Archive for February, 2011

Wooster’s Fossil of the Week: The ‘osses ‘ed clam (Upper Jurassic of southwestern England)

February 27th, 2011

Katherine Nicholson Marenco (’03) and I did delightful fieldwork on the Isle of Portland in Dorset, England, during the summer of 2002. We collected fossils from the famous Portland Limestone (Upper Jurassic) in a series of working quarries. Katherine completed her Independent Study thesis on the topic (“Paleoecology of a cryptic shell-encrusting community: observations from ‘upside-down’ encrusters in internal molds (Upper Jurassic of southern England)”) and the next fall gave her first GSA talk about her findings. Now Katherine is a paleontologist at Bryn Mawr College.

One of the common fossils in the Portland Limestone is the trigonid bivalve Laevitrigonia gibbosa (J. Sowerby, 1819) pictured above. It is usually preserved as an internal mold, meaning that the aragonitic shell dissolved away, leaving the sediment fill. The Dorset quarrymen thought these fossils resembled horses’ heads (in their dialect this comes out as “‘osses ‘eds”) and the name stuck among collectors. If you hold the internal mold upside down, there is a vague resemblance.

Trigonid bivalve in an outcrop of the Portland Limestone. It is "butterflied" meaning that the valves were still attached to each other by the ligament.

Our scientific fascination with this fossil went beyond its preservation and paleobiology (it was a mobile infaunal suspension feeder). After the clam died and the soft parts rotted away, a variety of organisms settled on the inside of its shell. These sclerobionts are preserved upside-down on the internal mold.

Close-ups of the outside of the L. gibbosa internal mold showing "upside-down encrusters": an encrusting oyster Liostrea expansa (o), a colony of the cyclostome bryozoan Hyporosopora portlandica (b), and a serpulid worm (s).

Katherine was able to sort out the identity of these encrusters (not an easy task from the bottom!), their succession and their growth and development. Entire communities lived in these half-closed shells lying on a shallow seafloor 150 million years ago. An ordinary ‘osses ‘ed yields extraordinary paleontological detail.

Postcard from Wooster, Ohio

February 22nd, 2011

On such a winter’s day.

Scovel Hall, The College of Wooster.

Front doors of Scovel Hall.

Kauke Hall at dawn.

Wooster’s Fossil of the Week: A honeycomb coral (Upper Ordovician of southern Indiana)

February 20th, 2011

Polygons are common in nature, whether in two dimensions as desiccation cracks or in three dimensions as with columnar basalt. They result from “closely-packed” disks or tubes. The honeycomb coral (Favosites Lamarck 1816) is one of the best fossil examples of hexagonal packing.

Favosites appeared in the Late Ordovician (about 460 million years ago) and went extinct in the Permian (roughly 273 million years ago). It consists of a series of calcitic tubes (corallites) packed together as closely as possible, thus the resemblance to a honeycomb. The corallites share common walls with each other. They were occupied by individuals known as polyps that were much like today’s modern coral polyps. They had tentacles that extended into the surrounding seawater to collect tiny prey such as larvae and micro-arthropods. (I’m confident here because we actually have fossils showing the soft polyps themselves.)

A, Portion of the corallum of Favosites favosa. B, Portion of four corallites of Favosites gothlandica, enlarged, showing the tabulae and mural pores. (From H.A. Nicholson (1877): "The Ancient Life History of the Earth A Comprehensive Outline of the Principles and Leading Facts of Palæontological Science.")

As you can see in the drawings above, the corallites are distinguished by internal horizontal partitions called tabulae and holes in the walls termed mural pores. These pores most likely allowed internal soft tissue connections between the polyps so that they could share digested nutrients.

Thin-section of Favosites from the Upper Ordovician of southern Indiana. Note the gaps in some corallite walls. These are mural pores.

Favosites as a genus has a very long history. It was named by the famous French natural historian and war hero Jean-Baptiste Lamarck. It is a favorite in paleontology courses because it is so easily recognized.

Wooster’s Fossil of the Week: A brittle star trace fossil from the Jurassic of Utah

February 13th, 2011

This week we have a trace fossil that looks almost exactly like the animal that made it. A trace fossil is evidence of organism activity recorded in the rock record. The photograph above shows one of my favorite specimens: Asteriacites lumbricalis von Schlotheim 1820 from the Middle Jurassic (Bathonian) Carmel Formation in southwestern Utah. I collected it while doing fieldwork with Wooster student Steve Smail too long ago for either of us to mention.

This fossil was made when a brittle star (ophiuroid) burrowed into carbonate sediment to either hide from predators or to look for a bit of food. Brittle stars are echinoderms that appeared in the Ordovician and are still very much alive today (see below). This Jurassic trace was formed when a brittle star essentially vibrated its way down into the loose sediment in a manner many of their descendants do today. The result is what appears to be an impression of the body (an external mold) but is actually formed by action of the animal.

Green Brittle Star (Ophiarachna incrassata) courtesy of Neil at en.wikipedia.

The trace fossil Asteriacites is far more common in the rock record than the brittle stars and seastars that made it. These traces thus often indicate the occurrence of organisms in critical intervals where they would otherwise be unknown. For example, Asteriacites lumbricalis is found in Lower Triassic rocks showing that brittle stars were part of the recovery fauna after the Permo-Triassic Mass Extinction (see, for a Wooster example, Wilson & Rigby, 2000).

Happy Birthday, Charles Darwin! An Occasion to Celebrate the Teaching of Evolution

February 12th, 2011

Portrait of Charles Darwin (with an editorial addition).

It is now a tradition among scientists to celebrate the birthday of the great English naturalist Charles Darwin.  He was born on February 12, 1809 — the very same day Abraham Lincoln entered the world.  (I have images of both men in my office as historical touchstones for the best of science and citizenship.)

Geologists like to remind the world that Darwin was one of their own.  He studied geology at Cambridge under the famous Adam Sedgwick and helped him map rock units in Wales one summer.  One of the primary influences on Darwin’s evolutionary ideas was the work of the uber-geologist Charles Lyell.  In fact, in an 1838 notebook, Darwin wrote:

“Pleasure of imagination. . . . I a geologist have illdefined notion of land covered with ocean, former animals, slow force cracking surface &c truly poetical.” [Maybe not so grammatical, but any geologist recognizes the sentiments!]

Charles Darwin, Geologist by Sandra Herbert is an excellent book on this topic (Cornell University Press, 2005, ISBN: 978-0-8014-4348-0).  I mention more of Darwin’s geological work and ideas in a recent podcast produced by The Wilderness Center. (The interview starts about 24 minutes into the program.)

The College of Wooster has a rich history of grappling with the tensions between its Presbyterian foundation and the new Darwinian evolution.  In the late 19th Century when evolution was mentioned in Wooster publications, it was always negative.  In The Post-Graduate and Wooster Quarterly of October 1890, for example, Professors Jonas O. Notestein and Elias Compton wrote in a review: “The whole essay is well calculated to wake up evolutionists to see either that there are more things in heaven and earth than are dreamed of in their philosophy, or else that it had been better if they had never been born.”  (I walk by a large portrait of stern Professor Compton every time I enter our second floor Scovel Hall lecture room … to teach evolution!)

In 1894, the astronomer Samuel Phelps Leland gave a talk at Wooster in which he said, “Your great, great, great, great, great grandfather was never a pollywog, and your great, great, great, great grandfather was never a ring tailed monkey.  No relative of yours was ever anything but a man; there is no connecting link between the mortal and the immortal.”  The Wooster Voice campus newspaper writers at the time thought it was a fine speech.  I find some pleasure in another famously wrong quote from Dr. Leland three years later: “… it will be possible to see cities on Mars, to detect navies in his harbors, and the smoke of great manufacturing cities and towns… Is Mars inhabited? There can be little doubt of it … conditions are all favorable for life, and life, too, of a high order. It is not improbable that there are beings there with a civilization as high, if not higher, than our own. Is it possible to know this of a certainty? Certainly.” (From World Making, p. 68-69; Woman’s Temperance Publishing Association, Chicago, 1898.)

Just a year after Samuel Phelps Leland dismissed Darwin at Wooster, a young biology professor named Horace N. Mateer began to teach a course on campus titled “Organic Descent”.  In his Wooster Catalogue description, Dr. Mateer wrote that “the doctrine of development by descent has come to be regarded as the basic factor in the study of organic life”.  With careful language and judicious politics, he broke through the resistance and taught evolution openly at Wooster for the first time.  He was very cautious indeed: he did not write the word “evolution” itself into any course description (it did not appear in a Wooster Catalogue until 1963!), and he repeatedly gave a popular talk on campus called “Evolution and Christianity” in which he essentially avoided Darwinian natural selection in favor of a kind of progressive creationism that correlated with biological and geological evidence.  Nevertheless, Professor Mateer laid the foundations for secular evolutionary science at Wooster.

(The story of evolution at Wooster is told in more detail in an article I wrote for the Fall 2002 issue of Wooster magazine.)

Meteorites Observed on the College of Wooster Campus!

February 8th, 2011

WOOSTER, OH – So the meteorites didn’t exactly fall from the sky today, but our GeoClub speaker let us see some samples from his own meteorite collection. Dr. Ed Young, UCLA Cosmochemist and Wooster Geology Alum (’81), gave a fascinating talk today on his research, which uses oxygen isotopes in meteorites to understand the origin and evolution of the solar system. He took us through the complicated taxonomy of meteorite classification and gave us a primer on oxygen isotopes before blowing our minds with supernova explosions, star formation, and uniqueness of our own solar system. I think the talk is best summarized by a quote from one of our current majors, “Now all I want to do is be a grad student and go to Antarctica and collect meteorites.”

Dr. Ed Young ('81, on the right) with his favorite TA and fellow Wooster alum, Dr. Mark Wilson (left).

Wooster’s Fossil of the Week: A chewed-up leaf (Upper Cretaceous of Kansas)

February 6th, 2011


This week’s fossil is a departure from our usual set of marine invertebrate animals. Above is a leaf of Viburnum lesquereuxii from the Dakota Formation of Ellsworth County, Kansas. The rocks enclosing it are from the Upper Cretaceous Cenomanian Stage, roughly 93-99 million years old. The leaf is preserved as a carbonized film in excellent detail.

What is cool about this particular leaf is that it has damage from insects that fed on the softer tissues between the veins. These feeding trace fossils are distinguished by smooth edges around the circular holes where the plant grew to seal off the torn cells. The leaf-eating insects may have been beetles or some kind of caterpillars. Viburnum is a common and diverse group of plants today, and they still experience significant insect herbivory, as shown below.

Beetles chewing holes in a modern Viburnum (http://www.maine.gov/agriculture/pesticides/gotpests/bugs/vib-leaf-beetle.htm).

Viburnum is a flowering plant, an angiosperm. This group appeared in the earliest Cretaceous (about 140 million years ago) and started a rapid rise to dominance just about the time this fossil leaf and its insect pests were alive. This little ecological vignette gives us an insight into the early days of our modern flora.

Theory to Practice on Ice

February 1st, 2011

A group from the Wooster community, the University of Cincinnati, The College of Wooster and St. Lawrence University assembled in Wooster for the weekend to mount an expedition to recover many meters of lake mud from the bottom of Round and Long Lakes in Ashland County, Ohio.



Dr. Lowell goes over the theory.

The practice consists of extracting meters of mud from the lake bottom.

Steph takes the vital notes on each meter (left). Lindsey (right) steps up to core another hole in the 6 inch-thick ice.

After a day coring Round Lake the team moved onto Long Lake and targeted the upper several meters of sediment to be analyzed by Jon Theisen for his senior IS in Archaeology. Jon hopes to shed some light on the environmental changes that occurred approximately 1500 years ago during the end of the Hopewell era in Ohio.

Because ice is a mineral …

February 1st, 2011

… we should record this morning’s ice storm in Wooster. You can read about the surprising properties of water ice as well on Wikipedia.

Ice on the holly tree near the back door of Scovel Hall in Wooster, Ohio.

The view from Scovel Hall across the College Mall to Severance Chemistry.

This makes me long for hot desert days.