum of Natural History last week, I had my research desk amongst the many cabinets housing the famous Permian brachiopod collection made by the eminent paleontologist Richard E. Grant (1927–1995). Most of these specimens are from the Middle Permian of southwestern Texas, and they are preserved in a fantastic way. I peaked into some of these drawers and was just amazed at the beauty and delicacy of these fossils.

Many years ago I received a block of limestone from the Road Canyon Formation (Middle Permian, Roadian, about 270 million years old) found in the Glass Mountains of southwestern Texas. This rock was from an ancient reef system and so nearly completely filled with fossils. The fossils are replaced with very fine-grained quartz (“silicified”), yet the rock matrix around them is limestone (composed of calcium carbonate). The trick, then, is to dissolve away the limestone in hydrochloric acid and watch the delicate replaced fossils emerge. I did this with the Road Canyon Formation rock and recovered hundreds of extraordinary specimens. One set is shown above. Previous Fossils of the Week have included an aberrant brachiopod and a set of reef-forming brachiopods.
While at the Smithsonian, Kathy Hollis showed me a polished block of original Road Canyon Formation limestone (above) and then next to it the results after dissolving a similar block in acid (below). The complex mass of bryozoans, corals and brachiopods is preserved in exquisite detail.
Now, back to the Wooster specimens at the very top of this entry and just above. The platform is the wavy outer layer of a bivalve shell. Attached to it are encrusting organisms (sclerobionts). The long, gorgeous tube is a rugose coral. At its base is a ribbed athyrid brachiopod. Also in this vignette are bryozoans, additional corals and some really tiny productid brachiopods. Beautiful.

References:

Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas: American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Olszewski, T.D. and Erwin, D.H. 2009. Change and stability in Permian brachiopod communities from western Texas. Palaios 24: 27-40.

 

Wooster’s Fossil of the Week: A spiriferid brachiopod (Middle Devonian of northwestern Ohio)

October 14th, 2012

I begin my Invertebrate Paleontology course by giving each student a common fossil to identify “by any means necessary”. This year I gave everyone a gray little brachiopod, one of which is shown above. They did pretty well. Kevin Silver (’13) got it down to the genus quickly. Turns out a Google image search on “common fossil” is very effective!

This is Mucrospirifer mucronatus (Conrad, 1841), a beautiful spiriferid brachiopod from the Silica Shale Formation (Middle Devonian) of Paulding County, northwestern Ohio. I collected it and many others at a quarry on a crisp October day with my friend and amateur paleontological colleague Brian Bade.

The image at the head of this page is a view of the dorsal valve exterior of Mucrospirifer mucronatus; the image immediately above is the ventral valve exterior. Spiriferid brachiopods like this are characterized by extended “wings” and a long hingeline. Inside was their defining feature: a spiral brachidium that held a delicate tentacular feeding device known as the lophophore.

This is the anterior of our brachiopod. The fold in the middle helped keep incurrent and excurrent flows separate, enabling more efficient filter-feeding. (By the way, have you noted the quirky asymmetry of this specimen?)

A view of the quarry that yielded our Fossil of the Week. Note the happy amateurs picking through blast piles of the Silica Shale Formation (Middle Devonian).

A pond in the quarry. It has an unexpected beauty, muddy as it is.

Timothy Abbott Conrad (1803-1877) described Mucrospirifer mucronatus in 1841. We met him before when discussing a siliquariid gastropod. He was a paleontologist in New York and New Jersey, and a paleontological consultant to the Smithsonian Institution.

Reference:

Tillman, J.R. 1964. Variation in species of Mucrospirifer from Middle Devonian rocks of Michigan, Ontario, and Ohio. Journal of Paleontology 38: 952-964.

Wooster’s Fossils of the Week: Giant ostracods (Silurian of Estonia)

October 7th, 2012

During our Estonian expedition this summer, Richa Ekka (’13) chose as her Independent Study project focus the Soeginina Beds (lowermost Ludlow, Upper Silurian) of the Paadla Formation exposed in southeastern Saaremaa Island. These carbonate sediments, mostly dolomitized, were deposited in very shallow conditions — so shallow that in some places we have syneresis cracks and halite crystal molds. I expected the fossils to be mostly stromatolites and rare traces. We were pleasantly surprised to also find, though, a bed with numerous valves of the giant ostracod Herrmannina Kegel 1933 (shown above). I should have guessed that the hardy and extraordinarily successful ostracods would have been present.

At first we thought that these slightly-recrystallized shells must be bivalves (clams) because of their relatively large size (up to 25 mm long). But we didn’t see the typical bivalve muscle scars or hinging teeth and sockets. They had to be ostracods — but so big? The typical ostracod valve, shown below, is two mm or less in length. These Silurian examples are over 10 times that size. It would be like me meeting my 60-foot equivalent. Turns out that Herrmannina is known for its gigantism in the ostracod world — and it is not even the largest.

Cyamocytheridea sp. from the Eocene of Nederokkerzeel, Belgium. (Public Domain, Wikimedia.) This is the typical small size for an ostracod.
Today the ostracods, members of the Phylum Arthropoda, have over 8000 living species in both fresh and marine waters. Most crawl or burrow into sediments (that is, most are vagrant benthic epifaunal and infaunal), and a few are suspended in the water column (planktic). They have a wide range of feeding habits, from filter-feeding and deposit-feeding to herbivory and carnivory. (This is a key to their survival from the Early Paleozoic to today.) The living ostracod above shows that they are essentially a large head with several pairs of appendages inside two hinged valves. (The image is public domain from Anna33 at Wikipedia.) Their sex life is astonishing: ostracods have the largest sperm of any animals in both relative and absolute measures. Ostracod sperm are often ten times the length of the male body. (No, I don’t know how that works!)

Herrmannina is in the Order Leperditicopida of the Class Ostracoda. This genus was named in 1933 by Wilhelm Kegel (1890-1971), a geologist in the Preussische Geologische Landesanstalt of Berlin, Germany, who specialized in the Devonian and Carboniferous systems. I couldn’t find out much more about Dr. Kegel, but did stumble across an uncredited, undated low-resolution photo of him above. A fuzzy face from our paleontological past!

References:

Abushik, A. 2000. Silurian-earliest Devonian ostracode biostratigraphy of the Timan-Northern Ural Region. Proceedings of the Estonian Academy of Sciences, Geology 49: 112-125.

Belak, R. 1977. Ontogeny of the Devonian Leperditiid ostracode Herrmannina alta. Journal of Paleontology 51: 943-952.

Kegel, W. 1933. Zur Kenntnis palaozoischer Ostrakoden 3, Leperditiidae aus dem Mitteldevon des Rheinischen Schiefergebirges. Preussischen Geologischen Landesanstalt, Jahrbuch fur das Jahr 1932, Bd. 53, p. 907-935.

Kesling, R.V. 1958. A new and unusual species of the ostracod genus Herrmannina from the Middle Silurian Hendricks Dolomite of Michigan. Contributions, Museum of Paleontology, The University of Michigan 14, No. 9: 143-148.

Putzer, H. 1971. Wilhelm Kegel. Geologisches Jahrbuch 89: xiii-xxii.

Vannier,J., Wang, S.Q., and Coen, M. 2001. Leperditicopid arthropods (Ordovician – Late Devonian): Functional morphology and ecological range. Journal of Paleontology 75: 75-95.

Wooster’s Fossils of the Week: Beautiful molds on a concretion (Lower Carboniferous of Ohio)

September 30th, 2012

Kit Price (’13) was exploring a local creek on a Geomorphology course field trip north of Wooster led by Dr. Greg Wiles. Like the excellent paleontologist Kit is, her eyes continually searched the pebbles, cobbles, slabs and outcrops for that distinctive outline of something fossilian. This particular place has been in the blog before, so we know the stratigraphic and geological context of the rocks. Kit saw the curious golden brown, rounded rock above and immediately noted the presence of several fossils on its exterior. She collected it, cleaned it up, and the two of us examined the treasures.

Here is the key to what we found: A = trilobite pygidium external mold (more on this below); B = productid brachiopod dorsal valve internal mold; C = replaced bivalve shell fragment; D = productid brachiopod ventral valve external mold; E = nautiloid external mold. There are also external molds of twiggy bryozoans on the surface, but they are too small to distinguish in this view.

This rock is an ironstone concretion formed within the Meadville Member of the Cuyahoga Formation (Kinderhookian; Lower Carboniferous). It weathered out of the softer shale matrix and lay free on the creek bed. The original shells of the various fossils were dissolved away after burial, either being replaced with iron oxides (like the bivalve) or just remaining as open cavities (the molds). They represent a little survey of some of the animals that lived in this shallow, muddy seaway. Most of these fossils would have been lost to the dissolution, but the hard concretion preserved them.

The most interesting fossil here is the external mold of the trilobite pygidium (or tail piece). We don’t see these very often in Carboniferous and later rocks. The group is dwindling in advance of their final extinction at the end of the Permian period. I suspect this is the pygidium of Brachymetopus nodosus Wilson, 1979. I can only guess this, though, because only the cephalon (or head) of B. nodosus was described originally from the Meadville Member. This may be the long-missing pygidium of that species. It certainly has the little bumps that we would expect. (By the way, if you stare at the above image long enough, it appears in positive relief rather than the actual negative relief (or hole) that it is. It “pops out”, giving a view of what it may have looked like in life.)

Thanks, Kit, for such a nice view of a local Carboniferous community! It also brought back fond memories of my own local explorations as a Wooster student long, long ago.

References:

Corbett, R.G. and Manner, B.G. 1988. Geology and habitats of the Cuyahoga Valley National Recreation Area, Ohio. Ohio Journal of Science 88: 40-47.

Wilson, M.A. 1979. A new species of the trilobite Brachymetopus from the Cuyahoga Formation (Lower Mississippian) of northeastern Ohio. Journal of Paleontology 53: 221-223.

Wooster’s Fossil of the Week: a deformed brachiopod (Upper Ordovician of Indiana)

September 23rd, 2012

Kevin Silver (’13), a sharp-eyed paleontology student, found this odd brachiopod on our field trip earlier this month in southeastern Indiana. It comes from the Upper Ordovician (Katian) Whitewater Formation. Kevin correctly identified it as Vinlandostrophia acutilirata (Conrad, 1842), an orthid brachiopod formerly in the genus Platystrophia (see Zuykov and Harper, 2007). The above view is looking at the anterior of the brachiopod with the dorsal valve above and the ventral valve below.

What we see right away is that this brachiopod specimen is asymmetric: the right side is much shorter than the left. This is a feature of this individual, not the species. Is it a teratology — a deformity of growth? Probably. It is unlikely to be from post-depositional squeezing because the shell is otherwise in excellent shape. The oddity did not seem to hinder this individual from growing to a full adult size.

The same specimen looking at the dorsal valve with the hinge at the top of the image. The fold in the center is coming up towards us.

The posterior of our specimen, with the dorsal valve at the top. This is the hinge of the brachiopod.

A view of the ventral valve with the sulcus in the center.

(The above images are to help my paleontology students with their brachiopod morphology!)

References:

Alberstadt, L.P. 1979. The brachiopod genus Platystrophia. United States Geological Survey Professional Paper 1066-B: 1-20.

Boucot A.J. and Sun, Y.L. 1998. Teratology, possible pathologic conditions in fossil articulate brachiopods: p. 506-513, Collected works of the international symposium on Geological Sciences, Peking.

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 of Philadelphia 8: 228-280.

Zuykov, M.A. and Harper, D.A.T. 2007. Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera. Estonian Journal of Earth Sciences 56: 11-34.

Wooster’s Fossils of the Week: a little sclerobiont community (Upper Ordovician of Indiana)

September 16th, 2012

Last week the students of my Invertebrate Paleontology class found many excellent fossils in the Whitewater and Liberty Formations of southeastern Indiana. We will be featuring some of them in this space. I want to start with one of my own finds: an orthid brachiopod from the Whitewater known as Vinlandostrophia acutilirata (Conrad, 1842), the inside of which is encrusted by old friends Cuffeyella arachnoidea (Hall, 1847) and Cornulites flexuosus (Hall 1847).

A sclerobiont is an organism living in or on a hard substrate. The branching form in the image is Cuffeyella arachnoidea, an encrusting cyclostome bryozoan well represented in the Cincinnatian Group (Taylor and Wilson, 1996). The conical encrusters are the lophophorate Cornulites flexuosus, a species we covered earlier in detail.

These sclerobionts were well protected from weathering on the outcrop by the concavity of the brachiopod’s interior, giving us a beautiful vignette of an ancient ecosystem.

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 of Philadelphia 8: 228-280.

Hall, J. 1847. Paleontology of New York, v. 1: Albany, State of New York, 338 p.

Taylor, P.D. and Wilson, M.A. 1996. Cuffeyella, a new bryozoan genus from the Late Ordovician of North America, and its bearing on the origin of the post-Paleozoic cyclostomates, p. 351-360. In: Gordon, D.P., A.M. Smith and J.A. Grant-Mackie (eds.), Bryozoans in Space and Time. Proceedings of the 10th International Bryozoology Conference, Wellington, New Zealand, 1995. National Institute of Water & Atmospheric Research Ltd, Wellington, 442 pages.

Wooster’s Fossil of the Week: a twisted little crinoid (Lower Silurian of Estonia)

September 9th, 2012

This week’s fossil is a tiny little crinoid with an odd shape. Calceocrinus balticensis (shown above with the scale bar as one millimeter) is a new species from the Lower Silurian (Llandovery) of Hiiumaa, western Estonia. It is part of a series of new crinoid taxa described in the most recent issue of Acta Palaeontologica Polonica by Ausich et al. (2012). All that geological work in Estonia by Ohio State and Wooster geologists is resulting in several paleontological publications, all with the collaboration of our friend Olev Vinn at the University of Tartu, Estonia.

The western Estonian island of Hiiumaa where our little crinoid was found. (Image courtesy of Google Maps.)

Calceocrinus balticensis Ausich, Wilson and Vinn, 2012 (to give its full and glorious name) is unusual because its crown (the filter-feeding “head” of the crinoid) is recumbent on the column (the “stem”). In the images above you can see the column as a series of disks on their sides at the bottom of the view. The crown is the set of larger plates attached to the top of the column, from which there are several arms extending to the right. This new species is the first of its genus from the paleocontinent Baltica. It had sister species in North America on what became Anticosti Island in eastern Canada (see Ausich and Copper, 2010).

Calceocrinids (Order Calceocrinida Ausich, 1998) lived very close to the seafloor. The column of an individual, which in other crinoids holds the crown far off the substrate, lay horizontally along the bottom. The crown was hinged at its base so that it could be elevated perpendicular to the stem with the arms spread wide to filter organic material from the water. During non-feeding times the crown would lie inconspicuous on the bottom. This crinoid literally had a very low profile compared to its showy cousins.

Now, though, the shy little Calceocrinus balticensis gets a moment of exposure and formal admission to the roll call of life’s species.

References:

Ausich, W.I. 1998. Phylogeny of Arenig to Caradoc crinoids (Phylum Echinodermata) and suprageneric classification of the Crinoidea. The University of Kansas Paleontological Contributions, n.s. 9, 36 pp.

Ausich, W.I. and Copper, P. 2010. The Crinoidea of Anticosti Island, Québec  (Late Ordovician to Early Silurian). Palaeontographica Canadiana 29, 157 pp.

Ausich, W.I., Wilson, M.A. and Vinn, O. 2012. Crinoids from the Silurian of western Estonia. Acta Palaeontologica Polonica 57: 613-631.

Wooster’s Fossils of the Week: Sea urchin bits (Middle Jurassic of southern Israel)

September 2nd, 2012

Our fossils this week come from our growing collection of material found in the Matmor Formation (Callovian-Oxfordian) of Makhtesh Gadol, southern Israel. In November I will be giving a talk at the annual meeting of the Geological Society of America in Charlotte, North Carolina, on the taphonomy of Matmor regular echinoids (“sea urchins”). The abstract is online. Taphonomy is the study of the fossilization process. In this case it is essentially what happened to the echinoid remains after death and before final burial. This part of the fossilization history can tell us much about the environment of deposition of the Matmor Formation. The image above is one of the rare complete tests (skeletons) in our study. It is probably a rhabdocidarid echinoid, but the preservation is not quite good enough to tell.

Echinoids are especially interesting for this kind of work. (That link will send you to a wonderful site explaining all you’ll want to know about echinoids and their evolutionary history.) They originated way back in the Ordovician Period, about 450 million years ago, and have retained the same general skeletal structure since then. Their response to physical and chemical conditions on the ocean floor has thus been consistent over time, and we can experiment with modern representatives to estimate their decay and disarticulation processes.

Typical test plate fragments from a rhabdocidarid echinoid in the Matmor Formation. The specimen on the right is encrusted by a very thin plicatulid bivalve, which is in turn encrusted by small branching stomatoporid bryozoans.

A flattened and thorny rhabdocidarid spine. The left end has a socket that attached to a tubercle (bump) on the test of the echinoid.

This cool spine was apparently bitten by a Jurassic fish! Wish I had at least one of that fish’s teeth.

The strange swollen sphere with little holes at the base of this echinoid is a cyst that likely formed from a copepod parasitic infection. Neat (and so far undescribed in the literature).

We can conclude that the Matmor Formation was deposited in very shallow, warm marine waters, probably lagoonal (a favorite living place for rhabdocidarid echinoids), that were only occasionally disturbed by storms and “burial events”. The echinoids decayed and disarticulated on the seafloor (a process that takes about a week) and the pieces tossed around for awhile gathering sclerobionts (encrusters, in this case) and experiencing significant abrasion. This matches other evidence from our previous paleontological studies of the Matmor’s depositional environment.

References:

Donovan, S.K., and Gordon, C.M., 1993, Echinoid taphonomy and the fossil record: Supporting evidence from the Plio-Pleistocene of the Caribbean. Palaios, v. 8, p. 304-306.

Greenstein, B.J., 1991, An integrated study of echinoid taphonomy: Predictions for the fossil record of four echinoid families: Palaios, v. 6, p. 519-540.

Greenstein, B.J., 1992, Taphonomic bias and the evolutionary history of the Family Cidaridae (Echinodermata: Echinoidea): Paleobiology, v. 18, p. 50-79.

Greenstein, B.J., 1993, Is the fossil record of the regular echinoid really so poor? A comparison of Recent and subfossil assemblages: Palaios, v. 8, p. 587-601.

Kidwell, S.M. and Baumiller, T., 1990, Experimental disintegration of regular echinoids: Roles of temperature, oxygen and decay thresholds: Paleobiology, v. 16, p. 247-271.

Wooster’s Fossils of the Week: an enigmatic set of tubes (Middle Jurassic of Poland)

August 26th, 2012

The fossils this week celebrate the appearance of an article in the latest issue of Palaios authored by an international team led by my good friend and colleague Michał Zatoń (University of Silesia, Poland). The fossils are strange polka-dotted tubes encrusting Middle Jurassic oncoids and concretions from the Polish Jura — a place I enjoyed visiting last summer with Michał. The fossils were quite mysterious to us, but with the help of our new colleague Yasunori Kano (The University of Tokyo), we think we now have a good idea what they represent. Above you see one of the tubes on a concretion.
The polka dots are actually small, regular divots in the sides of the tubes, as shown above in this view through a scanning electron microscope. It turns out that these concavities are the same size as ooids (rounded carbonate grains) in the depositional environment. In fact, occasional ooids are still in their holes, as shown by the white arrow in the image.
In this cross-section through one of the tubes, each of the exterior holes is lined with a thin layer of carbonate, which is apparently the outer layer of an ooid that was cemented into each space. The tube itself is completely occupied by fine carbonate sediment.

Our hypothesis is that the tubes were formed by some sort of polychaete worm similar to serpulids and sabellids (with which they are associated). The worm may have built a hollow living tube by gluing ooids together and possibly taking advantage of the quick-cementing characteristics of this Jurassic calcite sea. It may have then fed on the surrounding microbial mats that covered the concretion and oncoid surfaces. This hypothesis explains the sessile nature of the tubes, their shape and construction, and their association with thin mineralized layers formed by cyanobacteria.

No polychaetes today are known to build living tubes out of ooids, so these Jurassic forms are thus far unique in the fossil and living record. It was a fun paleontological puzzle to tackle with my friends!

We are proud that our little study was chosen as the cover story for the August 2012 issue of Palaios:

“Unusual tubular fossils associated with microbial crusts from the Middle Jurassic of Poland. Upper left, an exposure of Middle Jurassic (Bathonian) clays at Ogrodzieniec in the Polish Jura; lower left, ESEM pictures of morphology and structure of the Middle Jurassic tubular fossils interpreted as remnants of agglutinated polychaete tubes; lower right, two pictures of tubular fossils encrusting oncoid and concretion; upper right, two pictures of recent agglutinated polychaete tubes from Japan.”

References:

Zatoń, M., Kano, Y., Wilson, M.A. and Filipiak, P. 2012. Unusual tubular fossils associated with microbial crusts from the Middle Jurassic of Poland: agglutinated polychaete worm tubes? Palaios 27: 550-559.

Zatoń, M., Kremer, B., Marynowski, L., Wilson, M.A. and Krawczynski, W. 2012. Middle Jurassic (Bathonian) encrusted oncoids from the Polish Jura, southern Poland. Facies 58: 57–77.

Wooster’s Fossil of the Week: a cameloid footprint (Miocene of California)

August 19th, 2012

This fossil is from near my hometown of Barstow, California. It was collected many years ago loose in talus from the Barstow Formation (Barstovian, Miocene). I note this carefully because today collecting such specimens from the Fossil Beds of the Rainbow Basin Natural Area is illegal, as it should be. This is one of the most fossiliferous Miocene deposits in the world, and it has been heavily vandalized over the years.
The Barstow Formation (in a wonderful syncline) at Rainbow Basin, Mojave Desert, California.

This two-toed footprint is Lamaichnum alfi Sarjeant and Reynolds, 1999. It is preserved as a convex hyporelief, which is essentially a filling of the actual footprint. It was made by a camel-like animal (there are many choices) that walked through stiff volcanic mud along a stream during the Miocene. The impression of this foot was quickly filled with later sediment, probably from an overbank flood.

When I was a kid we found dozens of these footprints in long trackways throughout the Barstow Formation at the Fossil Beds. Those fossils are all gone now, most lost to collectors with rock saws and sledge hammers. Fortunately many have been lovingly preserved in the Raymond M. Alf Museum in Claremont, California. You will note that the ichnospecies of our fossil was named for the charismatic Raymond Alf, a legend in the study of vertebrate trace fossils and a spectacular teacher.

Reference:

Sarjeant, W.A.S. and Reynolds, R.E. 1999. Camelid and horse footprints
from the Miocene of California and Nevada. San Bernardino Museum
Association Quarterly 46: 3-20.

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