Archive for October, 2016

Wooster’s Fossil of the Week: A naticid gastropod from the Pliocene of southern California

October 28th, 2016

polinices-galianor-sd-pliocene-1-copyThis week’s fossil comes from our teaching collection. It’s label appears to be from the late 19th Century. It is a naticid gastropod (“moon snail“) listed as Polinices galianor. That name, which I can only find in two lists and never with an author, may be a corruption of Polinices (Euspira) galianoi Dall 1909. It was collected from the Pliocene of San Diego County, California. It is preserved as both an internal mold and thin sheets of remnant original shell.

polinices-galianor-sd-pliocene-2-copyThis is a view of the underside along the axis of coiling. The hole is known as the umbilicus and is distinctive for the naticids. These snails are predatory, moving through loose sand with a very large foot and capturing shelled prey, like clams and other gastropods. They then drill a beveled hold through the shell of the prey with specialized teeth in their radulae. We’ve discussed the trace fossils they leave (Oichnus) in a previous post.

The genus Polinices was named in 1810 by Pierre Dénys de Montfort (1766–1820), a French malacologist (one who studies mollusks).

screen-shot-2016-10-22-at-11-52-46-amThe title page of de Monfort (1810).

screen-shot-2016-10-22-at-11-49-26-amThis brief paragraph is all it took in the early 19th Century to name a new taxon. The system is much more elaborate now.screen-shot-2016-10-22-at-8-20-44-pmPierre Dénys de Montfort is a tragic figure in science. First, he had the misfortune of being a French intellectual during the chaos of the French Revolution and the resulting Napoleonic dictatorship. Scientists struggled then, but after service in the revolutionary army and an apprenticeship with a geologist, de Monfort gained a position in the Jardin des Plantes, a research botanical garden in Paris. He did a massive study of mollusks, producing systematic tomes. De Monfort was a whiz at languages, so he did well as a translator after Napoleon was  finally defeated in 1815 and the Allied armies occupied Paris. Then he went off the rails. He had since 1801 championed the reports of mariners that giant cephalopods occasionally rose from the sea and attacked shipping, as shown in his above print (de Monfort, 1801, p. 256). The modern roots of the kraken! De Monfort took the idea too far, was ridiculed in the scientific community, and eventually died of starvation and alcoholism in the streets of Paris in 1820. The later discovery of giant squid salvaged his reputation a bit, but no one has yet found evidence of “le poulpe colossal”.

References:

Dall, W.H. 1909. Contributions to the Tertiary paleontology of the Pacific coast. U.S. Geological Survey Professional Paper 59. U.S. Government Printing Office, 288 pages.

de Montfort, P.D. 1801. Histoire naturelle, générale et particuliere des Mollusques, animaux sans vertèbres et á sang blanc. Volume 2. Paris, 424 pages.

de Montfort, P.D. 1810. Conchyliologie systématique, et classification méthodique de coquilles. Volume 2. Paris, 692 pages.

 

Wooster’s Pseudofossils of the Week: Artifacts in thin-sections of Ordovician limestones from southeastern Minnesota

October 21st, 2016

1bubfirstIt is always exciting to a geologist when thin-sections of curious rocks are completed and ready for view. A thin-section is a wafer of rock (30 microns thick) glues to a glass slide and examined by transmitted light through a petrographic microscope. They provide fantastic views of the mineralogy, paleontology, and structure of a rock in exquisite detail. Thin-sections are also full of mysteries since we have essentially two-dimensional slices through three-dimensional materials.

Thin-sections from the Decorah Formation samples collecting by Team Minnesota this past summer were finally available this week for study. I took the first look at slides of limestones containing ferruginous (iron-rich) ooids we gathered as part of Etienne Fang’s (’17) Independent Study. The first structures I saw were the crazy dark outlines above. What sort of fossils are these, I wondered. Could they be sponges? Odd bryozoans? Borings through the rock fabric? I was ready to post them here as mystery fossils to solicit your opinions. Now, though, they instead make a cautionary tale.

2bub730There are many of these features in a single slide from the Decorah Formation exposed at the Golden Hill outcrop near Rochester, Minnesota. Some are astonishingly complex. It then began to occur to me that these structures were too convoluted and unpredictable to actually be fossils. It also bothered me that to focus on them required to put the rest of the field out of focus. That only made sense if these oddities were in the epoxy, not the rock itself.

3buboverlapEtienne showed me how to demonstrate that these funny loops were not in the rock with this view: You can just make out the greenish lines overlapping the cut surface of this ferruginous ooid. Turns out I was excited about air bubbles in the cementing epoxy. They have nothing to do with the rock. I nearly posted my own pseudofossils.

4trio7321I held out hope, though, that these odd white objects in another thin-section of ooid-rich limestone. They appear to be ghostly outlines of ooids with a finely-textured object inside. They look like seeds with embryos within. Several are scattered through the thin-section. Another mystery fossil!

5duo7321A closer view. Strange how each internal object seems connected to an ooid on the outside, making them asymmetrical in their placements.

6single7321Strange also how once again the details of the internal object can only be seen with the rest of the slide out of focus. Yes, another artifact in the epoxy. This time we may be looking at holes left by ferruginous ooids plucked from the rock through the grinding process, pulling a patch of epoxy with them. Somehow this happened when the now-missing ooid was wedged against another. Nothing to see here, folks.

7ooid7301fAt least I can take the opportunity to show how cool Etienne’s ferruginous ooids are. Note that this one has a greenish layer midway through the cortex. It looks like the mineral chamosite to me. Spectacular detail in the lamellae, but only visible if the image is over-exposed.

8bifoliate7301hThere are plenty of real fossils in these thin-sections, of course. My favorites are these bifoliate bryozoans (lower right half) with their zooecia filled with ferruginous material. Note that the ooid above has had some of its lamellae dissolved away, probably because of some mineral diversity. Also note in the upper right another one of those crazy air bubbles.

The lesson I learn over and over: think, but then think again.

 

 

 

Wooster’s Fossil of the Week: Spiriferinid brachiopod from the Lower Carboniferous of Ohio

October 14th, 2016

syringothyris-texta-hall-1857-anterior-585Sometimes I choose a Fossil of the Week from our Invertebrate Paleontology teaching collection because students have responded to it in some way. This week’s fossil brachiopod has confused my students a bit because it is an internal mold (unusual for brachiopods in our experience) and a member of the Order Spiriferinida rather than the Order Spiriferida. (Catch that? The difference is in two letters.) It is Syringothyris texta (Hall 1857) from a local exposure of the Logan Formation (Lower Carboniferous). Above is a view of the anterior showing the medial fold and sulcus (like an anticline). This, by the way, is the largest brachiopod in our collection.

syringothyris-texta-hall-1857-posterior-585Syringothyris Winchell, 1863, is a genus within the order Spiriferinida, as noted before. This order was erected in 1994, pulling it from the more familiar Order Spiriferida. In this preservation, the spiriferinids are distinguished by a high cardinal area in the posterior (shown above). Not much higher than the spiriferids, truth be told.

syringothyris-texta-hall-1857-dorsal-585This is a view of the dorsal valve side of this internal mold. Note the absence of ribs (plicae) on the fold in the middle.

a_winchellThe geologist and paleontologist Alexander Winchell (1824-1891) named and described the genus Syringothyris. We met Winchell before in this blog as he described many common fossil taxa in the Midwest. He was born in upstate New York, a seventh-generation New Englander. In 1847 he was graduated from Wesleyan University in Connecticut. He had a varied and peripatetic career, spending most of his time as a teacher of science. He first taught in New Jersey, New York and Alabama, staying a short time in each place. He founded the Mesopotamia Female Seminary in Eutaw, Alabama, and became president (briefly) of Masonic University in Selma. In 1854, Winchell was appointed professor of physics and civil engineering at the University of Michigan, a position that soon became geology and paleontology. Five years later he became the state geologist of Michigan, a job characterized by an apparently difficult relationship with his superiors. In 1872 he left Michigan to be chancellor of Syracuse University, lasting only two years. Next he was a professor of geology and zoology at Vanderbilt University, a position he was forced to resign from in 1878 due to his unbiblical views of evolution. Winchell then returned to the University of Michigan, again as a professor of geology and paleontology. There is where he died.

Winchell’s views on evolution were complicated by his religiosity, and his religious life was made difficult by evolution. He developed a kind of transcendental Darwinism in which selection was reduced to inflexible laws from the Creator, a view we would today call Intelligent Design. He then confused it all by writing a popular book called Preadamites, published in 1880. The darker races, he said, lived in Europe and Asia before Adam. Adam and the subsequent “Noachites” were derived from Negroes, according to Winchell, advancing steadily in intellectual development and whiteness while the black race and other Preadamites were left behind. This work is profoundly racist and pseudoscientific, despite the Darwinian gloss he attempted to paint over it.

a-screen-shot-2016-10-10-at-8-49-42-pmb-screen-shot-2016-10-10-at-8-57-04-pmFrontispiece of Winchell (1880).

References:

Bork, K.B. and Malcuit, R.J. 1979. Paleoenvironments of the Cuyahoga and Logan Formations (Mississippian) of central Ohio. Geological Society of America Bulletin 90: 89–113.

Vörös, A., Kocsis, Á.T. and Pálfy, J. 2016. Demise of the last two spire-bearing brachiopod orders (Spiriferinida and Athyridida) at the Toarcian (Early Jurassic) extinction event. Palaeogeography, Palaeoclimatology, Palaeoecology 457: 233-241.

Winchell, A. 1863. Descriptions of FOSSILS from the Yellow Sandstones lying beneath the “Burlington Limestone,” at Burlington, Iowa. Academy of Natural Sciences of Philadelphia, Proceedings, Ser. 2, vol. 7: 2-25.

Winchell, A. 1880. Preadamites; or a demonstration of the existence of men before Adam. Chicago, S.C. Griggs and Company; 500 p.

Wooster’s Fossils of the Week: Upper Ordovician strophomenid brachiopods from Iowa

October 7th, 2016

leptaena-585Since we are covering brachiopods in my paleontology course this week, I’ve chosen a very recognizable genus from the Upper Ordovician of Iowa for our Fossil of the Week. This wrinkly strophomenid brachiopod is of the genus Leptaena Dalman, 1828. It is one of the most common brachiopods in the Lower Paleozoic, ranging from the Ordovician into the Carboniferous. The two specimens above are showing their dorsal valve exteriors.

leptaena-dorsal-585The same specimens are here turned over, showing the ventral valve exterior on the left and the dorsal valve interior on the right.

I always learn something when writing these brief fossil posts. These specimens are labeled in our collections as Leptaena rhomboidalis (Wahlenberg, 1818), the most common species name I’ve seen for this genus. Hoel (2005, p. 266), however, says: “In fact, L. rhomboidalis is known only from Gotland, [Sweden,] where it was confined to moderate energy reef environments during the early Wenlockian [Silurian].” So this species is only Silurian, and only found on a Swedish island. I’ll just leave it in open nomenclature, then, as Leptaena sp. The taxonomic details of the many species in the genus are beyond my skills and experience.
gwahlenbergThe erroneous species name, though, does introduce us to a fascinating Swedish naturalist named Göran Wahlenberg (1780-1851). This man is best known as a botanist, but he also had many geological and paleontological interests. He entered Uppsala University in 1792, earning a doctorate in medicine in 1806, and then joining the faculty to teach botany and medicine (with much more emphasis on the first). He occupied the university chair previously held by the demigod taxonomist Carl Linnaeus. He was elected at a young age to the Royal Swedish Academy in 1808. Wahlenberg’s primary work was with plant biogeography, especially in Sweden, but he made many scientific forays throughout Scandinavia and into Central Europe. He named Anomites rhomboidalis in 1818, which was later added to the genus Leptaena.

Wahlenberg studied glaciers in Scandinavia, making many observations about glacial striations and moraines we would recognize today. His main overarching theory of Earth history was that massive vulcanism in the “pre-Adamite” past caused great climate changes, eventually producing a global flood, the evidence for which included glacial erratics strewn throughout northern Europe. He was one of the first naturalists to posit connections between atmospheric composition and global temperatures.

What the scientific biographies of Göran Wahlenberg don’t often mention is that he is credited as the first person to bring the pseudoscience of homeopathy to Sweden. He studied the medicinal ideas of the founder of homeopathy, Samuel Hahnemann, and declared they had merit. He was an enthusiastic advocate, making him one of the “pioneers of homeopathy”. In his defense, at that time homeopathy was no doubt safer than mainline medicine!

References:

Hoel, O.A. 2005. Silurian Leptaeninae (Brachiopoda) from Gotland, Sweden. Paläontologische Zeitschrift 79: 263-284.

Kelly, F.B. 1967. Silurian leptaenids (Brachiopoda). Palaeontology 10: 590-602.

Wahlenberg, G., 1818. Geologisk avhandling om svenska jordens bildning. Uppsala.